How good are the Pass/AKSA amps in reality? - diyAudio
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Old 9th May 2001, 01:49 AM   #1
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Join Date: May 2001
One of the problems with “rolling one’s own” equipment is the ability of comparing the circuit or even a kit with commercial products before commencing.

It is hardly surprising that, having spent hours building a project, we’d like to think it is the greatest sounding piece of equipment on earth, however this could hardly be considered an impartial opinion. One thing I’ve noticed is that testimonials are often by people upgrading from what I consider to be fairly “low/mid-fi” equipment, hence a substantial improvement is possibly not difficult to achieve.

I presently use an Arcam Alpha 10 as my main amp (A9 CD player/ EPOS ES-22 or ES-11 speakers), however am most impressed with the design philosophy of Mr Nelson Pass, whereby he adopts the KISS principle to great benefit. It would also appear Mr Hugh Dean follows the same principles with his ASKA kit. Given that it is not possible to hear the amplifiers before building, I am interested in hearing the opinions of those who might like to compare some of the Pass or ASKA amplifiers with those that are commercially available.

As an aside, in a previous thread much was mentioned about the wisdom of Mr Pass in making his designs so freely available. In addition to my electronics background, I completed a marketing degree “just for fun” and can certainly testify as to the merits of Mr Pass’ attitude from a commercial perspective. The fact remains that we, as audio enthusiasts pass on our “wisdom” to all those who care to listen (sometimes whether they want to hear it or not!). Goodness knows how many times, upon learning that this is one of my hobbies, an acquaintance will ask for my opinion on suitable audio equipment to purchase. By having a group of audio enthusiasts “on side” a manufacturer essentially has a very large group of “salespeople” selling their product for zero cost. While I would not like to suggest this is Mr Pass’ motivation, I believe it may help put some people’s minds at ease regrading the morals of reverse engineering etc. After all, as someone else pointed out, to another manufacturer, the information is available is already out there, either as patents or as finished products; it is simply naïve to believe otherwise.


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Old 9th May 2001, 03:19 AM   #2
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Join Date: Feb 2001
Location: Columbia, SC
I, too, have little faith in (most) people's opinions of their projects, as far too many of them proclaim religious enlightenment over what appears to be pretty humble equipment. Three possibilities present themselves:
1) Their previous equipment was so pathetic that it really was a revelation. (The same point you made, just stated more baldly.)
2) They have low standards for music reproduction. (A round-about way of saying that they have tin ears--although this can sometimes be remedied by liberal doses of listening to real [unamplified] music, so the condition isn't necessarily fatal.) Most people in this category will vehemently deny that they are members. They're easy to identify--they're the ones who jump and down and tell you that they heard the Beastly Expensive Model 99 at their local salon and that their new amp (based on a car stereo circuit using opamp outputs) whomped it. *Ahem.*
3) It really was a great design. 'Nuff said, if true. We should all be so fortunate.
Although it's not absolutely necessary, it helps to be familiar with some of the better equipment out there so that you have a more accurate assessment of where your own hardware (DIY or bought) stands in relation to The Rest Of The Pack.
In any case, pride can override honest judgement of sonic merit.
I can't speak about ASKA circuits, not having heard any. I can speak regarding the Pass Aleph 2 (at least my version--I'd be interested to hear my DIY compared to a production model, just for fun). Note that I modified the stock Aleph circuit by grafting the input network from a Volksamp onto the stock circuit in order to raise the input impedance, and omitted C6, also per the Volksamp version of the circuit (although I made a spot on the circuit board in case I need it). All else is as per stock.
See the Water Cooled Audio Circuitry thread for my preliminary assessment of the amp's sound. Consider this an addendum:
Regarding image--The Aleph 2 image consistently begins slightly behind the speakers. My tube amp circuit image starts at the plane of the speakers and, sometimes, slightly in front of it. Even on the same material, the Aleph is always further back. If you were to compare the two amps with your eyes closed, trying to throw a wad of paper at, say, the vocalist, the Aleph wad of paper would always end up about three feet (a meter) behind my tube amp's image. My tube amp images approximately where all the other amps I've had in my system image, so it's the Aleph which is different, here. It's not bad or wrong...just different. Since I'm quad-amped, it does lead to a bit of dislocation when an instrument or vocalist goes beyond the range of the mid drivers. I am considering building a second pair of 2's in order to try them on the tweeters or woofer panels to see if the image snaps into place. (Not as big a financial outlay as it might seem--I bought 100 output devices in order to have enough to match and ended up with another nicely matched set. I also bought plenty of input devices.)
Tonality--If I were to say that the amp leans fairly heavily towards the 'dark' sound that many class A solid state amps have, would that tell you anything? This will not be a circuit that will appeal to those who like a bright or forward sound (not to be confused with my description of the image placement--I'm talking about glare in the upper midrange/lower treble that so many people seem to mistake for 'accuracy'). It's not going too far to say that it sounds more 'like tubes' than most solid state amps. If I go through with building a second pair, I'll be better prepared to address treble/bass extension, etc.
Obviously, you should take what I say with a grain of salt, but if you get the impression of a darker, more tube-like sound than you might normally expect from a solid state piece, then perhaps my capsule review might do some good.
Note that I would not expect the Zen to sound quite the same. To its credit, it drops to one gain stage from two. On the other hand, it has electrolytic coupling caps (albeit bypassed with film). The SOZ is an entirely different beast and should sound wonderful if you can take the efficiency penalty.

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Old 9th May 2001, 04:55 AM   #3
grataku is offline grataku  United States
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you must consider the fact that there are many ways to build a circuit from scratch, how well can you solder and wire your projects, if you believe that the components you use and the way you layout the PCB make a difference then it is simply impossible to tell how a certain design will perform. Commercially built stuff, the good ones at least, go through a process of optimization and debugging that usually makes the product work much more smoothly.
As a DIY guy the prototype IS your final product. So if you have a certain amount of experience and did things right everything should be cool.
Bottom line: you must like the concept and the schematic, love it actually. That way you will likely invest a certain amount of money for good components and build it carefully with the goal of having the circuit perform as well as it possibly can.
DIY audio is all about experimentation, crafting and spending money and time looking for a better sound. At the end of the day you get to listen to your creations, that is what makes this hobby great!

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Old 10th May 2001, 01:37 AM   #4
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Thanks for the comments. I agree the question I asked can be difficult to answer given the variables involved and the difficulty in replicating results between builders. An analogy to cooking may be appropriate, that is, the taste of the dish is highly dependant on the quality of the ingredients used. However it is also true to say that the ingredients can be combined in different fashions for what are considered by the majority better or worse results ie the recipe. Likewise what you may enjoy, I may find totally unpalatable.

Given the variables, what I am hoping for is some way I can relate the results of others back to some sort of standard that I, and others, may be familiar with. For example someone may build the ASKA kit using the standard components. Rather than saying “it sounds great”, try to find an objective comparison in the commercial field. That is, “I find it musically slightly bright and forward, possibly similar to a MF X series amp.” Where this may not be possible, say it doesn’t remind you of any particular commercial amp, it should nevertheless be possible to say “If this unit was commercially available I’d expect to pay US$ X for it”, and so on.

I believe this is similar to comparing commercial amps between each other. If I go into a store and see amplifier A costs $500 and amplifier B costs $5000, even without auditioning, I would expect amplifier B should sound “better” to A. While this is straight logic, it is not to say that amplifier A isn’t still a very good amp, and may indeed be better value for money than B. Likewise, in the same price range I will almost certainly prefer one amplifier over another.

While price alone can be highly misleading, it nonetheless does provide a guide, one in which we are unfortunately devoid in the DIY circles. Comparing the finished product to a commercial equivalent not only gives an indication of what level of quality we are talking about, ie is it in the $500 or $5000 range, but helps provide a guide as to whether I am likely to prefer this amplifier over another.

Grat, while I agree with what you’re saying, perhaps my situation is somewhat different in that I worked professionally in the field for many years, left it, and have now returned to it as a hobby. Although I enjoy the satisfaction of building/repairing/modifying, it really has no novelty value to me. I am also no longer familiar with the level of performance DIY builders are achieving these days. As a result I need to feel that my efforts will be rewarded with a result superior to what I am currently using. In other words if I replace the A10 amp I would probably expect to pay, say, US$2000 – 3000 for a significant improvement. Given that I am not prepared to pay that sort of money, I may be able to capitalize on my experience in this field to reduce the cost. However if I am unlikely to see any improvement over what I am presently using I would prefer to spend my time tinkering with other components that will more likely provide an improvement.


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Old 10th May 2001, 02:36 AM   #5
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My 'ingredients' were as follows:
Resistors--Vishay/Dale for the lower wattage parts, Panasonic for the higher wattages
Caps--polystyrene/foil where practical, silver/mica for the little 10 pF critter, Panasonic F-something series...seemed like the best of the best of the best, with honors, sir! of what Digikey had for the circuit electrolytics (I'll look it up if you're curious), and Mallorys for the power supply bulk filter caps
Semis--Motorola for the zeners & MPSA18s, IRF for the MOSFETs (I should have noted above that I'm using the IRF644 for the output devices--seems to be the TO-220 case variant of the same device that Nelson used. You might be able to make a case that the case (ahem) might make some difference in the sound, but I doubt it.)
Heatsinks--See the water-cooled discussion elsewhere. I'm of two minds as to whether the actual physical heat has an effect on the sound. I can argue it both ways. I suppose that I could conduct an experiment wherein I ran the temperature up to about where Nelson ran the actual Aleph 2 and compare the sound hot vs. warm, but I'm not sufficiently motivated to fiddle the heat sink system. It works well and I'm happy with it. (And it didn't cost much, which makes me even happier.)
I did my own artwork and etched my own boards. Standard FR-4 stuff. 1 oz copper for the front end and 2 oz for the output.
Note that I did not use the omigod Vishay, or Caddocks or whatever. Just the better than average stuff that's commonly available from Mouser, Digikey, et. al. If the fancy stuff wasn't so damned expensive ($10 for *one* resistor?, I regard myself as inhabiting the high-end of the audio world, but I draw the line at having to take out a bank loan in order to buy the resistors alone), I'd try it. Perhaps if the price comes down, I'll give it a whirl later.
The results I got were *easily* worth the money I put in. The sound quality is much nicer in the mids than my Thresholds, and is on a par with my tube circuit. Yes, I know, you haven't heard my tube amp, but I used to own a Conrad Johnson Premier One, so I have high standards for tube equipment. I can still drive ten minutes and hear the CJ (a buddy of mine owns it--I rag him from time to time about "my" Premier One) so I'm still pretty familiar with the sound and try to stay semi-current on the better stuff out there. In the last six months I've heard the monster Classe amp (sounds like Classe has always sounded...okay, but kinda bleached and dry, they have a definite 'house sound' that you either like or not) plus one of the smaller ones, the largest Levinson stereo amp (forget the model#), and the big Krell (can't comment on the Krell as the system was extremely poorly set up--pathetic, just pathetic).

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Old 7th June 2001, 08:40 AM   #6
jkeny is offline jkeny  Ireland
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Default aksa amp

Does anybody know if the old AKSA pcb (available from ESP as a board) sounds as good as the new AKSA kit (only available from printedelectronics) The AKSA site states that the old board is not as sonically good as the new one
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Old 16th January 2002, 10:29 PM   #7
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Default ASKA Performance

I built a ASKA 55 mid last year and compared it to my Creek 5350SE with my Vandy 2Cis. I found I preferred the ASKA55. Better bass (tighter, less [excuse the technical term] mush, more extension). Top end seems slightly less forward but has good clarity and detail. Soundstage and imaging are excellent.

Hugh is a real gentleman and gave me infinite help in disgnosing a problem with one channel.

I was building the unit for a second location in my house and it has performed flawlessly. Based on the performance I decided to buy a second ASKA kit and am in the process of building it with a remote control (from oakley electronics), panasonic motorized pot, Holcos, RTX and Black Gate caps in key positions, some other upgrades. It's taken me 4 months to accumulate the bits (from Australia, USA, Belgium, UK) but I may finally get to hear it this weekend. My intent is to get this beast working and sell the Creek and pocket the proceeds.

My correspondence with Hugh indicates I may not like my initial choice of input cap (Musicap) so I may have some iteration before I close the box up.

Anyone considering building the amp should give Hugh the money. he worked long and hard to create the design, provides excellent component and outstanding construction support.
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Old 19th January 2002, 10:15 PM   #8
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Default Pass.Aksa amps

I read with interest your remarks about sound quality.

At the end of the day I think its a case of "they are all a bit different and what is right? anyway."

I have compared the Aleph 3 with a Cary SL70 (Class A 35+35 watt Push Pull Valve amp)in the early stages of the project prior a sorting out some power supply issues and the Aleph compared well.

I would suggest my Aleph 5 would now be equally dynamic.

The Aleph seems quite neutral tonally and has resolution of fine low level detail, but also has power/drive where other single ended value amps fall over.

From this point of view The Aleph is better as it is more neutral, and therefore more accurate playing a wide range of program material.

Would it be of any value if I arranged a proper listening comparison in association with Hugh Dean of Aska and The Melbourne Audio Club of which I am a member?


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Old 19th January 2002, 11:24 PM   #9
JohnR is offline JohnR  Australia
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Pete, while I see where you are coming from, but I can't help thinking you might be asking for a bit much. After all, even if you were to buy a highly-lauded commercial offering, there is no guarantee that *you* would find it better than what you have, or even if you did, worth the money.

Actually, that's the reason I've turned back to DIY, I got tired of being disappointed with the commercial offerings, never mind the $$! An acquaintance has expressed an interest in having a listening session in the next couple of weeks, if that happens then we could do a head to head comparison of an AKSA, a Stratos, and a Plinius. But you know, even then, that will only be the opinions of a couple of blokes listening on a particular set of speakers, source, etc... I guess at least one of them won't be the constructor :-)

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Old 20th January 2002, 12:18 AM   #10
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G'day John. It's interesting to see this thread has resurfaced after all these months.

While you may feel I am asking too much in this question, I'm afraid I really can't find myself agreeing with you. Personal taste and opinion will always exist, whether it refers to DIY or commercial offerings. Not withstanding this point, I believe it’s still possible to compare and rank different amplifiers, even if only broadly. My original question was how a well constructed DIY amp would compare with commercial offerings in blind testing, and what cost advantages (if any) exist in DIY.
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