new dumble build in bassman head chassis

[Structo]

Looks great to me!

Rock on!

[andresound]

Thanks Tom,

She survived a practice last night. VERY loud (one EVM 12L in TL806 cab). Thank God for the Master. Although the master HAS to be over 3-4 before she starts to sound great.

The overdrive sound is not as great as my TW Express. So still some tweaking to be done.

[Structo]

I don't recall if you have a Dumbleator?

That is a great addition to the ODS, since you can have your preamp volume up around noon or more.

And the Master volume can also be up around 1:00-2:00 then the overall volume is controlled with the Dumbleator output pot.

This way you can get the amp cooking a bit but still control the volume with
the D'lator.

These amps take a while to learn how to play (at least me!)

[andresound]

Amp has a built in D'Lator. Hence the extra hole. Very crowded in this chassis!!!

[andresound]

Well, I'm not sure about that either but since this is negative voltage, it may be important to use a polarized electrolytic.

Most Dumble amps use a 100uF 100v cap in the bias.

FWIW, The bias cap is unpolorized and no smoke

[andresound]

Completed 2nd gen ODS amp in a 68 Fender Bassman chassis. My second build!

1. Based on #40
2. Built in Dumbleator
3. Master volume on front face ala Martin Manning design
4. NOS pre and output tubes. (Tele smooth plate in V1)

[andresound]

Here she is the the 48 year old cabinet. Kind of digging the "relic'd" look. Waiting on faceplate and knew knobs.

[andresound]

Now that the amp has settled, I decided to revisit the amp and finally address the dropping string to achieve the desired voltages as per Talbany's layout for a 2nd gen build. V1 and v2 were approx 10v down and the built in dumblelator 10v too high. B+ on power tubes was also approx 15v down. Because this is a Export Bassman PT, with multiple primary taps, I went from 240v - 230v tap (simply select the voltage selector on the back of amp). This allowed me to get the B+ up.

Being the lazy type, I have to admit, the thought of "tacking in" various resistor combinations to achieve the "holy grail" voltages did not sound like fun.

I have to say, I am glad I did this exercise. The amp sounds much better and the tone controls (including jazz/rock, mid boost) do seem to be more even. I was getting a HUGE diff in volume between Jazz and Rock settings. Voltages are now within a few volts of the 2nd gen posted by Talbany in the files section.

Only 2 problems to solve;
1. Mid control does not seem to do much.
2. The accent switch does %$@£ all!! It is a 1uf as per layout and schematic. I have tried different values. Reverse polarity etc. No luck

Any suggestions?

[jazzyjoepass]

Here's mine that I did a while ago


https://www.facebook.com/tritoneamplifi ... =2&theater


https://www.youtube.com/watch?v=Ns5a8Iz ... hVXqI_BTxp