Mastersound Compact 845 with Pvsane 845T

Cobra /Phil
Thanks for that,am I right in understanding that the 845 t would be ok as drop in and have no adverse effect on the existing resistors.Plus, that the 845B is better than the 845T. The amps are going back tomorrow for repair can you suggest any upgrade that would be worth doing such as capacitors etc which would be worth while.Might as well have it done while they are in the hands of a competent tech from Jordan Acoustics in scotland.
Thanks Guys

Patal,

Unless something has been done to your amp to make it incompatible with RCA-spec 845 tubes -- and if it's running 845A, nothing has -- you can replace 845A with 845-T or 845B. It may be that if subsequently you had the bias checked, testing might suggest that a precise adjustment to the value of the associated resistors can dial in the amp more perfectly. Maybe. But you're not going to harm anything by that simple change of tubes.

Whether you will think the 845-T is better sounding than the 845B, or not, is your call. I did not find the 845-T to have clear advantage to warrant using it, and in my own experience with the tube and observation by others who have reported results to me, I have to conclude the 845-T is less reliable than the 845B. Others may have a different experience. Other than the B tube, my suggestions for not-too-exotic alternatives are the Sophia 845MkIII, and the cryo'd 845A sold by ATSI. Interesting exotic alternatives include the KR -- likely requiring some changes to the filament supply -- and the super-scarce Elrod; expensive! Or for that matter, go hunting for a pair of NOS RCA or Amperex. Also dear.

The major area for upgrade that I suggest you have your tech investigate is recapping the power supply. The power supply caps have a strong influence on the voicing of vivid tube amp like this, and on its dynamic character. The Mastersound SET amps sound a little "slow" compared to my Audion equivalents, to me, and I think this can be easily corrected by judicious selection of capacitors to recap the power supply, and you can pick up more transparency in the bargain. Certainly while a tech has the amp for repair it is easy enough for him to precisely bias the amp for the tubes you choose, too.

Phil

I agree with everything that Phil wrote especially about new caps. I recapped my 845 amp with both teflon V-Caps which once broken in, offer the amp more speed and transparency. I also tried Mundorf M-CAP Supreme Silver / Gold & Oil caps which offer a very organic rich sound without sacrificing transparency. Two different excellent sounding caps, but in the end I kept the Mundorfs.

Dear Phil

Many thanks for that useful information

Hi Patal, let us know how you get on because I too have a Compact 845 from Jordan, so will be very interest in the outcome

Jonathan.