Go for the resister mod no brainer as far as Im concerned. I can only speak from personal experience but it wasn't the extra watt, is was everything else, just more!....
think it was documented in this thread - an optimisation of the circuit that became obvious after more thought and or Californian wine (?) ...its just nicer.....in art a word you cannot say but I managedI love my ACA bi amp, aleph J still waiting for funds bloody heatsinks!
Where do the boards in the kit come from? The boards currently sold by the diyAudio store have a space for R15. If you have these boards, no mod needed.
Yes, 18VAC will give 24VDC -> more heat 
I have built with 300VA toroid 2x15VAC and 132mF, a little bit overkill.....
15VAC gives 19,7 VDC.
Just wanted to know what`s minimum.
Instead of more voltage I have changed R15 to 1K5.
Gives about 1,7A Bias and a little more heat.
Sound is maybe a little "smoother"..?
I have built with 300VA toroid 2x15VAC and 132mF, a little bit overkill.....
15VAC gives 19,7 VDC.
Just wanted to know what`s minimum.
Instead of more voltage I have changed R15 to 1K5.
Gives about 1,7A Bias and a little more heat.
Sound is maybe a little "smoother"..?
Guys, I bought a "kit" from someone and the enclosures separately. Does anyone have the parts list for the stuff required to build these amps in the enclosures?
I need:
-Part number of the power switch
-Part number of the dc jack
-Part number of the brass standoffs
-Part number of the RCA jacks
-Part number of the speakers jacks
-What size are the washers and screws used? Part numbers would be aweoms
-Part number of the Keratherm insulators
Thanks guys!!
-Jim
I need:
-Part number of the power switch
-Part number of the dc jack
-Part number of the brass standoffs
-Part number of the RCA jacks
-Part number of the speakers jacks
-What size are the washers and screws used? Part numbers would be aweoms
-Part number of the Keratherm insulators
Thanks guys!!
-Jim
I guess, I really just need the speaker and RCA jack parts numbers as well as the power switch.
The other stuff, I've been able to largely figure out.
Thanks,
Jim
Hey Jim...
I didn't care for the supplied jacks, so I used some I had. The supplied
speaker posts did not accept banana terminated cables.
Are you willing to drill out the supplied holes to accept better jacks?
Mike
Thanks!
Yes, of course...
BTW, with BC546, is the 2k2R still needed? And bias setting always at 10V?
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Late to the party but...
Not sure if I should post here or in the general amp pictures thread, but this is pretty ACA specific so here goes...
Here's my version of the ACA based on a custom PCB that orients the FETs differently. Dual mono, 200VA 15V Anteks (this combo produces exactly 19.0V) and shields with diyaudio soft start and CRC filter boards with 15KuF caps. Standard Vishay 35A potted rectifiers. All deployed in a modified ModuShop 2U chassis with 10mm front panel, 300mmX40mm heatsinks.
I modeled the entire chassis and all components in Solidworks and then had the front and rear panels and heatsinks machined. I also designed a thicker base plate to help take the weight of the transformers and had it manufactured in small quantity. I think this baseplate will fit any of ModuShop's 300mm deep chassis but I know for sure it will fit the 2U. The parts are literally a swap.
How does it sound / work?
I'm most impressed with the high end. I have to say I'm hearing details in my music I hadn't heard before and I also find it far less fatiguing to listen to this amp with my nearfield monitors vs. my commercial NAD 2200 (BJT from the 80's). Hard to explain, actually, but it sounds amazing.
Heatsinks run roughly 109F at their hottest spot around Q1. Around 105-107F elsewhere. Each PCB draws 1.4A as verified by my bench supply during early testing / biasing. Soft start works like a charm...no dimming lights on startup. Kill-A-Watt shows 0.75A max peak on start with 0.65A @ 110VAC running.
Nelson, thanks so much for everything you contribute to DIY and for inspiring me to build this! You rock!
If you want to read more about it, check out the full story on PCBs here:
Dougs DomainCB
and the chassis / ps here:
Dougs Domain:Chassis
Not sure if I should post here or in the general amp pictures thread, but this is pretty ACA specific so here goes...
Here's my version of the ACA based on a custom PCB that orients the FETs differently. Dual mono, 200VA 15V Anteks (this combo produces exactly 19.0V) and shields with diyaudio soft start and CRC filter boards with 15KuF caps. Standard Vishay 35A potted rectifiers. All deployed in a modified ModuShop 2U chassis with 10mm front panel, 300mmX40mm heatsinks.
I modeled the entire chassis and all components in Solidworks and then had the front and rear panels and heatsinks machined. I also designed a thicker base plate to help take the weight of the transformers and had it manufactured in small quantity. I think this baseplate will fit any of ModuShop's 300mm deep chassis but I know for sure it will fit the 2U. The parts are literally a swap.
How does it sound / work?
I'm most impressed with the high end. I have to say I'm hearing details in my music I hadn't heard before and I also find it far less fatiguing to listen to this amp with my nearfield monitors vs. my commercial NAD 2200 (BJT from the 80's). Hard to explain, actually, but it sounds amazing.
Heatsinks run roughly 109F at their hottest spot around Q1. Around 105-107F elsewhere. Each PCB draws 1.4A as verified by my bench supply during early testing / biasing. Soft start works like a charm...no dimming lights on startup. Kill-A-Watt shows 0.75A max peak on start with 0.65A @ 110VAC running.
Nelson, thanks so much for everything you contribute to DIY and for inspiring me to build this! You rock!
If you want to read more about it, check out the full story on PCBs here:
Dougs Domain
CBand the chassis / ps here:
Dougs Domain:Chassis
