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Issue with Dynaco PAS2 with Van Alstine Mod

vaathi

vaathi

baski
Subscriber
I picked this up couple of years back from Sam. He was generous enough to give me the tubes he used. I have used this preamp for a while with Marantz 1120 connected to Rogers LS2a. Clean sound. I had to move the preamp to demo Heresy speakers I was selling. Amplifier used was Grandson of Ampzilla, a 40 WPC amplifier. Everything was working fine when I was using Iphone as source.

Buyer wanted to use his own CD ( Milt Jackson - Sunflower) I switched of the PAS2 and connected the CD into the same input and played the CD. Guess I switched off and on without letting it cool I guess. I heard heavily distorted sound. I never had any issue with this preamp.

Question is what to check first before using the preamp again?
 
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I think I goofed up by plugging the CD inputs into Special which I was using for Iphone in the excited Salesman mode.. I will try it again with Spare to make sure I didn't mess up the preamp. Thanks folks for your help. :)
 
vaathi said:
I think I goofed up by plugging the CD inputs into Special which I was using for Iphone in the excited Salesman mode.. I will try it again with Spare to make sure I didn't mess up the preamp. Thanks folks for your help. :)
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If you turned your preamp off then on again within a second or 2 you may have blown your tube rectifier if your Pas still has one. This called "hot switching" and is very bad for tube rectifiers. But if it still lights up and your preamp is making sound then the rectifier is probably ok. What may also happen is that your preamp shot a healthy dose of DC, because of the hot switching, into the SS amp which can really mess it up. My son fried a Counterpoint 200w hybrid amp this way. You should have seen all the output transistors that were totally blown. I am glad i wasn't there when that happened.
 
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Luckily the AMP is still fine. I used a Nakamichi CA-5 and demoed the CD for him. I will check the preamp again with Marantz today. Hopefully rectifier tube is still good. Fingers crossed.
 
vaathi said:
Luckily the AMP is still fine. I used a Nakamichi CA-5 and demoed the CD for him. I will check the preamp again with Marantz today. Hopefully rectifier tube is still good. Fingers crossed.
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Your Nakamich probably has a capacitor on the input, which saves SS amps as well as tubed amps from that horror!
 
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