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a new life

12.73.68.193
Posted on October 6, 2009 at 20:21:30
Camrahnbay
Audiophile

Posts: 152
Location: DESERT SW
Joined: January 15, 2009



Brought these back from the junk pile!

RE: a new life, posted on October 7, 2009 at 14:08:20
xaudiomanx
Audiophile

Posts: 978
Joined: August 16, 2004
 Nice job! How do they sound?

RE: a new life, posted on October 7, 2009 at 18:08:45
Camrahnbay
Audiophile

Posts: 152
Location: DESERT SW
Joined: January 15, 2009
 Thanks,
I have different tubes now,they are the best R&R amps.
Great bass and detail,I have other amps but these are my favorites.
Left the original topology with new board,K40 caps and 2watt resistors.
Replaced selenium with diode and matched all the componants to the 9's.
They both hold a steady bias..1.56 and I am useing 7199 RCA blackplates,Mullard fat base GZ-34 and Golden Lion KT-88's.Stock value can caps.
LONG LIVE DYNACO

RE: a new life, posted on October 7, 2009 at 18:34:55
xaudiomanx
Audiophile

Posts: 978
Joined: August 16, 2004
 Let's face it. David Hafler was no idiot when it came to doing a lot with very little. The single most important issue with his input circuit was getting good 6AN8 and 7199 tubes. You might get better performance out of another board but then it isn't a Dynaco anymore.

On the downside, the input board was always the parts values and matching. I am not going to say when the amps were packaged for shipping or pre assembled at the factory that he didn't use good stuff. I will say that he used what was economically available to keep the price down and his profit margin where he wanted it.

If you really want to make the amp sing with greater speed, put the choke on the other side of the B+ where it goes to the inoput board only. In place of the choke put a 10 ohm resistor. If there is no hum leave it. If there is hum you might need another decoupling stage but it works. But again, it will not be a Dynaco.

Another thing you might want to not do is load the input board up with lots of capacitance. At the most, double of what's there but that's even a stretch. If you use too much capacitance then you affect the TC's(time constants). That is why a lot say that the bass is awesome or really dominating. If you like it that way then so be it. But even at that, it is not a Dynaco anymore.

Just my "0" cents worth.

Paul

RE: a new life, posted on October 11, 2009 at 20:50:53
strieb
Audiophile

Posts: 230
Location: Sendai, Miyagi
Joined: November 13, 2001
 Really nice work. And, I really appreciate your attitude in regards to your rebuild.
Sonic Lizard
RE: a new life, posted on October 7, 2009 at 19:02:09
Camrahnbay
Audiophile

Posts: 152
Location: DESERT SW
Joined: January 15, 2009
 OH,my mistake....I meant to say 6an8!I have a ST-70 also,first tube amp I rebuilt and really like it too.Different sound than the MK-111.
Yes,there is a point where there is so many modifications done that it is nothing like it was and to some it might be the cats meeow.
I have grown to like the original,vintage topology with as little as possible to bring them up to reliable units.
Tubes have always fasinated me and the love of music and commuication.
It's a hobby that was sleeping inside untill retirement.
Now music just fills the air through hundreds of tubes,most all vintage.
Great stuff!!!

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