View Full Version : Croft Micro Basic 25 Valve Pre Amp
In the meantime, I'm due a reality check and am going to force myself to listen to the utterly neutral AVI preamp again.......
I see. You start getting used to the Croft sound. It'll be even nicer to get back, later on. ;)
I do this often. :eyebrows:
Ian Walker
30-01-2010, 15:33
http://wduk.worldomain.net/acatalog/info_WDATTN.html
These look like they'll do the job for next to nowt.
Well, I put the AVI back, gave a few minutes to settle (it doesn't take long) and had a listen on both headphones and "the" Thomas Dolby LP..
I'm in a quandrary...:scratch:
There's no denying that the valve option is *musically* a fantastic listen and all the tweaks Glenn has suggested, together with the valve replacements have increased the objective balance too, but it looks like the pre will have to go to Glenn for some more substantial work at some point I think (he has offered, bless him)..
The AVI at first sounds a bit deadpan, but listening for a good few minutes shows the extra half octave in the bass it has, and the extra ability to delve into the mix, subtle things I know are there somehow seem a bit more intelligible. the downside is that it reproduces compression in the recordings a little too well, the difference between bad and good pressings and discs seemingly bigger.
I think that for the passive system I'm currently using needs the extra "life" and "verve" in the old Croft preamp and I'm sure the current "R" version of the series 25 would answer most if not all of the niggles I'm bleating about. I am glad I've retained the AVI though, as it is a superb product given decent uncompressed sources (I'm hoping for a turntable upgrade shortly)..
HMMM, much to ponder :)
CornishPasty
30-01-2010, 20:01
Yes, thanks Ian. I do have some Rothwell attenuators that I'm using elsewhere and they go in the cd to pre line NOT the pre to power line. That's how Rothwell recommend you use them as do World Designs. There's nothing to stop anyone using these attenuators between pre and power but my pre is not overdriving the power amp, the cdp is overdriving the pre. All I've done is measure the value of the resistors in the Rothwells and hardwire some resistors into #4 input of my preamp.
Those WD attenuators are very good value for money Ian. If I decide to keep the Croft I'll buy a pair.
DSJR, just like you I've gone back to an old favourite, a much modified NAC42 pre amp. It too has better bass than the Croft and no problem with cd either.
I do appreciate that the Basic is a beer budget preamp, so maybe I'm expecting too much. Marco, I'm guessing your Charisma X will be much more expensive than a Basic and therefore better sorted.
My power amps are a pair of 100 watt mosfet monos made by a company called BLTS. I doubt they're still in business, the amps were made in 1983. I was going to pull them apart for bits, especially the large 50-0-50 toroids, but they sound to good to scrap, so I've recently recapped them and given them a bit of a make over.
Hi Ralph,
Marco, I'm guessing your Charisma X will be much more expensive than a Basic and therefore better sorted.
Errm, yes, just a tad! ;)
Still, the gain does seem to be set a little high on the Micro, as even the position of the volume knobs shown earlier by Dave makes it look a little out to me.
On the Charisma (bearing in mind that I've reversed the way that the volume pot works), things don't start to get really loud (with CD) until the 11 'o clock position - and that's with 95db Tannoys and a 'meaty' P/P valve amp.
On the Micro, that should equate to around 5 'o clock on the dial, not just shy of 2 'o clock - but then there are so many variables.....
It's a difficult one to analyse properly.
Marco.
Would be interesting to check the input sensitivity of the amps though. the input of the Croft in standard form is designed to take a CD player with no clipping.. With the Quads I have, the Series 25 was set well up on the volume controls with a CD source.
Ali Tait
30-01-2010, 22:17
Well, I put the AVI back, gave a few minutes to settle (it doesn't take long) and had a listen on both headphones and "the" Thomas Dolby LP..
I'm in a quandrary...:scratch:
There's no denying that the valve option is *musically* a fantastic listen and all the tweaks Glenn has suggested, together with the valve replacements have increased the objective balance too, but it looks like the pre will have to go to Glenn for some more substantial work at some point I think (he has offered, bless him)..
The AVI at first sounds a bit deadpan, but listening for a good few minutes shows the extra half octave in the bass it has, and the extra ability to delve into the mix, subtle things I know are there somehow seem a bit more intelligible. the downside is that it reproduces compression in the recordings a little too well, the difference between bad and good pressings and discs seemingly bigger.
I think that for the passive system I'm currently using needs the extra "life" and "verve" in the old Croft preamp and I'm sure the current "R" version of the series 25 would answer most if not all of the niggles I'm bleating about. I am glad I've retained the AVI though, as it is a superb product given decent uncompressed sources (I'm hoping for a turntable upgrade shortly)..
HMMM, much to ponder :)
That AVI pre is superb.It's doing exactly what it should,I.e. disappearing.Saying that,it doesn't do the valve thang.Detractors say valves are coloured.If that's the case,then I'll live in a coloured world thanks! That AVI pre is great,but you just don't get the emotional connection that you do with valves.
Ali Tait
30-01-2010, 22:19
Just MHO.
Just MHO.
;)
Everytime I go back to tubes, I realize this simple truth...
(and my heart whispers: forget the measures !)
....because measurements don't tell the whole story!
And that's and old story ;)
Marco.
CornishPasty
31-01-2010, 09:49
I don't think there's anything wrong with the gain of the Micro, it just doesn't like 2 volts from a cdp. It's a very simple design and unfortunately I think that's the cause of the problem.
As for the sensitivity of my amps, I've had the Micro driving a 300B set and an old HK Citation 12 with the same results. The previous owner suffered the same thing and that's why he sold it.
A thought did occur to me. What about another switch on the front panel to alter the value of the feedback resistor to give two gain options? 150K across the original 470K will give just under 114K which is near enough I think.
Ralph, yes, I'd try that - or, better still, speak to Glenn about it and I'm sure he'll be able to fix your problem :)
It'd be a shame to give up on an otherwise excellent preamp, whose particular sonic benefits and way of music making you may not get elsewhere...
Contact Glenn, mate!
Marco.
I don't think there's anything wrong with the gain of the Micro, it just doesn't like 2 volts from a cdp. It's a very simple design and unfortunately I think that's the cause of the problem.
I'm certainly repeating myself, but I noticed nothing when used with various 2v sources and the Denon amp... The pots at the basic were at 6 o'clock for normal listening. ;)
So, I suspect it has more to do with the amp after the Croft than with the source gain.
hifi_dave
31-01-2010, 11:19
I can say, categorically, that selling Croft pre's since 1982 (I think it was), I have never had anyone complain about such a problem. An e-mail to Glenn should resolve the matter.
Hi Dimitri,
So, I suspect it has more to do with the amp after the Croft than with the source gain.
I'd agree, however, whatever power amp Dave (DSJR) was using earlier with the Micro seemed to be causing a similar effect, as in my experience, the sound should not be so loud with both volume knobs only at 1.30.... On my CX, the same position in the other direction, would mean that the volume was barely on.
Marco.
CornishPasty
31-01-2010, 11:44
Problem sorted.
Up for low gain, down for normal gain.
http://i63.servimg.com/u/f63/11/73/38/69/croft10.jpg (http://www.servimg.com/image_preview.php?i=678&u=11733869)
http://i63.servimg.com/u/f63/11/73/38/69/croft_10.jpg (http://www.servimg.com/image_preview.php?i=679&u=11733869)
http://i63.servimg.com/u/f63/11/73/38/69/croft_11.jpg (http://www.servimg.com/image_preview.php?i=680&u=11733869)
Very neat solution, Ralph. Glad you sorted this. You did that yourself ?
Looks like a very neat job - well done.
I hope that this now means you can enjoy the line stage for the good things it can offer and not be annoyed with it :)
You know, Andre may dislike this point to point construction, but what a simple line stage it is. It has to be better than op-amps with tons of miniature transistors inside...
CornishPasty
31-01-2010, 12:41
Yes Themis, all my own work. Took me an hour to do this morning. Just a spot of black paint needed around the hole I drilled for the new switch.
Point to point wiring is just so much better. It's much easier to work with too. With a pcb the path doesn't always take the most appropriate route. My Naim preamp is just such a case. Some of the tracks go all around the board to get between two points inches apart. I did a lot of track cutting and hard wiring and the results were very rewarding.
Integrated circuits do have their place but not in one of my amps;) I'm digressing.
Yes DSJR, I'm enjoying listening to my Croft as I type this :) It's surprising how a small thing like this can detract from one's listening pleasure.
Yes Themis, all my own work. Took me an hour to do this morning. Just a spot of black paint needed around the hole I drilled for the new switch.
I envy you. Very neat, indeed. ;)
The first time I listened to the Basic, I had almost tears in the eyes. This amp has a way of transcribing strings that is exceptionally near my long-term memory. And as the music I grew up with (traditional Greek) is composed mainly of strings it was a shock. :)
Yes DSJR, I'm enjoying listening to my Croft as I type this. It's surprising how a small thing like this can detract from one's listening pleasure.
Good work, Ralph! Achieving the correct gain structure in a system is fundamental to the accurate portrayal of music, and hence one's enjoyment of it thereof. The ear is very sensitive to these things :)
Marco.
Hi - I am looking into getting a Micro 25. I have been offered the line stage only version for £420 (as opposed to the £700 for the version which can be paired with a record player).
Does anyone think that is a good deal? I want something with a classic tube sound to go in between a Cyrus cdp and a powerhouse Bryston power amp. In £ terms the croft would be the weakest link with an RRP of way less than all my other components, but I have overshot myself with some other bits of kit and have a limited budget left for a pre.
I have recently been using a passive pre amp with class D ampflication and found the sound to be quite bright, shouty and a bit dry. I am not seeking huge amounts of granular detail, but do want something this a nice warm tone.
My slight concern is that Crofts seem to be used with record players quite a lot. Does this mean it might not be a great partner for a CDP? Also, I notice the line version only uses one tube. I am not a technical expert, but have seen that most line level tube pre amps use at least 2 if not 4 tubes. What difference do more or less tubes make? I thought it would need at least 2 tubes, one for each channel, but I guess that shows how much I know...
Opinions appreciated.
Thanks.
Nicky
Croft products DO NOT sound like "classic" valve stuff, as they're far too well performing for that. You will have air and space with an almost palpable image between and around the speakers, but I guarantee that there's no soggy bass and soft treble...
The line stage of the 25 is excellent and the various differences in CD players is reproduced very well IMO. The highish input impedance will keep these differences to a minimum I think, although HiFi dave's been all but wetting himself over the valved Rega Isis CD player.
If you find you need a phono stage, in addition to the wonderful bargains out there, the £500 Croft one is the "R" spec stage with its own supply and tweaked componentry unless I'm mistaken (the 25 "R" features twin supply transformers).
check this site out> http://www.bigearsaudio.org.uk/valve_amps/used_valve_amplifiers.html
CROFT micro pre-amp £375 Dual mono, good valve phono stage.
you won't be disappointed, the owner is a great and knowledgeable chap selling excellent gear, and there is always a chance for a bargain... good luck :)
Ali Tait
08-03-2010, 17:49
Some very nice gear on there.
Nice prices for paupers like me as well...... :(
The Grand Wazoo
08-03-2010, 20:54
I notice the line version only uses one tube. I am not a technical expert, but have seen that most line level tube pre amps use at least 2 if not 4 tubes. What difference do more or less tubes make? I thought it would need at least 2 tubes, one for each channel, but I guess that shows how much I know...
I don't know what the valve is for sure but I'd think it's a dual triode, - two valves in one. One half per channel.
Cheers
Ali Tait
08-03-2010, 21:02
Yup.My WAD Pre 2 is the same,one ECC88 does both triodes.Twin triode in one bottle.
Thanks for all the replies.
The vintage croft mentioned above is a little old school for me but thanks.
My question about one valve wasn't that dumb after all then! :) I did wonder how it would do both channels. That explains everything.
Would you guys think that £420 for a linestage only version of the Micro 25 is a good deal? It is essentially a new unit, I am told, and I would have a guarentee etc.
The Grand Wazoo
09-03-2010, 13:56
I'll tell you what Nicky, we'll do you a deal!
Before anyone answers that question, why don't you dive into the Welcome section and type out a short introduction telling everyone a little about yourself, roughly where you're from, what your system consists of & what kind of music you like to listen to. Then we'll all know each other a little better!
Cheers
Haselsh1
09-03-2010, 16:25
Thanks for all the replies.
The vintage croft mentioned above is a little old school for me but thanks.
My question about one valve wasn't that dumb after all then! :) I did wonder how it would do both channels. That explains everything.
Would you guys think that £420 for a linestage only version of the Micro 25 is a good deal? It is essentially a new unit, I am told, and I would have a guarentee etc.
The Micro 25 Basic is 350 quid brand new and complete with a phono stage. I'm not sure how 420 quid without a phono stage for a Micro 25 stands up against that.
The Micro 25 Basic is 350 quid brand new and complete with a phono stage. I'm not sure how 420 quid without a phono stage for a Micro 25 stands up against that.
The Micro Basic WAS £350 with a phono stage, but I understand that it's not currently available unless a dealer's flogging his demo one. When and if it returns, there may be a price rise of fifty notes or so...
The Micro 25 should sound better - i.e. more refined, as I understand the power supply is better and a component or three may be better too, although I've not had the tops off to compare...
Haselsh1
09-03-2010, 16:37
The Micro Basic WAS £350 with a phono stage, but I understand that it's not currently available unless a dealer's flogging his demo one. When and if it returns, there may be a price rise of fifty notes or so...
Bugger...!!!
It looks as though I timed that just right...!
Bugger...!!!
It looks as though I timed that just right...!
Check with HiFi Dave! As one of Glenn's longest established dealers/friends, he might be able to pull something out of the bag....
I doubt Glenn was making much on the basic and it probably isn't worth his while as it probably takes as much time to build. The standard Series 25 IS an incredible bargain sonically though and I believe ALL Croft products fetch good money used - the Series V power amp on here went for £550 IIRC which is roughly what its new price would have been..
hifi_dave
09-03-2010, 16:58
I'm sorry to say that DSJR is correct.
I guess that Glenn has realised he was making naff all (inc VAT) on the Micro Basic and he has increased the price by 50 quid to a massive £400 inc VAT....:eyebrows:
Obviously this is still a derisory sum for such a brilliant pre-amp - hand made with a stunning phono stage included but it needed to happen.
Haselsh1
09-03-2010, 17:12
The truth is, we're not in business as a charity...!
Haselsh1
09-03-2010, 17:16
The Croft pre/power combo is clearly worth a grand of anyone's money but of course that's only true if you have the grand at your disposal. All in all, a fabulous amplifier combination made even better now I have the Beresford Caiman.
Well, I ordered the ex dem corft. Four hundred quid for the line stage version. If I ever want to dabble with turntables I will get the seperate phono stage.
Interesting dealing with Glenn. He is a "no bullshitL kind of person and told me tube rolling was snake oil. That surprised me! I thought he would be in favour of it.
Does tube rolling make a difference on the micro? Also, does anyone have experience of doing it, I mean, its easy to do, right?
The Grand Wazoo
11-03-2010, 09:01
Well, I've never done it with a Croft but my experience with this is that it's can be one of the most cost effective changes you can make with a preamp. But that would depend on:
- how many different types you have to try before you find 'the one'.
- whether what's fitted already is best suited to your ears already or not. Glenn may have already done that work for you!
- you being aware that this can be very hit & miss (esp. with old stock valves that may not be what the vendor tells you they are).
I'd say that with only one valve in that unit, the job would be made very much easier and cheaper though.
You shouldn't really be thinking about that till you've had the unit for at least a reasonable enough time for you to get to know it's basic sound - you may love it as it is!
Cheers
Haselsh1
11-03-2010, 09:10
I've had my Croft Micro 25 Basic since before Christmas 09 and I still haven't started swapping valves around yet. I shall not be doing that until I am 100% sure I know its sound inside and out. I am very tempted by some nice JJ's though.
Stratmangler
11-03-2010, 12:06
What tubes are in it now ?
To be honest it's one area of thermionic amplification devices that causes me concern - the tonal characteristics and the variable electrical/mechanical dependability of different brands.
Chris;)
hifi_dave
11-03-2010, 16:47
Playing with tubes is not something I bother much with nowadays but it's not such a big deal. You keep the original tubes, plug in the new ones and if they sound better you keep them in. If they sound worse you oik them out and put back the originals...:scratch:
Hi.
I have tried another ecc83 in my Croft series 7. Ecc83 for the regulated ht.
And for me there is a huges different in the jj83 and now my ecc83 miniwatt philips.
I will try the line stage tubes later.
best jan
Changing the value and/or make of the caps can make a difference as well, not sure if this is worth while on this Croft or not but i have seen it done on other Croft Amps
I think Marco found that the 25 "R" preamp with carefully selected "standard" components and valves wasn't very far behind his tweaked out, whizz-bang EXPENSIVELY RE-CAPPED, CUSTOM ATTENUATED and re-valved Epoch, or whatever it was originally. I'm not saying the 25R was easily as good, merely to point out that to get that extra 10% or whatever, Marco had to spend some hundreds of pounds on boutique bits...
hifi_dave
11-03-2010, 18:51
The 25R is seriously good. I just wish Glenn would get his bl**dy finger out and make my Seven R power-amp to go with...:rolleyes:
I wanted to get replacement for future (occasional) tubes for the 25, and, when I gave Glenn the potential list (with tubes going up to 6 times the price of the Teslas, but without mentioning their price) his answer has :
"If I was you I would stick with the Teslas"
... now, who am I to discuss this ? ;)
The 25R is seriously good. I just wish Glenn would get his bl**dy finger out and make my Seven R power-amp to go with...:rolleyes:
How much does this combination go for Dave ?
Also, not knowing anything about valves, will this combo drive most speakers.
hifi_dave
11-03-2010, 22:26
Well, this is Glenn's current top of the range stuff, so the pre-amp and power-amp are £1400 apiece.
The pre is all tube and the power-amp is hybrid with around 55wpc into 8 ohms. It has more than ample poke for all normal speakers...:band:
Oh, ok.
Bit above my price range, need to listen to something lower down the chain I think.
I need to contribute to this thread, chaps, in order to provide some necessary information and to clarify a few matters...
Rest assured I will do so later once Barry (J Hunt) has left, who's due round for a sesh in about an hour :cool:
Laters, muchachos!
Marco.
Haselsh1
12-03-2010, 15:42
What tubes are in it now ?
To be honest it's one area of thermionic amplification devices that causes me concern - the tonal characteristics and the variable electrical/mechanical dependability of different brands.
Chris;)
Strat, to be totally honest, I haven't a clue what type of valves are in it. They are still the ones supplied by Glen Croft.
My reason for saying I'd like to try JJ's is that I tried those in my Chinese 300B SE amplifier and they were of much lower gain. Given the overall problems trying to set a decent volume and balance using the Croft pre/power, I just thought that lower gain valves would benefit.
Haselsh1
12-03-2010, 15:44
Of course the JJ's would be ECC83's and would therefore only impact on the phono stage, not the line stage. I'm not sure about the line stage valve.
Ian Walker
12-03-2010, 15:48
I'm pretty sure you already have jjs in the Croft pre,thats what was in the 25R i tried.
Regards,
Ian.
Haselsh1
12-03-2010, 16:11
I'm pretty sure you already have jjs in the Croft pre,thats what was in the 25R i tried.
Regards,
Ian.
Hmmm... I guess that stuffed my plans for World domination then.
Yep, Glenn uses JJs.
Richard
HiFi dave's 25 had 83's with a small, squarish "C" surrounded by a "square with curved corners" logo. Apologies, I can't remember the manufacturer...
Tube rolling is very dangerous unless you know what the "straight through" signal sounds like. Changing valves for a nicer or different tone goes against what "HiFi" is all about IMO. It's quite possible to have neutrality and keep the musical interest as well. Again, IMO.
Haselsh1
12-03-2010, 18:52
I've heard that Harma valves are very good and also Philips valves. Watford valves do a good range in very expensive Philips valves.
The Grand Wazoo
12-03-2010, 19:04
Philips owned Mullard, Valvo, Dario & Amperex
hifi_dave
12-03-2010, 21:16
They all sound slightly different, a bit like using tone controls.
guys, i wonder if any of you could insert a pic of Mr. Glenn Croft here, i am pretty curious to see him since have never had the chance, and may not be able to, do so - thankx (i know it may be strange for the some of you, but i have difficulties even when speaking on the phone due to lack of the other's sight, that visible type i am :) )
He does have a simple Facebook page.....
There's a Twinstar 2 up for sale here around these parts. Any opinion on that particular model? I currently have an Exposure Super 18 as my power amp.
He does have a simple Facebook page.....
Dave, can you please advise as how to get there? thnx
Dave, can you please advise as how to get there? thnx
http://www.facebook.com/?sk=ff#!/profile.php?id=1176908201
hifi_dave
14-03-2010, 10:04
guys, i wonder if any of you could insert a pic of Mr. Glenn Croft here, i am pretty curious to see him since have never had the chance, and may not be able to, do so - thankx (i know it may be strange for the some of you, but i have difficulties even when speaking on the phone due to lack of the other's sight, that visible type i am :) )
Well, if you imagine David Beckham with a touch of Hugh Grant - he's nothing like that....:lolsign:
I've got one of him in his favourite baseball cap and cricket t-shirt ;)
Marco.
That's how I remember him :)
Gotta get me Series 4 PP back out methinks, with the absolute phase taken care of.....
Talking about phase, is it normal that between the pre and the power, one of them (don't recall which) has its phase inverted ? :scratch:
It's on purpose, or Glenn simply thinks it has no influence ?
Well, if you imagine David Beckham with a touch of Hugh Grant - he's nothing like that....:lolsign:
;)
http://www.facebook.com/?sk=ff#!/profile.php?id=1176908201
Dave, thanx for the link though can do not much to see him, actually... i may seem to be quite a PITA but feel like not registering for the sole purpose to see Glenn there - i don't like forums like that spying info on you... :(
I've got one of him in his favourite baseball cap and cricket t-shirt ;)
Marco.
Marco, i wonder if you could insert it here...
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