I would recommend building a higher voltage linear supply to get higher power per channel. I suppose you could also find a 27V or higher SMPS brick if you wanted to try that instead. Part of the power limitation of the regular ACA is the supply voltage. The circuit can make good use of a better PSU if you are willing to build your own.
Can you elaborate on the "don't have to be identical" comment. Is it a "it really doesn't matter" or is it a "you could get away with it" type of comment?
Because you could get away with a car with four different sizes of wheels, but it wouldn't drive smooth or be durable. If you use different finishings for your seats, on the other hand, it really wouldn't matter.
So which is this scenario? Thanks.
Rafa.
Just as the Zen V4 is capable of using different types of Mosfets in the different positions, so is the ACA. Done with some thought about the different roles of each device, this may even have some benefits to the sound of the amp. The upper device is simply an interactive current source, while the lower device is the controller.
This is DIY; try it and see if you like it.
This is DIY; try it and see if you like it.
I have been using 28 volts with the original modified ACA from this thread and noticed it sounded much better than it did when it was at 20. My meanwell won’t supply more than 28 with the voltage adjustment cranked to its limits, I often wonder if it would stay in the operating region at 30-32 volts.
Higher voltage with 4 ohm speakers?
Is there any advantage to using the IRFP140 with higher voltage in a parallel mono setup for 4 ohm speakers? I always thought that for 4 ohm speakers one had to decrease the voltage and increase the current. Am I wrong about that with the ACA? What would be the best current/voltage combination for parallel mono in that situation? I would like to be able to use the ACA chassis from the diyaudio store, would the heatsinks on that chassis limit the current in my build?
Thanks for any insight you can provide.
Jazzzman
Is there any advantage to using the IRFP140 with higher voltage in a parallel mono setup for 4 ohm speakers? I always thought that for 4 ohm speakers one had to decrease the voltage and increase the current. Am I wrong about that with the ACA? What would be the best current/voltage combination for parallel mono in that situation? I would like to be able to use the ACA chassis from the diyaudio store, would the heatsinks on that chassis limit the current in my build?
Thanks for any insight you can provide.
Jazzzman
As previous posts have mentioned, running the IRFP140 with higher voltage is beneficial. The higher voltage helps (slightly) with improved transconductance, as well as lowered parasitic capacitance. Mainly, the device will be closer to its "sweet spot" of linear operation.
Using the ACA in a parallel mono setup is also beneficial for some types of speakers, including those with lower impedance. In addition to parallel mono, I recommend changing R3 and R4 to 0.56 Ohms in order to increase the bias current. Also change C1 to 4700 uF, Nichicon KG series.
Probably the biggest improvement will be upgrading the power supply to a linear one. I recommend the Antek AS-3222 or AS-3224. This will feed the amp boards with a better supply of clean current. A single stereo chassis can be configured as a dual-mono amp this way, and parallel mono can be configured with a back panel switch with some thought. This has been covered previously in this thread.
The smaller 2U Mini-Dissipante chassis will be difficult to work with, but the 3U Mini-Dissipante chassis is just the right size.
Using the ACA in a parallel mono setup is also beneficial for some types of speakers, including those with lower impedance. In addition to parallel mono, I recommend changing R3 and R4 to 0.56 Ohms in order to increase the bias current. Also change C1 to 4700 uF, Nichicon KG series.
Probably the biggest improvement will be upgrading the power supply to a linear one. I recommend the Antek AS-3222 or AS-3224. This will feed the amp boards with a better supply of clean current. A single stereo chassis can be configured as a dual-mono amp this way, and parallel mono can be configured with a back panel switch with some thought. This has been covered previously in this thread.
The smaller 2U Mini-Dissipante chassis will be difficult to work with, but the 3U Mini-Dissipante chassis is just the right size.
Jazzzman, I expect the Dissipante-3U-case (heatsink: 300 x 120 x 40mm) to have a thermal resistance of about 0.5 - 0.6C/W.
As comparison I took a Fischer SK 47 heatsink (the one that I am using).
If your ACA will ever produce 50VA per channel, this will contribute 50 x (0.5 - 0.6) °C to the surrounding temperature (say: 22°C)
and will then result in about 50 - 55°C heatsink-temperature.
This is o.k. - Rudi
As comparison I took a Fischer SK 47 heatsink (the one that I am using).
If your ACA will ever produce 50VA per channel, this will contribute 50 x (0.5 - 0.6) °C to the surrounding temperature (say: 22°C)
and will then result in about 50 - 55°C heatsink-temperature.
This is o.k. - Rudi
Hoping to get some help for a friend that now has 5 amp camps and attempting to run his Klipsch Jubilee HF (horns only) on balanced XLR. At first, he was running two amp camps in stereo but tried balanced expecting higher output on his 8 ohm horns but he is getting 5db less vs running RCA bridged. Does anyone know why this is? I checked wiring multiple times and it’s correct. Below is his setup.
Marantz 7703 XLR outs using MOGAMI XLR cables
..into XILICA XP- 4080. DSP signal processors. XLR outs to ACA amps
Each amp has the premium parts upgrades done.
Marantz 7703 XLR outs using MOGAMI XLR cables
..into XILICA XP- 4080. DSP signal processors. XLR outs to ACA amps
Each amp has the premium parts upgrades done.
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open dedicated thread, posting exact schematic of build and some pictures, if needed
before that , do homework:
- using any signal source capable of producing 400-500Hz sine , measure what's signal level going in amp with RCA (hot to gnd) and what's level of signal outputing from amp in SE mode (loaded with speaker or not) , measuring hot to gnd speaker terminals
- using same signal source , measure what's signal level going in amp with RCA (hot to gnd) and what's level of signal outputing from amp in inherently bridged mode(loaded with speaker or not) , measuring hot to hot speaker terminals
- using same signal source , measure what's signal level going in amp with XLR (pin 1 to pin 2) and what's level of signal outputing from amp in normally (not inherently) bridged mode(loaded with speaker or not) , measuring hot to hot speaker terminals
post then your measurements
before that , do homework:
- using any signal source capable of producing 400-500Hz sine , measure what's signal level going in amp with RCA (hot to gnd) and what's level of signal outputing from amp in SE mode (loaded with speaker or not) , measuring hot to gnd speaker terminals
- using same signal source , measure what's signal level going in amp with RCA (hot to gnd) and what's level of signal outputing from amp in inherently bridged mode(loaded with speaker or not) , measuring hot to hot speaker terminals
- using same signal source , measure what's signal level going in amp with XLR (pin 1 to pin 2) and what's level of signal outputing from amp in normally (not inherently) bridged mode(loaded with speaker or not) , measuring hot to hot speaker terminals
post then your measurements