Hi Rocket,
I am glad that your amps are coming together with a sound that you are
pleased with. I know it is very satisfying🙂
I am glad that your amps are coming together with a sound that you are
pleased with. I know it is very satisfying🙂
Hey there, there is a mistake on the parts list spreadsheet earlier in this thread, that mouser part# is for a 90.9ohm resistor instead of 90.9k
Are you all using 1/4w or 1/8w resistors for the 90.9k and 20k?
Are you all using 1/4w or 1/8w resistors for the 90.9k and 20k?
For general info, I have for some time been using the 044N's in both the Q1 and Q2 position in my amp camp. I chose them for their more robust lower registers in the sound.
Recently I came across a CD of Motets, and by chance, I was listening through my headphones. I was taken with the clarity and resolution of the voices coming through to my ears! I then decided to give a listen through my open baffle speakers, and was disappointed with the mush of sounds. I auditioned all of my amps, a transistor Scott, and my modified B&K ST-140 with increased bias, and then my amp camp that had the 044N's. The amp camp had the best resolution of the three, but it was still lacking the clarity and resolution I heard with my headphones. I went back through my notes, and recalled my use of the Cree C3M0065090, a 900 volt part, searching for something with the character of the expensive and rare Semi Mosfets that was the topic of conversation a year ago.
I replaced my Q1&2 with the Cree parts, which I had, but seem to be on back order at Mouser, and no stock at DigiKey either. For what it is worth, the clarity and smoothness of their sound is very good, and far superior to the 044N's, and any of the other parts I have experimented with. There is slightly less bass, but the upper and mid-range is seductive and clear. I don't know if anyone has the Cree's, but I would suggest that they are really worth a listen. I am certainly leaving them in place.
I suppose musical preferences are always subject to change, we are human, but I am glad to have come back home to the Cree's.
Recently I came across a CD of Motets, and by chance, I was listening through my headphones. I was taken with the clarity and resolution of the voices coming through to my ears! I then decided to give a listen through my open baffle speakers, and was disappointed with the mush of sounds. I auditioned all of my amps, a transistor Scott, and my modified B&K ST-140 with increased bias, and then my amp camp that had the 044N's. The amp camp had the best resolution of the three, but it was still lacking the clarity and resolution I heard with my headphones. I went back through my notes, and recalled my use of the Cree C3M0065090, a 900 volt part, searching for something with the character of the expensive and rare Semi Mosfets that was the topic of conversation a year ago.
I replaced my Q1&2 with the Cree parts, which I had, but seem to be on back order at Mouser, and no stock at DigiKey either. For what it is worth, the clarity and smoothness of their sound is very good, and far superior to the 044N's, and any of the other parts I have experimented with. There is slightly less bass, but the upper and mid-range is seductive and clear. I don't know if anyone has the Cree's, but I would suggest that they are really worth a listen. I am certainly leaving them in place.
I suppose musical preferences are always subject to change, we are human, but I am glad to have come back home to the Cree's.
Well, life happened. I'm only now starting to build the premium ACA.
One thing though, I want to double check the correct place for R16.
Is my assumption correct that I can cut the indicated trace and add a 500 ohm resistor there? I can't see anything else the will be affected, but you never know.
Also, is the 2SK170GR the right type for Q4? I have a few from the 90's when I build a Hiraga Le Monstre.
One thing though, I want to double check the correct place for R16.
Is my assumption correct that I can cut the indicated trace and add a 500 ohm resistor there? I can't see anything else the will be affected, but you never know.
Also, is the 2SK170GR the right type for Q4? I have a few from the 90's when I build a Hiraga Le Monstre.
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Hi Strongbow,
you can cut the trace on the board, or you can just trim the drain leg of Q4, and solder the resistor to the trimmed leg. Just take case to not overheat Q4. I then slipped a piece of insulation over the leg to make sure it didn't short to the middle leg. Either way works fine. Not sure about the letter classification on your Q4, as I just used the ones from DIY. The letters delineate the specifics on the 2SK's.
Someone will chime in on that one🙂
you can cut the trace on the board, or you can just trim the drain leg of Q4, and solder the resistor to the trimmed leg. Just take case to not overheat Q4. I then slipped a piece of insulation over the leg to make sure it didn't short to the middle leg. Either way works fine. Not sure about the letter classification on your Q4, as I just used the ones from DIY. The letters delineate the specifics on the 2SK's.
Someone will chime in on that one🙂
Hi dfoulk,
Doing it your way wont work, then R16 and C4 wont form a low pass filter. And C4 will not be parallel to drain of Q4.
Or am I missing something?
Doing it your way wont work, then R16 and C4 wont form a low pass filter. And C4 will not be parallel to drain of Q4.
Or am I missing something?
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Strongbow,
Perhaps you are right, and putting the resistor where you have it marked will serve better. I do not know if the effect of the resistor is entirely negated placing it on the drain leg instead of in the cut trace. I have increased C4 to 1000uf.
To be sure, I would put the resistor in the cut trace.
Search for Tungsten's posted schematic for ACA mods for reference.
Perhaps you are right, and putting the resistor where you have it marked will serve better. I do not know if the effect of the resistor is entirely negated placing it on the drain leg instead of in the cut trace. I have increased C4 to 1000uf.
To be sure, I would put the resistor in the cut trace.
Search for Tungsten's posted schematic for ACA mods for reference.
Completed mods but haven't attempted R16 yet
So I have implemented Tungsten's mods and the amp sounds so much more open. I really think a single stereo amp with this mod sounds better than two unmodded amps in balanced mono by far, will start working on the second one.
Also, I'm curious to know more about how the sound improvements are achieved, I understand the parts upgrade will lead to a lot more clarity, what did the change in resistor values do? change negative feedback?
I'm am really shocked by the improvement!
I didn't install the R16, how important is this to the sound? and is there a clear tutorial/picture/instructions for where this resistor goes?
So I have implemented Tungsten's mods and the amp sounds so much more open. I really think a single stereo amp with this mod sounds better than two unmodded amps in balanced mono by far, will start working on the second one.
Also, I'm curious to know more about how the sound improvements are achieved, I understand the parts upgrade will lead to a lot more clarity, what did the change in resistor values do? change negative feedback?
I'm am really shocked by the improvement!
I didn't install the R16, how important is this to the sound? and is there a clear tutorial/picture/instructions for where this resistor goes?
Hi, to whom upgraded C1 from 3300uF to 4700uf does it only increase bass or the upgrade to Gold Tune caps has more impact on overall sound quality? As my speakers are bass generous already i need to think twice here. Thanxs
I am still breaking in the mods on my first amp. What I am hearing is more detail in the bass and tighter overall bass response. It does not sound bloated at all. I don't hear anything so far that would make me concerned about having too much bass. It sounds very accurate to what is on the recording.
Hello.
A couple of quick questions:
1: If I want to lower the gain, I can reduce R12!?
2: If I reduce R12 / increase feedback, will this increase the damping factor?
3: Running at 24V, is the preferred size of R16 still around 200 ohm?
Thank ya'll.
🙂
A couple of quick questions:
1: If I want to lower the gain, I can reduce R12!?
2: If I reduce R12 / increase feedback, will this increase the damping factor?
3: Running at 24V, is the preferred size of R16 still around 200 ohm?
Thank ya'll.
🙂
Are the 2 ohm resistors added in parallel to both R3 and R4 or just one on R4? Are we adding 2 resistors per side or just one?
Thanks!
Thanks!
Hello, ACA pundits. Am new to the forum and to amp building and have ordered the ACA v.1.8 along with the caps and resistors specified by the august TungstenAudio. This is a “bucket list” project and am already blessed with high-bias class A monoblocks (Emotiva XPA-1s) and 300B SET tube amplifiers. My goal is to build a working amp to learn some basic design and construction skills then to use this “true” class A amp to compare with a high-bias amp (that suffers, of course, from the crossover issue) and see what, if any, differences are audible.
Have read through this impressive thread and there appears to be an original upgrade that employed these capacitor and resistor changes/additions, then a more refined version using Rudi's board with additional items and board changes, then a great deal of further refinement that is way past my comprehension.
Want to build a single unit at first to check the above class A question and develop simple skills. Will there, consequently, be an improvement to the stock 1.8 version using just the caps and resistors shown in TungstenAudio's post 31? There are so many paths to choose from here that a beginner such as myself needs to identify one simple upgrade path.
Have got all of the 1.8 items from DIY Audio but the case has not been shipped. Elena! Got any news? Ordered the upgrade components from Mouser and Parts Connexion and have most of them.
SO..should a beginner just go for the stock board and components, or is it worthwhile to start with the refinements shown in the Post #31?
AND...want to thank all of the creative/brilliant minds that make this thread so helpful. You folks are the best.
Have read through this impressive thread and there appears to be an original upgrade that employed these capacitor and resistor changes/additions, then a more refined version using Rudi's board with additional items and board changes, then a great deal of further refinement that is way past my comprehension.
Want to build a single unit at first to check the above class A question and develop simple skills. Will there, consequently, be an improvement to the stock 1.8 version using just the caps and resistors shown in TungstenAudio's post 31? There are so many paths to choose from here that a beginner such as myself needs to identify one simple upgrade path.
Have got all of the 1.8 items from DIY Audio but the case has not been shipped. Elena! Got any news? Ordered the upgrade components from Mouser and Parts Connexion and have most of them.
SO..should a beginner just go for the stock board and components, or is it worthwhile to start with the refinements shown in the Post #31?
AND...want to thank all of the creative/brilliant minds that make this thread so helpful. You folks are the best.