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    Pas 3 taps like a mic

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    pcrosewood

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    Pas 3 taps like a mic

    Post by pcrosewood on Thu Oct 22, 2015 6:25 pm

    Picked up a pas 3 a while back. It had some issues so today is the day it all got sorted out. But, when I tap on the pas, anywhere, it comes through the speakers like I'm tapping on a microphone. I searched for a solution/ explanation and nothing came up. Hoping someone here can shed some light on this. Cheers and all the best.

    Bob Latino
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    Re: Pas 3 taps like a mic

    Post by Bob Latino on Thu Oct 22, 2015 6:38 pm

    pcrosewood wrote:Picked up a pas 3 a while back. It had some issues so today is the day it all got sorted out. But, when I tap on the pas, anywhere, it comes through the speakers like I'm tapping on a microphone. I searched for a solution/ explanation and nothing came up. Hoping someone here can shed some light on this. Cheers and all the best.

    It is possible that one or more of the 12AX7 tubes in your preamp is "microphonic" ... Check the link below ...

    Microphonic tubes

    Bob

    MontanaWay

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    Re: Pas 3 taps like a mic

    Post by MontanaWay on Thu Oct 22, 2015 6:49 pm

    yes, sounds to me like a microphonic tube. There is no fix except a replacement tube.
    Flick/tap each tube slightly and see which one is microphonic and replace that one.

    pcrosewood

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    Re: Pas 3 taps like a mic

    Post by pcrosewood on Thu Oct 22, 2015 7:04 pm

    Well, I tapped the tubes and they all sound microphonic . Everything I tap inside sounds equally microphonic, the tubes, the boards, the rectifier, the base. It raises and lowers with the volume control.

    MontanaWay

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    Re: Pas 3 taps like a mic

    Post by MontanaWay on Thu Oct 22, 2015 7:13 pm

    pcrosewood wrote:Well, I tapped the tubes and they all sound microphonic . Everything I tap inside sounds equally microphonic, the tubes, the boards, the rectifier, the base. It raises and lowers with the volume control.

    I assume it is an original PAS3?
    Power down and remove tubes from the phono preamp, power back up and then tap tubes on the line preamp, see if you still get the sound coming through. If yes, more than likely a tube on the line preamp. If not, more than likely phono preamp, power down, remove tubes from line preamp, re install tubes on phono preamp, power back up and tap those.

    GP49

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    Re: Pas 3 taps like a mic

    Post by GP49 on Thu Oct 22, 2015 7:50 pm

    If one tube is very microphonic, it will make that noise no matter which one you tap, since the vibration transmits no matter where you tap. And since the PAS filaments are connected in series, remember that when you pull one tube, two will go out!

    MontanaWay

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    Re: Pas 3 taps like a mic

    Post by MontanaWay on Thu Oct 22, 2015 7:55 pm

    GP49 wrote:If one tube is very microphonic, it will make that noise no matter which one you tap, since the vibration transmits no matter where you tap.  And since the PAS filaments are connected in series, remember that when you pull one tube, two will go out!

    that is true, but hitting a tube slightly may just give it away.
    Also, that is why I suggested to pull both tubes from either the phono or line preamp, so that particular pcb is 'dead'......

    pcrosewood

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    Re: Pas 3 taps like a mic

    Post by pcrosewood on Thu Oct 22, 2015 8:09 pm

    Well, I removed the tubes from the phono preamp and powered up and no noise. So I removed one of the tubes from the line preamp and replaced it with one tube from the phono pre and no noise. Removed that tube and replaced it with the other phono pre tube and that is the one that is microphonic. I'm new to tube gear and really appreciate this site and your help.Thanks everyone. Can I replace that one tube or do I have to get a matched set?

    MontanaWay

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    Re: Pas 3 taps like a mic

    Post by MontanaWay on Thu Oct 22, 2015 8:37 pm

    pcrosewood wrote:Well, I removed the tubes from the phono preamp and powered up and no noise. So I removed one of the tubes from the line preamp and replaced it with one tube from the phono pre and no noise. Removed that tube and replaced it with the other phono pre tube and that is the one that is microphonic. I'm new to tube gear and really appreciate this site and your help.Thanks everyone. Can I replace that one tube or do I have to get a matched set?

    well done!
    You can just replace the one tube, although, how old are the others? If they are still the original units, it may pay you to upgrade all of them, then, you'd be set for years to come!

    pcrosewood

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    Re: Pas 3 taps like a mic

    Post by pcrosewood on Thu Oct 22, 2015 8:53 pm

    The pas is original and I picked it up with a toasted transformer. I ordered one from dynakits and installed it today. I have no idea if the tubes are original .The writing is mostly worn off the tubes and it's not readable. Sounds good with the st-70 I also picked up recently.

    MontanaWay

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    Re: Pas 3 taps like a mic

    Post by MontanaWay on Thu Oct 22, 2015 8:55 pm

    pcrosewood wrote:The pas is original and I picked it up with a toasted transformer. I ordered one from dynakits and installed it today. I have no idea if the tubes are original .The writing is mostly worn off the tubes and it's not readable. Sounds good with the st-70 I also picked up recently.

    it would pay you to have a set of spare tubes, same for the ST70. They do not cost a fortune, and its just a nice backup!...as today has shown! Very Happy

    pcrosewood

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    Re: Pas 3 taps like a mic

    Post by pcrosewood on Thu Oct 22, 2015 9:35 pm

    What are some of the better, newer tubes. I know there are some good NOS tubes to be had but a lot of them at premium $$$. Are there some new tubes as good? I will get some backups. :-)

    MontanaWay

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    Re: Pas 3 taps like a mic

    Post by MontanaWay on Thu Oct 22, 2015 9:39 pm

    one has to be realistic here I guess. You have an older PAS3 and I assume an older ST70?
    So it is not going to make a huge difference buying premium tubes.
    EH aka Electro Harmonix, Tung Sol, even JJ, they are all good new tubes at good prices and will be perfectly fine with your setup.

    GP49

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    Re: Pas 3 taps like a mic

    Post by GP49 on Thu Oct 22, 2015 10:07 pm

    If they are original Dynaco tubes, they are Telefunkens. Check out the $$$ for new old stock Telefunkens, or even good-condition used ones!

    I'd take a good Telefunken any day, over anything from Eastern Europe, Russia or China.

    MontanaWay

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    Re: Pas 3 taps like a mic

    Post by MontanaWay on Thu Oct 22, 2015 10:10 pm

    GP49 wrote:If they are original Dynaco tubes, they are Telefunkens.  Check out the $$$ for new old stock Telefunkens, or even good-condition used ones!

    I'd take a good Telefunken any day, over anything from Eastern Europe, Russia or China.

    yes, Telefunken are very good, so are Siemens....but usually they are big $...AND there are a lot of forged Telefunken as well as Siemens out there......so caveat emptor!

    peterh

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    Re: Pas 3 taps like a mic

    Post by peterh on Fri Oct 23, 2015 1:36 am

    pcrosewood wrote:What are some of the better, newer tubes. I know there are some good NOS tubes to be had but a lot of them at  premium $$$. Are there some new tubes as good? I will get some backups. :-)
    JJ ECC83MG is a good tube with very little production spread ( all tubes has very simular properties)

    GP49

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    Re: Pas 3 taps like a mic

    Post by GP49 on Fri Oct 23, 2015 2:31 pm

    Original tubes marked DYNACO are very unlikely to be forged.  What may be more difficuli is finding a genuine NOS Telefunken if an original Dynaco goes bad.  

    Dynaco put some very good tubes into their gear...Telefunken 12AX7s, Mullard EL 34s and GZ34s...and yet I have seen some oafs yank out the original Dynaco-Telefunken 12AX7s from a PAS and stuff in some Russian or Chinese tube festooned with a fancy name. They would even GIVE me the Dynacos ("I can use them for test purposes," I'd tell them)!

    Tubes4ever

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    Re: Pas 3 taps like a mic

    Post by Tubes4ever on Sat Oct 24, 2015 8:20 pm

    GP49 wrote:Original tubes marked DYNACO are very unlikely to be forged.  What may be more difficuli is finding a genuine NOS Telefunken if an original Dynaco goes bad.  

    Dynaco put some very good tubes into their gear...Telefunken 12AX7s, Mullard EL 34s and GZ34s...and yet I have seen some oafs yank out the original Dynaco-Telefunken 12AX7s from a PAS and stuff in some Russian or Chinese tube festooned with a fancy name.  They would even GIVE me the Dynacos ("I can use them for test purposes," I'd tell them)!

    Would love to hear their rational for doing so. Care to share?

    GP49

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    Re: Pas 3 taps like a mic

    Post by GP49 on Sat Oct 24, 2015 11:32 pm

    Knownothing techs at a repair shop in a "High End" dealer.  They'd ask me for help fixing stuff.  In fact they farmed out all turntable and tape deck repairs to me...not much good with mechanicals.  

    They would sell people with tube gear on the idea that their old, dusty tubes were worn out, and replace them with new, shiny Russian or Chinese ones, and clean all the switches and sockets.  

    The place shrank down to one tech before the store was sold...He is doing something else, now; luckily for the customers!

    Tube Nube

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    Re: Pas 3 taps like a mic

    Post by Tube Nube on Sun Oct 25, 2015 2:28 pm

    I was over on the crossover network a couple weeks ago when I read of a fellow being told that his still quite new tube amp needed to be completely re tubed. From the description of the problem, it sonded like one tube might be bad.

    GP49

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    Re: Pas 3 taps like a mic

    Post by GP49 on Sun Oct 25, 2015 4:27 pm

    The late Dave O'Brien of McIntosh, who ran the McIntosh amplifier clinics, would make a show out of pulling the output tubes from a McIntosh that did not meet the THD spec of 0.5%, at full continuous rated power, 20-20,000 Hz.  He'd yank them with a tube puller (HOT!) and throw them into a garbage can, where the KT88s or 6L6s or whatever met their catastrophic end (CRASH! tinkle-tinkle).  But Dave knew those amplifiers inside-out, and none of those tubes were unnecessarily destroyed, because the amplifier would come back to life and meet its specs with the new tubes, whenever he did that.

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