Terry Demol said:
I, and plenty of others, can design an amp that gets around 0.001%
or less THD at close to full power right up to 20kHz.
But there's not much point in buying or building an amp that you
don't want to listen to.
Cheers,
Terry
Don't mix this together, Terry. The very low THD does not automatically mean it is an amp you do not want to listen to. As you know there are another factors of influence.
My question would be different: make 2 amps, both very pleasant to listen to. 1st with THD of 0.00X%, flat with power, flat with frequency. 2nd with THD of 0.X% or X%, rising with power and rising with frequency. Listen to well recorded (Bishop, Renner) Beethoven, Mahler, and tell me, which of the amps sounded better.
Cheers,
Pavel
Hi Suzy
I have had heaps of experience with Laterals Fets and while they
do have problems with parisitic oscillation, they can be fixed so
they are unconditional stable, even into 2 Ohm loads.
I have designed and built amplifiers that develop as much as 1400 watts into 2 Ohm loads and they are 100% stable.
i am also very familiar with the AEM 6000 amp.
So if you require any help with it let me know.
You may find that you will have to increase the gate resistors on the N-channel fets with respect to the P-channel.
I built one of the AEM 6000 amps when they first can out.
A very nice design and sounded OK as well.
Anyway if you need help with just let me know.
I have had heaps of experience with Laterals Fets and while they
do have problems with parisitic oscillation, they can be fixed so
they are unconditional stable, even into 2 Ohm loads.
I have designed and built amplifiers that develop as much as 1400 watts into 2 Ohm loads and they are 100% stable.
i am also very familiar with the AEM 6000 amp.
So if you require any help with it let me know.
You may find that you will have to increase the gate resistors on the N-channel fets with respect to the P-channel.
I built one of the AEM 6000 amps when they first can out.
A very nice design and sounded OK as well.
Anyway if you need help with just let me know.
PMA wrote:
Aside from the narrow range of audition music, why would anyone want to build a couple of amps and then report the results to you? You have made it amply clear what you think, surely the aim is to prove something to the majority?
And is the ear the final arbiter? Or the measurements? Which is it to be?
Hugh
Aside from the narrow range of audition music, why would anyone want to build a couple of amps and then report the results to you? You have made it amply clear what you think, surely the aim is to prove something to the majority?
And is the ear the final arbiter? Or the measurements? Which is it to be?
Hugh
Terry
Design and show me, please.
Because there are different ways to achieve such a goal, none these ways is easy, some better and some worse to other factors.
Design and show me, please.
Because there are different ways to achieve such a goal, none these ways is easy, some better and some worse to other factors.
Keep cool, Hugh (and decent as usually).
Terry has suggested a kind of comparison of 2 amps, I do suggest another one. What I wrote works for any kind of music, the classical is the fastest to judge by ears.
Terry has suggested a kind of comparison of 2 amps, I do suggest another one. What I wrote works for any kind of music, the classical is the fastest to judge by ears.
I'm cool as a cucumber....... age and treachery wins out against youth and enthusiasm every time......
This eternal, seemingly insoluble debate goes to the crux of how the marketers shape and exploit the market.
Now, which has it? The ears, or the meters?
Hugh
This eternal, seemingly insoluble debate goes to the crux of how the marketers shape and exploit the market.
Now, which has it? The ears, or the meters?
Hugh
Now, which has it? The ears, or the meters?
hmm... the ears all disagree 'cos , well they're all basically different , and ( as we all know ) numbers can be made to say anything 😎
For me at least it comes down to what I would choose to listen to.
I reckon that anyone old enough and wise enough to actually know what they are listening for, is too old to actually have the auditory range to actually *hear* it.... especially true for men, whose hearing drops off quicker than women.
When I need a second opinion about audio I always ask my wife what she hears , partly because she has better hearing , and partly because she used to work as a professional sound engineer....
Ray
hmm... the ears all disagree 'cos , well they're all basically different , and ( as we all know ) numbers can be made to say anything 😎
For me at least it comes down to what I would choose to listen to.
I reckon that anyone old enough and wise enough to actually know what they are listening for, is too old to actually have the auditory range to actually *hear* it.... especially true for men, whose hearing drops off quicker than women.
When I need a second opinion about audio I always ask my wife what she hears , partly because she has better hearing , and partly because she used to work as a professional sound engineer....
Ray
Try a value of 680E for the N-channel and 470E for the P-channel FETs. This combination also sounds the best sonically in my experience.
Hai Mr.Holton, great to see you active here again. Been looking at your new offerings of all-mosfet amps. Fantastic job as usual.
Ringing ears
What a hoot!
I've powered my monoblocks up, and am incredibly happy with them. A few lessons though:
10 Ohm 1/2 Watt resistors are no good charging the on-board electrolytics 🙂
The Vgs threshold on my MOSFETS is a little higher than the data would indicate - I had to remove the 220 Ohm resistor across the bias trimpot to get a full 100mA quiescent current.
It's a tad tempramental, and prone to taking off at 1.1MHz. I have no idea how people build these things without a good CRO. Increasing the compensation caps on the drivers from 12p to 22p helped, but hasn't cured it completely - with a speaker connected, it occasionally oscillates when I power-cycle it. For now I've just decreased the global feedback (increased the gain from 17dB to 23dB), which has cured it, but there's clearly still some work to be done optimising the compensation networks. I'd ideally like to be able to run it with more global feedback.
I'm leery of just increasing the gate resistors. That'll stop oscillations, sure, but it does nothing for slew rate.
Having hooked one up to a speaker, and played some of my favourite music (Bernard Fanning, Mike Oldfield, Suzanne Vega, James) through it, I've gotta say, I'm well impressed. It's amazingly transparent and clear. I find the limits of the speaker (not to mention the limits of my husband's patience) a long time before it starts to clip.
I've got a bit of work to do now to work out how to measure its THD and IMD performance. All the gear I have access to at work is for HF/microwave use, and has pretty poor performance at audio. I've had a fairly feeble attempt at measuring the distortion with my notebooks on-board sound card, but have just found that my notebook's sound is shocking. A loopback gives me 0.02%.
If anyone has any recommendations for a good (or at least hackable) USB sound card I'd be very grateful.
I'm _so_ happy.
Cheers,
Suzy
What a hoot!
I've powered my monoblocks up, and am incredibly happy with them. A few lessons though:
10 Ohm 1/2 Watt resistors are no good charging the on-board electrolytics 🙂
The Vgs threshold on my MOSFETS is a little higher than the data would indicate - I had to remove the 220 Ohm resistor across the bias trimpot to get a full 100mA quiescent current.
It's a tad tempramental, and prone to taking off at 1.1MHz. I have no idea how people build these things without a good CRO. Increasing the compensation caps on the drivers from 12p to 22p helped, but hasn't cured it completely - with a speaker connected, it occasionally oscillates when I power-cycle it. For now I've just decreased the global feedback (increased the gain from 17dB to 23dB), which has cured it, but there's clearly still some work to be done optimising the compensation networks. I'd ideally like to be able to run it with more global feedback.
I'm leery of just increasing the gate resistors. That'll stop oscillations, sure, but it does nothing for slew rate.
Having hooked one up to a speaker, and played some of my favourite music (Bernard Fanning, Mike Oldfield, Suzanne Vega, James) through it, I've gotta say, I'm well impressed. It's amazingly transparent and clear. I find the limits of the speaker (not to mention the limits of my husband's patience) a long time before it starts to clip.
I've got a bit of work to do now to work out how to measure its THD and IMD performance. All the gear I have access to at work is for HF/microwave use, and has pretty poor performance at audio. I've had a fairly feeble attempt at measuring the distortion with my notebooks on-board sound card, but have just found that my notebook's sound is shocking. A loopback gives me 0.02%.
If anyone has any recommendations for a good (or at least hackable) USB sound card I'd be very grateful.
I'm _so_ happy.
Cheers,
Suzy
Hi Suzy
Great to hear you amp is working... 🙂
IMHO I have found that it is important to balance the speed
difference between the N-chn and P-chn fets. this is best achieved I believe by increasing the N-channel get resistor value
with respect to the P-channel. You see the P-chn fet is quite a bit slower that the N-channel fet, so the n-channel fet will need to be slowed down to the same speed of the P-channel.
This I have found will rid of the oscillation and helps to get rid of cross conduction issues.
My NX150 and NX400 Amplifiers do not cross conduct even at 200khz and have no oscillation issues at all.
also when testing the amplifiers into a dummy load try loading
the amp with a 2uf MKP in parallel with an 8 Ohm load this will show up any instablity issues if any. 2 Ohms load have habit of doing this as well.
Anyway good luck with you amp. Very impressed with your eye for detail.
Great to hear you amp is working... 🙂
IMHO I have found that it is important to balance the speed
difference between the N-chn and P-chn fets. this is best achieved I believe by increasing the N-channel get resistor value
with respect to the P-channel. You see the P-chn fet is quite a bit slower that the N-channel fet, so the n-channel fet will need to be slowed down to the same speed of the P-channel.
This I have found will rid of the oscillation and helps to get rid of cross conduction issues.
My NX150 and NX400 Amplifiers do not cross conduct even at 200khz and have no oscillation issues at all.
also when testing the amplifiers into a dummy load try loading
the amp with a 2uf MKP in parallel with an 8 Ohm load this will show up any instablity issues if any. 2 Ohms load have habit of doing this as well.
Anyway good luck with you amp. Very impressed with your eye for detail.
Suzyj, try out my recommendation of gate resistors values. I am sure they will help almost eliminate oscillation issues and improve sonics as well. These were Randy Slones favoured values when using 2SK1058 and 2SJ162 mosfets. I have used them and have been mighty pleased. However, if you are using the 2SK133,134,135 and 2SJ74,75,76 types values may differ.
this amp has been built to high levels of sophistication
just think this-if it all turns out bad sounding what a
contrast of objectivist misinformation
i am just waiting to see this rf-audio-amp really come
to completion including casing etc the designer is keen
to push the limits of performance with some rf know
how lets see
suzyj no1
cheers
john
just think this-if it all turns out bad sounding what a
contrast of objectivist misinformation
i am just waiting to see this rf-audio-amp really come
to completion including casing etc the designer is keen
to push the limits of performance with some rf know
how lets see
suzyj no1
cheers
john
The Saint said:
Samuel Jayaraj said:
Thanks guys.
I thought at first that increasing the gate resistors would destroy the intermod performance, but on simulation I find that there's only a very modest increase in intermods (by a dB or two).
However the improvement in stability is remarkable.
I'm now running with 470 and 680 Ohm gate resistors, 2 x 15pF miller caps on each of the driver transisrors, and x16 gain, and my monoblocks are as solid as a rock.
I've done all sorts of horrid things to them - driving them hard into clipping at 20KHz, putting a 2u2 cap across my dummy load, you name it. They just work.
Awesome. Now that I'm satisfied that they won't take off, I can hook them up to my good speakers and do some listening tests.
Again, thanks heaps for your help.
Cheers,
Suzy
eti 5000
Hi Suzyj,
Congratulations!!! Now you can built two or four more units plus active crossovers and go active all the way. It is the most significant improvement heard by all who can still hear something.
Maybe you could post a final cuircuit diagram of your achievement?
One additional note: I keep my power supply for my active system in a separate box. No hum problems in my amps whatsoever. Costs many times less than your board expenditure.
cheers,
Hi Suzyj,
Congratulations!!! Now you can built two or four more units plus active crossovers and go active all the way. It is the most significant improvement heard by all who can still hear something.
Maybe you could post a final cuircuit diagram of your achievement?
One additional note: I keep my power supply for my active system in a separate box. No hum problems in my amps whatsoever. Costs many times less than your board expenditure.
cheers,
Hi Janusz,
It's certainly tempting. I've got another couple of PCBs, sitting on my bench, looking awefully lonely...
What's the usual deal with active crossover systems? I imagine the woofer needs most of the power, so do you use a thumping big amplifier for the woofers, and smaller ones for mid and tweeters, or just use lots of big ones?
It adds some interesting flexibility, come to think of it. If there's no need to be able to drive large powers at high frequency, one could optimise the amplifier for the tweeters for slew rate, and end up with much better system performance.
So do you put the amps with the speakers, or with the sources?
On another note, I think I've found a reasonable sound card. It's the M-Audio Audiophile USB. Looks like it has reasonably good distortion specs, at any rate. I've been working on my hubby to convince him that I really need one. "But darling, I can use it in the HTPC that I want to make..."
Cheers,
Suzy (married to a saint)
It's certainly tempting. I've got another couple of PCBs, sitting on my bench, looking awefully lonely...
What's the usual deal with active crossover systems? I imagine the woofer needs most of the power, so do you use a thumping big amplifier for the woofers, and smaller ones for mid and tweeters, or just use lots of big ones?
It adds some interesting flexibility, come to think of it. If there's no need to be able to drive large powers at high frequency, one could optimise the amplifier for the tweeters for slew rate, and end up with much better system performance.
So do you put the amps with the speakers, or with the sources?
On another note, I think I've found a reasonable sound card. It's the M-Audio Audiophile USB. Looks like it has reasonably good distortion specs, at any rate. I've been working on my hubby to convince him that I really need one. "But darling, I can use it in the HTPC that I want to make..."
Cheers,
Suzy (married to a saint)
-------------------------------------------------------------------------------
susyj:
I'm now running with 470 and 680 Ohm gate resistors, 2 x 15pF miller caps on each of the driver transisrors, and x16 gain, and my monoblocks are as solid as a rock.
------------------------------------------------------------------------------
i'd suggest you increase the miller caps to at least 100pf!on the other hand leave em and take the risk
john - class-a guru
susyj:
I'm now running with 470 and 680 Ohm gate resistors, 2 x 15pF miller caps on each of the driver transisrors, and x16 gain, and my monoblocks are as solid as a rock.
------------------------------------------------------------------------------
i'd suggest you increase the miller caps to at least 100pf!on the other hand leave em and take the risk
john - class-a guru
suzyj said:
Miss Jackson,
You could ask Janneman how he likes it, he uses it.
(thinking of getting one myself too)
Traditional power distribution for a 3-way is: 2-1-1
So say 100 watts for the woofer, and 50 for mid and high.
Going to post some pictures of the finished work ?
J(Just another devil)
active eti 5000
Hi Suzyj,
Jacco already replied on power requirements for a three way system. If I remember correctly, on the average, there is only about 15% of sonic energy above 3kHz but it is good to have ample headroom in all amps.
My power amps are in boxes and speakers are connected by thick speaker cables. You may attach power amps to speaker boxes if you wish. Each solution has advantages and disadvantages. I prefer boxed amps close to their preamp and active crossover. Connecting small signal cables are short and amps are not exposed to direct speaker vibrations.
The current system I'm stll building has active 600Hz crossover (4th order Bessel, low pass is all pass minus high pass) but midrange and tweeter are crossed passively (simple first order crossover). All four amps are identical - about 150W RMS into 8 ohms. As my woofers are 6ohm (2x12ohm parallel), while midrange and tweeter are 8 ohms each, my woofers see a 200W amp.
The system will have separate active servo subwoofers crossed at about 120Hz. There will be two subwoofers. These are my intentions. Maybe they will come true. I also intended to keep my old car for the next 2-3 years but three weeks ago it was terminated on an intersection by a student from India. Luckily, no one was hurt.
cheers,
Hi Suzyj,
Jacco already replied on power requirements for a three way system. If I remember correctly, on the average, there is only about 15% of sonic energy above 3kHz but it is good to have ample headroom in all amps.
My power amps are in boxes and speakers are connected by thick speaker cables. You may attach power amps to speaker boxes if you wish. Each solution has advantages and disadvantages. I prefer boxed amps close to their preamp and active crossover. Connecting small signal cables are short and amps are not exposed to direct speaker vibrations.
The current system I'm stll building has active 600Hz crossover (4th order Bessel, low pass is all pass minus high pass) but midrange and tweeter are crossed passively (simple first order crossover). All four amps are identical - about 150W RMS into 8 ohms. As my woofers are 6ohm (2x12ohm parallel), while midrange and tweeter are 8 ohms each, my woofers see a 200W amp.
The system will have separate active servo subwoofers crossed at about 120Hz. There will be two subwoofers. These are my intentions. Maybe they will come true. I also intended to keep my old car for the next 2-3 years but three weeks ago it was terminated on an intersection by a student from India. Luckily, no one was hurt.
cheers,
Hi Suzy,
I'm sure you'll be very happy with the M-Audio card. I've got a Soundblaster Audigy NX USB card that is also very good and has been an extemely useful tool for me. I use it for just about all of my audio measurements.
Soundblaster products have a mixed reputation, but this particular card is pretty good. I've measued residual THD+N at -90dB (0.003%). By looking at the individual harmonics I can resolve distortion products down to about -94dB, which is usually enough for me.
The M-Audio card will probably do even better.
With regard to active crossovers; I'm a big fan! Rather than repeat the advantages here, I suggest you have a look at Rod Elliot's site. He's got an excellent article on active crossovers and loads of other great information. A clever guy who really tells it like it is. And he's a local!
http://sound.westhost.com/biamp-vs-passive.htm
Cheers, Ralph
I'm sure you'll be very happy with the M-Audio card. I've got a Soundblaster Audigy NX USB card that is also very good and has been an extemely useful tool for me. I use it for just about all of my audio measurements.
Soundblaster products have a mixed reputation, but this particular card is pretty good. I've measued residual THD+N at -90dB (0.003%). By looking at the individual harmonics I can resolve distortion products down to about -94dB, which is usually enough for me.
The M-Audio card will probably do even better.
With regard to active crossovers; I'm a big fan! Rather than repeat the advantages here, I suggest you have a look at Rod Elliot's site. He's got an excellent article on active crossovers and loads of other great information. A clever guy who really tells it like it is. And he's a local!
http://sound.westhost.com/biamp-vs-passive.htm
Cheers, Ralph
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