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Old 15th January 2012, 09:48 PM   #3851
M Gregg is offline M Gregg  United Kingdom
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Its RFI shielding,

Covered in Foil..The caps are Mundorf silver in oil..Audio note pot..

I shielded The Tx's from the circuits..you can see the tape in the pic..

The finish was a moment of madness..shellac resin..

While I think about it notice no holes around the tubes...
The bases are gapped 3mm and mounted on silicone washers..
The vent at the back is driven by the heat of the choke..


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M. Gregg
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What is the sound of one hand clapping?

Last edited by M Gregg; 15th January 2012 at 10:04 PM.
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Old 15th January 2012, 10:32 PM   #3852
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by GloBug View Post
Looks good!, Is that a copper shielding in there?
Yes sorry just realised what you were looking at,
Across the front section for the tubes is a copper shield..(double sided PCB)

It seems to work well..
I can't tell when it's switched on except for the neon in the power switch its Dead silent, ear inside the speaker no hiss or hum like the speakers are disconnected..

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M. Gregg
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What is the sound of one hand clapping?

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Old 18th January 2012, 09:09 AM   #3853
M Gregg is offline M Gregg  United Kingdom
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Well I notice,
The schematic is missing in the Build thread..

So here it is...The line with feedback is not used it was just an Idea for global feedback and yes it does work, however just use a standard 1M ohm..
I use a dual log 100k In the volume position..

Thread is
Any thoughts on this circuit?

Lots of design and help from artosalo and toprepairman (many thanks for a great project)



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M. Gregg
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What is the sound of one hand clapping?

Last edited by M Gregg; 18th January 2012 at 09:17 AM.
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Old 18th January 2012, 09:23 AM   #3854
male42 is offline male42  Russian Federation
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I would refuse the capacitor at the input
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Old 18th January 2012, 09:37 AM   #3855
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No input cap and not sure you need a 220R feed from the primary OPT tap to the screen grid. The rest looks OK. Please no GNFB. Also if no GNFB drop the earth from the secondary of the OPT. Let the secondary float.
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Old 18th January 2012, 09:41 AM   #3856
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by male42 View Post
I would refuse the capacitor at the input
There are lots of tweeks this is just the schematic as was..because it has gone missing in the build thread..

And no global feedback is used...I like the sound...its close in schematic to a PYE mozart...
Please note that the secondary is providing the feedback..and needs the earth..
If you get the secondary out of phase it will be unstable..
If you remove the box saying feedback components and the lines so you just have a standard 1M resistor with secondary in the cathode + Gnd thats it..

Without the 220 you will get grid current..

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M. Gregg
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What is the sound of one hand clapping?

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Old 18th January 2012, 10:15 AM   #3857
M Gregg is offline M Gregg  United Kingdom
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The secondary IS part of the cathode circuit.



It does need a choke PSU...so please read the thread if you think about building it...
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What is the sound of one hand clapping?

Last edited by M Gregg; 18th January 2012 at 10:21 AM.
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Old 18th January 2012, 10:33 AM   #3858
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by mhouston View Post
Also if no GNFB drop the earth from the secondary of the OPT. Let the secondary float.
How can I do that when its carrying the cathode current?

Yes its strange..

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M. Gregg
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Old 21st January 2012, 08:42 AM   #3859
dady is offline dady  Argentina
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HI lazarello, I need to hear your oppinion about the Hammond SE Transformers.
Your equipment looks wonderfull.
Best Regards
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Old 21st January 2012, 10:37 AM   #3860
Milen is offline Milen  Bulgaria
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E88CC + EL34 SE, 5,5W @ 8 Ohm
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