PS Audio 200C connection question

[ddrjboo]

I just acquired a beastly PS Audio 200C amplifier without a users manual. Google searches have pointed out that these units were recalled in the 80s because of they could catch fire. My research indicates the fire hazard resulted from connecting a preamp that has DC at it’s output to the directly coupled RCA inputs. These amps have two inputs. Directly coupled (DC) and alternative capacitor coupled (AC). For safety, I read that if you don’t know if your preamp has DC in it’s output you need to connect to the AC inputs of the amplifier, resulting in some decrease in quality of the amplifier output.
One question I have is what level of DC output from the preamp is OK? A couple of millivolts?? Absolute “0” millivolts?
Second question is, does anyone out there have a copy of the user manual??

 

[ddrjboo]

Hoping someone that missed this thread can help me out!

 

[chazix]

Hoping someone that missed this thread can help me out!

Web lore indicates that the power amp has a voltage gain of about 30.8X (1.3V in for, I assume, 40V out). So if you wanted to keep DC at the power amp output to, say, less than 100mV, then the preamp's DC offset needs to be less than about 3.3mV. Of course, the smaller the preamp's offset, the better.

If you go to measure the offset at the preamp output, let it settle at least a few seconds before measuring. It would make sense to put a realistic load on the preamp outputs, too, perhaps something like 50 Kohms.

You probably already know that you should power up the preamp and let it settle a few seconds before powering up the power amp; and when shutting down, shut down the power amp first.

Can't help with an owner's manual. (All the aforegoing is just based on best practices, plus what I could find about the power amp's input sensitivity.)

chazix

 

[ddrjboo]

Thanks for your response! Will a dummy load cause the DC output of the preamp to go up?
I also read something online (so in must be true) about the 30.8 voltage multiplication.

 

[chazix]

Will a dummy load cause the DC output of the preamp to go up?

No, I don't see any way that that would happen. The main idea is that, if the preamp has a coupling capacitor right at the output, you want the DC voltage (if any) across that capacitor to settle to its steady-state value before you measure the output offset.

 

[hjames]

https://www.psaudio.com/pauls-posts/back-in-the-day/

maybe you could just ask Paul McGowan directly for a PDF of the 200C manual ??
He seems like a pretty accessible guy ...

 

[ddrjboo]

https://www.psaudio.com/pauls-posts/back-in-the-day/

maybe you could just ask Paul McGowan directly for a PDF of the 200C manual ??
He seems like a pretty accessible guy ...

Hello Heather! Thanks for the post. I have already sent him an inquiry but haven’t received a reply. If I do I will post it here.

BTW. I’ve recently acquired this amp and another that put out 200 wpc, but they are huge compared to the Carver. Amazing how much output Carver gets out of such a compact package!

 

[hjames]

I got a pair of Von Schweikert VR4 speakers a couple years back. They were long since out of production, and have a black enamel finish.
I wanted to strip the paint off the top and bottom panels (the sides are open cloth) but could not figure how to get them apart.
So I wrote Von Schweikert, asking for an owner's manual, and actually got a reply from Albert himself!
You never know how these things will turn out.

I have a monster Harman Kardon Citation 22 downstairs that is huge, a midsized B&K 202+ and the Carver TFM-25 - they are all around 200w/ch
- it IS interesting the size difference between them!

Hello Heather! Thanks for the post. I have already sent him an inquiry but haven’t received a reply. If I do I will post it here.
BTW. I’ve recently acquired this amp and another that put out 200 wpc, but they are huge compared to the Carver. Amazing how much output Carver gets out of such a compact package!

 

[ddrjboo]

My Eico HF-85 had 0.1 mV of DC output and my Moscode Minuet had 0.3 mV. I suppose it's fine to use the DC inputs on my 200C!

 

[ddrjboo]

I received this email from PS Audio today:

I talked to Paul about this (the CEO and lead engineer at the time), and he says although this wasn't a recall - you should be advised to not plug or unplug anything while the unit is on.

Other than that, you're all good.

Let me know if you need anything else at all.

Best Regards,

TJ Tomasetti | Customer Service Representative

They also provided me with a PDF of the user's manual!

 

[vsat88]

@ddrjboo would you do me a huge favor and send a copy of that manual to me ? Thanks.

 

[ddrjboo]

Hello @vsat88 .
I sold my 200C about a year ago, and I didn't keep a copy of the user's manual. Sorry. I'm sure PS Audio would send you a pdf of the manual if you ask. Their email address is:
support@psaudio.com
If you would rather call them, the number is 800-PSAUDIO.
They have excellent customer service so I am confident they will help. Please feel free to ask me anything else as well. I'll answer anything I can.
Does your 200C have the mod with the DC protection feature? Mine did not. Also as you may have read, mine had an annoying low hum. If not for that I would still have it. It sounded excellent at higher volumes. Oh, and the blue spark and clack on start up was fun!

 

[vsat88]

Hello @vsat88 .
I sold my 200C about a year ago, and I didn't keep a copy of the user's manual. Sorry. I'm sure PS Audio would send you a pdf of the manual if you ask. Their email address is:
support@psaudio.com
If you would rather call them, the number is 800-PSAUDIO.
They have excellent customer service so I am confident they will help. Please feel free to ask me anything else as well. I'll answer anything I can.
Does your 200C have the mod with the DC protection feature? Mine did not. Also as you may have read, mine had an annoying low hum. If not for that I would still have it. It sounded excellent at higher volumes. Oh, and the blue spark and clack on start up was fun!

No, mine has the newer relay . It's a 200 cx. I had an original 200 c as well. Sold it to a friend that wanted it after a re cap. I would really like to know how they set bias on these. And yes, both of them had the daughter boards underneath the driver boards. I would like a solid state relay , to be able to set bias as per factory specs, perhaps a relay DC protect on the outputs.. Thanks for getting back with me. Oh, mine has little to no transformer noise. Crossing my fingers there but there is somewhat of a fix I have heard about. Taking the copper around the transformer off.

 

[ddrjboo]

The materials they used in these were top notch. I've never seen so much copper in an amp before. I'm pretty sure the user's manual doesn't have bias settings in it, but maybe PS Audio would send you a copy of the service manual. It doesn't hurt to ask.
Good luck!

 

[vsat88]

Yeah, that's the thing. They told me they had nothing on it.. It does exceptionally well as is. Just checked the DC offset and it's almost unmeasurable. Thanks friend !