Maybe you have a point, I haven't heard it and it might have a little nice phase response or some other twist that other Pultec clones don't have. But, even if something like that is the case, I still have a point that it could not account for making "everything sound better" and eliminating the sound of "digital."
Remember what an EQ is, in theory it's a wire-with-gain type of concept, but with frequency selectivity. So it can turn up or down the levels of certain frequencies. To most people's ears, the closest we can come to a type of volume-control-for-frequencies has only been done by the best linear phase digital EQs using the best sounding data converters.
In any case, a volume control for frequencies cannot have the property of taking away the sound of "digital." To put it another way: No linear EQ functionally can turn down only the digital sound quality embedded in music, because the music, and the "digital" sound people are objecting to, aren't in two different frequency bands.
However, it is possible to make everything you put through it sound better and remove the sound of digital, at least to some people's ears, using certain types of distortion. Personally, I don't usually like boxes for that purpose, as I said before. Maybe I would like this one better. If so and I wanted to use it to make things sound better and less digital, it would be because I like what the distortion does better than I like the distortion of other Pultec clones.
EDIT: "Resolving" is an interesting term to use to describe an EQ. I believe it refers to a perceptual experience quality of sound associated with low level 3rd harmonic distortion, and with other higher order distortion products relatively absent. That is exactly the type of distortion iron core saturation produces, although that's not the only way to produce it. It can sound nice in moderation, as distortion goes, but it is often accompanied by iron core hysteresis distortion which can be less desirable in many cases.
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So who or what is the amp maker you are referring to? Be interesting to know more.
Not quite. ME Amplifiers acquired the rights to use the name, but they do not build products in the same fashion that Peter Stein did. There are a number of crucial differences. Peter's website (such as it is):
http://me-au.com/
Yes Zaphod, there are significant differences between the old and new amps. However, overall it is a good effort. This is what it takes to make truly competitive audio products.
This amp was released in 1988.
The list of features amazed those of us who listened to it for the first time:
* 5kVA @ 5% regulation, split wound, double C core power transformer.
* 100 Amps of current capability.
* Zero global NFB, of course.
* User adjustable Class A bias settings (1W ~ 100W)
* Infinitely variable, AC synchronous fans (2). Fans are controlled by an optical tachometer, which feeds information to an analogue computer which compares output device temperatures. Under normal operation (10 Watts Class A setting), fan speed is typically 200 ~ 300RPM and thus inaudible.
* 92 X 3,300uF filter caps. Each cap is expressly designed for the company, in Taiwan and is very low ESR and ESL.
Attachments
I suppose if you're going to go all in, then dropping a new 240V-30A line from the utility box is the least of your problems!
The largest single phase domestic line available in Australia is *only* 15 Amps. 'Normal' outlets are rated for 10 Amps. FWIW: My audio system runs from a 6 sq mm CSA, single phase run using a 15 Amp receptacle. Also, FWIW: Australian power is much less problematical than US mains power. EVERY single phase Australian outlet will deliver 2,400 Watts at minimal Voltage drop. At the time the amp was released, I attempted to persuade the manufacturer to design a 3 phase variant. It was decided that demand would be too low and complexity too high, despite the many advantages of three phase operation. Imagine how effective the filter caps would be.
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Never compared broken in versus new units or the impossible tropic versus desert.
Cleaning is used to reduce impedance lowering films. Capacitors are made with dielectric films that absorb a trivial amount of moisture but that seems to be enough.
Scott, (As usual!)
-135 is better than -132, but I'd have to dig up the old files I recall the improvement was 15 dB ish for the capacitors I tested.
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Scott,
Still!!!
After break in -115 to -130 should be your line. But as I only was interested in seeing if moisture was the cause I did not do a complete circuit test and have no idea what the final result would be in the complete device under test.
Folks claim to hear differences after break in. I can measure differences in capacitors as do others from break in. Now an interesting test would be to present to claimants units that have been broken in and recording their perceptions.
So as interesting as the "coincidence" may be I have no real informed opinion. I certainly have heard gear that sounds better after being under power for a while.
Is this due to reduction in humidity, reforming of power supply capacitors, internal temperature rise or some other issue? Until more research is done, who knows?
So as interesting as the "coincidence" may be I have no real informed opinion. I certainly have heard gear that sounds better after being under power for a while.
Is this due to reduction in humidity, reforming of power supply capacitors, internal temperature rise or some other issue? Until more research is done, who knows?
Hi Ed,
There is also the well known problem of bias stability over temperature. Early Bryston amps sounded HORRID when just turned on and became almost tolerable after some time that saw the heatsinks become almost too hot to hold your hand on. That's only one example, and I'm pretty certain there are plenty of other amplifiers with similar problems.
My personal belief is that the person becomes used to the equipment rather than the other way around.
-Chris
There is also the well known problem of bias stability over temperature. Early Bryston amps sounded HORRID when just turned on and became almost tolerable after some time that saw the heatsinks become almost too hot to hold your hand on. That's only one example, and I'm pretty certain there are plenty of other amplifiers with similar problems.
My personal belief is that the person becomes used to the equipment rather than the other way around.
-Chris
Sure is. The product range I was discussing with John Curl earlier requires a good 20 ~ 40 minute warm-up time, due to the lack of global NFB. In fact, I did a demo in Canberra one morning. Temperature had fallen to well below zero (Celcius) the night before and the amp was in the car. I set the amp up and switched on. IT was TOTALLY unlistenable. It took almost an hour to reach a point where is was reasonable. The preamps are a particular problem, in that they require a couple of days of being powered up before they sound good. Again, all due to the lack of global NFB.
Hi Zaphod,
I don't think you can involve negative feedback in this process. Using feedback may help some of the circuit remain stable, but not to the extent that the sound quality changes that much. Some equipment with feedback behaves the same way.
A preamp that doesn't stabilize in an hour will never settle down, not ever. The thermal time constant of the room would be a lot shorter than the equipment. The equipment would spend it's life chasing the room temperature up and down.
With the oscillators I'm using (10 MHz Lab standard), it can take a week for an ovenized oscillator to settle back down to it's normal phase performance, but you are talking about something far more critical than sound quality. It can take a double ovenized oscillator (oven within an oven) to reduce room temperature variances to a level within the measurement noise. These are errors around the 10 (exp -13) range. A couple oscillators are locked to the GPS system clocks to maintain exactly correct time, but for critical measurements you unplug the external reference and use the ovenized oscillator built into the equipment. The short term phase noise is lower than the GPS disciplined oscillators. No audio equipment is anywhere near this level of accuracy or stability. If it were, the equipment would be large (to house the physics package) and to isolate the circuitry from the room environment. I guess that means you would have to load up a CD library machine up and seal it for a week. I don't see that happening. Forget trying to manage the temperature of any amplifier!
-Chris
I don't think you can involve negative feedback in this process. Using feedback may help some of the circuit remain stable, but not to the extent that the sound quality changes that much. Some equipment with feedback behaves the same way.
A preamp that doesn't stabilize in an hour will never settle down, not ever. The thermal time constant of the room would be a lot shorter than the equipment. The equipment would spend it's life chasing the room temperature up and down.
With the oscillators I'm using (10 MHz Lab standard), it can take a week for an ovenized oscillator to settle back down to it's normal phase performance, but you are talking about something far more critical than sound quality. It can take a double ovenized oscillator (oven within an oven) to reduce room temperature variances to a level within the measurement noise. These are errors around the 10 (exp -13) range. A couple oscillators are locked to the GPS system clocks to maintain exactly correct time, but for critical measurements you unplug the external reference and use the ovenized oscillator built into the equipment. The short term phase noise is lower than the GPS disciplined oscillators. No audio equipment is anywhere near this level of accuracy or stability. If it were, the equipment would be large (to house the physics package) and to isolate the circuitry from the room environment. I guess that means you would have to load up a CD library machine up and seal it for a week. I don't see that happening. Forget trying to manage the temperature of any amplifier!
-Chris
Dunno about that. A long time ago, I was discussing, with the manufacturer, ways of reducing THD & IMD, so that reviewers would be more favourable towards the equipment. Although THD & IMD remained below 0.1% and thus, likely inaudible, reviewers tended to look at the numbers and denigrate the performance. As a trial, the manufacturer re-jigged one amp to employ a few dB of global NFB. THD fell to around 0.02%. I took part in blind listening tests. Not one tester liked the amp that employed some global NFB. That said, I did note that warm-up time (to optimum sound quality) was reduced dramatically. Probably a few seconds. I never measured it.
Yeah, I get that, but the preamps do take a long time to sound good. Uncertain if it is a temperature thing or an electrolytic cap thing.
I get that. A long time ago, I worked with satellite receivers, cooled with liquid helium. Communications is a different world to audio.
What if the issue is not temperature stability, but the time it takes to drive moisture out of capacitors, or some other unknown mechanism? Just sayin'
Otherwise we are back to people are crazy, when maybe they aren't. Brains tend to make certain errors, but not others. And not all aural perception errors work by the same mechanism.
How to find out which it would be in this case? If the sound is that bad before and that much better afterwards, it would probably be better than nothing to record under both conditions with the same source material using a decent sound card. Then maybe we could hear it for ourselves and see what we think.
If that isn't possible, then my inclination would be to reserve judgment. There is no rush to get a final answer about particular preamp that can't wait.
The legal system is how we decide things when a decision is required in the presence of limited evidence. In that scenario, but sides put forth their best arguments and the jury picks a winner. We end up with a legal fact, which may or may not be the same as a scientific fact.
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