Superphon Revelation MK II PreAmp

[yeoldestereo]

Recently the Superphon Revelation MK II preamp has come my way. Was designed and built by Stan Warren, at one time the other half of PS Audio. Cant' find out much about it though. Performance wise a very good preamp, phono section exceptional.

However the Volume and Balance pots are quite pedestrian and should be upgraded. I have in the parts bin a TKD 25Kohm volume pot. Anybody know if this would be of correct value? Any other help greatly appreciated.

[analog_sa]

Originally posted by yeoldestereo
Anybody know if this would be of correct value?

Too scared to open it and check? How did you find out the pots "are quite pedestrian"?

[yeoldestereo]

Yep Charles did open the unit. The volume and balance pot are quite generic, akin to Radio Shack parts. Current parts show no value on them. Thanks for the response.

[Panelhead]

I had a Rev 2G back in the late 80's. It was a very nice preamp, but mine suffered from a low level buzz. Suspect grounding, but muting the unit would make it dead silent.
I think mine had 50k pots. It was dual mono, no balance. I would rewire the unit and go dual mono controls.
The preamp was very nice, low level hash was not that bad. I think today I could sort it out. Sent it back and they said it was silent, so it was most likely one of my sources caused it.
To check yours, only measure the volume control. The three pins are in-out-ground. Measure the two outside pins to find impedance of pot. I would ditch the balance.
If it is a 50K control, get two 100k stereo log taper controls. Parallel the two sections. This should track a little better and with two wipers should be a little quieter.
The value of the pot is not critical. Just get it in the same ballpark as the original.


George

George

[beeger]

I have already sent Ye Olde Audio Fan a note, but for the sake of clarity to other viewers of this subject I will attempt to explain a few things. The controls in the Rev II were custom made by Alps. We auditioned several of their pots and found the 16MM metal enclosed units to have about the same grain as the larger and more expensive square bodied types, with a more open and spacious sound stage. The problem was tracking. The best case channel to channel match was about 2 dB and some were worse. We paid a small surcharge and bought a thousand units with less than one dB error. At least, the ones we checked met that spec! Of course, Alps wanted around 24-26 weeks to build them and that was kind of a pain. Still, what are you gonna do? We got a better sounding control with good tracking and it cost about half of the bigger and darker sounding ones from the same company. The balance control is more or less a standard unit from Alps with resistance elements that are metal from one side to the twelve o'clock position. Thus, if you have the control at top center there is no resistance in series with the signal and if you turn the balance to one side, only the attenuated side gets a little resistance inserted. We did do an A-B test and no one in the shop at the time could tell which units had dual mono volume and which were volume/balance. Not much has changed since then. Beware of expensive controls with great specs, most did poorly in a blind test. These last few years, I have been very impressed by the Mouser/Alpha 24 MM units sold by Mouser Electronics. They are not great trackers either, but at less than three dollars for a stereo unit you can buy a few of them and use the best one. Of course, YMMV

[Panelhead]

Those cabon Alpha pots ae prime candidates for converting a stereo to mono. Even if you cannot tell a stereo and balance control from dual mono by listening, the dual mono takes tracking out of the equation.
The Superphon gear was noted for having wimpy power supplies, cheap RCA jacks, and now controls. But they did sound and operate very well for quite reasonable money.


George

[eeeehaw]

I have a Superphon Revelation II preamp (s/n 2520F) that's served me quite well since 1984ish. But now the Play/Mute relay has gone bad, contacts have degraded and adds a lot of noise to the signal, particularly in one channel. I have confirmed that the relay itself is the problem.

However, I can't find a source for the relay. Its blue plastic housing is marked with p/n "OUB-SS-212D" and "ES Taiwan". Anyone have ideas on how to locate, or substitute equivalent, part?

[KBK]

sounds like standard 8 pin 2 contact (Silver contacts) 12V relay.

common as grass.

[eeeehaw]

Au contraire. It would have been great if Superphone had used a "conventional" relay. This is an unusual relay. Altho its pin spacing is standard, and uses a common PCB-mount configuration of 8 pins of standard 16DIP dimension, the pin-out is non-standard. The 12VDC coil is on pins 6 & 12, instead of 1 & 16, and the commons of the relay switches are on 1 & 16.

Certainly, there are several choices of low-signal PCB relays available with similar coil current and sensitivity, but they will require re-drilling the PCB board in an open space, gluing it on, and then hand-wiring it via soldering directly to the pins and the original PCB pads in the correct locations...something I'd like to avoid if there's a drop-in replacement. Instead of grass, this one looks to be a rare orchid.

[beeger]

Twenty years ago, this was a readily available relay. My how the years do get by.... Email me and perhaps I can help you with a replacement.