Suggestions on driver stages for big tube MI amps.

[leadbelly]

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:

with its DC coupled followers, which is basically what an Ampeg SVT uses:


There's the Weber AB200:

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]

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]

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

[tubelab.com]

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]

Originally Posted by leadbelly

<snip>
There's the Weber AB200:

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]

This is a link to that schematic.

[SemperFi]

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]

Originally Posted by SemperFi

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]

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]

Originally Posted by 211hojbjerg

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?