View Full Version : Croft 85a2 valve
Hi
Is there differents in sound with the 85A2 valve.
Any thoughts ?
best jan
It's not in the signal path so I doubt it, unless it's faulty or worn out. Why not ask Glenn for chapter and verse on what it actually does in the power supply circuits he uses it in and what to expect if it goes down?
Hi Jan,
The 85A2/CV449 voltage regulator valve is part of the power supply electronics inside Croft preamps, and therefore does influence the sound, as indeed my experiments in that area have shown.
I've recently been playing with quite a few different ones, from Phillips, Amperex, Valvo, and various types of Mullards, and it's the latter that have impressed me the most, sonically, giving a level of detail retrieval, overall naturalness, solidity and superb projection with vocals, making the others sound anaemic and 'processed' in comparison.
With the Mullards, in general, the older the vintage the better - I've had superb results from late 60s production ones, such as this, which even came with a guarantee/certificate of authenticity:
http://imageshack.us/a/img35/6324/img1206vi.jpg (http://imageshack.us/photo/my-images/35/img1206vi.jpg/)
http://imageshack.us/a/img13/1061/img11681n.jpg (http://imageshack.us/photo/my-images/13/img11681n.jpg/)
http://imageshack.us/a/img204/6209/mullard85a2.jpg (http://imageshack.us/photo/my-images/204/mullard85a2.jpg/)
That's probably the best sounding one I've found so far. However, I also took delivery of one of these yesterday, bought from a valve seller on eBay I've used before: http://www.ebay.co.uk/itm/370619589237?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
http://imageshack.us/a/img526/4599/cv449.jpg (http://imageshack.us/photo/my-images/526/cv449.jpg/)
...and it sounds very good indeed. He's got a few more available, if you fancy buying any yourself. I'm also waiting on these 1968 Chelmer-branded Mullards, in their original boxes, to arrive from the States, and have high hopes for these:
http://imageshack.us/a/img100/2897/chelmercv449.jpg (http://imageshack.us/photo/my-images/100/chelmercv449.jpg/)
Marco.
It's not in the signal path so I doubt it, unless it's faulty or worn out
See my previous post, Dave. It's not in the audio signal path, but it's part of the power supply (in the rectification stage, I think), and many listening tests have confirmed that it *does* indeed influence the sonics of Croft preamps :)
As an aside, the best ECC83 (also featured in Croft preamps) I've heard, by a country mile, are these NOS 1961 Mullard M8214s:
http://imageshack.us/a/img826/8446/2050m2.jpg (http://imageshack.us/photo/my-images/826/2050m2.jpg/)
Utterly, utterly STUNNING sound! Available from here: http://www.tubemonger.com/Mullard_CV4035_NOS_NIB_1961_Prem_CV4004_Whyteleafe _p/2050m.htm
Marco.
At that price, they bloody well should be :)
The 85A2 in my Croft is over twenty years old and the only valve not to have been replaced now. For £7 on the eBay link there's no issue at all and I'm always happy to have my hunches proved wrong :)
Give one a go, Dave. Trust me, I think you'll like the improvement (just allow about 48 hours for the valve to fully burn-in). You know that the Marco-boy is rarely wrong! ;)
Marco.
Your wish is my command sir! :)
Lol - it could give you a nice little upgrade for not a lot of dosh! Btw, what's in your amp, 85A2-wise, at the moment?
That would be useful to know, including a piccy, if you can manage it :)
Marco.
Ordered and paid for...
Can't "whip it out" at the moment, since it's on and glowing nicely at present :eyebrows:
Lol - well, we can't disturb that, can we? :D When your bulb is less 'angry', try it then.
Nice one... Let me know what you think when the new valve arrives :)
Marco.
No wonder I was a bit ambivalent about it - s'cuse the pics..
http://i132.photobucket.com/albums/q8/DSJR_photos/DSCF2472_zps00fe9782.jpg
Here's the date stamp if anyone can date it..
http://i132.photobucket.com/albums/q8/DSJR_photos/DSCF2474_zpsf8aa39fa.jpg
Nice one, Dave. I thought it would be a Mullard. I'm not up on date codes, so not sure exactly how old it is. I would guess 1960s vintage, as it has the older Mullard 'shield' logo. In the 1970s the logo was changed to a 'diamond' shaped one.
Thing is, the one you've just bought is a military spec version, and brand new old stock, so given how much use your current one's had, I doubt you'll not hear the difference when popping in the new one! ;)
Marco.
I look forward to it. that means all the supply valves are now updated (other two are 60's Mullards too).
Hi
I also waiting for some 85a2 valve, to try them in my Croft
jan
The valve arrived today, beautifully packed in an outsize box with "hundreds and thousands" poly chips surrounding it.
Now, I cannot in all honesty say that one valve sounds better than t'other, since the one which was removed has over twenty years varied use behind it and a previous owner from new until three or four years ago, but I can say that I'm glad I did :)
For whatever reason, the sound of the preamp's output now more closely than ever mirrors its input, the slight fuzziness that had crept up on it in recent times very much reduced, if not eliminated, and the rendition of reverb and atmosphere is enhanced if anything (this into the old HH VX300 amp too). The LS5/9's sound as if they've had a tweeter transplant :lol:
Thanks for the suggestion Marco. I don't at all mind updates of this magnitude for a tenner's worth of outlay........
Nice one, Dave. I thought you'd be able to hear a difference... All these 'little things' matter because, cumulatively, they all add up! ;)
Marco.
I have several of these spare as my S4s uses 3 - 1 on the input and 2 on the output circuit.
I remember discussing these tubes with Glenn a while ago - he uses Mullards and all my spares are Mullards - BUT, some examples don't "glow" at the required voltage for the circuit to be stable so I made sure all the ones I use (and the spares) were pre-tested by Glenn to ensure they were up to spec.
Steve
These valves really are "valvey" looking in Mullard form. The CV one I've just fitted is silvered and the only way you know it's working is a faint glow at the tip - the silvered bit hides the gubbins inside.
As I said before, I have no idea of the lifespan of these things or how they behave under different loading conditions, but thanks again for the tip - worth every penny since I love this old preamp and would only change it for the two box Croft RS in all honesty.
Thanks both - just ordered the last one for my Micro II after checking it last night and finding a no-name item in there.
Richard
Richard
As per my post above not all these are created equally - regardless of the manufacturer they need to "glow" at a specific voltage in order to allow the relevant circuit to perform to spec and some just dont. You might want to D/W Glenn and perhaps get some direct from him that he has tested.
Steve
Thanks Steve, for the money it's worth a punt. And I want to compare with what's in there (when I bought it a few years back I shipped it straight to Glenn to replace the neon reference tube and update OP stage to latest spec - while he changed the phono stage valves too, he was happy with the existing regulator in there).
I need to contact him soon anyway - I want to improve the PSU in my basic unit, and I suspect I'll be better off returning it to him to do the work rather than bodging it myself, I'll add it to the list.
Richard
Hi Marco
Have you recived the 1968 Chelmer-branded Mullards 85a2 ?
Sound compare to the old mullard?
jan
Hi Jan,
I got them the other day, and so will be doing that comparison tomorrow. I'll let you know :)
Marco.
Hi Jan,
The Chelmers were good, but the old Mullard was notably better and is probably the best sounding 85a2 I've heard, so I'd advise you to try and get some :)
Marco.
Hi. Yes just recived some mullard 85a2 with vi
Code 3p3a. Is there a link to some Info about the code ?
I fitted the one I ordered today - certainly doesn't sound worse, I'll leave it in a few weeks and then swap back to get a better idea.
Thanks.
Richard.
In the S4 if you change an 85a2 the amp needs rebiasing
Steve
Hi Marco,
your valve experience is required mate. Apart from the Mullard valve 85A2 did you find any others that were particularly good in the voltage reg stage of the Croft?
Only just seen this post, Jim! If you'd like my advice like this in future, just PM me, as these days I simply don't have time to read everything that's posted here :)
Anyway, the answer is yes - this:
English Electric ones from Colomor Valves:
http://imagizer.imageshack.us/v2/1024x768q90/923/S3i1HT.jpg (https://imageshack.com/i/pnS3i1HTj)
Details here (89 more available, so plenty in stock): http://www.ebay.co.uk/itm/370791865665?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Turns out this company has some history and were taken over by GEC in 1968, see here: http://www.radiomuseum.org/dsp_hersteller_detail.cfm?Company_id=8417 The valves themselves are fully NOS, and come beautifully packaged in their original boxes. I suspect that they're 1970s vintage.
Anyway, how do they sound? In a word: wonderful!
In comparison with the NOS Sylvania CV449 I was using beforehand, the English Electric produced a notably more open and 'liquid' midrange, with gorgeous tonal textures and increased detail retrieval. Furthermore, the soundstage/imaging of the Croft seems to have become even more 'widescreen' than before, with music, and particular female vocals, now enveloped in a 'cavernous chasm of clarity', thus increasing their 'intimacy' and believability accordingly.
Honestly, for £6 this is an instantaneous quick, cheap, and very effective tweak for all Croft preamps featuring the use of this particular voltage regulator valve. Highly recommended! :cool:
Marco.
Only just seen this post, Jim! If you'd like my advice like this in future, just PM me, as these days I simply don't have time to read everything that's posted here :)
Anyway, the answer is yes - this:
English Electric ones from Colomor Valves:
http://imagizer.imageshack.us/v2/1024x768q90/923/S3i1HT.jpg (https://imageshack.com/i/pnS3i1HTj)
Details here (89 more available, so plenty in stock): http://www.ebay.co.uk/itm/370791865665?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Turns out this company has some history and were taken over by GEC in 1968, see here: http://www.radiomuseum.org/dsp_hersteller_detail.cfm?Company_id=8417 The valves themselves are fully NOS, and come beautifully packaged in their original boxes. I suspect that they're 1970s vintage.
Anyway, how do they sound? In a word: wonderful!
In comparison with the NOS Sylvania CV449 I was using beforehand, the English Electric produced a notably more open and 'liquid' midrange, with gorgeous tonal textures and increased detail retrieval. Furthermore, the soundstage/imaging of the Croft seems to have become even more 'widescreen' than before, with music, and particular female vocals, now enveloped in a 'cavernous chasm of clarity', thus increasing their 'intimacy' and believability accordingly.
Honestly, for £6 this is an instantaneous quick, cheap, and very effective tweak for all Croft preamps featuring the use of this particular voltage regulator valve. Highly recommended! :cool:
Marco.
Cheers Marco, I will have a look if I have one of those as Glenn kindly sent me a bag of 85A2 valves to try so there maybe one in there. So far I have tried a Mullard and a Siemans which were both excellent.:cool:
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