Kay tremolo above unity volume

[Supernaut_]

Hi guys!

I recently built the Kay Tremolo kit from Musikding (https://www.musikding.de/The-Kay-Tremolo-kit) with a few tweaks. I replaced C4 and C5 with 6.8uF caps to slow it down a bit, replaced R4 with a 500k trimpot for biasing Q1, replaced R11 with a 1M lin pot for depth control, replaced the speed pot with a 1k rev log, and replaced Q1 and Q4 with 2N2222 transistors.

The only issue left to resolve is the pedal's volume. I want it to be unity volume, but at the moment it's pretty loud. I'm thinking about replacing R1 with a 100k trimpot, would this fix work?

Schematic:
https://www.musikding.de/docs/musikding/kay/kay_schalt.pdf

Cheers!

[antonis]

IMHO, better try to tweak R7 value..
(make it 47k or so..)

[Peetem]

IMHO, better try to tweak R7 value..
(make it 47k or so..)

Or use a 100K pot in place of R7....

[iainpunk]

replace R8 with a 100K trim pot where the outer lugs are in the circuit, and the middle pin is connected to the output. this way you have a regular volume control (except, its not log) to easily change the volume.

cheers, Iain

[antonis]

On a second thought, raising R1 value is the only mod not involved in altering initial amplitude modulation margins..
(but it's an asking for noise troubles certain mod..)

[willienillie]

IMHO, better try to tweak R7 value..
(make it 47k or so..)

Or use a 100K pot in place of R7....

Or a 50k volume pot in place of R8.

[PRR]

.....it's pretty loud. ...

I should say so. Gain in the gain stage is like 150. It should be closer to 2. There's no simple way, that I see, to get the gain down without tricky trace-cutting or so much passive loss that hiss/overload rage get poor.

[Rob Strand]

To reduce the gain, insert a resistor in series with the emitter try 100R, 220R, 470R.

Leave you 4.7k collector resistor.  The aim here is just to show the emitter resistor.


(Don't copy caps from this one.)

Ideally you would like use as large as possible emitter resistor, remove the 33k, and raise the 470k and 43k.
Use emitter resistor to tweak gain and "43k" position to tweak bias voltage on the collector.

As is the 33k is the only think keeping the input impedance high but it adds some noise.    Using an emitter resistor should significantly increase the input impedance.    The problem then is the 43k, as it then become the limiting factor for input impedance.  It should be possible to raise that somewhat as well, you could set it to 100k or more then tweak the 470k position to bias the collector.

[Supernaut_]

Thanks for all the help fellas! So I'm guessing my best bet would be replacing R8 with a 50k trimpot or wiring a volume pot from the board out connection. Any difference between the two in terms of functionality? I'm leaning towards a trimpot solution, as I'm really only interested in a fixed unity volume level.

Cheers!

[iainpunk]

well, the trimpot is/should be wired just the same as a volume pot, but set and forget, instead of exposed.
i'd personally go for trim pots all day long.

cheers, Iain