1 KOhm IMHO. Because negative FB connects directly to the input of ACA, and NFB gain is - R12/R11. If you add the source output resistance (5Kohm in your case in 50% volume and 10K volumepot, for example), the gain will be decrease.
PS
sorry my english
Thanks for the quick answer!
Your English is just fine - much clearer than my electronics thinking!
I have B1 board feeding pair of ACA boards.
I think I inadvertently swapped + and - on the supply rails.
What would this blow?
Amp appears dead
Nothing getting warm
Leds light fine
Bias voltage per build thread measurement points seem to sit at 1.5v
I'm assuming this will also have taken out the transistors on the B1 board? How do I check...
Thanks for your guidance
I think I inadvertently swapped + and - on the supply rails.
What would this blow?
Amp appears dead
Nothing getting warm
Leds light fine
Bias voltage per build thread measurement points seem to sit at 1.5v
I'm assuming this will also have taken out the transistors on the B1 board? How do I check...
Thanks for your guidance
Bad luck!
How difficult is it to separate the B1 from the ACAs?
Testing them separately would be my first step.
Is this the recommended order? or steps to happiness?
So ACA is the first step.
Thanks Anand.
Is this the recommended order? or steps to happiness?
So ACA is the first step.
Thanks Anand.
The recommended order would be ACA, Aleph J, F4 (with gain stage, try tube & solid state), F5, F6, and then VFET.
Best,
Anand.
Anand:
"inquiring minds want to know..."
Can you explain your thinking on this build series..did you get the rankings because of build difficulty, availability of parts/transistors/pcbs, sonic qualities, power levels and wasted heat, weight, or......
Trimpot of ACA must be set for symmetry clipping, not to 10V
I did adjust the bias this way - using the scope - and it resulted in a slight increase in the bias - from 10v up to 12-13 volts (different on the 2 channels). It seems like a simple adjustment to do if you have a scope and an oscillator handy.
Thanks, 6C4C.
Anand:
"inquiring minds want to know..."
Can you explain your thinking on this build series..did you get the rankings because of build difficulty, availability of parts/transistors/pcbs, sonic qualities, power levels and wasted heat, weight, or......
In all honesty I pulled it out of my fat ****
Best,
Anand.
Well, better for you to admit it than have others accuse you of it!!In all honesty I pulled it out of my fat ****
Best,
Anand.
I'm thinking of going straight from ACA to F6, in spite of the fact that I have parts for Aleph J on hand. Between those two choices, do you have any advice?
(sorry, I know it's OT for the ACA thread - I'll make it brief...)
I built the 2nd channel ACA amp and I'm using the BOSOZ 'line stage' as preamp- it has a 10k pot on the output side.
There's plenty of volume with 95dB speakers and both (stereo) channels - vs the one amp (mono) experiment before.
I'm going to try a few more combinations with volume control pots and different speakers, but what I have now seems usable, as far as volume level goes. So, I'm going to start looking in my shop for some case ideas.
I've gotten advice to use a low resistance pot if I want a 'passive' volume control between the CDP and the ACA. Does anybody make ganged(stereo) pots with less than 10k resistance? And, is that what I need?
There's plenty of volume with 95dB speakers and both (stereo) channels - vs the one amp (mono) experiment before.
I'm going to try a few more combinations with volume control pots and different speakers, but what I have now seems usable, as far as volume level goes. So, I'm going to start looking in my shop for some case ideas.
I've gotten advice to use a low resistance pot if I want a 'passive' volume control between the CDP and the ACA. Does anybody make ganged(stereo) pots with less than 10k resistance? And, is that what I need?
It's still at the 'breadboard' stage, but here are a couple of pics of my ACA pair.
Many thanks to Rudi_Ratlos who had posted the Gerber files for the PCBs. Using Gerbv software, I made the toner transfer 'masters and the pcbs.
I added a couple of pads for the R15 mod- just in case I needed them.
Power supply is a regulated 24v 5A Hammond supply.
I removed the R15 'mod' - heatsinks are cool (35-40C) so they are definitely large enough @ 60mm x 180mm
Next: case, power switch and fuse, etc....
Many thanks to Rudi_Ratlos who had posted the Gerber files for the PCBs. Using Gerbv software, I made the toner transfer 'masters and the pcbs.
I added a couple of pads for the R15 mod- just in case I needed them.
Power supply is a regulated 24v 5A Hammond supply.
I removed the R15 'mod' - heatsinks are cool (35-40C) so they are definitely large enough @ 60mm x 180mm
Next: case, power switch and fuse, etc....
Attachments
Well, better for you to admit it than have others accuse you of it!!
I'm thinking of going straight from ACA to F6, in spite of the fact that I have parts for Aleph J on hand. Between those two choices, do you have any advice?
(sorry, I know it's OT for the ACA thread - I'll make it brief...)
To me the Aleph J is the logical step up from an ACA, it's still has an SE MOSFET output stage but with a very refined Aleph current source (originally in the Aleph 3, then Aleph 30), and of course much more power, etc...
It depends on what you want really. I've always wanted to build an Aleph J as the extreme predecessor, the Aleph 3 in 1991, completely changed/shook the Hifi industry with its sound in spite of being "solid state." It was an amp I fell in love with in a Boston Hifi store a long time ago.
It's an amp that I want in my arsenal as a point of comparison to my other diy amp projects.
That being said, my first Pass build will be the F6 which is a very straightforward build.
Best,
Anand.
Well, better for you to admit it than have others accuse you of it!!
I'm thinking of going straight from ACA to F6, in spite of the fact that I have parts for Aleph J on hand. Between those two choices, do you have any advice?
(sorry, I know it's OT for the ACA thread - I'll make it brief...)
I just successfully finished Aleph J today. Got some bumps along the way but folks on the thread are of great help; especially, Jim (6L6). He has a special heart and willing to go extra mile to help others such as myself to finish the build successfully. Aleph J's sound is blissful and it's not even breaking in yet. Only the 1st day. The soundstage, dynamic range freq from low(bass) - high(treble) surpasses ACA. ACA is my 1st amp project then I jump to Aleph J after reading so many good reviews all around the entire forum and from people who finished it in the past.
My sequence is ACA -> some phono preamps in between -> DC B1 -> Pearl 2 phono -> Aleph J
Hope it helps and gives you some more courage to try out Aleph J. You won't be disappointed!
Regards,
Tom
If you do not have scope and oscillator on hand, just set it to 1/2 of power rail
I'm surprised that none of the experts has dropped in with the answer to your question.
(Perhaps a new thread in the Pass sub-forum would get more notice..)
It's not very clear in the descriptions, but the 'Grades' on the jfets aren't 'good to bad' grading, or 'First class, Second Class' , A, B, C....
My understanding is that the 'Grades' give an idea of the electrical properties - current & voltage specs.
It's also my understanding that the ACA is pretty tolerant about component choices, so I didn't hesitate to build mine since I had the parts on hand.