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Old 9th September 2012, 11:57 AM   #1541
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Originally Posted by lhquam View Post
Here is Stereophile Mag's impedance measurement of my B&W CDM1 speakers. Yup, my next tweak will be to lower the output JFET source resistors to somewhere near ZERO ohms, which will increase open-loop gain to around 100 or so. I could also reduce the closed-loop gain below 4.7, requiring an input source capable of higher voltage drive.
I hope that you do not drive your loudspeakers with a current source amp. Try this if you like [if not done already] with F1 or F2 diy builds as buzzforb suggested above. Their resulting tonal balance will be out of wack, and downright fatiguing.
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Old 9th September 2012, 12:00 PM   #1542
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BTW, before tearing down amp, pulled it away from toroid and all is well. no noise and completely silent.
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Old 9th September 2012, 12:04 PM   #1543
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Nope, I drive the CDM1s with balanced F5s - low enough output impedance to approximate a voltage source.

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I hope that you do not drive your loudspeakers with a current source amp. Try this if you like [if not done already] with F1 or F2 diy builds as buzzforb suggested above. Their resulting tonal balance will be out of wack, and downright fatiguing.
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Old 9th September 2012, 12:04 PM   #1544
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BTW, before tearing down amp, pulled it away from toroid and all is well. no noise and completely silent.
Now the listening pleasure begins. I am confident that you'll choose the optimal loudspeaker from your collection.
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Old 9th September 2012, 12:17 PM   #1545
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Nope, I drive the CDM1s with balanced F5s - low enough output impedance to approximate a voltage source.
By comparison, Rothacher uses Tekton Lore two-way 8 Ohm loudspeakers to mate with his L'Amp SIT amp of Zo ~8 Ohms. He was satisfied with this combo.
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Old 9th September 2012, 12:21 PM   #1546
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buzzforb. I second you opinion and first point you made earlier. You also build and know loudspeakers very well.
giving me way too much credit. I will be listening to my F6 with FR unit.
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Old 9th September 2012, 12:32 PM   #1547
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BTW, before tearing down amp, pulled it away from toroid and all is well. no noise and completely silent.
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Old 9th September 2012, 12:42 PM   #1548
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giving me way too much credit. I will be listening to my F6 with FR unit.
I wanted to write [before I saw your post] that you will most probably use an FR in maybe an Open Bafle loudspeaker design from the other threads you are involved with [that of Melon Head]. I looked at the impedance curve of Fostex FF 125WK. It showed the expected woofer impedance at its resonance then down to the minimum impedance of 8 Ohms between 100-500 Hz, and thereafter a gentle sloping rise in the impedance to 10 KHz. That FR will sound pleasant.

Last edited by Antoinel; 9th September 2012 at 12:59 PM.
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Old 9th September 2012, 12:56 PM   #1549
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With my Alpair 7.3dMarKen, i think it sounds pretty good. I am listening to laterals too. Small amount of noise, but not bad considering. Time to rebuild with SS
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Old 9th September 2012, 12:57 PM   #1550
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This has me worried.
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