Increasing wet signal in Kalamazoo 12

[jukelemon]

Hi all.

Ok..got reverb working but the wet signal is a lot less than I would want.

Can someone help ID the resistor that would serve as the mixing resistor in this amp?

I see R13/R14 form a divider so I would think it would be R14. Please confirm.


Or R31...increasing the front end?


Thanks all.

[jukelemon]

Ok..please disregard.

I just watched a bunch of vids and this amp should have way more wet signal as a baseline.

So something is still wrong in the reverb circuit. Any suggestions?

[tubenit]

Things that might help increase reverb:

C15 to 22uf

C16 from .001 to 220p

Remove R14 or reduce it to 100k-220k range.  (And where R13 & R14 intersect, add a 10k to 33k grid resistor to V2a)
OR I would be inclined to reduce the 2.2M reverb pot to 1M and have a 220k R14 above it.   

R27 to 100k   and R28 to 1.5k

With respect, Tubenit

[HotBluePlates]

... the wet signal is a lot less than I would want.

Can someone help ID the resistor that would serve as the mixing resistor in this amp?

I see R13/R14 form a divider ...

If you turn the Reverb pot full-up, do you still not get enough reverb?  I ask because Fender's circuit typically gives way more reverb than most players want/use, and we don't want to stumble into making a circuit where the Reverb control is barely turned on just for the sake of having "Wow!" reverb at low settings.


In a perfect world, you would have a spare reverb tank to swap in to this amp to verify this isn't an issue with the tank itself.  (EDIT:  It seems you already tried this, but it was posted in a different thread...)

R44 (150kΩ) and R31 (1MΩ) form a divider reducing the signal level going into the Reverb Driver tube (V3a).  You might consider replacing R44 with a piece of wire to increase the drive to the tank (if desired). 

R13 (470kΩ), R14 (1MΩ) and R15 (2MΩ Reverb pot) form a divider that mixes the Dry and Reverb signals.  This can't be directly compared to a Deluxe Reverb, but the Deluxe would have R13 closer to 2-3MΩ, and R14 closer to 470kΩ.

Were I in your shoes, I would think about measuring the AC Volts to the Driver tube grid, to the tank input, and at different points along the divider/mixer of a typical Fender amp with reverb.  Those can be compared to similar measurements in your amp to determine whether there's a tank issue, circuit issue, or simply a need to adjust the original circuit to get the response you prefer.

[jukelemon]

Things that might help increase reverb:

C15 to 22uf

C16 from .001 to 220p

Remove R14 or reduce it to 100k-220k range.  (And where R13 & R14 intersect, add a 10k to 33k grid resistor to V2a)
OR I would be inclined to reduce the 2.2M reverb pot to 1M and have a 220k R14 above it.   

R27 to 100k   and R28 to 1.5k

With respect, Tubenit

Thank you!!

[jukelemon]

... the wet signal is a lot less than I would want.

Can someone help ID the resistor that would serve as the mixing resistor in this amp?

I see R13/R14 form a divider ...

If you turn the Reverb pot full-up, do you still not get enough reverb?  I ask because Fender's circuit typically gives way more reverb than most players want/use, and we don't want to stumble into making a circuit where the Reverb control is barely turned on just for the sake of having "Wow!" reverb at low settings.


In a perfect world, you would have a spare reverb tank to swap in to this amp to verify this isn't an issue with the tank itself.  (EDIT:  It seems you already tried this, but it was posted in a different thread...)

R44 (150kΩ) and R31 (1MΩ) form a divider reducing the signal level going into the Reverb Driver tube (V3a).  You might consider replacing R44 with a piece of wire to increase the drive to the tank (if desired). 

R13 (470kΩ), R14 (1MΩ) and R15 (2MΩ Reverb pot) form a divider that mixes the Dry and Reverb signals.  This can't be directly compared to a Deluxe Reverb, but the Deluxe would have R13 closer to 2-3MΩ, and R14 closer to 470kΩ.

Were I in your shoes, I would think about measuring the AC Volts to the Driver tube grid, to the tank input, and at different points along the divider/mixer of a typical Fender amp with reverb.  Those can be compared to similar measurements in your amp to determine whether there's a tank issue, circuit issue, or simply a need to adjust the original circuit to get the response you prefer.

Thank you very much and I agree that the Fender circuit has WAY too much reverb-much of which is wasted/not used.

When the Rev Pot is maxed, it is just about right BUT then I watched a bunch of vids of other amps and they had much more reverb available.  So, it would be ideal to find why this amp doesn't do those things.

Of course..it is just as logical to assume the amps I saw had work/modifications done and their verbs are not factory :) 

All the components/wiring in this amp are original minus the 40/20/20 uf caps I changed out and me rewiring the terrible grounding scheme/addition of a three prong.

The amp is now dead quiet (biggest complaint on these) and strong.  I suspect the caps on V3/in the reverb circuit are weak and especially the cathode caps.  That is my gut and have not gotten to the point of pulling them to test.

Good idea on the measuring of AC in comparison to a Fender!

[HotBluePlates]

I'm starting to get to a point where I listen to an unfamiliar amp, think something's wrong, then question myself:  "But is it really wrong, or is my expectation wrong?"


We can fix a lot of the over-strong reverb in a Fender by using an audio-taper Reverb pot.  But that's modifying the circuit from "what it is."

I had similar thought when I had a Supro Spectator amp, which is much like a tweed Princeton.  Except the Supro is darker, because its Tone control is configured to dump treble only, while the Princeton's Tone control can also cut bass by acting like a Volume pot bright cap.

I thought about modifying the Supro for a while, but decided to let it be what it is, and turn the Tone control full-up.  It meant playing my Tele bridge pickup had a cool 50's sound, without being overly-bright.

[shooter]

"But is it really wrong, or is my expectation wrong?"

after painting for 17 years and fixing amps about as long, only the original creator knows "what's right" even when the rest think "Hmm?? what were they smok'n" 

[jukelemon]

I'm starting to get to a point where I listen to an unfamiliar amp, think something's wrong, then question myself:  "But is it really wrong, or is my expectation wrong?"


We can fix a lot of the over-strong reverb in a Fender by using an audio-taper Reverb pot.  But that's modifying the circuit from "what it is."

I had similar thought when I had a Supro Spectator amp, which is much like a tweed Princeton.  Except the Supro is darker, because its Tone control is configured to dump treble only, while the Princeton's Tone control can also cut bass by acting like a Volume pot bright cap.

I thought about modifying the Supro for a while, but decided to let it be what it is, and turn the Tone control full-up.  It meant playing my Tele bridge pickup had a cool 50's sound, without being overly-bright.

Yeah, I hear ya lol.  I really try to leave well enough alone but hearing 3 other amps on YT which much much more reverb, I am willing to bet a few caps are tired on V3.  We shall see!  Going to start subbing in things just for Shi-ts and Giggles and prove out my hunch.

[jukelemon]

"But is it really wrong, or is my expectation wrong?"

after painting for 17 years and fixing amps about as long, only the original creator knows "what's right" even when the rest think "Hmm?? what were they smok'n" 

True that!