300B Class A gorgeousness

[Firebottle]

I have a 300B amp in atm and to be frank it wasn't anything to write home about.
Very well proportioned output transformers but lack lustre bass and a thickening of the sound as the wick was turned up.

http://i66.tinypic.com/1z66ofn.jpg

Investigation revealed it to be a zero feedback design, now IMHO that exposes all the weaknesses of the active devices, not an approach I am keen on.
However with a small modification it transforms into a stellar performer. Gorgeous Class A clarity and with a really solid taut bass that you would hope for from generous output transformers.

I've not heard a 300B amp before but this one now is world class, sensational sound.

:)

[struth]

I have a 300B amp in atm and to be frank it wasn't anything to write home about.
Very well proportioned output transformers but lack lustre bass and a thickening of the sound as the wick was turned up.

http://i66.tinypic.com/1z66ofn.jpg

Investigation revealed it to be a zero feedback design, now IMHO that exposes all the weaknesses of the active devices, not an approach I am keen on.
However with a small modification it transforms into a stellar performer. Gorgeous Class A clarity and with a really solid taut bass that you would hope for from generous output transformers.

I've not heard a 300B amp before but this one now is world class, sensational sound.

:)

one of these for sale somewhere...i saw it recently....???:scratch:

[Edward]

Interesting

I assume you implemented some feedback? By how much and can you do it such that it is switchable between none and whatever value you chose?



§

[Firebottle]

Yes Edward, only about 4dB and it could easily be made switchable.

[YNWaN]

It’s an Audion - Silver Night perhaps? These are somewhat renowned for having reliability issues as I recall.

[Bigman80]

Well done Al, glad the mods have worked out.

[Firebottle]

It’s an Audion - Silver Night perhaps? These are somewhat renowned for having reliability issues as I recall.

Thanks for that heads up Mark.
I have noticed that two of the 3W rated anode loads are dissipating 2W.

[ERICLIMPIT]

It’s an Audion - Silver Night perhaps? These are somewhat renowned for having reliability issues as I recall.

The early Audions did have a few issues but the model here and later models were fine, and I think something of a bargain secondhand.

[anthonyTD]

Tend to agree with you on the feedback Alan,
All this purist stuff about zero feedback is as you say; often deteremental to the over-all performance that could be gained by using just what's needed, nothing more and certainly nothing less!
Feed back, when used correctly ie; not as a sticking plaster, but as a tool to make a good circuit great, is IMHO a no brainer, some of my earliar amps were/are fitted with adjustable feedback controls.
I have a 300B amp in atm and to be frank it wasn't anything to write home about.
Very well proportioned output transformers but lack lustre bass and a thickening of the sound as the wick was turned up.

http://i66.tinypic.com/1z66ofn.jpg

Investigation revealed it to be a zero feedback design, now IMHO that exposes all the weaknesses of the active devices, not an approach I am keen on.
However with a small modification it transforms into a stellar performer. Gorgeous Class A clarity and with a really solid taut bass that you would hope for from generous output transformers.

I've not heard a 300B amp before but this one now is world class, sensational sound.

:)

[AD Audio]

For me, you've missed the most vital piece of information which is: what speakers are you using to test this amp? To my ears, and many of my clients, 300b, 845, and 805 amps sound best with no feedback, in the right circuit and driving sensitive, easy load speakers. Of course, difficult loads or insensitive speakers can cause the whole sound to collapse, which is where feedback comes to the rescue.

I've built amps with variable and switchable feedback but, again, with the right speakers and amp circuit the sound always closes up when feedback is switched or dialled in.

Don't get me wrong: I'm not anti feedback and happily run Radfords, Lebens and others to drive my Tannoy Canterburys. It's just that the valves above in the right circuits sound best driving the right type of speakers with no feedback

[Bigman80]

Would be Quad ESL 57's at Alan's.
For me, you've missed the most vital piece of information which is: what speakers are you using to test this amp? To my ears, and many of my clients, 300b, 845, and 805 amps sound best with no feedback, in the right circuit and driving sensitive, easy load speakers. Of course, difficult loads or insensitive speakers can cause the whole sound to collapse, which is where feedback comes to the rescue.

I've built amps with variable and switchable feedback but, again, with the right speakers and amp circuit the sound always closes up when feedback is switched or dialled in.

Don't get me wrong: I'm not anti feedback and happily run Radfords, Lebens and others to drive my Tannoy Canterburys. It's just that the valves above in the right circuits sound best driving the right type of speakers with no feedback

[AD Audio]

Quad ESL57s sound absolutely gorgeous with my no feedback 300b amps which very happily drive them, so that for me, points at something up circuit-wise.......

[Bigman80]

Quad ESL57s sound absolutely gorgeous with my no feedback 300b amps which very happily drive them, so that for me, points at something up circuit-wise.......You may well be right. I can't comment, I haven't heard a 300b amp

[Firebottle]

Good to hear other viewpoints but in this instance it is far far better with a little bit of feedback in the circuit.
The circuit is very traditional, 3 common cathode stages with simple resistive anode loads on the first two.
However I have never been a fan of 6922 valves as I think there are far more linear valves to be had. With a small amount of feedback the sound is transformed.

Previously my low output OTL amp trounced the 300B, now they are on a par, extremely lucid with the 300B actually having a better bottom end.

[Primalsea]

I think a 300b amp with no feedback can sound amazing with some speakers but terrible with others. However, a 300b amp with feedback can sound amazing with some speakers but terrible with others.

Its the old chestnut of synergy, but not only that, also what music you listen to. Sometimes coloured, flawed sound is just the ticket but sometimes it just doesn’t work...

[anthonyTD]

It is of course possible to unite a zero feedback amp with a particular type of speaker" that will work exceptionally well with some music, and if that is all that you listen to, then fine, however; if you listen to real world music, from many genre's, and at real world level, then this type of amp, and speaker combination will undoubtedly almost always come up severely short in the listeners expectations.
I have heard many systems over the years that can’ and do indeed excel in certain aspects of chosen musical content, but if I Were asked could I personally live with that type of system, then the answer would be a firm no, as to do so, would probably render most of my music collection unplayable, but again, that’s just my personal view.

[WESTLOWER]

It is of course possible to unite a zero feedback amp with a particular type of speaker" that will work exceptionally well with some music, and if that is all that you listen to, then fine, however; if you listen to real world music, from many genre's, and at real world level, then this type of amp, and speaker combination will undoubtedly almost always come up severely short in the listeners expectations.
I have heard many systems over the years that can’ and do indeed excel in certain aspects of chosen musical content, but if I Were asked could I personally live with that type of system, then the answer would be a firm no, as to do so, would probably render most of my music collection unplayable, but again, that’s just my personal view.

I’ve had zero feedback amps on a few different sets of speakers and they performed wonderfully over a wide range of musical genres. Yes the pairings had to be considered but once put together they certainly wasn’t genre dependent.

[anthonyTD]

Good to hear! :)
I’ve had zero feedback amps on a few different sets of speakers and they performed wonderfully over a wide range of musical genres. Yes the pairings had to be considered but once put together they certainly wasn’t genre dependent.

[AD Audio]

It is of course possible to unite a zero feedback amp with a particular type of speaker" that will work exceptionally well with some music, and if that is all that you listen to, then fine, however; if you listen to real world music, from many genre's, and at real world level, then this type of amp, and speaker combination will undoubtedly almost always come up severely short in the listeners expectations.
I have heard many systems over the years that can’ and do indeed excel in certain aspects of chosen musical content, but if I Were asked could I personally live with that type of system, then the answer would be a firm no, as to do so, would probably render most of my music collection unplayable, but again, that’s just my personal view.

Unfortunately Anthony your personal view and blanket statement-then this type of amp, and speaker combination will undoubtedly almost always come up severely short in the listeners expectations-is not backed up by fact. My musical tastes range from choral through to dub with everything in between and I'm lucky enough to have a commercial zero feedback 845 amp in my studio-Mastersound 845 mono blocks driving Troels Gravesen speakers-along with a Leben CS1000 driving Tannoy Canterburys in the lounge. Both systems reproduce all types of music beautifully and would not be there if they didn't. This goes for my clients' systems using zero feedback amps too: they all listen to a wide variety of different styles and would not accept an amp that didn't excel with all styles full stop. The majority if not all of them moved from amps using feedback to zero feedback amps.

The speaker /amp match is important and there's many a tale on this Forum of folk changing speakers and ending up changing amps-the name Tannoy springs to mind-and my Mastersounds are not a good fit with my Tannoys but perform wonderfully with the Troels' speakers that are themselves a difficult load.

You are very welcome to stop by and have a listen if near London.

[anthonyTD]

Hi David,
First of all, thank you for your kind invitation, I have to admit, I dont get the need to visit London much these days, but you never know! :)
Now as I hinted in my earliar posts, when you get the combination of speaker and amp correct, something almost magical can happen, unfortunetly, where zero feedback designs are concerned, and this is all IMHO a lot of folk give up way before they get to that magical combination, also, as I am sure you understand, the type of output valves used, and their configuration play a huge part in how the amp reacts to the speakers varying load, and the difficulty of controling the speaker cone movement etc, this again IMHO is key to getting a zero feedback amp and speaker combination to work. I suspose its posible that I have become Biased and slightly Jaded over the years,from the systems I have heard, and therefore; witnessed first hand, how wrong you can get these type of systems, when proper care and attention hasnt been used to partner things correctly etc, which could indeed contribute to my feelings on Zero feedback designs, and for that I sincerely appologise. :)
Unfortunately Anthony your personal view and blanket statement-then this type of amp, and speaker combination will undoubtedly almost always come up severely short in the listeners expectations-is not backed up by fact. My musical tastes range from choral through to dub with everything in between and I'm lucky enough to have a commercial zero feedback 845 amp in my studio-Mastersound 845 mono blocks driving Troels Gravesen speakers-along with a Leben CS1000 driving Tannoy Canterburys in the lounge. Both systems reproduce all types of music beautifully and would not be there if they didn't. This goes for my clients' systems using zero feedback amps too: they all listen to a wide variety of different styles and would not accept an amp that didn't excel with all styles full stop. The majority if not all of them moved from amps using feedback to zero feedback amps.

The speaker /amp match is important and there's many a tale on this Forum of folk changing speakers and ending up changing amps-the name Tannoy springs to mind-and my Mastersounds are not a good fit with my Tannoys but perform wonderfully with the Troels' speakers that are themselves a difficult load.

You are very welcome to stop by and have a listen if near London.

[anthonyTD]

Perhaps you may find this an interesting read, it discusses in great detail, the use of 6922/6DJ8 for audio.http://tubeaudiostore.com/suitof6dfora.html

However I have never been a fan of 6922 valves as I think there are far more linear valves to be had...

[AD Audio]

Good to hear other viewpoints but in this instance it is far far better with a little bit of feedback in the circuit.
The circuit is very traditional, 3 common cathode stages with simple resistive anode loads on the first two.
However I have never been a fan of 6922 valves as I think there are far more linear valves to be had. With a small amount of feedback the sound is transformed.

Previously my low output OTL amp trounced the 300B, now they are on a par, extremely lucid with the 300B actually having a better bottom end.

So by introducing a small amount of feedback you've proved that the 6922s are probably not the issue. But if a small amount of feedback improves the bass to that extent and it's not the circuit I'd be putting the amp on the scope as it might be some instability when driving the Quads that the feedback cures

[Firebottle]

I am being picky when I say I am not a fan of the 6922. To say they were an issue would be incorrect.

My system is very revealing, the performance without feedback wasn't shabby but the bass response certainly was improved with the addition of the feedback.
This was apparent on the scope feeding dummy loads as well as heard on speakers, conventional and the Quads.

[Haselsh1]

Back around 1997 I owned a WAD 300B PP power amp with switchable feedback and for me it was always better with feedback switched in rather than out in terms of sound quality.

[Haselsh1]

Interesting, back in 2004 I had an Audion 300B SE integrated amp and paired it with Audio Note AZ-2's. For me personally the sound was incredibly good but after six months or so of listening I just found that the system really suited acoustic music more than prog rock. Bloody fab sound but I would really have needed two systems.

[WESTLOWER]

Back around 1997 I owned a WAD 300B PP power amp with switchable feedback and for me it was always better with feedback switched in rather than out in terms of sound quality.

Swings & roundabouts... Myself and Petrat of this parish also owned WAD 300pp power amps with switchable feedback and we both preferred, by quite a margin, with the feedback switched Off! The sound deteriorated with it on.

[WESTLOWER]

Interesting, back in 2004 I had an Audion 300B SE integrated amp and paired it with Audio Note AZ-2's. For me personally the sound was incredibly good but after six months or so of listening I just found that the system really suited acoustic music more than prog rock. Bloody fab sound but I would really have needed two systems.

Serves you right, That's what you get for listening to prog rock! :rofl: :rofl:

[Haselsh1]

Serves you right, That's what you get for listening to prog rock! :rofl: :rofl:

:thumbsup:

I remember selling my WAD 300B power amp back around 1999 - 2001 time to some guy who came and shoved it in the boot of his car. Really nice amplifier to be honest with the most amazing sense of space and air to the sound. Prior to that I was using a Musical Fidelity A100 which was much better suited to me but I was very grateful for the experience even though it was a bloody expensive experience. It started me on the valve journey that has led me to where I am now.