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Old 29th March 2014, 04:04 PM   #321
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Quote:
Originally Posted by Rod Coleman View Post
Thanks, Andy....

For reference, I have attached a serving-suggestion for the 4P1L in filament-bias, transformer output version.

You can see the degeneration effect of the bias resistor: about 10%, if you choose 15Ω - for a typical bias of 8-9V or so.

4P1L is an excellent choice for experimenting with filament bias. It looks a bit wasteful of power, at first glance - but to get the same level of performance, you would need a separate transformer, rectifier, caps and a very low-noise regulator to generate a fixed-bias supply of equal quality to this circuit. The 3-terminal regulators would be fairly disastrous for this function, too!
Did you consider using the Ultrapath technique to extend bass response?
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Old 29th March 2014, 05:06 PM   #322
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Hi...

I did a total rewire after what I could see from my 6922 preamp, now playing for
30 min without any issues...

Michael.
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Old 30th March 2014, 07:42 PM   #323
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Hi Guys.

Would you mind to post some picture of your "not ringing" 4P1L.
It would be very helpful for me....

These rubber dampers, which one do you use. ???

Any luck from mouser, gets stuff from them very regular...

Thanks Michael.
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Old 30th March 2014, 08:18 PM   #324
mogliaa is offline mogliaa  United Kingdom
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Hi Michael,
I mount the ceramic valve socket directly with a pair of silentblocks (see link below). They are not cheap but are very effective. You can also make a sandwich of a top plate with a silicon layer in between, this can be effective as well.

This seller is closer to you, so you may find it useful.
Gummipuffer Silentblock Typ A M3 6 / H 10 Silent Block Bloc | eBay

Cheers,
Ale
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http://www.bartola.co.uk/valves/
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Old 1st April 2014, 12:34 PM   #325
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Hi Ale..

I ordered 10 of these silentblocks.

I can't use my socket anymore.

Do you mind to share which socket do you use ???

/Thanks Michael
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Old 1st April 2014, 12:44 PM   #326
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Here are some methods - my current line stage and proposed "overkill" arrangement with plumbers units. Top plates are 4mm aluminium.
Attached Images
File Type: jpg 4P1L plumbers units.jpg (884.8 KB, 344 views)
File Type: jpg 4P1L.jpg (919.0 KB, 332 views)
File Type: jpg 4P1L_PSE-OPstage.jpg (930.1 KB, 325 views)
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Old 2nd April 2014, 11:54 AM   #327
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Hi.

Thank you for your suggestions.

I have my amp in a homemade chassic made of azobe "iron wood". This helped on
the microphonic, and I have ordered the "silent blocks".

Will try to add the "silent blocks" when they shows up.

I have 25 hours on the beast and its getting better.

Click the image to open in full size.

Michael.

Last edited by michaelvv; 2nd April 2014 at 12:00 PM.
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Old 2nd April 2014, 12:18 PM   #328
euro21 is offline euro21  Hungary
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Hi Michael,

Try to use suspended sub-chassis.
In the sub-chassis mounting holes I use rubber grommet, and between the sub-chassis and the socket I put rubber sheet.
Attached Images
File Type: jpg image032.jpg (64.5 KB, 276 views)
File Type: jpg image036.jpg (65.0 KB, 158 views)
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Old 2nd April 2014, 01:00 PM   #329
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Quote:
Originally Posted by euro21 View Post
Hi Michael,

Try to use suspended sub-chassis.
In the sub-chassis mounting holes I use rubber grommet, and between the sub-chassis and the socket I put rubber sheet.
Hi Euro21...

First i would like to suspend the sockets from the aluminium plate.

Then I'll suspend the trafos from the chassis. Tried with some rubber which
turned out to be quite efficient.

The Silent Blocks would be my choice here.

If I don't play to loud "normal listening level" it's quite okay now.

When I started it was a disaster. Now it's much better.

I really like the sound of the 4p1L. Bass response is way over my wildest
expectations. Midrange and top is starting to be a lot better.

My speakers is a pair of tannoys 385-HPD alnico, in a 303 liter internal volume enclosure. Running on a 2a3 loftin-white amplifier.

Michael.
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Old 2nd April 2014, 01:48 PM   #330
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Quote:
Originally Posted by michaelvv View Post
Hi Euro21...

First i would like to suspend the sockets from the aluminium plate.

Then I'll suspend the trafos from the chassis. Tried with some rubber which
turned out to be quite efficient.

Michael.
Before you do any drastic rebuilding, put the chassis on something really soft and spongy. And wrap teflon plumbers tape round the bottles several times. Remember that there is both air borne and structure borne vibration.

I don't know why you want to suspend the transformers - surely they add mass to the chassis which is good? It's the glass bottles and the filaments in the tube that vibrate.

You could make a subchassis for the sockets - may be overkill. In that case mount the sockets on a double thickness alu, like 8mm. Mass is your friend. You may prefer to use bendy springs to decouple - think Linn turntables.

You need to think a bit about what you are doing here. I know Ale uses the rubber decouplers, and I pretty much have faith in anything he does, but I think it's possible to achieve better decoupling than that by imitating turntables. There's also the SME turntable which used multiple rubber bands. Like the Linn they use gravity to suspend the sub-chassis. And because gravity works better on heavier objects, the mass of the sub-chassis should be robust.

Last edited by andyjevans; 2nd April 2014 at 01:51 PM.
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