EQD Hoof Reaper clone : AC176 substitute and Volume loss issue.

[eh la bas ma]

Hello,

My last build is an Hoof Reaper clone made with a musikding kit. Hoof Reaper is a 3-in-1 Tonebender, Octave up and  a BIg Muff variant.

https://docs.pedalpcb.com/project/WarScythe.pdf

Everything sounds fine, all controls are working.

I only noticed one obvious issue : If i just use the Tonebender and if i activate the octave, there is a noticeable volume loss, between 5 or 10 db i think.

No volume loss with the Muff section when i activate the octave, this issue only happens with the Tonebender.


Instead of 2N1308 for Q4 & Q5, i have a pair of BC107A. But that's in the muff section.

The transistors in the tonebender are an MPSA18 and an unknown transistor, marked MП38A 9005. I guess it's an MP38A. The build doc calls for an AC176.

In my stash i have AC122, 90-99 hFe and AC125, 110-120. Or EFT83, 60-70 hFe.

I wonder if the volume loss with the octave could be related to the transistor substitution in the Tonebender section ?

Is MP38A a suitable sub for AC176 in this application ?

Edit : i am using this stompbox with a long signal chain. There are several other effects, including a compressor and a few buffered effects (MXR stereo chorus, GE-7, BD-2, etc.).

If i connect the Hoof Reaper in the first position, the volume loss from the octave's activation disappears, but the Tonebender on its own sounds very compressed on full chords. If i just play single notes it sounds normal, but there is a volume loss on full chords. I play with active double hambuckers Seymour Duncan pickups.

If i put back the Hoof Reaper after the compressor, a Meatball and a BD-2, all switched off, the Tonebender sounds ok on full chords, and the volume loss is back when i activate the octave... Isn't it strange ?

I wonder if there is something wrong with my build, or if this Tonebender and octave combo are just very sensitive to their location in the signal chain ?

Every observations and suggestions are welcome !

[eh la bas ma]

Here are a few pics in case someone can spot something wrong or suspicious :












Voltage readings are coming...

[eh la bas ma]

DC 9V+ = 9.47 V


ToneBender :

Q1 MPSA18

E= 184.4 mV
B= 0.8 V
C= 3.6 V

Q2 MP38A

E= 100 mV
B= 171 mV
C= 7.76 V



Octave

Q7 2N5089

E= 1.4 V
B= 1.9 V
C= 5.19 V

Q8 2N3906

E= 5.83 V
B= 5.19 V
C= 3.3 V

Q9 2N5089

E= 3.7 V
B= 4.32 V
C= 9.23 V