Its obvious you have problems with the way you do it
The way you handle your electronics
Your complete setup is probably an issue too
How old are you
You dont sound very young
Yet you seem to lack basic knowledge of how to handle electronics
Your asking fore help is fine
But I think you should make a dedicated thread
I think your whole setup needs revision
It should be done step by step in every detail
Pictures of every part of your setup etc
Its very likely you do have a problem somewhere in your setup
It could be anything, simple or complicated
And you need to find it
Its obvious you need help with this
Until you have located the problem any kind of listening impressions are pointless
This thread is about listening impressions
You need a thread about fault finding
The way you handle your electronics
Your complete setup is probably an issue too
How old are you
You dont sound very young
Yet you seem to lack basic knowledge of how to handle electronics
Your asking fore help is fine
But I think you should make a dedicated thread
I think your whole setup needs revision
It should be done step by step in every detail
Pictures of every part of your setup etc
Its very likely you do have a problem somewhere in your setup
It could be anything, simple or complicated
And you need to find it
Its obvious you need help with this
Until you have located the problem any kind of listening impressions are pointless
This thread is about listening impressions
You need a thread about fault finding
Hi Professor smith,
Right now I'm going to comment on what I have seen from your posts and your own pictures you have showing your construction of a B1 buffer.
It is obvious that you don't understand electronics very well, that's okay. The problem is that you are not willing to accept that something you have done may be at fault here. I see plenty of evidence that you don't understand how to dress your wiring, and that is critical in any equipment. You can be presented with a perfectly working, wired amplifier and destroy that performance simply by changing the wires between components, or even changing the positions of the original wires. From what I can see, your lead dress is terrible (looking at the B1). Bad enough to cause performance problems.
From what I can see, your best course of action would be to take your amplifier and documentation to a really good audio technician and pay to have him assemble your amplifier properly. This person will not be a TV technician, or a computer technician. That person will be someone who specializes in audio equipment and is well known to be an excellent technician. Otherwise, accept that you have created some trouble and work to fix your errors before throwing up your hands and blaming the amplifier modules.
You could start by posting some pictures of your amplifier internal connections. That would be step one before asking for any help. We can not see how you put it together, so most of us would assume you did a good job. I learned a long time ago that this would be a bad assumption.
As far as Hugh is concerned, I know him to be an honest, straight forward person from exchanging communication for a few years. I do not own any of his products, in fact I have never even seen one. I do have over 30 years in the consumer and pro audio industry in service, and I have had to support customer built kits. There is no kit designed that will avoid customer errors. Heck, customers even blow up built units!
-Chris
Right now I'm going to comment on what I have seen from your posts and your own pictures you have showing your construction of a B1 buffer.
It is obvious that you don't understand electronics very well, that's okay. The problem is that you are not willing to accept that something you have done may be at fault here. I see plenty of evidence that you don't understand how to dress your wiring, and that is critical in any equipment. You can be presented with a perfectly working, wired amplifier and destroy that performance simply by changing the wires between components, or even changing the positions of the original wires. From what I can see, your lead dress is terrible (looking at the B1). Bad enough to cause performance problems.
From what I can see, your best course of action would be to take your amplifier and documentation to a really good audio technician and pay to have him assemble your amplifier properly. This person will not be a TV technician, or a computer technician. That person will be someone who specializes in audio equipment and is well known to be an excellent technician. Otherwise, accept that you have created some trouble and work to fix your errors before throwing up your hands and blaming the amplifier modules.
You could start by posting some pictures of your amplifier internal connections. That would be step one before asking for any help. We can not see how you put it together, so most of us would assume you did a good job. I learned a long time ago that this would be a bad assumption.
As far as Hugh is concerned, I know him to be an honest, straight forward person from exchanging communication for a few years. I do not own any of his products, in fact I have never even seen one. I do have over 30 years in the consumer and pro audio industry in service, and I have had to support customer built kits. There is no kit designed that will avoid customer errors. Heck, customers even blow up built units!
-Chris
Hi Mark A. Gulbrandsen,
I haven't checked in for a while, but I should comment here.
There is nothing wrong with an HP 339A at all. It's oscillator has about 0.0018% THD, a touch lower actually. It measures this residual pretty closely, which tells me the filter / metering circuits are doing a bit better.
I should look up your Sound Technology. I know it's also pretty good, but they usually have switch problems by now. However, I wouldn't knock either instrument.
I got rid of a few newer THD meters that were bought new. The old HP 339A is a better THD analyzer. I am also going to restore an HP 334A THD meter, because it's high frequency response is better than most products. BTW, look at the HF performance of both the HP 339A and your ST model (which one is it?). If your HF response is too low, your unit will be outperformed by the HP, simply because the HP "sees" the higher harmonics where others will not.
One of my newer THD meters promised response out to a few hundred KHz. Imagine my surprise when I found out that it really started rolling off at 30 KHz! I should have measured it when I got it, but I trusted that manufacturer. No, there was no low pass filter. Just a 400 Hz high pass.
I think it's important that we look at all performance specs before commenting on test equipment (or audio equipment for that matter). Some of that old stuff really does perform better that one would expect. So, for now I will happily continue to use my two HP 339A THD analyzers. They perform identically - always a good sign. I must admit that I did have to clean the switches though.
-Chris
I haven't checked in for a while, but I should comment here.
There is nothing wrong with an HP 339A at all. It's oscillator has about 0.0018% THD, a touch lower actually. It measures this residual pretty closely, which tells me the filter / metering circuits are doing a bit better.
I should look up your Sound Technology. I know it's also pretty good, but they usually have switch problems by now. However, I wouldn't knock either instrument.
I got rid of a few newer THD meters that were bought new. The old HP 339A is a better THD analyzer. I am also going to restore an HP 334A THD meter, because it's high frequency response is better than most products. BTW, look at the HF performance of both the HP 339A and your ST model (which one is it?). If your HF response is too low, your unit will be outperformed by the HP, simply because the HP "sees" the higher harmonics where others will not.
One of my newer THD meters promised response out to a few hundred KHz. Imagine my surprise when I found out that it really started rolling off at 30 KHz! I should have measured it when I got it, but I trusted that manufacturer. No, there was no low pass filter. Just a 400 Hz high pass.
I think it's important that we look at all performance specs before commenting on test equipment (or audio equipment for that matter). Some of that old stuff really does perform better that one would expect. So, for now I will happily continue to use my two HP 339A THD analyzers. They perform identically - always a good sign. I must admit that I did have to clean the switches though.
-Chris
I've got a possibility for your issues here...
Power.
It is possible that the power going into your house is 'different' at times and this can sure affect the sound. The load on the grid will vary, therefore affecting the 'cleanliness' of the power. I'm not quite sure how to test this without a really nice meter, but I do believe this would explain why it sounds good at times and not at others.
I just feel that by your posts it seems to be an outside factor, not the amplifiers.
-West
Power.
It is possible that the power going into your house is 'different' at times and this can sure affect the sound. The load on the grid will vary, therefore affecting the 'cleanliness' of the power. I'm not quite sure how to test this without a really nice meter, but I do believe this would explain why it sounds good at times and not at others.
I just feel that by your posts it seems to be an outside factor, not the amplifiers.
-West
anatech said:
Chris
There is almost zero chance that I have done something wrong to this amp. It came ready built and all I did was solder a few wires. The bias and dc offset are slightly high but this is nothing to do with what I have done. I am not blaming the amp or anybody but I am abit frustrated that it doesnt sound the same all the time when I want to use it and moreover I dont even know why this is.
I am simply stating an observation I have made about the sound of the amp. Various people are telling me various things. Hugh tells me its a burn in issue, you are saying its the way Ive put it together, while others have even said its my imagination. So who is right?? Whos advice do I believe?
How does positioning of the wires in the B1 have any effect? Nelson recommends building it using point to point wiring. There are no stray magnetic fields so I do not see how the position matters.
Professor smith said:
If you have been working inside amps that have been powered up, there is a possibilty to disturb curcuits
Power supply caps should always be discharged with power resistor before touching anything
That goes fore both your Aksa and B1 pre
B1 point to point wired 🙄
Are you sure that works properly
Are your fets matched
How big is your cap on output
Its size should be calculated accordingly to your power amp input impedance
If Poweramp impedance is low, it needs a big cap on pre, or you will loose lowend
That will most likely sound awful
As i recal, no lowend was one of your first complains
Well, just thought whether you have a "leaking" cap somewhere
A diode not working
A wrong mounted resistor
something
Have you tried with other amps, preamps
Does that change anything
Please, you will need to do so
Slightly high bias and DC
How high is that
How much does it fluctuate
Monitor over a period and check if it changes much
Lots of questions
Some are just thoughts
Others need answers
Member
Joined 2009
Paid Member
I'm the least qualified to comment here, but I'll share some thoughts.
We have a dissatisfied Prof. Smith, his sound system does not behave consistently (problem 1) and one of the modes in which it operates has for him poor sound quality (problem 2).
Next we have long-distance technical support via email, a method of communication that is notorious for being problematic. Even between people working at a Company in the same building I have seen issues where information is misunderstood, intent and emotion is misconstrued. And we have a forum where several Chef's are in the kitchen trying to sort out the problem, each with a different suggestion.
Regardless of what theories people may have of Prof. Smiths intentions or skills, this isn't a great situation for him.
Having one person on this forum (if not Hugh) take the lead in helping Prof. Smith would be one way to simplify the communication. Somebody with the right experience would be even better. If Prof. Smith would then agree to follow the instructions given accurately then a set of tests and analysis could be performed and others on the forum could offer their advice for the nominated 'helper' to consider before providing follow-up instructions for Prof. Smith.
If this isn't scientific enough, you could consider some traditional fault finding methods such as the Fish Bone diagram. Work out the possible factors impacting the results from the sound system and work down each one as you go instead of jumping around from idea to idea based on what appears to be the most obvious cause from the little data available.
I marvel at how Hugh has managed his business with the difficulties of remote technical support.
We have a dissatisfied Prof. Smith, his sound system does not behave consistently (problem 1) and one of the modes in which it operates has for him poor sound quality (problem 2).
Next we have long-distance technical support via email, a method of communication that is notorious for being problematic. Even between people working at a Company in the same building I have seen issues where information is misunderstood, intent and emotion is misconstrued. And we have a forum where several Chef's are in the kitchen trying to sort out the problem, each with a different suggestion.
Regardless of what theories people may have of Prof. Smiths intentions or skills, this isn't a great situation for him.
Having one person on this forum (if not Hugh) take the lead in helping Prof. Smith would be one way to simplify the communication. Somebody with the right experience would be even better. If Prof. Smith would then agree to follow the instructions given accurately then a set of tests and analysis could be performed and others on the forum could offer their advice for the nominated 'helper' to consider before providing follow-up instructions for Prof. Smith.
If this isn't scientific enough, you could consider some traditional fault finding methods such as the Fish Bone diagram. Work out the possible factors impacting the results from the sound system and work down each one as you go instead of jumping around from idea to idea based on what appears to be the most obvious cause from the little data available.
I marvel at how Hugh has managed his business with the difficulties of remote technical support.
Member
Joined 2009
Paid Member
I walked into that didn't I !
- I disqualify myself on the basis that I haven't built an amplifier yet
- I disqualify myself on the basis that I haven't built an amplifier yet
Hi Gareth,
Oh yeah!
You suggested it, now its yours - own it and smile!
Nothing I have read so far has indicated that Professor smith has approached troubleshooting this methodically. Questions were asked and a round of interesting answers appeared. There has been no real technical effort on Professor smith's part to solve this. I don't doubt Professor smith has tried some things, just not much that I have seen that had a hope of working, save putting the system back the way it was once he heard it and liked it. Could be wrong about this, just nothing posted to indicate any real effort to really solve the issue(s).
Hi Professor smith,
There is no need to quote entire large posts. That's a waste of space and doesn't help anyone.
So, let's attempt to help you out some. I expect some effort on your part as well. Some of that effort may take the form of you studying some concepts if you don't understand. Like the following comments ...
I did touch on that in my previous reply to you. You have got to read what people post if you want to learn anything.
Lead dress is critical some times. It certainly is in power amplifiers. Improper wire routing (or dressing) can make an amplifier smoke and die, or just sound bad. This is an incredibly important concept. You must read up on this.
This is why I told you to pay to have your amp repaired. From the pictures you have, I know you don't know how to wire anything up. Sorry, but that is the truth.
We need to start fresh.
I haven't seen your amplifier yet. No one can say anything with any certainty until we can see it. I extrapolated your problems from what I saw you do to your B1. You are lucky the B1 is a low gain device, mind you it may still be misbehaving. You don't have any way to tell what is what.
When you build anything, you really should have a decent meter and oscilloscope. It sounds like you have some kind of meter, and that's a good start.
If you ask why you should have an oscilloscope, you didn't really read my second quote from you. An oscilloscope is used to check for noise, ripple or oscillation. It can show you a very distorted waveform, but below a couple percent THD, you really need to use a distortion analyzer of some type. Ask a technician nicely to help you.
I'm trying to help you Professor smith. Some of that requires me to shock you into the real world where people make mistakes and stuff burns up.
-Chris
Oh yeah!
You suggested it, now its yours - own it and smile!
Nothing I have read so far has indicated that Professor smith has approached troubleshooting this methodically. Questions were asked and a round of interesting answers appeared. There has been no real technical effort on Professor smith's part to solve this. I don't doubt Professor smith has tried some things, just not much that I have seen that had a hope of working, save putting the system back the way it was once he heard it and liked it. Could be wrong about this, just nothing posted to indicate any real effort to really solve the issue(s).
Hi Professor smith,
There is no need to quote entire large posts. That's a waste of space and doesn't help anyone.
So, let's attempt to help you out some. I expect some effort on your part as well. Some of that effort may take the form of you studying some concepts if you don't understand. Like the following comments ...
If you stay that course, nothing you attempt to troubleshoot will ever work. Always assume that you made an error when something doesn't work properly. I do, and therefore do normally catch my silly errors.
Exactly!!!!
I did touch on that in my previous reply to you. You have got to read what people post if you want to learn anything.
Lead dress is critical some times. It certainly is in power amplifiers. Improper wire routing (or dressing) can make an amplifier smoke and die, or just sound bad. This is an incredibly important concept. You must read up on this.
This is why I told you to pay to have your amp repaired. From the pictures you have, I know you don't know how to wire anything up. Sorry, but that is the truth.
Intended or not, you took this out on Hugh. We know you are frustrated. We also know that you don't know why. It's time to learn - yes?
That tends to happen when there is no method or process in troubleshooting a problem.
We need to start fresh.
Judging from what I saw in your B1 pictures, yes I am. However, I did clearly ask you to post internal pictures of your amplifier.
I am. You must believe me beyond anyone else.
I haven't seen your amplifier yet. No one can say anything with any certainty until we can see it. I extrapolated your problems from what I saw you do to your B1. You are lucky the B1 is a low gain device, mind you it may still be misbehaving. You don't have any way to tell what is what.
When you build anything, you really should have a decent meter and oscilloscope. It sounds like you have some kind of meter, and that's a good start.
If you ask why you should have an oscilloscope, you didn't really read my second quote from you. An oscilloscope is used to check for noise, ripple or oscillation. It can show you a very distorted waveform, but below a couple percent THD, you really need to use a distortion analyzer of some type. Ask a technician nicely to help you.
Unwanted coupling of signals between different parts of a circuit. Look it up - please?
Like everything else, there are correct ways to do things, and incorrect ways. Your B1 is not wired properly and if it does work properly, its only due to the low gain of Nelson's circuit design. Nelson is an excellent designer, but even he checks his work. If you have not measured the distortion of your B1, you have no clue whether it is working properly or not. Believe it. There must be some reason they make all that expensive test gear (and why many of us buy it).
Oh man!! You really don't understand what's going on at all, do you? You are surrounded by both magnetic and "e" fields. Every current carrying wire sets up a magnetic field. Every potential generates an "e" field. Your preamp generates some of it's own fields, just not very much. Now think here, if there are no fields to worry about, why on earth does shielded wire exist? Why do we use metallic enclosures to house most electronic assemblies? Even the magnetic field generated by the earth affects equipment. Every CRT oscilloscope needs to have it's beam corrected to counter the effects of the earth's magnetic field. That is a weak field by the way.
No. I am pointing out what I can see wrong with it. If you don't like the word "wrong", let's use the term "substandard". You are just learning how to wire things up. Take some pride in your work and learn how to do things properly. The performance gains are worthwhile. Example, how many threads here are there related grounding?This many!
I'm trying to help you Professor smith. Some of that requires me to shock you into the real world where people make mistakes and stuff burns up.
-Chris
I've stayed fairly quiet about this so far, but I suggest Kenji (aka Professor Smith) start taking responsibility for his actions, his understanding, and his expectations. Kenji, you're going to have to start thinking for yourself instead of depending on others to do all your thinking, then trying to decide who to believe. "Professor" indeed!
And you're going to have to take responsibility for properly dealing with technical support and communications concerns. As I understand it, Hugh has graciously fielded over 60 emails and even some direct phone calls. He also offers a dedicated technical support forum, and despite that, you insist on make this everyone else's problem by complaining on a public forum, a DIY public forum no less. DIY is an acronym for "do it yourself". This is an amazing forum for sharing and contributing, not for expecting others to do unto you.
If you spent as much time educating yourself and reading these forums, as you have spent peppering these forums with impossible questions, you'd probably have your problem solved by now. Learn by reading first (I recommend 3 years minimum), then specific questions, not nebulous unanswerable ones.
..Todd
And you're going to have to take responsibility for properly dealing with technical support and communications concerns. As I understand it, Hugh has graciously fielded over 60 emails and even some direct phone calls. He also offers a dedicated technical support forum, and despite that, you insist on make this everyone else's problem by complaining on a public forum, a DIY public forum no less. DIY is an acronym for "do it yourself". This is an amazing forum for sharing and contributing, not for expecting others to do unto you.
If you spent as much time educating yourself and reading these forums, as you have spent peppering these forums with impossible questions, you'd probably have your problem solved by now. Learn by reading first (I recommend 3 years minimum), then specific questions, not nebulous unanswerable ones.
..Todd
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Joined 2009
Paid Member
anatech said:Hi Gareth,
Oh yeah!
You suggested it, now its yours - own it and smile!
IN that case I volunteer 😀
I'll re-read over the past few pages and get back to you....
Member
Joined 2009
Paid Member
Here's what I can try to summarize from what was posted, but I didn't see the many emails that have been going around:
Kenji - can you check what I've written and tell us if any facts are wrong and if any facts are missing ?
And the next step would be for the guru's on this forum to see if any conclusions or opinions are wrong or missing, to suggest some missing possible causes and suggest how they could be tested to prove or eliminate them ?
Remember - I never build an amplifier or heard of AKSA til a few weeks ago!
The System:
AKSA 55N+
Source with pre-am and DAC
Statement of the Problem:
initially worked fine, after 24hrs for two weeks (= 336 hrs) with no changes to any components in the system:
a) the bass 'disappeared'
b) dynamics 'gone'
c) transparency 'gone'
Conclusions at this point: all parts of the system, including the amplifier started off fine, so this specific copy of the amplifier was 'good' when it left Hugh and it was 'good' when it arrived in London.
Proposed Cause of the problem:
1) the amplifier is defective, it may have got like this after system integration or have developed a latent defect from before it was purchased
2) the implementation of the amplifier into the box and into the system is flawed but the amplifier module is fine
3) another component in the system is defective
4) the amplifier or another system component is sensitive to some unknown environmental factor
5) the observer is human and like the rest of us, can't consistently evaluate the system performance
Analysis:
1) amplifier is defective (something that changes with time) ?
1.1) Bootstrap Capacitor Burn-in: Black gate capacitor is installed in the amplifier and are notorious for their inconsistent and lengthy settling-in period. I believe BG cap is in the C4 Bootstrap role and this is known to impact Bass sound. Capacitors are one of the least reliable components in any piece of electronics, not just audio. BG caps are also obsolete, the factory shutdown several years ago and there is little information on their shelf-life (i.e. not subjected to polarizing potentials). The behaviour of these caps is strange, so we haven't eliminated this as the cause of the problem yet.
Option: replace the BG caps with Nichicon MUSE (I have a 220uF one in TGM1, I can provide a cap for this experiment).
Option: wait even longer time for settling-in
Option: replace with another BG (from Hugh who has stock)
1.2) drift in amp biasses: I don't see how small drifts in dc-offset or output device biass will produce the observed behaviour ?
1.3) Input Capacitor Burn-in: this cap also can impact bass quite a lot. Don't know if BG is used in this position, I thought this one is usually upgraded to something else. Same comments as 1.1).
1.4) defective semi-conductor devices on input (e.g. poor LTP pair sounds bad): issue would have to vary with time/temperature.
Option: ?
2) amplifier implementation
2.2) poor power supply: what can change over time here ? could it be defective capacitors ? - usually this just makes 'hum' and this wasn't a reported problem. Poor regulation or something that increases the power supply impedance would cause rails to sag under load and big bass swings - but not sure what could cause this only from time to time ?
2.3) poor wiring: suggestions are contamination by mutual inductance between wires and amplifier. Such things usually require a high fluctuating current in one wire, contaminating the signal in another wire and the wires need to be coupled, especially if they run parallel to each other. It can also happen if there is mutual capacitance between wires and these thins usually require a high voltage fluctuation in one wire contaminating an adjacent wire. Fluctuating signals can the AC line voltage, which in the UK is at 50Hz and the harmonics. This usually causes 'hum' and this isn't part of the problem reported. Kenji provided a photograph for us to study. To me, it doesn't look to be a problem. The signal input wires are pairs (so signal contamination would appear on signal and signal gnd which the amplifier will reject fairly well); plus these wires cross others at right angles so coupling will be low. I don't see an earth to the heatsink*
Option: ?
2.4) oscillating amplifier: will affect the sound, reduce dynamics and transparency. The standard AKSA has the usual inductor on the output mounted underneath the pcb from the output devices to the output connecting lug - I assume it exists on this copy ? Could the non-earthed heatsink be an issue, it would allow anything coupled into it capacitively from the output devices to be felt by the drivers and the VBE device ?
Option: add earth strap.
3) Another component is at fault ? - seems unlikely that this would happen just when Kenji gets a new amplifier.
4) Environmental Factors or other components ?
4.1) AC mains fluctuations: could cause line voltage changes. I still wouldn't see this aligning well with the observed problem ?
4.2) AC mains contamination: isn't this usually just producing HF noise - can it kill bass ?
Option: ?
4.3) RF interference getting into amplifier from an intermittent source: could this spoil the sound ? - I don't think the amp has any RF protection on it. This could be added.
Options: add RF supressor at the input.
4.4) Speaker problems: what could be the issue, over-heating of voice-coil ?
4.5) Faulty Elma switch in pre-amp: swapping around to different source/pre-amp didn't help. Eliminated this cause.
4.6) Pre-amp needs relatively low output impedance to get the best out of AKSA (B1 buffer not best match?): a low impedance source was tried and didnt' help, and since the problem was not present to start with this cause is Eliminated.
5) Observer not consistent ? -
5.1) seating position: Kenji has compared like with like so this can't be the cause
5.2) observer not an impartial judge ?
Option: Kenji could get a friend to listen when it's 'good' and again when it's 'bad'
Kenji - can you check what I've written and tell us if any facts are wrong and if any facts are missing ?
And the next step would be for the guru's on this forum to see if any conclusions or opinions are wrong or missing, to suggest some missing possible causes and suggest how they could be tested to prove or eliminate them ?
Remember - I never build an amplifier or heard of AKSA til a few weeks ago!
The System:
AKSA 55N+
Source with pre-am and DAC
Statement of the Problem:
initially worked fine, after 24hrs for two weeks (= 336 hrs) with no changes to any components in the system:
a) the bass 'disappeared'
b) dynamics 'gone'
c) transparency 'gone'
Conclusions at this point: all parts of the system, including the amplifier started off fine, so this specific copy of the amplifier was 'good' when it left Hugh and it was 'good' when it arrived in London.
Proposed Cause of the problem:
1) the amplifier is defective, it may have got like this after system integration or have developed a latent defect from before it was purchased
2) the implementation of the amplifier into the box and into the system is flawed but the amplifier module is fine
3) another component in the system is defective
4) the amplifier or another system component is sensitive to some unknown environmental factor
5) the observer is human and like the rest of us, can't consistently evaluate the system performance
Analysis:
1) amplifier is defective (something that changes with time) ?
1.1) Bootstrap Capacitor Burn-in: Black gate capacitor is installed in the amplifier and are notorious for their inconsistent and lengthy settling-in period. I believe BG cap is in the C4 Bootstrap role and this is known to impact Bass sound. Capacitors are one of the least reliable components in any piece of electronics, not just audio. BG caps are also obsolete, the factory shutdown several years ago and there is little information on their shelf-life (i.e. not subjected to polarizing potentials). The behaviour of these caps is strange, so we haven't eliminated this as the cause of the problem yet.
Option: replace the BG caps with Nichicon MUSE (I have a 220uF one in TGM1, I can provide a cap for this experiment).
Option: wait even longer time for settling-in
Option: replace with another BG (from Hugh who has stock)
1.2) drift in amp biasses: I don't see how small drifts in dc-offset or output device biass will produce the observed behaviour ?
1.3) Input Capacitor Burn-in: this cap also can impact bass quite a lot. Don't know if BG is used in this position, I thought this one is usually upgraded to something else. Same comments as 1.1).
1.4) defective semi-conductor devices on input (e.g. poor LTP pair sounds bad): issue would have to vary with time/temperature.
Option: ?
2) amplifier implementation
2.2) poor power supply: what can change over time here ? could it be defective capacitors ? - usually this just makes 'hum' and this wasn't a reported problem. Poor regulation or something that increases the power supply impedance would cause rails to sag under load and big bass swings - but not sure what could cause this only from time to time ?
2.3) poor wiring: suggestions are contamination by mutual inductance between wires and amplifier. Such things usually require a high fluctuating current in one wire, contaminating the signal in another wire and the wires need to be coupled, especially if they run parallel to each other. It can also happen if there is mutual capacitance between wires and these thins usually require a high voltage fluctuation in one wire contaminating an adjacent wire. Fluctuating signals can the AC line voltage, which in the UK is at 50Hz and the harmonics. This usually causes 'hum' and this isn't part of the problem reported. Kenji provided a photograph for us to study. To me, it doesn't look to be a problem. The signal input wires are pairs (so signal contamination would appear on signal and signal gnd which the amplifier will reject fairly well); plus these wires cross others at right angles so coupling will be low. I don't see an earth to the heatsink*
Option: ?
2.4) oscillating amplifier: will affect the sound, reduce dynamics and transparency. The standard AKSA has the usual inductor on the output mounted underneath the pcb from the output devices to the output connecting lug - I assume it exists on this copy ? Could the non-earthed heatsink be an issue, it would allow anything coupled into it capacitively from the output devices to be felt by the drivers and the VBE device ?
Option: add earth strap.
3) Another component is at fault ? - seems unlikely that this would happen just when Kenji gets a new amplifier.
4) Environmental Factors or other components ?
4.1) AC mains fluctuations: could cause line voltage changes. I still wouldn't see this aligning well with the observed problem ?
4.2) AC mains contamination: isn't this usually just producing HF noise - can it kill bass ?
Option: ?
4.3) RF interference getting into amplifier from an intermittent source: could this spoil the sound ? - I don't think the amp has any RF protection on it. This could be added.
Options: add RF supressor at the input.
4.4) Speaker problems: what could be the issue, over-heating of voice-coil ?
4.5) Faulty Elma switch in pre-amp: swapping around to different source/pre-amp didn't help. Eliminated this cause.
4.6) Pre-amp needs relatively low output impedance to get the best out of AKSA (B1 buffer not best match?): a low impedance source was tried and didnt' help, and since the problem was not present to start with this cause is Eliminated.
5) Observer not consistent ? -
5.1) seating position: Kenji has compared like with like so this can't be the cause
5.2) observer not an impartial judge ?
Option: Kenji could get a friend to listen when it's 'good' and again when it's 'bad'
I should hope that they arent going around. They were private messages exchanged between us.
hi,
The heatsink is bolted (hence earthed) to the chassis which is earthed and the star earth is also connected to the chassis. The picture doesnt show everything because it was taken before it was finished.
Point 5 about the observer:
How does 'audio memory' conspire to prevent an accurate judgement of sound from one day to another?
From my experience 'audio memeory' is reset after a period of say 7 to 10 days.
I am focussing on the observer aspect because ultimately we have a very precarious situation where there is no way to correlate this apparent change in sound with any given cause(s) since there are so many factors which could all be playing a part.
Really, after looking at the photo of your amp, the first thing that comes to my mind, is a bad solder joint.
Your soldering skills are sub-standard (thanks Chris), to be honest they look very sub-standard.
Magura 🙂
Your soldering skills are sub-standard (thanks Chris), to be honest they look very sub-standard.
Magura 🙂
Professor smith said:
I would say Sound Quality memory isnt more than 7-10 minutes or even much less.
It all boils downto how to define 'memory' and the quality of this remembered stuff,
of course 😉
This is an interesting thing to debate, as we all in audio, some way or another, finally are dependent on what goes into our ear(s) and mind(s).
Some have only one ear intact. And some have one new mind for each and every day = change their mind as frequently as their mood changes.
For example a few impulsive hotblooded from near or south of the equatorial border.
/lineup
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