strongbow60: Not on my unit. If you try and read the bias with no load, then the current rises to +10 volts on the meter or so, then gradually declines. No reading/adjusting is possible without a speaker load connected to the terminals.
^ This does sound odd. I have also made all my "bias voltage" adjustments without a speaker load connected. There is just the 1k load that is intended to discharge the output coupling capacitor.
TA: Perhaps because my units are wired directly to the RCA ins and Terminal outs with none of the shared connections used in the stock model. BTW, TA, got the PSU done for the M2X build and it works superbly. Thanks for your equipment reccos.
Craig, I may follow in your footsteps and build the m2x! although it may have to wait until next summer as I just started a new teaching job.
The modified ACA is sounding so good. I'm now wholeheartedly in favor of the FQH44N10 in both Q1 and Q2 after some experimenting with changing Q2. It sounds perfectly balanced. Thanks again to Tungsten and everyone for the help and suggestions, the amp is leaps and bounds better than stock, I would never have believed it could have been improved this much and I haven't even increased the voltage or gon to a linear PSU, the dual-smps setup is really fantastic.
I'm looking forward to trying rthatcher's filter boards when they are ready. I also ordered the two pole power switch.
The modified ACA is sounding so good. I'm now wholeheartedly in favor of the FQH44N10 in both Q1 and Q2 after some experimenting with changing Q2. It sounds perfectly balanced. Thanks again to Tungsten and everyone for the help and suggestions, the amp is leaps and bounds better than stock, I would never have believed it could have been improved this much and I haven't even increased the voltage or gon to a linear PSU, the dual-smps setup is really fantastic.
I'm looking forward to trying rthatcher's filter boards when they are ready. I also ordered the two pole power switch.
Zj27: Thanks. Am almost finished with the M2X but have been waylaid by a troubled board. This should be fixed tomorrow and will then have some listening results.
Here are some things you need to know about a M2x build.
1. The parts for the main boards have to be ordered from both Mouser and Digikey as a number are backordered at Mouser. Order both the boards and chassis from DIY as the chassis may take a while to ship. Mine arrived in only 5 days from order but this was unusual.
2. The PSU can be a learning challenge and PaulInWA has done great work in providing a BoM for a basic 3-stage unit with transformer-rectifier-PSU board. Will provide additional information if you need it. My PSU unit is very stable and has more power than will ever be needed. It weights 24.4 lbs and requires a good-sized 3U chassis.
3. Only the Tucson and Mountain View daughterboards can currently be built as the others have parts backordered -- some of them very far ahead.
4. Make sure you get at least a 3U tall case for the amp -- am trying a 2U and it is not sufficiently high. A number of rail alterations had to be made.
And, to second your accolades, the new DS ACA I have just finished (2nd one) is sounding so good that I never use my other tube and Emotiva amps. It is way out of their class. Now I hope that the M2X sounds as good or better. Will see.
Here are some things you need to know about a M2x build.
1. The parts for the main boards have to be ordered from both Mouser and Digikey as a number are backordered at Mouser. Order both the boards and chassis from DIY as the chassis may take a while to ship. Mine arrived in only 5 days from order but this was unusual.
2. The PSU can be a learning challenge and PaulInWA has done great work in providing a BoM for a basic 3-stage unit with transformer-rectifier-PSU board. Will provide additional information if you need it. My PSU unit is very stable and has more power than will ever be needed. It weights 24.4 lbs and requires a good-sized 3U chassis.
3. Only the Tucson and Mountain View daughterboards can currently be built as the others have parts backordered -- some of them very far ahead.
4. Make sure you get at least a 3U tall case for the amp -- am trying a 2U and it is not sufficiently high. A number of rail alterations had to be made.
And, to second your accolades, the new DS ACA I have just finished (2nd one) is sounding so good that I never use my other tube and Emotiva amps. It is way out of their class. Now I hope that the M2X sounds as good or better. Will see.
I am sure this has been answered somewhere in the 46 pages, but google hasn't shown me the answer....
This design is so similar to the Zen amps, and there is no PCB available anymore, has anyone put higher voltage parts on the ACA PCB, gave it 50v power supply and gotten results similar to or better than the Zen V4? I see lots about higher quality parts, and even new power supplies, but not much specifically about running the ACA at much higher voltages in the dozen or so pages I've read.
I ask because while I bought some Chinese Zen V4 boards, that was only a few dollars investment, and I am now trying to decide whether Zen V4 at 50+ volts or a pair of custom built ACA (turbo) amps is the right build. What I am looking for is the highest power best sounding single mosfet amp.
Between zen boards, DIY PSU boards, transformer, parts and a case, I am looking at a minimum of $700 for a Zen.
This design is so similar to the Zen amps, and there is no PCB available anymore, has anyone put higher voltage parts on the ACA PCB, gave it 50v power supply and gotten results similar to or better than the Zen V4? I see lots about higher quality parts, and even new power supplies, but not much specifically about running the ACA at much higher voltages in the dozen or so pages I've read.
I ask because while I bought some Chinese Zen V4 boards, that was only a few dollars investment, and I am now trying to decide whether Zen V4 at 50+ volts or a pair of custom built ACA (turbo) amps is the right build. What I am looking for is the highest power best sounding single mosfet amp.
Between zen boards, DIY PSU boards, transformer, parts and a case, I am looking at a minimum of $700 for a Zen.
SoundWaveSteve:Have built the premium version with upgraded mosfets and supplied a second SMPS -- one for each board. Each at 24vdc with an added 1500uf cap.Have since added the rkthatcher CLC filter to the incoming SMPS voltage. The dual smps ACA amp sounds great AND has enough power to blow you into another dimension -- although I should stress that I am using high efficiency Tekton speakers. Check my posts above in this thread for more specifics.
Interesting! And this uses the ACA boards but with a bunch of new parts? I will definitely hunt that down from earlier in the board to read about the results. Thanks for replies!
There is an extra resistor, labeled R3, 6k8 on that schematic. It drops the voltage into the drain of the input JFet. The ACA boards can be tweaked to add this part. The rest of the parts fit onto the board.
I made a mistake and ordered 100uf silmic cap instead of 10uf for the input cap c3 will this be okay to use? Thanks for your help
Hi,
Could someone kindly confirm the it is OK to substitute the 3 below original values to the ones in bold?
R15 from 2.21Kohm to 2K2 0.5W
R12 from 39.2Kohm to 39K 0.5W
Rl0 from 332Kohm to 330K 0.5W
Regards
Bambos
Could someone kindly confirm the it is OK to substitute the 3 below original values to the ones in bold?
R15 from 2.21Kohm to 2K2 0.5W
R12 from 39.2Kohm to 39K 0.5W
Rl0 from 332Kohm to 330K 0.5W
Regards
Bambos