I would say it really depends what speakers one uses, their impedance and sensitivity.
I run a lightly modded ACA with a B1 as a pre. As we know B1 is a buffer, gain of 1.
But the speakers that I connect to it are 93 - 95 dB, 8ohm, plenty of volume, plenty of grunt.
I also tried for some time the ACA with a 12AH7 pre with gain of 10 with the same speakers. Volume control (the pot) needed to be between at 8-9 o'clock most of the time. Not a good combo.
So I guess 86dB speakers might benefit from a pre with high gain but the main thing is your speakers will tell you what pre you need.
pstefan98,
I am happy with the solid state version of the Freya. I use it to preamp my ACA XLR Pair and my Sansui Amp as RCA at the same time. I only have one on at a time, as both are outputting at the same time, And, the relay noise is easily ignored.
Web cut and paste: FREYA S: PASSIVE OR ACTIVE SOLID STATE REMOTE BALANCED PREAMP $599 https://www.schiit.com/products/freya-s
I am happy with the solid state version of the Freya. I use it to preamp my ACA XLR Pair and my Sansui Amp as RCA at the same time. I only have one on at a time, as both are outputting at the same time, And, the relay noise is easily ignored.
Web cut and paste: FREYA S: PASSIVE OR ACTIVE SOLID STATE REMOTE BALANCED PREAMP $599 https://www.schiit.com/products/freya-s
That particular chassis mount SMPS wouldn't necessarily be an upgrade over the ACA kit brick style on its own. What you do with the rest of your build could be an upgrade. The bricks were well chosen for this task.
Those chassis mount SMPS can take some external capacitance on their output. You could try a simple CRC or CLC filter. There is a potential to improve power delivery. A lot has been written on this topic in the DIY VFET amp, part 2. You might hear a startup noise due to the supply hiccup feature for starting into larger capacitance. Whether there is an overall improvement with this configuration is up to you.
I tried using one of the 27V Meanwell chassis mount supplies in one of my Hafler chassis ACAs. The ACA boards I'm using have CRC filters to the tune of 10,000 uF > 0.1 Ohm > 10,000 uF. The SMPS seemed to perform fairly well, but I prefer the sound of the linear supply that have built for these amps. The linear supply performs best at lower frequency extension and definition.
Those chassis mount SMPS can take some external capacitance on their output. You could try a simple CRC or CLC filter. There is a potential to improve power delivery. A lot has been written on this topic in the DIY VFET amp, part 2. You might hear a startup noise due to the supply hiccup feature for starting into larger capacitance. Whether there is an overall improvement with this configuration is up to you.
I tried using one of the 27V Meanwell chassis mount supplies in one of my Hafler chassis ACAs. The ACA boards I'm using have CRC filters to the tune of 10,000 uF > 0.1 Ohm > 10,000 uF. The SMPS seemed to perform fairly well, but I prefer the sound of the linear supply that have built for these amps. The linear supply performs best at lower frequency extension and definition.
Thank you for your reply. I think I’d like to peruse the linear power supply option. Is there a DIY BUILD GUIDE or thread that would help have a BOM and guide me through the process of building a linear power supply? Would the universal power supply boards in the DIYaudiostore be a good starting point. Or, could you recommend and a viable retail version?
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Well. there is this:
https://www.diyaudio.com/community/threads/aca-amp-with-premium-parts.328357/post-5565678
Building a linear supply for the ACA is definitely a more advanced endeavor. Fortunately it can be done with a single power transformer, where each of the secondary windings powers one of the two channels. There is a lot of reading to do before you decide to commit to this path. Please do your homework first.
https://www.diyaudio.com/community/threads/aca-amp-with-premium-parts.328357/post-5565678
Building a linear supply for the ACA is definitely a more advanced endeavor. Fortunately it can be done with a single power transformer, where each of the secondary windings powers one of the two channels. There is a lot of reading to do before you decide to commit to this path. Please do your homework first.
You can jump forward to pages 6 & 7 of that thread to see where this is headed. I had some modified boards built to manage higher voltage power supplies. R16 is an addition that does not exist on stock ACA boards, but can be added with some care. It is necessary to go safely above 25V.
Hey, hows your headphone mod, I'm planning to do a ACA for headphones as well. What did you change in the end?
Hello team,
This is my first try at building a amplifier, almost all parts where sourced locally. Assembled PCBs were bought by a friend of mine. Used CAD to design some chassis around heat sinks.
Using Meanwell SMPS 24v 8.8a to power these.
I just finished building both of these, I have few questions:
I am a noob at all this, yet trying to learn as much as I can.
Here are some pictures:
This is my first try at building a amplifier, almost all parts where sourced locally. Assembled PCBs were bought by a friend of mine. Used CAD to design some chassis around heat sinks.
Using Meanwell SMPS 24v 8.8a to power these.
I just finished building both of these, I have few questions:
- I have used a 2watt 39k resistor on for the switch, will it make a difference for not using 0.25w?
- One heat sink gets warmer than the other, bias and voltage is corrected. 24v and 12 for bias. (Yet to try the 2nd amp just finished it yesterday)
I am a noob at all this, yet trying to learn as much as I can.
Here are some pictures:
@amrutmhatre90
You're fine with the 2W resistor.
It doesn't seem like you're making a good thermal connection between the output transistors and the heat sinks. What did you use as an insulator?
You're fine with the 2W resistor.
It doesn't seem like you're making a good thermal connection between the output transistors and the heat sinks. What did you use as an insulator?
Maybe good to use some large shims to secure output devices to even out the pressure on the devices?
I was thinking if it was a good idea to rotate the PSU 180 degree to have much shorter mains wires to the PSU?
Now mains wires pass very close to the one amp board. The magnetic fields can introduce some hum to the amp.........
Generally a good idea also not to have signal wires close to the Meanwell PSU transformer.
I was thinking if it was a good idea to rotate the PSU 180 degree to have much shorter mains wires to the PSU?
Now mains wires pass very close to the one amp board. The magnetic fields can introduce some hum to the amp.........
Generally a good idea also not to have signal wires close to the Meanwell PSU transformer.
yeah, same parts used accross.
I tested the other amp, and it evenly dissipates heat on both heatsinks.
@charles34 I am using Soundartist LS3/5a with these amps, and they do drive them.