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-   -   Suggestions on driver stages for big tube MI amps. (http://www.diyaudio.com/forums/instruments-amps/196296-suggestions-driver-stages-big-tube-mi-amps.html)

leadbelly 9th September 2011 10:39 PM

Suggestions on driver stages for big tube MI amps.
 
I was hoping to get design suggestions for driver stages for my pet project, a big 200W tube bass head. It's more a thought exercise at this point, as I'm sure the price of a 200W OPT with good bass response will shock me back into reality.

As to what's already out there with 200W driver stages, there's of course Dogzilla:
http://www.dogstar.dantimax.dk/tubes...s/dz_pwram.gif
with its DC coupled followers, which is basically what an Ampeg SVT uses:
http://drtube.com/schematics/ampeg/svt6550-jp.gif

There's the Weber AB200:

:cop: Link removed by moderation

which uses an interstage transformer, which is a little unique for MI.

Thoughts? Of course using SS followers is always an option but I wonder if that might not be a goode solution for MI.

leadbelly 12th September 2011 03:16 PM

Nobody cares? Just thought of another candidate, how about a DC coupled pentode LTP like in the Tim Mellow OTL? I don't think I've come across that yet topology in commercial MI amps, but I bet that is because using small tubes as drivers is much more cost effective.

kevinkr 12th September 2011 03:57 PM

The MI guys have all moved to the instrument & amps thread which is where this thread belongs. I'll move it there..

tubelab.com 12th September 2011 06:00 PM

Quote:

Thoughts? Of course using SS followers is always an option but I wonder if that might not be a goode solution for MI.
My thoughts.....Mosfets are your friend. I use them in HiFi and MI. The bigger the amp the more they help.

kevinkr 12th September 2011 06:37 PM

Quote:

Originally Posted by leadbelly (Post 2704057)
<snip>
There's the Weber AB200:

:cop: Link removed by moderation

which uses an interstage transformer, which is a little unique for MI.

Thoughts? Of course using SS followers is always an option but I wonder if that might not be a goode solution for MI.

Please repost link to schematic, but please note in the post that it is a link to the schematic.

leadbelly 12th September 2011 06:58 PM

https://taweber.powweb.com/store/ab200_schem.jpg

This is a link to that schematic.

SemperFi 12th September 2011 08:15 PM

I like ampeg and would start there. What's the deal with Weber going the mile with a transformer coupled EL34 as driver (which would be able to truely drive the output tube) but wasting the potential with series capacitors and 15kohm gridstoppers? Might as well use a wimpy 12ax7 then!

leadbelly 12th September 2011 10:48 PM

Quote:

Originally Posted by SemperFi (Post 2707259)
I like ampeg and would start there. What's the deal with Weber going the mile with a transformer coupled EL34 as driver (which would be able to truely drive the output tube) but wasting the potential with series capacitors and 15kohm gridstoppers? Might as well use a wimpy 12ax7 then!

The more I look at the Weber design the less I like it. I think you're right about the grid stoppers: they are that size to primarily limit grid current when overdriven and not just to prevent RF oscillation. I looked at pictures and the interstage transformer is just a wimpy little thing. I think it's probably a mediocre design wherein reusing as many existing catalog parts as possible was a primary design objective.

211hojbjerg 13th September 2011 10:04 AM

Hi
DC connection with tube or FET driver will kick *** on any cap connection! the bedst cap is the one that have just been replaced by a DC connection.
*
best regards
Karsten

SemperFi 14th September 2011 06:27 PM

Quote:

Originally Posted by 211hojbjerg (Post 2707918)
Hi
DC connection with tube or FET driver will kick *** on any cap connection! the bedst cap is the one that have just been replaced by a DC connection.
*
best regards
Karsten

...so your suggestion is?


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