ST-35 First Build

[milsman2]

After careful thought and planning and deciding which kit to get between the K-12G, K-502 or two K-501's...I decided to get none of them and simply get the ST-35, but I am unsure whether to get

DIYTube Dynaco ST35 Tube DIY Amp Kit Great for iPod

or

Product Detail: ST-35 KIT (120 VAC)

Just pick one and I'm ordering

[Bob01605]

Originally Posted by milsman2

After careful thought and planning and deciding which kit to get between the K-12G, K-502 or two K-501's...I decided to get none of them and simply get the ST-35, but I am unsure whether to get

DIYTube Dynaco ST35 Tube DIY Amp Kit Great for iPod

or

Product Detail: ST-35 KIT (120 VAC)

Just pick one and I'm ordering

Both the Triode Electronics and the Dynakitparts ST-35's will probabaly sound about the same. Since the Dynakitparts ST-35 is a replica of the original Dynaco ST-35, I am betting it would be worth more once built should you ever decide to sell the amp in the future. Another thing to consider is that the Dynakitparts version is physically smaller and would take up less space.

Bob Latino

[john dozier]

I have dealt with Triode for many years and find them to be a very reputable company. They know their stuff. The ST35 was thought by many to be the best sounding Dyna, especially when used as a tweeter amp. It is a bit low powered for full range use IMHO. I know nothing about the new Dynakits. I do know the transformer is the heart of any tube amp and in that area, Triode is very experienced. BTW I use Antique Sound Lab Monsoons and have completely rebuilt Fisher 50a's, so I am not a tube novice. Whichever way you go, I would replace the input stage coupling caps with Solen Teflon and foils, the single best improvement you can make to either of these amps. Expensive and darn well worth it. Regards Dr. John Dozier

[milsman2]

I just ordered from Dynakit. I was kind of up in the air about it then called Dynakit to ask a really quick question and he was incredibly knowledgeable and very helpful with talking me through a number of points. It's on the way (Along with EL84's and JJ ECC832 /
12DW7's)!

[merlin2069er]

Check out Shannon's board...

diytube.com :: Index

I'm sure he still sells board & plenty of support on his bulletin board.

[rknize]

You'll also be able to use a used or one of the reproduction chassis covers for the Dynakit version.

[rmyauck]

Shannon's board is the one used in Triode's ST-35 version.

Go to Bob Latino's form for some more info on modding the ST-35 a bit with a choke and input cap removal etc.

http://dynacotubeaudio.forumotion.co...wer-amp-photos

One mod well liked is to add fixed bias. There are two ways:

Dave Gillespies's EFB mod for fixed bias with a neg voltage regulator. Lot's of info on the diytube site.

http://tronola.com/A_New_Look_At_An_Old_Friend.pdf

http://www.tronola.com/html/efb_in_a_dynaco_st-35.html

Daynakit also has a fixed bias kit for adjusting each output tube. It's a board for $65 which mounts on the top of the amp.

http://www.dynakitparts.com/store/product.aspx?id=293

Can a volume control be added or is it best to get a preamp? I noticed that on my Eico HF-12 bypassing the preamp section with a portable CD player plugged into the amp input through it's RCA didn't sound very good.

Have fun!

[milsman2]

One of the reasons I bought this kit was it's stability and performance without mods, so with that in mind I'm going to build it stock and plug in the iPod and let 'er rip for now. I'll post pics and let you know how it goes after that then move on to mods.

[rhing]

I got a good deal on a used original Dynakit Stereo 35 via Craigslist. Because the unit looked rusted and in generally bad shape, I was able to get an additional price reduction. The unit was missing the 7247/12DW7 driver/phase splitter tubes, the can cap didn't work either, and the boards were cracked and beyond repair. However, the seller assured me that the original Dynaco transformers were in good operating condition.

Dynaco Stereo 35 2.JPG
Dynaco Stereo 35 3.JPG
Dynaco Stereo 35 6.JPG

The power tubes are old RCA 6BQ5's that tested good.

I removed everything from the chassis and tossed the printed circuit boards. I ordered new blank replacement boards, a new can cap, a chassis bottom and a few other parts from Kevin at Dynakitparts.com. As mentioned earlier, Kevin is very knowledgable and very responsive. I am grateful that guys like him are around for us DIYers and Dynaco enthusiasts. Kevin's PC-13 replacement boards are extremely well made using Polyimide (a.k.a. Kapton), which is superior to the original Phenolic boards.

I started off using a 3M scouring pad to knock off the rust, and followed that with Rustoleum Rust Stripper. After a thorough cleaning with dishwashing liquid and water, I wiped the surface with alcohol for a final cleaning. Next, I used Rustoleum metallic enamel followed with a Rustoleum clear coat to seal the finish. The final paint cure was in my kitchen oven for 20 minutes at 180 F.

For the transformers, I used a brass brush to knock off the loose rust, followed with an alcohol wipe. Then I used some Rustoleum engine paint to handle elevated temperatures (up to 800 F). I followed that with a light polish.

For all the hardware, I used a brass wire brush and WD-40 to clean the rust off.

Dynaco Stereo 35 9.JPG

I populated the PC-13 boards with KOA Speer Carbon film resistors, CDE Silver Mica caps, Panasonic ECQP Polypropylene film and foil caps, and Sonicap Gen 2 caps. I also installed some nice Vampire CM1F RCA connectors. For wiring, I decided to go with Mil-Spec Teflon-insulated Copper wire following the general tube amp wiring color codes. The original wiring used black PVC-insulated wire that was heavily oxidized. Assembling the unit back together, I simply followed the instructions in the original Dynakit Stereo 35 manual.

Here it is in its finished state:

Dynaco Stereo 35 12.JPG

Dynaco Stereo 35 15.JPG

I brought it over to a friend's audio get together. We hooked it up to his Electro-Voiee 12TRXB fullrange triaxials mounted in JE labs open baffles. We used his Conrad-Johnson PV10B tube preamp and another friend's restored Thorens TD-124 turntable. Playing the Mobile Fidelity edition of Pink Floyd's "Dark Side of the Moon," we were in sonic heaven. The 12-15 watts from the Dynaco amp with these 101dB efficient triaxials was producing chest thumping bass. Of course, the mids and highs were outstanding as well.

I restored and modified a Magnavox 9304-20 6BQ5/EL84 console amplifier and I have been using this as my main amp. This is a paraphase splitter-type push-pull design. I love this amp with my upgraded Klipsch Forte II's.

Magnavox 2.JPG

Time will tell which amp is better, but I'm quite pleased with the way this amp has turned out. Now my friends at the get together are interested in buying the replica kits from Kevin. Some may will argue which new production output iron is better. My guess would be that Mike LeFevre's Magnequest MQ-565's are probably the next best thing to the original Dynaco Z-565's.

I'm thinking of bringing these two amps to the Burning Amp Festival in San Francisco in October.

[milsman2]

Are there any equivalents of the ECC832 that have the imaging similar to the tube blinking in this video:

My First Vacuum Tube Stereo Amplifier on 6c33c - YouTube