ACA amp with premium parts

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#1,001
Zamjazz27 said:
I have done all of the upgrades that Tungsten has provided so those input caps have been upgraded, maybe not to a crazy level. I know that the output coupling cap is pretty important from a sound quality standpoint which is why I chose to try a new one in that spot. It would be interesting to think about what you could do there. I do think that with this last upgrade and running on 36v that I have achieved a really high level of extension, bass definition, I listen to a lot of acoustic jazz and I notice myself really following the rhythmic momentum of the walking bass lines and really hearing the definition of the attack of different players. The stock ACA sounds very veiled by comparison with a more over ripe and bloated bass.
I don't know how much more punishment my boards can take as far as part switching, those boards are so robust! but maybe the bug will bite me again and I'll put some 6800-10,000uf caps on the output coupling and look out those other caps, but I don't think they are holding things back...
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Hello Zamjazz27,

Thanks for your feedback. What is the input capacitance you are using in your build? I plan to use film cap which is not very expensive. I have the Axon true cap left over from B1 build long time back. I am thinking of giving this a try. It wont fit on the boards but I will try to get it in some way.

Thanks
 
#1,002
Some here may recall that I didn't change C3, which is an Elna Silmic 10uF, 50V electrolytic. These are excellent caps. If one were curious to try something else, then another one to try would be the Nichicon UES 2.2uF, 50V, which is a bipolar electrolytic. Film caps can be 1.0 uF, or even less. Look at the value of R10 to determine the Fc of the input RC network.
 
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#1,009
TungstenAudio said:
BTW, if you want to hear what an ACA is really capable of, build a linear power supply. Start with an Antek 300VA, 25V. For simplicity use a Vishay VS-26MB40A bridge rectifier for each channel; CRCRC supply filter with around 22,000 uF at each C. It can be made point-to-point.
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I think this is part of why the dual smps sound so much better than the single, I think it gets you part of the way to the benefits of a linear. I am going to start putting the pieces together for a 36v LPS.
 
#1,010
baswamin said:
Ah, which are the other two you tried?
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Stock 3300, Nichicon KG 4700, and now the Mundorf. I switched to the Mundorf at the same time that I also went dual smps at 36v. I do think that the Mundorf is responsible for better definition in the bass and much more clarity and transparency in the midrange, I would say the Nichicon KG was a little warmer and less detailed, but I can't directly AB. I have another ACA, single 36v smps, so I may play around with changing C2, and C4, and try a larger C1. If I like that I can always drop the boards into the one I have wired for dual SMPS. Or probably I should just build up a clean set of boards!

But I am sure TA is right and that going linear is probably the big improvement rather than spending to much time fussing over each cap. It really is fun to experiment though!
 
#1,011
I am working through the upgrades for the premium parts mod. I wanted to ask on how to add the 10pf silver mica caps in parallel with the 90k resistor. Is this simply soldering it across the leads to the resistor.
My 4700 C1 caps should arrive Monday. I have everything else in place, minus the 10pf silver mica. It is a definite change already but initially a little bright in the upper frequency. How much should the 10pf help soften that and will some hours also smooth things out.
 
#1,013
motospark said:
Hi, I finally have all the performance parts for my two Amps. While test fitting I ran into this issue the upgrade for R12 is a Vishay 1/2 watt 90.9k ohms and is a little larger than the pads. I came up with this idea that I have see on older equipment. I figure I will tack on the Mica to the bottom of the board or in between the arch of the Vishay on top. Any thoughts. See Pic.

Mark
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Nice placement. I got the 90.9K 1/4 watt resistor, per another recommendation, and I must admit the small size of the 1/4 watt has me a bit worried about its suitability. Should I take it out and go with the 1/2 watt before I fire my amps up?

David
 
#1,014
scottsabo said:
I am working through the upgrades for the premium parts mod. I wanted to ask on how to add the 10pf silver mica caps in parallel with the 90k resistor. Is this simply soldering it across the leads to the resistor.
My 4700 C1 caps should arrive Monday. I have everything else in place, minus the 10pf silver mica. It is a definite change already but initially a little bright in the upper frequency. How much should the 10pf help soften that and will some hours also smooth things out.
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Which transistors did you go with? I think that the FGH44N10 offers the best balance, the IRFP140's sounded a little tilted up on the high end, that said I am using Klipsch Rp600m's which already have a little rise in the high end. Tungsten is right, you really do have to rung things in a while, especially when you put the C1 cap in.
 
#1,015
Zamjazz27 said:
Which transistors did you go with? I think that the FGH44N10 offers the best balance, the IRFP140's sounded a little tilted up on the high end, that said I am using Klipsch Rp600m's which already have a little rise in the high end. Tungsten is right, you really do have to rung things in a while, especially when you put the C1 cap in.
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Zamjazz
I went FQH44N10 in Q1 and stock Q2. I just installed the mica across the 90k resistors at R12. I need some time to let them settle in but it seems to have eased the top end a bit. This mod is definitely more dynamic and give a nice presentation. It is a bit bright on my Klipsch. Though Klipsch tends to be a little forward by nature.
Before I added the micas at R12 I found running parallel mono eased the top end presentation. I’m not sure on the 600m but my RP5000f dip to 4ohms in the lower frequency. The way power is delivered in parallel mode seems to ease the top end into a very sweet spot.

Thanks to everyone who helped me mod my amps. Very fun and somehow everything worked the first time…. No smoke!!

Now onto speaker cap and binding post upgrades!

Jazz hit me up if you have modded your 600m’s I would love to hear
 
#1,016
Craigl59 said:
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.
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