Spring Reverb
Spring reverb is a great effect. I wanted to add it to the Princeton-AOT. The P-AOT already has effects in/out connections, so I just needed a small inexpensive reverb unit I could mount in the cabinet. The bottom of the combo cab is empty so there is plenty of room for both a spring pan and electronics. A tube reverb unit needs power supplies and transformers and that all adds up to space and cost.
Spring reverb is a great effect. I wanted to add it to the Princeton-AOT. The P-AOT already has effects in/out connections, so I just needed a small inexpensive reverb unit I could mount in the cabinet. The bottom of the combo cab is empty so there is plenty of room for both a spring pan and electronics. A tube reverb unit needs power supplies and transformers and that all adds up to space and cost.
If you look around, most amps these days use opamps to drive reverb tanks. I decided to go "old school" and use plain old transistors. Transistors provide more drive than most opamps, so this circuit can use the same 8-10 ohm pans that are proven performers in old fenders. Those 8 ohm pans can sound great and there are lots of them around. I opted for a short pan due to space constraints. It fits better and it has three spring paths instead of just two, as found in many longer pans. Three springs gives a better (more dispersed, less correlated with the input) sounding reverb, IMO.
If you look around, most amps these days use opamps to drive reverb tanks. I decided to go "old school" and use plain old transistors. Transistors provide more drive than most opamps, so this circuit can use the same 8-10 ohm pans that are proven performers in old fenders. Those 8 ohm pans can sound great and there are lots of them around. I opted for a short pan due to space constraints. It fits better and it has three spring paths instead of just two, as found in many longer pans. Three springs gives a better (more dispersed, less correlated with the input) sounding reverb, IMO.
The simple circuit below drives any 8-10 ohm pan. The system is setup to work with my P-AOT preamp, but it's also likely to work with any effects loop. The circuit is optimized for a single 24V DC power supply. You could run it on 18 or even 15V, although you won't be able to drive the pan as hard. A 24V supply can drive the pan at slightly over its rated spec - which is fine since harder drive doesn't hurt it or cause distortion. More drive also leads to more signal at the pan output, which means that the hum and hiss levels are lower at the output (better S/N ratio). The P-AOT amp uses a 24V supply, so I tapped that supply for the reverb unit. You may have to get a wall wart or make other provisions.
The simple circuit below drives any 8-10 ohm pan. The system is setup to work with my P-AOT preamp, but it's also likely to work with any effects loop. The circuit is optimized for a single 24V DC power supply. You could run it on 18 or even 15V, although you won't be able to drive the pan as hard. A 24V supply can drive the pan at slightly over its rated spec - which is fine since harder drive doesn't hurt it or cause distortion. More drive also leads to more signal at the pan output, which means that the hum and hiss levels are lower at the output (better S/N ratio). The P-AOT amp uses a 24V supply, so I tapped that supply for the reverb unit. You may have to get a wall wart or make other provisions.
The circuit has greater input sensitivity and output levels than most effects loops require, so add some gain and level pots at the input and output, if you need them. The transistor choices are not critical, Q1 and Q5 can be most any small signal high beta devices. Q2-Q4 need to dissipate some power, so 0.5 or 1 Watt driver transistors are needed. In later versions of this circuit I use TIP29 and TIP30 transistors for Q3 and Q4. They are inexpensive, easy find and the TO220 package is ideal for this circuit.
The circuit has greater input sensitivity and output levels than most effects loops require, so add some gain and level pots at the input and output, if you need them. The transistor choices are not critical, Q1 and Q5 can be most any small signal high beta devices. Q2-Q4 need to dissipate some power, so 0.5 or 1 Watt driver transistors are needed. In later versions of this circuit I use TIP29 and TIP30 transistors for Q3 and Q4. They are inexpensive, easy find and the TO220 package is ideal for this circuit.
The images below show the electronics in a case and the final mounting of the electronics package and the reverb pan in the P-AOT cabinet. A pair of phone-plug cables connects the reverb system to the effects loop jacks.
The images below show the electronics in a case and the final mounting of the electronics package and the reverb pan in the P-AOT cabinet. A pair of phone-plug cables connects the reverb system to the effects loop jacks.
I have to say, this is a very nice sounding reverb and a great addition to the P-AOT package. I used the Alesis NanoVerb2 with the P-AOT amp for about 6 months, but this reverb is the real-deal and it sounds like reverb should.
I have to say, this is a very nice sounding reverb and a great addition to the P-AOT package. I used the Alesis NanoVerb2 with the P-AOT amp for about 6 months, but this reverb is the real-deal and it sounds like reverb should.
Update: 8/30/20
Update: 8/30/20
Since this page was written, I've build and described many similar reverb systems. See the Amp-Aid pages for examples. A new variation is the Solo Verb 3 created for the Solo 100 amp.
Since this page was written, I've build and described many similar reverb systems. See the Amp-Aid pages for examples. A new variation is the Solo Verb 3 created for the Solo 100 amp.