PV-1 to PV-2AR conversion

The PV-1 to now...
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supersportsteve
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PV-1 to PV-2AR conversion

Post by supersportsteve »

Hi everyone, this is my first post here. I purchased a nice PV-1 from somebody and they explained that the unit was converted to a PV-2AR by Conrad Johnson in 1984. My first question is do I use the same tube types and layout of the PV-1, or do I use the tube types and layout of the 2AR? I am getting a lot of floor noise, (hiss, and minor hum) and it seems like the gain is really too high. I am currently using the PV-2AR tube types and locations. Any help would be much appreciated.

Thanks!

Steve G.
plurn
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Re: PV-1 to PV-2AR conversion

Post by plurn »

Hi Steve,

Can you tell us about the rest of your system? It could be that you have very efficient speakers and/or an amplifier with high gain. If this is the case, then any hiss or hum will be exaggerated and will be audible in your system.

The gain in conrad johnson preamps is very high by the way. The gain in the line stage of the PV1 is 28dB and of the PV2 is 24.5dB. This is very high gain. Was useful back when sources had low voltage, but excessive for modern digital sources with 2 volt output.

Also, it could just be that the tubes are old. As they get old, they are likely to get tube rush noise (hiss) and possibly hum noise. This is very common and is the first thing you should check (because it is easy) by using some new tubes to compare.

If you are not using the phono stage, you might be able to get away with just changing the line stage tubes to see if that reduces the noise?

Regarding your first question, sorry I don't know. I would think that it should be the tubes specified for the 2AR. You might be able to tell by looking at the tube layout as shown on http://conradjohnson.com/vintage-conrad ... -products/ for both preamps.

The PV1 has three tubes in a column from front to back on the circuit board, and three tubes in a row from left to right.
The PV2 has two times, three tubes in a column from front to back on the circuit board.

Hopefully someone can answer that for you about which tubes you should use, or you can figure it out yourself based on the tube location diagrams.

Anthony
supersportsteve
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Re: PV-1 to PV-2AR conversion

Post by supersportsteve »

Thanks for the reply, you are correct about the gain being high, looks like a passive preamp will help.
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