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Old 7th December 2012, 02:17 PM   #3201
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Quote:
Originally Posted by lhquam View Post
I measured the hum & noise on my Teaser-6 with a Fluke meter. Outputs connected to 8 ohm loads. Inputs connected to M-Audio AP-192 sound card with no signal.

left channel: 0.6mV AC RMS
right channel: 0.2mV AC RMS
I routinely rotate the transformers in FW product to set the noise levels
at the lowest equal value. My F6 proto came out a bit over 0.1 mV

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Old 7th December 2012, 02:19 PM   #3202
6L6 is offline 6L6  United States
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Papa,

When you say rotate, do you mean swap one out for another or twist the torroid on it's mounting bolt for minimum hum?
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Old 7th December 2012, 02:36 PM   #3203
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Originally Posted by Tea-Bag View Post
Has anyone thought out the value of R1 to keep relative gain at 15db if using IRFP240's? I am prototyping this, but uncertain of a formula that can help.

My apologies if this has been mentioned already. I assume tweaking this and the degeneration resistors will get this working on point. I plan on using for source resistors 1R to start with the 10R Zen Pots.
I believe that R1 is the feedback resistor from output ? If so I'd leave it at 100R as this would still get us close to the orig 15 db gain。if you would like the actual exact formula it's somewhere earlier on this thread - I can look for it.
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Old 7th December 2012, 02:41 PM   #3204
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Originally Posted by Nelson Pass View Post
I routinely rotate the transformers in FW product to set the noise levels
at the lowest equal value. My F6 proto came out a bit over 0.1 mV

I have been surprised a couple of times how much difference this can make. My builds tend to be in tighter quarters than what i have seen from the FW chassis.
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Old 7th December 2012, 04:48 PM   #3205
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I set both R13 and R14 at .025 ohms and spent a couple of days listening. I think the soundstage is both wider and deeper than with r13, R14 set to zero.I also appear to have more detail. Don't know if its me thinking I need to hear something different I am going to set R13 to .0125 , keeping R14 at .025and give a listen. Then I will reverse the two. In my system this resistance range is where I get the most stimulation to my ears. Resistors are 5W wirewounds

Best

Bob
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Old 7th December 2012, 07:30 PM   #3206
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Quote:
Originally Posted by 6L6 View Post
Papa,

When you say rotate, do you mean swap one out for another or twist the torroid on it's mounting bolt for minimum hum?
Twist.

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Old 7th December 2012, 08:17 PM   #3207
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Originally Posted by Nelson Pass View Post
Twist.

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Old 7th December 2012, 09:21 PM   #3208
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Default Twist and shout...

Well, shake it up, baby, now
Twist and shout...
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Old 8th December 2012, 12:04 AM   #3209
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Twist 'n Frugg

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Old 8th December 2012, 12:07 AM   #3210
lhquam is offline lhquam  United States
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That did the trick. After rotating only about 15 degrees both channels are somewhere between 0.1 and 0.2mV RMS. (The Fluke meter indicates 0.1mV with its leads shorted).

Quote:
Originally Posted by Nelson Pass View Post
I routinely rotate the transformers in FW product to set the noise levels
at the lowest equal value. My F6 proto came out a bit over 0.1 mV

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