Hi William,
Yeah, I think it is a gain issue. A good listening level for my Krell is about 8:00 on the pre. For the A-X it is about 10:00. That made me think the A-X was underpowered. However, I could get it plenty loud before distortion by just raising the gain on the Pre.
Adjustilon the offset with the lid on is not an option. I can make adjustments and then replace the lid and watch though. I try that when I have a lot of time.
I played this amp through my nearfield speakers last night. They are 4 ohm and it really sounded nice. Probably sound even better once I get the right input caps installed. The board that I use in my studio for the nearfields is ballanced so I'm looking forward to seeing how that works out as well.
Blessings, Terry
Yeah, I think it is a gain issue. A good listening level for my Krell is about 8:00 on the pre. For the A-X it is about 10:00. That made me think the A-X was underpowered. However, I could get it plenty loud before distortion by just raising the gain on the Pre.
Adjustilon the offset with the lid on is not an option. I can make adjustments and then replace the lid and watch though. I try that when I have a lot of time.
I played this amp through my nearfield speakers last night. They are 4 ohm and it really sounded nice. Probably sound even better once I get the right input caps installed. The board that I use in my studio for the nearfields is ballanced so I'm looking forward to seeing how that works out as well.
Blessings, Terry
Hi Guys,
OK, I've been listening to the A-X all morning. I seem to detect a slight fizzle sound like I'm getting some distortion. I have just purchased a Tektronix 475 scope but don't have a clue how to hook it up. I would like to try that and maybe post some pics of the screen so you guys can maybe help me get to the bottom of this.
Can one or more of you give me some step by step to get my scope hooke up? It came with P6106 probes.
Thanks, Terry
OK, I've been listening to the A-X all morning. I seem to detect a slight fizzle sound like I'm getting some distortion. I have just purchased a Tektronix 475 scope but don't have a clue how to hook it up. I would like to try that and maybe post some pics of the screen so you guys can maybe help me get to the bottom of this.
Can one or more of you give me some step by step to get my scope hooke up? It came with P6106 probes.
Thanks, Terry
The probe is easy: attach the ground clip to an _actual_ ground point somewhere in your amp, near to where you want to measure. Be careful to _not_ attach the ground clip to any non-ground point in your circuit. Aside from that, just be careful to not short anything out with the probe tip.
If you're working with audio signals, it's easiest to trigger the scope from the AC line. This is labelled LINE on the trigger selection on Tektronix scopes.
I'd start by looking at the output, just to get a feel for what's happening. Then you'll want to look at the outputs of the differential, and the current source drive. Of course, you should start by measuring the DC parameters first, to get an idea of what the quiescent point is.
If you're working with audio signals, it's easiest to trigger the scope from the AC line. This is labelled LINE on the trigger selection on Tektronix scopes.
I'd start by looking at the output, just to get a feel for what's happening. Then you'll want to look at the outputs of the differential, and the current source drive. Of course, you should start by measuring the DC parameters first, to get an idea of what the quiescent point is.
You'll have better results using a differential input to the scope. Otherwise, the scope will only read half the output signal, since the probe is referenced to ground and not to the other side of the amp.
The implication here is that you will also see distortion and noise that would otherwise be cancelled by the "X" action of the circuit.
Grey
The implication here is that you will also see distortion and noise that would otherwise be cancelled by the "X" action of the circuit.
Grey
BobEllis said:
I was going to ask how inportant the 10uf was. I have a few 1uf metal film caps and quite a few .1uf. (100nf same?) I'll order some 10uf pp caps if it will make that much of a difference.
Did I forget to mention I don't know anything about using a scope?
I've finally figured out how to get the line to jump around when music is played through it but don't have a clue what to look for. When you say measure the DC parameters, how would I hook that up and what would I look for. Maybe I should wait until I can meet someone who can walk me through all of this so I don't take up folks precious time here.
Do you gys know of any stufff on line that can help someone who needs to learn this, like a scopes for dummies of something?
I though of that when it said to hook up to ground, that it was going to be seeing absolute offset and not really telling the whole story.
Thanks, Terry
use a couple of those 1 uf film caps in parallel if you have enough - that ought to give you a low enough corner frequency to be useful.
yes, 100 nf = 0.1 uf
you'll be better off using a sine wave to try to find distortion. reduce the time interval until you have a wave or two and look for discontinuities.
Is it a dual trace scope? try one probe on each output terminal, select A-B to view the output waveform.
yes, 100 nf = 0.1 uf
you'll be better off using a sine wave to try to find distortion. reduce the time interval until you have a wave or two and look for discontinuities.
Is it a dual trace scope? try one probe on each output terminal, select A-B to view the output waveform.
I could use some pointers on this one.
Hi guys,
As a fourth amp project I would like to build an Aleph-X. I am pretty cheap so I would like to use what I have on hand. The amp I would like to construct would be the largest,heaviest, and highest power AX I can muster. Before you go on about heat, consumption, and etc I want to say that I really want to build this thing. Here is what I have on hand....
- a few hundred IRFP140
- a lot of capacitance
- too much heatsink
- a pair of Kari and a pair of rev. 1 boards (help me choose)
- an old >3kva transformer +-21.5v or +-23v or +-39v
(help me choose)
- a bunch of 1r and .47r power resistors (help me choose)
- plenty of wire
of all colors.
- little time
OK, this is going to be a large 2 channel amp (1 chassis) with p2p wiring on the output/ccs section. I need to settle on a rail voltage, source resistor value, and best boards for the app. I have been thru the axe1 spreadsheet but there is no replacement for a little experience. I want to use the 23 v secs with maybe 20 or probably more fets per channel. I wanna do this..any advice?
Thanks in advance,
Marc
Hi guys,
As a fourth amp project I would like to build an Aleph-X. I am pretty cheap so I would like to use what I have on hand. The amp I would like to construct would be the largest,heaviest, and highest power AX I can muster. Before you go on about heat, consumption, and etc I want to say that I really want to build this thing. Here is what I have on hand....
- a few hundred IRFP140
- a lot of capacitance
- too much heatsink
- a pair of Kari and a pair of rev. 1 boards (help me choose)
- an old >3kva transformer +-21.5v or +-23v or +-39v
(help me choose)- a bunch of 1r and .47r power resistors (help me choose)
- plenty of wire
of all colors.- little time
OK, this is going to be a large 2 channel amp (1 chassis) with p2p wiring on the output/ccs section. I need to settle on a rail voltage, source resistor value, and best boards for the app. I have been thru the axe1 spreadsheet but there is no replacement for a little experience. I want to use the 23 v secs with maybe 20 or probably more fets per channel. I wanna do this..any advice?
Thanks in advance,
Marc
Re: I could use some pointers on this one.
Hi,
if you want something big 23V would be nice and good for 28-30V supply voltage. 39 is a bit too much and 21.5 an odd number.....
I would use the 0.47R resistors. They are big enough to help matching the fets and don´t waste as much voltage (and power) as 1R would do.
If you know what speakers you want to drive you could set the bias for maximum power at their lowest impedance. Then calculate the dissipation for one channel and set the number of fets for dissipation below 25watts. After that you can see if your heatsinks are big enough.......
William
mpmarino said:
Hi,
if you want something big 23V would be nice and good for 28-30V supply voltage. 39 is a bit too much and 21.5 an odd number.....
I would use the 0.47R resistors. They are big enough to help matching the fets and don´t waste as much voltage (and power) as 1R would do.
If you know what speakers you want to drive you could set the bias for maximum power at their lowest impedance. Then calculate the dissipation for one channel and set the number of fets for dissipation below 25watts. After that you can see if your heatsinks are big enough.......
William
Could I use these?
Dear All,
I have come by two unused amplifier transformers: EI style, 2 * 55V AC, centre-tapped rather than independent secondaries, 500 plus VA (I presume that is total secondary wattage). They are from a New Zealand audio company called Perreaux, who make some nice stuff, I am told. I have yet to actually run them up and test them myself with and without a load, but they look intact and the DC resistances in each of the windings agree on cross-checking.
1. Is the voltage of these too high to use on an Aleph-X design? It looks as though it would be.
2. Is there a way of providing amplifiers (class AB or class A) with a "Pseudo-ground" so that I could use each winding separately and effectively halve the voltage? (I have seen something on Rod Elliott's site, but this appears to be for low current applications.)
I am building some Linkwitz orions with LM3886 amps for each driver, but thought that for "fun" I could try some class A amplification on the midrange and tweeter and a Nelson Pass design would be the way to go: simple design, lots of space, and understandable (in an elementary - as a relative newbie).
The next option I considered was to build two Aleph 60/Aleph 5 which have about the right voltage requirement, and it is probably the way to go. The only thing that "worries" me is that 60W per tweeter seems a bit "over the top" and perhaps not as "sweet" as as a 30W design (Aleph 30/Aleph 3). (The Aleph 5 is about 60 Watts, isn't it ... I am writing this from work, so I might have that wrong.)
3. Any comments on this, or am I worrying too much?
Or something Zen-like ...
Or, I guess, I could just make a pair of subwoofers, much to my wife's disgust.
With thanks for your thoughts,
George
Dear All,
I have come by two unused amplifier transformers: EI style, 2 * 55V AC, centre-tapped rather than independent secondaries, 500 plus VA (I presume that is total secondary wattage). They are from a New Zealand audio company called Perreaux, who make some nice stuff, I am told. I have yet to actually run them up and test them myself with and without a load, but they look intact and the DC resistances in each of the windings agree on cross-checking.
1. Is the voltage of these too high to use on an Aleph-X design? It looks as though it would be.
2. Is there a way of providing amplifiers (class AB or class A) with a "Pseudo-ground" so that I could use each winding separately and effectively halve the voltage? (I have seen something on Rod Elliott's site, but this appears to be for low current applications.)
I am building some Linkwitz orions with LM3886 amps for each driver, but thought that for "fun" I could try some class A amplification on the midrange and tweeter and a Nelson Pass design would be the way to go: simple design, lots of space, and understandable (in an elementary - as a relative newbie).
The next option I considered was to build two Aleph 60/Aleph 5 which have about the right voltage requirement, and it is probably the way to go. The only thing that "worries" me is that 60W per tweeter seems a bit "over the top" and perhaps not as "sweet" as as a 30W design (Aleph 30/Aleph 3). (The Aleph 5 is about 60 Watts, isn't it ... I am writing this from work, so I might have that wrong.)
3. Any comments on this, or am I worrying too much?
Or something Zen-like ...
Or, I guess, I could just make a pair of subwoofers, much to my wife's disgust.
With thanks for your thoughts,
George
I got a bit of a surprize today when I got home. My wife had sent my son out to my studio to shut things off last night and he shut down everything but the A-X. Well, the room was toasty warm when I got home from work this evening. The amp sounds fine but man the transformer was very hot to the touch. I think I had better bite the bullet and change out the source resistors to 0R22. This thing is just running too hot. The heatsinks were up to 62c. 
I'll pull it apart next chance I get and report back as to how the sound was affected.
Blessings, Terry
I'll pull it apart next chance I get and report back as to how the sound was affected.
Blessings, Terry
re: post 930
Thanks William,
My research has proven worthwhile as that is the setup I would have chosen if alone. It's nice to get some affirmation.
What boards should I use? There is a lot of known experience on the hifizen boards and plenty of support. But it seems like the Kari boards would be better suited as they don't waste complication on outputs. They look real nice too. Also, I seem to remember some errata on the Kari boards...is it true? (I must be lazy, I could just trace it out myself!)
also, would it be of benefit to go lower than .47r on the source resistors? I could parallel them if need be.....
regards...
Thanks William,
My research has proven worthwhile as that is the setup I would have chosen if alone. It's nice to get some affirmation.
What boards should I use? There is a lot of known experience on the hifizen boards and plenty of support. But it seems like the Kari boards would be better suited as they don't waste complication on outputs. They look real nice too. Also, I seem to remember some errata on the Kari boards...is it true? (I must be lazy, I could just trace it out myself!)
also, would it be of benefit to go lower than .47r on the source resistors? I could parallel them if need be.....
regards...
Banned
Joined 2002
still4given said:I got a bit of a surprize today when I got home. My wife had sent my son out to my studio to shut things off last night and he shut down everything but the A-X. Well, the room was toasty warm when I got home from work this evening. The amp sounds fine but man the transformer was very hot to the touch. I think I had better bite the bullet and change out the source resistors to 0R22. This thing is just running too hot. The heatsinks were up to 62c.
I'll pull it apart next chance I get and report back as to how the sound was affected.
Blessings, Terry
Be carefull with that transformer if it over heats it could cause a dead short or the full ac line into your amplifier.. Maybe get a transformer over rated for this
. J'
Terry,
Not to scare you, but if your transformer gets that hot and your sinks get that hot your going to have to bias the amp down before you have a fire. This is no joke. If your transformer gets that hot eventually it will fail and cause all sorts of fireworks. I certainly would not leave it unattended if its running that hot. Larger sinks and a larger toroidal may not be a bad investment.
Not to scare you, but if your transformer gets that hot and your sinks get that hot your going to have to bias the amp down before you have a fire. This is no joke. If your transformer gets that hot eventually it will fail and cause all sorts of fireworks. I certainly would not leave it unattended if its running that hot. Larger sinks and a larger toroidal may not be a bad investment.