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Aleph J-X Amp Project
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Old 19th March 2013, 06:20 PM   #1401
kroyin is offline kroyin  India
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I tried increasing r4 on both halves from 221k to 2x221k did not work.
Worth decreasing R1 to 10k ?
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Old 19th March 2013, 06:52 PM   #1402
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it must work , even if I wouldn't go to double value

you didn't make something right
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Old 20th March 2013, 09:37 AM   #1403
kroyin is offline kroyin  India
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In my understanding (perhaps flawed ) gain is set by a combination of feedback resistor,input resistor & resistor to ground.I rechecked their values and they are proper.
Increasing feedback resistor,decreasing input resistor (whatever I do) gives me additional 1VAC gain.

I must have done something wrong. Any other parts of the circuit that affects gain
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Old 20th March 2013, 09:43 AM   #1404
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ref. to original Pa's circuit , ratio of R4/R1 is defining CLG of amp

that's 221K/22K1

you can freely ignore R2 (221K) from that
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Old 20th March 2013, 04:24 PM   #1405
kroyin is offline kroyin  India
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Problem resolved...

I had explicitly grounded the daughter board to PSU.

I was trying out ARTA & it gave me a THD of 0.48% at 2.8V.
Generally I was unhappy

As part of fiddling process the ground wire came loose & to my surprise the THD dropped to .038%.

Whipped out my multimeter
Relative DC 12mV
Absolute DC -130mV
Gain 20dB

ARCHIMEDES MOMENT

Arta measurements attached
Attached Files
File Type: pdf arta_jx.pdf (292.6 KB, 240 views)
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Last edited by kroyin; 20th March 2013 at 04:33 PM.
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Old 15th July 2015, 04:29 PM   #1406
vdi_nenna is offline vdi_nenna  United States
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Hi Everyone,

I'd like to build the AX-J, and have Peter's boards. Is it possible to build with the following specs and parts. I have used the A-X v2 spread sheet, but would like to ask the experts if I'm doing something wrong.

Transformers are 14.25v secondary volts at 267VA. Basically building around these transformers because I have several. They are Amveco toroids and look well made. 130C, potted centers and thermal protection.

From spreadsheet:
Rectified voltage is ~20VDC
19v at mosfets. .55A per mosfets.
8 mosfets per channel.
8 ohm is 24W output.

Spread sheet says Factor 3 is 251W. Factor 1 is 167W. Not sure what "factor" means.
Dissipation per channel 84W
Dissipation stereo 167W


Is the 20 volts provided too low?
I'd be willing to lower the current through the mosfets, if it helps.

Thanks,

Vince
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Old 16th July 2015, 02:53 AM   #1407
koja is offline koja  Canada
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wow, I was not aware of any of Peter's boards still being around. I gave up the idea of converting my PD Aleph30 to AJ and started planning on building F4s instead w/ a tbd preamp (probably BA-3 FE). still, if I had AJ boards I might be tempted to try a quick conversion over the same footprint on the heatsinks.
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Old 16th July 2015, 04:40 AM   #1408
vdi_nenna is offline vdi_nenna  United States
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I've had the l boards for years among others.
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Old 5th March 2018, 03:52 PM   #1409
mats31 is offline mats31  Sweden
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Default Late to Aleph J-X party

Being very late to read about the Aleph J-X it seems. Built BBA3 and BA-1 SE as well as Aleph J's. Now very interested to upgrade my J's (which are fantastic, and measure very well with Arta as well) to get some more power (I have 86 dB/1W speakers)

Option 1: Turbocharge the J's by going from 4 to 6 output FETs, and run total bias of say 1,33x3 =4 A bias @ 27 volts (36 W/FET), giving around 40 watts RMS output with better handling of low speaker impedance (than stock AJ)

Option 2: Build Aleph J-X, easily getting 100W (bias/channel 1,4x6=8,4 amps @22 volts - know the thermal stuff will work out since I run at 9 Amps already in the same box @22 volts

Option3: Realise the sound level increase will be limited => do nothing and just enjoy the music.

Any advice from the experienced builders here on what route to prefer?

Also asking is anyone has Peter's input boards for sale (so Option 2 is kind of interesting still :-) :-))

Thanks!!!
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Old 5th March 2018, 04:24 PM   #1410
Zen Mod is offline Zen Mod  Serbia
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option ZM - buy more sensitive and more efficient speakers

option 1 - with 8R speakers , Iq (thus max I) isn't limiting factor , but rails voltage is ; so, no go

option 2 - some thoughts in Babelfish XJ , or JX .. or whatever (Aleph X servo for Greedy Boyz)
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