373 replies to this topic

[spritzer]

Who needs low distortion and high power? What about some high distortion, high noise and very limited power output. Apparently some people want that in an amp... This has been a long time coming but this one will bear a striking resemblance to certain production amps but combine dynamic and electrostatic output in one amp. More to come...

[swt61]

Uhmmm, OK.

[Torpedo]

[roadtonowhere08]

I guess this is the much talked about shit hitting fan amp thread, eh?

[kevin gilmore]

So here is how this went down.

Someone over there really pissed off Birgir.
Its not nice to piss off the head of the stax mafia.
I mean its REALLY NOT NICE to piss off the don of the stax mafia.
So pictures were acquired.

And reverse engineering proceeded. Starting at about 11am today.
Then by about 4pm the stax mafia had an epiphany.

And so while a slight bit more work is necessary...
http://gilmore.chem....ern.edu/a10.pdf

Now there is just so much wrong with this thing, i don't know where
to start. OH wait, i do.

http://gilmore.chem....raptorschem.jpg


So Ray says the A10 is SRPP. Well go and look up the article
written by Broskie... Its SRPP only when the load is resistive
and close to impedance of the cathode resistors. Which by
the way an electrostatic headphone definitely IS NOT.
As usual ray does not have a fucking clue.

Whats more the thing is completely open loop, and i just
finished testing about 50 x 5687's in the output circuit, and guess
what, a variance of about 4+ db. Reminds me of mikhail's
ES1/2 disaster... And the same goes for the input section.
What a piece of work.

But let that not stop Moljinor(sp) audio... Who will be releasing
a board that is both a B52 and a A10 at the same time.
Add much bigger output caps for the dynamic thing, and
put in a switch to lower the output section power supply voltage.

Cheap as hell.

Still the 5687 is being driven way over its cathode to filament specs,
just like mikhail's disaster...

By the way, just the output section of this thing has distortion specs
that rival the Darkstar, >5% at even 200 vpp.

And the power supply... What a clusterfuck. Not even worth the
time to key that one in.

Edited by kevin gilmore, 04 March 2012 - 06:39 PM.

[swt61]

"The Law Offices of Do We Cheatem & Howe"

Love this!

[cobra_kai]

While I appreciate the sentiment, this seems like a somewhat futile gesture. Are you planning to offer these for sale, in which case do you really expect anyone to buy one? On the other hand if you make it a DIY project with a board run it seems even less likely that anyone would build it.

Nevertheless,

Edited by cobra_kai, 04 March 2012 - 07:50 PM.

[Knuckledragger]

[wink]

The law offices of Sue Grabbit and Runne may get some business out of this debacle..

Lawyers at 50 paces..........

[grawk]

There's nothing they can be sued for, if they didn't copy the board layout, which obviously they didn't.

[roadtonowhere08]

Priceless!

[wink]

Grawk is right.

I'm waiting for someone to bring out an amp that has loads of distortion and everyone raves about it.........

Wait, ---- Marshal has already done that......

How about 95% to 99% distortion and eminently musical. Yeah, I know, Moog synthesiser.....

[wink]

http://www.hilarious...rk-mccoy-spock/

[HeadphoneAddict]

"The Law Offices of Do We Cheatem & Howe" might be "Dewey, Cheatem, and Howe". http://en.wikipedia...._Cheatem_&_Howe

[guzziguy]

"The Law Offices of Do We Cheatem & Howe"

Love this!

This is borrowed from Johnny Carson. Of course, he probably borrowed it from somebody else. I believe it should be written as "Dewey, Cheatum and Howe". That way, they are real last names. It would be great to find a real legal firm with that name.

[wink]

http://www.google.co...=1t:429,r:3,s:0

[kevin gilmore]

Fine, Dewey Cheatem and Howe it is. But later because i don't have the file at work.

[kevin gilmore]

Wait, ---- Marshal has already done that......

I'm going to disagree with this, i have measured many a marshall amplifier.
Unless you push them well into clipping, they typically measure .1 to .2% thd
across the audio band.

Besides which the job of the headphone amp is to accurately reproduce the
distortions in the recorded sound. With something like a synthesizer, this
is not as easy as it sounds due to rise and fall times that exceed what
any musical instrument can do.

[spritzer]

Sorry for leaving you hanging like that but work called. Thanks Kevin for stepping in and stating rightly that it isn't wise to fuck with the Mafia. We've always known that the A-10 was bad but it is shocking just how bad is is. Ray states a voltage swing 600VP-P (roughly 210V RMS) which is just barely meets while generating way too much distortion so it is clearly clipping at that point. To put this into context the BHSE swings 1500VP-P (530VRMS) and it costs a lot less than the A-10. Hell,the SRM-252S swings 280VRMS and never comes close to clipping... hen we have the issue with no adjustments at all in the amp. Ray states on the top panel that you need matched ECC83's for the diff amp and 6SN7's for the preamp output but this will never work to balance out the amp properly. The diff amp has to be adjusted and ditto the phase splitter. There is also no offset adjustment so that 600VP-P voltage swing is purely theoretical. The amp will never reach that in practice...

To make matters worse these are not enough amplification stages so the gain is driven to the max with bypass caps on the cathodes so this thing is noise central. Massive amount of gain with no voltage swing is never a good idea. Then we have the over all layout of the amp, it's just a mess with stuff run all over the place, it's like auto routing gone mad.

As for the PSU, it is pure shit but Ray was clearly looking at Mikhail for inspiration there. Two bias lines run from the PSU to the headphones when a simple voltage divider in the amp chassis would have done a far better job. Mikhail did the same in the ES-1/2 wasting "precious" umbilical wires on nothing. Then we have the Cincon CMF40/60 switching PSU's used to run all the low voltage stuff from relays to the tube heaters. Grounding the heaters in the 5687 is a shockingly bad idea same as it was in the ES-1/2. Now the real question is, should I leave the circuit as it is or apply fixes so that it at least sort of works. Isolated heaters are a no brainer but I really want people to appreciate just how bad this amp is.

[n_maher]

While I understand the element of hilarity I'm not sure I get the overall point of this exercise. Why produce something that sucks? Why waste the time? Is it to spite Ray or something else overthere that likes the two products you're spoofing? I thought we (meaning the HC community at large) had kind of moved beyond giving a shit about most of this?