Comments on: Dynaco Stereo 70 Tube Amplifier

By: DrainDeclogger

DrainDeclogger — Fri, 05 Feb 2010 10:43:25 +0000

Great Unit. How about some details on how to hook up the Digital Volt Meters? Thanks. Nice going.

By: cjh4267

cjh4267 — Tue, 02 Feb 2010 17:43:16 +0000

Nice ST-70…great pink floyd album too!

By: valvezrock

valvezrock — Mon, 01 Feb 2010 23:35:48 +0000

Sweet ST 70. I recently purchased 2 of these voltmeters for my unit and would like the details of how you hooked them up. Where are you picking up the 5 volts? Thanks.

By: hubbatubey

hubbatubey — Mon, 01 Feb 2010 12:02:34 +0000

What the hell are those bias meters? Frickin Cool! I want them on my Dynaco ST-70!!

By: DrainDeclogger

DrainDeclogger — Sun, 31 Jan 2010 19:20:53 +0000

I have the same question. Thanks.

By: wurly1100

wurly1100 — Fri, 29 Jan 2010 21:06:50 +0000

You will want to supply the meters with around 6 volts. They are recommended up to 12 volts but that makes them way too bright. Anyway, get a transformer that supplies 6 volts and wire them in parallel.

By: wurly1100

wurly1100 — Thu, 28 Jan 2010 14:28:31 +0000

You can either make the connections for the bias within or outside the chassis. I have my wires (temp only) pushed into pin 8 and 3 on the front of the chassis. These are the socket pins for setting the bias. Pin 8 should read 1.56 and pin 3 is grounded.

By: wurly1100

wurly1100 — Wed, 27 Jan 2010 13:52:49 +0000

Again, you could also go into the chassis and make the connections inside to make it look a bit better. I’ve been playing around with my arrangement as to make it robust. Some people may want to buy some oct sockets from AES and push them into the front.
You will be amazed how much the bias changes over the period of warm-up of a few hours. Even changing out a rectifier tube will require a re-adjustment.

Regards,
Jim Ehlers

By: Lbuzzard

Lbuzzard — Mon, 25 Jan 2010 07:23:28 +0000

cool stuff jim!

By: plexuss

plexuss — Sat, 23 Jan 2010 02:34:21 +0000

i have a pair of dynaco Mk3′s. the thing about bias is that its better to measure the bias off each power tube separately. that means 4 meters. the reason is that each tube will age differently and adjusting the bias total of two tubes will not balances the bias between the tubes. example: if one tube is at 0.50 and the other at 1.00 you will sill read 1.5 on the total. best to measure and adjust each tube separately. i have my mk3′s set up this way.