OT for AB763

[duke of earl]

a few years ago I built my first amp-A Hoffman AB763 circuit for 2x6L6 tubes. I used a 100 watt PT and a 100 Watt OT for more headroom. I also used a GZ-34 Port Arthur Rectifier (Gerald Weber Mod) to get a little compression on the front of the note which works very nicely. I am toying with the idea of going with a 50 watt OT as I want the amp to breakup moderately but still maintain descent clean headroom. I have actually put some EH 6v6"s in the amp and put a 15k feedback resistor in and I'm not really digging the overdriven tone with this setup. The speakers are 1 Weber Legacy 12"and 1 Weber California Alnico 12". The speakers are not broke in yet and I wonder should I wait for the speakers to settle in before making any changes to the topology? Your thoughts are much appreciated.

[duke of earl]

speakers are 16 ohm each run in parallel. The circuit is a Hoffman Board layout for the most part with some tweaks.

[duke of earl]

If you look in Doug's circuits, you will see an AB 763 that he tweaked. It is found under the Hoffman Board Building Section in the Library.

[EL34]

018343
It's a great OT. I sell alot of them and people really like them.
http://www.hoffmanamps.com/MyStore/catalog/parts1.htm

I have one in my Super Vibrolux Reverb with a pair of EH 6V6's but I have also used it with 6L6's

[duke of earl]

Thanks Doug. How do the 6v6's respond to this model?

[Dave]

You said you were using a 100 watt PT. So, you intend to use a pair of 6V6's with a Twin Reverb PT and a Super Reverb OT?
First, are you looking to find out how quickly you can kill a pair of 6V6's?
Second, you will create a 100 percent mismatch between your OT and your speakers by using 6V6's.
It will work, but it seems pretty, hmm, unorthodox.
Ever see a Volkswagon Beetle with a V12 and a power glide transmission?

Dave

[duke of earl]

Dave,

I originally used 6l6's and by using the bigger OT, doubled the speaker impedance to match the reflected impedance. Doug says the Electro Harmonix 6v6's can handle the plate volts in a Twin Reverb so I thought I'd give em a try. I'm still a novice to amp building and am trying different things to feel out what works and what doesn't. When I had the 6l6's in the amp, I blew my California speakers so I wanted lower wattage output tubes after the recone job. You could say I am adventuress in my endeavor! Thanks for your advice and to all who are posting here.
Weber speakers
Getting the Eric Johnson Tone

[Willabe]

Yes tell me, Why does love have to be so sad?

You sound good Duke.


                  Brad   

[PRR]

> When I had the 6l6's in the amp, I blew my California speakers

The Weber California? That's suggested to be "like a JBL" and really should eat ALL the output of a couple 6L6. I wonder what went wrong?

[duke of earl]

I played the amp on "11" with overdrive and humbuckers for a couple of years. Yes they are weber alnicos @ 65 watts a piece.