Many thanks!
I currently have a pair of ACAs and run them in balanced monoblock mode with an XLR connection. I pulled one amp from duty for the upgrade and put the other in single ended stereo mode for the time being. I was quite struck with how different the amp sounded. I found that I really prefer balanced monoblock, but everybody's system (all the way to your ears) is different.
I currently have a pair of ACAs and run them in balanced monoblock mode with an XLR connection. I pulled one amp from duty for the upgrade and put the other in single ended stereo mode for the time being. I was quite struck with how different the amp sounded. I found that I really prefer balanced monoblock, but everybody's system (all the way to your ears) is different.
Oh - what about the IRFP240s - Q1 and Q2? Should they also remain connected to the boards? This may have been what I meant - but last night was Saturday night so ... 🍸
Yes, it will be easier and safer to leave the big Mosfets connected as well.
.. Unless you want to try something different, such as IRFP140s.
.. Unless you want to try something different, such as IRFP140s.
Tungsten: I know this post was in reference to boards from Rudi_Ratlos but I believe it is an option for the standard ACA boards. As I take the V+ from the V+ line I will be adding the suggested 100uF cap in parallel. Since the cap is a polarized electrolytic does the negative lead of the cap see the V+ first, or the other way around? Here's a crude drawing. Which is strangely huge. Thank you.
Attachments
Got it. I'm looking at the original schematic and understand what you are describing. Thanks.
Also - this makes adding R16 much easier. I was devising in my head some way of adding the cap then piggybacking the resistor on to the leads. 😉
Also - this makes adding R16 much easier. I was devising in my head some way of adding the cap then piggybacking the resistor on to the leads. 😉
One pair of boards done. My photos are not up to the Puma Cat standard... I'm doing all the soldering from the back side since I zorched one wire when uninstalling. The R16 part of the work is challenging but once you do one the rest go fairly easily. I built up 4 R16s so that the next time I install them it should go faster. I wanted a mechanical connection along with the electrical so that when the amp heats up it will keep from taking itself offline - which is why I created that particular share with the leads.
I'll bias these up to - I think 12.4 as per this thread since I plan on monoblock usage - and move on to the next amp soon. Lots of fun to get this far!
BTW - if anyone sees anything peculiar with my board feel free to tell me I'm going to set the house on fire.
I'll bias these up to - I think 12.4 as per this thread since I plan on monoblock usage - and move on to the next amp soon. Lots of fun to get this far!
BTW - if anyone sees anything peculiar with my board feel free to tell me I'm going to set the house on fire.
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Doing power on voltage checks. Things good so far. I have the original Tungsten upgrades, 24V PS and the original IRFPs. Tungsten's post on the first page of this thread says bias at 12.4, however I saved off a jpeg at some point (attached) that says 12.9. I do notice that the attached jpeg version has the older biasing scheme. Which one is right?!
Thanks!
Also, here is the final build (for now).
Thanks!
Also, here is the final build (for now).
Attachments
Let’s call it a range of values that may be set according to one‘s preference.
Maybe start with 12.4V, listen to the amp for some time (day or three), then try 12.6 or 12.9V. See if one of those sounds nicer for you.
This ‘bias’ will introduce slight asymmetry to the output as the amp is driven harder. There may be little noticeable affect under moderate listening levels.
If you choose to eventually power the amp from a higher voltage, the bias will scale proportionally.
Maybe start with 12.4V, listen to the amp for some time (day or three), then try 12.6 or 12.9V. See if one of those sounds nicer for you.
This ‘bias’ will introduce slight asymmetry to the output as the amp is driven harder. There may be little noticeable affect under moderate listening levels.
If you choose to eventually power the amp from a higher voltage, the bias will scale proportionally.
Fascinating. Thank you!
Why does the voltage change as the amp heats up? I had set these at 12.4V earlier today but powered them up just now and they are slowly drifting from about 12.6-ish downwards towards the probable 12.4V.
Why does the voltage change as the amp heats up? I had set these at 12.4V earlier today but powered them up just now and they are slowly drifting from about 12.6-ish downwards towards the probable 12.4V.
It's difficult to install a new or updated component without taking just a bit of time to listen. I think a break in period longer than an hour is probably better, but I couldn't resist. My build has mostly the same parts list as the Tungsten build although I've substituted a Mundorf M-Lytic for C1.
By the way, I am only running one updated amp in stereo mode. It is set up for monoblock use but only one of the two has been completed.
The first thing I noticed was a much more clearly defined space around any part of the music. Even on the same recording. For instance, Pat Metheny's Secret Story has orchestra mixed with his at-that-time band. The songs can be complex and dense which is why it's fun to test with. I've heard this album countless times, but never heard the reverb around his band to be so different than the reverb around the orchestra. Nice.
The bass is now more extended and articulate. The high end is clean, although my current setup is a bit dry so I can't say for sure what is likely there.
But the thing I hear most of all is an elegance to the music. It's relaxed and, well, musical. More flow. More dynamic without being in your face. It seems almost like someone swapped my original amp for a different brand.
The only thing I think I might be hearing is a slight balance issue which is interesting to me. It may be my room or it may be real. Will wait for more break-in and likely test it from the binding posts at some point later in the week.
That's all for now. I have hours and hours of music cued up on my server so that the new components can break in during the day.
Many thanks to Nelson Pass for the original design and James (TungstenAudio) for his work in updating the ACA.
By the way, I am only running one updated amp in stereo mode. It is set up for monoblock use but only one of the two has been completed.
The first thing I noticed was a much more clearly defined space around any part of the music. Even on the same recording. For instance, Pat Metheny's Secret Story has orchestra mixed with his at-that-time band. The songs can be complex and dense which is why it's fun to test with. I've heard this album countless times, but never heard the reverb around his band to be so different than the reverb around the orchestra. Nice.
The bass is now more extended and articulate. The high end is clean, although my current setup is a bit dry so I can't say for sure what is likely there.
But the thing I hear most of all is an elegance to the music. It's relaxed and, well, musical. More flow. More dynamic without being in your face. It seems almost like someone swapped my original amp for a different brand.
The only thing I think I might be hearing is a slight balance issue which is interesting to me. It may be my room or it may be real. Will wait for more break-in and likely test it from the binding posts at some point later in the week.
That's all for now. I have hours and hours of music cued up on my server so that the new components can break in during the day.
Many thanks to Nelson Pass for the original design and James (TungstenAudio) for his work in updating the ACA.
Hi bhjazz. I haven't finished my ACA build yet so I cannot comment on that example. But your desciption of the effects of installing Mundorf M-lytic capacitors match my own experience in several builds and modifications. They do seem to clarify and clean up complex music, but also expose bad recordings.
Hey Grunnet! I was laughing at your comment about exposing bad recordings because that happened during my initial listen. No kidding. Things were going along just fine and I was having fun. But I put on some vinyl from 1979 and suddenly the party stopped dead. Makes me laugh now. I think any good components will lay bare bad recordings and even bad components upstream. As we get closer to the (musical recording) truth, sometimes the truth hurts!
the FQH44N10 are out of stock. Can the base model IRFP240 can still be used with the modded unit?
IRFP140 is out of stock Mouser or Digikey
Would the 240 work or not ? I have a bunch coming my way
Would the 240 work or not ? I have a bunch coming my way