The Khozmo Mkii Stepped attenuator

[The Black Adder]

Hello all.

There has been an upgrade pending for my Croft Epoch Elite pre amplifier for a while now. About a year ago it was fitted with an Alps Black Beauty pot by Glenn. As we all know Glenn likes his dual pots but with this pre amp it would have meant drilling more holes in the acrylic or surface mounting a control knob to which would've looked a little odd.

The Alps Black Beauty sounded superb and it's to no surprise to most that this pot is a superbly made bit of kit. Now unfortunately discontinued and replaced by another model. But the Black Beauty is still regarded as one of the best Alps pots made and even the dodgy black market have reproductions of them!

http://i457.photobucket.com/albums/qq295/musical_submarine/Tannoyista%20System/Khozomo%20Mkii%20Attenuator/DSC08788.jpg
Alps Black Beauty - Image ©2014 Tannoyista

So what was I wanting from an upgrade? Well firstly it came on a recommendation from Marco as he upgraded his BB to a DACT attenuator with distinct improvements in realism and air. So after deliberatiing whether I should also go with a DACT I was about to go for one but then AnthonyTD (Tube Distinctions) suggested a Khozomo attenuator. This sounded a much better option for me simply because of how many steps the DACT had being 24 steps. The BB also has 24 steps. But the Khozomo has 48 steps so works much better for me and with the kids in bed I could adjust the volume much better.

I'd seen them being talked about on the net quite affectionately. Although the early batches of the first MKI pots did have reliability issues they did seem to be isolated cases and Khozomo have now acted on those faults.

So after looking at them I found that a mkii version of this unit was now available albeit only through partsconnexion.com at the moment.

So I contacted Arek of Khozomo direct and asked about the new versions. The new version does look different from the previous version as it's red in colour, different style connections and a torque adjuster. Internally they are a fully new design too and come in shunt and series specs with Vishay, Takman or SMD resistors.

One thing I would like to add at this point is that the looks are superficial to me because it will always be hidden so this upgrade was a purely sonic adventure. But you have to admit, they do look superb...lol

http://i457.photobucket.com/albums/qq295/musical_submarine/Tannoyista%20System/Khozomo%20Mkii%20Attenuator/inside.jpg
Image property of Khozomo

The great thing about these is that you can change the loading resistors for example ZFoils, Caddock or whatever you fancy really. The model I went for was the ZFoils (47K) and the SMD version in shunt.

The order was placed and 3 working days later it arrived safely from Poland.

http://i457.photobucket.com/albums/qq295/musical_submarine/Tannoyista%20System/Khozomo%20Mkii%20Attenuator/DSC08780.jpg

http://i457.photobucket.com/albums/qq295/musical_submarine/Tannoyista%20System/Khozomo%20Mkii%20Attenuator/DSC08781.jpg

http://i457.photobucket.com/albums/qq295/musical_submarine/Tannoyista%20System/Khozomo%20Mkii%20Attenuator/DSC08784.jpg
Images ©2014 Tannoyista

The ZFoils are dead easy to install and wiring was a little tricky but that's because the wire I have in my pre is something like 0.5mm... maybe thinner.

http://i457.photobucket.com/albums/qq295/musical_submarine/Tannoyista%20System/Khozomo%20Mkii%20Attenuator/DSC08785.jpg

http://i457.photobucket.com/albums/qq295/musical_submarine/Tannoyista%20System/Khozomo%20Mkii%20Attenuator/ec823652-f9ae-4223-a4dc-c1101e170550.jpg
Images ©2014 Tannoyista

Fully installed and powering up I found that the sound had lost something... hmm.. What was it? - Well, it's quite apparent after the first few tracks.

What was missing was NOT a bad thing. When before the bass presence was even and maybe a little off beat/slow now the bass was more focused, faster and less lingering, rock solid too. It's like removing a muddiness to the sound. Transients are improved and more profound giving realism, air and presence to the music and it's recorded surroundings/environment. The music is also less strained and shouty and maybe less microphonic on certain frequencies too.

Tracking is spot on and much improved over the BB too. The action of the steps is also very nice, it feels slick and solid. I've not had chance to experiment with the torque adjuster but to be honest in it's default state it's perfect.

The Alps Black Beauty is a lovely pot let's get that in to perspective and it has many fans including myself but to quote others who I've spoke to "once you have heard what a decent attenuator can do it's there for life" I have to agree.

Up to now (4 hours and counting) I'm very happy with this unit and the service from Arek. He answered my picky questions well, lol. A first class service if I may say.

I'll report back with more findings once the ZFoils have dug in a little more as they will need to loosen up further.

http://www.khozmo.com/

Cheers
Joe

[User211]

I nearly bought one of his passives a while ago. They look pretty good - excellent, really, for the money. Great looking, too.

[Marco]

Nice one, Joe. Glad that the Khozmo has worked out well - thought it would! You can easily hear the 'phat' sound that's removed, which IME is intrinsic in all carbon-based pots, when upgrading to a quality stepped attenuator :)

Yup, I think that the Khozmo and the DACT are on a par, sound quality-wise, but the former has the advantage of more steps. At some point, I may try one, as when listening late at night I too could do with some more flexibility, in terms of volume adjustment. I'll then be able to compare both units and determine which one actually sounds best.

Your next move, since you're on that type of job at the moment, is to upgrade the source selector switch on your Croft. Do Khozmo design those, too? If not, I can thoroughly recommend the Seiden switches, available from HFC, which is what I used on my preamp. You won't get quite the same dramatic improvement as you obtained with your stepped attenuator, but the difference is still significant and very much worthwhile - doesn't cost too much either!

Anyway, looking forward to seeing you on Sunday and hearing your system for the first time in ages!! :cool:

Marco.

[The Black Adder]

Nice one, Joe. Glad that the Khozomo has worked out well - thought it would! You can easily hear the 'phat' sound that's removed, which IME is intrinsic in all carbon-based pots, when upgrading to a quality stepped attenuator :)

Yup, I think that the Khozomo and the DACT are on a par, sound quality-wise, but the former has the advantage of more steps. At some point, I may try one, as when listening late at night I too could do with some more flexibility, in terms of volume adjustment. I'll then be able to compare both units and determine which one actually sounds best.

Your next move, since you're on that type of job at the moment, is to upgrade the source selector switch on your Croft. Do Khozomo design those, too? If not, I can thoroughly recommend the Seiden switches, available from HFC, which is what I used on my preamp. You won't get quite the same dramatic improvement as you obtained with your stepped attenuator, but the difference is still significant and very much worthwhile - doesn't cost too much either!

Anyway, looking forward to seeing you on Sunday and hearing your system for the first time in ages!! :cool:

Marco.

Thanks guys.

Indeed, Marco.. the 'sound' of the carbon pot is now very apparent. With the Khozy it's such more free sounding. Very happy with it! :cool:

Yes.. I do need to update the selector. I'll take a look at seiden switches. It was going to be a question for this weekend actually, lol... I just need to know which type I need for it, as in spec because Ii only have two inputs.

Yup, sunday looks like a good-un. :)

Cheers

[anthonyTD]

Hi Joe,
Glad the recommendation seems to have worked out, as i explained in our recent conversations, i decided to try one of these attenuators about a year or so ago now' in a preamp i was building for someone else, and i was first blown away with the build, and quality of the components,i have since fitted one into my own Grounded Grid preamp. The sonic qualities differ slightly from the DACT i have been using for over ten years now in the Soul-Mate pre-amps and such, however, its not in a negative way, just different, and a lot will depend on the resistors used, and whether its a Shunt type, or series etc, over-all a very worth while upgrade, and of course, having double the positions over the DACT is a massive improvement in gain control.:)
Anthony,TD...

PS, as for a decent upgrade in selector switch, i would still recommend the DACT type, its an excellent switch, and [IMHO]a hard one to beat as far as reliability, and sonics are concerned.

[The Black Adder]

Ok... about 20 - 25 hours in and it's really opening up. The realism is now really starting to cook. I'm chuffed as big mad McChuff won the 'who's the most chuffed' competition one midsummer's eve.

:):cool::cool:

[pitadavespa]

Hi,

I've been interested in this attenuator for a while, but I've read a few complaints about its reliability.
Are you still happy with yours?


Thanks,
Luis

[The Black Adder]

Hi Luis.

Yes, it's superb!.. I'm very happy with it. The problems with the MK1 have now been addressed.

Arek is great to deal with too. :)

[pitadavespa]

Hi Joe,

Yes, I've contacted Arek and it seems a great guy.
I just hope all that mechanical problems are solved and the pre is as good as it looks.

Thanks ;)

[Stratmangler]

Are all those bare looking wires from the selector switch insulated by being lacquered?
It would bother me hugely if not :eek:

[The Black Adder]

Are all those bare looking wires from the selector switch insulated by being lacquered?
It would bother me hugely if not :eek:

They are lacquered... Regardless they are always checked so they are not too close to anything or any other of the wires. They are stiff too so they don't droop.

[Marco]

They are stiff too so they don't droop.

I guess you wouldn't have it any other way, big boy! :bum:

Marco.

[Paul4972]

Hi,
2 - 1/2 years later...... I'm thinking of following in your footsteps; I also have a Black Beauty (bb) installed in a Croft preamp. I understand I would gain more transparency, separation and space with a stepped attenuator (SA) instead of the bb. Is the Khozmo still holding up ? Does anyone have a sense of how differently the DACT or even TKD device would present music relative to the Khozmo ? Using a fast and open Decca cartridge on a good tonearm, silver bypasses on the phono stage's Duelund copper caps and fast single driver horns that give air and space aplenty, its hard to imagine just how much more transparency would come through with an SA. Perhaps I'd appreciate the difference on larger scale notionally more congested orchestral material. Concerned that the SA would thin out the sound too much, on the lean tending horns, though they're great now with the BB. Any thoughts much appreciated. Thank you.

[RothwellAudio]

I checked out the Khozmo website and that stepped attenuator certainly looks well-made and not terribly expensive. However, can someone explain exactly what a "shunt" attenuator is? I think I already know but I'd like it spelled out for me if possible.

[Firebottle]

Andrew, a shunt attenuator is one with a fixed series resistor followed by a variable resistance to ground, either by a variable pot, or in the case of a stepped attenuator a selected single resistor to ground.

:)

[AD Audio]

I use a Khozmo shunt in the prototype of my latest pre design. I've also tried TKD and Tocos pots shunted or otherwise. The Khozmo is the best sounding of all of these and very well made

[RothwellAudio]

The very idea of a "shunt" attenuator seems deeply flawed to me. It's a shame the Khozmo doesn't come as a more conventional design because it does look nicely made.

[Ali Tait]

It can sound very good though, and make a cheap pot sound much better too.

[Reffc]

The very idea of a "shunt" attenuator seems deeply flawed to me. It's a shame the Khozmo doesn't come as a more conventional design because it does look nicely made.

Quite. It's probably not an issue though if using low output impedance sources and has some cost benefits in such cases. The issue with shunt type stepped attenuators is that there's always going to be a conflict between keeping the input to output series resistance as high as possible to maintain a sensible load impedance, especially for higher output impedance sources, with the requirement to pass most if not all of the signal for higher volume settings. Ladder-types or series types would make more sense for valve sources.

You're right though, they do look well made and Arek Kallas, the chap that makes them, is a really nice guy too.

[Ali Tait]

Good article here-

http://www.world-designs.co.uk/forum/showthread.php?t=5795

[Reffc]

Having just contacted Arek, he does indeed produce a series-type stepped version which would by far the more universally usable. I'll be trying a few Khozmo series-type mono's in the RFC passive.

[anthonyTD]

He does, I have had a few, they are very well made.
Having just contacted Arek, he does indeed produce a series-type stepped version which would by far the more universally usable. I'll be trying a few Khozmo series-type mono's in the RFC passive.

[The Black Adder]

I now use the Series version in my Croft. It's a green body. I've not looked back to be honest.

Sounds superb.

[RothwellAudio]

At the risk of ruffling a few feathers, let me explain why I think shunt attenuators are a bad idea.

1) The input impedance is all over the place and the output impedance isn't as low as it could be. That may or may not be a problem, but it should be taken into account and included in the wider design decisions. Using a shunt attenuator as a drop-in replacement for a conventional pot may lead to problems.

2) The rationale for using the so-called shunt configuration is based on a flawed concept of the "the signal path", in my opinion. The flawed argument goes something like this: "an attenuator is formed by two resistors, but only the top resistor (aka the series resistor) is in the signal path, with the other resistor (aka the shunt resistor) being less important because it is only shunting the "waste" signal to ground."
This is totally wrong. Consider for example a 6dB attenuator. This could be formed by two identical resistors, and it usually is. However, it could also be formed by two identical capacitors, or two identical inductors. It could even be formed by a complex collection of resistors/capacitors/inductors in any series and/or parallel combination as long as the top half the attenuator is identical to the bottom half. Accepting the truth of this (and it's about as fundamental as it gets in electronics) should be enough to convince anyone that the so-called "shunt" resistor in an attenuator is just as important as the "series" resistor. The essential thing is that the two impedances (upper and lower) are identical.
I chose a 6dB attenuator because is makes the principal blindingly obvious (in my opinion), but of course the same holds true for any other level of attenuation.

So, if we accept that the shunt resistor is no less important than the series resistor the whole rationale behind the "shunt attenuator volume control" is shown to be flawed and the disadvantages outlined in statement 1) above have no counterbalancing advantages.
So, that's my argument. Feel free to point out any errors I may have overlooked.

[Reffc]

He does, I have had a few, they are very well made.

Good to know Anthony. I'll be ordering a few of them I suspect.

Agree with Rothwell's post above. Don't see any real advantages at all of shunt attenuator designs, just drawbacks. For me, having input impedance varying, and output impedance being higher than it needs to be are my main issues with the design.

[Arkless Electronics]

At the risk of ruffling a few feathers, let me explain why I think shunt attenuators are a bad idea.

1) The input impedance is all over the place and the output impedance isn't as low as it could be. That may or may not be a problem, but it should be taken into account and included in the wider design decisions. Using a shunt attenuator as a drop-in replacement for a conventional pot may lead to problems.

2) The rationale for using the so-called shunt configuration is based on a flawed concept of the "the signal path", in my opinion. The flawed argument goes something like this: "an attenuator is formed by two resistors, but only the top resistor (aka the series resistor) is in the signal path, with the other resistor (aka the shunt resistor) being less important because it is only shunting the "waste" signal to ground."
This is totally wrong. Consider for example a 6dB attenuator. This could be formed by two identical resistors, and it usually is. However, it could also be formed by two identical capacitors, or two identical inductors. It could even be formed by a complex collection of resistors/capacitors/inductors in any series and/or parallel combination as long as the top half the attenuator is identical to the bottom half. Accepting the truth of this (and it's about as fundamental as it gets in electronics) should be enough to convince anyone that the so-called "shunt" resistor in an attenuator is just as important as the "series" resistor. The essential thing is that the two impedances (upper and lower) are identical.
I chose a 6dB attenuator because is makes the principal blindingly obvious (in my opinion), but of course the same holds true for any other level of attenuation.

So, if we accept that the shunt resistor is no less important than the series resistor the whole rationale behind the "shunt attenuator volume control" is shown to be flawed and the disadvantages outlined in statement 1) above have no counterbalancing advantages.
So, that's my argument. Feel free to point out any errors I may have overlooked.

+1

These are the units I will be offering as an upgrade option (or indeed a unit can be ordered with one from new) in my forthcoming hybrid pre amp....

[anthonyTD]

I agree,
Ie; Shunt type Attenuators.
I tried them in a couple of preamps, but they just seem to sit on the dynamics, unless you played loud, the series version [IMHO] is great, especialy if your using them in the front end of a valve preamp.
Good to know Anthony. I'll be ordering a few of them I suspect.

Agree with Rothwell's post above. Don't see any real advantages at all of shunt attenuator designs, just drawbacks. For me, having input impedance varying, and output impedance being higher than it needs to be are my main issues with the design.

[Paul4972]

ok, so that's at least two of you vouching for Series rather than Shunt type from Kozmo for use in valve preamps including Croft units. I note, "shunt types sit on dynamics"; was that when used in a valve preamp or ss ? I'd like to order the SERIES type, but it cannot be built with Takman REX resistors, which, I am advised, would have given a warmer sound, and, according to the manufacturer would also give "more bass--though slightly less well controlled" than the resistors fitted as standard. I want to avoid losing bass impact through my single driver horn loudspeakers, which, as many on the forum will know, can suffer from bass lightness. So, if I fit a Khozmo Series type unit, which ended up removing too much bass, does anyone have a sense of how to dial bass back in to the equation by tuning the Khozmo ? I could of course return to using the Black Beauty pot and be happy! Everything else in the system has been optimised for bass response through the horns, including placing them in room corners ! Any thoughts greatly appreciated.

[Reffc]

ok, so that's at least two of you vouching for Series rather than Shunt type from Kozmo for use in valve preamps including Croft units. I note, "shunt types sit on dynamics"; was that when used in a valve preamp or ss ? I'd like to order the SERIES type, but it cannot be built with Takman REX resistors, which, I am advised, would have given a warmer sound, and, according to the manufacturer would also give "more bass--though slightly less well controlled" than the resistors fitted as standard. I want to avoid losing bass impact through my single driver horn loudspeakers, which, as many on the forum will know, can suffer from bass lightness. So, if I fit a Khozmo Series type unit, which ended up removing too much bass, does anyone have a sense of how to dial bass back in to the equation by tuning the Khozmo ? I could of course return to using the Black Beauty pot and be happy! Everything else in the system has been optimised for bass response through the horns, including placing them in room corners ! Any thoughts greatly appreciated.

That's a joke, right?

Just use the standard SMD resistors. If a resistor (or any other passive device) "removes bass" then there's something seriously wrong elsewhere or it's a faulty component. Its impossible for one resistor measuring "x" to affect FR of the bass any differently than another type/brand. That's not opinion, it's fact. As for resistors resulting in more or less bass control, that's also not possible. Bass control is everything to do with damping factor and nothing to do whatsoever with the brand of resistor being used. Just order the series SMD and it'll perform no differently to the posh one with more expensive resistors, except will result in a healthier bank balance.

[The Black Adder]

I first used a Black Beauty, then a TKD and then I tried the shunt, had two of the Khozy's a mk1 and a mk2. The difference between the carbon pots and the Khozy shunt was pretty dramatic. I then moved to the series SMD version and found that to sound slightly better in my system. I honestly have no problem with the series version. It's a lovely bit of engineering for the price.

With the shunt pots I used a few resistors, firstly the TAKMAN's then the ZFOIL's. I did on this occasion find a difference in sound with the latter winning. But I found the series version just as good if not better. Less harsh, nicely balanced sound.

I do think there is a difference in sound between a conventional resistor and the ZFOIL design but this is the bit of experience I've had with said resistors.

It's the same with conventional wirewound and the Duelund carbon pencil resistors in my crossovers. There is a difference there IMO but you pay for something that is small, very small and to some it would insignificant. So it's a 'choose ya poison' moment, if you feel flush then what the heck. :)

The only thing I can put these changes down to is the design as in both of these cases they are quite radical in design.

[Paul4972]

REFFC wrote:
That's a joke, right?

I doubt it's a joke. While what you write might be correct objectively, for the sake of clarity, the manufacturer did me the favour of giving his view of the effects on my very particular system --with sensitive / revealing single driver horn loudspeakers-- of the standard Shunt unit with SMD resistors and also one fitted with Takman REX resistors. On 7 November, Arek wrote with this guidance, "The Takman REX upgrade gives warmer sound. There are more bass but seems to be less controlled. Zfoil upgrade give more details and neutrality". That comment on the Takman REX resistor echoed others who know my system. Of course I am keen to avoid going backwards, as we all are, wanting to enhance sound while reducing the risk of a wrong turn, which in my case, could effect a deflating loss of bass heft and impact through horns. Thanks for your note.

[Paul4972]

Thank you Black Adder, it's helpful to read your notes. I have a Croft pre also, with horns that can be sensitive, negatively, to changes that more conventional speaker systems would simply shrug off. Thus my interest in other Croft pre and / or horn users' findings. Of course, systems behave differently, so I will only know by trying. Glenn wrote today that electrically,

I was interested to read ANTHONY TD's note above, "I agree, Ie; Shunt type Attenuators. I tried them in a couple of preamps, but they just seem to sit on the dynamics, unless you played loud, the series version [IMHO] is great, especialy if your using them in the front end of a valve preamp".

[anthonyTD]

Hi Paul,
Yes, I was relating to conventional Valve preamps, where the input resistance on the shunt type, and to a point, the type of resistor used, has a very marked affect on the sonic presence, and performance.
Hope this helps.
A...
Thank you Black Adder, it's helpful to read your notes. I have a Croft pre also, with horns that can be sensitive, negatively, to changes that more conventional speaker systems would simply shrug off. Thus my interest in other Croft pre and / or horn users' findings. Of course, systems behave differently, so I will only know by trying. Glenn wrote today that electrically,

I was interested to read ANTHONY TD's note above, "I agree, Ie; Shunt type Attenuators. I tried them in a couple of preamps, but they just seem to sit on the dynamics, unless you played loud, the series version [IMHO] is great, especialy if your using them in the front end of a valve preamp".

[RothwellAudio]

REFFC wrote:
That's a joke, right?

I doubt it's a joke...
...the manufacturer did me the favour of giving his view of the effects on my very particular system...
I'll back up Paul from Reffc. The idea that one brand of resistor has more bass than another is well into snake oil territory in my opinion.

[Arkless Electronics]

I'll back up Paul from Reffc. The idea that one brand of resistor has more bass than another is well into snake oil territory in my opinion.

+1 Beyond snake oil territory in fact.

[The Black Adder]

Snake Oil... I don't touch it. I'm tea total, proper builders tea too! :)

More bass? I agree a resistor isn't particularly tuned to a certain frequency, that does sound very far fetched. But an a difference in presentation/balance, small as it may be IME is possible.

[Paul4972]

I can do without snake oil, unless its good for hair loss or other health benefit. All I know is that horn loudspeakers can be quite a bit more sensitive than conventional loudspeaker systems to seemingly very minor moves. Thanks everyone for input.

[Edward]

I've had various custom audio stuff from Paul Baldwin.

Here is his lower price passive preamp.

http://www.reelaudio.co.uk/P3S.shtml

[pankon]

I am coming a bit too late in this interesting discussion about pots and passive attenuators. As an owner of a Croft Micro 25RSLS (line only), I wonder whether it would be worthwhile upgrading the Croft pots with Khozmo's passive attenuators (what type actually?) or try to completely substitute the Croft preamp with a Khozmo passive dual-mono preamp. https://khozmo.com/dual_mono_selector.html

Any clues from Croft owners and others?

Thanks in advance.

Panos

[Firebottle]

The cheapest upgrade you could do is to change the pots in the Croft for conductive plastic pots, such as these :

https://www.mouser.co.uk/ProductDetail/BI-Technologies-TT-Electronics/P160KN-0QC15A250K?qs=sGAEpiMZZMtC25l1F4XBU%252bXO0%2fntrr gI5Uf%2fbxv2Axs%3d

[pankon]

The cheapest upgrade you could do is to change the pots in the Croft for conductive plastic pots, such as these :

https://www.mouser.co.uk/ProductDetail/BI-Technologies-TT-Electronics/P160KN-0QC15A250K?qs=sGAEpiMZZMtC25l1F4XBU%252bXO0%2fntrr gI5Uf%2fbxv2Axs%3d

Alan, thanks for the advice. However, I am not looking for the cheapest upgrade, but for the one that will take the sound quality to the max. As mentioned, I am considering either high-end attenuators or perhaps even altogether substituting the active preamp with a passive design. Hmmm, there are real-life problems :lol:

[Bigman80]

Alan, thanks for the advice. However, I am not looking for the cheapest upgrade, but for the one that will take the sound quality to the max. As mentioned, I am considering either high-end attenuators or perhaps even altogether substituting the active preamp with a passive design. Hmmm, there are real-life problems [emoji38]The Khozmo is a beast. Simply, stunning.

You may have to rejig the guts to get one to fit. I did ask Glenn Croft how much it would cost to buy a 25r pre with my Khozmo fitted but never got a reply.

Sent from my VKY-L09 using Tapatalk

[pankon]

Oliver, the dilemma for me would be whether it would be worthwhile to completely turn to a passive preamp, such as the Khozmo dual-mono box, and not just fit the attenuators within the Croft pre.

[Firebottle]

To be honest I don't think you would notice much difference between having Khozmo attenuators or conductive plastic track pots in the Croft.

The conductive plastic tracks have a very organic sound, quite different from standard carbon track pots. This opinion is from received wisdom, but from some very well respected individuals in audio industry.

[pankon]

To be honest I don't think you would notice much difference between having Khozmo attenuators or conductive plastic track pots in the Croft.

The conductive plastic tracks have a very organic sound, quite different from standard carbon track pots. This opinion is from received wisdom, but from some very well respected individuals in audio industry.

Alan,

enclosed a photo of the pots in my Micro 25RSLS. Can you or any other forum member recognize them perhaps?

24014

[Bigman80]

There's a lot of perceived wisdom about pots etc and to be honest, there are some very notable designers that use standard pots like Alps blue and some that use plastic pots like the ones Alan pictured. There is one I know of who uses a cheap £1 version in their gear and reports are that it's excellent.

All I can say is in my own experience, I have been able to get a higher level of transparency from better pots/attenuators like that of the Khozmo compared to the Alps blue. Some will say I am imaging it but when I offered to make a cheap as chips pre v my DCB1, There wasn't any enthusiasm.

Truth is, it's a matter of taste. When I had a totally passive preamp, I never felt they offered the grip on the bass I liked. When I built he DCB1 which is effectively an active pre by way of the DCB1 Buffer board, I lost nothing of the fluidity and expanse of the passive but gained authority and slam. It suits me but may not suit you.

Sent from my VKY-L09 using Tapatalk

[pankon]

I searched on the Internet and found that the pots used in my Croft 25RSLS are RV24YN20S A104...

[Bigman80]

I searched on the Internet and found that the pots used in my Croft 25RSLS are RV24YN20S A104...Like I said, there are a fair few who swear off high end pots/attenuators. It's a "suck it and see" situation.

Sent from my VKY-L09 using Tapatalk

[pankon]

And by the way, what’s the verdict? Shunt or series attenuator for a passive preamp design?

Thanks

[Bigman80]

Mine is a 50k series.

My verdict is that it's exceptional.
And by the way, what’s the verdict? Shunt or series attenuator for a passive preamp design?

Thanks

Sent from my VKY-L09 using Tapatalk

[pankon]

I've asked Arek (Khozmo designer/builder) and he is very much fond of the shunt topology, claiming that it yields great (the best?) sonic results. Hmmm, what should I do?

[Bigman80]

I asked Arek and he is very much fond of the shunt topology, claiming that it yields great (the best?) sonic results. Hmmm, what should I do?I went for series as it presents a constant load.

That the the advice given from the guys here.

Sent from my VKY-L09 using Tapatalk

[Firebottle]

..... what should I do?

Panos, for the money try one of these before you do anything else, it's a giant killer :

https://www.ebay.co.uk/itm/Volume-Remote-Control-Relay-128-Steps-Exponential-Constant-input-impedance-4-CH/142811721459?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

[pankon]

Many thanks for the advice, Alan. It's just that I need a dual-mono passive preamp with two outputs. And as a matter of fact, earlier today I placed the order for a Khozmo preamp. My dilemma is shunt vs series resistors...
I will try to match and drive my Croft Series 7R monoblocks and Harbeth SHL5 Plus speakers.

[pankon]

Joe,

if I understand correctly, you just replaced your Alps Black Beauty pots with Khozmo's shunt attenuators? How easy was it? No other mods in your Croft preamp required?
I am also thinking of doing something similar to my Croft Micro 25 RSLS (Line-only) and replace the inexpensive TOCOS pots (https://www.ebay.com/itm/10pc-Cosmos-Tocos-Potentiometer-RV24YN-20S-15A104-24mm-A100K-A104-A100K-Japan-/140413148908) with something more substantial (Khozmo shunt attenuators with z-foil and Takman REY or REX?).

24369

I wonder if it's more complex than I think and not just a simple replacement of the pots... Thoughts, please?

[anthonyTD]

The Superior stereo balance accuracy a good stepped attenuator acheives is; in itself IMHO worth the upgrade, However, I do understand why some would recomend some other types of conventional pots, they all have a sonic impact, you choose your poison etc.
As for Shunt, or Series, I have tried both over the years, and always come back to the Series type. :)
The khozmo Attenuators are exceptional value, with a build quality that is hard to beat at any price!
Hope this helps.
A...

[Bigman80]

I'm sure Hificollective stopped stocking the TOCOS pots due to channel imbalances.

The Khozmo is a supreme attenuator, but you may have to reorganise the guts to fit it in. It's massive!

Sent from my VKY-L09 using Tapatalk

[pankon]

Yes, I am afraid the Khozmo attenuator will not fit in the Croft. I am wondering whether there is any other alternative attenuator (to replace the Tocos), that might significantly affect the sound (for the better -)).

[Bigman80]

Yes, I am afraid the Khozmo attenuator will not fit in the Croft. I am wondering whether there is any other alternative attenuator (to replace the Tocos), that might significantly affect the sound (for the better -)).I spoke with Glenn Croft about this when I was deciding on what preamp to go for. The Croft was a serious contender and I asked if he could fit a Khozmo. He said he could and would do so but never got back with a price so I went elsewhere. What I can say is, in my opinion, it's an absolutely wonderful attenuator and has far surpassed all of my expectations.

Sent from my VKY-L09 using Tapatalk

[anthonyTD]

DACT attenuators will fit in the Croft, I have used these in my own preamps over the years with excelent results.
Yes, I am afraid the Khozmo attenuator will not fit in the Croft. I am wondering whether there is any other alternative attenuator (to replace the Tocos), that might significantly affect the sound (for the better -)).

[Bigman80]

DACT attenuators will fit in the Croft, I have used these in my own preamps over the years with excelent results.DACT are well liked. Good shout!

Sent from my VKY-L09 using Tapatalk

[pankon]

Anthony,
as you know Croft preamps use dual-mono pots, so I guess that DACT would offer something similar. Is there is a specific model that you would recommend? Is it a drop-in replacements to the existing TOCOS pots? Any idea about the cost perhaps?
Thanks
Panos

[Bigman80]

Anthony,
as you know Croft preamps use dual-mono pots, so I guess that DACT would offer something similar. Is there is a specific model that you would recommend? Is it a drop-in replacements to the existing TOCOS pots? Any idea about the cost perhaps?
Thanks
Panos
You don't need dual pots, can fit a stereo pot and fill the hole of the now redundant hole with a blank.

Sent from my VKY-L09 using Tapatalk

[pankon]

To be honest, the dual pots actually play the role of a balance pots. So I would not like to eliminate them and substitute them with a single stereo pots -))

[Bigman80]

Fair enough.
To be honest, the dual pots actually play the role of a balance pots. So I would not like to eliminate them and substitute them with a single stereo pots -))

Sent from my VKY-L09 using Tapatalk

[STD305M]

Hi
I also use the Khizmo 50k series pot in my dcb1 turbo and would concur with Oliver.
The transparency and bass authority is by far the best I've heard.

Steve..

[Bigman80]

I'd drop Glenn a message and ask him if he could help you out.

[anthonyTD]

Hi Panos,
You used to be able to get the mono versions, I will check, and let you know which ones to go for.
A...
Anthony,
as you know Croft preamps use dual-mono pots, so I guess that DACT would offer something similar. Is there is a specific model that you would recommend? Is it a drop-in replacements to the existing TOCOS pots? Any idea about the cost perhaps?
Thanks
Panos

[anthonyTD]

Here you go!
http://dact.com/html/attenuators.html
Hope this helps.
A...

[Qwin]

I don't understand, why is no one recommending the Khozmo Ladder stepped attenuators?

Is it just cost, they are 40 t0 50% more expensive than the Shunt or Series, as you need 96 resistors per channel, not 48/49.

The problem with the Shunt has been explained, you have different impedance for every setting.

For me the problem with the Series type, is just that, you have 48 resistors in series with the output seeing the number of resistors dictated by the rotary control position and the remaining number going to ground, the sum of the two equaling 48. At low volume there will be many resistors in series for the signal path, is this not a bad thing?

Surely the Ladder type is the best, where you have pairs of resistors for each volume position, one for the signal and one (matched) to maintain impedance. There is only ever one resistor in the signal path and constant impedance is maintained across the controls range.

The only difference is that the Series uses multiples of resistors for each value, the Ladder uses a single resistor.

I would have thought the Ladder was the better choice?
You still get +/- 0.1dB channel matching if you want a stereo version.

So why not the Ladder? :scratch:

[Bigman80]

I don't understand, why is no one recommending the Khozmo Ladder stepped attenuators?

Is it just cost, they are 40 t0 50% more expensive than the Shunt or Series, as you need 96 resistors per channel, not 48/49.

The problem with the Shunt has been explained, you have different impedance for every setting.

For me the problem with the Series type, is just that, you have 48 resistors in series with the output seeing the number of resistors dictated by the rotary control position and the remaining number going to ground, the sum of the two equaling 48. At low volume there will be many resistors in series for the signal path, is this not a bad thing?

Surely the Ladder type is the best, where you have pairs of resistors for each volume position, one for the signal and one (matched) to maintain impedance. There is only ever one resistor in the signal path and constant impedance is maintained across the controls range.

The only difference is that the Series uses multiples of resistors for each value, the Ladder uses a single resistor.

I would have thought the Ladder was the better choice?
You still get +/- 0.1dB channel matching if you want a stereo version.

So why not the Ladder? :scratch:I went with the advice given to me by Rothwell and Firebottle and bought the Khozmo Series.

I couldn't tell you why the Ladder would or wouldn't be better but if it's better than the Series, it's worth every penny of that extra 40-50%

[Qwin]

I went with the advice given to me by Rothwell and Firebottle and bought the Khozmo Series.

I couldn't tell you why the Ladder would or wouldn't be better but if it's better than the Series, it's worth every penny of that extra 40-50%

The Shunt/Series use one brushing contact, the Ladder uses two, which is a contributing factor I suppose, but I wouldn't have thought this was as detrimental as a hole bunch of components strung together. The old adage, less is more comes to mind.

I know you are happy with the results Oli, we are probably talking very minor differences here anyway.

[Qwin]

There are 48 resistors in the circuit regardless of the volume setting. The idea that some are "in the signal path" and the rest are "just going to ground, so they don't matter" is totally and fundamentally wrong. All 48 resistors are doing the same job regardless of the volume control setting.

Is using 48 resistors inferior to using 2 resistors? In my opinion, no, it's superior. Resistors have a voltage coefficient http://www.resistor.com/tech_voltagecoefficient.htm If you use 48 resistors instead of 2 the voltage across each resistor is lower and therefore any distortion is lower too. Also, the power handing capacity of 48 resistors is much higher than 2 resistors so any heating effects will be much less with 48 resistors. Admittedly the power dissipation is microscopic so the benefits are probably insignificant, but it's better to have higher capacity than lower imho.
Also, with 48 resistors instead of 2, each resistor is a low value and any stray capacitance between switch contacts will have a much smaller shunting effect across a small resistor compared to a big one.
They are my reasons for advocating the use of "series" stepped attenuators rather than so-called "ladder" stepped attenuators. BTW, I think the term "switched pair" is preferable to "ladder" but nobody else seems to think so :lol:

Your point about individual, smaller value resistors, having lower distortion is right I think, but it is additive across the number used, so you end up with more distortion overall. This is marketed as the rational for using the Ladder type, which is just a load of individual voltage divider networks.
I just looked at who is making/selling what and there are not many Series Type made compared with Shunt or Ladder. There are some Ladder types selling at around a Grand or more, if simpler, cheaper to make alternatives gave better results, I don't think they would bother.
On the other hand Khozmo make all three types, but give no indication as to which is preferable.
Some of the Ladder type using surface mount devices, with their shorter signal paths are incredibly compact.
Ladder attenuators were all the rage a while back, had one retro fitted in my Croft Pre, still plenty available, just wondering why they had not been considered in this thread. :)

[sq225917]

I use the SMT ladder version of the Khozmo 10k with relay switching and optical encoder. It's a very nice pot. Not quite sure it's as clean as a similar value Goldpoint but it does have a remote control in the mix.

In a ladder arrangement isn't the total resistor noise the total resistance / the number of resistors, or thereabouts

[Qwin]

I use the SMT ladder version of the Khozmo 10k with relay switching and optical encoder. It's a very nice pot. Not quite sure it's as clean as a similar value Goldpoint but it does have a remote control in the mix.

In a ladder arrangement isn't the total resistor noise the total resistance / the number of resistors, or thereabouts

I think that would give you an average for the noise across the settings.
In a Ladder there is only ever one resistor connected in series with the signal and one to ground.
When you move up one notch it connects a different resistor in series with the signal and a different one to ground, which maintains impedance and so on for each step.

Those motorised units with digital display look really nice, but ouch, are they expensive.

[sq225917]

They are expensive, and mine had a sticky relay so from step 24 to step 32 one channel was down. Not so noticeable for the first few clicks up from 24, but stepping from 32 to 31 was an 8db drop. It's off for repairs. He was super quick in responding to my email and no questions asked. It's a beautiful unit and sounds great, above 32.... ;-)