I remember,30 odd years ago, taking my Nak 730 to a local Mac amp clinic @ a boutique stereo shop for one of their clinics to demonstrate how good Mac amps were at THD, TIM, etc. all the distortion specs in vogue, 30 years ago....
After the pre-conditioning1/3 power warmup, my lowly receiver delivered something like 120 watts @ 8 ohms and 164 w/channel@ 4 ohms with vanishing distortion (if I recall, something like .0007% across 40khz, at any power level from 1st watt up to the rated (105w/channel@8ohms)
He wouldn't run full power sweep @4ohms, said he'd be afraid of blowing the amp up. Was the best set of numbers on any amp they ran (out of hundreds) all day, but he refused to post the results
I still use 2 of these receivers today, 35 years later...they'll pretty much drive anything I use with great sound
John L
After the pre-conditioning1/3 power warmup, my lowly receiver delivered something like 120 watts @ 8 ohms and 164 w/channel@ 4 ohms with vanishing distortion (if I recall, something like .0007% across 40khz, at any power level from 1st watt up to the rated (105w/channel@8ohms)
He wouldn't run full power sweep @4ohms, said he'd be afraid of blowing the amp up. Was the best set of numbers on any amp they ran (out of hundreds) all day, but he refused to post the results
I still use 2 of these receivers today, 35 years later...they'll pretty much drive anything I use with great sound
John L
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If I may, I would like to talk a little bit about the history of 'preconditioning' the power amp. In general, I think that it is too stringent a test, except for PA. It was put into the standard by a manufacturer who was in direct competition with Phase Linear about 40 years ago, and they used bigger heatsinks in their product, so they knew that they had an advantage. They used the inexperience of some of the other people in the standards group to put in this seemingly 'harmless' requirement. I heard this directly from the people who did it. Here are the equations:
Presumably you test between the conectors at one end of the cable, with the far end of the cable shorted? Capacitance testing would be similar, but with the far end open circuit.
Thanks. So standards aren't enforced? Maybe a problem for export, if compliance testing and certification is required?
But for the added weight, they also add a couple of advantages.
(which some may view as elegant)
Current MSRP here for a 500W MC501 monaural is €6500, a Parasound JC-1 does €6000 each.
In what many refer to as a fashion business, I'd reckon that 8.33 % difference in price is of less significance than brand appeal or blue power displays.
(Dithyrambic, lovely word)
Yes. The problem is in the level of inductance. Cables run the range from 200 nH per foot down to under 10nH per foot, depending on design. Many vendors do not auto-zero their instrument or realize it is needed, some will use Lp/Rp instead of Ls/Rs, some will try to measure 100 nH using 100hz or 120 hz test frequencies, and many do not rigidly control the setup to prevent variation of parasitic inductance.
Capacitance turns out to be significantly easier to get valid or near valid values close to reality.
jn
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Transformers
I'm glad to not have seen comments regarding how terrible having a transformer in the output stage of the Mac amp is. Many audiophiles love the sound of amps with transformers, namely those with vacuum-state devices.
I am a proponent of simple topologies, and if a transformer is not needed, then so be it, but a properly designed transformer can be transparent. indeed many of the vaunted recordings used as references have had their signals passed through one or more transformers at line-level.
The improvement in sound quality by eliminating multiple ground connections, common-mode RF and other garbage can be greater than any small loss due to the transformer itself. Then again, I am used to audio engineering in high electronic noise environments, such as factory floors and radio stations, so I may be biased in this opinion. Achieving >100dB s/n re: 4dBm in a factory environment distributing audio on unbalanced coax is a tough challenge!
My $0.02 worth.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
I'm glad to not have seen comments regarding how terrible having a transformer in the output stage of the Mac amp is. Many audiophiles love the sound of amps with transformers, namely those with vacuum-state devices.
I am a proponent of simple topologies, and if a transformer is not needed, then so be it, but a properly designed transformer can be transparent. indeed many of the vaunted recordings used as references have had their signals passed through one or more transformers at line-level.
The improvement in sound quality by eliminating multiple ground connections, common-mode RF and other garbage can be greater than any small loss due to the transformer itself. Then again, I am used to audio engineering in high electronic noise environments, such as factory floors and radio stations, so I may be biased in this opinion. Achieving >100dB s/n re: 4dBm in a factory environment distributing audio on unbalanced coax is a tough challenge!
My $0.02 worth.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
John,
Those Phase Linear and Spectra Sonics amplifiers at the time they were new to the market did sound better than most others you could use in PA applications. But I also remember trying to keep them cool on a hot summer day outside, they did have a habit to go up in smoke if they were pushed hard or impedance got to low.
JN,
Having had to troubleshoot 3-phase 480v would be considered working hot then I suppose! Had to do that more than once, usually a blown protection fuse on one leg.
Some may complain about the cost of a Mac amp but I don't think anyone can fault the build quality of there products, and they sure do look pretty if that is something that you care about. I sold some old Mac equipment that I inherited that had spent years at Disneyland producing the sound in some of the original rides. That was what was used there for years, very reliable and when I had them they still worked properly. I just wasn't into the tube sound or having to change those every so often. Someone paid some nice money to get their hands on them and they were not the chrome models, used 6BG6 output tubes I think.
Those Phase Linear and Spectra Sonics amplifiers at the time they were new to the market did sound better than most others you could use in PA applications. But I also remember trying to keep them cool on a hot summer day outside, they did have a habit to go up in smoke if they were pushed hard or impedance got to low.
JN,
Having had to troubleshoot 3-phase 480v would be considered working hot then I suppose! Had to do that more than once, usually a blown protection fuse on one leg.
Some may complain about the cost of a Mac amp but I don't think anyone can fault the build quality of there products, and they sure do look pretty if that is something that you care about. I sold some old Mac equipment that I inherited that had spent years at Disneyland producing the sound in some of the original rides. That was what was used there for years, very reliable and when I had them they still worked properly. I just wasn't into the tube sound or having to change those every so often. Someone paid some nice money to get their hands on them and they were not the chrome models, used 6BG6 output tubes I think.
I would consider it crazy..lectricity scares me.
for 480:
Limited approach is 3 foot 6 inches
Restricted approach is 1 foot
Prohibited approach is 1 inch.
To me, 16 feet is close enough..
jn
I would consider it crazy..lectricity scares me.
for 480:
Limited approach is 3 foot 6 inches
Restricted approach is 1 foot
Prohibited approach is 1 inch.
To me, 16 feet is close enough..
jn
You need to read the history of the guy who pioneered hands on 750KV.
Yes JN, No touchy the wires at that voltage. Worse experience was as a teen grabbing an old Sears Craftsman steel electric drill barefoot in the garage. Clamped my hand down real good, thought I was toast until I pulled the power line out of the wall with my other hand!
ps. That 480V was only 85kw so nothing to worry about!
ps. That 480V was only 85kw so nothing to worry about!
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The pilot is the one that's just nuts.
Who thinks up these things????
I can see it now....
You want me to do WHAT???
jn
Measurements 2.40 meters twisted pair:
86.2 pF = 10.95 pF/foot
3.8uH = 0.48 uH/foot
My LCR specs:
Test Frequency: 200µH to 2H rgs: 1000Hz;
20 and 200H ranges: 100Hz
Temperature Coefficient, ≤0.5H:
0.2%/°C; >0.5H: 0.5%/°C
Any suggestion how to use these measurements and LCR specs to calculate the resistor?
86.2 pF = 10.95 pF/foot
3.8uH = 0.48 uH/foot
My LCR specs:
Test Frequency: 200µH to 2H rgs: 1000Hz;
20 and 200H ranges: 100Hz
Temperature Coefficient, ≤0.5H:
0.2%/°C; >0.5H: 0.5%/°C
Any suggestion how to use these measurements and LCR specs to calculate the resistor?
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Creepage and clearance, ISO-60950 covers all the grim details and gives the spacing's required etc.
This link is better but I cant get it to work at the moment!
www.ce-mag.com/ce-mag.com/archive/01/03/ProductSafety.html
Should lead to a page called:
"calculating creepage and clearance early avoids..."
This is all part of CE marking in Europe and I believe UL in the USA.
www.ce-mag.com doesn't work by itself. There is something wrong with the link or the server right now.
> I don't think anyone can fault the build quality of there products
One time long ago I had occasion to dismantle a Mac amp.
Every thing at all visible was of high quality. (fibre-glass
boards, metal film resistors, et. al.) BUT ! When I got down
to the hidden internals it was bakelite with carbon comp etc.)
Gave us a good laugh
One time long ago I had occasion to dismantle a Mac amp.
Every thing at all visible was of high quality. (fibre-glass
boards, metal film resistors, et. al.) BUT ! When I got down
to the hidden internals it was bakelite with carbon comp etc.)
Gave us a good laugh
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