I don't know if I'm at the right place, but I need help !
I found a keyboard amp at pawn shop for really cheap this week. The amp is an old Stage (univox) 720k, solid state, from the mid 70s. Everything is working perfectly but the reverb tank is missing. By the look of the amp it's easy to tell that it's been in a lot of shows and the previous owner must have removed the reverb tank.
So, how can I determime what reverb tank I must put in it ? There's no information at all on internet about that amp. I found the schematics here :
http://www.schematicsunlimited.com/u...fier-schematic
but it's not really helping me. Is there a way to calculate the proper impedance the reverb tank should have ?
I found a keyboard amp at pawn shop for really cheap this week. The amp is an old Stage (univox) 720k, solid state, from the mid 70s. Everything is working perfectly but the reverb tank is missing. By the look of the amp it's easy to tell that it's been in a lot of shows and the previous owner must have removed the reverb tank.
So, how can I determime what reverb tank I must put in it ? There's no information at all on internet about that amp. I found the schematics here :
http://www.schematicsunlimited.com/u...fier-schematic
but it's not really helping me. Is there a way to calculate the proper impedance the reverb tank should have ?
Commercial spring reverb units just about ALL have the same or similar output impedance, so that choice is essentially made for you.
The input end, where the drive signal goes, the end connected to Q11, comes in a variety of impedances. Since this is driven through a cap off the collector of Q11, you want the highest impedance on the list. The actual impedance number isn't important, the amp won't care if it is 1500 ohms versus 1800 ohms or whatever.
Accutronics uses a number system that specifies impedances, among other things. A typical reverb pan has a number like 4EB2C1B. You can go to Accutronics web site and look up all the data. But the second and third characters tell the impedances, in the example, the E and B. The E is the input and the B the output. They will almost always have the B output. Fortunately the other brands of reverb unit mostly use the same or similar number system.
In my example the second character was E. They range from A through F. A is low impedance, like 8 ohms, while F is the highest, I forget just what. You would want an FB type pan. An EB might work, but the FB would be preferred.
I don't know how much room you have. The first digit describes the physical size. The 4 in my example means a full size pan, about 17" long. It has two long springs inside. There is also a 9, which is the same size, but with three long springs. For tighter spaces, there are also smaller ones, starts with an 8, maybe 8-9 inches long. Other than shape, the two sizes are interchangeable.
The other numbers and letters matter, but less so. And when you go to someone who sells them, you will only have a couple to chose from. So once you decide on th 4 or 8 size, if you look down the list for 4FB or 8FB there will probably only be one on the list. It will work. All we need do then is make sure we wire it in right.
Reverb tank and reverb pan mean the same thing.
Here is an example:
https://www.tubesandmore.com/products/P-RMOD-4FB3A1B
The input end, where the drive signal goes, the end connected to Q11, comes in a variety of impedances. Since this is driven through a cap off the collector of Q11, you want the highest impedance on the list. The actual impedance number isn't important, the amp won't care if it is 1500 ohms versus 1800 ohms or whatever.
Accutronics uses a number system that specifies impedances, among other things. A typical reverb pan has a number like 4EB2C1B. You can go to Accutronics web site and look up all the data. But the second and third characters tell the impedances, in the example, the E and B. The E is the input and the B the output. They will almost always have the B output. Fortunately the other brands of reverb unit mostly use the same or similar number system.
In my example the second character was E. They range from A through F. A is low impedance, like 8 ohms, while F is the highest, I forget just what. You would want an FB type pan. An EB might work, but the FB would be preferred.
I don't know how much room you have. The first digit describes the physical size. The 4 in my example means a full size pan, about 17" long. It has two long springs inside. There is also a 9, which is the same size, but with three long springs. For tighter spaces, there are also smaller ones, starts with an 8, maybe 8-9 inches long. Other than shape, the two sizes are interchangeable.
The other numbers and letters matter, but less so. And when you go to someone who sells them, you will only have a couple to chose from. So once you decide on th 4 or 8 size, if you look down the list for 4FB or 8FB there will probably only be one on the list. It will work. All we need do then is make sure we wire it in right.
Reverb tank and reverb pan mean the same thing.
Here is an example:
https://www.tubesandmore.com/products/P-RMOD-4FB3A1B
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