Mastersound Compact 845 with Pvsane 845T


I own a Mastersound Compact 845 and Mastersound PH5 Pre Amp and orderd two Pvsane 845 T Valves.I was advised by the valve supplier that they would work ok as they were the top of 845 range of valves.I was then advised by my dealer that a mod had to be done to the Cathode Resistor on the Compact 845 to take account of the voltage increase.Otherwise the uit could in the future fail.Any body out there using the 845 T in the compact without modification to the resistor should be aware of this .Any comments welcome
patal
Why doesn't someone simply ask Mastersound to provide the Compact 845's operating specs for the 845 tube???? I know of a couple of Mastersound owners who use the Shuguang 845B tube which has the same operating specs as the Psvane 845.

Is the Mastersound Compact 845 shipped with standard Chinese 845 from Shuguang?
HI All,
This gets a bit more complicated,I recieved a e mail from mastersound which advised the only way they could advise on the value of the resistor as a mod for the 845t was if they physically had the valve so a engineer could do the required checks.
I dont see that to be rocket science and would have thought they would or could do this quite easily.Even then they stated that it could not be a definite solution in regard to determining the exact value of the resistor.
One would have thought it would be in their customers interests to go down this path and advise customers bearing in mind the PVsane 845T is a god valve and likely wanted to be used by mastersound 845 Amp owners .
If that was not enough I got home last night and was watching TV when the PH5 Pre Amplifier switched on by itself.I thought I had ghosts.checked the on off switch this was okay reconnected the power with the switch removed it still came on.There was a small LED flashing on a circuit board on the same side of the switch.
Both amps are going back to mastersound for repair.It never rains but it pours.Anybody know of a Valve P0wer Amp which would be as good as the Compact 845 which is integrated.going to keep the PH5 when fixed
HI Brf
Sorry for not anwsering your questions .The 845 compact is shiped with standardc 845 Shuagang valves.The shuagang 845B is somewhat different to the 845T hence the need for the mod.Albeit the 845B is compatible with the compact 845 without any modifications.
Re operating specs you are quite correct but I find it very difficult to get detailed information from them.I think this is caused to a considerable extent by the language barrier.They should suply it withe the operators manual which is also scant in this regard.
Brf, the first responder to the OP, is correct. The 845-T operates to the RCA/Amperex spec, as does the stock 845A tube, and the B. Every Mastersound Compact 845 amp I've ever seen shipped stock with the prosaic Shuguang 845A, a cheap'n'cheerful power tube. 845-T is a drop-in replacement for 845A and 845B, but it is not a clear improvement over 845A, while 845B generally is. If for some reason you don't want to use 845B, consider the cryogenic 845A sold by ATSI.

Precise bias is desired, but these SET amps have enough latitude to allow drop-in replacement for RCA-spec tubes. If you want to address tube-to-tube inconsistency, then sure have a tech install the right resistor. But doing so is prompted by wanting to address inconsistencies rather than an intrinsic incompatibility with the 845-T. My guess is Mastersound's techs in Europe have no experience with the 845-T and are reluctant to endorse a tube substitution they haven't previously tried.

Phil
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