Thanks for the advice. I use Tannoy reveal 6P and m-audio audiophile firewire with Alesis amplifer. In the m-audio on the first channel of the two I replaced the electrolytic capacitor 10 uF on ceramics. It is easy to hear the difference. I put the amp Alesis instead of myselfmade low-power (30 watts) amplifier based on tda7294. I got the bass, but lost the transparency of sound.
I have an amplifier Parasaund HCA-1000 without any capacitors, apogee mini dac, B&W DM602.
I will carefully compare everything before to spoil Alesis.
Alesis RA100 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
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Dan.
Register and download for free
.Dan.
What makes the Alesis RA100 interesting as an amplifier - is that if you are keen, and read the schematic carefully, I notice that there were at least 4, if not more different designers' ideas ... and a most interesting break from treating LTP/differential pairs as the source of complimentary phase to drive the output transistors.
Indeed, the first line stage is a modest gain LTP (long tail pair / differential pair). It is not in any particularly high-gain configuration. The next set (ignoring all the stuff between) is another LTP ... make sense from a simplicity and symmetry perspective. Yet, the signal which drives the output - one side is taken from that 2nd stage LTP, and the complimentary phase is 'created' by another amplifier section above it. It also has the trimpot that accommodates the output-transistor stage lack-of-perfect gain-matching. (The outputs, being of the complimentary PNP/NPN type between the upper and lower half of the push-pull design, simply won't have very close gain matching. Different processes to make the darn things. So, having a variable gain complimentary phase section for the upper pair of the push-pull duo makes for a convenient and basically necessary way to adjust symmetry of signal amplification, thus reducing distortion to whatever intrinsic optimum the circuit can achieve.
ivanlukic notes the RA100 is 'better sounding' - which may be due to many factors, but we too have found the same observation in practice. The RA100 seems better damped, yet not too tight - allowing the resonant nature of passive speakers to flex a bit in reproduction. This, though not widely regarded as either positive or desirable, turns out to be a common factor amongst amplifiers said to be golden: they're not so tight on the damping factor that they force the cones into submission - even at the point of oscillating due to reverse EMF and the resonant LC circuits set up by wires, crossovers and cone physics (coupling, mass, relative position compared to rest, and so on)
In short - RA100 is a sweet, sweet "reference amplifier". It may not have the ultimate power that some might want (being "only" 50 watts per side of "music power", but it still has those nice 48 volt rails, letting it easily burst upwards of 100 music watts before clipping, and even more at the lower end due to excellent current sourcing and sinking. The RA150 by comparison is symmetric ... and "conventional". At some level, I fail to see why the firm changed so radically. They had a good thing.
Indeed - the same amplifier, with a 70 volt supply, a set of 42 volt regulators and parallel ganged output transistors run in the same push-pull/compensated fashion, could easily have output 100 watts per channel, though it would obviously have needed double the heat-sink area. 225 peak watts too. AND TO BE SURE - the RA150 is clearly not a "150" except in Marketing's rosy lenses.
As I've long advised: if you see economically priced RA100's on Ebay or CraigsList, and they're supposedly "tested and working", then get them. They are, for the price, about as close to the "gold standard" for a transistor-based amplifier as I have yet found. Ugly ducks (usually they're awfully scratched up), but electrons don't know from scratches!
GoatGuy
Indeed, the first line stage is a modest gain LTP (long tail pair / differential pair). It is not in any particularly high-gain configuration. The next set (ignoring all the stuff between) is another LTP ... make sense from a simplicity and symmetry perspective. Yet, the signal which drives the output - one side is taken from that 2nd stage LTP, and the complimentary phase is 'created' by another amplifier section above it. It also has the trimpot that accommodates the output-transistor stage lack-of-perfect gain-matching. (The outputs, being of the complimentary PNP/NPN type between the upper and lower half of the push-pull design, simply won't have very close gain matching. Different processes to make the darn things. So, having a variable gain complimentary phase section for the upper pair of the push-pull duo makes for a convenient and basically necessary way to adjust symmetry of signal amplification, thus reducing distortion to whatever intrinsic optimum the circuit can achieve.
ivanlukic notes the RA100 is 'better sounding' - which may be due to many factors, but we too have found the same observation in practice. The RA100 seems better damped, yet not too tight - allowing the resonant nature of passive speakers to flex a bit in reproduction. This, though not widely regarded as either positive or desirable, turns out to be a common factor amongst amplifiers said to be golden: they're not so tight on the damping factor that they force the cones into submission - even at the point of oscillating due to reverse EMF and the resonant LC circuits set up by wires, crossovers and cone physics (coupling, mass, relative position compared to rest, and so on)
In short - RA100 is a sweet, sweet "reference amplifier". It may not have the ultimate power that some might want (being "only" 50 watts per side of "music power", but it still has those nice 48 volt rails, letting it easily burst upwards of 100 music watts before clipping, and even more at the lower end due to excellent current sourcing and sinking. The RA150 by comparison is symmetric ... and "conventional". At some level, I fail to see why the firm changed so radically. They had a good thing.
Indeed - the same amplifier, with a 70 volt supply, a set of 42 volt regulators and parallel ganged output transistors run in the same push-pull/compensated fashion, could easily have output 100 watts per channel, though it would obviously have needed double the heat-sink area. 225 peak watts too. AND TO BE SURE - the RA150 is clearly not a "150" except in Marketing's rosy lenses.
As I've long advised: if you see economically priced RA100's on Ebay or CraigsList, and they're supposedly "tested and working", then get them. They are, for the price, about as close to the "gold standard" for a transistor-based amplifier as I have yet found. Ugly ducks (usually they're awfully scratched up), but electrons don't know from scratches!
GoatGuy
My friend and I tried his RA100 with small Mackie mixer (I think it was 1202) in my room ten years ago and I can confirm that we both were surprised with quality of sound. It sounded spectacular. Certainly one of the best sounding transistor amps I ever heard and I heard a lot, even indecently expensive amps.
Than couple of years ago I found brand new RA150 at sale for some 120 euros hoping that it is basically same product as RA100. But I was wrong. Neither is it sounding better nor is schematics even similar to RA100. I was disappointed.
Than couple of years ago I found brand new RA150 at sale for some 120 euros hoping that it is basically same product as RA100. But I was wrong. Neither is it sounding better nor is schematics even similar to RA100. I was disappointed.
Lerpa,
If you want more detail and transparency with RA100 you should try loudspeakers with horn loaded HF driver. There is excellent and cheap Eminence Beta 10CX driver that can accept different compression horn drivers for a cost effective monitoring quality sound.
Tannoy Reveal 6 is more like HiFi loudspeaker, too laid back, somewhat rolled off in HF range. You will never get that open sound with it.
If you want more detail and transparency with RA100 you should try loudspeakers with horn loaded HF driver. There is excellent and cheap Eminence Beta 10CX driver that can accept different compression horn drivers for a cost effective monitoring quality sound.
Tannoy Reveal 6 is more like HiFi loudspeaker, too laid back, somewhat rolled off in HF range. You will never get that open sound with it.
Food for thoughts
The following are 1W 8 Ohm FFT measurements of RA-100 (turquoise) and another amp made for studio use, Ashly SRA-120 (grey). RA-100 measures about the same as other PA amps while Ashly SRA-120 harmonics are much lower. Will this be audibly different? Since I haven't done a level matched double blind test, I can't comment on that but what I can speculate is that RA-100 may sound identical to many other amps as long as it's not driven to max.
The following are 1W 8 Ohm FFT measurements of RA-100 (turquoise) and another amp made for studio use, Ashly SRA-120 (grey). RA-100 measures about the same as other PA amps while Ashly SRA-120 harmonics are much lower. Will this be audibly different? Since I haven't done a level matched double blind test, I can't comment on that but what I can speculate is that RA-100 may sound identical to many other amps as long as it's not driven to max.
Attachments
Nonsense. I can distinguish subjective differences between low distortion amps in few minutes listening.
Try to read:
Robert Hurley, The Blind (Mis)Leading the Blind, Editorial, The Absolute Sound issue 183.
also his paper The Role of Critical Listening in Evaluating Audio Equipment Quality, presented to AES. (AES E-Library The Role of Critical Listening in Evaluating Audio Equipment Quality)
Try to read:
Robert Hurley, The Blind (Mis)Leading the Blind, Editorial, The Absolute Sound issue 183.
also his paper The Role of Critical Listening in Evaluating Audio Equipment Quality, presented to AES. (AES E-Library The Role of Critical Listening in Evaluating Audio Equipment Quality)
Yes, many people can do that in subjective evaluation. I've done that too. But subjective and objective comparisons are not the same thing. AES E-Library High-Resolution Subjective Testing Using a Double-Blind Comparator
I'm familiar with Robert Harley and I'll bet many members on this forum know who he is as well. Try to read:
The reviews of his book Amazon.com: Customer Reviews: The Complete Guide to High-End Audio (Acoustic Sound Engineering)
Ah, we're almost heading toward the Can-You-Hear-It jihad!!!
Here's the thing that basically never gets tested rationally and quantitatively: the response and performance of an amplifier over minutes of varied input material, ranging from "full scale" to barest whispers of sound. The "problem" is that all that source which is -40 to -50 dB below "sustained maximum" ... is all but unmeasurable to the probes which pick up the analysis data. And that's where the subjective "I can tell in a few minutes" comes from. The nonlinearities centering around the quiescent is where SO much information is "transformed" by amplifier subtleties.
So much for my 2 cents.
GoatGuy
Here's the thing that basically never gets tested rationally and quantitatively: the response and performance of an amplifier over minutes of varied input material, ranging from "full scale" to barest whispers of sound. The "problem" is that all that source which is -40 to -50 dB below "sustained maximum" ... is all but unmeasurable to the probes which pick up the analysis data. And that's where the subjective "I can tell in a few minutes" comes from. The nonlinearities centering around the quiescent is where SO much information is "transformed" by amplifier subtleties.
So much for my 2 cents.
GoatGuy
How do you explain that GoatGuy and me actually heard the difference between RA100 and RA150? We do not know each other and live tens of thousands of miles away. The amp that we like is no longer produced so we do not have some secret economic agenda to rate it high.
Are we imagining the difference?
Are we imagining the difference?
No. But it is not necessary to match the levels to be able to hear the difference. I am able to hear the difference when I take out the amp's mains fuse from the fuse holder and put the fuse back in opposite direction. I am audiophile for more that thirty years and my ear is so trained to hear the differences.
But I think that the most fascinating thing is that many (most?) non-experts are able to hear the differences while at the same time engineers are claiming that differences can not be heard.
Recently my audiophile neighbor and I discussed one interesting perception. (Neither of us is engineer, I have BA degree in Art History and he is truck driver). We both noticed that many valve amplifiers are better in LF reproduction that most transistor amps. And that is paradox: how come that amps with so bad damping factor are better sounding than "superior technology".
I am waiting with impatience for some engineer to correlate measurements with listening experience but in the meantime I shall rather believe my ears than lab instruments.
I am waiting with impatience for some engineer to correlate measurements with listening experience but in the meantime I shall rather believe my ears than lab instruments.
It is absolutely necessary to match the levels when comparing audio components. Ask any real (not someone who pretends to be one just to sell magazines) experts in this industry.
You have just *destroyed* any credibility you might have had by stating this.
Your "ear" is trained?
Poor ear, don't blame it.
It hears what it hears, I can reasonably trust it within its limitations.
What you have trained is your brain
30 years doing so?
Maybe Pavlov would have something to say about it.
Google "conditioning".
Classical conditioning - Wikipedia, the free encyclopedia
In other circunstances I might have suggested you make a few double blind tests and submit results to AES or something, but since you don't believe in them anyway, it's pointless.
Maybe "Cork Sniffing, Golden Ears and Aliens are among us" Magazine would be interested, though.
I think I'll renew my subscription.
A degraded damping factor will give create a boost around the speaker's resonant frequency, which is some low note like 80 Hz or whatever. Damping factor controls that are fashionable on guitar amps these days used to be found on some home hi-fi equipment the 50's and 60's. Loosening the damping factor enhanced the bass response from the full-range drivers without requiring a more powerful amplifier.
You don't need this kind of trick when you have separate woofers and tweeters, and even separately amplified (sub)woofers. It's nice (or, really, essential) in guitar, of course. More thumping, louder bass is not to be confused with good bass.
Good bass should mean that the speaker complies with the signal, rather than taking it as cue to begin improvising. Which is not to say that less damping is bad. If he overall mechanical and electric damping of the system is at least critical, all should be good.
You really should trust measurements and not your ears. There is all kinds of sound that sounds and feels good, but is not a replica of the input signal. I have great ears that are sensitive to fine differences, yet I don't trust them to tell me what is enhanced and what is starkly reproduced.
Tubes are a nice sounding signal processing effect. They are a music production tool, and not so much a reproduction tool. If, say, a singer chooses to color his voice with a tube mic preamp, that is an artistic decision. How you reproduce that sound for yourself depends on whether you fancy yourself as part of the artistic process, or simply a passive member of the audience. If you think that the art is not finished when the final mix is etched into the distribution medium, and that it benefits from your creative input, then you go ahead and process the audio with tubes or whatever else you have on hand.
Similarly, if you don't like a painting hanging on your wall, you can whip out your acrylics, palette and brushes and fix it up!
Audio processed by tubes is analogous to a postcard photograph that features unreal colors: the grass is greener than reality, the sky more blue, and so on. If you look at that all day, and then step outside, reality might seems "clinical", sterile, dull, ...
Or, if you will, passing audio through tubes is like putting makeup on a woman. It looks beautiful (at least it can), but it's not what the woman actually looks like. It is a distortion of her real face. The "measurement" of the woman before she steps out of the "lab" is that she's Plain Jane; but you'd rather trust your eyes.
OK. This reqires a bit of explanation. I like the combination of push pull EL84 pentodes with Kimber 4TC braided loudspeaker cable. The cable is very low inductance high bandwidth. The cable exposes inherent HF distortions in amp, and serves as some kind of tone control, adds a pinch of sharpness to LF. (Very few transistor amps sounds good to me with this high capacitance cable, transformer coupling helps here). It is impossible to replicate this "tone control" with opamp based preamplifiers. The bottom line is that this combination gives pleasure in listening, no matter how technically flawed.
After all, don't we all like Plain Jane after some beauty treatment? I know that I do.
After all, don't we all like Plain Jane after some beauty treatment? I know that I do.
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