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Pete Millett's Menace - Page 2

post #16 of 110
Quote:
Originally Posted by ericj View Post
And yeah, I'm building an amp with a 6080 too, but mostly just out of curiosity.
In general, I think that if tubes are in the amp, that transformer coupling is a good plan. The lower the impedance of the transformer, all other things being equal, the better it will perform. The 6080 has such a low rp that you can use a low impedance transformer. So, it could be used to good effect in that regard. Though at that point, I'd use a 45 or a 2A3
post #17 of 110
Quote:
Originally Posted by dsavitsk View Post
In general, I think that if tubes are in the amp, that transformer coupling is a good plan. The lower the impedance of the transformer, all other things being equal, the better it will perform. The 6080 has such a low rp that you can use a low impedance transformer. So, it could be used to good effect in that regard. Though at that point, I'd use a 45 or a 2A3
Transformer coupling is wonderful. But wonderful transformers are expensive...

Pete
post #18 of 110
Quote:
Originally Posted by pmillett View Post
Transformer coupling is wonderful. But wonderful transformers are expensive...

Pete
Not to mention, what impedance should the transformer secondary have? A man with four pair of good headphones could have one with 24-ohm impedance (a denon for example) and one with 600-ohm impedance, and another at 200 ohms and another at 400 ohms . . . .
post #19 of 110
very nice work nate. i like the layout a lot, and cant wait to see the inner-bits of the amp.
post #20 of 110
Quote:
Originally Posted by pmillett View Post
Transformer coupling is wonderful. But wonderful transformers are expensive...
Yeah, I guess, but compared to a 50lb power supply? For the money people spend on amps around here, a $100, or even $200 pair of OPTs isn't really that bad. And, even a $40 pair of power toroids can do wonderful things.

Quote:
Originally Posted by ericj View Post
Not to mention, what impedance should the transformer secondary have? A man with four pair of good headphones could have one with 24-ohm impedance (a denon for example) and one with 600-ohm impedance, and another at 200 ohms and another at 400 ohms . . . .
Sowter has a good solution for this. They use 4 equal secondaries that can be combined in various parallel and series connections for multiple impedances. You can also just push them up higher so long as the induction is sufficient -- it usually is with parafeed. So long as gain is sufficient, you end up with lower distortion this way.

Anyhow, I apologize for derailing the thread, so I'll leave it alone.
post #21 of 110
Quote:
They use 4 equal secondaries that can be combined in various parallel and series connections for multiple impedances.
Hmmm..... hadn't thought of that way to get impedance/load matching. Very Nice. ;-)
post #22 of 110
Thread Starter 
Quote:
Originally Posted by dsavitsk View Post
Yeah, I guess, but compared to a 50lb power supply?
Well, the problem is that it's kind of hard to eliminate the 50lb beast if you want to be able to run the amp at the current levels that I did and keep it tube rectified. The B+ needed to supply almost .4A of current at ~300V and there are three different heater supplies: 5V for the rectifiers, 6.3V for the input and 6.3V @10A for the output tubes.

Quote:
Anyhow, I apologize for derailing the thread, so I'll leave it alone.
Actually, I think that the discussion is great. The design is a platform, not a directive so exploring options are a welcome addition. At one point I was actually considering a transformer coupled version but decided to stick w/ my original plan of a hot-rodded HA-2. I can't wait to hear Pete's new TTVJ trafo coupled design at CanJam.

Quote:
Originally Posted by nikongod View Post
very nice work nate. i like the layout a lot, and cant wait to see the inner-bits of the amp.
Thanks Ari, the layout was largely dictated by function, not form ironically enough. The PS layout is darn near a schematic in the way that it's put together. For the amp I knew certain things, like wanting to keep the heater wiring as far away from the signal path as possible, so I chose to have the heater wiring come into the chassis on the opposite side of the rear panel. For the amp I also went as far as doing CAD drawings of the layout and a wiring diagram to try and head off any potential problems. Those efforts paid huge dividends in the form of much less thought having to go into the wiring when I got down to business. And in truth the circuit is pretty straight forward and simple (low parts count) compared to a lot of the SS stuff that I've worked on.
post #23 of 110
Quote:
Originally Posted by n_maher View Post
Well, the problem is that it's kind of hard to eliminate the 50lb beast if you want to be able to run the amp at the current levels that I did and keep it tube rectified. The B+ needed to supply almost .4A of current at ~300V and there are three different heater supplies: 5V for the rectifiers, 6.3V for the input and 6.3V @10A for the output tubes.
eh? 10 amps? 2.5 amps per 6080 iirc.
post #24 of 110
Do not understand any of the technical stuff! But if the amp sounds half as good as it looks it will be a killer. Nice work!
post #25 of 110
Thread Starter 
Quote:
Originally Posted by ericj View Post
eh? 10 amps? 2.5 amps per 6080 iirc.
I thought that I'd mentioned before but I just looked and I didn't - the amp was designed to be able to run at least 7 output tube options: 6AS7, 6080, 5998, 7236, 6528, 6336, 421A and I'm sure many others that I haven't found yet. The heater requirements range from a low of 2.4A (per tube) all the way up to 5A. I'm working through all the substitutes listed in Duncan's TDSL but for the 6080 alone there are more than 10 alternative tubes listed so I'm sure my wallet will give up long before I run out of tubes to try.
post #26 of 110
Quote:
Originally Posted by n_maher View Post
Actually, I think that the discussion is great.
Okay, then I'll say more


Quote:
Originally Posted by n_maher View Post
Well, the problem is that it's kind of hard to eliminate the 50lb beast if you want to be able to run the amp at the current levels that I did and keep it tube rectified. The B+ needed to supply almost .4A of current at ~300V and there are three different heater supplies: 5V for the rectifiers, 6.3V for the input and 6.3V @10A for the output tubes.
So, I guess the point I was trying to make is that there are 2 main ways to lower the output impedance (assuming no solid state buffers). One is to use brute force -- a stack of cathode followers, or something similar -- the other is to use impedance matching via a transformer. With the transformer, you wouldn't need the huge volume of tubes, and thus would save the expense of a huge power supply. A single 6H30 will power almost any phones to extreme volumes, for example.

Quote:
Originally Posted by n_maher View Post
I can't wait to hear Pete's new TTVJ trafo coupled design at CanJam.
I didn't know such a thing existed. I'm curious to see how Pete designed it.
post #27 of 110
Quote:
Originally Posted by n_maher View Post
I can't wait to hear Pete's new TTVJ trafo coupled design at CanJam.
Is it this one? TTVJ Millett 307A Headphone Amplifier [TTVJ Millett 307A] - $5,995.00 : TTVJ, Todd The Vinyl Junkie

That would explain why everyone is sold out of 307A's right now. It took me forever to track some down recently.
post #28 of 110
Thread Starter 
Quote:
Originally Posted by dsavitsk View Post
Okay, then I'll say more
Please do, as I said I'm no designer and contributed very little to this project from a design perspective. About all I designed was the heater biasing setup, which is really nothing more than a series of voltage dividers. I was rather happy that it actually worked.

Quote:
I didn't know such a thing existed. I'm curious to see how Pete designed it.
The TTVJ Millett 307A Headphone Amp.
post #29 of 110
Quote:
Originally Posted by dsavitsk View Post
Is it this one? TTVJ Millett 307A Headphone Amplifier [TTVJ Millett 307A] - $5,995.00 : TTVJ, Todd The Vinyl Junkie

That would explain why everyone is sold out of 307A's right now. It took me forever to track some down recently.
wow!

that amp looks pretty cool. 6K though.
post #30 of 110
I like OTL amps. pete's comment on good transformers having a good price is very true, but i agree with davistk's point of transformers doing cool things.

i still think the amp looks pimp, and if nate REALLY wants transformers they can always be run parafeed in a their own little case like moth used to do. its a nice project for a rainy day.
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