801a amplifier

[Paul Barker]

Here is the data, showing as 3 watts but it’s two valves per channel, so 6 watts. Distortion profile showing less than 1/2 a percent.

[Nick]

Sitting here in dark as we still have no.electric. looked up the spec and had a penny drop moment. The phase of the windings is as you thought Paul from what is printed on the top. The problem was our lack of thinking. In the primary the end at b+ is in effect at ac ground. The other end on the driver anode is the end that moves with respect to ground. On the secondary it's swopped. The lower end (as drawn) is stationary wrt ground the top end is to the grid. So the primary and secondary were out of phase. Hence leakage inductance hence no treble.

[Paul Barker]

I’ll take youre analysis, thank you Nick.

Im going to see if I have any knickel laminations to fit these Hammond’s, possibly not , and they may have to parafeed, though perhaps with 15mA the Nickel lams will stand up to dc.

I haven’t! No repeatable sources either. I bought my Niclel lams on eBay, no longer available.

[Ray P]

Good stuff Paul, I can picture you with a nice big grin now...

[Paul Barker]

Good stuff Paul, I can picture you with a nice big grin now...

You know me well OB1

[Paul Barker]

Ray and I were togetherat VSAC was it in 2003? I know we all look a lot different, peoples films and stills of me at first eggborough show a much younger looking person without hardly any lines.

But I saw this character 18 years on showing really deep analytical sort of conscentration interest in all sorts of things. I knew when he came up to me and said hello Paul. I had to say, Im terribly sorry I just cant remember youre name? “ Its Ray” Oops.

There will be more moments like that I feel. But it really was great to talk to Ray as an old friend in person, these meets are invaluable.

Ray tried to communicate to me what hese doing digitally, but it was like trying to teach a cave man digital music reproduction. What Took from it was that Ray is using one bit digital at 5nn something or others which makes digital more analogue sounding. Keep going with it Ray, Ill be interested in the results, which maybe youll bring one day. Glad you came all that way.

Some of the things we experience at Owston are better than a lot of yanky stuff we heard at vsak, with the exception of Bruce Edgar. But for me Bottlehead Straight 8’s sadly being phased out, were great. Paul Joppa and Doc Bottlehead are very good at what they do, Doc and his Wife were so hospitable to us 3.

[Ray P]

No problem not remembering Paul, it's been a long time since we spent a few days at VSAC, yes it was in 2003 - we went with Clive and Scott neither of whom I've heard of/from for years.

I was telling you about my exploration of DSD (or more correctly SDM) playback, which is now my preferred way of listening to digital music - preferred to PCM that is. I normally play the SDM stream at 11MHz (=DSD256), which, in very simple terms, is 256 times the red book CD data rate. I prefer this playback because the music sounds more organic/analogue but without vinyl's shortcomings. It's kind of ironic that digital playback, at least for me, has moved away from the clamour for 'bit perfect' and now has lots of digital processing that I prefer the sound of.

I was planning to bring my playback system to Owston but didn't have time to get it ready to do so - it would have entailed bring the server, building a simple network, etc. and with my late arrival it wouldn't have been practical to have set-up and demo'ed it, and it would have further curtailed the time I had to speak with old friends. If at all possible I will bring it to the next Owston event, perhaps as part of a system.

Hopefully we won't have to wait as long until the next Owston.

Anyway, good to speak with you again and it'll be nice to hear your new amp working next time.

[Paul Barker]

Thanks for filling in the details, sounds like something I want too. But I’ve a long way up a steep learning curve, I only know about valves and transformers.

I’m having visual heaven at home I love this amp it’s rained these speakers it could tame anything. I just love the view. The excess choke input is enforcing the bass light speakers. The 100h of the Hammonds and the 50 Henry of the opts, allow that push through.

[IslandPink]

'Come home to a real amplifier'

[Paul Barker]

That’s what I’m talking about.

It’s quite different to anything SE dht that Ive built. The only reason I can think of is, the lack of 2nd harmonic distortion. Its kinda like listening to push pull directly heated triode. Until it gets into youre sole, youre listening for the usual SE dht inacuracy which endears SE to us. But there has developed a change in ball park in our gatherings, people independently bringing pretty linear amps with power far in excess of a valve SET, and folk having Mofo’s and stuff I dont even know what theyve got. All those amps are that good, you have to question yourself.

So does it do Eva Cassidy, yes, but it does her right, it doesent do her with give like an elastic band, it holds her linear, if it doesnt belong, its not there. Ill have to expand on what it does so well before this all sounds negative, because its not.


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With Barbaric


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I set the capacitor value by ear to provide whats lacking above 10khz in the pair of main drivers with the compression tweeter, just with the cap no LPad. By ear Id got it right. Barbaric played great bass in Steve’s house but home here on these speakers bass was lost, went down a rabbit hole. I first realised this that day at Steve’s house in Hull, one of those testing tracks they all were listening for a deep bass crescendo at the end of a track, was it on Jazz at the Pornshop anyone? I played it when I got home, listening for it on tentahoo,s, Nada, zilch! That I attributed to the speakers.

Now the speakers are at last being provided with the bass to reproduce. You know what theyre alright these speakers! The main drivers give a pretty good sounding faithful reproduction, maybe theyre less bass, but there is enough to satisfy, and its very strongly controlled by the new amp. Those who understand sedht talk, will know the control comes from choke input, the simplest form of regulated supply, and this amp is the most excessive choke input supply than youll ever hear. The Black Gates, one of there key features is in the bass, not as if enforcing it or elaborating on it. No,; allowing it and every gradation of tone and character, hidden by wham bam thankyou man capacitor banks, like you get in car audio for instance.

The top end is far reaching way beyond Barbaric, I’m going to have to Lpad the tweeters and/or reduce cap size further. Or to put that another way, nothing about the amp limits top end, so the crossover doesnt have to falsely raise top end.

So, is anything at all, not to my like? Im missing 2nd harmonic just a shred, but it sounds so great in every respect without searching for the homely 2nd harmonic character. It is not lacking real quality voicing of people or instruments whatsoever, its more in the league of these extremely well controlled massively powerful solid state amps were now hearing, and not to forget the mofo. But it does it better in a domestic setting. I mean, it won’t satisfy the crowd on the beech at Ibitha or HCTID. Thats when you need those solid state megawatt amps. But Id take this any day in my home.

There is no need to build another 212, or 833.

Cant wait to try this on Nicks Quasars, but I think that project is awaiting on outsiders, such as the acrylic workers, not helped by changes in which holes where and of what dimensions are required.

[Paul Barker]

So whats going to happen to poor Barbarick? who is sat in the dog house, sidelined by the new puppy.

Barbaric will undergo a refit to a interstage phase split Sukuma style 801a push pull amp. As the top end is lacking It’ll get the Sowter PP transformers I bought from Dr John.

Ive lost the phase split transformers I brought to Owston last time I brought an amp.

So I’d have to buy some and those arent made any longer.

Just looking at the topology of the PSE, if you made a Sukuma 801a


where its only pp at the output stage, a technique Stephie also uses, and I thought it worked well for me that time at Owston.

Transformers transformers transformers, everything waits for transformers, but Barbaric will undergo a refit! Its too cool to scrap.

Oh, and of course the same power supply that powers the Nightingale 801a PSE amp will power the “In direct Heating’s 801a Shadow” Barbaric.

[Mike H]

'Come home to a real amplifier'

[Paul Barker]

This amp is such a beauty, but I’m now on a mission to get rid of the cathode bypass caps on the output stage.

Someone linked a great teaching of JC M at European gatherings. In which he talks about triode as a diode bias.

I scoured my diode data sheets in Vade mechum and came up empty handed. Closest I could get to was two 5r4’s in series parallel but might not behave at such voltages as expected and would require a test bed first. So I started looking at triodes and found a closer triode to my needs in the double triode alone 5687. It’s not exact but close, so I using it I’d push more current but in doing so it would pull more voltage away from the output valves and probably balance up, the benefit being no capacitor sound influence (apart from valve capacitance, as JC stated) in my outlook a small trade off, you might not agree. I can hear my cathode bypass caps (Russian pio’s) They sound nice but they sound something.

Also from JC I took away resurrecting an old idea to build the Bates dc CF design (Radio & Television News) with se 6v6 triode connected cf. James quoted a miss concept from diy audio that a 1619 is a 6l6. It isn’t it’s a 6v6. With it’s full filament voltage the 1619 biases bang on same as a 6v6, the 6L6 is a countrymile out, no chance. Anyway 6v6 sounds great. Bruce Edgar demonstrated his speakers with CF output 6v6. Could have been a Bates. Sounded bloody marvellous.

I thought I’d build it as a cooking amp for everyday use. But I anticipate something special.

I’ll try 1619 on reduced filament voltage as Stephies’ done the legwork on that and the additional linearity is worthy. But my biasing may not tolerate it. Therefore, you know it, another test bed for that required too.

First iteration will be Bates values with standard 6v6.

I’ll make a test bed….. when I get a round tuit.

[Nick]

What size are the pio's on the cathode? I would expect they would introduce a bass cut.

[Paul Barker]

I did the math, 30 + 30 160v in parallel.

It has gorgeous bass, not like the 801a breadboard of nearly two decades ago. Now IT in correct phase as you know, it puts the leed instrument or singer to the space it belongs aswell. As such its brutally honest. Too honest for Eva Cassedy, who is actually let down I now know by the sound guys who probably did their meddling postumously. With a brutally honest amp there is no hiding. But on a good recording, thre is nothing to be worried about.

This amp has also taught me I would need a better dac. The Spifire DAC has now revealed its level. Its a lower level of quality than this amp deserves. But its a very good budget DAC (Burr Browned blah blah) for most amps.