Greg Erskine said:
This is your opinion, Greg Erskine.
But in order to
'put quasi back to believe lineup gave a very good advice'
....
9/10 good web designers, who knows these things,
would think this:
That's right, Lineup!
... we shouldn't go away from good web standards recommendations
... just because we are lucky and it works today, at this server
... this is not wise thing to do!
We should, as far as possible, follow most general web standard for our stuff.
This makes for good 'portability' and your code would run everywhere
without a lot of headaches and extra work, to adjust.
---------------------------------------
Erskine, dear,
I have seen guys,
my friends, happy with Web Hosting one week
getting into problems with host
and desperately looking foor a New good Webhost,
the next, following week.
... where things would be better, but different
Script that worked before, will work no more: Only produce ERRORS.
Regards to Quasi ( ... but Mr Erskine maybe do some homework ; )
lineup
Web Master and Web Designer of this Web Standard web code:
http://lineup.awardspace.com/
lineup said:
Hi lineup,
No need. I already know. I've been doing this longer than you have. I've been there done that.
But I do advise you, if you are really worried about standards, to use this to get your code right.
http://validator.w3.org/
Qasi's website looks great and he should concentrate on designing amps rather than worring about a few spaces in filenames, IMHO.
I must be the 1/10 good web designers that know better.
regards
This amp looks like a great fit for one of my projects. Trouble is the power transformers I have available for it are 105 VCT, that puts the rail voltage a tad over the maximum of +/-70V (less than +/-75V though).
If it's the output device SOAR that maximum is based on, will using MJ21193's or 5's provide enough additional wriggle room to use this higher voltage? What about increasing the emitter resistors to drop a tad more? My heatsinks fit 4-pair of TO-3, so adding more parallel devices isn't going to work.
I don't really care that much about huge output power, I just want to recycle my spare parts. However, I do anticipate 4-ohm speakers being used.
..Todd
If it's the output device SOAR that maximum is based on, will using MJ21193's or 5's provide enough additional wriggle room to use this higher voltage? What about increasing the emitter resistors to drop a tad more? My heatsinks fit 4-pair of TO-3, so adding more parallel devices isn't going to work.
I don't really care that much about huge output power, I just want to recycle my spare parts. However, I do anticipate 4-ohm speakers being used.
..Todd
+/-75 V rails with a 4 ohm load is going to give you an amplifier with a power output of around 500W (If your power supply is up to the task).
That will make 3 pairs of MJ21193's into burnt smokey crispies pretty quickly with the volume control turned up.
Below is the reactive loadline for a reasonable 4 ohm speaker (2.83ohms+j2.83ohms).
The green line is the non-temperature derated 1sec SOAR for the MJ(L)21193(4). It doesn't come close to enclosing the load line.
I'd use 6 pairs minimum.
Cheers,
Glen
That will make 3 pairs of MJ21193's into burnt smokey crispies pretty quickly with the volume control turned up.
Below is the reactive loadline for a reasonable 4 ohm speaker (2.83ohms+j2.83ohms).
The green line is the non-temperature derated 1sec SOAR for the MJ(L)21193(4). It doesn't come close to enclosing the load line.
I'd use 6 pairs minimum.
Cheers,
Glen
Attachments
There is no doubt in the data presented by Glen, but it depends on the point of view. If the amp was run in test mode i.e. sinus input on the bench at full power for an extended period then the output stage is at risk.
But music is nothing like that, even at full power. Also consider that in an AB amplifier, the output transistors are turned off for almost half the time. So whilst the data is technically correct, it does not reflect real life applications (not by a mile).
Is this why every single commercial amp, even really good ones, that I've opened up would fail the theoretical SOAR test but somehow seem to live forever?
If in doubt use the full 4 output pairs.
Anyway Glen, I'm interested in the application you use. Where dya get it?
Also dug reading about the Landrover restoration.
Cheers
Q
But music is nothing like that, even at full power. Also consider that in an AB amplifier, the output transistors are turned off for almost half the time. So whilst the data is technically correct, it does not reflect real life applications (not by a mile).
Is this why every single commercial amp, even really good ones, that I've opened up would fail the theoretical SOAR test but somehow seem to live forever?
If in doubt use the full 4 output pairs.
Anyway Glen, I'm interested in the application you use. Where dya get it?
Also dug reading about the Landrover restoration.
Cheers
Q
quasi said:
G'day Quasi.
I have to disagree.
The graph shows that over just half a cycle at near maximum output, the 1 sec SOA of 3 parallel connected MJ21193's doesn't even come close to enclosing the reactive 4 ohm load line. And don't forget, the SOA curve shown is not temperature derated - it assumes a case temperature of 25 deg C.
In real life, with the transistor cases runing at perhaps 70 deg C or so, the conditions will be much worse.
It is unfortunate that the ON semi datasheets for the MJ21193 only show a 1 SEC SOA curve, but if you look at the SOA graphs for the similarly rated MJL3281A (Which has a virtually identical 1 Sec SOA) you'll see that the 1 second and 10ms SOA curves have have much less than one order of magnitude difference between them.
If you temperature derate and extrpolate from the graphs, you'll see that even the 10mS SOA will be violated.
Three MJ21193 pairs with +/-75V rails would be just passable for a domestic HiFi amp with 8 ohm loads, but hugely inadequate for 4 ohms, IMO.
What you say about the SOA design margins of commercial power amps is generally true for the cheaper end of the domestic amplifier market, but not so for proper professional or PA use.
I doubdt that there would be many professional amplifiers rated at ~500W in to 4 ohms with only three pairs of MJ21193/4 (or equilavent, power rating wise) transistors noted for their reliability.
I wrote the SOA calculator myself in Microsoft Visual Basic for computing my own high power designs. If you want a copy for a play, I can e-mail it to you.
Cheers,
Glen
Hi Glen,
In my post #8, I described this amp a powerful domestic power amp. Indeed if the amp was to be used as a musical instrument amplifier then the output stage needs to be heavier. It is true also for PA applications because compression is often used lifting the average power dissipation.
In terms of actual power delivered, in post #32 I gave an estimate of power using 70 volt rails. Along the theme of a domestic amplifier using a "reasonable" power supply, I estimated some losses in the power supply and in the amplifier finally arriving at a conservative 210 watts into 8 ohms. I guess near 400 watts into 4 ohms is achievable. I named this amp the N-Bip350 because in a "reasonable" stereo build this is reflects what would be achieved.
In another thread I presented a mos version of this amp. With a 500va transformer and DC rails of 73 volts I achieved 210 watts into 8 ohms and 360 watts into 4 ohms before clipping.
Having said the above I must fess up that when I looked at the SOAR of the MJ21193 and compared it to the MJ15003 I didn't notice that I was comparing a 1 sec SOAR to a DC SOAR. It may well be that the MJ15003 is actually stronger.
There is no way this amp could deliver 500 watts into 4 ohms with a reasonable power supply of say a 600 - 800va transformer. The amps that I've seen capable of delivering 500+ watts into 4 ohms run rails of around 80 volts (or more, idle).
I would be delighted if you could send me your SOAR applet. I currently do it in Excel. Please email to quasiweb@adam.com.au
I have written all the above for a wider audience and may have written the obvious for some readers. I trust I have not offended anyone in doing so.
Cheers
Q
In my post #8, I described this amp a powerful domestic power amp. Indeed if the amp was to be used as a musical instrument amplifier then the output stage needs to be heavier. It is true also for PA applications because compression is often used lifting the average power dissipation.
In terms of actual power delivered, in post #32 I gave an estimate of power using 70 volt rails. Along the theme of a domestic amplifier using a "reasonable" power supply, I estimated some losses in the power supply and in the amplifier finally arriving at a conservative 210 watts into 8 ohms. I guess near 400 watts into 4 ohms is achievable. I named this amp the N-Bip350 because in a "reasonable" stereo build this is reflects what would be achieved.
In another thread I presented a mos version of this amp. With a 500va transformer and DC rails of 73 volts I achieved 210 watts into 8 ohms and 360 watts into 4 ohms before clipping.
Having said the above I must fess up that when I looked at the SOAR of the MJ21193 and compared it to the MJ15003 I didn't notice that I was comparing a 1 sec SOAR to a DC SOAR. It may well be that the MJ15003 is actually stronger.
There is no way this amp could deliver 500 watts into 4 ohms with a reasonable power supply of say a 600 - 800va transformer. The amps that I've seen capable of delivering 500+ watts into 4 ohms run rails of around 80 volts (or more, idle).
I would be delighted if you could send me your SOAR applet. I currently do it in Excel. Please email to quasiweb@adam.com.au
I have written all the above for a wider audience and may have written the obvious for some readers. I trust I have not offended anyone in doing so.
Cheers
Q
quasi said:
Hi Quasi.
I don't think that you should have offended anyone either. I was just replying to Taj, who said that he has a 105VCT transformer, giving rail voltages of just under +/-75V and anticipates the use of 4 ohm speakers. He didn’t say what his transformers VA rating is though.
500W in 4ohm = 63V peak. That gives a ~10V sag/ripple/Vsat/etc headroom. 500W would just be rather close to the maximum RMS power output if his PSU is beefy enough.
Way back in 1997 SC did a 500W amp using a dual 55V secondary 800VA toroid (giving a nominal rail voltages of +/-80V. It used six pairs of MJL21193/4 transistors (plus a seventh pair for drivers) and about 80,000uF filter capacitance per rail. It managed a measured 500W rms and 590W for brief bursts.
The MJ15003 is a 20A transistor and it SOA at low voltages is superior to the M21193, but it is a lower voltage device and its secondary breakdown occurs earlier. The MJ21193 is better at high voltages.
I’ve had my SOA calculator on the net previously, so instead of E-mailing it, I’ve just uploaded it again.
The actually program *.EXE file is here:
http://users.picknowl.com.au/~glenk/CALC.EXE
To run it though, this *.DLL file needs to be put into the same directory/folder:
http://users.picknowl.com.au/~glenk/VBRUN300.DLL
Cheers,
Glen
Thanks for the responses, guys! That is a cool little application Glen.
The chassis and power supply for this project will come from an old decomissioned Bryston 4B, the power supply has dual EI transformers which are 400VA ea. The heatsinks are designed to hold 4 pairs of TO-3 transistors per channel.
So the circuit situation doesn't sound TOO different than what the original amplifier was designed to provide.
And I will NEVER be using this amp for PA. (I'm not in the music business anymore.) It's mainly for my own amusement and appreciation.
Quasi,
Just as a side note regarding compression: (And to qualify my next statements, I have mixed more than 2700 concerts (back when that Bryston 4B and myself were both considerably younger), then I worked in a mastering studio for a few years.)
The ONLY place compression is not used (as much) is in live classical recordings and "audiophile" jazz (like Chesky's products). Elsewhere, live and in the studio, in virtually all situations, considerable compression is omnipresent.
One difference between live and recording though, is that in recording, compression is typically applied to a greater degree on the overall mix, during the mastering phase, and [arguably] less often on the individual tracks. Though vocal tracks will typically always be compressed. Whereas, in my live concert experience, the mixes will focus the compression more on the individual inputs (to help control the level of the microphone lunacy on stage), then compress the main mix output very little, if any.
Having said that, many live audio crossovers and speaker management processors will provide limiting and sharp compression (greater than 5:1 ratio) to protect the drivers. And this protection is often invoked by the engineers to the point that its indicator LEDs are more on than off.
..Todd
The chassis and power supply for this project will come from an old decomissioned Bryston 4B, the power supply has dual EI transformers which are 400VA ea. The heatsinks are designed to hold 4 pairs of TO-3 transistors per channel.
So the circuit situation doesn't sound TOO different than what the original amplifier was designed to provide.
And I will NEVER be using this amp for PA. (I'm not in the music business anymore.) It's mainly for my own amusement and appreciation.
Quasi,
Just as a side note regarding compression: (And to qualify my next statements, I have mixed more than 2700 concerts (back when that Bryston 4B and myself were both considerably younger), then I worked in a mastering studio for a few years.)
The ONLY place compression is not used (as much) is in live classical recordings and "audiophile" jazz (like Chesky's products). Elsewhere, live and in the studio, in virtually all situations, considerable compression is omnipresent.
One difference between live and recording though, is that in recording, compression is typically applied to a greater degree on the overall mix, during the mastering phase, and [arguably] less often on the individual tracks. Though vocal tracks will typically always be compressed. Whereas, in my live concert experience, the mixes will focus the compression more on the individual inputs (to help control the level of the microphone lunacy on stage), then compress the main mix output very little, if any.
Having said that, many live audio crossovers and speaker management processors will provide limiting and sharp compression (greater than 5:1 ratio) to protect the drivers. And this protection is often invoked by the engineers to the point that its indicator LEDs are more on than off.
..Todd
Thanks Todd for that interesting information. Whilst I knew a fair bit of compression was used I didn't realise it was used as much as you've described. The only compression I've used is at the odd DJ show a friend and I used to do for fun. It wasn't because we were short of power, but more to keep the upper volume at a reasonable level.
You ex-Bryston setup sounds perfect for this amp. I imagine you could retain the look and feel of the Bryston as well.
Will you be using fly leads to the transistors?
Cheers
Q
You ex-Bryston setup sounds perfect for this amp. I imagine you could retain the look and feel of the Bryston as well.
Will you be using fly leads to the transistors?
Cheers
Q
Hi Quasi,
Your statement "more to keep the upper volume at a reasonable level" is the key. Nobody, I assume, *wants* to use compression. It's just a necessity of life, and studio compressors are always competing to provide the lowest notice-ability. The dynamics of a live stage show are just too much for your average ear, given the quiescent volume level. For example, if we're listening to music at a nominal 110dB (quite normal for an energetic rock/country/jazz concert), then we must keep the "microphone-lunacy-ratio" (my terminology) to a civilized 3:1 (~120 db), otherwise we have bleeding eardrums to clean up after. It gets messy; blood doesn't come out of concrete very easily. The topic is more sensitive in that respect (and difficult to deal with) than many people realize. ;-)
..Todd (ears still ringing, even after 17 years away from the console) Johnson
Your statement "more to keep the upper volume at a reasonable level" is the key. Nobody, I assume, *wants* to use compression. It's just a necessity of life, and studio compressors are always competing to provide the lowest notice-ability. The dynamics of a live stage show are just too much for your average ear, given the quiescent volume level. For example, if we're listening to music at a nominal 110dB (quite normal for an energetic rock/country/jazz concert), then we must keep the "microphone-lunacy-ratio" (my terminology) to a civilized 3:1 (~120 db), otherwise we have bleeding eardrums to clean up after. It gets messy; blood doesn't come out of concrete very easily. The topic is more sensitive in that respect (and difficult to deal with) than many people realize. ;-)
..Todd (ears still ringing, even after 17 years away from the console) Johnson
And I completely agree, by the way, the Bryston chassis is perfect for the NBIP. Hence the interest. Look and feel?? The look would be hard to change. And the feel will be freakin' heavy no matter how you brace yourself for the weight.
Fly leads? Do you mean wires from the PCB traces to the transistors? I suppose I will, though your PCB layout is conveniently close to the heatsink size/layout of the Bryston chassis, so the wires would be fairly short. 4" maximum (10cm) from the PCB to the TO-3 terminals. Do you think that presents a problem?
The only trouble I anticipate is getting T8 mounted onto the same physical plate as the output devices for thermo-coupling. But I relish that challenge.
..Todd
Fly leads? Do you mean wires from the PCB traces to the transistors? I suppose I will, though your PCB layout is conveniently close to the heatsink size/layout of the Bryston chassis, so the wires would be fairly short. 4" maximum (10cm) from the PCB to the TO-3 terminals. Do you think that presents a problem?
The only trouble I anticipate is getting T8 mounted onto the same physical plate as the output devices for thermo-coupling. But I relish that challenge.
..Todd
Trouble in paradise...
I spoke too soon. The Bryston chassis will not accommodate your PCB's length. I forgot the 4th pair heatsink is mounted around the corner, so there is only about 9 inches of usable length available (as seen in this illustration. )
So Quasi, I'd still like to retrofit this chassis with your circuit, but I'd need to draw up a new PCB that fits the form factor I have. Would you be willing to help with advice and instructions as required? The only thing I'm qualified to handle is the artwork.
..Todd
I spoke too soon. The Bryston chassis will not accommodate your PCB's length. I forgot the 4th pair heatsink is mounted around the corner, so there is only about 9 inches of usable length available (as seen in this illustration. )
So Quasi, I'd still like to retrofit this chassis with your circuit, but I'd need to draw up a new PCB that fits the form factor I have. Would you be willing to help with advice and instructions as required? The only thing I'm qualified to handle is the artwork.
..Todd
Todd,
Thanks for the interesting compression information, fascinating.
I have met Quasi (aka Con!!) - a truly lovely fellow, and his amp is, in my view, incredibly robust and at this point very refined.
Considering it's freeware, I think all the Quasi builders are very lucky - I'm not so generous!
Cheers,
Hugh
Thanks for the interesting compression information, fascinating.
I have met Quasi (aka Con!!) - a truly lovely fellow, and his amp is, in my view, incredibly robust and at this point very refined.
Considering it's freeware, I think all the Quasi builders are very lucky - I'm not so generous!
Cheers,
Hugh
Re: Trouble in paradise...
Hi Todd, the length (funny, I always thought of it as the width) of the PCB is determined mainly by the 8 x TO3 transistors and the DC detect section. So there is good scope for the board to be made smaller as you would only need enough room for the wiring points. The DC protect could be on a seperate PCB. I posted one here http://www.diyaudio.com/forums/showthread.php?postid=972400#post972400. When designing the PCB take note of the ground tracks. There are two seperate grounds on the board seperated by a 10 ohm resistor. Also as much as possible all ground returns should be via exclusive tracks back to the central ground points.
Freeware ?? So why does this DIY cost me so much money?
Cheers
Q
taj said:
Hi Todd, the length (funny, I always thought of it as the width) of the PCB is determined mainly by the 8 x TO3 transistors and the DC detect section. So there is good scope for the board to be made smaller as you would only need enough room for the wiring points. The DC protect could be on a seperate PCB. I posted one here http://www.diyaudio.com/forums/showthread.php?postid=972400#post972400. When designing the PCB take note of the ground tracks. There are two seperate grounds on the board seperated by a 10 ohm resistor. Also as much as possible all ground returns should be via exclusive tracks back to the central ground points.
AKSA said:
Freeware ?? So why does this DIY cost me so much money?
Cheers
Q
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