So this is a good one? Does it offer continuous protection or only on startup? Does it affect sound?
http://cgi.ebay.com/Speaker-Protect...trkparms=65:12|66:2|39:1|72:1234|293:1|294:50
http://cgi.ebay.com/Speaker-Protect...trkparms=65:12|66:2|39:1|72:1234|293:1|294:50
Hi Ruwe,
Thanks for your response, read carefully your earlier posts, very helpful. Speaker connections look fine. Am I right thinking that I should take out the 100ohm 1/4 watt resistors from power supplies before connecting to load as they're bound to burn when load is attached and current drawn? This is what I did and amp plays nicely and seems stable now. Resistors and transistors in the input stage (ZTX753 and 653) seem to get rather hot but the heatsinks/output do not overheat after a few hours playing at mid level. One last thing, one of the boards shows a 6 mv difference in quiescent current measured at the output transistors emitter resistors. The one on the positive side measures lower than the one on the negative side (i.e. 2.2mv on +side, 2.8mv on -side). The difference goes away when amp is playing and both sides measure the same. Does this indicate a problem?
Thanks a lot
Thanks for your response, read carefully your earlier posts, very helpful. Speaker connections look fine. Am I right thinking that I should take out the 100ohm 1/4 watt resistors from power supplies before connecting to load as they're bound to burn when load is attached and current drawn? This is what I did and amp plays nicely and seems stable now. Resistors and transistors in the input stage (ZTX753 and 653) seem to get rather hot but the heatsinks/output do not overheat after a few hours playing at mid level. One last thing, one of the boards shows a 6 mv difference in quiescent current measured at the output transistors emitter resistors. The one on the positive side measures lower than the one on the negative side (i.e. 2.2mv on +side, 2.8mv on -side). The difference goes away when amp is playing and both sides measure the same. Does this indicate a problem?
Thanks a lot
DreadPirate said:
This should be good for you:
http://www.ska-audio.com/Forum/YaBB.pl?custompage=products
Or;
http://www.ska-audio.com/Forum/YaBB.pl?custompage=products
The protection circuits on the blue and white clone NAP-140C boards are not speaker protection circuits like the ones mentioned in the last few posts.
The original protection circuits are supposed the keep the amp operating within SOAR, thus protecting the amp from overload. Speaker protection ciruits usually disconnect the speakers from the amp after the amp has failed. Ideally you need both.
regards
The original protection circuits are supposed the keep the amp operating within SOAR, thus protecting the amp from overload. Speaker protection ciruits usually disconnect the speakers from the amp after the amp has failed. Ideally you need both.
regards
Hi marcel5996,
I'm sorry, I'm again very late with my answer.
I don't really understand how removing these 100 ohms resistors fixed your circuit. I was thinking that they protect your amp, and your speakers in the situation that you described... But if it works fine then it doesn't matter anymore...
My ZTX 753/653 also get hot, but not too much. You should feel comfortable keeping your finger on their cases.
The voltage across the emitter resistors should be equal if they are equal. I think that 2.2 mV is too low and you'll have to play a little with the trimmer and increase carefully this voltage to 4.5 - 6 mV. I guess when the amp is cold the emitter current is very low ... 2.2/0.33=6.66 mA , but when you leave it on it increases and the balance between the output transistors becomes better. Do you measure higher DC voltage at the the output, when you see 2.2mV and 2.8mV across the emitter resitors? Are your + and - supply voltages equal?
I don't know whether the circuit is fine, though. It could be just bad solder joint at one end ... who knows, or it may improve when you increase the current. If you feel that it works reliably then leave it alone. Mine is always on, unless we leave home for few days.
Regards.
I'm sorry, I'm again very late with my answer.
I don't really understand how removing these 100 ohms resistors fixed your circuit. I was thinking that they protect your amp, and your speakers in the situation that you described... But if it works fine then it doesn't matter anymore...
My ZTX 753/653 also get hot, but not too much. You should feel comfortable keeping your finger on their cases.
The voltage across the emitter resistors should be equal if they are equal. I think that 2.2 mV is too low and you'll have to play a little with the trimmer and increase carefully this voltage to 4.5 - 6 mV. I guess when the amp is cold the emitter current is very low ... 2.2/0.33=6.66 mA , but when you leave it on it increases and the balance between the output transistors becomes better. Do you measure higher DC voltage at the the output, when you see 2.2mV and 2.8mV across the emitter resitors? Are your + and - supply voltages equal?
I don't know whether the circuit is fine, though. It could be just bad solder joint at one end ... who knows, or it may improve when you increase the current. If you feel that it works reliably then leave it alone. Mine is always on, unless we leave home for few days.
Regards.
Hi Ruwe,
Thanks again for the suggestions. Maybe I wasn't clear about the 100 ohm resistors. They are only 0.25watt under the assumption that they'd burn quickly in case of a short in the circuit, allowing time to quickly turn the amp off before damaging it. The light bulb in series with the main leads would give the same warning if staying lit after power on. What happened was that the resistors (and light bulb) would be fine (no short then) without speaker load. I'm just learning all this stuff, so be patient
, but I believe that the load from the speaker causes a current draw that burns the 0.25 watt resistors. (I used 10 ohm/5 watt in the same position and they don't even get lukewarm). Voltage +- is the same (~47 volts with no load, 42ish under load). You're right in saying that when the amp warms up the output resistors are better balanced, now the difference is only 0.1-0.2 mv. One last thing, dc offset at the output is 12-14mv on one board and 18-20mv on the board that has the uneven quiescent current between the 2 outputs. Any clue what it might indicate? Other than this the amp sounds very nice, next step Nelson Pass B1 preamp. Thanks for the patience...
Thanks again for the suggestions. Maybe I wasn't clear about the 100 ohm resistors. They are only 0.25watt under the assumption that they'd burn quickly in case of a short in the circuit, allowing time to quickly turn the amp off before damaging it. The light bulb in series with the main leads would give the same warning if staying lit after power on. What happened was that the resistors (and light bulb) would be fine (no short then) without speaker load. I'm just learning all this stuff, so be patient
, but I believe that the load from the speaker causes a current draw that burns the 0.25 watt resistors. (I used 10 ohm/5 watt in the same position and they don't even get lukewarm). Voltage +- is the same (~47 volts with no load, 42ish under load). You're right in saying that when the amp warms up the output resistors are better balanced, now the difference is only 0.1-0.2 mv. One last thing, dc offset at the output is 12-14mv on one board and 18-20mv on the board that has the uneven quiescent current between the 2 outputs. Any clue what it might indicate? Other than this the amp sounds very nice, next step Nelson Pass B1 preamp. Thanks for the patience...Hi,
Well with 0.25W resistors this could happen.
About the offset in my opinion everything below 50mV is absolutely fine. I had normally working amp with about 40 mV DC offset. Then I went crazy and I added some adjustment options in the input stage, so now it's about 1-2mV both channels.
The difference between the two channels is caused by the intrinsic differences between the input transistors (the differential pair). Apparently, you have one pair better matched than the other. You can tweak this, I have some info in previous posts, but you really don't need to.
BTW, if you want a preamp I would recommend Aleph P 1.7. This is my newly completed project and it sounds better than B1. May be because it's more quiet and powerful (strange word for a preamp It is also much more expensive project, needs careful match of components etc., but it's worth it. Nelson Pass has provided the whole documentation for us, the DIY guys.
Regards
Well with 0.25W resistors this could happen.
About the offset in my opinion everything below 50mV is absolutely fine. I had normally working amp with about 40 mV DC offset. Then I went crazy and I added some adjustment options in the input stage, so now it's about 1-2mV both channels.
The difference between the two channels is caused by the intrinsic differences between the input transistors (the differential pair). Apparently, you have one pair better matched than the other. You can tweak this, I have some info in previous posts, but you really don't need to.
BTW, if you want a preamp I would recommend Aleph P 1.7. This is my newly completed project and it sounds better than B1. May be because it's more quiet and powerful (strange word for a preamp
It is also much more expensive project, needs careful match of components etc., but it's worth it. Nelson Pass has provided the whole documentation for us, the DIY guys.Regards
I'm finally getting around to building this kit. Two questions: 1) should I offset the larger wattage resistors off the board, are they going to get hot? 2) should the TIP 42C transistors be mounted on a heat sink like the others, or is it fine to leave them free standing without heat sinks? I intend on running these full out with 4 ohm speakers and good power supply (300VA toroids at 40v). I have the blue boards, same as audio tony in Post 328 (hifidiy.net).
Thanks Ruwe,
Will probably leave it alone for a while, before tinkering with hfe matched transistors. Was intrigued by the simplicity of the B1, but will check out the Aleph P 1.7 for sure before deciding which direction I want to take. One last $1million question. A light hum is present at both speakers (B&W CM4), not really the white noise/hiss that I would expect, like a soft buzz. Can only hear it if I put my ears on the tweeters, but nonetheless... it is annoying. It does not increase if i turn the volume up or change if I disconnect the preamp cables. I guess it's caused by some grounding issue. I know this is like opening a can of worms, but has anyone suggestions or is willing to share their experience with speaker hum and the nap clones? By the way I have PCB ground, input ground and speaker ground separately run for each board and starred at the smoothing capacitors common point (all on the DC side let's say. The star point is then joined to the earth ground on the chassis. Thks
Will probably leave it alone for a while, before tinkering with hfe matched transistors. Was intrigued by the simplicity of the B1, but will check out the Aleph P 1.7 for sure before deciding which direction I want to take. One last $1million question. A light hum is present at both speakers (B&W CM4), not really the white noise/hiss that I would expect, like a soft buzz. Can only hear it if I put my ears on the tweeters, but nonetheless... it is annoying. It does not increase if i turn the volume up or change if I disconnect the preamp cables. I guess it's caused by some grounding issue. I know this is like opening a can of worms, but has anyone suggestions or is willing to share their experience with speaker hum and the nap clones? By the way I have PCB ground, input ground and speaker ground separately run for each board and starred at the smoothing capacitors common point (all on the DC side let's say. The star point is then joined to the earth ground on the chassis. Thks
Hi,
Mine is pretty quiet. There is very little hum (120Hz) in bass driver, at full power and my ear on the cone. In the tweeters I have only some white noise. My grounding is basically like yours. I also took the shield from the input cables and put them to earth (I don't know how else to call the 3rd pin on the AC wall plug). My case is tied to this point too for safety, but not the amp star point - my system is grounded through the CD player.
If you hear buzz in the tweeters, no matter what is the volume setting, I would say that your amp is trying to oscillate. It's very easy with this circuit. This amp is very sensitive to speaker cables. Despite all audiophile concepts you'll need highly inductive, low capacitive speaker cables. What cables do you use? I tried with some DIY CAT5 type and it was oscillating like crazy, with more standard wires was fine. Then a friend of mine gave me a pair of QED Silver Anniversary and they were very good in my system. Finally, few months ago I bought Naim NACA5 and I feel safe now I don't know how they managed to do so inductive cables.
Have in mind that the noise is also in result of the grounding of your audio system as a whole, not just the amp. I always make sure that all audio components share the same power distribution outlet. If there are any ground loops they will be shorter.
Regards.
Mine is pretty quiet. There is very little hum (120Hz) in bass driver, at full power and my ear on the cone. In the tweeters I have only some white noise. My grounding is basically like yours. I also took the shield from the input cables and put them to earth (I don't know how else to call the 3rd pin on the AC wall plug). My case is tied to this point too for safety, but not the amp star point - my system is grounded through the CD player.
If you hear buzz in the tweeters, no matter what is the volume setting, I would say that your amp is trying to oscillate. It's very easy with this circuit. This amp is very sensitive to speaker cables. Despite all audiophile concepts you'll need highly inductive, low capacitive speaker cables. What cables do you use? I tried with some DIY CAT5 type and it was oscillating like crazy, with more standard wires was fine. Then a friend of mine gave me a pair of QED Silver Anniversary and they were very good in my system. Finally, few months ago I bought Naim NACA5 and I feel safe now
I don't know how they managed to do so inductive cables.Have in mind that the noise is also in result of the grounding of your audio system as a whole, not just the amp. I always make sure that all audio components share the same power distribution outlet. If there are any ground loops they will be shorter.
Regards.
johnm said:
Agree. I went over this time and time again based on comments stating Q5 silkscreen of the device was backwards, it appears there may be different transistors supplied with different shipments of the kit and they have opposite pin-outs. Q1, Q2, and Q5 should all be checked closely (schematic, board, datasheet of supplied device) to ensure proper orientation.
NAP140 Startup
I'm nearing completion of the assembly. Is the procedure at startup to first ensure trimmers are all the way counterclockwise, then slowly turn while measuring the voltage drop across the R=.22ohm resistor on the emitter of the outputs until I get 7.7mV (V=.035AmpX.22Ohm=7.7mV)?
I'm nearing completion of the assembly. Is the procedure at startup to first ensure trimmers are all the way counterclockwise, then slowly turn while measuring the voltage drop across the R=.22ohm resistor on the emitter of the outputs until I get 7.7mV (V=.035AmpX.22Ohm=7.7mV)?
DreadPirate said:
The confusion arises as there are (at least) two different clone boards. The one I have (small, blue on one side, transparent on top, with gold circuit traces) which is copy of the Avondale NCC200 design, and the longer blue board (originally white?) which is a near exact copy (visually at least - I don't know about component values) of a Naim NAPA circuit board. It's this longer board which has Q5 marked incorrectly (and from what I've read Q1 and Q2), NOT the smaller boards.
It is just the annotated layout of the smaller board in post 328 that is incorrect in regards to Q5.
My (small board) amp is finished and sounds amazing. I'm really quite stunned. I didn't use all the provided parts however, and went back to Naim's proper circuit values rather than Avondale's (from analysing many photos of the NAPA6/3 boards over at Pink Fish Media). Incidently all Naim schematics that I have seen on the net so far appear to be incorrect...
Re: NAP140 Startup
I believe that's correct. You'll probably find (as I did) that you won't get any response from turning the trim pot for a few rotations, then the bias will suddenly start to rise - so watch out for that and take it slowly
I have mine at 5.4V (measured across ONE 0.22 resistor only) and this appears to be the 'sweet spot' for best sound, at least on my boards/build.
You may find this of some use:
http://www.pinkfishmedia.net/forum/showthread.php?t=36057
Good luck
DreadPirate said:
I believe that's correct. You'll probably find (as I did) that you won't get any response from turning the trim pot for a few rotations, then the bias will suddenly start to rise - so watch out for that and take it slowly
I have mine at 5.4V (measured across ONE 0.22 resistor only) and this appears to be the 'sweet spot' for best sound, at least on my boards/build.
You may find this of some use:
http://www.pinkfishmedia.net/forum/showthread.php?t=36057
Good luck
Just bought one of these:-
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=180395541500&ssPageName=STRK:MEWNX:IT
From the picture, the same as the short (Gigaworks) one only even cheaper!! £24 including post.
I'll let you all know what's it's like and how I get on.
Pete
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=180395541500&ssPageName=STRK:MEWNX:IT
From the picture, the same as the short (Gigaworks) one only even cheaper!! £24 including post.
I'll let you all know what's it's like and how I get on.
Pete
Did it again!
Thanks for that. Binding post shorted to chassis, I blew one board, that was also the cause of the hum!! Lesson learned the hard way. Another board is coming, interesting learning process. Since I have partially to rebuild, was wondering if I shoud regulate my PSU. My toroid is 250VA +30-0-30, but raw supply is around 47VDC (my apartment mains are running at 120 VAC). Is this too much for this board? All caps are rated 50 Volt higher, but is it too close? Should I replace BC550's with BC546's? In case I decided to regulate the PSU, will have to go for an external PSU. What's the best recommendation in this case as to where to house rectifiers and smoothing caps? Should I keep the caps with the boards + regulators and put rectifiers with toroid in separate housing? What is the recommended combination? If going separate housing, what's the bes grounding scheme? Apologies for the tons of questions! Many thanks
Hi,
Mine is pretty quiet. There is very little hum (120Hz) in bass driver, at full power and my ear on the cone. In the tweeters I have only some white noise. My grounding is basically like yours. I also took the shield from the input cables and put them to earth (I don't know how else to call the 3rd pin on the AC wall plug). My case is tied to this point too for safety, but not the amp star point - my system is grounded through the CD player.
If you hear buzz in the tweeters, no matter what is the volume setting, I would say that your amp is trying to oscillate. It's very easy with this circuit. This amp is very sensitive to speaker cables. Despite all audiophile concepts you'll need highly inductive, low capacitive speaker cables. What cables do you use? I tried with some DIY CAT5 type and it was oscillating like crazy, with more standard wires was fine. Then a friend of mine gave me a pair of QED Silver Anniversary and they were very good in my system. Finally, few months ago I bought Naim NACA5 and I feel safe now
Have in mind that the noise is also in result of the grounding of your audio system as a whole, not just the amp. I always make sure that all audio components share the same power distribution outlet. If there are any ground loops they will be shorter.
Regards.
Thanks for that. Binding post shorted to chassis, I blew one board, that was also the cause of the hum!! Lesson learned the hard way. Another board is coming, interesting learning process. Since I have partially to rebuild, was wondering if I shoud regulate my PSU. My toroid is 250VA +30-0-30, but raw supply is around 47VDC (my apartment mains are running at 120 VAC). Is this too much for this board? All caps are rated 50 Volt higher, but is it too close? Should I replace BC550's with BC546's? In case I decided to regulate the PSU, will have to go for an external PSU. What's the best recommendation in this case as to where to house rectifiers and smoothing caps? Should I keep the caps with the boards + regulators and put rectifiers with toroid in separate housing? What is the recommended combination? If going separate housing, what's the bes grounding scheme? Apologies for the tons of questions! Many thanks
Naim NAC42.5 Pre-Amp Kit on eBay
Anyone using this kit with their NAP-140 Clone? Would it be a good match?
http://cgi.ebay.com/ws/eBayISAPI.dl...akeTrack=true&ssPageName=VIP:watchlink:top:en
Anyone using this kit with their NAP-140 Clone? Would it be a good match?
http://cgi.ebay.com/ws/eBayISAPI.dl...akeTrack=true&ssPageName=VIP:watchlink:top:en