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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: 28 May 2011, 03:51 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Now put it in a box.

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PostPosted: 28 May 2011, 05:02 
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Mark,

Here I run into a problem. The caps are so tall that I need at least a 4U case.
The case with the massive heatsink is probably overkill as the modules are barely warm with the small heatsink I am using now.

Heatsink version - 190 Euros
Non-heatsink - 116 Euros

So which one? Or can you recommend a suitable 4U case?


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PostPosted: 28 May 2011, 17:05 
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Joined: 14 Oct 2008, 17:35
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Location: Dartmouth, Nova Scotia
If you don't mind me adding, a good improvement for that amplifier would be to add another something like 6.8MFD film cap along side the 1.5MFD Auricaps, this will give you around 8.3MFD for the imput coupling cap and get you better low frequency response, I was told that a 4.7MFD cap is not big enough to get a good flat 50 hz response into 22K load?

I added a 6.8MFD cap to the 3.3MFD cap I all ready had on my P3A, not sure if the difference is that noticable, I havn't really had any listening time on it since I added it but I am sure you will get sun low bass after adding one, 10MFD is supposed to be ideal. :)

Also, when you finalise you build, it wouldn't hurt to take the time out and use uninsulated solid copper wire in the power supply and outputs if possible, it sounds superb this way in my honest opinion. ;)


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PostPosted: 28 May 2011, 18:47 
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Hi Alan,

I have a Solen 6.8uF MKP cap lying around. Will try it and report back.

My wiring is temporary. Once I get a case, it will be hooked up with high quality wire.
I'm trying to make the wiring as neat as Benny's. LOL

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PostPosted: 29 May 2011, 19:40 
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Hi Dinesh, go for the no heat sink version. The other chassis is way to big for a preamp. ;)

Also, perhaps consider going for a 2U chassis and mounting the capacitors horizontally.

Cheers

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PostPosted: 05 Jun 2011, 07:46 
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I tested with a 6.8uF Solen cap and was disappointed - the bass remained the same but the treble lacked clarity of the Auricaps. Soundstage also appeared to close in. This could be due to the fact that my speakers cannot play deep bass well.

I ramped up the bias to 0.25A and was very impressed with the sound. Better bass impact and less grainy treble. Biggest improvement was fatigue free listening @ 92dB levels. The cold NZ air keeps the heatsink barely warm to the touch with such a high bias!

"i'm loving it!" :mrgreen:

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PostPosted: 05 Jun 2011, 16:32 
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Jaycar sell a 4U. Jaycar is in NZ.

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PostPosted: 05 Jun 2011, 20:03 
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Yes Mark, I was there few weeks ago. They just re-opened after recovering from earthquake damage.
They refused to give me a student discount =(
Jaycar in Mel rocks!

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PostPosted: 06 Jun 2011, 07:10 
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Dinesh: Apply for a trade card. You R an engineer. They will issue one to all train drivers.

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PostPosted: 10 Jun 2011, 04:10 
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I have noticed that at loud volume levels, the heatsinks do no change temperature ? Still barely warm.
Maybe the peaks in the music do not exceed 0.25A of bias !
So this means I'm running in pure class A ? =O

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