from Jocko Homo:
This has been my experience. Fractions of a dB can make dramatic differences. I have also noted that a slight change (e.g. slight increase) at high frequencies (between 10khz and 20khz) can be perceived by some people as harsher (more apparent high frequency content) and by other people as smoother (less apparent high frequency content). The location of a high frequency resonance will also affect different people differently. This makes for some argument when fine-tuning a speaker system with multiple listeners describing the differences they hear.
So when Lars says he hears better things from his amplifier I believe him. I expect that if we all had several amplifiers to play with we could find our favorite, and it would not be the same amplifier.
My own experiments with the ucd400, comparing to an Audio Research M100 monoblock, has been interesting. These two amplifiers sound more alike that any other two amplifiers in my experience. This is particularly strange because one is a tube amp and one is class D. Somehow they both do the important things right (they are both very good). The biggest difference is a small but significant difference in high frequency response caused by the frequency dependent output impedance of the tube amp (favorable to the electrostatic panels I am using). I am working on this, getting closer to the sound of the M100 amps.
This has been my experience. Fractions of a dB can make dramatic differences. I have also noted that a slight change (e.g. slight increase) at high frequencies (between 10khz and 20khz) can be perceived by some people as harsher (more apparent high frequency content) and by other people as smoother (less apparent high frequency content). The location of a high frequency resonance will also affect different people differently. This makes for some argument when fine-tuning a speaker system with multiple listeners describing the differences they hear.
So when Lars says he hears better things from his amplifier I believe him. I expect that if we all had several amplifiers to play with we could find our favorite, and it would not be the same amplifier.
My own experiments with the ucd400, comparing to an Audio Research M100 monoblock, has been interesting. These two amplifiers sound more alike that any other two amplifiers in my experience. This is particularly strange because one is a tube amp and one is class D. Somehow they both do the important things right (they are both very good). The biggest difference is a small but significant difference in high frequency response caused by the frequency dependent output impedance of the tube amp (favorable to the electrostatic panels I am using). I am working on this, getting closer to the sound of the M100 amps.
I just returned from the AES in Barcelona (hi to those who went to hear the UcD paper), to find a long thread concerning pro's and cons of different amplifier designs. The following answer is an attempt to answer a lot of the points raised in one go.
Firstly I hope the readership will understand LC and myself will not start bashing eachothers design. This would not be good business practice for either of us. We both have our ways of doing things. I will argue later that the details of how we skin the cat should not matter to anyone interested simply in listening to good music.
In my case, the philosophy is to make an amplifier "act like it has no feedback". More precisely, this means insuring that THD is not significantly frequency dependent. The two pillars onto which this rests in UcD designs are
1) Lead compensation. In control theory this is the "D" in "PID". This completely solves this problem some people feel arises with the output filter adding "delay". If indeed I tried adding feedback without lead compensation, loop gain would have to drop enormously at high frequencies, making for a most bizarre THD vs frequency behaviour. Keep in mind that the "delay" of an output filter is not a true delay (=linear phase shift) but that a filter's response to a stimulus is indeed instantaneous, if initially small. Lead compensation allows use of this small response and hence nearly delay-free control loops.
2) constant loop gain across the audio range. In control theory this means not to have an I term (or more precisely, to have a real pole only above 20kHz.
The result is an amplifier with a considerable amount of feedback (some 30dB) that walks and quacks like a good zero feedback design without the disadvantages (THD and frequency response aberrations).
--------------------
On the layout side, as anyone who makes actual circuit boards will attest, there is no such thing as a computer-generated layout. Not in my amps, not in my competitors'. In stuff like computer main boards, autorouters do a lot of groundwork, but in analogue circuits like power supplies and audio amplifiers, the whole layout is drawn by hand using a PCB layout program to help with pointing out the netlist and check consistency.
Here are a few of my layout rules:
1) Have a ground plane that has as little as possible interruptions (large holes or traces) in it, especially around the switching power stage.
2) MOSFET placement: placing devices back to back helps control EMI, by allowing alternating magnetic loops to have the same orientation and area during the switching interval.
3) Capacitive coupling to the cooling assembly: The low-side device has HF on the tab. This will couple capacitively to the heat sink. This capacitive current must be returned directly to the PCB at the site of the power stage.
4) The currents in the switching power stage imposes a voltage across the ground plane. If connections are made to opposing sides of the PCB with the power stage in the middle, they will act like a dipole driven by an RF voltage source. Keep all connections to one side of the power stage, preferably grouped close together. If you must have a connector on the other side for mechanical reasons, the traces (including ground) should emanate from the "correct side" and be routed like a cable to the end that has the connector.
You'll see that it is not possible to instruct a PCB layout program to do this for you. The layout of a class D power stage is a long-winded puzzle that spans many circuit board generations.
The upshot is "Form folgt Funktion". Too many audio circuits are designed with a particular sense of aesthetics in mind, like nice symmetrical boards with the "signal flow" neatly followed. These boards make great photo shoot material, but often fall short from their primary aim, which is to perform electrically. The laws of electromagnetics are oblivious to aesthetics. I'm not among those who claim that PCB layout is an art. It's a skill with sound scientific background. Anything less won't do.
----------------------
I might also point out that there are many valid standards to judge audio amplifiers by, depending on what you want from them. In general they are:
1) Listening pleasure
2) Measured audio performance
3) Others, like EMC, reliability, efficiency, etc.
2 and 3 are tested on the lab bench. 1 is tested in the listening room. All are tested with the amplifier operating and knowledge of the insides is unnecessary (=black box).
Then there is the bad criterion which I find expounded all too often in audio circles.
4) What's inside and what does the schematic look like.
This is a funny criterion for users of amplifiers, since it is tested with the amplifier not operating (the circuit diagram does not change when power is applied), possibly not even existing yet.
For someone who designs amplifiers, the question of construction is obviously a necessary station to pass before we can get anywhere near the previous three. What I can't get my head around is why some people are allowing their listening pleasure to be marred by thoughts about operating principle and such. If an amplifier sounds brilliant, should it sound any less good once the listener is made aware of the fact that it uses feedback? The knowledge of an amplifier's design details is interesting from an academic perspective but is entirely irrelevant when the performance (musical or otherwise) of the box can be tested by simply connecting it and turning on the power.
For example, the discovery that negative feedback often results in substandard sonics is an important one which allows amplifier designers to go and ask themselves "why?" and "what to do about it?". Many people are now getting excellent sound from feedback amplifiers, showing that they have been able to answer these questions with good effect. Subsequently demanding that an amplifier have no feedback around it is simply putting the cart in front of the horse.
Firstly I hope the readership will understand LC and myself will not start bashing eachothers design. This would not be good business practice for either of us. We both have our ways of doing things. I will argue later that the details of how we skin the cat should not matter to anyone interested simply in listening to good music.
In my case, the philosophy is to make an amplifier "act like it has no feedback". More precisely, this means insuring that THD is not significantly frequency dependent. The two pillars onto which this rests in UcD designs are
1) Lead compensation. In control theory this is the "D" in "PID". This completely solves this problem some people feel arises with the output filter adding "delay". If indeed I tried adding feedback without lead compensation, loop gain would have to drop enormously at high frequencies, making for a most bizarre THD vs frequency behaviour. Keep in mind that the "delay" of an output filter is not a true delay (=linear phase shift) but that a filter's response to a stimulus is indeed instantaneous, if initially small. Lead compensation allows use of this small response and hence nearly delay-free control loops.
2) constant loop gain across the audio range. In control theory this means not to have an I term (or more precisely, to have a real pole only above 20kHz.
The result is an amplifier with a considerable amount of feedback (some 30dB) that walks and quacks like a good zero feedback design without the disadvantages (THD and frequency response aberrations).
--------------------
On the layout side, as anyone who makes actual circuit boards will attest, there is no such thing as a computer-generated layout. Not in my amps, not in my competitors'. In stuff like computer main boards, autorouters do a lot of groundwork, but in analogue circuits like power supplies and audio amplifiers, the whole layout is drawn by hand using a PCB layout program to help with pointing out the netlist and check consistency.
Here are a few of my layout rules:
1) Have a ground plane that has as little as possible interruptions (large holes or traces) in it, especially around the switching power stage.
2) MOSFET placement: placing devices back to back helps control EMI, by allowing alternating magnetic loops to have the same orientation and area during the switching interval.
3) Capacitive coupling to the cooling assembly: The low-side device has HF on the tab. This will couple capacitively to the heat sink. This capacitive current must be returned directly to the PCB at the site of the power stage.
4) The currents in the switching power stage imposes a voltage across the ground plane. If connections are made to opposing sides of the PCB with the power stage in the middle, they will act like a dipole driven by an RF voltage source. Keep all connections to one side of the power stage, preferably grouped close together. If you must have a connector on the other side for mechanical reasons, the traces (including ground) should emanate from the "correct side" and be routed like a cable to the end that has the connector.
You'll see that it is not possible to instruct a PCB layout program to do this for you. The layout of a class D power stage is a long-winded puzzle that spans many circuit board generations.
The upshot is "Form folgt Funktion". Too many audio circuits are designed with a particular sense of aesthetics in mind, like nice symmetrical boards with the "signal flow" neatly followed. These boards make great photo shoot material, but often fall short from their primary aim, which is to perform electrically. The laws of electromagnetics are oblivious to aesthetics. I'm not among those who claim that PCB layout is an art. It's a skill with sound scientific background. Anything less won't do.
----------------------
I might also point out that there are many valid standards to judge audio amplifiers by, depending on what you want from them. In general they are:
1) Listening pleasure
2) Measured audio performance
3) Others, like EMC, reliability, efficiency, etc.
2 and 3 are tested on the lab bench. 1 is tested in the listening room. All are tested with the amplifier operating and knowledge of the insides is unnecessary (=black box).
Then there is the bad criterion which I find expounded all too often in audio circles.
4) What's inside and what does the schematic look like.
This is a funny criterion for users of amplifiers, since it is tested with the amplifier not operating (the circuit diagram does not change when power is applied), possibly not even existing yet.
For someone who designs amplifiers, the question of construction is obviously a necessary station to pass before we can get anywhere near the previous three. What I can't get my head around is why some people are allowing their listening pleasure to be marred by thoughts about operating principle and such. If an amplifier sounds brilliant, should it sound any less good once the listener is made aware of the fact that it uses feedback? The knowledge of an amplifier's design details is interesting from an academic perspective but is entirely irrelevant when the performance (musical or otherwise) of the box can be tested by simply connecting it and turning on the power.
For example, the discovery that negative feedback often results in substandard sonics is an important one which allows amplifier designers to go and ask themselves "why?" and "what to do about it?". Many people are now getting excellent sound from feedback amplifiers, showing that they have been able to answer these questions with good effect. Subsequently demanding that an amplifier have no feedback around it is simply putting the cart in front of the horse.
Bruno
I agree with you when you say that it should not matter how the amplifier is designed as long as it sounds good. But a lot of people use their audio interest not just as a way to listen to good music. It is their way of having something the can control and affect in their life. One of the humans strongest characters is that we need answers to everything. If we cannot understand a thing that we are depending on we try to create our own explanations and theories. That is how a lot of people form an opinion on how tube amps are or how feedback affects the signal. It is our way to try to control things that few people understand. This false prejudice is also used to form small groups of people with similar opinions, like fan clubs. Sometimes this false prejudice is also stretched to silly proportions. Why is it that thick black cables almost always sound powerful and smooth whilst thin or flat white cables always sound very transparent and a bit cold? Why do a lot of people find class d amplifiers to be very dynamic? Is it because they are switching 500 000 times per second?!? The output filter slows down most class d amplifiers to only fractions of what a class b can perform.
It is completely true though that it is up to each and everyone what equipment they want to buy and use but as a manufacturer of audio technology this factor can be used to better understand the customer.
I agree with you when you say that it should not matter how the amplifier is designed as long as it sounds good. But a lot of people use their audio interest not just as a way to listen to good music. It is their way of having something the can control and affect in their life. One of the humans strongest characters is that we need answers to everything. If we cannot understand a thing that we are depending on we try to create our own explanations and theories. That is how a lot of people form an opinion on how tube amps are or how feedback affects the signal. It is our way to try to control things that few people understand. This false prejudice is also used to form small groups of people with similar opinions, like fan clubs. Sometimes this false prejudice is also stretched to silly proportions. Why is it that thick black cables almost always sound powerful and smooth whilst thin or flat white cables always sound very transparent and a bit cold? Why do a lot of people find class d amplifiers to be very dynamic? Is it because they are switching 500 000 times per second?!? The output filter slows down most class d amplifiers to only fractions of what a class b can perform.
It is completely true though that it is up to each and everyone what equipment they want to buy and use but as a manufacturer of audio technology this factor can be used to better understand the customer.
Bruno : Hi Bruno
Well a train takes you from A to B. But for some people who are interested in trains it's a lot more fun, if they know how the engine works, where it was built, if it has electic or hydraulic wheel drives, etc. etc. It turn the trip into a magical and fun experience. These are the kind of people you find here on diyaudio.com, only that it's not about trains, but audio. Those who just want to go from A to B don't really care enough to be here. That is why we should give people here in diyaudio.com as much technical details about our amplifiers as possible, of course without compromizing our products. If there were only DIY'ers here, i would gladly post all schematics of ZAPpulse, but i realize there are also many far east producers in here with a time-to-market problem, who will love to 'borrow' my 1000's of hours of experimentation and developing time.
Pabo said:
Lars Clausen said:
I agree with both of you. The point I am trying to make is different. What I mean to say is "make sure your final opinion is not dictated by anything else than what you observe from the unit in operation".
It is of course most desirable to learn further about what makes the amplifier sound such and such but the reverse is not correct. Superficial knowledge of the insides of an amplifier should not lead to presumptions of how it's going to sound.
Saying that "an amplifier is class D" or "it has only feedback" is not a reliable indicator of the resulting performance. There are a lot of subtleties behind general statements like "feedback sounds bad". In this precise case, the subtleties actually exceed the generality. A lot of feedback amplifiers sound hopeless but some outperform non-feedback amplifiers on their own turf (listening pleasure). Likewise, a lot of non-feedback amplifiers sound great but some are ripe for the bin. The statement "feedback sounds bad" is therefore quite wrong.
This is why it's often said that a lot of knowledge is not dangerous but a little knowledge is. I applaud people who study the whole thing in such depth that they can indeed make a reliable guess of the sound quality of an amplifier by simply studying the schematic. However, the problem I was referring to is what I call "audio opinion". In a typical example, audio press live by generalities (upsampling sounds better, negative feedback is bad, single-ended circuits sound better than push-pull). The generalities become myths among the readership and subsequently audio manufacturers find themselves compelled to make changes to the insides of their black box because of what is believed should be inside to make it sound good. Quite often the result will sound worse, but may well sell better because "it's done the right way". We're seeing audio storage formats being promoted this way.
Why I feel so strongly about this is because music lovers have only just broken free from "distortion terror" (=the presumption that ultra-low amplifier THD is a necessary and sufficient condition for good sound). To maintain our independence of ear, we should be on a vigil to keep away from other similarly meaningless preconceptions such as "an amplifier will sound better iff it has less feedback" or "a DAC will sound better iff it has a higher sampling rate" (note iff with 2 "f"). Otherwise we have only landed ourselves in another camp with the same attidude.
Lars Clausen said:
Bruno : Hi Bruno
Those who just want to go from A to B don't really care enough to be here. That is why we should give people here in diyaudio.com as much technical details about our amplifiers as possible, of course without compromizing our products. If there were only DIY'ers here, i would gladly post all schematics of ZAPpulse, but i realize there are also many far east producers in here with a time-to-market problem, who will love to 'borrow' my 1000's of hours of experimentation and developing time.
Hi Bruno and everyone,
First off, nice paper Bruno, it seems anyone can check it out at Hypex.nl, thanks for that too.
Why did you write it anyway, just in case you forgot? I'd think it was more to generate interest in your product amongst those who'd .. exploit it the most, and maybe a few interested clients of the technology.
When you partake in a forum such as this, it's very much the same, only with a slllightly bigger probable audience, where the potential for small clients might even outweigh that of a few larger ones.
At the same time here you have people driven by other interests, such as students, some perhaps for learning others for making the grade, hobbiests, who do it for the pride and joy of it, educational aspect, and sure a few who just want to rip it off, but can they really do with it. It's protected by patent and more so by the cheap cost, that's where you **** me off. As a hobbiest I can't build a very powerful design for anywhere near the amount of money I could if I just bought it.
While it does "bother" me that it's so expensive to build your own, functional unit, from scratch, I hope that won't change with the release of the 700, as I'd no doubt buy it if at all able to. I also realize that buying it gives me the ability to build 20 of them to sell to my friends as cheaply, easily and realiably as I possibly can, or they can, while ensuring a quality far beyond what just about any OEM would be willing to include.
To think that you're now with Hypex and not Philips, after, what's it been, about a year with the UCD180 on the market..
BTW someone once mentioned a signiature edition now that your'e at Hypex, I vew them all as being signiature editions, so things like a gold stamp for more money won't be much of a selling feature in my case at least.
As a hobbiest I also find it design choices of the UCD700 rather interesting, the signiature is plastered all over it.
Lars I agree with your post entirely as well and am glad you share that realization.
I believe you both are very aware that in a market such as you're in quality of product and service are essential to survival, also it wins leniancy and understanding from the consumers when situations do arise. Here we have two good examples of how that should be done.
I appreciate that you both go a step further than the business aspect and help out the hobbiests as well. It's a perfect example of what I think there's room for alot more of, participation in the diy community, even and perhaps especially from the hobbiests end of things. Perhaps there's some benefits you may find there as well.
Best Regards,
Chris
Hi Chris,
Publishing papers is a more powerful sales tool than you'd think. Once you've published a certain share of papers on a subject, people start associating you with the subject. There is little added risk from copycats because for them it is easier simply to reverse-engineer existing hardware than to try and get an amplifier running based on generic drawings and some crude maths.
I take part in this forum because it's fun. As a nice side effect, the positive comments from happy users do send bigger clients our way. I can't say it's an economical way of making publicity because it's much easier and cheaper to send samples to prospective clients and have them play with them.
Cheers,
B.
Publishing papers is a more powerful sales tool than you'd think. Once you've published a certain share of papers on a subject, people start associating you with the subject. There is little added risk from copycats because for them it is easier simply to reverse-engineer existing hardware than to try and get an amplifier running based on generic drawings and some crude maths.
I take part in this forum because it's fun. As a nice side effect, the positive comments from happy users do send bigger clients our way. I can't say it's an economical way of making publicity because it's much easier and cheaper to send samples to prospective clients and have them play with them.
Cheers,
B.
Listening session between the Zappulse 2.3SE and the UCD400
Hello,
My Opinion from the listening session between the Zappulse 2.3SE and the UCD400 from Jan-Peter.
I found the differences between the Zappulse 2.3 SE and the UCD400 very big, the Zappulse has a very open sound, the air/space from the voice of the singer and the instruments from the Zappulse were much more present than the UCD400.
Also was the Zappulse more detailed in placing the instruments, UCD400 I found too tame, it like there was a curtain over the loudspeakers.
My Zappulse has a much larger power supply in the test, I have done that because it was tested on the Dutch forum that you have minimum 1000Va transformer for the Zappulse.
A person were in the assumption that with 2000Va ring core transformer the bass much more under control, and more dynamics than with the 500Va transformator in a Zappulse.
Rudy
Sorry for my bad English
Preamp: AVM
Amplifier: Zappulse 2.3SE monoblock 28 Kg.
Amplimo ringkern transformator 2000Va 2 x 42 Volt.
2 x 47.000µF 80 Volt type Mundorf M-Lytic HC.
DVD Player: Marantz DV17
CD Player: Denon DCD 3560 LClock XO 2.
Speakers: ACR Isostatic RP-400
The picture has a bridged Zappulse in the test was only 1 Zap.
Hello,
My Opinion from the listening session between the Zappulse 2.3SE and the UCD400 from Jan-Peter.
I found the differences between the Zappulse 2.3 SE and the UCD400 very big, the Zappulse has a very open sound, the air/space from the voice of the singer and the instruments from the Zappulse were much more present than the UCD400.
Also was the Zappulse more detailed in placing the instruments, UCD400 I found too tame, it like there was a curtain over the loudspeakers.
My Zappulse has a much larger power supply in the test, I have done that because it was tested on the Dutch forum that you have minimum 1000Va transformer for the Zappulse.
A person were in the assumption that with 2000Va ring core transformer the bass much more under control, and more dynamics than with the 500Va transformator in a Zappulse.
Rudy
Sorry for my bad English
Preamp: AVM
Amplifier: Zappulse 2.3SE monoblock 28 Kg.
Amplimo ringkern transformator 2000Va 2 x 42 Volt.
2 x 47.000µF 80 Volt type Mundorf M-Lytic HC.
DVD Player: Marantz DV17
CD Player: Denon DCD 3560 LClock XO 2.
Speakers: ACR Isostatic RP-400
The picture has a bridged Zappulse in the test was only 1 Zap.
Attachments
Re: Listening session between the Zappulse 2.3SE and the UCD400
Hi,
Can't really be sure if what you're comparing here is the UCD Vs ZapPulse or the ZapPulse small PSU Vs ZapPulse grossly oversized PSU.
It must be the later though because all of the test specs you've provided deal with the ZapPulse, not even a mention as to the VA used with the UCD for instance, for all we know it could have been 10VA on the UCD but not a word of your sonic dissertation of it would have been untrue.
Have you applied for a review mag yet
Could you possibly swap transformers and retest each module with the same PSU for more meaningful listening results? For your own curiosity anyway.
Thanks
BMW850 said:
Hi,
Can't really be sure if what you're comparing here is the UCD Vs ZapPulse or the ZapPulse small PSU Vs ZapPulse grossly oversized PSU.
It must be the later though because all of the test specs you've provided deal with the ZapPulse, not even a mention as to the VA used with the UCD for instance, for all we know it could have been 10VA on the UCD but not a word of your sonic dissertation of it would have been untrue.
Have you applied for a review mag yet
Could you possibly swap transformers and retest each module with the same PSU for more meaningful listening results? For your own curiosity anyway.
Thanks
I have to made some small remarks;
We have listen to an HUGE speakersetup where there was some serious acoustical problems in the low part. The bass was gromming and humming, the loudspeakers were placed about 20-30cm from the wall. So there were a lot of standing waves what creates big peaks in the bass area. For me it was very difficult to get used to this booming sound. Because of this I coudn't make a good opinion between the two different amplifiers.
There is indeed a difference soundwise spoken in the high end of an UcD amplifier and a Class-D amplifier who has not a post-feedback. That's is an HUGE difference in the frequence response with different load above 10kHz.
Hereby a measurement whereby there is NO post-feedback.......
(from top to bottom; 12, 8, 4 and 2 ohm....)
Jan-Peter
Attachments
I think i know what's meant by the "curtain" bmw850 mentions. I have yesterday bypassed the input caps on my ucd400 modules.
This sounds much better, the sound is more open, it seems as though the voices "open up" and now there's real people singing in stead of 'just voices'. Placement is better and somehow the modules sound less dark, less mid-bass or something? A change for the better, in any case.
(jan-peter: try 'mr. bojangles' by robbie williams on 'swing when you're winning' the difference is clearly audible on this track. 'Inside Job' by ilse Delange on 'Dear John' is another good one to test this).
Downside is that you have to be really sure your pre has 0DC on its outputs. (How much dc is too muc in this case?)
Still heaven't heard the zappulses...
This sounds much better, the sound is more open, it seems as though the voices "open up" and now there's real people singing in stead of 'just voices'. Placement is better and somehow the modules sound less dark, less mid-bass or something? A change for the better, in any case.
(jan-peter: try 'mr. bojangles' by robbie williams on 'swing when you're winning' the difference is clearly audible on this track. 'Inside Job' by ilse Delange on 'Dear John' is another good one to test this).
Downside is that you have to be really sure your pre has 0DC on its outputs. (How much dc is too muc in this case?)
Still heaven't heard the zappulses...
The input caps are really garden variety. By all means do experiment with shorting them (or use BG "NP" type caps if you do have a DC problem). I should really stress that the modules are basically "industrial strength" designs that we offer to diy audiophiles for the fun of it, and because we know how far you can take the modules with only minor tweaks. What this does mean is that we can't economically justify using anything other than standard grade parts.
It would also be annoying for our high-end customers if we were to offer fully tweaked boards to the diy community as we would be creating competition for our own customers. That we are selling untweaked boards to diy'ers is already drawing comment from some.
The fact that the modules sound "rather nice" as they come does not mean that's all you can get out of them, far from it. I have a contraption here using slightly modified UcD400's (different output caps, input caps shorted, but otherwise no mods) running off 2x10000uF BG (yes, black gates). The difference with the unmodified modules and BC caps is nothing short of shocking. I would really like to encourage people to start playing around. That's why this clique is called "DIY Audio".
It would also be annoying for our high-end customers if we were to offer fully tweaked boards to the diy community as we would be creating competition for our own customers. That we are selling untweaked boards to diy'ers is already drawing comment from some.
The fact that the modules sound "rather nice" as they come does not mean that's all you can get out of them, far from it. I have a contraption here using slightly modified UcD400's (different output caps, input caps shorted, but otherwise no mods) running off 2x10000uF BG (yes, black gates). The difference with the unmodified modules and BC caps is nothing short of shocking. I would really like to encourage people to start playing around. That's why this clique is called "DIY Audio".
Something of which I picked up a large quantity at an industrial dump. When you take them out of the case, the construction turns out to be cubic, not cylindrical like most film caps. Otherwise the size, value and voltage suggests it's still MKT. But I like them in output filtersPasi P said:
Pasi P said:
For my UcD180 modules I used BG HQ NX types. Smaller ones than original since the UcD180 amps were used for mid and tweeters only. For my UcD400 modules I plan to use no caps. And I replaced the two 22uF 50V caps that are located near the two transistors for the OPAMP rail voltage regulation with 22uf 50V BG caps. However, those two caps are probably not that critical. As the input impedance of the UcD400 is 100k I think, you can use much smaller caps than those 22uF. A small 0.47uF BG HQ non-polar should be OK. No caps would be preferred of course.
Best regards
Gertjan
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