WTB: Gotham amps

[MrMegaEli]

Hi all,
I am looking to buy a pair of Gotham amps. I know they are used with a Grampian head, but I want to try modifying them for my Westrex 3D. Get in touch if you have just one, or a pair.

[dubcutter89]

Hi!
I cannot speak from practical experience with gotham/westrex setup, but I'm not sure if this is a good idea.

1. The Gotham amp was designed for the Grampian head -> afaik the feedback loop has a dominant pole in the middle of the audio range! You would have to remake this and I'm not sure if the amp will work stable afterwards...

2. The Grampian head has a much hotter feedback signal -> you would have to make a feedback preamp stage. Also you would have to make another RIAA stage for monitoring if you want to...

3. Drive Coil Impedance -> well, probably no problem

4. Cutterhead EQ -> The Westrex head has no flat frequency response -> You would have to make another EQ for getting it flat.

I don't know the reason why you want to do this (do you need more output power??) , but it might be easier to make a "new" system from scratch or to modify a westrex/haeco than to modify the gotham amps....

Just some thoughts...

Lukas

[dubcutter89]

...but maybe it's a great idea, or at least quite unique undertaking!

Go for it

[MrMegaEli]

Hi!
I cannot speak from practical experience with gotham/westrex setup, but I'm not sure if this is a good idea.

1. The Gotham amp was designed for the Grampian head -> afaik the feedback loop has a dominant pole in the middle of the audio range! You would have to remake this and I'm not sure if the amp will work stable afterwards...

I'm not sure I know what you mean

2. The Grampian head has a much hotter feedback signal -> you would have to make a feedback preamp stage. Also you would have to make another RIAA stage for monitoring if you want to...

Yes, the 3D FB signal would need to be amplified

3. Drive Coil Impedance -> well, probably no problem

4. Cutterhead EQ -> The Westrex head has no flat frequency response -> You would have to make another EQ for getting it flat.

Yes, I would need a head EQ built in. Switching to a Neumann style torque tube would make this much more manageable.
I don't know the reason why you want to do this (do you need more output power??) , but it might be easier to make a "new" system from scratch or to modify a westrex/haeco than to modify the gotham amps...

Westrex tube amps don't have enough power to cut a loud record, like the 1700

Why? Because it's a good project! I am interested in hearing how this would sound, and the only way to do this would be to take on the huge project of making this work

Just some thoughts...

Lukas

[uvoscillator]

What is the street price for it ?
I cut on Grampian D so also interested to try with original amp.

[MrMegaEli]

Let me know what you have.