I built my reverb pedal last week and used it with my acoustic for the first time in church today. I'm really impressed with the pedal but I also noticed a distinct volume drop when I switch it in. I unfortuntaely don't have a signal generator and scope to test it accurately but I rigged up a simple chain - acoustic in to reverb pedal - and measured the output of the pedal with a digital multimeter when the guitar was strummed. With the pedal off, the meter recorded 35-40mV. With the pedal on, the equivalent reading was 25-30mV. So the overall pedal circuit gain is less than unity. I should perhaps mention that like other builders I substitued R14 with a pot (47k) and adjusted to give the amount of reverb I wanted. It ended up set at about 7k. I don't, however, think that this accounts for the less than unity gain overall.
To correct the gain back to unity, I guess that we need to increase the gain on either the input stage op amp (IC1a) or the output stage (IC2a) by changing the feedback resistor. The obvious choice is to change R25 (33k) on the output stage but this is locked in by "the brick". So before I start hacking my circuit board, I'm interested to hear if other builders apart from Lyle also have this problem.
It's been too many years since I studied op amp circuit design so I would appreciate advice from anyone more familiar with the subject on what to change to get unity gain on the overall pedal. Perhaps BYOC's designer could advise.
As an aside, I compared the pedal with the real Belton spring reverb in my Trace Elliot TA60CR acoustic amp and with all the reverb pedal controls set at 12 o'clock, I really couldn't tell the difference but of course, the pedal is more versatile. If I can just sort out the unity gain issue, I'll be absolutely thrilled with the pedal.