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Sovtek MIG50: 511V plate voltage. Which "dark" 6L6 tube?
Posted: Sat Nov 17, 2012 7:17 am
by Harold
I recently bought a 90's Sovtek MIG50 with the original tubes in it. After replacing the poweramp wiring (was a real mess!) and all pots, I added pre PI master volume and fitted the preamp with JJ's.
The amp is still very bright and lacking (sub)lows. I guess that this might be due to the 20+ year old Sovtek 5881's (6P3S-e with the "coin" base). I even clipped the bright caps, but that didn't fix the brightness.
Schematic:
http://www.el34world.com/charts/Schemat ... G50-60.pdf" onclick="window.open(this.href);return false;
(My MIG has 100nF PI coupling caps and a few minor other differences from this schematic)
I was recommended the JJ 6l6GC, but
the datasheet tells me that the tube might not be happy running on the MIG's 511VDC plate voltage.
Any other recommendations for a fat, "dark" 6l6 that can handle a lot of voltage?
![Help me! :help:](./images/smilies/help.gif)
Re: Sovtek MIG50: 511V plate voltage. Which "dark" 6L6 tube?
Posted: Mon May 27, 2013 4:03 pm
by Tremblayamps
I threw KT-88's in a marshall 2204 and it gave it fat low end. You can try both 6550 and KT-88's. You will have to mod the Bias section most likely to handle the 88's. It would be r27 on the schematic (10k). After the I the put the 88's in I would never go back to 34's in that amp.
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Re: Sovtek MIG50: 511V plate voltage. Which "dark" 6L6 tube?
Posted: Mon May 27, 2013 4:24 pm
by Harold
Well, I've gone a slightly other path with my Sovtek Mig50
- Put in a IGOT-JMP50 output transformer
- Switchable V2a cathode bypass: none, 680nF and 220uF
- Switchable fixed resonance: 2n2
- Changed the 47nF in the tonestack to 22nF
- NFR to 100k (instead of 39k)
- Internal jumpering of both channels
- And ... JJ 6l6GC's
![Wink ;)](./images/smilies/icon_wink.gif)
Of this list, the output transformer made the biggest difference! With the fixed resonance engaged, I have to roll down the bass to at least 2-3, so that's a nice "bedroom level mod".
Re: Sovtek MIG50: 511V plate voltage. Which "dark" 6L6 tube?
Posted: Mon May 27, 2013 5:17 pm
by Tremblayamps
What are your thought on the ig transformers. I'm in the midst of a soldano project and im trying to find the best transformers and the ig transformers came up but i haven't reviewed them to much yet
Re: Sovtek MIG50: 511V plate voltage. Which "dark" 6L6 tube?
Posted: Tue May 28, 2013 8:52 am
by Harold
Tremblayamps wrote:What are your thought on the ig transformers. I'm in the midst of a soldano project and im trying to find the best transformers and the ig transformers came up but i haven't reviewed them to much yet
Well, Ingo has had some difficulties manufaturing them due to personal reasons but he is up to speed now and building a nice stock. His new webstore also doen't allow items to be sold which aren't in stock.
I bought two "Marshall" 50W OT's and one 100W. I've only used one 50W to replace the stock OT in my Sovtek MIG50 and it's a helluva difference! Loads of clear lows and way less "barking" aka annoying high/mids.
I have a couple of original 2203 and 2204's which I'm thinking about upgrading with IG transformers since they're kinda cheap ...
There might also be another MIG50 on it's way
![Wink ;)](./images/smilies/icon_wink.gif)