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Old 15th February 2011, 05:33 PM   #1401
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The ZTX parts have slightly different Vbe, so the protection point and bias setting would be slightly different. Your call.

One of the original Aleph clones used a 100K trimpot in the R13 position. You can also use a trimpot for R12 to experiment with AC current gain. I'd also have pads for fixed resistors once you determine your favorite values.

R17 should be less than R21. The actual values aren't too critical, but you don't want to see more than ~.3V across R17 in normal operation. R17 and R21 form a voltage divider. If your bias is 1A, you'll see ~.47 V across R27. A lot of interdependence. You can leave out R17, R21 and Q4. It just means that you don't have short circuit protection.

I'd avoid R6. Just match your input devices well. You might want to play around with different devices in the front end - in one of the shootouts a few years ago the ZVP3310 was preferred to the IRF9610 positions. But that was before people started playing with 2SJ74s.

The Jfets and ZVN3310 share the same lead order, but opposite body orientation. The lead order and spacing for the IRF9610 is different. If you want to allow for both you'll need two sets of pads.
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Old 15th February 2011, 05:57 PM   #1402
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I use a trimpot for offset and bias control.
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Old 17th February 2011, 02:45 PM   #1403
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When iīm going to drive the amp unbalanced all time, without thinking on driving it balanced, can R2, R9, R10, C1, Z3, Z4 be omitted?
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Old 17th February 2011, 06:32 PM   #1404
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If you would do a search for the original Mini-A thread all your questions will be answered in the very first post.

Best, Bill
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Old 17th February 2011, 07:14 PM   #1405
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Thanks for the hint, Bill

One last question here: Can i build this amp linke itīs shown in the original Mini-A thread with the values of the parts in briangtīs schematic?
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Old 17th February 2011, 07:38 PM   #1406
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What does the suggestion for liberal use of trim pots and the large variety of values used in the same basic circuit in the Aleph series tell you? It shouldn't say that all parts values are critical and the circuit won't work with any changes. There are a couple that are interdependent, but the circuit isn't hard to figure out what each change will do for you.
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Old 17th February 2011, 09:05 PM   #1407
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As Bob is saying, you can change damned near anything as long as you understand what sets the bias current, the overall gain, the AC current gain, and what maintains the near zero output offset. The Zen articles are the best source for study.

Have fun, Bill
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Old 4th December 2012, 11:52 PM   #1408
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Default xls to pdf for Aleph-5

Hello everyone, Could someone please post the BOM converted to a pdf for building a Aleph-5 with the chipamp.com black pcb's ? Thank's any help would be greatly appreciated !
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Old 5th December 2012, 12:13 AM   #1409
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wow. thats an old tread.
Bill, R.I.P.
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Old 5th December 2012, 12:20 AM   #1410
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There is no BOM for an Aleph5 specifically, but you can certainly utilize those boards for the Aleph5, I built 4 or 5 with various voltage/bias configs. With those boards you get an Aleph with the bonus of the Aleph 30/60 input, which allowed for more gain when using unbalanced inputs. You'll need to dig around for the schematics. The front end of the Alephs are all virtually the same, it's the back end, voltages, bias which is where they differ. The Aleph 30 is essentially the same configuration as the Aleph 5, just slightly different input (noted above), less bias/voltage, and a few resistor changes.

Last edited by MEGA_amp; 5th December 2012 at 12:31 AM.
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