Bitmo Mod Kit for AC4

[Olsson]

Hi
If the 12AX7 has a gain of 100, the 12AT7 has 60 and the 12AY7 has 45. I think both of them is to recomend, but Dave, if You have the possibility to try 12AY7, I am very interested to here Your opinion. I have tried to contact Roger, but I have not got any answer. have someone heard from him lately ?
/Bertil

[rogera]

Hello Bertil - I have seen no message from you recently. How did you try to contact me?

I do still build EF86 pre-amps by request (depending on what amp they are to be fitted to).

[dave robinson]

Hello Bertil - I have seen no message from you recently. How did you try to contact me?

I do still build EF86 pre-amps by request (depending on what amp they are to be fitted to).

There you go, you will not get better than this.

[Olsson]

Well thats good news ! I have sent a personal messages on Charlie Halls site. Can You send me a mail: bertil.olsson"at"hotmail.se, replace "at" with @. And Dave, I believe You.
/Bertil

[Twang46]

I fitted one of these a while back out of curiosity & tend to agree with Dave that the valve used (Phillips at7 is a big part of the "sound") having some similarities to the ef86

The 2 switched tone settings are just that & could be better covered by fitting a full set of tone controls but for a simple improvement that is easy to fit I think it is reasonable value even with the savage implementation of vat from £15 on USA imports that then includes postage & a "handling charge" from the courier.

I did not use a kit but just used stuff I had lying around + a valve at about £13 I think

A more important mod (for me) is to reduce the "hum" & throw away that useless power switch thingy replacing that with a VVR (power scaling) in it's place.

For less than £35 in parts (+ labour charges if you need to get someone to do the work for you) makes the standard AC4tv (h) a very nice amp indeed

Dick.

[dave robinson]

Been playing some more and starting to like the subtle differences in the tones on offer.

[Billyboygretsch]

A couple of weeks on any changes to initial thoughts ?

[dave robinson]

Yes I like it and use the three different settings for different things. I sold my other AC-4 as I no longer need it.

[AlanMcKillop]

Would this valve from Watford Valves RFT Cryo / ECC81/12AT7/RFT-CRYO , be a suitable replacement for an AC4TV?

[rogera]

In view of the fact that no valves in the 50s or 60s were ever given cryogenic treatment I believe that you would be wasting your money Alan.

This treatment for valves is quite recent and in my view an opportunity to make money using 'smoke and mirrors'.

The ECC81/12AT7WC Philips that they stock would do just the same thing at a saving of £5 (probably better to make the saving before the 18th though whilst you still have the pound !! )