Dynaco Stereo 70 Tube Amplifier

Posted by  in Tuesday, January 5th 2010   
Topics: Pro Audio    
wurly1100 asked:


Restored 1950′s Dynaco Tube Amplifier Courtesy of Jim Ehlers.

Custom rims wholesale…instantly.

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21 Comments

TullioWalker said in January 8th, 2010 at 11:37 am    

Great amplifier, of course. I don’t know if you like Manley amps but check”EL34 Manley Snapper” here on YT. It’s very impressive too. Your comments will be very appreciated.

musmann said in January 11th, 2010 at 5:34 am    

Nice amp! I have a rebuilt ST 70 I put a new input board and the SDS Labs cap board in it.

mati1979 said in January 13th, 2010 at 6:11 pm    

Wurly, where can i buy this vu meter ? could you put this a exactly model ? thank you. (i have a ST70)

bcdhifi said in January 17th, 2010 at 4:00 am    

Real cool! I am glad that young audiophiles are into tubes. Thanks to you more vintage repro. is becoming available. Thanks for keeping DIY audio alive.

banaanemt said in January 17th, 2010 at 10:22 am    

Hello Jim.I have a restored st70 triode.
I like de meters very much.Can you gif the adress or website where i can buy it.
Regards Peter from Nederland.

63spats said in January 17th, 2010 at 8:29 pm    

Can you tell me where you got your meters from? Thanks

tubeglowaudio said in January 19th, 2010 at 1:08 pm    

where can i buy those meters? is there a website?

ramdass42 said in January 20th, 2010 at 10:31 pm    

I’ve added a video response to the ongoing conversation. I built a custom set of Dynaco Mark III’s before the retro kits were available. I had the same idea and built them into the chassis as can be seen in the video. Great way of integrating bias checking without having to pull out and plug in the good ‘ol multi-meter.

Rocketfrogs said in January 21st, 2010 at 10:16 pm    

Are the volt meters sitting directly on top of the output transformers? I have a Yaqin MC 10l and I think the heat from my transformers would fry the voltmeters.

kimbalxyz said in January 22nd, 2010 at 2:49 am    

Can you post a link for the volt meters ?
Thanks

icantdrive85 said in January 22nd, 2010 at 7:21 am    

Nice Wurly i think its a great idea, I’m going to upgrade an ST-70 soon, can you tell me your source for the meters? I can’t seem to find them.
David

plexuss said in January 23rd, 2010 at 2:34 am    

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.

Lbuzzard said in January 25th, 2010 at 7:23 am    

cool stuff jim!

wurly1100 said in January 27th, 2010 at 1:52 pm    

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

wurly1100 said in January 28th, 2010 at 2:28 pm    

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.

wurly1100 said in January 29th, 2010 at 9:06 pm    

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.

DrainDeclogger said in January 31st, 2010 at 7:20 pm    

I have the same question. Thanks.

hubbatubey said in February 1st, 2010 at 12:02 pm    

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

valvezrock said in February 1st, 2010 at 11:35 pm    

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.

cjh4267 said in February 2nd, 2010 at 5:43 pm    

Nice ST-70…great pink floyd album too!

DrainDeclogger said in February 5th, 2010 at 10:43 am    

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

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