Hey there, Thanks, I'm all over the thread, did all the upgrades and am running dual mono with 36V supplies, it is killer. You mentioned somewhere that you keep coming back to this amp even though you have built some other first watt designs, and that is a comparison that I am really interested. I have the FQH44N10 ant T1 and T2, as I thought that sounded a little warmer/fuller but I know the 140 is a great fit at T2. I may build another set of boards, I'd love to try a 10,000uf at C1 with a 1.5uf bypass cap like a huge miflex and get creative with placement....I'd also like to see what I can fit on the input side to swap out the smaller polymer caps. I love experimenting with this amp.... that said, I am not going to touch the one I am using now with the full mods and dual mono 36v, I have it running a pair of very modified Klipsch Forte1's and it is amazing!
Honestly I'm a little surprised that nobody seems to have built an "ACA hedgehog" with premium parts. It has the advantage of being a monoblock so the channel separation is off the charts. And variants have been offered which include a 4 pole LCLC filter right on the PCB, to clean up the power supply rail and attenuate SMPS noise tremendously. (LINK 1) , (LINK 2) .
The on-PCB filter is an exact copy of the SMPS filter currently sold in the diyAudio Store (LINK 3) . The filter is capable of 3 Amps DC and 48 volts DC, so it has loads of safety margin in an ACA monoblock application where the current drawn is less than 2 amps and the voltage is less than 30 volts.
By the way, the Saturday Amp Camp project at the 2022 Burning Amp Festival next month, has attendees building a stereo pair of the Hedgehog amps, sans filter. It remains to be seen whether the provided kits will include Premium Parts or not.
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The on-PCB filter is an exact copy of the SMPS filter currently sold in the diyAudio Store (LINK 3) . The filter is capable of 3 Amps DC and 48 volts DC, so it has loads of safety margin in an ACA monoblock application where the current drawn is less than 2 amps and the voltage is less than 30 volts.
By the way, the Saturday Amp Camp project at the 2022 Burning Amp Festival next month, has attendees building a stereo pair of the Hedgehog amps, sans filter. It remains to be seen whether the provided kits will include Premium Parts or not.
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Heatsinks can you have to much sink?
I am building my own cases for two ACA Premium MonoBlocks 36V SMPS with FQH44N10's
It has been mentioned that they like to run hot. Is it best to do some kind of a heat calculation to get the right temperature or can any size heat sink be use?
Secondly 36v brick sold at the DIY audio store has 4 pins 2 + and 2 - those of you building 36v dual SMPS are you using ONE power brick using the one pair of pins for each channel
or
2x 36v SMPS with the pins bridged?
Thanks for reading.
I am building my own cases for two ACA Premium MonoBlocks 36V SMPS with FQH44N10's
It has been mentioned that they like to run hot. Is it best to do some kind of a heat calculation to get the right temperature or can any size heat sink be use?
Secondly 36v brick sold at the DIY audio store has 4 pins 2 + and 2 - those of you building 36v dual SMPS are you using ONE power brick using the one pair of pins for each channel
or
2x 36v SMPS with the pins bridged?
Thanks for reading.
Regarding the 36V SMPS, the V+ and V– pins are electrically connected at the power brick. If you wanted a separate power for each channel, you would need two SMPS bricks. Better still, build a dual-mono linear supply in a separate chassis, and use a custom umbilical wire to power the amp. That way the V+ and V– pins in the connector can be kept isolated from each other and directly connected to the separate PSU for each channel.
Amazing find this site. This will be my first experience with a class A amp and building an amp kit. I have two v1.8 kits on order. I know quality parts matter, so I want to built it right.
I've looked at all of the posts and am humbled by all of the knowledge and experience, far beyond mine, in this field.
I plan to run them in bridge monoblocks with the delivered power supplies. I cannot see ever building my own LPS given that it would be well beyond my skillset and concerns regarding safety issues for self and property.
Focusing mostly on TungstenAudio's insight this is what seems like the best parts given my planned setup, but I did have a couple of questions.
Decisions that seem clear:
C1: 4700 uF, 35V; Nichicon KG series "Gold Tune"
C2: 1000 uF, 16V; Nichicon RNL series Aluminum Organic Polymer
C4: 100 uF, 35V; Nichicon RL8 series Aluminum Organic Polymer
R11: 20 kOhm, 1/4W, 1% metal film (Input Resistor), stock was 10k
R12: 90.9 kOhm, 1/4W, 1% metal film (Feedback Resistor), stock was 39.2k
68.1K bridge Resistor (R16) to replace the stock 39k
Decisions that I need guidance on:
1) FQH44N10 in Q1 seems clear, but I am not clear at all what should be in Q2? FQH44N10 or IRFP240? I saw several references to IRFP140 but that part wasn't on the V1.6 components list. I couldn't find a v1.8 parts list.
2) .5ohm 3W to replace stock R4 resistor, instead of using the 2.0 Ohm resistor in parallel to R2 and R4. But then does it require a reset of the bias voltage to 12.4V? Wasn't clear here to me at all?
Would appreciate any help. Thank you.
I've looked at all of the posts and am humbled by all of the knowledge and experience, far beyond mine, in this field.
I plan to run them in bridge monoblocks with the delivered power supplies. I cannot see ever building my own LPS given that it would be well beyond my skillset and concerns regarding safety issues for self and property.
Focusing mostly on TungstenAudio's insight this is what seems like the best parts given my planned setup, but I did have a couple of questions.
Decisions that seem clear:
C1: 4700 uF, 35V; Nichicon KG series "Gold Tune"
C2: 1000 uF, 16V; Nichicon RNL series Aluminum Organic Polymer
C4: 100 uF, 35V; Nichicon RL8 series Aluminum Organic Polymer
R11: 20 kOhm, 1/4W, 1% metal film (Input Resistor), stock was 10k
R12: 90.9 kOhm, 1/4W, 1% metal film (Feedback Resistor), stock was 39.2k
68.1K bridge Resistor (R16) to replace the stock 39k
Decisions that I need guidance on:
1) FQH44N10 in Q1 seems clear, but I am not clear at all what should be in Q2? FQH44N10 or IRFP240? I saw several references to IRFP140 but that part wasn't on the V1.6 components list. I couldn't find a v1.8 parts list.
2) .5ohm 3W to replace stock R4 resistor, instead of using the 2.0 Ohm resistor in parallel to R2 and R4. But then does it require a reset of the bias voltage to 12.4V? Wasn't clear here to me at all?
Would appreciate any help. Thank you.
On the
68.1 kOhms bridge Resistor (R16) to replace the stock 39k - is there more specification on that resistor for watts, types, etc. Having trouble narrowing that part down since it is generic and 'many' options. Suggestions?
I never use the ACA bridged, but for safety, I would think a 1/2 watt would be fine 🙂
<The FQH44N10 would be a good choice for Q1, leaving the IRFP140 at Q2>. Can you help me understand this. Is Q2 using IRFP140 a typo? When I look at the ACA v1.6 Component List, It has stock Q1/Q2 as IRFP240. And as far as I am able to determine, the ACA v1.8 kit uses IRFP240 as well. Please advise.
Funny you mentioned that, I actually just plugged in my other ACA which has 140 at Q2 and FQH44N10 at Q1.
Amp 1: All tungsten upgrades, FQH44N10 at Q1 and Q2, Thatcher filter, Dual 36v Meanwell supplies
Amp 2: All Tungsten upgrades, FQH44N10 at Q1 and Q2, No power fliter, Mundorf AG 4700uf at C1, Single Meanwell 36v (I just need to rewire it to take two supplies)
Bias on both is 18.5v
So I'm not sure why any of this is true but: Amp 1 is more transparent, more extended up high and revealing, more drive. That said, i am really enjoying Amp 2, it is more at ease, maybe a little more effortless and throws a big soundstage, warmer more like a tube amp...
My guesses: the thatcher dc filter gives you more details but things sound not as relaxed to me. The Mundorf is a high quality cap for sure maybe that is where the soundstage is coming from. The difference in Q2.... I thought when I was running 24v supplies that the 140 sound was brighter and the FQH was richer...now I am not so sure.
I plan on building a fresh set of boards and putting them in a much bigger case because running at 36v I need the heatsinks to be way bigger, and building a linear power supply. The question is which transistors would I choose after all this experimenting, definitely FQH in Q1... I'm going to do some more listening. I may have changed over to the 140 in Q2 camp. Maybe a bigger Mundorf or Audi Note in C1, 10,000, with a 1.5uf bypass if I can figure out where to put it...
Running hot is an understatement. You can barely touch them...at 18.5v bias. I bought 36v Meanwells from Parts Express that at the correct connector/pins
https://www.parts-express.com/Mean-...pter-with-2.5-x-5.5mm-Center-Positive-129-225
These worked great, I have tested them 1 per amp, or dual on one amp, worked great. I even ran monoblock with two supplies on one amp, although meanwell recommends against that.
My favourite configuration is a single amp, running stereo with dual mono 36v power supplies. There is something transparently magical about optimising that single transistor output.
My System:
Thorens TD160 Super/ Rega Arm/ Hana EL MC
Hagerman Trumpet MC Phono preamp
Blue Sound Node 2i (for the rare times I digital)
Just auditioned a Chord Cutest DAC (it was amazing but decided not to pull the trigger on it)
Adcom GFP 750 Preamp
ACA Tungsten 36v
Klipsch Forte 1 heavily modified (cabinets braced and damped, stupid outboard DIY crossovers with ridiculous parts) this was my summer project
Having two bridged ACAs I'm following this thread with great interest and the results of the improvements seems to be great.
Is somewhere a summary with the latest status, or a circuit diagram, for the 36v version? Or is this info to be found scattered in the thread? Many thanks in advance.
Is somewhere a summary with the latest status, or a circuit diagram, for the 36v version? Or is this info to be found scattered in the thread? Many thanks in advance.
Hi! There is a lot of ideas on ACA PS, but has anyone built Le Monstre by Jean Hiraga? 8 W, 45 Ah car batteries and plenty of capacitors. I did and the sound was quite like ACA, detailed, soft and not so much power.
http://kaschei.com/classa/monster29.htm
http://www.diyaudioprojects.com/Solid/Jean-Hiraga-Le-Monstre/
http://kaschei.com/classa/monster29.htm
http://www.diyaudioprojects.com/Solid/Jean-Hiraga-Le-Monstre/
Attachments
It is definitely worth reading through the thread, the basic difference is going with FQH44N10 at Q1 and Q2 (or 140 at Q2). ((Tungsten is the 140 ok running at the higher voltage?))and upping the additional resistor to 1000k to protect the jfet. I would strongly consider a bigger case or fans, cause they run hot!
The sound is so good though. I think running the FQH biased at 18.5v sounds so solid, huge improvement for such a small investment in time and money.
Yes for sure, I found that the switch to FQH44N10's was huge, I think the 240's sound rolled off, diffuse, and unfocused in comparison. The FQH is both clearer and richer, and more extended at the frequency extremes.
I ran the FQH at Q1 and Q2 at 24v for quite a while before upping to 36v. At 24v it made a big difference, going to 36v made it even better.
As to if 140 or FQH is better at Q2 needs a little more experimentation....my thinking after playing with it a little is that it is not a huge difference. I'm thinking that the 140 at Q2 might soundstage better and possibly more extend up high, and the FQH may be fuller sounding...
Thanks. So at 24V are the Q1/Q2 pairs: FQH44N10/FQH44N10 or FQH44N10/ IRFP140 just considered simple drop-in replacements? Or are there resistor changes too necessary? Reading though the forum it is difficult to determine if any adjustments are necessary for Q1/Q2 changes when running at 24V. For 36V it is clear changes are required.
Yes, I'm in the process of getting the information from the thread. It's really worth.