Can a reverb circuit be a loop?

mikemorgan

mikemorgan

panned out
I just bought a Crate V18 112 today on a whim. I was looking for an el-cheepo all-tube? amp to leave at rehearsal. It will probably fit that bill.

It has the worst sounding reverb tank I've EVER heard. It will not survive the night. What exactly gets sent from the output to the tank? Raw voltage? Is it possible to use the in/out meant for the reverb tank as a send/return? I'm sure it's not, but don't know exactly why.
 
No, you can't use a reverb line as an effects loop. The impedance will be completely wrong.


Light

"Cowards can never be moral."
M.K. Gandhi
 
Try this site.
http://www.accutronicsreverb.com/
They probably make a tank that will suit your taste and they have information to help you make the selection. Tanks come in a variety of dwell times and other characteristics. Upgrading the tube that feeds the tank may be a small help. An upgraded tank is cheaper than a pedal and the right tank will sound better than a pedal ever could (IMHO).
 
i'm with light on not being able to use it... but i suspect it's more of a voltage/level problem... and try to stay away from different tubes in that circuit... you really want 12AT7's for that...
 
Interesting stuff.

If I disconnect the tank and decide to live without it, would pulling that tube just disable the circuit, or disable the amp? What do you think? Lose the tube or leave the tube and nail the knob to "0"?
 
Is it footswitchable? Just turn it off. Otherwise, just turn the knob to zero.

It is an impedance issue, by the way. The input impedance on a reverb tank is in the 250 ohms range, guitars are in the 5k-20k range. While it's OK to double or so the load on an output transformer, 20 to 100 times is a bit much. The amount of power in the signal chain for an amp doesn't get out of range for effects until you get to the power amp. It's quite common to simply put an effects loop right before the phase inverter in an amp. It's not a bad idea to put in an isolation transformer, but you don't really NEED it - a cap will do the job, and is probably already part of the circuit.


Light

"Cowards can never be moral."
M.K. Gandhi
 
mikemorgan said:
Interesting stuff.

If I disconnect the tank and decide to live without it, would pulling that tube just disable the circuit, or disable the amp? What do you think? Lose the tube or leave the tube and nail the knob to "0"?
Click to expand...

If you just disconnect the tank, the circuit is disabled because that will open-circuit the output of the reverb driver tube.
 
mikemorgan said:
Interesting stuff.

If I disconnect the tank and decide to live without it, would pulling that tube just disable the circuit, or disable the amp? What do you think? Lose the tube or leave the tube and nail the knob to "0"?
Click to expand...

I have the same amp but with 30 watts, and I actually emailed Crate and asked the same questions you are asking.... the tech said do not disconnect or patch in a different box, say digital delay, because of the impedance issue. Just turn the thing to zero..... maybe have a tech wire in a proper effects loop for you.... other than the verb, those amps are my favorite (I haven't used a spring reverb for years anyways).... I have two of them....I even like them better than my Mesa Boogie I paid 3x the $$ for....

Peace!

~Shawn
 
Light said:
Is it footswitchable? Just turn it off. Otherwise, just turn the knob to zero.

It is an impedance issue, by the way. The input impedance on a reverb tank is in the 250 ohms range, guitars are in the 5k-20k range. While it's OK to double or so the load on an output transformer, 20 to 100 times is a bit much. The amount of power in the signal chain for an amp doesn't get out of range for effects until you get to the power amp. It's quite common to simply put an effects loop right before the phase inverter in an amp. It's not a bad idea to put in an isolation transformer, but you don't really NEED it - a cap will do the job, and is probably already part of the circuit.


Light

"Cowards can never be moral."
M.K. Gandhi
Click to expand...

The impedance of the reverb on some old Gibson amps as well as some others can be as high as 1.8K. The Crate probably is compatible with Fender's 250 but I would verify that before I proceeded. The reverb will use one side of the tube that drives it. the other half may or may not serve another purpose in the amp. Removing it to see what happens shouldn't harm the amp.

Good Luck
 
Thanks for saving me all this time guys. I knew I'd get a wealth of knowledge here, and fast. For $150, I too am loving this amp. I just slammed an old Digitech Legend in front of the input. It has a great compressor, gate, EQ, and all the delays and reverbs you could ever want. I'm pretty sure I'll switch out the speaker at some point, just 'cause I have so many lying around, and I can't wait to burn up these Sovteks for a better string of valves. I wish it had a loop, but I started playing before amplifier effects loops existed, so I'll get over that. Musician's Friend still has these for $150 new, and there's a 2-12 version for $199.
I'm gonna give it a thumgs up!
 
mikemorgan said:
I just slammed an old Digitech Legend in front of the input. It has a great compressor, gate, EQ, and all the delays and reverbs you could ever want.
Click to expand...

I bet that'll be your favorite amp before it's over....

mikemorgan said:
Musician's Friend still has these for $150 new, and there's a 2-12 version for $199.
I'm gonna give it a thumgs up!
Click to expand...

:eek: :eek: :eek: :eek:
I can't believe how cheap these have gotten.... You can get the 30 watt for $250 at MF!!!..... and IMO they blow away any of the Hot Rods or Juniors that Fender is selling by the truckload..... but people won't buy them because it says "Crate" on the outside.... :rolleyes:
 
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mikemorgan said:
Thanks for saving me all this time guys. I knew I'd get a wealth of knowledge here, and fast. For $150, I too am loving this amp. I just slammed an old Digitech Legend in front of the input. It has a great compressor, gate, EQ, and all the delays and reverbs you could ever want. I'm pretty sure I'll switch out the speaker at some point, just 'cause I have so many lying around, and I can't wait to burn up these Sovteks for a better string of valves. I wish it had a loop, but I started playing before amplifier effects loops existed, so I'll get over that. Musician's Friend still has these for $150 new, and there's a 2-12 version for $199.
I'm gonna give it a thumgs up!
Click to expand...

If you really want a loop, replace the reverb tank with a 250 ohm (or whatever the correct value is) wirewound pot that can take the heat (5W or 10W I would think would do, but worth measuring), and set the pot at whatever level you need to for your effects box.
 
Just got one of these as well. I was wondering about adding loop as well. As there is a line out jack, I'll bet it could be very easily modded to have an effects loop. Half the work is already done...
 
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