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Old 14th October 2012, 06:45 PM   #2151
10y is offline 10y  Italy
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Ale,
will do like you suggest

Thank you !

Ciao,

Anto
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Old 14th October 2012, 06:53 PM   #2152
DimZ is offline DimZ  Greece
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for the rubber suspenders take a look here

PB Fastener Gewindepuffer 110004 Außen-/Außengewinde Schwarz im Conrad Online Shop | 546346

and here

4x Anti Vibration Damper Isolator for FPV Aerial Photography GIMBAL ECILOP XA650 | eBay
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Old 14th October 2012, 07:26 PM   #2153
mogliaa is offline mogliaa  United Kingdom
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Anto,
The rubber dampers are not cheap, but worth adding them. If you don't want to put the money on them, you can cut some rubber squares from a spare bicycle tube and add them between the screws and the base of the amp.
Time to experiment my friend!
Ale
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Old 14th October 2012, 08:16 PM   #2154
Magz is offline Magz  United States
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Quote:
Originally Posted by andyjevans View Post
I wasn't aware of this - it could be useful since you can adjust the final voltage more accurately. What's the minimum size resistor to give adequate separation?

Also it could help with strike voltage if the HT is restricted.
Putting a resistor of that size in series with the VR tube will kill the regulation. If that doesn't matter to you, then go for it.
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Old 14th October 2012, 08:16 PM   #2155
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I used mouse pads to mount sockets of "microphonic" tubes. Punched holes in the chassis bigger than tube sockets, mounted sockets on circles made from mouse pads, then mounted this construction on the chassis.
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Old 14th October 2012, 08:18 PM   #2156
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by Magz View Post
Putting a resistor of that size in series with the VR tube will kill the regulation. If that doesn't matter to you, then go for it.
Resistor is not in series. VR is fed by CCS directly and RC is fed out of it...
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Old 14th October 2012, 08:24 PM   #2157
Magz is offline Magz  United States
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Re: microphonics, if you look back a while in this thread, you can see what I did. I mounted teflon sockets on a heavy support I made from two 4mm thick aluminum plates sandwiching a layer of soundcoat damping material, then mounted the support to softwood brackets using Deflex bushings and washers.

I used wood to mount them because I wanted dissimilar acoustic impedances, I.e. aluminum-wood-aluminum-soundcoat-teflon.

In any case it worked great. I can tap on the shelf or even the preamp itself and not hear anything through the speakers. A lot of work, though...
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Old 14th October 2012, 08:35 PM   #2158
Magz is offline Magz  United States
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Quote:
Originally Posted by mogliaa View Post
Resistor is not in series. VR is fed by CCS directly and RC is fed out of it...
It looks like it's in series between the VR tubes and the 26 to me. As far as I know, that hinders the ability of the VR tubes to regulate the B+ going to the plate. If that doesn't matter to you, then no problem.
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Old 14th October 2012, 08:46 PM   #2159
mogliaa is offline mogliaa  United Kingdom
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Why? VR will keep the CCS node at same voltage. When anode voltage goes down, then more current is drawn, but difference is small to take VR out of regulation.
Can you explain your point?
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Old 14th October 2012, 08:54 PM   #2160
Magz is offline Magz  United States
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From what I've read when I was researching VR tubes and their application, you're basically increasing the output impedance of the VR tube as seen by the 26, so you get poorer regulation. Will it be enough to make an audible difference in that circuit? I don't know.
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