Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Gone_Fishing on November 17, 2012, 10:18:54 am
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First, I want to thank everyone for helping me with my 6G9 Tremolux bias questions.
I just finished my ReVibe. It is dead quiet, the reverb sounds really good (it does seem to take more Dwell and Mix to get to the same level as my 1966 Fender Reverb unit).
My question is: the Tremolo sounds more like a Leslie (kinda throaty). It works great otherwise (I do need to slow the Tremolo down a bit). I have tried different tubes,,,NOS 6K6, USA 6V6, as well as good USA preamp tubes. The Reverb sounded better with the tube changes, but the Tremolo didn't change. It doesn't sound "bad", just more like a Leslie than the tremolo on my blackface Fender amps. Is this inherent with this design or can some changes be made?
Anyone with any ID's?
Thanks,
Eual
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By design the Revibe trem will sound more lush than the typical blackface trem. You can slow it down by changing one of the 0.01µF caps in the LFO circuit to 0.022µF. I have one such mod in my warbler where I left the original cap and switch another 0.01µF in parallel. This give a slow range and a fast range.
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My question is: the Tremolo sounds more like a Leslie (kinda throaty). ... It doesn't sound "bad", just more like a Leslie than the tremolo on my blackface Fender amps. Is this inherent with this design or can some changes be made?
If it doesn't sound like your blackface amps, then it's working 100% correctly.
The "tremolo" is based on the 6G12 Concert (http://www.el34world.com/charts/Schematics/files/fender/CONCERT_6G12.pdf). That's 2 tubes (4 triode sections) just for the tremolo circuit.
It doesn't just pump the volume up and down, but acts a lot more like a Magnatone vibrato circuit or, as you mentioned, a Leslie.
I think Fender moved away from this circuit after transitioning form the blonde amps of the early-60's to the blackface amps of the mid-60's because the patent on the Magnatone circuit kept them from getting the full-on vibrato, the circuit took a LOT of extra parts, and not everyone wanted vibrato as much as they might want tremolo.
You can read some info about the origins of this circuit here (http://www.el34world.com/Hoffman/revibe_origin.htm).
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Thanks Steve and Hot Blues Plate (that reminds me, I'm hungry),
I will try to get my friend take some pics of my ReVibe and post them for me,,,this is why. I started with Jeff Gerhing's layout and did all the under the board connections first,,,about 60 in all with 120 solder joints. All I have ever worked on is black and silver faced Fenders, and I wondered if I could do a "Fendery" layout and add all the new caps and resistors that the Revibe required and the unit still work. So, I drew out my own layout using the Fender layouts on the 6G12 and 6G15. I used Doug's cloth covered wire, put the power caps on the back (like a good little Fender should be) and made my oun islet board (again, most parts from Doug).
I knew that Fender started using shielded wire when their lead-dress started looking like a bird's nest (I have rewired a few of those). So, I kept my lead-dress as neat and black-face looking as I could and didn't use shielded wires (except for the reverb wires running to the reverb tank). The unit is dead quiet without shielded wires.
The only difference is the "kinda Leslie sounding" Tremolo which doesn't sound bad, just different than what I'm used to, as Blue Plate pointed out (it actually sounds cool).
Again, I'm a hobbyist, and don't understand much of the electronic things, but I can follow a layout and a schematic.
Thanks again,
Eual