The Marco-boy main system, as of August 2020

Good post, Gaz - shows how you've learned from your experiences and used that info to your benefit (and that of your system). I also think it's no 'happy accident' that you've got into CD again after getting a decent transport, which for me is the key to really enjoying what CD has to offer, and a properly designed dedicated transport makes a big difference:)

It's not just about the DAC, and 'any old transport' will do, off of a DVD player or whatever. For me, that's bollox and simply doesn't tally with my experience.

Unlike you, I've never 'fallen out of love' with CDs, despite embracing streaming (although not to anywhere near as high a standard as you), and of course have never stopped enjoying vinyl, and that's because I've been using the same (top notch) Sony CDP and DAC for the last 11 years, which really shows what the format can do.

So continue enjoying those sliver discs mate, along with everything else. You've got a nicely assembled system going on now, by paying close attention to the details and making properly informed choices, and long may that continue!:cool:

Marco.

Marco, out of interest, why are you using nylon bolts on your cartridge? Is this a recommendation to do with the Houdini?

Hi Adam,

Yes, it's because of how the Houdini is designed. The bolts/screws have to be cut to fit (reduced in size) in order only to penetrate the Houdini far enough to secure the cartridge, but not so far as to upset its suspension.

Plus it also reduces mass, should that be a consideration:)

Marco.

Quote:

---

Originally Posted by Marco

Interesting idea, and one that could work. This is far from an urgent project though (just floating some ideas about, really), so I won't be rushing into anything. As usual, when I've decided to go ahead, extensive research will be undertaken, and the processing of as much relevant info as possible will be carried out before a choice is made.



Yes, so they say, and in certain circumstances that may be true.

However, I've used umpteen different passives in my system with the Copper amp, which is even more sensitive than a Quad 306, and high-efficiency speakers (95db Tannoys), and where on paper a passive should thrive, yet (aside from LDRs), when used the soundstage collapses and they *always* sound soft/veiled/'padded out'/lacking in 'drive' and dynamics (even receiving a 2v digital signal), *in comparison* [that bit is crucial] with the best active designs.

Therefore, given the above and the type of system I've tried passives in, I'm struggling to see what the 'compatibility issues' would be?:scratch:

Don't get me wrong, the sound isn't dreadful or anything like that, with passives, just not up to the high standards I'm used to from top-notch active designs. You have to remember the benchmark I've got as an active preamp...

My modded Croft, in today's market, would likely retail for around £8-10k - it's a very capable, highly-optimised design, which allows serious insight into recordings, and a truly wide-open window onto the music, so that's what any passives are up against.

Interesting though, that LDRs, some of them despite not sounding anywhere near as good as the Croft, don't suffer from a lack of said 'drive', and consequently don't sound soft, so there must be something in their design that negates this.

They're powered by the mains supply, so perhaps that's part of it?

Marco.

---

Hi Marco
LDR's are capable when properly powered to present music exactly as it was recorded. They neither add or subtract from presenting every bit of detail, dynamics that the recording has preserved.

Properly powering them has been my passion and interest for over 13 years. The type of LDR firstly is the encapsulated type NSL32SR3 . The SR3 has the best properties for audio as well as capability of highest resistance range.
The circuit formed on the signal side is a passive L pad, however with a distinct difference, to simply being just variable resistance ( achieved by more or less light intensity ). The difference is the enormous hold or grip which LDR's have on the entire grounding of all audio equipment, that it attaches to. The benefit is a black silence in a unbalanced audio system, that even balanced systems cannot achieve. To make this occur the LDR anodes needs to receive ideally 8 volts or more and have its cathodes not directly grounding, rather far better forming active current drive for the circuitry.

If we think of the most outstanding amplifier circuits that preserve bandwidth such as the cascode and common gate, and we apply those forms to what is ostensibly a DC circuit, we find we suddenly are confronted with added audio properties
occurring on the signal side. Some might say DC circuitry does not need high bandwidth as it is form, is the exact opposite, however if we read manuals such as Designing with Field Effect Transistors 2nd Edition reference is indeed made to using cascodes in DC circuitry. I regularly inform audio forums who muster all sorts of opposition to LDR's, that they simply relay how well or how poorly they are powered, power them well if we speak in positive terms and that is what you hear.

Comparison then to other passives that do not have this grounding grip as we are calling it , has LDR's in a area all of their own. Other passives use ideally or represent approximately 15 k of resistance at mid volume in usually equal halves as a potentiometer, variations are those with log curves meaning there is usually a taper in the volume curve . The benefit with LDR's is they emphatically do NOT have to follow potentiometer set curves and forced restrictions.

We are thus free with LDR's to have total control over where the shunt pair becomes active vs the series pair. Another is that we can have total silence at zero volume, simply by arranging a voltage reference pushing appropriately against the series cathodes. Which begins to ask, what is ideal resistance of the potentiometer used in LDR's and what is its best positioning. In my circuits I can proudly say there are NO resistors on the main board - none at all ! Rather I have solved all need of resistors, with semiconductors. Most of the semiconductors used therefore are very close internally to exactly half the potentiometer resistance value, so the potentiometer used for attenuation is just seen as yet another semiconductor resistance value and in effect semi disappears as a device. The potentiometer is placed between the series cathodes volume UP, and shunt cathodes volume down. When measured we find some really good impedance characteristics for matching to source components and to power amps. Typically 1k3 on the shunt pair at half volume and 2k to the series pair. If we compare this to a stepped attenuator or a potentiometer passive it is losing badly in terms of connecting the source component and power amp, as it has much higher resistance in order to function. LDR's therefore connect not only all your grounding paths with grip, but also connect to the source component and power amp in near perfect relationship.

I hope that helps to answer some of the mysteries. Please let me know if I can help further.

Hi Chris,

Thanks for that, much appreciated. I think this part kind of suns up what you're saying, especially the emboldened text, in reference to what I was describing earlier:

Quote:

---

Originally Posted by Light Dependant Resistor

Rather I have solved all need of resistors, with semiconductors. Most of the semiconductors used therefore are very close internally to exactly half the potentiometer resistance value, so the potentiometer used for attenuation is just seen as yet another semiconductor resistance value and in effect semi disappears as a device. The potentiometer is placed between the series cathodes volume UP, and shunt cathodes volume down. When measured we find some really good impedance characteristics for matching to source components and to power amps. Typically 1k3 on the shunt pair at half volume and 2k to the series pair. If we compare this to a stepped attenuator or a potentiometer passive it is losing badly in terms of connecting the source component and power amp, as it has much higher resistance in order to function. LDR's therefore connect not only all your grounding paths with grip, but also connect to the source component and power amp in near perfect relationship.

---

Do you think that the higher resistance you've outlined, together with the lack of "grounding paths with grip", explain why with the passives I've used to date in my system (despite it on paper being 'ideal' for incorporating such a device), music reproduced sounds 'subdued' and lacks 'life' [best way I can describe it] compared with when done by a good active preamp or LDR?

For me, what you say makes sense and confirms my listening experiences in that respect. I'm convinced that a) I'm not imagining the effect, and therefore it's real, and b) that it isn't due to the artifice of an active preamp (in this case my Croft) making the sound appear as superficially 'more exciting', and therefore creating a false effect.

To my ears, it's definitely the other way round, and in fact the passive device robbing the sound, and subsequently the music, of elements that should *actually* exist!:)

Marco.

Yes that nails it, passives other than LDR's, alter the ideal source to power amp relationship by using too much resistance, just when less is needed. In effect as you say, robbing us of the life in music that is actually there in abundance.

The fact that LDR's solve other passives failings, in their unique way, connecting us so well with the music, is why I have been so excited about them, all these years.

Yes, your current Stereo Coffee is the best LDR I've heard, and which no doubt will become even better when fitted with the latest boards!:)

It certainly pisses all over any other 'passive preamp' I've heard.

Marco.

Btw, just an addendum to the 'which preamp to partner the 306 with' conundrum.... After having carried out some research, I've decided to go for a late (grey-version) 44, and have it modded/upgraded by Redhill or similar - the full monty, with off-board PSU!

So if anyone sees or knows of any for sale [only minty examples would be of interest), let me know!:cool:

Marco.

I use these voltage regulator tubes in my Croft preamp, and I've been wanting this one for a while, as it's a special (and rare) military spec version, from the 1950s, of the 85A2:

https://imagizer.imageshack.com/v2/1...922/aAXwHJ.jpg

https://imagizer.imageshack.com/v2/1...924/fP8usS.jpg

I've rolled these VR tubes before, and the best ones always make a nice difference, so will be interesting hearing what this one does!:)

For the Croft's line stage, I've also just bought a rather nice matched Pair of 1940s Raytheon 6SL7GTs in gray glass:

https://imagizer.imageshack.com/v2/1...923/ylyt4m.jpg https://imagizer.imageshack.com/v2/1...924/EFKxQm.jpg

Looking forward to hearing those, too!:cool:

Marco.

I haven't used one of these in the Croft for years, but had very fond memories of it, so decided to take the plunge and treat myself to one, which as you can see has been fully tested and is conforming to spec, courtesy of AnthonyTD of Tube Distinctions:

https://imagizer.imageshack.com/v2/1...924/YYuq8A.jpg

https://imagizer.imageshack.com/v2/1...922/wXF5MV.jpg

https://imagizer.imageshack.com/v2/1...924/1GJdq0.jpg

https://imagizer.imageshack.com/v2/1...922/aA1q5L.jpg

It'll be interesting comparing it with my current favourite ECC83/12AX7 type, which is my rather rare and superb sounding La Radiotechnique, of a similar vintage, as shown here where I bought it from (read the description): https://reverb.com/item/4913765-la-r...d-1967-vintage

https://imagizer.imageshack.com/v2/1...923/BzKR5g.jpg

https://imagizer.imageshack.com/v2/1...924/UTZ0Lh.jpg

It'll be interesting seeing if the Mullard can better it!:cool:

Marco.

Quote:

---

Originally Posted by Marco

I use these voltage regulator tubes in my Croft preamp, and I've been wanting this one for a while, as it's a special (and rare) military spec version, from the 1950s, of the 85A2:

https://imagizer.imageshack.com/v2/1...922/aAXwHJ.jpg

https://imagizer.imageshack.com/v2/1...924/fP8usS.jpg

I've rolled these VR tubes before, and the best ones always make a nice difference, so will be interesting hearing what this one does!:)

For the Croft's line stage, I've also just bought a rather nice matched Pair of 1940s Raytheon 6SL7GTs in gray glass:

https://imagizer.imageshack.com/v2/1...923/ylyt4m.jpg https://imagizer.imageshack.com/v2/1...924/EFKxQm.jpg

Looking forward to hearing those, too!:cool:

Marco.

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Tried those exact 6sl7gt they are ok but there are better to be had

Lol, churz. I'll let you know what I think mate, as results vary wildly with tubes, depending on the kit used and also the system:)

Marco.

Quote:

---

Originally Posted by Marco

Lol, churz. I'll let you know what I think mate, as results vary wildly with tubes, depending on the kit used and also the system:)

Marco.

---

I'm also looking to roll the ECC88s. The Mullard are always a great choice in our pimped up pre amps, Marco [emoji16][emoji106]

I've also used NOS Teslas too... They were excellent.

Sent from my 9001X using Tapatalk

Lol, cheers, Jo. Did you mean ECC83s, though? There are no ECC88s in my Croft, and the M8137 is a premium version of an ECC83. It'll have to go some though to better the vintage RTC 12AX7S, I'm currently using. However, I'm confident it will, or run it very close. It certainly should at £175!:eek:

I just wanted to introduce some 'Mullardy goodness' into the mix, as I haven't had any in the Croft for a while, so hopefully the M8137/M8098 combo will prove fruitful! Both are due to arrive tomorrow, so all will be revealed shortly!:cool:

Marco.

Quote:

---

Originally Posted by Marco

Lol, cheers, Jo. Did you mean ECC83s, though? There are no ECC88s in my Croft, and the M8137 is a premium version of an ECC83. It'll have to go some though to better the vintage RTC 12AX7S, I'm currently using. However, I'm confident it will, or run it very close. It certainly should at £175!:eek:

I just wanted to introduce some 'Mullardy goodness' into the mix, as I haven't had any in the Croft for a while, so hopefully the M8137/M8098 combo will prove fruitful! Both are due to arrive tomorrow, so all will be revealed shortly!:cool:

Marco.

---

Agh... 88s? Nah, 83s for defo... Sorry bout that.

Sent from my 9001X using Tapatalk

Interesting to see what your doing with valve rolling. I've got the Tunsgram 85A2, I've tried the GEC CV449 and Phillips CV449. The Tunsgram sounds so the best so far, I've not even seen that Mullard before so I might have a go with one. I didn't realise the Mullard 8137's were going for £175 a piece :eek: I've got 6 in a stash, 3 of which are in my 834p clone. The valves are worth more than the clone. :wowzer: FWIW I think the 8137 are the best ECC83 variant I have ever heard.

Quote:

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Originally Posted by The Black Adder

Agh... 88s? Nah, 83s for defo... Sorry bout that.

---

Lol - no worries. What kind of valves (makes) have you got in your Croft - do you remember, when was the last time you were in there?:D

Marco.

Quote:

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Originally Posted by REXTON

Interesting to see what your doing with valve rolling. I've got the Tunsgram 85A2, I've tried the GEC CV449 and Phillips CV449. The Tunsgram sounds so the best so far, I've not even seen that Mullard before so I might have a go with one. I didn't realise the Mullard 8137's were going for £175 a piece :eek: I've got 6 in a stash, 3 of which are in my 834p clone. The valves are worth more than the clone. :wowzer: FWIW I think the 8137 are the best ECC83 variant I have ever heard.

---

Yeah, there are military spec versions of pretty much every Mullard valve, as back in the day many of them were used in military applications, and then later in professional civilian ones, such as the telecommunications industry, both of which where reliability and longevity was paramount.

This meant that the build quality needed to be top-notch, and subsequently the best materials were used for constructing every aspect of the valves, and which is precisely what improves their performance, from an audio perspective [usually resulting in them being less microphonic, for starters].

It's also why they're worth paying a premium for, as not only are they likely to sound better than other valves of the same type, but will last maybe 100 times longer! Simply because in most audio applications, compared with where they would've been originally designed to operate, they're not really being 'taxed'.

Therefore, valves such as this, along with the likes of original GECs, etc, are generally always worth the investment!:cool:

Marco.

Just scored a nice matched pair of these vintage tubes. 'Coin Base' RCAs are often frowned upon by audiophiles, but I actually like using them (and vintage RCAs in general), in key areas of the Croft's phono stage.

They have a nicely open, punchy and dynamic sound, and not in any way thin-toned [as is often their criticism] when used in the right circuit, and which doesn't need the rather 'plump' bass enhancement of 'phat' sounding tubes. When tube rolling, and subsequently optimising the sound, it's all about successfully combining 'flavours'!:)

Anyway, here are the little 'tall-bottled' bastards...:D

https://imagizer.imageshack.com/v2/1...922/tF3nGn.jpg

https://imagizer.imageshack.com/v2/1...922/5oFP5k.jpg

https://imagizer.imageshack.com/v2/1...924/MbsIGD.jpg

Nicely constructed... Look at those nice fat shiny pins!

Oh, and as an aside, this is a rather interesting site, detailing the history of many different valves, but this bit is involving 6SL7s and their history, which folks here using them should read: http://vinylsavor.blogspot.com/2016/...onth-6sl7.html

:cool:

Marco.

Ok, so now that the Lentek's been modded, and sounding STUNNING [more on that later], it's time to start on my valve headphone amp! Firstly, just to remind folks what the internals look like again:

https://imagizer.imageshack.com/v2/1...922/jO1bUl.jpg

https://imagizer.imageshack.com/v2/1...924/7WfpD5.jpg

So... To begin with, I've sourced some quality NOS Melz tubes (including some as spares), to replace the, no doubt, modern Chinese one that'll be in it above: https://www.ebay.com/itm/6N16B-V-602...72.m2749.l2649

Secondly, I've just bought a rather nice NOS 50K Alps Black Beauty pot, originally intended for use in a McIntosh amp, which (with some jiggery pokery to the PCB, moving some caps around, etc, which Anthony will be doing) will replace the existing cheap pot:

https://imagizer.imageshack.com/v2/1...922/NJ9mx8.jpg

https://imagizer.imageshack.com/v2/1...923/B6CHin.jpg

https://imagizer.imageshack.com/v2/1...924/ZFmEY9.jpg

https://imagizer.imageshack.com/v2/1...923/NS8Fpy.jpg

I was originally going to fit a stepped attenuator, but decided to go down a different route for this project.

I've always liked the Alps BBs, which have a very detailed and musical sound, perhaps not quite as 'upfront' or transparent as the likes of the DACT stepped attenuator in the Croft, but it will compliment the sonic signature of this headphone amp nicely - and NOS Alps BBs (highly-regarded but long discontinued) are pretty rare these days!

Anyway, that's stage 1 and 2 of the mods, which I'll analyse separately first before starting on any alterations to caps or resistors, with the aim in the end of creating a 'giant killing' headphone amp, which majors on the highest SPPV!:cool:

Marco.

Just a little update on the Mullard M8098 voltage regulator and M8137 combo... Well, oh lordy it's stunning!:eek::wow:

It's undoubtedly the best combination of those valves I've ever heard in the Croft. I've no idea why I stopped using an M8137 (as a premium ECC83 equivalent) and started messing around with other makes of valves, as it is quite simply THE BEST.

As good as the La Radiotechnique 12AX7 is I was using before, and it's a superb sounding tube, the M8137 takes things to another level.

Quite simply, it does the classic 'Mullard thing', which is a producing a lovely natural, open, detailed and lucid mid and top end, such that it often makes valves of the same type from other manufacturers sound rather false and tonally 'forced', (zingy/fuzzy) in comparison - and somewhat like using a tone control, where certain aspects of the frequency response were artificially boosted or muted.

The M8137, in comparison, sounds very even-handed and 'linear', top to bottom throughout the frequency range, and in terms of the low frequencies, they're firm and full but not in any way overblown. Detail retrieval has also gone up a notch, with subtle nuances popping out in musical mixes that previously were glossed over. In conclusion, it's pretty obvious why these valves are so sonically sought after!

However, a special mention must go to the M098, which is head and shoulders the best version of the 85A2 I've heard. This one is vintage 1950s 'golden era' valves at its best. For me there's a unique musicality to valves from this era (or earlier), especially military spec ones such as this.

When I received this valve today from Langrex, it came in a lovely original box, carefully wrapped in its original packaging, totally untouched and NOS, along even with its original guarantee certificate, which had clearly never been opened! The whole thing 'felt' special before I'd even installed it and listened to it. However, the most special thing about it is the sound....

Rather uncannily, it seems to have lowered the Croft's 'operating noise-floor', widened the soundstage and also held music in more of a vice-like grip, such that bass is tighter and more extended, with heightened rhythmic alacrity - almost as if a bigger power supply had been fitted - it's just scarily good and hugely addictive!:eek:

So... If you've got a Croft preamp (or other amp) that uses this type of voltage regulator, and can find an M8098 voltage regulator valve, then my advice would be snap it up, tout suite, and prepare to hear it like never before.

Marco.

Thats good news regarding to M8098 I managed to get one some time ago but never tried it in the Preamp. Looks like I'll be unhooking the Croft again!

No worries, Andy. I think you'll like it:)

Btw, those 1940s-vintage Raytheon grey-glass 6SL7GTs have arrived - remember the ones you said were ok but nothing special? Well, in my Croft these specific ones are sounding SUPERB, and among the best I've heard! Very wide-open, detailed and dynamic, and create a vast 'walk around' soundstage - hugely impressed!:cool:

Are you sure that the ones you had were NOS military-spec 1940s vintage, and not later examples? IME, the very early 6SL7s, produced during the 40s, for military applications, invariably sound best, and considerably better than later examples.

Marco.

I've had a look at your photo and I notice that one of your valves appears to be National Union and the other Raytheon. Are they the same? It could be that you have two VT229's but re badged under two differing names? They do look identical, you'll need to check the internal construction and make date. Yes I have tested those valves, they are down the list of the one's I've tested, in at number 7. I've tried 12 different types now and you'll notice that the upper spots are dominated by special military variants with the 5691, so far, being the best I've heard. I've included below what I've trialled. There some notable exemptions such as Mullard ECC35's and the Melz 5 dot versions, they will appear at some point on the horizon so at the moment I stalk the USA for different 6sl7's.

1. RCA 5691 (Red Base) 9.75/10
2. Bendix 5691 (Red Base) 9.75/10
3. Tung Sol 6S7GT (Black Bottle) 9.6/10
4. Tung Sol 6SL7GT (Orange base) 9.5/10
5. Mullard 6SL7GT (Black base) 9.25/10
6. Ken Rad 6SL7GT (Black Base) VT229 9.25/10
7. Raytheon 6SL79 VT229 (Black bottle) 9.1/10
8. Tung Sol 6SL7GT VT229 (Black bottle) 9.1/10
9. General Electric GSL7GT (Black base 1970's) 8.75 / 10
10. Slyvania 6SL7GT black base 7/10
11. Brimar 6SL7GT (black base) 6.25/10
12. Reflektor black base 70's version 5/10

Hi Andrew.

Just a note, Marco's are grey glass. We're yours the same?

Sent from my 9001X using Tapatalk

I'd like to do some rolling. I have Brimar Mill spec 1988 black glass 6SN7s in my copper. I'd like to give something else a go.

As for my croft. I still have the Synvania 6SL7s mill spec in my phono stage as recommended by Marco quite a few years ago now.

Sent from my 9001X using Tapatalk

Quote:

---

Originally Posted by The Black Adder

Hi Andrew.

Just a note, Marco's are grey glass. We're yours the same?

Sent from my 9001X using Tapatalk

---

Hi Jo,

Yes they are the same. I've seen quite a few forums over in the USA where these values are simply referred to as "black bottles" I don't think they differentiate. But in the picture they do look grey, perhaps they are a slight variant?? I'd wager money they are probably made by the same company and sourced out the Raytheon and National Union. They do look identical. I've tried the Slyvania 6SL7GT black base and found them to be a nice sounding valve and I lived when them for quite some time until I went nuts and started by different matched pairs of 6SL7's every Sunday night after a few drams of single malt!

Hi guys,

Firstly, the glass is defo grey, not a black of any description!:)

And yes, both are VT-229s, so military spec 6SL7GTs. One is badged as Raytheon, and the other as National Union. The internal construction of both valves is identical. It's my understanding that Raytheon (once a huge electronics and vacuum tube producing company) had some of their tubes rebranded under different names, one of which was National Union. So essentially they are Raytheons.

The key factors in terms of how good they sound is that they are a very closely matched pair, indeed one valve is fully balanced, and that they are 1940s vintage. That last bit is CRUCIAL, in terms of ascertaining if the ones you've had, Andy, were the same. IME, even one or two years of age difference can have a significant impact on matters.

Therefore, 1950s, 60s, 70s or later ones, all sound quite different, with the earlier varieties invariably always being best. Therefore, ONLY if yours were 1940s vintage and grey-glass can you say you've heard the same valves... I also like red-base 5691s, but unlike you they aren't my favourite 6SL7.

As I've said before, mate, results are totally dependent on the circuit used, and we've already identified in a previous discussion we had about 5691s, with your Croft needing modified by Alan before it could take them, and mine not, so clearly our amps react differently to the valves used, therefore proving that it's pointless compiling lists of 'The best 6SL7s', in a sense that it will apply universally or be definitive, which of course for reasons stated it can't.

In that respect, unfortunately, there is no 'one size fits all' valve, of any description, but nonetheless that doesn't stop you or I recommending specific ones, and it being interesting (and also potentially beneficial) to others:cool:

Marco.

Quote:

---

Originally Posted by Marco

Well, until I have a peek inside, that's not been confirmed!;) So we'll see...

---

Which we did today and the answer is 12uF

https://live.staticflickr.com/65535/...5d6b096a_c.jpg

The next big question, is what will you replace it with?

Quote:

---

Originally Posted by The Black Adder

I'd like to do some rolling. I have Brimar Mill spec 1988 black glass 6SN7s in my copper. I'd like to give something else a go.

As for my croft. I still have the Synvania 6SL7s mill spec in my phono stage as recommended by Marco quite a few years ago now.

Sent from my 9001X using Tapatalk

---

try these they are a step above in my opinion https://theartofsound.net/forum/show...-Tung-Sol-6F8G

Quote:

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Originally Posted by karma67

try these they are a step above in my opinion https://theartofsound.net/forum/show...-Tung-Sol-6F8G

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Problem is, Jamie, she needs 4!:eek::D

...and also, physically, the glass envelope of those valves is too bulbous for them to fit side by side, where they need to go, as there isn't much room.

Marco.

Quote:

---

Originally Posted by DarrenHW

Which we did today and the answer is 12uF

https://live.staticflickr.com/65535/...5d6b096a_c.jpg

The next big question, is what will you replace it with?

---

Lol, thanks for that, mate. Could you email me all the pics you took today of the above? If you haven't already got my addy, then PM me for it.

As for what to replace them with... I'm currently considering various options and will report back later!:cool:

Marco.

Quote:

---

Originally Posted by Marco

Hi guys,

Firstly, the glass is defo grey, not a black of any description!:)

And yes, both are VT-229s, so military spec 6SL7GTs. One is badged as Raytheon, and the other as National Union. The internal construction of both valves is identical. It's my understanding that Raytheon (once a huge electronics and vacuum tube producing company) had some of their tubes rebranded under different names, one of which was National Union. So essentially they are Raytheons.

The key factors in terms of how good they sound is that they are a very closely matched pair, indeed one valve is fully balanced, and that they are 1940s vintage. That last bit is CRUCIAL, in terms of ascertaining if the ones you've had, Andy, were the same. IME, even one or two years of age difference can have a significant impact on matters.

Therefore, 1950s, 60s, 70s or later ones, all sound quite different, with the earlier varieties invariably always being best. Therefore, ONLY if yours were 1940s vintage and grey-glass can you say you've heard the same valves... I also like red-base 5691s, but unlike you they aren't my favourite 6SL7.

As I've said before, mate, results are totally dependent on the circuit used, and we've already identified in a previous discussion we had about 5691s, with your Croft needing modified by Alan before it could take them, and mine not, so clearly our amps react differently to the valves used, therefore proving that it's pointless compiling lists of 'The best 6SL7s', in a sense that it will apply universally or be definitive, which of course for reasons stated it can't.

In that respect, unfortunately, there is no 'one size fits all' valve, of any description, but nonetheless that doesn't stop you or I recommending specific ones, and it being interesting (and also potentially beneficial) to others:cool:

Marco.

---

No arguments with those statements, it's fun messing about with stuff innit!!

Quote:

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Originally Posted by Marco

Lol, thanks for that, mate. Could you email me all the pics you took today of the above? If you haven't already got my addy, then PM me for it.

As for what to replace them with... I'm currently considering various options and will report back later!:cool:

Marco.

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I added a pair of Duelund 0.01uF tinner copper bypass caps. They sound bloody lovely.

The ones I'm replacing though, Andy, as 12uF, and I can't get Duelunds in that value.

Marco.

Quote:

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Originally Posted by Marco

The ones I'm replacing though, Andy, as 12uF, and I can't get Duelunds in that value.

Marco.

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Yep, you can keep the 12uF in situ if you like. I seem to remember you saying you really liked the noise they produced. The bypass caps keep the uF value at 12uf (well 12.001 uf) but you get to experience the Duelund flavour! Have a look at post 60, that's what I used. https://theartofsound.net/forum/show...lestion+ditton I also used Janzten Audio Silver Z Cap 2% to recap the XO's. The caps are worth more than the speakers but they sound very good.

Quote:

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Originally Posted by Marco

The ones I'm replacing though, Andy, as 12uF, and I can't get Duelunds in that value.

Marco.

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I use both Dueland and Jupiter copper foil output caps in the output stage of my DAC.

.47 uF Dueland versus 2.2uF Jupiter.

The Jupiter's sound better generally. Smoother and warmer. The Dueland's appear more accurate and possibly a smidge faster.

That might purely be due to capacitance values rather than actual real differences in construction. The capacitance value of the Jupiter's means better bass extension, which may account for the marginal, and I do mean marginal perception of warmth.

That said the character traits of a few of the triodes I use in that output stage work better with the Duelands. But they are in the minority.

As bypass caps some pussy (non man like, small) value of either will probably be fine.

Quote:

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Originally Posted by REXTON

Yep, you can keep the 12uF in situ if you like. I seem to remember you saying you really liked the noise they produced. The bypass caps keep the uF value at 12uf (well 12.001 uf) but you get to experience the Duelund flavour! Have a look at post 60, that's what I used. https://theartofsound.net/forum/show...lestion+ditton I also used Janzten Audio Silver Z Cap 2% to recap the XO's. The caps are worth more than the speakers but they sound very good.

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Ah yes, Andy, interesting idea...I hadn't considered bypass caps. The lower capacitance value of such would certainly reduce costs when choosing 'exotic' replacements!:)

Are you saying that you used the Z-Caps to replace the original 12uF ones, then bypassed them with Duelunds? If not, I'm unsure what you mean.

Marco.

Quote:

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Originally Posted by User211

I use both Dueland and Jupiter copper foil output caps in the output stage of my DAC.

.47 uF Dueland versus 2.2uF Jupiter.

The Jupiter's sound better generally. Smoother and warmer. The Dueland's appear more accurate and possibly a smidge faster.

That might purely be due to capacitance values rather than actual real differences in construction. The capacitance value of the Jupiter's means better bass extension, which may account for the marginal, and I do mean marginal perception of warmth.

That said the character traits of a few of the triodes I use in that output stage work better with the Duelands. But they are in the minority.

As bypass caps some pussy (non man like, small) value of either will probably be fine.

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Thanks, Justers, that's also very useful info:):thumbsup:

Marco.

Also, Andy, how did you work out the value of the bypass caps as optimally being 0.01uF?:)

Marco.

Quote:

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Originally Posted by Marco

Thanks, Justers, that's also very useful info:)[emoji106]

Marco.

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Probably bollox. But factor it into your equation;)

Yeah, dude, but der's skanky-ass, playin' at it bollox, and PRIMO bollox... Dat's PRIMO quality bollox, no shit...:eyebrows:

Marco.

My 15's had a cap value of 4.7uF. I have a later version of 15's than yours. I have no idea why yours is 12uF and mines 4uF's, the dudes at celestion must have had good reasons. I replaced the old knackered 4.7uf caps on the XO with the Jantzen's and loved the sound. I then wanted to try the Duelund bypass caps, I bought a pair and then bypassed the Jantzens, I can see a lot of members rubbing their heads at this point. Well, it worked very very well indeed and I have no intentions of doing any further modding to the 15's XO. The bypass cap has a very very low value so that all the original XO cap values are maintained and the voicing is kept in place. So I didn't work out the optimal value. All bypass caps have similar low values. Hope this roughly explains things.

Makes sense, mate. So do you think that 0.1uF, as bypass caps, would work the same with my 12uF originals, as they did with your 4.7uF, or would a different value be required?:)

Marco.

They should work with original caps. It's always worthwhile getting your xo cap values checked out and making sure they are 12uf. Mine had drifted away from 4.7uf markedly. The Jantzens had +\- 2% tolerance to the 4.7uf value I needed and they actually measured within 0.5% tolerance. I'm not sure what tolerances your old caps on your xo should be probably somewhere between 5-10%. The bypass caps have a very low nominal value, this should keep any desired tolerance very very close to what's needed for your xo, in my instance 4.7uf and in your instance 12uf. I can't understand why a speaker designer would want to use a cap with a specific value only to use something with a 10% tolerance of the value needed. Surely the desired voicing of the speaker is going to be dramatically effected? So my logic was to use something that got me very close to a value of 4.7uf.

Quote:

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Originally Posted by REXTON

. I can't understand why a speaker designer would want to use a cap with a specific value only to use something with a 10% tolerance of the value needed. Surely the desired voicing of the speaker is going to be dramatically effected? So my logic was to use something that got me very close to a value of 4.7uf.

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I can answer this one - because the 4.7uF Jantzen Silver capacitor is £20 but the same value in their budget MKT range is £1!

When the speaker it’s going in is a budget model, that extra £19 is just not viable economically.

As to the 10% tolerance affecting the voicing of the speaker, its effects will be minimal. It will contribute to the sound far less than the natural and unavoidable physical differences between one drive unit and another.

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Originally Posted by Beobloke

As to the 10% tolerance affecting the voicing of the speaker, its effects will be minimal

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Quite probably to the point of being indiscernible.

Thanks guys For the explanations.

Ok, then... 0.1uF bypass caps it is! Now to decide on which sexy-ass babies to strap-on...:eyebrows:

Always fancied trying some nice paper-in-oils in loudspeaker crossovers, so now's my chance!:)

Marco.

Ok... The deed's been done! Decided to go one better than the PIOs I was looking at, and try these Jupiter Copper Foil Paper & Wax jobbies: https://www.hificollective.co.uk/com...il_in_wax.html

https://imagizer.imageshack.com/v2/xq90/924/YvppVr.jpg

Loved the description of the sound:

"Wax with very special sonic characteristics, better damping and thermal characteristics was chosen as a perfect match. Further, new lead termination technique has allowed the music to flow more naturally. Without exception, every detail has been tailored to this specific copper capacitor design. After four years of refinement Jupiter Copper Foil capacitors are here.

Life like vibrance gives the feeling of presence, along with micro-detail, holographic bass, and aural decay that is disarmingly natural, the ears will know immediately."

...so couldn't resist!!:D

And I'll be replacing the stock binding posts with these copper CMCs, which seemed really good value: https://www.hificollective.co.uk/bin...terminals.html

https://imagizer.imageshack.com/v2/1...924/TctIVk.jpg

Full report to follow once Dazza's visited and wielded his trusty soldering iron!:cool:

Marco.