View Full Version : Fun With Valve Amps
I've had three old valve amps stored in my garage for too many years now and thought it was time to warm them up indoors, check them out and fire them up in my normal system. I am raising funds for another hi-fi upgrade so they will reluctantly be sold off, another reason to enjoy what they can do one more time and say goodbye to some old friends.
First up: a Rogers Cadet III. I bought it back in the early 1990s and fully rebuilt it. This tiny thing, with its four Mazda ECL86 valves and 8W per channel, looks positively terrified when presented with my system. Even the speaker cables dwarf it! I plugged it in to the Power Plant Premier somewhat anxiously, checked that I was getting hiss in each channel and put some music on, not expecting much. Wow!
That liquid midrange coupled with more bass than it has any right to produce. Lovely, slightly dark, soundstage and really very good sound within its low power envelope. Saying that, it goes louder than I expected. It's so good that I shall just enjoy it for a couple of days before putting it up for sale.
I must admit to grinning while listening to the sound it's making. It just looks so ridiculously small and inadequate, yet it must represent the biggest giant-killer of all three. This would make the ultimate amp in a small room or on the end of a computer setup.
http://www.mtc.me.uk/images/Rogers_Cadet.jpg
Does it work without a rectifier valve?
Agree with your sentiments: there are still a lot of 'sleepers' out there. Vintage amplifiers of modest power running into efficient speakers can sound excellent.
For several years I ran a pair of home-made Mullard 5-10 amps into a pair of Wharfedale RS8DD drivers mounted in a (Wharfedale designed) distributed rear port cabinet, of around 1.5cu ft. in size. I'm sure if I still had this system today I would still enjoy it.
What are the other two valve amps you are resurecting Martin?
Regards
...or even Martin? :lol:
The Cadet uses a couple of solid state rectifiers as far as I can remember. That empty looking valve socket is for the umbilical cable to the matching preamp, which I do not have.
The next two amps to be resurrected are a Leak Stereo 20 and Croft Series 4S.
I love my Cadet 11 and wouldn't part with it, no valve rectifiers in these
Opps! Mea culpa Martin!
A friend of mine had an integrated Rogers Cadet and I thought it used an EZ80 rectifier, but obviously not.
Regards
I've just remembered: I also have an ultra-rare Croft SIP preamp with MC phono stage. This from the man who doesn't believe in MC cartridges!
Hi Martin,
Most interesting! So how does it feel to have some thermionic lurveliness for a bit in your staunchly 'sand-boy' system? ;)
It's amazing, isn't it, just how good little valve amps can sound? It also shows that your big Ushers must be quite a forgiving load, which is a good thing in my book...
Looking forward to what you think of the Stereo 20 and the Croft! :cool:
Marco.
Hi Marco
It certainly makes a change and it's always good to readjust any latent bias one may have accumulated over the years. The little Rogers punches way above its weight. However, we'll have to wait for the Leak in order to restore full dynamics and fill in maximum midrange detail, I think.
Nice one, Martin. Look forward to reading your impressions on the other amps. So what's the hi-fi upgrade you're saving up for - an SR7, or something even more 'exotic'? :)
Marco.
jandl100
09-02-2012, 08:03
...The next two amps to be resurrected are a Leak Stereo 20 and Croft Series 4S.
Ah, that brings back memories :wheniwasaboy:
... a Croft 4SA was my very first valve amp. £600 that was, used from a sadly now defunct dealer in Surrey about 25 years ago. Luvvly jubbly!
That dealer ... Tony Long was his name, I think ... wife called Rosa ... anyone recall them? Was a dealer for John Jeffries for a while, til he seriously pissed them off! Just off the south section of the M25 ... :scratch:
So what's the hi-fi upgrade you're saving up for - an SR7, or something even more 'exotic'? :)
http://theartofsound.net/forum/showpost.php?p=292931&postcount=23 :)
The Rogers is up for sale here http://theartofsound.net/forum/showthread.php?p=294380#post294380
Tonight: the Leak Stereo 20.
The Rogers is up for sale here http://theartofsound.net/forum/showthread.php?p=294380#post294380
Tonight: the Leak Stereo 20.
That has to be a bargain! I would be lynched if I bit, but I'm sure it will be snapped up, Martin. (I guess delivery to Scalford would also be an option, if people can wait until then and can't collect?)
Tonight: the Leak Stereo 20.
Oooh, you know how to build up the tension, doncha? I guess it'll give you something to do during the forum downtime... :eyebrows:
:popcorn: :popcorn:
Good luck with selling the Rogers - it's a bloody bargain and ripe for some judicious tweakage!
Marco.
It's a real plunge in the dark, Marco, as none of them have been fired up in years. That's why I'm doing a real system test on each one, as well as to have a final nostalgic listen. At least I can sell them with hand on heart as to their condition, and enjoy the fact that AoS members will give them a good home :)
Just watch that none of them blow up your speakers! I presume that you're testing them first, electrically, before firing them up in your system? :)
Marco.
Yes, don't worry. One nice thing about valve amps with output trannies is that there is a level of isolation and it's difficult for most faults to blow speakers.
So next, my revered Leak Stereo 20. It's been rather neglected for many years (the last time I actually used it as part of my system was back in 1993) and looks a bit tatty.
It's also quite non-standard as you can see: I replaced the two electrolytic reservoirs with large RATA SPX003 32uF + 32uF polypropylene caps and the GZ34 rectifier valve with a RATA fast solid state rectifier (this is easily changed back if required), giving it incredible speed and dynamics. The circuit is modified according to a Hi-Fi World article: it involves essentially changing the biasing of the phase splitter stage to allow direct coupling from the primary stage, reducing gain (a blessing) and fitting the more linear ECC82 valve for the original ECC83 type. I also added resistors to isolate the transformer windings from the output valve screens.
Powering it up took a while to settle down, the caps obviously groaning at having charge across them for the first time in some 18 years. Once I left it on for a couple of hours things settled down to some hiss and some low level hum.
As for the sound, I will say it again for anyone who believes that I am a total sand-head: the Stereo 20 has the best midrange of any amplifier I've ever heard. It simply soars, it's liquid, detailed and makes female voice sound extraordinary. Bass is strong, textured, deep and more powerful than the Rogers and treble is sweetly extended and ultimately a touch rolled off. Respect for those transformers, they were superbly well designed. If I had to return to valves I could very easily live with this amp, something I could never say about Quad IIs or even the Radford STA25 (which I also had in my system for a while). I think EL84s have a lot to do with it. This was the pinnacle of valve design in its heyday and it sounds bang up to date now.
I'm really going to miss it.
http://www.mtc.me.uk/images/Leak_Stereo_20.jpg
This is how it looked back in 1993, somewhat cleaner:
http://www.mtc.me.uk/images/Leakstereo20.jpg
Why didn't you clean it then before you took the picture, daftee? :D
Marco.
It's for that authentic well used effect...
Ali Tait
10-02-2012, 19:33
How much are you looking for Martin?
selfaddict
10-02-2012, 20:31
If Ali will pass the opportunity to buy, could I get a PM from you re price. This could be a good amp with my new Decca London ribbon tweeters :scratch:.
Will do, Juha. Ali and I are still in discussions.
Why didn't you clean it then before you took the picture, daftee? :D
Marco.
That's magic audiophile dust Marco,the buyer can bag it and sell it.
All my best equipment seems to produce a thin layer on top.
It seems to create a force field that majicly adds warmth to the music.:cool:
jandl100
11-02-2012, 08:35
Curious, I thought this was a hifi discussion sub-forum not the classifieds. :scratch:
;)
Dingdong
11-02-2012, 08:38
Curious, I thought this was a hifi discussion sub-forum not the classifieds. :scratch:
;)
Forum leaders privileges Jerry;)
It wasn't my intention to discuss sales here, just natural thread drift. I'll comment more on the Leak's sound later, suffice to say that I had a ball listening to it last night. The quality and power of the midrange on everything I played is immense. There has to be something in the circuit or choice of EL84s that does that - I've never heard a 6550 or EL34 amp quite reach that level of presentation.
jandl100
11-02-2012, 09:31
I'll comment more on the Leak's sound later, suffice to say that I had a ball listening to it last night. The quality and power of the midrange on everything I played is immense. There has to be something in the circuit or choice of EL84s that does that - I've never heard a 6550 or EL34 amp quite reach that level of presentation.
Yep, as myself and Marco commented on another recent thread, the little Leak ST20 really shows up most el34 amps as being a bit drab and lacklustre.
Why are you so keen to move these lovely valve amps on? - why not keep the Leak as a valid and interesting occasional alternative to your big sandy monster?! ;)
LOL - I Shall think of the Chord as a Big Sandy Monster from now on :)
I'm raising funds for another BSM, a PS Audio P10 regenerator, so I'm in 'everything must go' mode.
jandl100
11-02-2012, 10:40
Aha - yup, I understand completely. :)
I must confess that I am very fond of my own BSM. :D
I've removed the valves and given the Leak a bit of a clean. It's not exactly detailed, but presentable. The photo in post #18 has been replaced, thus satisfying Marco's need for personal cleanliness at all times ;)
I've also found a full set of replacement valves, including a Mullard GZ34 to revert the ss rectification to valve if necessary. Personally I've always preferred the RATA fast rectifier but I know some purists would disagree with me.
I just put some k d lang on and you would think that the Leak was designed for her voice. Talk about soaring as if without limits :eek:
I must confess that I am very fond of my own BSM. :D
If my Chord ever went bang for any reason, your Parasound would be getting some serious interest from me as the first amp to try out in my system.
I've removed the valves and given the Leak a bit of a clean. It's not exactly detailed, but presentable. The photo in post #18 has been replaced, thus satisfying Marco's need for personal cleanliness at all times ;)
Lol - much better! It now looks even more desirable as a potential purchase for someone :)
Btw, have you tried using it again in your current system, with the GZ34, or are you basing your opinion on what you heard when you originally did the comparison with the solid-state rectifier?
Much will depend on the Leak's circuit, but I can tell you that when I've done the same thing with the Copper amp, the GZ34s ate the SS rectifier alive to the extent that the amp was hobbled sonically beyond use!
However, I'm not saying that the same will happen with the Leak, as clearly there are other variables to consider.
Also, after having now listened to the Leak over an extensive period, can you hear it doing anything which your Chord isn't capable of, or perhaps doesn't achieve to the same degree?
Marco.
anthonyTD
11-02-2012, 11:47
HI Martin,
only just read this, yes, the little rogers amps are great fun, and as you have re-discovered they do indeed impress for their size, some points to add about the 3's non rectifier valve set, they used a voltage doubler circuit with solid state diodes to get the HT voltage, [very unusual as they could just have had a higher voltage winding wound on the secondary and used two or four diodes in the conventional way, but for what ever reason, this is how they did it.
Anyway, good to see that you have had some fun and a bit of a re-awakening so to speak.
Good luck to the next owners.
Anthony.
Hey Anthony, as a valve expert do you agree with my feelings about EL84s? Do you use them at all in your designs? There is something about the Leak which is simply magical.
Indeed, Anthony. It's funny that Martin prefers the SS rectifier, and as when we tried one in the Copper amp, it was notably worse...
Any thoughts as to why that may be the case, technically (as you know both the Leak and Copper amp intimately), other than simply a difference of personal tatste? :)
Marco.
Also, after having now listened to the Leak over an extensive period, can you hear it doing anything which your Chord isn't capable of, or perhaps doesn't achieve to the same degree?
I'll try the GZ34 out tonight.
Your question is tricky to answer as we are comparing a 20W valve amp from the 1960s with a 350W switched-mode MOSFET design from the early 2000s.
So - within the envelope of the Leak's performance - the Chord comes very close to emulating its midrange sonics but the Leak wins overall in liquidity, bringing forward detail and sheer beauty with female voice. It's not a big difference and I won't be throwing the Chord away as it wins hands down in sheer power and extension in the bass and lower-mid slam. In the extended treble they are similar. Outside of the Leak's envelope all bets are off, as the Chord can move air like no other I have tried, including a Linn Klimax.
Do you remember when we compared my Chord with your Copper amp? We concluded that the technologies are much closer than they are generally credited with sounding. I truly believe that a power amp completely responds to the way it is driven, and for me passive 'preamps' are out. It's my Pass preamp's sheer drive via balanced for the Chord or single-ended for the Leak that does it, not to mention good source quality.
The other thing to mention is that both Chord and Leak are powered from my Power Plant regenerator. High quality mains undoubtedly contributes to their high performance.
chris@panteg
11-02-2012, 12:19
Hey Anthony, as a valve expert do you agree with my feelings about EL84s? Do you use them at all in your designs? There is something about the Leak which is simply magical.
Hi Martin
I wondered if you knew that the Border Patrol PSU (choke input filter) apparently transforms the leak ? Not heard it but I did have a pair with my 2nd Audio's and have heard them with the AI 500 and 800 anniversary + Diavolo's , I suppose it's not something you want to do but having heard the BP I don't much care for SS rectifiers ! Expensive yes but once heard .
Nope - never heard a Border Patrol PSU but they do have a good reputation.
Hi Martin,
Interesting, and thanks for that. I'll comment more later. However, just to address this:
Do you remember when we compared my Chord with your Copper amp? We concluded that the technologies are much closer than they are generally credited with sounding.
Absolutely, and I remember it well. There wasn't a hill of beans in it between them, which surprised both of us.
It's my Pass preamp's sheer drive via balanced for the Chord or single-ended for the Leak that does it, not to mention good source quality.
However, you heard the Copper amp in conjunction with my Croft preamp; the Pass Labs had nothing to do with the superb results we obtained with my pre/power combo in your system - and that was before both have been significantly improved since.
In that respect, it would be interesting to do the comparison again... ;)
Marco.
chris@panteg
11-02-2012, 12:31
Nope - never heard a Border Patrol PSU but they do have a good reputation.
I still get to hear them as my m8 John still has his late 2nd audios , recently serviced with BP's only 15 watts but its still one hell of an amp :)
However, your heard the Copper amp in conjunction with my Croft preamp; the Pass Labs had nothing to do with the superb results we got with my pre/power combo in your system - and that was before both have been significantly improved since!
Yes, indeed, but the Croft is another world class preamp!
Ali Tait
11-02-2012, 12:41
Indeed, Anthony. It's funny that Martin prefers the SS rectifier, and as when we tried one in the Copper amp, it was notably worse...
Any thoughts as to why that may be the case, technically (as you know both the Leak and Copper amp intimately), other than simply a difference of personal tatste? :)
Marco.
Steve over on Audio-Talk, is in the process of re-housing his fantastic monoblock amps in some new chassis. He's been trying a few different things, including SS rectification in place of the valve setup he had. The conclusion was that there was no difference whatsoever. The thing with his amp is that it uses loads of regulation on the power supplies, and it seems to be this that makes the difference, or not in this case!
As is often said, an amp IS it's power supply, so skimping in this area will affect performance. The downside is it adds complexity and cost. Worth it though, from what I've heard of it.
The thread is here, if you read from where I've begun the link to the end, you'll see his conclusions -
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=3666&postdays=0&postorder=asc&start=285
Thanks for that, Ali. I'll have a read :)
It must depend on the circuit used then, as Anthony's Copper amps sound clearly worse with SS rectification - and by a big margin!
Perhaps Anthony would provide us with a possible explanation for this?
Marco.
anthonyTD
11-02-2012, 19:43
Hey Anthony, as a valve expert do you agree with my feelings about EL84s? Do you use them at all in your designs? There is something about the Leak which is simply magical.
Hi Martin,
i have indeed designed and built amplifiers using EL84's,in fact there is a rather ugly looking but seemingly very popular design still being sold of which the original circuit topology [not the casework] was in fact the brainchild of myself and another Colleague. Its a very sweet and sparkly sounding little valve and can be found in an abundance of equipment, i paticularly liked them in the original leek stereo 20, no, the amp wasnt perfect, but its one of those rare amplifiers from the day that can still sound modern when partnered with the right equipment.
As for solid state versus valve rectification, well, without going too much into it, i think one of the main reasons that one might be improved or made to sound worse with either technology is down to impedance, obviously a modern solid state diode is going to have a much lower impedance than any valve rectifier, so, if you take that into acount and its affect on the power supply, also, the impedance of the signal and output valves used then its no wonder one type might sound better in one paticular amplifier design, and seemingly worse in another.
Anthony,TD...
Hi Anthony,
Interesting, and I suspect you are right (regarding impedance), but I'm afraid that the technical explanation goes a little over my head in terms of its relevance as to why the Copper amp sounds much better with its stock GZ34s, than even your super-duper SS rectifier, which we tried... :scratch:
Marco.
anthonyTD
12-02-2012, 12:59
Hi Anthony,
Interesting, and I suspect you are right (regarding impedance), but I'm afraid that the technical explanation goes a little over my head in terms of its relevance as to why the Copper amp sounds much better with its stock GZ34s, than even your super-duper SS rectifier, which we tried... :scratch:
Marco.
Hi Marco,
one of the reasons i think the stereo 20 can seemingly be improved by removing the rectifier valve is down to the fact that the GZ34 takes an aditional 1.8 amps from the power transformer to light the heaters, once you remove this extra drag on the power supply by fitting solid state diodes, it can have the affect of the amp being able to produce dynamic range better with more deffinition etc.
Of course it all depends on how good the power supply was in the first place, hence my original brief explanation regarding impedances etc.
Hope this helps.
Anthony,TD...
Yup, I gets ya now, and I think you're right...The huge, high-quality, PSUs in the copper amps would just laugh at it! :)
Any thoughts on what Steve Shiels has experienced, in that respect (Ali referred to earlier), with his SE amp, which no doubt has as good a PSU as that used in the Copper amp?
Steve claimed that he heard no difference between SS and valve rectification, but I believe there was a valid reason for that.
Speaking from my own personal experience, the differences have always been very evident to my ears in any equipment I've used. And generally I've always much preferred valve rectification; the only exception was when Glenn changed the 6080 rectifier in my Croft for a MOSFET, which was undoubtedly a major sonic improvement.
However, I've always heard a difference between the two, and so am surprised why that wasn't the case with Steve?
Martin, have you tried using the GZ34 yet? I'd value your opinion on how that compares with the RATA :cool:
Marco.
I have now tried the GZ34 in the Stereo 20. Interestingly, there is precious little in it in the midrange: all of the Leak's wonderful soaring vocals are present and correct. However, the bass is a little woolly in comparison and I think Anthony is spot-on: the mains transfomer has the extra job of providing heater current to it in comparison with the ss rectifier.
Putting the RATA rectifier back in place, the bass tightens up and becomes more detailed again. Which tells me that the defining sound of the Stereo 20 is produced by the EL84s, not the power supply.
Once again, remember that I'm driving it from my Power Plant Premier. Dirty mains may change things around. I don't know and I don't care: no raw mains has touched my system for many years and it's going to stay that way :)
The Leak has now gone on sale here: http://theartofsound.net/forum/showthread.php?p=295628#post295628
Good price and I'm sure the new owner will love it :)
That "woolly bass" with GZ34 could also be a little of the "velvet glove" I referred to a while ago in the sonics. Can't wait to hear Dave's unit again.
Someone got a bargain
Certainly did! Thankfully it sold so quickly I didn't get the chance to get myself into trouble! :lol:
Dominic Harper
14-02-2012, 21:18
The Leak has now gone on sale here: http://theartofsound.net/forum/showthread.php?p=295628#post295628
Martin, I saw one of these on PFM a few months ago and they wanted £600, so whoever buys this are getting a bargain. I would have it for £350.00 if I had the funds. Good luck with the sale.
Natalie;)
Thanks, guys. It's gone to a good home. That last blast of k d lang through it was memorable. I don't know a better female voice and that was the best I've ever heard it.
Next amp: the Croft Series 4S power amp. It hasn't been fired up in more than 15 years and I'm going to give it a proper inspection before switch-on. It has enough welly to give me a fright if all does not go well :eek:
anthonyTD
14-02-2012, 22:27
Next amp: the Croft Series 4S power amp. It hasn't been fired up in more than 15 years and I'm going to give it a proper inspection before switch-on. It has enough welly to give me a fright if all does not go well :eek:
Hi Martin,
do you own a variac, if so or you have access to one, i would advise bringing it up gradualy, after being off for so long the power supply caps are likely to go with the fright of the full mains up it.:eek:
Anthony,TD...
I don't have acces to a variac any more, Anthony. Wish I did.
Anthony TD will have a fit, but the recommendations from "London Sound" were to switch on for a second, then off. back on for a couple of seconds, then off. Then five seconds, then ten etc etc..
I did the above with the crofted Quad II's, which hadn't been used for well over ten years, but I must admit the supply is tiny in comparison...
The Series 4SA will have more power than the Leak, but will it sound as good??? I found it to be a comfy classic pipe-n-slippers design after the EAR509's and I remember it being sold often with Pro-Ac Super-Towers which could spit viciously with any other amp...
anthonyTD
15-02-2012, 10:58
Anthony TD will have a fit, but the recommendations from "London Sound" were to switch on for a second, then off. back on for a couple of seconds, then off. Then five seconds, then ten etc etc..
I did the above with the crofted Quad II's, which hadn't been used for well over ten years, but I must admit the supply is tiny in comparison...
The Series 4SA will have more power than the Leak, but will it sound as good??? I found it to be a comfy classic pipe-n-slippers design after the EAR509's and I remember it being sold often with Pro-Ac Super-Towers which could spit viciously with any other amp...
HI Dave,
They must have ninja like reactions thinking they can beat the speed of electricity by switching things on and off.:lol:
Seriously, i would never recomend anyone do this, the only safe way is to bring the voltage up very gradualy, ie; 20, to 30 volt to start, leave it at that for a minuite or so, next 70 to 80 volts, and so on.
Power supply caps[electrolytics] present an almost dead short to the power supply when they have been left un-energised for any length of time, thats why they need to be brought back up gently to give them chance to re-form.
Hope this helps.
Anthony,TD...
anthonyTD
15-02-2012, 11:02
I don't have acces to a variac any more, Anthony. Wish I did.
Hi Martin,
if you can wait untill the show, bring the amp with you, and i will bring a Variac and we can power it up there.
Anthony,TD...
Now that's a good offer, Anthony. I can wait and it saves me scouting around for a variac to buy, which I don't really want. Thanks! :cheers:
The Croft 4S is on hold, then.
Next: my Croft SIP (Stereo Integrated Preamp) complete with the optional low output MC stage. Very rare!
anthonyTD
15-02-2012, 11:38
Now that's a good offer, Anthony. I can wait and it saves me scouting around for a variac to buy, which I don't really want. Thanks! :cheers:
The Croft 4S is on hold, then.
Next: my Croft SIP (Stereo Integrated Preamp) complete with the optional low output MC stage. Very rare!
Great,
just remind me closer to the show as my memory is not what it was these days.:)
Anthony,TD...
Aye, now you're 53! :eyebrows:
Marco.
anthonyTD
15-02-2012, 12:22
Aye, now you're 53! :eyebrows:
Marco.
83 IN THE MIND,
but whose mind, and who are you anyway:eek::eyebrows::lol:
A...
To be fair to Glenn, he does fuse his gear very well, so, should Martin be tempted to power the Series 4SA up in the meantime, wouldn't the fuses blow if the inrush was too high?????????
Actually, for those that tweak and bodge things bought on fleabay, a variac should be part of the tool-kit I reckon..
83 IN THE MIND,
but whose mind, and who are you anyway:eek::eyebrows::lol:
A...
S'ok, the nurse will be along with your tablets soon! :D
Marco.
Stop it Marco - I'm on seven tablets in the morning and three at night as it is, and I'm not much older than Anthony, if 53 is his true age :) As for a nurse giving it to me - chance would be a fine thing :(
Lol - he's 49, which is still ancient! :lol:
Marco.
t saves me scouting around for a variac to buy,
I have a variac if your passing my way on the A27
Thanks, guys. It's gone to a good home. That last blast of k d lang through it was memorable. I don't know a better female voice and that was the best I've ever heard it.
Thank you to Martin for the leak and the opportunity to have a chat and listen to a stonking system. I have yet to plug in the Leak (with or without the GZ34) but it will indeed be at home with a vintage system of Garrard 401 & Quad ESL57s. A few people have heard this amp and whilst giving it a bit of a clean I had a nose up the old girls skirt to find kimbercap polyprop? and blackgate electrolytics, I suspect it has a rather different (more modern & upfront) sound to a PIO equipped Leak. No idea what the resistors are.
Thanks again to Martin :-)
Hope it drives your '57s well, JP. Keep us informed.
I have a variac if your passing my way on the A27
Thanks for the offer, Jon. I'll keep that in mind.
Powered by vBulletin® Version 4.2.3 Copyright © 2026 vBulletin Solutions, Inc. All rights reserved.