I quite agree, personally (and I don't have the skills of a designer), it's been a long time since I looked at the specs and schematic of an amp before I got an idea of how it sounds.
I have had so many surprises over the past 20 years that I no longer assume anything.
This is the advantage of being a pro repairer, we listen and it passes through our hands a lot of amp every year, and year after year.
I have had so many surprises over the past 20 years that I no longer assume anything.
This is the advantage of being a pro repairer, we listen and it passes through our hands a lot of amp every year, and year after year.
I envy you with a with that daily workload of listening opportunities. My repair experience was only part-time but I always tried to compare the occasional better quality amps alongside the usual Japanese receivers, amps and the generic rack-system junk that seemed to come my way. Yes, there were plenty of surprises, like I seldom agreed with published reviews and comments but who has the same room, speakers and source to make fair comparisons anyway? - It's just fun 
A voltage on the output of a transformer.
Now if we take a diode of 0.545V vDROP and 60p of capacitance and add 26.9V of secondary AC to it, will it produce different harmonics compared to:
0.6V vDROP and 300pf with 29.6V AC ?
Or some think it will sound the same ? If yes, than i would prepare a setup and test it in real.
Cuz to me there seems to be a huge difference and thus amplifier boards act very differently in these situations.
Now if we take a diode of 0.545V vDROP and 60p of capacitance and add 26.9V of secondary AC to it, will it produce different harmonics compared to:
0.6V vDROP and 300pf with 29.6V AC ?
Or some think it will sound the same ? If yes, than i would prepare a setup and test it in real.
Cuz to me there seems to be a huge difference and thus amplifier boards act very differently in these situations.
hi rensli, you haven't shown or referred to any circuit, input or output for us to be clear on what you are taking about. So far, you have a diode and small capacitor connected in some way to an AC source of about 30V at some unknown frequency but then what? Is 30V the power to the circuit, the signal or both?
Any sound effect will vary with load impedance and frequency because all components with reactance (i.e. inductance or capacitance) have frequency dependent effects. At audio frequencies, a silicon diode just places a step function (i.e a block of current at voltages less than about 0.6V in one direction and a complete block in the other. The output of a single silicon diode is therefore a half-waveform plus a small step discontinuity. What can a small capacitor do to that and where will it be located?
To begin with, you might like to review some diode theory and properties: Chapter 7: Diode application topics [Analog Devices Wiki]
Any sound effect will vary with load impedance and frequency because all components with reactance (i.e. inductance or capacitance) have frequency dependent effects. At audio frequencies, a silicon diode just places a step function (i.e a block of current at voltages less than about 0.6V in one direction and a complete block in the other. The output of a single silicon diode is therefore a half-waveform plus a small step discontinuity. What can a small capacitor do to that and where will it be located?
To begin with, you might like to review some diode theory and properties: Chapter 7: Diode application topics [Analog Devices Wiki]
Well, I work on power switching electronic issues in the last few years and must say that I've never seen anything as clean and nice as these educational articles try to tell us. All junction devices, no matter transistors, diodes, SCRs or others have nasty and sometimes violent switching on and off behavior. Maybe not so in audio applications though.
What rensli says doesn't make any sense to me from the very beginning... I'm just pointing out that switching effects are impossible to predict just from schematic. Experimenting and measuring is the best way to find out what is going on.
In my Naim-like amp I use dual Schottky diodes bridge rectifier and the ripple in some 10x2200uF per side is very clean. I was prepared to fight transients with various snubbers and other techniques, but I liked what I saw and left it as is.
What rensli says doesn't make any sense to me from the very beginning... I'm just pointing out that switching effects are impossible to predict just from schematic. Experimenting and measuring is the best way to find out what is going on.
In my Naim-like amp I use dual Schottky diodes bridge rectifier and the ripple in some 10x2200uF per side is very clean. I was prepared to fight transients with various snubbers and other techniques, but I liked what I saw and left it as is.
I understand what you mean about theory V reality. It's true of any physical science but we have to begin there, otherwise what we observe has no coherent meaning or reference point. Circuit behaviour and audio experiences just fall back into mystery and unrelated facts that only boggle our imagination (hmm... isn't that how sales talk works? )
Think of circuit simulations with software designed with the power switching industry in mind - LT spice. Funny enough, it does work rather precisely with audio waveforms and harmonics but human impressions involving a mix of the real world with our mental filtering processes is another thing altogether.
Sometimes the colours and objects in a room, the presence of something or someone we have strong feelings about, will change our perception of the music and particular frequency ranges, both now and in future. I've heard people change their mind radically about the same gear and effects they have also listened to in the past - just a few of the problems with listening tests and satisfying others.
)Think of circuit simulations with software designed with the power switching industry in mind - LT spice. Funny enough, it does work rather precisely with audio waveforms and harmonics but human impressions involving a mix of the real world with our mental filtering processes is another thing altogether.
Sometimes the colours and objects in a room, the presence of something or someone we have strong feelings about, will change our perception of the music and particular frequency ranges, both now and in future. I've heard people change their mind radically about the same gear and effects they have also listened to in the past - just a few of the problems with listening tests and satisfying others.
I agree with all that. The moment we are out of the measurement territory there are no rules. Personality, taste, age, climate, mood, listening level, company of friends or unpleasant people, culture...
I like mostly jazz and classical, I doubt a system recommended by a hip-hop fan would suit me.
About Spice, the only time I have had good correlation was when the circuit had been measured and the simulation tweaked to match. It's a great design tool. It saves a lot of time, but you can't rely on it to tell you anything about parasitics. Especially in complex circuits with feedback etc. I talk only from personal experience though. Maybe some people manage to design in simulation and have exactly the same on the pcb...
I like mostly jazz and classical, I doubt a system recommended by a hip-hop fan would suit me.
About Spice, the only time I have had good correlation was when the circuit had been measured and the simulation tweaked to match. It's a great design tool. It saves a lot of time, but you can't rely on it to tell you anything about parasitics. Especially in complex circuits with feedback etc. I talk only from personal experience though. Maybe some people manage to design in simulation and have exactly the same on the pcb...
A simulator is a mathematical equation solver. All the component icons are equations, simplified versions of real parts. This is really useful because I find solving the maths of just a few components with pen and paper a struggle. And I make mistakes.
As usual with computers, it’s garbage in garbage out. Lots is simplified away by default such as trace impedance, many non-linearities, electromagnetic coupling and so on.
What I find most useful is going from audition to bench and then theorizing a cause and using a simulator to reengineer to minimize that cause. Playing with ideas. Otherwise what is your simulation goal (aside from basic functionality)? It’s easy to make a distortionless circuit in a simulator.
In the 1970s, Naim probably had very little CAD if any at all. So it was down to listening and lab T&M equipment, probably all analogue. You can get a good result with a simple circuit this way if you know what to measure. When the circuits contain many components in complex configurations a simulator is essential; it’s just too hard to get your head around what’s going on otherwise.
As usual with computers, it’s garbage in garbage out. Lots is simplified away by default such as trace impedance, many non-linearities, electromagnetic coupling and so on.
What I find most useful is going from audition to bench and then theorizing a cause and using a simulator to reengineer to minimize that cause. Playing with ideas. Otherwise what is your simulation goal (aside from basic functionality)? It’s easy to make a distortionless circuit in a simulator.
In the 1970s, Naim probably had very little CAD if any at all. So it was down to listening and lab T&M equipment, probably all analogue. You can get a good result with a simple circuit this way if you know what to measure. When the circuits contain many components in complex configurations a simulator is essential; it’s just too hard to get your head around what’s going on otherwise.
The issue of the soundtrack is the music production, not the amplification or the rest of the audio system. It's electronically generated audio, as defined by the generator chip(s), filter settings etc and there is no fixed, identifiable sound quality to compare, other than for producers to say it is played on a brand/model XX synthesizer, brand YY drum generator and so on. In fact, the best way to hear the sound effects you prefer, is to synthesize them yourself with your own keyboard and settings.
Forget tweaking amplifiers, because all the adjustments and effects can then be done much faster, cheaper, easier in software settings i.e. compose, play or edit your own music as you like to hear it. Many people have being doing this at home for around 40 years now but there are no surprises if you mistake this type of music to be anything more than musical cliches, played with electronic keyboards, drum machines etc - all compiled and edited in cyber-space.
For me, its awful stuff and in this case, with a dark, morbid theme and I'd rather listen to a jug band, a few guys playing jazz with acoustic instruments, a classic 4-piece rock band or a full pro. orchestra playing the treasured concert music pieces of long ago. You can hear what people really like in your own towns and cities, everywhere. You won't find much enthusiasm there, for some guy with headphones on, playing sombre synthesizer music though.
Forget tweaking amplifiers, because all the adjustments and effects can then be done much faster, cheaper, easier in software settings i.e. compose, play or edit your own music as you like to hear it. Many people have being doing this at home for around 40 years now but there are no surprises if you mistake this type of music to be anything more than musical cliches, played with electronic keyboards, drum machines etc - all compiled and edited in cyber-space.
For me, its awful stuff and in this case, with a dark, morbid theme and I'd rather listen to a jug band, a few guys playing jazz with acoustic instruments, a classic 4-piece rock band or a full pro. orchestra playing the treasured concert music pieces of long ago. You can hear what people really like in your own towns and cities, everywhere. You won't find much enthusiasm there, for some guy with headphones on, playing sombre synthesizer music though.
Hi All!
I just got my hands on a 140 clone from China and had tried to read from the beginning of this thread (2007) but got overwhelmed by pg10.
Anyway, I was trying to figure out the biasing current at the output transistors and noticed that they had used a pair of 0R33 instead. The series resistor at the output is also 0R33.
1. Does it matter much if it is 0R22 or 0R33 other than a 50% increase in voltage across the resistors for the same bias current (15~20mA, ya?)?
2. Does it matter if these 2 resistors are wirewound or metal film type?
3. Do you think putting a metal film // to the installed wirewound to bring the resistance down to 0R22 is a bad idea?
I just got my hands on a 140 clone from China and had tried to read from the beginning of this thread (2007) but got overwhelmed by pg10.
Anyway, I was trying to figure out the biasing current at the output transistors and noticed that they had used a pair of 0R33 instead. The series resistor at the output is also 0R33.
1. Does it matter much if it is 0R22 or 0R33 other than a 50% increase in voltage across the resistors for the same bias current (15~20mA, ya?)?
2. Does it matter if these 2 resistors are wirewound or metal film type?
3. Do you think putting a metal film // to the installed wirewound to bring the resistance down to 0R22 is a bad idea?
Great! There's nothing I need to do at this moment! Now, what can I fiddle with
?
As a matter of interest, how much power output is this clone kit designed for? Is there a power supply recommendation?
Can you post at least a link to this or a very similar kit or finished example product?
We usually see nonsense numbers quoted for Chinese kits. 'don't know where they originated from but they seldom have much to do with what comes in the little plastic bag. They may just be quoted from the original product spec or just transcribed from another kit seller's blurb. You may never know what you really have until you test it almost to destruction - something you aren't likely to try, I assume.
Can you post at least a link to this or a very similar kit or finished example product?
We usually see nonsense numbers quoted for Chinese kits. 'don't know where they originated from but they seldom have much to do with what comes in the little plastic bag. They may just be quoted from the original product spec or just transcribed from another kit seller's blurb. You may never know what you really have until you test it almost to destruction - something you aren't likely to try, I assume.
The chinese market for consumer audio is somewhat like what was in the 80s and before, when music output was measured in "Watts PMPO"...LOL! I guess their domestic consumers aren't really bothered coz these are not big ticket items.
Anyway, it came with what looks like a 150~200W transformer, no label on it. I believe it is 26-0-26V into a tiny rectifier + spkr protection board. Output is +/-36Vdc.
https://item.taobao.com/item.htm?sp...f4S2no&id=655737014077&ns=1&abbucket=4#detail
Well, for $100, I get a working amp to mess around with so I'm quite happy. But the weirdest thing I found on this amp is that the transistors are 'glued' onto the heatsink plate using what looks like silicone caulk!!!
Just some notes when you buy from taobao or ali or sellers from similar platforms.
i. check if the chassis is properly earthed before power on.
ii. Don't use their supplied power cord, or at least check the point to point connectivity at both ends. Ever encountered 3-pin power cord but is really a 2-core cable, ie, there is no earth connection.
At US$100, almost anything that made sound would be a bargain. Anyway, the voltage is about right for a NAP140, which runs on around +/-34VDC rails. Commonly though, I see mostly alleged NAP 140 kits which are actually based on the NAP250 design (i.e. the power amplifier section only - not including it's separate, matching regulated PSUs) and it also has different "tuning". So, because it perpetuates a number of cloning blunders from past decades and also some poor substitute components, kits often turn out so-so in sound quality. I think a chip amp usually sounds better but that's a matter of taste, I guess.
It's been years since I measured the transformer sag at full rated power but it does affect what you hear. What happens when you don't have a big enough power supply is that sound compresses and clips on peaks. Otherwise, it may not suit the design's capabilities and "voicing" if your transformer is too large for whatever model you intend to use it with. If you're interested, there's a summary article of stuff like original transformer details of the old models here: http://www.acoustica.org.uk/t/naim/power_amps.html
'No idea what "silicone caulk" is like but any rigid bond to aluminium that undergoes heat cycling, is likely to fail soon. I guess you now know where some of the the kit's cost savings were made, though.
It's been years since I measured the transformer sag at full rated power but it does affect what you hear. What happens when you don't have a big enough power supply is that sound compresses and clips on peaks. Otherwise, it may not suit the design's capabilities and "voicing" if your transformer is too large for whatever model you intend to use it with. If you're interested, there's a summary article of stuff like original transformer details of the old models here: http://www.acoustica.org.uk/t/naim/power_amps.html
'No idea what "silicone caulk" is like but any rigid bond to aluminium that undergoes heat cycling, is likely to fail soon. I guess you now know where some of the the kit's cost savings were made, though.
OK, being a Taobao Chinese language site, your link doesn't work for me but this alternative English language link to the product seems to:
https://parcelup.com/shop/item.php?id=655737014077
Is this what you refer to?
https://parcelup.com/shop/item.php?id=655737014077
Is this what you refer to?