Quote from Mr. Pass:
I waited for the amp to cool and then hooked up my digital volt meter. It read 3.5 volts. Both pcbs read about the same voltage at start up. I don't have the diff. pair physically touching, yet. I will eventually bolt an insolator and aluminum wedge between them. My x-over schematic appears to show caps on the outputs. Therefore, I assume that the answer is "no" when you asked if I'm running DC input. I matched all of my transistors to with in 0.01 volts. I'm currently running 11 volts per rail.
Here in Oregon, the word "exacerbate" has been floating around in the news channels for years.
John
I waited for the amp to cool and then hooked up my digital volt meter. It read 3.5 volts. Both pcbs read about the same voltage at start up. I don't have the diff. pair physically touching, yet. I will eventually bolt an insolator and aluminum wedge between them. My x-over schematic appears to show caps on the outputs. Therefore, I assume that the answer is "no" when you asked if I'm running DC input. I matched all of my transistors to with in 0.01 volts. I'm currently running 11 volts per rail.
Here in Oregon, the word "exacerbate" has been floating around in the news channels for years.
John
3.5V or 4V offset cold
I imagine that when the amp is switched on, the speaker corn would be pushed out (or in) giving a light popping sound and stay there. And the corn will be returned back to the almost neutral position little by little following the amp’s heat-up speed. It might take about half an hour or more to arrive to the neutral position.
If the offset is happening with the well matching pair of transistors, I guess that we could reduce it by increasing the negative feedback amount. Any has opinions?
JH
I imagine that when the amp is switched on, the speaker corn would be pushed out (or in) giving a light popping sound and stay there. And the corn will be returned back to the almost neutral position little by little following the amp’s heat-up speed. It might take about half an hour or more to arrive to the neutral position.
If the offset is happening with the well matching pair of transistors, I guess that we could reduce it by increasing the negative feedback amount. Any has opinions?
JH
jh,
we are talking ABSOLUTE DC OFFSET, NOT what it is seen by the speakers!!!!!!! I did my sharing BS'ing so you are forgiven. There is NO SPEAKER popping out and then back in!!! I am finding what Nelson finds, at the speaker, <10mV from the very start and absolute of maybe 3-400mV before everything settles down to ~0.
An earlier post asked about load, music in relation to DC offset: I do the DC balancing with NO LOAD, and no MUSIC, I hot plug the 8 ohm load, everything stays the same.
Like Nelson stated time and time again, load or no load the aleph don't care, they have their own problems managing the bias, load makes absolutely no difference at all.
When playing music with the input AC coupled the dc stays put. I have output caps on the BOSOZ so I will try to remove the input caps from the AX side to see what happens.
Don't be fooled by what your multimeter tells you when looking at mixed signals though!
we are talking ABSOLUTE DC OFFSET, NOT what it is seen by the speakers!!!!!!! I did my sharing BS'ing so you are forgiven. There is NO SPEAKER popping out and then back in!!! I am finding what Nelson finds, at the speaker, <10mV from the very start and absolute of maybe 3-400mV before everything settles down to ~0.
An earlier post asked about load, music in relation to DC offset: I do the DC balancing with NO LOAD, and no MUSIC, I hot plug the 8 ohm load, everything stays the same.
Like Nelson stated time and time again, load or no load the aleph don't care, they have their own problems managing the bias, load makes absolutely no difference at all.
When playing music with the input AC coupled the dc stays put. I have output caps on the BOSOZ so I will try to remove the input caps from the AX side to see what happens.
Don't be fooled by what your multimeter tells you when looking at mixed signals though!
don't frown......
My horns are 110 db 1w1m and I hardly notice a reduction in gain. In fact, the sparkle and lush musical reproduction quailities of this amp are impossible to ignore.
Because the AX sounds so good, I can learn to live with the fact that I must allow the amp an hour to thoroughly warm up (hugh massive heatsinks/chassis) to remove the dc offset. Honestly though, I'm the type of guy that carries a large bottle of aspirin around because I'm bothered by imperfection. Perhaps I'll discover a way to eliminate the dc offset from the get go, or, perhaps not.
Either way, this is one hell of a nice sounding amplifier and a project I wish I could have undertook 20 years ago.
John
My horns are 110 db 1w1m and I hardly notice a reduction in gain. In fact, the sparkle and lush musical reproduction quailities of this amp are impossible to ignore.
Because the AX sounds so good, I can learn to live with the fact that I must allow the amp an hour to thoroughly warm up (hugh massive heatsinks/chassis) to remove the dc offset. Honestly though, I'm the type of guy that carries a large bottle of aspirin around because I'm bothered by imperfection. Perhaps I'll discover a way to eliminate the dc offset from the get go, or, perhaps not.
Either way, this is one hell of a nice sounding amplifier and a project I wish I could have undertook 20 years ago.
John
Regarding Fred......
Fred and I are communicating via email. I am getting to know him and find that not only is he a source of valuable information, but is capable of being more down to earth than I could have imagined. I admit that, in the past, we have seen Fred's creative side unleashed, sometimes with less than positive results. But, I've also noticed that what triggers Fred's ire faster than greased lightning is people posting blatantly false or erroneous data or claims. If you're in the know, then post away. But, if you're just guessing; stop, or be ready to back up your claim. Fact of the matter is, the more I understand Fred, the more I appreciate his brand of genius.
John
Fred and I are communicating via email. I am getting to know him and find that not only is he a source of valuable information, but is capable of being more down to earth than I could have imagined. I admit that, in the past, we have seen Fred's creative side unleashed, sometimes with less than positive results. But, I've also noticed that what triggers Fred's ire faster than greased lightning is people posting blatantly false or erroneous data or claims. If you're in the know, then post away. But, if you're just guessing; stop, or be ready to back up your claim. Fact of the matter is, the more I understand Fred, the more I appreciate his brand of genius.
John
Bring Fred Back!
John,
I have been trying to tell that to members but for the most part his knowledge and practial no nonsense approach seems to have been ignored but by a few of us in the know. It seems most rather listen to someone that post pages and pages of nothing.
Jam
P.S. I sometimes wish they would bring back the days of the Brittanty Spears Fan Club and fat cats. Members seemed to be less uptight in those days.
John,
I have been trying to tell that to members but for the most part his knowledge and practial no nonsense approach seems to have been ignored but by a few of us in the know. It seems most rather listen to someone that post pages and pages of nothing.
Jam
P.S. I sometimes wish they would bring back the days of the Brittanty Spears Fan Club and fat cats. Members seemed to be less uptight in those days.
Hey John,
Good to see you are relaxed.
Proof in the pudding here here,
As a matter of interest I have my X Aleph up for 30 minutes now and have been able to null out the absolute dc almost completely, but at switch on not possible.
Is everyone running with .22 source resisters and one pair of devices per side @ 15 +- volts supply?
My readings are 0.5 volts all round, from this I concluded:
my measurements: for 15 volt supply => 0.50 v on 0.22 source resisters;
Calculation:
max swing is 19 volts ie 0.8 x supply rail. ie 45 watts for 8 ohms
So measured Bias is 0.5v/2.272A = 0.22 ohms, thats per pair, then multiply x 2 for both sides = 4.54 total bias current which gives about 86 watts @ 4 ohms, total dissapation is then 2.272 x 4 x 15 = 136 watts. Yes mate its bloody hot!
Am I correct with my calculation?.......Grey, Mr Pass, calling all cars......, anyone.. ... ... ..
Assuming this is the case:
If this is correct the bias can be ramped back if I don't need double power into 4 ohms, but say allow for 6 ohms say, we need 60 watts for a 19 volt swing, which is 3.16 amps total bias, /2 for bias for side is 1.58 amps, 0.5volts/1.58 = 0.315 ohms, 0.27 or .33 are peferred values.
This will reduce dissapation to 94.9 watts, about 30% less than previously.
Your feedback is appreciated!
ian
Good to see you are relaxed.
Proof in the pudding here here,
As a matter of interest I have my X Aleph up for 30 minutes now and have been able to null out the absolute dc almost completely, but at switch on not possible.
Is everyone running with .22 source resisters and one pair of devices per side @ 15 +- volts supply?
My readings are 0.5 volts all round, from this I concluded:
my measurements: for 15 volt supply => 0.50 v on 0.22 source resisters;
Calculation:
max swing is 19 volts ie 0.8 x supply rail. ie 45 watts for 8 ohms
So measured Bias is 0.5v/2.272A = 0.22 ohms, thats per pair, then multiply x 2 for both sides = 4.54 total bias current which gives about 86 watts @ 4 ohms, total dissapation is then 2.272 x 4 x 15 = 136 watts. Yes mate its bloody hot!
Am I correct with my calculation?.......Grey, Mr Pass, calling all cars......, anyone.. ... ... ..
Assuming this is the case:
If this is correct the bias can be ramped back if I don't need double power into 4 ohms, but say allow for 6 ohms say, we need 60 watts for a 19 volt swing, which is 3.16 amps total bias, /2 for bias for side is 1.58 amps, 0.5volts/1.58 = 0.315 ohms, 0.27 or .33 are peferred values.
This will reduce dissapation to 94.9 watts, about 30% less than previously.
Your feedback is appreciated!
ian
Well let's see if your temperature calibration nomenclature
matches mine:
Blimey hot is 10 seconds hands on = 45 deg C.
Crikey hot is 5 seconds = 50 deg C.
Bloody hot is 2 seconds = 55 deg C.
X*?@! is 60 deg C.
All of these are within an acceptable range, although
X*?@! is resrved for the more mature constructor.
matches mine:
Blimey hot is 10 seconds hands on = 45 deg C.
Crikey hot is 5 seconds = 50 deg C.
Bloody hot is 2 seconds = 55 deg C.
X*?@! is 60 deg C.
All of these are within an acceptable range, although
X*?@! is resrved for the more mature constructor.
Hmm,
Well if we have multiple choice then I recken it was option 3. (around 58 deg c according to the probe, and on the case of the IFR240 it was 79 deg c).
60 deg c is big burnies for any diy lad, not even the pussy cat will go near it (hot tin roof) Muhahahahahah
Worse than a hot iron or dripping solder on nylon socks!!
1. Blimey hot is 10 seconds hands on = 45 deg C.
2. Crikey hot is 5 seconds = 50 deg C.
3. Bloody hot is 2 seconds = 55 deg C. Correct
4. Flaming HotX*?@! is 60 deg C.
All of these are within an acceptable range, although
X*?@! is reserved for the more mature constructor.
Nobody said boo about my bias calcs?
Ian
This is to be avoided
Well if we have multiple choice then I recken it was option 3. (around 58 deg c according to the probe, and on the case of the IFR240 it was 79 deg c).
60 deg c is big burnies for any diy lad, not even the pussy cat will go near it (hot tin roof) Muhahahahahah
Worse than a hot iron or dripping solder on nylon socks!!
1. Blimey hot is 10 seconds hands on = 45 deg C.
2. Crikey hot is 5 seconds = 50 deg C.
3. Bloody hot is 2 seconds = 55 deg C. Correct
4. Flaming HotX*?@! is 60 deg C.
All of these are within an acceptable range, although
X*?@! is reserved for the more mature constructor.
Nobody said boo about my bias calcs?
Ian
This is to be avoided
