octal trainwreck hammond conversion

[maxkracht]

Heres another trainwreck inspired conversion that I made this winter for my dad's 70th birthday. The hammond amp is about the same vintage as he is. AO-14 amp from a M2 organ. I used the original tubes, just in a slightly different order. 6sj7 input with a variable triode to pentode (morph) knob lifted from one of merlin’s books. 1MB pot with 100k resistor for tapering. 6SL7 2nd and 3rd stage. I mounted part of the tone stack on an extra tube socket and hid some caps in some old tube bases for some variation. 6sc7 phase inverter because internally tied cathodes were convenient. Larmar master volume. Cathode biased 6v6's. Was in a bit of a rush building it and neglected to take pictures, but I did get a timelapse video. (only took a few months to motivate myself to edit it together...)

IMG_7116.jpeg

IMG_6907.jpeg

IMG_7981.jpeg

[Colossal]

Nice build, mate!

Love the soundtrack

How's she sound?

[sluckey]

How do you work so fast with all that noise?

[maxkracht]

Nice build, mate!

Love the soundtrack

How's she sound?

Thanks. There's another video pinned to the youtube comments with some sound clips. All the trainwreck style things I have played just sound like classic rock to me. I'm not great at descriptions, but I'm pretty happy with it.

How do you work so fast with all that noise?

For some reason I always pick tunes that are alienating to the general public, but sun ra seemed to fit...

[Reeltarded]

LOVE THE AMP AND THE VIDEO!

The music was also fantastic!

[Reeltarded]

How do you work so fast with all that noise?

I just ejected things from my nose, things I need.

[dorrisant]

I thought I was fast at building... Haha! Nice job!!

[johnnyreece]

I've read Merlin's preamp book and always wondered about the Pentode/Triode control. What do you think of it? Worthwhile mod? Or, do you find yourself playing on only one setting?

[maxkracht]

Thanks for the kind words everyone.

I've read Merlin's preamp book and always wondered about the Pentode/Triode control. What do you think of it? Worthwhile mod? Or, do you find yourself playing on only one setting?

I didn’t live with the thing very long so I might not be the best judge. It’s definitely more volume control than eq. The tonal change is somewhat interesting but infinitely variable isn’t much more interesting than a pentode/triode switch. If I were to use it again, it would probably be in place of a volume control on a specific gain stage instead of in addition to. I will probably use the idea again, but not in the same way.

[ChopSauce]

Awesome video, thanks for sharing ...

... but how about the 1MB pot with 100k resistor(s), which I failed to see on the gushot?

[maxkracht]

Awesome video, thanks for sharing ...

... but how about the 1MB pot with 100k resistor(s), which I failed to see on the gushot?

That is the only picture I have; taken when the amp wasn't entirely finished. Was just before Christmas and I had distractions and other gifts to build... I also changed the power tube cathode resistor, cap, and probably a handful of other things after that picture. I mentioned that pot/resistor value in case someone else wants to try that bit of circuitry but doesn't have a 1M C taper pot. Will save you the extra few minutes of adding a trim pot to find what value feels right. Anything in the 50k-300k range is probably fine.

[ChopSauce]

Thanks a lot for your reply. I'm glad I could read at least one testimony about "pot mods", for I failed to find any until then. I'll try that, thanks again!

[maxkracht]

No problem. I do inappropriate things to pots all the time. Apologies if this is obvious, but the catch with tapering is, audio taper only works as a voltage divider, not as a variable resistor. That and remembering which side to add the resistor.