Maestro FZ-1b, low volume?

[drummer4gc]

Hey all,




I'm restoring a Maestro FZ-1b, which is running now and I think putting out the sound it should. However, the volume seems too low - with both controls dimed, it's close to unity volume (sounds quieter than unity when i run it through a practice amp, maybe a little higher through a bigger amp).

Searching around, I see that it's common practice to dime the volume on these to get it loud enough, so I know it's not a circuit that's going to blow heads off, but I'm not convinced it's putting out what it should. I'd love to run a signal into it and scope the output to know for sure, but I don't have the knowledge to look at the schematic and understand what the total gain should be. Can anyone help? If, for example, I hit the input with a 100mv sine wave, what amplitude can I expect at the volume pot?

Thanks!

[Mark Hammer]

A 33k fixed resistance going into a 50k volume pot is not going to get you very much output.  This seems like the same issue that plagued the MXR Distortion+, which started out with a 10k resistor going into a 10k volume pot.  You couldn't get much output unless you dimed the thing.  However, change the Dost+'s volume pot to 100k and the lights went on.

Try lower those 33k resistors to maybe 10k and see if that helps, or perhaps increase the value of the output volume pot.

[drummer4gc]

Thanks Mark, I'll play around with that. I've done it with a Dist + and it makes it way more useable.

I'm still curious to figure out if I'm getting all the signal I ought to be out of the rest of the circuit. Just want to make sure it's all operating as expected so I'm not masking a problem by playing with the volume pot.

Thanks!

[DIY Bass]

If you have a look at a spice program such as LTSpice you can put the schematic in and simulate the circuit, so you could in fact put a virtual 100mV sine wave into the input and measure the virtual voltages and waveforms anywhere in the circuit that you like.

[Mark Hammer]

Thanks Mark, I'll play around with that. I've done it with a Dist + and it makes it way more useable.

I'm still curious to figure out if I'm getting all the signal I ought to be out of the rest of the circuit. Just want to make sure it's all operating as expected so I'm not masking a problem by playing with the volume pot.

Thanks!

I'll note that we have collectively identified a few errors in Maestro "factory" schematics in past.  I don't know that this is one such example, but the possibility exists.  And just because it may be glued to the bottom plate on an actual pedal doesn't get around that.  It's not like Maestro had a team of 50 people dedicated to checking and rechecking schematics before public release.