Ever since the original AST, the Swart Reverb has been an integral component to the overall Swart sound. We opted for the tube and spring tank solution for the most authentic and natural reverb take and we have not veered from this approach from 2003 to 2022.

Here are a few things to help with your understanding of the Swart reverb as well as trouble shooting any issues that might crop up.

Stock Reverb Tube

JJ ECC832 (12DW7)
(NOS 7247 SUB)

The reverb circuit is usually something YOU can take care of without need for tech support. 99% of any issue is a matter of plug & play replacement. Simply put, it's usually either TUBE, TANK, or RCA Cables, all inexpensive and easily replaced.

     REVERB TANK *Stock

*MOD 8FB3C1B (Long Decay)
      MOD 8FB2C1B
(Medium Decay)

INPUT IMPEDANCE.....1925 ohms

Not only is it generally all serviceable by the end user, it's really inexpensive if ever an issue and out of warranty.

There is a simple test to suss out the culprit. It's usually the reverb TUBE or TANK, closely followed by an issue with the RCA cables that connect the tank. All of these are easy replacements.

Try to rule out the RCA cables. Also, make sure they are fully seated and a tight connection (sometimes, removing and bending outer flanges in of plug will help tighten contact).

ALSO IMPORTANT: RULE OUT the Footswitch by unplugging from amp.  Your reverb WILL WORK without the FS connected.

RCA cables good...try this below.



  • Turn the reverb up to 11

  • Shake the amp, and listen to see if you hear the springs through the tank. Note result.

  • Now, swap the RCA cable leads and shake it again.

    If you hear the springs one way and not
    the other, than it's most likely the tank.

    If you hear it BOTH WAYS,
    it's most likely the 12DW7 tube.

    Note: On the early older amps, with a bad knock,
    there can be issues with white push on connectors.
    Sometimes cleaning and re-seating can fix.

HUM an issue?

While there will always be a trace of hum, if noticing some excess, one quick trick might be to reverse the RCA leads. There will almost always be one orientation that is quieter than the other. To find BEST, simply try both ways. Whichever is quieter is correct orientation in your amp.

This also handy if you ever remove cables and forget orientation. Simply test which has least noise/hum.

There will always be slightly more hum in the smaller heads due to closeness of tank to transformer.

And if you are unsure of any of this, you're always free to drop us a mail or call.

Below are the three main components that you will address if an issue.


JJ ECC832 (12DW7) Reverb Tube

This is a dual triode that is unusual in that one side is a 12AX7 while the other side is a 12AU7. That is literally the most gain (12AX7 side) and least gain (12AU7 side) of the minipin 12A*7 tubes, To give you an idea, the 12AU7 is literally 18% of the gain of the 12AX7. One side pushes the reverb drive and the other side the reverb recovery. These tubes are usually pretty reliable, however they CAN have an issue and cause some strange symptoms. This is the first thing to check with a reverb issue. IF you do NOT have a spare 12DW7, a 12AX7/12AT7 is completely fine to TEST circuit to see changes. Subbing 12A*7 tubes does no harm, just not the designated tube for circuit. Of note, the default 12DW7 for us is the JJ ECC832.  This has been our stock tube due to ease of sourcing since day one (pre-pandemic-Putin).  Of note, there is a NOS version, the 7247, that actually can sound quite amazing though they are far harder to find and more expensive for sure.  If you happen to prefer, say, a nice 12AT7, or any other 12A*7, feel free to use with knowledge JJ option is our usual choice. . 

MOD 8FB3C1B Tank (Long Decay)

...............1925 ohms
OUTPUT IMPEDANCE...........2575 ohms

Ever since we ran out of our big stash of vintage Accutronics tanks way back in the late mid 2000s, this has been our go-to reverb tank. Yep, it's the MOD 8FB3C1B and it's a short tank that fits ALL the amps. It sounds a lot bigger than it looks, which is one of the reasons we like this little beast. It's pretty reliable and inexpensive to replace if ever an issue. It's an overachiever and has some nice character to the response, too. However, there are a few that do prefer the MEDIUM DECAY tank. Everything is the same except a shorter decay time of 1.75 - 3 seconds verses 2.75 - 4 seconds for the long. Note, it's important to match the input & output impedance with any tank sub.




MOD 8FB2C1B Tank (Medium Decay)

Occasionally, someone does prefer the medium decay tank if the splash seems a bit too long. This is a drop in replacement. Some get both just to experiment and since most of the tanks are floating in the tank bag, no mounting is involved. The dimensions and specs are the same aside from the decay. You'll notice the one number difference in model with a 2 in place of the 3.


RCA Cables

A pair of RCA cables carries the send and receive signal to and from the circuit to the reverb tank. Later cables were a bit more heavily shielded and are somewhat quieter though I personally still have the more traditional gray sets in my amps and do not have any issues. But it's important to rule out the RCA cables as a potential issue. The amp side is obviously easier to access than the tank side due to bag. One thing to be aware of, you can tighten the grip of the connection on RCA jack by lightly bending in the outer tangs of the RCA plugs. Make sure the plugs are fully seated on the jack

Reverb Tank Bag

In most every combo, we employ a reverb tank bag to house the tank. For a while, we did directly screw the tank to the cabinet but after comparing the two methods, the amps with the tanks in the bag seemed to have less of a mechanical harsh take, sounding somewhat sweeter and smoother. So we opted for the bag in the combos. If your combo does not come with the bag, it's also available for purchase. The tank is literally FLOATING within the bad, unattached aside from the RCA cables that connect tank to amp chassis.

©2022 swart amp co.       2031 wrightsville ave wilmington nc       910.620.2512



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