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Old 28th February 2012, 02:15 AM   #1671
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Default Here comes some photos

guys,

Please check photos and comment
Thanks

Albert
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Old 28th February 2012, 08:53 AM   #1672
euro21 is offline euro21  Hungary
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Originally Posted by albertli View Post
Are you with transformer coupled ???
No, capacitor coupled.

#26 pre amp

If this drives my passive attenuator (S&B Tx102 MkII copper as autoformer -AVC-), (-3dB) upper limit "only" 80kHz (low level input, -20dB below transformer saturation).
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Old 28th February 2012, 09:11 AM   #1673
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guys,

Please check photos and comment
Thanks

Albert
Albert, Looks like a nice build.

The variation in temperature should be expected, when the Power resistors are mounted close together. Up to about 150 deg C, this is no real problem, but take precautions against anyone getting burnt!

Talking of precautions, please take care that the higher-voltage end of the resistors/tag-strip does not get shorted to chassis (beware screwdrivers!), or the 10W of Resistor-power will end up in the filament regulator's Q5. The transistor can actually handle this power, given good heatsinking, but the small heatsink normally required for a 26 filament regulator may get very hot if this happens!

The filament is also protected by the regulator, in this situation. No change in current or voltage will be forced onto the filament.
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Old 28th February 2012, 02:19 PM   #1674
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Rod,
Thanks for the advice and the guidance.


The variation in temperature should be expected, when the Power resistors are mounted close together. Up to about 150 deg C, this is no real problem, but take precautions against anyone getting burnt!
I have them checked last night and found that there just couple in a group was at 105c, only on the tip but not the whole body. The other end was 20c cooler.
Talking of precautions, please take care that the higher-voltage end of the resistors/tag-strip does not get shorted to chassis
I did think about changing the tag-strip to something else more solid. Will look around for something suitable. Is one big resistor work better on this position - Stability wise, or I can buy and put them on for the chassis still have room for that.


Albert
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Old 28th February 2012, 02:26 PM   #1675
Salas is offline Salas  Greece
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Did you check the Zobel on your output trafo regarding square waves? Massive nice sink on the regs, chunky general construction BTW. Nice. I hope you don't have a cat though with a taste for exploring red boards.
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Old 28th February 2012, 07:00 PM   #1676
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Did you check the Zobel on your output trafo regarding square waves? Massive nice sink on the regs, chunky general construction BTW. Nice. I hope you don't have a cat though with a taste for exploring red boards.
Sala's

Thanks for the comment. I don't have a cat, but I have a big German Shepard. My dog really doesn't care and he goes away every time I turn the volume up. I have to keep an eye on my grandson though, he is 11 months and learning to walk. I made a simple pcb as a platform for the zobel. I thought this will be easier for add on/ replace parts. Will report asap

Albert
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Old 28th February 2012, 07:18 PM   #1677
Salas is offline Salas  Greece
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Surely cover the reg red boards somehow so no fingers can ever touch the parts, keeping an eye is never full proof when kids are around, and lethal voltage areas are exposed. Maybe with perspex.
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Old 28th February 2012, 07:23 PM   #1678
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Rod,
Thanks for the advice and the guidance.


<snip>
I did think about changing the tag-strip to something else more solid. Will look around for something suitable. Is one big resistor work better on this position - Stability wise, or I can buy and put them on for the chassis still have room for that.


Albert
The very large Vitreous enamelled Wirewounds may give good sound, but even these have large exposed terminals. The Russian types that Andy gave the example, they look like they are worth trying.

But the big advantage of 10x parallel resistors is that the current-noise caused by the end-cap attachment (or wire termination) is reduced by paralleling. This could make a big difference to the sound, because the current is at the 1A level. for the same reason, series-connected power resistors would be a bad idea.

I would probably leave well alone, except to add some terminal insulation. Maybe you'll get the chance to try some other resistors in the future, but for now, I would do some good listening!
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Old 29th February 2012, 01:37 AM   #1679
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Surely cover the reg red boards somehow so no fingers can ever touch the parts, keeping an eye is never full proof when kids are around, and lethal voltage areas are exposed. Maybe with perspex.
This is my concern too. Thanks
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Old 29th February 2012, 01:42 AM   #1680
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Originally Posted by Rod Coleman View Post
The very large Vitreous enamelled Wirewounds may give good sound, but even these have large exposed terminals. The Russian types that Andy gave the example, they look like they are worth trying.

But the big advantage of 10x parallel resistors is that the current-noise caused by the end-cap attachment (or wire termination) is reduced by paralleling. This could make a big difference to the sound, because the current is at the 1A level. for the same reason, series-connected power resistors would be a bad idea.

I would probably leave well alone, except to add some terminal insulation. Maybe you'll get the chance to try some other resistors in the future, but for now, I would do some good listening!
Thanks and I have some new idea in mind. I'm going to replace the tag-strip, see if that helps even out the temperature.
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