Hi All, Thanks for the positive feedback Ian and Barry, I probably spent more time designing and building the casework than anything else (including my family, bad boy), The fascias are finished in Hy-Cote satin black, and the main case in VHT Super wrinkle which is an absolute pain until you get used to applying it.
I don't know if the photo is giving an accurate view, those sinks are about 40mm high, 110mm long and 25mm deep, I know the coupling method may not be ideal, but as I said this was my first ever project and the transistors barely get warm and certainly not hot.
The small board is a LM317 circuit to provide 12vdc to the speaker protection board in the upper left.
And as correctly guessed the external PSU is for the Pre only with a SNAIC type cable providing a regulated 15vdc.
I don't know if the photo is giving an accurate view, those sinks are about 40mm high, 110mm long and 25mm deep, I know the coupling method may not be ideal, but as I said this was my first ever project and the transistors barely get warm and certainly not hot.
The small board is a LM317 circuit to provide 12vdc to the speaker protection board in the upper left.
And as correctly guessed the external PSU is for the Pre only with a SNAIC type cable providing a regulated 15vdc.
Nigel Pearson: The arrangement with 2 recitfier bridges will prevent the charging current for the caps to pass through GND point between the 2 series connected caps. That's the advantage. And since it cost almost nothing to do it, there is no good reason to use a single rectifier solution. BUT there is one drawback. You can no longer use a 3 wire transformer, like many nice chinese O or U core types. Only 4 wire types will work.
Background: If you consume 2A average current, that's the current going out of your capacitor bank. But this current is not charged equally from your transformer. Typically the current is charged into your capacitor bank in about 10% of the time. So that's a charge current of 20A potentially going through your GND point, in case you use a single rectifier, and both caps in series. No star GND point will save you from hum in that case. Just use a 2 rectifier setup, then the charge current will go directly to each capacitor instead, and NOT into the GND point. Well unless you feel you have to use the star GND which - i think you take away from this - you should avoid at all cost ;-)
Background: If you consume 2A average current, that's the current going out of your capacitor bank. But this current is not charged equally from your transformer. Typically the current is charged into your capacitor bank in about 10% of the time. So that's a charge current of 20A potentially going through your GND point, in case you use a single rectifier, and both caps in series. No star GND point will save you from hum in that case. Just use a 2 rectifier setup, then the charge current will go directly to each capacitor instead, and NOT into the GND point. Well unless you feel you have to use the star GND which - i think you take away from this - you should avoid at all cost ;-)
Nigel Pearson: The arrangement with 2 recitfier bridges will prevent the charging current for the caps to pass through GND point between the 2 series connected caps. That's the advantage. And since it cost almost nothing to do it, there is no good reason to use a single rectifier solution. BUT there is one drawback. You can no longer use a 3 wire transformer, like many nice chinese O or U core types. Only 4 wire types will work.
Background: If you consume 2A average current, that's the current going out of your capacitor bank. But this current is not charged equally from your transformer. Typically the current is charged into your capacitor bank in about 10% of the time. So that's a charge current of 20A potentially going through your GND point, in case you use a single rectifier, and both caps in series. No star GND point will save you from hum in that case. Just use a 2 rectifier setup, then the charge current will go directly to each capacitor instead, and NOT into the GND point. Well unless you feel you have to use the star GND which - i think you take away from this - you should avoid at all cost ;-)
Background: If you consume 2A average current, that's the current going out of your capacitor bank. But this current is not charged equally from your transformer. Typically the current is charged into your capacitor bank in about 10% of the time. So that's a charge current of 20A potentially going through your GND point, in case you use a single rectifier, and both caps in series. No star GND point will save you from hum in that case. Just use a 2 rectifier setup, then the charge current will go directly to each capacitor instead, and NOT into the GND point. Well unless you feel you have to use the star GND which - i think you take away from this - you should avoid at all cost ;-)
Hi
and what about those assembled kits? are they ok?anybody knows?
140 Classic Naim Clone Stereo Amplifier Full Assembled | eBay
thanks
and what about those assembled kits? are they ok?anybody knows?
140 Classic Naim Clone Stereo Amplifier Full Assembled | eBay
thanks
You'll find that long links to Ebay don't work anymore. Google for instructions on short links or try editing the link down to just the item number or simply copy the item number to your post so that others can paste that into their browser where Google etc. will find it. That's new Ebay policy, nothing to do with forums or the web.
Otherwise, the assembled kits are the same kits based on LJM boards as those that were unassembled - They won't be different except with periodic revisions, like most kits.
Less fun perhaps, though less assembly mistakes this way.
Otherwise, the assembled kits are the same kits based on LJM boards as those that were unassembled - They won't be different except with periodic revisions, like most kits.
Less fun perhaps, though less assembly mistakes this way.
You'll find that long links to Ebay don't work anymore. Google for instructions on short links or try editing the link down to just the item number or simply copy the item number to your post so that others can paste that into their browser where Google etc. will find it. That's new Ebay policy, nothing to do with forums or the web.
Otherwise, the assembled kits are the same kits based on LJM boards as those that were unassembled - They won't be different except with periodic revisions, like most kits.
Less fun perhaps, though less assembly mistakes this way.
sorry about that...here is item number:
110615057463
Yes - LJM boards. No problem with these later revisions and I have seen several of them as kits and preassembled. The supplier has been good for me and some friends too, over a few years now.
I think that some substitute transistors used in kits and are not the best types for this design. You may try substituting the VAS and CS transistors at some time in the future as the sound quality may be poor until the original compensation capacitance is restored. i.e use original ZTX753/653 transistor pair for TR4/6. The difference made by these higher capacitance types can be dramatic. Either way, hope you enjoy it.
See older posts for the Naim schematic and posts discussing the parts subs.
I think that some substitute transistors used in kits and are not the best types for this design. You may try substituting the VAS and CS transistors at some time in the future as the sound quality may be poor until the original compensation capacitance is restored. i.e use original ZTX753/653 transistor pair for TR4/6. The difference made by these higher capacitance types can be dramatic. Either way, hope you enjoy it.
See older posts for the Naim schematic and posts discussing the parts subs.
120W should be written as 120VA on a transformer but the power anyway, is insufficient for 2 channels. The power output of NAP 140 is rated 70W/ 8 ohms and 100W /4 ohms, each channel. Allowing for 65% efficiency and music program, you would need at least 250 VA for a stereo amplifier that delivers full rated power before clipping (if the protection/ limiting circuits are not retained).
Take a look at Google images of original NAP 140 on the internet. It will help to realise what is necessary. Type "NAP 140 pics" - it works for me anyway!
Alternatively, 2 transformers like yours, with separate rectifiers and smoothing capacitors might make a very nice dual-mono amplifier. However, if you are careful not to use much bass or high volume, the small transformer will still work ok and make a good testing power supply but it will run out steam with a stereo amplifier as the supply voltages will drop quite a bit with the signal when driving a load.
Take a look at Google images of original NAP 140 on the internet. It will help to realise what is necessary. Type "NAP 140 pics" - it works for me anyway!
Alternatively, 2 transformers like yours, with separate rectifiers and smoothing capacitors might make a very nice dual-mono amplifier. However, if you are careful not to use much bass or high volume, the small transformer will still work ok and make a good testing power supply but it will run out steam with a stereo amplifier as the supply voltages will drop quite a bit with the signal when driving a load.
Since you have already spent the money, It will have to be fine!
As the difference from, I think, 275 VA is not large, It should be fine under most circumstances.
If you play dance music etc, up loud, I would consider > 300VA. or 2 x 160 VA. That's just an opinion, though.
It is up to you, but the advantages of dual-mono will outweigh the problem of small transformers with reduced headroom output.
Dual mono requires a complete separation of power supplies after the transformer primary windings -
through to the output terminals. Only signal input ground will be common to both amplifiers and there
a few ways to make low noise power supplies. Search this topic for the best PSU arrangement before beginning.
As the difference from, I think, 275 VA is not large, It should be fine under most circumstances.
If you play dance music etc, up loud, I would consider > 300VA. or 2 x 160 VA. That's just an opinion, though.
It is up to you, but the advantages of dual-mono will outweigh the problem of small transformers with reduced headroom output.
Dual mono requires a complete separation of power supplies after the transformer primary windings -
through to the output terminals. Only signal input ground will be common to both amplifiers and there
a few ways to make low noise power supplies. Search this topic for the best PSU arrangement before beginning.
Hi all,
I have a problem, one channel has DC offset is ~14v, other channel is ~100mv, I changed all of transistors BC550 (3 transistors) of error channel but DC offset is ~14v. Before I sat bias at 8mv (all channel), it broken one 2SC5200 and I changed it, other channel not broken 2SC5200 (when I adjust bias two 2SC hotter or cooler) but DC offset is ~14v like above. I don't know why ?! Who can help me ? Sorry, Im not good English
I have a problem, one channel has DC offset is ~14v, other channel is ~100mv, I changed all of transistors BC550 (3 transistors) of error channel but DC offset is ~14v. Before I sat bias at 8mv (all channel), it broken one 2SC5200 and I changed it, other channel not broken 2SC5200 (when I adjust bias two 2SC hotter or cooler) but DC offset is ~14v like above. I don't know why ?! Who can help me ? Sorry, Im not good English
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One thing to do is look for solder bridges . Also when building kits check each transistor before inserting . Do all the same ones at a time as anything odd should stand out . That would be something NPN that should be PNP and of a very different gain . It is so hard to read what the transistors say these days . White ink would help . Most test meters have this function and explain how to do it .
If the PCB is already built measure across each resistor . An auto-ranging meter helps . The absolute reading is not important if one channel works . It is that R 1 should = R1 on each and R2 etc . Try across capacitors also and look to see they are correctly inserted . It is unlikely a wrongly inserted capacitor can be saved . If so go to a higher grade and do both amps . Panasonic FC usually a good device .
I am sure Ian will have more advice . I am 99% certain this method will show the problem area . Also do a simple diode test on the transistors .B to E , B to C . With luck 0.7 V ( 0.5 to 0.8 ) should show in one direction and not the other . If it does show than it should be the same on both . Sometimes a transistor is used as a diode and will show 0 ohms on a terminal pair . If so it will be the same on both amps .
I try hard to speak French and a little Spanish . Your English is fine , I appreciate how hard it is .
If the PCB is already built measure across each resistor . An auto-ranging meter helps . The absolute reading is not important if one channel works . It is that R 1 should = R1 on each and R2 etc . Try across capacitors also and look to see they are correctly inserted . It is unlikely a wrongly inserted capacitor can be saved . If so go to a higher grade and do both amps . Panasonic FC usually a good device .
I am sure Ian will have more advice . I am 99% certain this method will show the problem area . Also do a simple diode test on the transistors .B to E , B to C . With luck 0.7 V ( 0.5 to 0.8 ) should show in one direction and not the other . If it does show than it should be the same on both . Sometimes a transistor is used as a diode and will show 0 ohms on a terminal pair . If so it will be the same on both amps .
I try hard to speak French and a little Spanish . Your English is fine , I appreciate how hard it is .
Hi Nigel, trust you are well.
You are right with likely assembly faults and from what I hear, this is about all that goes wrong now there are only 2 boards commonly available; the blue LJM marked board and the plain H140 board without TR7,8 protection circuits. Both are now trouble-free, from what I hear. From what luckyluke says, having 2SC5200 power transistors, this is probably the H140 kit.
Many people are ill-prepared for electronic kit construction and can't read colour coding on resistors and so resort to measuring them which is still good, as it reduces the number of bad or incorrectly fitted parts but doesn't help with substituted semis having different pinouts. You can check by Googling "2SCxxx pinout" or whatever, if they are not as per the schematic or printed overlay.
As Nigel says, correct orientation of electrolytic caps and diodes is also essential but you do have the markings, so check them against the schematic too. If these are all OK, bad solder joints are the next most likely fault. Test the joints with the continuity beeper on your multimeter. If you don't have one, make a continuity tester with a battery and torch globe. Note that a DMM may read OK but the circuit may not pass enough current to work properly.
As you have one working channel, It should be easy to trace the area of a fault by comparing DC voltages at different nodes on either channel. I would suspect a fault in the voltage amplifier for instance, involving TR4,5,6 but I am not yet certain.
Approx. 0.7V should also be measured from B-E on each transistor when powered, to check that it is really wired correctly and likely functional. If you have not read enough of this thread or taken advice on powering amplifiers for the first time read this:
Never power up new amplifiers without a current limiting device!
This can be a "http://www.diyaudio.com/forums/equipment-tools/252386-bulb-limiter-testing.html#post3844592" or you can fit a couple of 100R 1/2 Watt resistors in place of the fuses supplying DC to the board. Simply solder them across the clips.
The reason is not only to protect components but give you the chance to measure faults and set bias approximately without damage. If you don't take precautions, you only have yourself and the lack of full instructions to blame for damaged parts. The kit suppliers assume you know what you are doing, don't supply spare parts, nor instructions or a manual of audio amplifier design. When things go badly wrong, parts will inevitably burn, even your protection resistors, maybe without even knowing.
If you don't have a schematic to refer to, you could use the original one posted a few times already in this thread or post your clone's version here, perhaps marking any large voltage differences, so we know what you may refer to.
You are right with likely assembly faults and from what I hear, this is about all that goes wrong now there are only 2 boards commonly available; the blue LJM marked board and the plain H140 board without TR7,8 protection circuits. Both are now trouble-free, from what I hear. From what luckyluke says, having 2SC5200 power transistors, this is probably the H140 kit.
Many people are ill-prepared for electronic kit construction and can't read colour coding on resistors and so resort to measuring them which is still good, as it reduces the number of bad or incorrectly fitted parts but doesn't help with substituted semis having different pinouts. You can check by Googling "2SCxxx pinout" or whatever, if they are not as per the schematic or printed overlay.
As Nigel says, correct orientation of electrolytic caps and diodes is also essential but you do have the markings, so check them against the schematic too. If these are all OK, bad solder joints are the next most likely fault. Test the joints with the continuity beeper on your multimeter. If you don't have one, make a continuity tester with a battery and torch globe. Note that a DMM may read OK but the circuit may not pass enough current to work properly.
As you have one working channel, It should be easy to trace the area of a fault by comparing DC voltages at different nodes on either channel. I would suspect a fault in the voltage amplifier for instance, involving TR4,5,6 but I am not yet certain.
Approx. 0.7V should also be measured from B-E on each transistor when powered, to check that it is really wired correctly and likely functional. If you have not read enough of this thread or taken advice on powering amplifiers for the first time read this:
Never power up new amplifiers without a current limiting device!
This can be a "http://www.diyaudio.com/forums/equipment-tools/252386-bulb-limiter-testing.html#post3844592" or you can fit a couple of 100R 1/2 Watt resistors in place of the fuses supplying DC to the board. Simply solder them across the clips.
The reason is not only to protect components but give you the chance to measure faults and set bias approximately without damage. If you don't take precautions, you only have yourself and the lack of full instructions to blame for damaged parts. The kit suppliers assume you know what you are doing, don't supply spare parts, nor instructions or a manual of audio amplifier design. When things go badly wrong, parts will inevitably burn, even your protection resistors, maybe without even knowing.
If you don't have a schematic to refer to, you could use the original one posted a few times already in this thread or post your clone's version here, perhaps marking any large voltage differences, so we know what you may refer to.
Hi everyone , yes I am well .
I have to say every time I fault find something I am back where I started in 1973 . The few rules the three of us have explained might be as far as I got in 40 years .
Diodes and transistors can be tested cold . Roughly speaking the diode test numbers relate to forward voltage . A red LED might be 1.6 V and a germanium diode 0.25 V , silicon about 0.6V . Blue LED's at 3.3 V usually outside of the meter range . These voltages are exactly what defines a semiconductor , the electrons jumping further to then fall and release for example blue light if 3.3 V . White is impossible as a single diode , it is ultraviolet converted to white as in florescent tubes ( 4.5 V ) . As one PCB works and the other not the readings although not the same as powered ( hot ) should be consistent . One thing to look for is PCB whiskers . That is when a PCB hasn't had enough time to etch or is using depleted chemicals .
Earth/ground will make or brake any amplifier . All amplifiers have poor grounding ( yes ) . Most can be made acceptable or even good . I would bet you anything that 1 year spent with a spectrum analyzer will transform most amplifiers . Musical Fidelity say one of their amplifiers improved by earthing alone . They go on to say the sound is considerably different as are the measurements . This is exactly like Formula One racing . Mostly the same parts with very different outcomes . Unfortunately this can not be taught . All I will say is if hum is minimal it must be about right . This is why a Naim Clone is never a Naim Clone . Sometimes one type of hum sounds nicer even though it scores worse in dB's . It might have more of 50 and 100 Hz ( 60/120 ) , but nothing after that . So - 80 dB 50/100 might be better than -90 dB 350 Hz to 950 Hz . This is a typical figure from distorted mains waveforms . Sometimes rotating the mains transformer will help . Ears say a more melodious hum which actually sounds quieter as our ears do not hear 50 as easily as 950 Hz . This is true even if we have big speakers . Doubtless a gross simplification . The rest takes forever to learn and explain . It is a bit like teaching the piano . Worth trying at the transformer trick is as significant as playing the Moonlight Sonata . Relatively easy for the reward it gives .
BTW . A friend asked Tiger Transformers in Peterborough UK to make a Naim clone transformer for the look . They did and I am very happy with it . The cloning was the look mostly .
I have to say every time I fault find something I am back where I started in 1973 . The few rules the three of us have explained might be as far as I got in 40 years .
Diodes and transistors can be tested cold . Roughly speaking the diode test numbers relate to forward voltage . A red LED might be 1.6 V and a germanium diode 0.25 V , silicon about 0.6V . Blue LED's at 3.3 V usually outside of the meter range . These voltages are exactly what defines a semiconductor , the electrons jumping further to then fall and release for example blue light if 3.3 V . White is impossible as a single diode , it is ultraviolet converted to white as in florescent tubes ( 4.5 V ) . As one PCB works and the other not the readings although not the same as powered ( hot ) should be consistent . One thing to look for is PCB whiskers . That is when a PCB hasn't had enough time to etch or is using depleted chemicals .
Earth/ground will make or brake any amplifier . All amplifiers have poor grounding ( yes ) . Most can be made acceptable or even good . I would bet you anything that 1 year spent with a spectrum analyzer will transform most amplifiers . Musical Fidelity say one of their amplifiers improved by earthing alone . They go on to say the sound is considerably different as are the measurements . This is exactly like Formula One racing . Mostly the same parts with very different outcomes . Unfortunately this can not be taught . All I will say is if hum is minimal it must be about right . This is why a Naim Clone is never a Naim Clone . Sometimes one type of hum sounds nicer even though it scores worse in dB's . It might have more of 50 and 100 Hz ( 60/120 ) , but nothing after that . So - 80 dB 50/100 might be better than -90 dB 350 Hz to 950 Hz . This is a typical figure from distorted mains waveforms . Sometimes rotating the mains transformer will help . Ears say a more melodious hum which actually sounds quieter as our ears do not hear 50 as easily as 950 Hz . This is true even if we have big speakers . Doubtless a gross simplification . The rest takes forever to learn and explain . It is a bit like teaching the piano . Worth trying at the transformer trick is as significant as playing the Moonlight Sonata . Relatively easy for the reward it gives .
BTW . A friend asked Tiger Transformers in Peterborough UK to make a Naim clone transformer for the look . They did and I am very happy with it . The cloning was the look mostly .
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