Princeton reverb has a lot of hiss

[rutledj]

I built the PR based on the schematics at Hoffman Amps. It works well with two exceptions:

1. The amp has a lot of hiss when turned up. Not hum but hiss. Is this normal?
2. The reverb control needs more range. A setting above 2-3 is way more reverb than most people would normally use. I exchanged the 100k pot with a linear version but not much difference.

Appreciate any feedback.

[pdf64]

For better reverb range of control, try a log / audio taper reverb control. Stock is linear.

Regarding the hiss, are you sure the inputs are wired up properly? New builders seem to have problems getting that right.

Another new builder thing seems to be comparing the noise / hiss of their new non master volume build to that of master volume amps they may have; if doing that, turn the master up full CW and select a clean channel.

If you sort yourself out with a signal generator, you can use the RI schematic V AC levels along the signal path https://www.thetubestore.com/lib/thetub ... ematic.pdf

[bepone]

1. not correct grounding despite what most people thunk that grounding creating only humm,
lead dress issue also can create a lot of hiss

2. to cut reverb amount is easy just increase resistor before the reverb pot

[rooster]

Hiss is not typical in a stock PR build. Make sure you have a 10pf across the 3.3M, if you made it any larger than 10pf you will have a problem. This 3.3M bridged with a 10pf cap is actually the clean signal input path to the PI. BTW, the AA763 used 4.7M here and the AB763 used 3.3M, this was a Fender tweek that everyone seems to like as the AB763 circuit is the most popular in the Fender BF range.

As to 'too much reverb' make sure you tubes are correct for the circuit.