Phase Linear amp, preamp on CL great deal

[Ken Boyd]

As a Bob Carver fan I love these old Phase Linear amps, a PL 700b and a PL 4000 preamp for sale both in good shape and working includes the orginal PL cooling fan. These were some of the most powerful amps in their days with 350 watts at 8 ohms, almost 700 at 4 ohms and over 900 at two ohms. Would recommend having them both refurbished but when done are great sounding amps for the price IMO. Not mine and and no affiliation but if I lived close or the seller wanted to ship them I would take them off his hands. Most of the ebay listings on these amps go for at least 700 and the pre goes for over 300 and the fan kits for for over 200.

Hope someone here on AK picks them up.

http://minneapolis.craigslist.org/dak/ele/2674930452.html

 

[Ken Boyd]

Darn already sold, I knew it was a good deal, I hope someone here got it!

 

[frankxbe]

real good deal I had a phase linear 700b bought it used for 450. in the
late 70's sounded good sold it though had way more power than I needed at the time
sold it at a profit.

 

[luckyed]

Darn already sold, I knew it was a good deal, I hope someone here got it!

The ad is still up. Why do you think that it is sold?

 

[Cactus Bob]

and the fan kits for for over 200.

Tell me about the fan kit. Is that after market or?

My 700b that I picked up last week came in the wooden case and also came with a fan mount as shown below. Shouldn't the fan be cooling the tranny not the heat sinks?

 

[Ken Boyd]

The reason I know is because I called to see if he would ship them and if he would take paypal for payment, he said he sold it right after the listing was posted. I don't know why he didn't remove the listing.

The transistors are mounted right on the back of the amp, on the base of the cooling fins. The fins are there to assist in cooling the transistors by adding additional surface area. By the fan blowing on the fins, it dispates the heat in a more efficent way than just blowing on the transistors themselve. Just like an air cooled engine the fan blows on the fins around the combustion chamber to cool it if you didn't have the fins and the fan just blew on the combustion chamber it would not be able cool it as well. For the most part a fan kit is not needed, but since these amps were sold for the home audio market which would very often ever have driven these amps to the point of overheating, but since the amp was so powerful in those days, big name bands and nightclubs started using them in their pro audio racks and drove them full out and they started have problems with overheating. You have a lot of transistors on these amps, way more than most of the other amps that I can recall, and they all are putting out a lot of heat when driven hard and the combintation of that many transistors all getting each other hot when driven hard needed the fan kit. I can't recall any other amp that used as many transistors on them, I recall the BGW amps that Universal Studio's contracted to use in the movie Earthquake having quite a few but not as many as the PL amps.

 

[Cactus Bob]

Thanks for the explanation, but the fan mount (see picture above) has the opening for the fan over the tranny. I believe this is an original factory piece that was purchased with the walnut cab. for the PL700b.

 

[bowtie427ss]

Thanks for the explanation, but the fan mount (see picture above) has the opening for the fan over the tranny. I believe this is an original factory piece that was purchased with the walnut cab. for the PL700b.

If the ventilation openings in the wood case were located above and below the heatsinks, the airflow would effectively serve to cool both. And it makes sense as the wood cabinet would greatly restrict the otherwise natural convection around the transformer.

Lots of fan cooling schemes draw the incoming air over the transformer/s first.

 

[Ken Boyd]

+1 couldn't have said it better