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Hi
I recently picked up the chassis of a Garnet 15R tube reverb unit.
It came with a tiny 2 spring tank
I recapped it as the filter caps were quite unhappy and hooked it up to a Gibbs 2 spring long tank, as the one it came with (which I think might not have been original) , whilst it produced tonnes of reverb , also produced lots of ugly metallic feedback (I also tried it with a small 3 spring tank that sounded decent but the Gibbs was better)
The reverb sounds good now but there's a few things I'd like to address if possible.
-It really preamps and warms up the signal from the guitar. I can live with the extra volume but i don't like how muddy, midrangy and woofy it sounds compared to the sound straight into my deluxe lite conversion. I tried putting 12AT7s and 12AU7s in the preamp section and got less volume but also less reverb,
- I'd like to get more reverb. The Gibbs tank sounds great but not super loud. It would be nice to go beyond a tasteful amount of reverb into full on surf /effect territory occasionally(ala my Super Reverb) Can I accomplish this?
- Maybe a way to mix the dry and wet signals, and or adjust the dry one more
- I've noticed there seems to be a bit of sizzly distortion to the reverb too could that be a tank impedance mismatch?
the schematic is chopped in the top right corner
There is a .1mfd cap between the 12au7 plate and the 1 meg lin pot (labelled 'colour' basically a reverb tone pot)
I've noticed a few differences between my unit and the schematic that Garnet very nicely sent me
On my unit :
-The resistor to the right of the line going to the .1 mfd cap and then to the output is 10k not 1.5k like like the schematic
- The line coming back from the reverb tank goes straight to the ft switch and then straight to the 1meg linear reverb control pot. There is no 100k resistor to ground, nor is there a .001 mfd cap before the 1 meg pot
- there is no .001 bypass cap on the 470k mixer resistor coming from the input to the grid of the 12ax7 (where the reverb tank signal is sent through a 470k resistor and 470pf cap)
- also on the schematic the filter cap at point 'C' is 30mfd. on the can cap I replaced under chassis it was 20 mfd
I have the following voltage measurements of the 12au7 and the 12ax7
12AX7
pin 1- 250v
2 - .6 mv
3 2.9 v
pin 6 - 154v
7 - 3.2 mv
8 - 1.3 v
12au7
pin 1 - 280v
2 - 56v
3 - 80v
pin 6 - 334
7 - 51mv
8 - 15v
I recently picked up the chassis of a Garnet 15R tube reverb unit.
It came with a tiny 2 spring tank
I recapped it as the filter caps were quite unhappy and hooked it up to a Gibbs 2 spring long tank, as the one it came with (which I think might not have been original) , whilst it produced tonnes of reverb , also produced lots of ugly metallic feedback (I also tried it with a small 3 spring tank that sounded decent but the Gibbs was better)
The reverb sounds good now but there's a few things I'd like to address if possible.
-It really preamps and warms up the signal from the guitar. I can live with the extra volume but i don't like how muddy, midrangy and woofy it sounds compared to the sound straight into my deluxe lite conversion. I tried putting 12AT7s and 12AU7s in the preamp section and got less volume but also less reverb,
- I'd like to get more reverb. The Gibbs tank sounds great but not super loud. It would be nice to go beyond a tasteful amount of reverb into full on surf /effect territory occasionally(ala my Super Reverb) Can I accomplish this?
- Maybe a way to mix the dry and wet signals, and or adjust the dry one more
- I've noticed there seems to be a bit of sizzly distortion to the reverb too could that be a tank impedance mismatch?
the schematic is chopped in the top right corner
There is a .1mfd cap between the 12au7 plate and the 1 meg lin pot (labelled 'colour' basically a reverb tone pot)
I've noticed a few differences between my unit and the schematic that Garnet very nicely sent me
On my unit :
-The resistor to the right of the line going to the .1 mfd cap and then to the output is 10k not 1.5k like like the schematic
- The line coming back from the reverb tank goes straight to the ft switch and then straight to the 1meg linear reverb control pot. There is no 100k resistor to ground, nor is there a .001 mfd cap before the 1 meg pot
- there is no .001 bypass cap on the 470k mixer resistor coming from the input to the grid of the 12ax7 (where the reverb tank signal is sent through a 470k resistor and 470pf cap)
- also on the schematic the filter cap at point 'C' is 30mfd. on the can cap I replaced under chassis it was 20 mfd
I have the following voltage measurements of the 12au7 and the 12ax7
12AX7
pin 1- 250v
2 - .6 mv
3 2.9 v
pin 6 - 154v
7 - 3.2 mv
8 - 1.3 v
12au7
pin 1 - 280v
2 - 56v
3 - 80v
pin 6 - 334
7 - 51mv
8 - 15v