Modding a reverb circuit

[mr_sooty]

How difficult would it be to covert the reverb on my handwired point to point Dr Z Maz18 amp to be more Fender-ish? Does it just come down to component values or do different amp companies have completely different approaches to generating reverb? It's a tube driven spring reverb.

[Marshmallow]

How difficult would it be to covert the reverb on my handwired point to point Dr Z Maz18 amp to be more Fender-ish? Does it just come down to component values or do different amp companies have completely different approaches to generating reverb? It's a tube driven spring reverb.

Maybe best to try other spring reverb units first. The bigger the unit and more springs they have the more lush they usually sound.. I think...

[MikeC]

How difficult would it be to covert the reverb on my handwired point to point Dr Z Maz18 amp to be more Fender-ish? Does it just come down to component values or do different amp companies have completely different approaches to generating reverb? It's a tube driven spring reverb.

Maybe best to try other spring reverb units first. The bigger the unit and more springs they have the more lush they usually sound.. I think...

It's not quite that straight forward. If you can get the number from the existing tank this will probably help as to what suitable replacements are available.

[mr_sooty]

How difficult would it be to covert the reverb on my handwired point to point Dr Z Maz18 amp to be more Fender-ish? Does it just come down to component values or do different amp companies have completely different approaches to generating reverb? It's a tube driven spring reverb.

Maybe best to try other spring reverb units first. The bigger the unit and more springs they have the more lush they usually sound.. I think...

It's not quite that straight forward. If you can get the number from the existing tank this will probably help as to what suitable replacements are available.

Only thing is the one in there isn't the original one. So it's possible the one I currently have in there isn't the right something something. It works, it just doesn't sound that great, but neither did the previous one. I'll find the number when I get home and also see if I still have the original.

[MikeC]

I just did a little Googling - the correct tank is a 8AB2A1B. What you got?

[Marshmallow]

How difficult would it be to covert the reverb on my handwired point to point Dr Z Maz18 amp to be more Fender-ish? Does it just come down to component values or do different amp companies have completely different approaches to generating reverb? It's a tube driven spring reverb.

Maybe best to try other spring reverb units first. The bigger the unit and more springs they have the more lush they usually sound.. I think...

It's not quite that straight forward. If you can get the number from the existing tank this will probably help as to what suitable replacements are available.

I think it's the ohms of the reverb that needs matching.

[MikeC]

A few other things too - see below...

Char #1 - Reverb Type 4 = Type 4

Char #2 - Input Impedance A = 8 Ohm (White)
B = 150 Ohm (Black)
C = 200 Ohm (Violet)
D = 250 Ohm (Brown)
E = 600 Ohm (Orange)
F = 1,475 Ohm (Red)

Char #3 - Output Impedance A = 500 Ohm (Green)
B = 2,250 Ohm (Red)
C = 10,000 Ohm (Yellow)

Char #4 - Decay Time 1 = Short (1.2 to 2.0 sec)
2 = Medium (1.75 to 3.0 sec)
3 = Long (2.75 to 4.0 sec)

Char #5 - Connectors A = Input Grounded / Output Grounded
B = Input Grounded / Output Insulated
C = Input Insulated / Output Grounded
D = Input Insulated / Output Insulated
E = No Outer Channel

Char #6 - Locking Devices 1 = No Lock

Char #7 - Mounting Plane A = Horizontal, Open Side Up
B = Horizontal, Open Side Down
C = Vertical, Connectors Up
D = Vertical, Connectors Down
E = On End, Input Up
F = On End, Output Up

[RectifiedAmps]

I don’t know what the Dr Z circuit is like, but if it uses a whole 12AT7 through a little reverb transformer to drive the spring tank (ideally a long-spring tank), it should be relatively easy to mod or reconfigure the rest of it to imitate a classic Fender Reverb circuit.

It may actually already be identical to a Fender circuit, but it just differs by where the reverb is placed in the circuit, or by the rest of the preamp circuit around it.

[mr_sooty]

I don’t know what the Dr Z circuit is like, but if it uses a whole 12AT7 through a little reverb transformer to drive the spring tank (ideally a long-spring tank), it should be relatively easy to mod or reconfigure the rest of it to imitate a classic Fender Reverb circuit.

It may actually already be identical to a Fender circuit, but it just differs by where the reverb is placed in the circuit, or by the rest of the preamp circuit around it.

Am I right in hearing that you no longer do this kind of work?

[mr_sooty]

I have a feeling I may have replaced the tank twice, due to feedback or other issues, with little regard to impedance etc. So I have an old tank, but I'm not sure if it's the original, and I can't read the last letter. The new tank I just got from someone here and didn't realise you needed a specific type, have been using for quite a few years.

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So perhaps I just need to get the right sort of tank!

[MikeC]

The new tank is a perfect "fit" for your amp apart from that it has "long decay" over the correct tank's "medium decay". So reverb should be more "washy" with the new tank verses the correct tank.

[mr_sooty]

Oh well that should theoretically be a good thing by sounds of it.

[MikeC]

There could be something wrong of course including a bad reverb send tube, recovery tube or even a dodgy tank. Is the reverb weak?

[mr_sooty]

There was something wrong earlier. I replaced all the tubes, didn't fix it, then found that the reverb control pot was actually faulty, replaced that, much better now. I don't think there's anything wrong with it anymore. The reverb on the older model Maz 18 I have is generally regarded as it's 'achilles heel'. It just doesn't quite live up to the otherwise stellar quality of of the amplifier. It feels like a bit of an afterthought. Other owners of the same amp tend to agree. The good Dr had since upgraded it with the Mark 2 but won't spill on exactly what the changes are.

[MikeC]

There was something wrong earlier. I replaced all the tubes, didn't fix it, then found that the reverb control pot was actually faulty, replaced that, much better now. I don't think there's anything wrong with it anymore. The reverb on the older model Maz 18 I have is generally regarded as it's 'achilles heel'. It just doesn't quite live up to the otherwise stellar quality of of the amplifier. It feels like a bit of an afterthought. Other owners of the same amp tend to agree. The good Dr had since upgraded it with the Mark 2 but won't spill on exactly what the changes are.

I had a look earlier at the Maz 18 circuit (well, hand drawn ones because I couldn't find the factory one) and it was very similar to the Fender Blackface reverb. But after what you've just stated it may have been the MKII circuit. I'll see what else I can find.