Two-channel > Harmonic Tremolo > Reverb > Low Watt Amp Build

Snfoilhat

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Spent a lot of time on the sockets with all their connections between pins. Don't want to have to go back in and fix a mistake. Missed a couple eyelets on the board and will add them before soldering it all together. Added a third standoff in the middle of the board :)

Happy Father's Day
 

Snfoilhat

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Not yet powered on. Here is the 2-channel reverb amp with the handful of changes and component substitutions made along the way. Gotta do a visual check against the schematic, look at all the solder joints, all the boring stuff it's so tempting to gloss over.

Also haven't yet wired the speakers together and that might be helpful for moving along o_O
 

Snfoilhat

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It runs!
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I reworked the power supply from cascaded to star to keep the voltage supplies higher in the preamp. The most consequential change was to add a filter capacitor to the voltage divider for the heater elevation. Without that, the amp had a terrible buzz. This is the first thing I'm going to try in the harmonic tremolo amp, which has a similar heater elevation system and I neglected to include this cap.


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Guaranteed by Good Housekeeping :D

I don't know if tubes being sold as "NOS" just means includes an old matching box or tests-as-new or what, but these old USA 12AU7s were something like 10% of the asking price of a 12AX7 of the same origin and date of manufacture.

Single-ended_Reverb_Amp_3x10_draft_3.JPG


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Trying out the baffle in the 60s Bandmaster orientation.

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It's not a gain monster, but with the gain low and the volume high, there are nice cleans with ok volume in the room, and with the gain high it does touch sensitivity and an overdrive approximately like the Matchless Hotbox wannabe pedal I built years ago, which I've been missing. I haven't turned it up loud enough yet to hear what the higher preamp tones pushing the power section sounds like but I'm hopeful.

The reverb is as wet as you'd expect from a Fender and doesn't hum like crazy which is a relief.
 

Snfoilhat

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The needs improvement stuff:

The only reverse audio pot I had for the treble cut is 3M, and I think it's going to work better with something smaller next time I order parts. I only hear it near the very end of the sweep.

Turing the volume up to 10, it consistently gets louder, which means it's never running out of headroom, which I take to mean that I can dump less of the dry signal and get more total volume out of the amp.

I'm going to play it more and turn my attention to finishing the harmonic trem amp, circling back later. Thanks for all the help
 

Snfoilhat

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@King Fan that's kind of you to say, thanks very much!

@mountainhick I'll record something soon, thanks!

***

I added a 47 μF 100V capacitor across the heater elevation resistor and it quieted the harmonic tremolo amp's reverb more than all of the shielded wires and extra caps I tacked in all together. I can't believe how many times I looked at the schematic and noticed that cap was missing and told my self, full of confidence, that it wasn't necessary and anyway that the noise I was hearing wasn't heater noise so it _must_ be something else 🤯
 

Snfoilhat

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Phone video, unedited, unrehearsed, to share the tones 😬


I'm using the treble-bass channel for dirty because the treble-middle-bass channel has some unresolved lead dress issues and is noisier at higher gain settings. TMB channel set clean with the volume in the room approximately the same.
Ch I Gain 10, Bass Cut +, Treble 7, Bass 5, Volume 4; Ch II Gain 5, Bass Cut -, Treble 7, Middle 7, Bass 7, Volume 4; Reverb 4, Cut 1 (minimum high cut)


Here's the harmonic tremolo + reverb amp on the left and the dirty channel of the cascode amp on the right set up ABY
 
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