Low Tide Possibly Odd Behavior

[Gsatterw]

Hey guys I’ve been able to get my Low Tide functional and some cool warbles out of it, but have noticed some potentially odd behavior and we hoping others can confirm the observations with theirs, and possibly where to check for errors if mine is behaving strangely.

1. Gate trim pot - no volume passes until the trim pot is at about 90% clockwise. Once there the main gate pot works and has a decent sweep to it.

2. Volume - I feel like even at full volume the pedal is slightly below unity gain.

3. Mix - when the mix is at 0 and 100, the volume is constant, but in between settings their is a volume drop.

This is the first time I’ve ever used an SMD part (2SK208-Y) so I’m a bit nervous about that. I bought some J201’s through hole from smallbear a few years back so I’m hoping those are real.

Anyways, thanks for any input. Happy to provide voltages wherever to help out. Much appreciated for reading.

 

[Gsatterw]

So just saw some videos and seems like this circuit should be boosting the signal more than it is.

Where is most of the volume gain supposed to come from in this circuit? I threw together an audio probe and have been poking around to try and identify any signal loss, but so far it seems the volume is pretty consistent in the output side of the circuit around the two transistors after the mix and level pots.

Any and all input is appreciated!

 

[Gsatterw]

So I swapped out the 2SK208-Y for a TO-92 J201. No change.

I poked around some more and looked at the circuit diagram more. Figured the LM258P opamp should be amplifying the signal a good bit. The input to the opamp was barely perceptible and the output was very quiet also. Decided to roll some opamps. Tried: JRC4558, JRC4580 and TL072. Both JRC’s seemed louder than the 258P with the 4580 being the most HiFi sounding. TL072 was not as loud and muddy. I’ve rolled op amps in other pedals and usually they all sound pretty much the same. Not the case here. The difference was stark.

Anyways, kept the 4580 in there. Interestingly the entire range on the gate trim pot now passes volume. The pedal is louder but the mix knob still has a volume drop through the sweep and I’m still thinking it should be louder. How much should the JFETs/other transistors be boosting the signal? They seem very low gain.

 

[Gsatterw]

I guess the mix in the middle would be quieter than 0 or 100 because in the middle both signals have to pass through an additional 50k of resistance to get to the output?