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Old 3rd January 2013, 12:12 PM   #711
Nisbeth is offline Nisbeth  Denmark
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D'oh! Thanks

/U.
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Old 4th January 2013, 09:50 PM   #712
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Quote:
Originally Posted by Nelson Pass View Post
There's lots of margin in this design. As long as your original voltage is
not really much larger, I suggest you use it, and set the Drain voltage
at approximately 1/2 of the supply.

Many thanks for the info. Will be very useful.

Its a really nice little Amp. Many thanks for sharing your ideas.


Some Pics with the big brothers the F5, J and the B1 as Pre
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Old 8th January 2013, 12:59 AM   #713
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An ACA with a 0.22 ohm resistor in place of R1, R2 and a 0.33 ohm resistor in place of R3, R4 was tested for open loop gain at 1kHz, then the closed loop gain was adjusted via a trimpot to be 10dB less. The R12 value listed is just a calculated value. The distortion was measured along with the 2nd harmonic. For the 2X and 3X columns additional resistors were added in parallel with the exsistong 0.22 and 0.33. The 2X via jumper column is the standard ACA with a 1K resistor connected from Base to Emitter on Q3 effectively doubling the current. The open loop gain is higher but distortion numbers are about the same. All measurements were taken with an 8 ohm load and the voltage at the plus side of C1 adjusted to 10.0V.

The biggest surprise was that distortion at 1 Watt decreased at higher currents, but only below about 2kHz. At 10kHz distortion actually increased slightly.
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Old 8th January 2013, 03:04 AM   #714
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Loudthud and all, so it appears that there is no real benefit in increasing current as compared to Nelson's standard configuration. My considered guess is that in the long run the standard current setting and its distortion profile would be sonically more pleasing.

However, it is possible that Bass might be a little tighter with the higher current setting.
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Old 10th January 2013, 09:56 PM   #715
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Quote:
Originally Posted by Loudthud View Post
An ACA with a 0.22 ohm resistor in place of R1, R2 and a 0.33 ohm resistor in place of R3, R4 was tested for open loop gain at 1kHz, then the closed loop gain was adjusted via a trimpot to be 10dB less. The R12 value listed is just a calculated value. The distortion was measured along with the 2nd harmonic. For the 2X and 3X columns additional resistors were added in parallel with the exsistong 0.22 and 0.33. The 2X via jumper column is the standard ACA with a 1K resistor connected from Base to Emitter on Q3 effectively doubling the current. The open loop gain is higher but distortion numbers are about the same. All measurements were taken with an 8 ohm load and the voltage at the plus side of C1 adjusted to 10.0V.

The biggest surprise was that distortion at 1 Watt decreased at higher currents, but only below about 2kHz. At 10kHz distortion actually increased slightly.
WOW! Thank you for the detailed testing results!

Looking at your results, and using them as a rough guide for my own experimentation, it seems I am in agreement with Samuel Jayaraj's sentiments. I enjoyed the sound with no feedback, with feedback, 2x/3x bias, but it seems I've reached the limit....with my inefficient speakers anyway. I picked up a pair of Alpair 10.2 and FE126En, with the hopes of pairing them up with this amp, choosing a design is another matter....Frugal Horn MK-III...?

-john
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Old 10th January 2013, 10:09 PM   #716
bcmbob is offline bcmbob  United States
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Mega,

Don't know if you have been watching, but these are a lot of fun and sound surprisingly good. Might be a match for the FE126En.

Foam core Spiral Horn.
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Old 11th January 2013, 02:42 AM   #717
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Anyone have any idea how these might sound on some high efficient horns being biamped.
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Old 11th January 2013, 02:44 AM   #718
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well they sound freakin' awesome on a 97dB/W/m full ranger so I would say they should sound great
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Old 12th January 2013, 06:51 PM   #719
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My new table heater, first side, first own class A experience in mono:

http://www.abload.de/img/acarunningxlqu3.jpg

Sounds very clean and round. Can't wait to listen to it in stereo.

Thank you Mr. Pass

And thank you once again for the layout Rudi!
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Old 14th January 2013, 01:47 PM   #720
chris45 is offline chris45  Germany
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Danger Mouse,

are trafos Block . Can you tell me please what type, voltage, rating
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