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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 10 Dec 2012, 16:41 
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Joined: 10 Dec 2012, 16:03
Posts: 1
Hello redsky.
I´m working in the similar project and I´m very glad if I would can see the pics. I don´t know why don´t show me.
Best regards


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PostPosted: 18 Nov 2013, 06:01 
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Joined: 27 Dec 2012, 06:29
Posts: 47
Hello All

I've now put one of these together, and am very pleased with the results, The only problem appears to be a massive increase in volume when I turn my amp off (I've plumbed it into my KT88 valve amp, and it runs off the heater supply), until the caps run dry. I assume it is something to do with the voltage regulator's behaviour when the supply is cut, but am guessing - any ideas?

Cheers

John


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PostPosted: 18 Nov 2013, 18:05 
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Joined: 04 Jun 2008, 20:59
Posts: 3786
Location: Arizona, USA
Hi, I would think it is related as the "gain" is a function of brightness in the LEDs and when the power supply is shutting down an unusual voltage condition would be expected that could cause brightness.

Good listening
Bruce

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PostPosted: 19 Nov 2013, 04:56 
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Joined: 27 Dec 2012, 06:29
Posts: 47
I might stick a relay inbetween the regulator and the pot, just to cut the supply straight away when the amp shuts down. If I forget to turn off the source first, it wakes the whole house!


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PostPosted: 19 Nov 2013, 23:00 
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Joined: 28 May 2008, 21:53
Posts: 4561
Location: Winnipeg, CANADA
Hi John,
The attenuation should decrease with increasing current through the LED in the LDR. So it could be strange behavior from the regulator at the dropout voltage limit.

You have to watch that the heat from the tube amp does not heat up the LDRs. The resistance of an LDR will vary significantly with small changes in temperature. I had a similar arrangement but I eventually housed the attenuator in its own enclosure and separate power supply.

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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PostPosted: 07 May 2017, 21:33 
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Joined: 27 Apr 2017, 21:03
Posts: 2
Can anyone tell me where I can get a matched quad of LDP for building such Attenuator? Thanks in advance for your help!

Cheers


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