Fender Super Twin Reverb with Dumble-Style Mods...continued

[ic-racer]

How you been?

This Spring I need to just sit down and finish that HRM project that is still hanging out there. I have been spending too much time playing and recording guitar and not enough amp building

I have some massive mental block when I have to re-do something. I had to re-do all the PC boards for that HRM. They are all ready to go in the etching solution. I don't know what my problem is; the boards are sitting in a box under my desk.

[odourboy]

I have been spending too much time playing and recording guitar and not enough amp building

I have the exact opposite problem.

[Structo]

Since I have been out of work and a stay at home kept man, I have tried to play my guitar at least one hour per day.

I have actually made some progress but it isn't easy to correct 40 years of bad technique.

[cxx]

Here is a sound clip demonstrating the 'Deep' switch with a strat: http://soundclick.com/share?songid=6524788

Here is another with the strat, demonstrating the OD channel with the 12AX7 instead of the 6C10. http://soundclick.com/share?songid=6524783

Great playing The sound is to me somewhere between fender and dumble. Did You use the fenders own reverb ? If You dont have the NFB yet in this amp, I would suggest You to try it. To me it makes the nonHRM sound more dumbly.

Really nice phrasing

Thanks for the comments. Now I have added the 100k pot (which just came in the main) to the Mid and it really changes the whole character of the amp. Now the clean channel has much more bass and mid gain. Sounds less like a Fender, but it drives the OD section much better. The difference between PAB and Non-PAB is just right.

Now that I have more gain, I thought I would try the grid stoppers (270p) again. However, again they make the amp sound just bad. Reminds me of a transistor distortion with the treble rolled off to try to make it less harsh.

So, I have them off now.

In terms of the NFB, check out that file "Modified SuperTwin Power Supply.pdf" and I show what I have done. The original NFB resistor value got cut off in the file, but it is a 850R. This hooks to a typical Dumble type Presence control.

I'm not sure I saw the last schematic but the original NFB pair was 820/100 off 4 ohms. It looked like you have 820/390 now, like almost a third the output signal in the NFB loop rather than a ninth. Is that really the case? Seems like a lot if so.

[ic-racer]

My notes on this are actually all in this thread. Looking back, I believe my thought was that with the original 100k in there the D-style presence may not be as effective.

Right or wrong this is what I thought: more resistance at that point = more negative feedback = more opportunity for the presence control to have an effect. Or, less resistance = less NFB = presence may not do anything.

[talbany]

You need to be very careful if you do the 390/820/5k pot w/4 or 8 ohm tap.. Too much NFB can wreak havoc on the PI (input side) I had one last week..Also careful not to run the wires to the presence pot to close to other wires carrying signal ie master/level.. AC coupling there can cause congestion FWIW

Build On!!..Tony

[ic-racer]

I opened up the amp and found an error in my design. I had left the 820R resistor in the NFB loop. I changed that to 3k2.

Here is a recent clip from the amp in its current state.
http://www.youtube.com/watch?v=NvkB2wETTBc

[ic-racer]

Some pictures I forgot to post
First is the new NFB resistor:
[IMG768]http://img.photobucket.com/albums/v670/ ... file-1.jpg[/img]

[ic-racer]

I don't think I ever posted a picture of the completed 12V supply. I have it installed right behind the pilot light:
[IMG768]http://img.photobucket.com/albums/v670/ ... file-2.jpg[/img]

[ic-racer]

For the sake of completion, here are the speakers. They are the original speakers. I specifically did NOT replace them. How can one justify owning over 10 amps if they all sound the same??
[IMG768]http://img.photobucket.com/albums/v670/ ... file-3.jpg[/img]

[ic-racer]

The amp started humming and the output tube balance was not stable. I opened it up and found two wires on one of the output sockets almost touching. I re-soldered the wire and gave the whole amp a good inspection.
It is still sounding good with the tubes I had put in it back in 2013.

[shermanpup]

I have a Fender super twin I bought brand new .I knew nothing when I bought it . I have the electronics to do the mods here if a complete unified instructions were available. Therr doesn't seem to be any good recordings of these mods . Can the amp sound like this ?
https://youtu.be/5T_N1RoKKdQ https://youtu.be/QYQuWh_YngU ?
Thanks

[ic-racer]

https://m.youtube.com/watch?v=NvkB2wETTBc

[Ck0y0TE]

I make a YouTube video of the amp construction. Well, really just a tune playing with a lot of panning across the snake-pit of wires inside the amp.

http://www.youtube.com/watch?v=MlPjDWY0NXI

just to let you know, if you still receive messages at all....
I' watched your vid. Thx a bucket of tone! Great inspiration. You made it a dream amp.
I have this STR head that I want to convert to an amp which has all knobs do something that is likeable.
The clean tone i got now is good, but there's just too much that isnt usable on it. EQ+Distortion mainly.
It's gonna be a hard and steep learning curve and I might end up distroying it. We ll see.
Thx!

[Ck0y0TE]

I have a Fender super twin I bought brand new .I knew nothing when I bought it . I have the electronics to do the mods here if a complete unified instructions were available. Therr doesn't seem to be any good recordings of these mods . Can the amp sound like this ?
https://youtu.be/5T_N1RoKKdQ https://youtu.be/QYQuWh_YngU ?
Thanks

If you got anything... I have this Super Twin Reverb head I want to mod too.