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    New Dynaco ST-35 bias control upgrade kit from Dynakitparts, Mine expirence.....

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    Tazsmonn

    Posts: 18
    Join date: 2009-01-18
    Age: 52
    Location: Richfield (S. Minneapolis) Minnesota

    New Dynaco ST-35 bias control upgrade kit from Dynakitparts, Mine expirence.....

    Post by Tazsmonn on Sun May 31, 2009 7:08 pm

    I am lucky, I have a new ST35 & a rebuilt SCA35 (as power amp only). Both I have put in the ST35-BCU bias upgrade kit to & have done 3 additional critical changes. The Bias kit was constructed per instructions & I added the optional ground wire from the board for both amps. C1 was removed from both amps.

    ST35. I also added 22uF cap & a 1uF auricap after 50 ohm resistor. Replaced C4 & C5 with .47uF caps (5x original value, biggest I could fit in).

    SCA35. The power supply on this was already way over done, all sections are bypassed with 1uf auricaps & it is split into channel A & B right after the diodes. I replaced C4 & C5 with 1uF auricaps.

    Biasing, followed all setup instructions. I then turned on the amp & let set for 10 minutes. Set bias per instructions.
    Both amps were dead stable still a week later.
    ST35 32ma
    SCA35 34ma

    Sound after the above work done EXCELLENT! This is a term I seldom use. The amps were ok, but I have been around long enough & heard so many systems to know what was lacking. The high treble is now perfect in its delicacy. The deepest bass exists now with all the air. I found the sound staging much more focused & wider. The sound was all around clearer more enjoyable. What’s so interesting is just a few changes made a dramatic improvement in sound. I would highly suggest these mods to anyone owning ether amp.

    Go away, have fun!
    Tazsmonn
    05.31.09

    Tazsmonn

    Posts: 18
    Join date: 2009-01-18
    Age: 52
    Location: Richfield (S. Minneapolis) Minnesota

    Dynaco ST-35 bias control upgrade kit from Dynakitparts: in nonDynaco amp

    Post by Tazsmonn on Sat Feb 27, 2010 8:18 pm

    I will be writing a bit shortly on installing it in a non Dynaco amp, I have been rebuilding this winter. So look for it on the this Forum.

    shermanaudio

    Posts: 2
    Join date: 2011-01-18

    I just ordered an ST-35 Bias Kit

    Post by shermanaudio on Tue Jan 18, 2011 5:29 pm

    Hello.. I am brand new to this forum so hello to everyone. I just ordered an ST-35 bias kit from Dynakit and also some Dynapads.

    My ST-35 was rebuilt some 5 years ago and it was intermittently used. Now I have it as my daily amp with a PAS-3 (with the VTV upgrade kit a NOS Mallory FP, Si Diodes) and mated to some Focal 806V and fed by a Marantz BD-7004. Sounds amazing !

    My question is about the bias kit. I had never seen a Cathode Bypass cap in series with a 1K resistor. Does this resistor serve a purpose or is it needed because of the clever design on the variable Cathode Bias bias circuit?

    I always wanted to modify my ST-35 with four individual cathode resistors and bypass caps, this kit has been the answer to my prayers.

    Thanks,
    Rich

    tubes4hifi
    Admin

    Posts: 996
    Join date: 2008-11-30

    Re: New Dynaco ST-35 bias control upgrade kit from Dynakitparts, Mine expirence.....

    Post by tubes4hifi on Thu Jan 20, 2011 12:30 am

    the cathode bypass cap is NOT in series with a 1K resistor.
    There is a 1K resistor in series with a trimpot and in series with the 10 ohm bias measure resistor, and a bypass cap in PARALLEL with all of that. That is a normal bias setup
    for the DIYtube ST35 amp on which the Bias Kit for the Dyna ST35 was based on.

    shermana
    Guest

    Rev B Schematic

    Post by shermana on Thu Jan 20, 2011 5:42 pm

    Excellent! This is what I had concluded after scratching my head and trying to understand the schematic sent to me. I ordered the Bias Board and counting the days... Here's the diagram that confused me. I guess it will be corrected by Dynakit soon.

    shermanaudio

    Posts: 2
    Join date: 2011-01-18

    Re: New Dynaco ST-35 bias control upgrade kit from Dynakitparts, Mine expirence.....

    Post by shermanaudio on Mon Jan 31, 2011 4:41 pm

    I came back from a 1 week business trip and finally (anxiously) was able to install the ST-35 bias upgrade kit into my vintage ST-35 amplifier. Some 2 hours after I began the amp was ready. One nice thing I noticed was one weak EL-84 tube out of the four I had, so I swapped them out for a fresh new quad. Biased up at 0.35V (35ma) on each tube. Absolutely wonderful sound. Highly recommended upgrade. The kit also includes a filament resistor mod as well to provide a balanced resistive center tap to ground. The quality of the PC board is excellent. All of the parts are premium quality, the instruction manual is first class. The ST-35 now provides more inner detail to the music, and the overall sonics have noticeably improved, especially the Bass.

    Tazsmonn

    Posts: 18
    Join date: 2009-01-18
    Age: 52
    Location: Richfield (S. Minneapolis) Minnesota

    Re: New Dynaco ST-35 bias control upgrade kit from Dynakitparts, Mine expirence.....

    Post by Tazsmonn on Tue Apr 26, 2011 11:01 am

    As mentioned I wrote of putting The bias kit in a non dynakit amp. This posting can be found elsewhere on this forum.
    Tazsmonn
    04.27.11

      Current date/time is Wed Oct 22, 2014 4:36 pm