I did some simulaions with different resistor and transistors previously I can't remember exactly what the trends were. But it looks like your adjustment is not coarse enough.
If you are still having trouble after you try a different device I will run the simulations again.
I would do it now however I have to get ready for work.
If you are still having trouble after you try a different device I will run the simulations again.
I would do it now however I have to get ready for work.
Embarrassed
Hi all
I have found out what was wrong with my amp boards - absolutely nothing at all. I personally blame the builder for not engaging brain - obviously a complete dunce.
What I did (after checking orientation/tracks/dry joints etc) was to change one Q5 (BC546 for TIP41) and try again, this time the bias adjustment worked - I used inline measuring rather than across R29/30.
I then rechecked the adjustment on the other board (with BC546) and it also worked fine.
The actual problem was that I was not turning TR1 far enough, for most of the turns nothing much happens - I suppose you must get to the critical point where Q5 turns on.
I have set them both to 30mA and they are pleasantly stable, actually the board with the BC546 seems to be just that bit more stable in terms of quiescent current.
Just finishing off the (temp) fitting into a suitable case and then it is time to try it out for real.
Graham
Hi all
I have found out what was wrong with my amp boards - absolutely nothing at all. I personally blame the builder for not engaging brain - obviously a complete dunce.
What I did (after checking orientation/tracks/dry joints etc) was to change one Q5 (BC546 for TIP41) and try again, this time the bias adjustment worked - I used inline measuring rather than across R29/30.
I then rechecked the adjustment on the other board (with BC546) and it also worked fine.
The actual problem was that I was not turning TR1 far enough, for most of the turns nothing much happens - I suppose you must get to the critical point where Q5 turns on.
I have set them both to 30mA and they are pleasantly stable, actually the board with the BC546 seems to be just that bit more stable in terms of quiescent current.
Just finishing off the (temp) fitting into a suitable case and then it is time to try it out for real.
Graham
Hi
A couple of quick pics showing the 'installation'
Looks a bit like a Borg amp.
http://people.exeter.ac.uk/gar202/p...kBoxAmp/Phase_2_Naim140/TS_NaimNAP140_005.jpg
http://people.exeter.ac.uk/gar202/p...kBoxAmp/Phase_2_Naim140/TS_NaimNAP140_008.jpg
Anyway it has been working for a few hours with no probs, so fingers crossed it will still be working tomorrow.
Graham
A couple of quick pics showing the 'installation'
Looks a bit like a Borg amp.
http://people.exeter.ac.uk/gar202/p...kBoxAmp/Phase_2_Naim140/TS_NaimNAP140_005.jpg
http://people.exeter.ac.uk/gar202/p...kBoxAmp/Phase_2_Naim140/TS_NaimNAP140_008.jpg
Anyway it has been working for a few hours with no probs, so fingers crossed it will still be working tomorrow.
Graham
Hi
I started building the case in about 1989, can't rush these things....
It was built for different amp boards, (hence the strange angle of these), originally from a Crimson Elektric 520, the final version will have some boards based on the A&R A60 power amp section - when I finally finish the layout that is.
The sound is really very good - considering I am using some speakers from a Pure DMX50 mini system (actually not that bad - they have Wharfedale Diamond bass units) and only have mp3s via pc or ipod (I'm away from home). The pre-amp is Velleman valve job.
Given the less than inspiring source they sound clear, good stereo, lots of bass (perhaps a bit too much).
I am really impressed, they will eventually end up as mono units so then they should be even better.
Graham
I started building the case in about 1989, can't rush these things....
It was built for different amp boards, (hence the strange angle of these), originally from a Crimson Elektric 520, the final version will have some boards based on the A&R A60 power amp section - when I finally finish the layout that is.
The sound is really very good - considering I am using some speakers from a Pure DMX50 mini system (actually not that bad - they have Wharfedale Diamond bass units) and only have mp3s via pc or ipod (I'm away from home). The pre-amp is Velleman valve job.
Given the less than inspiring source they sound clear, good stereo, lots of bass (perhaps a bit too much).
I am really impressed, they will eventually end up as mono units so then they should be even better.
Graham
Yes it is great see others successfully complete their clones with excellent results.
I have completed one channel of mine and hope to hook it up to a CRO next week.
I haven't bothered with the zobel network mod at this stage. I'll see how stable it runs first without it.
Do any of you guys have recommendations for testing amplifier stability?
I am guessing runing a square wave into a resistive load with a capacitor in parrallel.
What value for the cap?
What frequency of square wave?
Also if anyone can provide a link with further information that would be great also.
I have completed one channel of mine and hope to hook it up to a CRO next week.
I haven't bothered with the zobel network mod at this stage. I'll see how stable it runs first without it.
Do any of you guys have recommendations for testing amplifier stability?
I am guessing runing a square wave into a resistive load with a capacitor in parrallel.
What value for the cap?
What frequency of square wave?
Also if anyone can provide a link with further information that would be great also.
Hi guys,
Firstly, I have been building several kits from Gigawork too, thanks to lots of mods and guidance from this thread!
One of the kit is used to rebuild an old sansui amplifier. For personal reason I want to maintain the existing transformer but however, I ended up having +/-53v DC power supply. The input transistors (BC550) are not rated for this higher voltage.
So I'm wondering if I can modify the circuit as per the attachment. Can I change the 330R resistors to a higher value to drop the rail voltage? If yes, what is a suitable value to replace here? Will this effect the feedback orr something? (Im not an EE so need help with calculations)
Thanks in advance
Firstly, I have been building several kits from Gigawork too, thanks to lots of mods and guidance from this thread!
One of the kit is used to rebuild an old sansui amplifier. For personal reason I want to maintain the existing transformer but however, I ended up having +/-53v DC power supply. The input transistors (BC550) are not rated for this higher voltage.
So I'm wondering if I can modify the circuit as per the attachment. Can I change the 330R resistors to a higher value to drop the rail voltage? If yes, what is a suitable value to replace here? Will this effect the feedback orr something? (Im not an EE so need help with calculations)
Thanks in advance
Attachments
Hi I am interested in these, can we have some consensus regarding the best.
output and driver transistors to go for?
its not terribly easy to find which would be best.
Slightly off topic, are there any ideas if this circuit would perform better as a fully complimentary output stage?
Its VERY interesting that naim have never changed it at all, but from looking at the very latest amps, they have a few extra transistors, I think the input stage has been altered a little to a cascode or a current mirror. But the output stage is STILL sacrosanct.
I am VERY VERY familiar with the topoligies and schematics of many commercial amplifiers.
Naim, to perhaps more foreign people who aren't really versed in the UK hifi market are generally seen as premium commercial products, quite expensive, and viewed by their followers as almost a religion. There is a historical reason for this.
Generally, British 1970/80s designs are minimalist, and fairly simple, unelaborate, but use very good pcb's, and quite heavy duty power supplies.
Naim hifi, are also renowed for their sources, the tuners and cd players are pricy too, and generally very well thought of by reviewers. the speakers, are generally for naim users though, again they have a distinctive sound.
The sound of the amplifiers, I think is LARGELY coloured by the preamplifiers, which are VERY simple single ended stages. With overkill power supplies.
When used together, they really do have a distinctive sound that none have been able to match, the tempo of the music is so punchy and bouncy, rhythms and all that, totally unique. Once you have heard one, you either love or hate, if you love, nothing else will ever do.
I did a very interesting compoarison with an
alesis ra100 old style
John linsley hood Mosfet 80 watter with complex discrete regulator, very good circuit
Michell alecto, 130 watt mosfet monoblocs, borbely design,
Pioneer £4000 all class A amplifier, VERY sexy indeed. VERY expensive. Fascinating circuit A-09 Very posh.
And naim NAP 250 power amplifier
I ranked them in order of sound imo
Naim top
Michell 2nd
Pioneer 3rd
Alesis 4th.
JLH last, sounded very poor, really bad disappoinment, such a great circuit.
Naim also manage to preserve very nice instrumental tone, better than I have heard many amplifiers.
They don't image or soundstage terribly well, but its just the hypnotic rhythms that get you.
to be honest, I think a good way to view them is this, against japanese equipment, that is very well engineered, the british bespoke stuff is quite extensively researched, and is probably equivalent to a handmade motor car vs., say, a Honda, Toyota, or Ford, say, which is mass market, rather like japenese hifi.
You don't think you are getting a lot, the price is very dear, but the quality is in the engineering.
Its only a rough analogy, I know there is far more to japanese equipment.
output and driver transistors to go for?
its not terribly easy to find which would be best.
Slightly off topic, are there any ideas if this circuit would perform better as a fully complimentary output stage?
Its VERY interesting that naim have never changed it at all, but from looking at the very latest amps, they have a few extra transistors, I think the input stage has been altered a little to a cascode or a current mirror. But the output stage is STILL sacrosanct.
I am VERY VERY familiar with the topoligies and schematics of many commercial amplifiers.
Naim, to perhaps more foreign people who aren't really versed in the UK hifi market are generally seen as premium commercial products, quite expensive, and viewed by their followers as almost a religion. There is a historical reason for this.
Generally, British 1970/80s designs are minimalist, and fairly simple, unelaborate, but use very good pcb's, and quite heavy duty power supplies.
Naim hifi, are also renowed for their sources, the tuners and cd players are pricy too, and generally very well thought of by reviewers. the speakers, are generally for naim users though, again they have a distinctive sound.
The sound of the amplifiers, I think is LARGELY coloured by the preamplifiers, which are VERY simple single ended stages. With overkill power supplies.
When used together, they really do have a distinctive sound that none have been able to match, the tempo of the music is so punchy and bouncy, rhythms and all that, totally unique. Once you have heard one, you either love or hate, if you love, nothing else will ever do.
I did a very interesting compoarison with an
alesis ra100 old style
John linsley hood Mosfet 80 watter with complex discrete regulator, very good circuit
Michell alecto, 130 watt mosfet monoblocs, borbely design,
Pioneer £4000 all class A amplifier, VERY sexy indeed. VERY expensive. Fascinating circuit A-09 Very posh.
And naim NAP 250 power amplifier
I ranked them in order of sound imo
Naim top
Michell 2nd
Pioneer 3rd
Alesis 4th.
JLH last, sounded very poor, really bad disappoinment, such a great circuit.
Naim also manage to preserve very nice instrumental tone, better than I have heard many amplifiers.
They don't image or soundstage terribly well, but its just the hypnotic rhythms that get you.
to be honest, I think a good way to view them is this, against japanese equipment, that is very well engineered, the british bespoke stuff is quite extensively researched, and is probably equivalent to a handmade motor car vs., say, a Honda, Toyota, or Ford, say, which is mass market, rather like japenese hifi.
You don't think you are getting a lot, the price is very dear, but the quality is in the engineering.
Its only a rough analogy, I know there is far more to japanese equipment.
hi I had the 2 circuit board, with large discrete active regulators.
I didn't like it at all, and I wasn't biased, I had my heart set on one for a while, it was well built, and a really well opimised circuit, ie decent differential pair and voltage amplifier.
I dunno why, but it just didn't sound good at all to me.
things are probably fine to a certain extent in isolation, but its a totally different kettle of fish when you start doing a to b's simultaneously.
I expected the alesis to do better, it outdid significantly a marantz ki66 signature in a shop,much to the surprise of the assitant,
the $6-8000 USD pioneer A-09, paid about equiv. $1700 for it, wasn't bad, but a big disappointment for the cash, fine, but can be bettered.
that's it, number 3 on my comparison
http://www.zerogain.com/forum/showthread.php?t=19762
thos are the number 2s, 130 watt mosfets...very valvey, but neutral at the same time with it.
http://www.affordablevalvecompany.com/alecto.jpg
the naim lost a lot of its character when ran via a different preamp, but ended up still the best sounding, its quite natural tonal colours, and none too clinical being an older circuit design, less developed, so perhaps more 'colour' and character due to measurement/design imperfections.
just did it for me, I ain't a naim nut, but I do like the sound. I was hoping for the michells to win, so I was biased in a way, but it didn't in the end affect my judgement, I suppose the ancilliaries, ie cd player, preamp, room and speakers all had an influence, so in a different setting the results could be different, with other pairs of prefereces, too, ie ears.
I didn't like it at all, and I wasn't biased, I had my heart set on one for a while, it was well built, and a really well opimised circuit, ie decent differential pair and voltage amplifier.
I dunno why, but it just didn't sound good at all to me.
things are probably fine to a certain extent in isolation, but its a totally different kettle of fish when you start doing a to b's simultaneously.
I expected the alesis to do better, it outdid significantly a marantz ki66 signature in a shop,much to the surprise of the assitant,
the $6-8000 USD pioneer A-09, paid about equiv. $1700 for it, wasn't bad, but a big disappointment for the cash, fine, but can be bettered.
that's it, number 3 on my comparison
http://www.zerogain.com/forum/showthread.php?t=19762
thos are the number 2s, 130 watt mosfets...very valvey, but neutral at the same time with it.
http://www.affordablevalvecompany.com/alecto.jpg
the naim lost a lot of its character when ran via a different preamp, but ended up still the best sounding, its quite natural tonal colours, and none too clinical being an older circuit design, less developed, so perhaps more 'colour' and character due to measurement/design imperfections.
just did it for me, I ain't a naim nut, but I do like the sound. I was hoping for the michells to win, so I was biased in a way, but it didn't in the end affect my judgement, I suppose the ancilliaries, ie cd player, preamp, room and speakers all had an influence, so in a different setting the results could be different, with other pairs of prefereces, too, ie ears.
Nap 140-C Amp clone
Hi all, I'm a newbie who got "bit by the bug". Enjoyed so much this thread that decided to purchase Nap 140-C clone bare boards on ebay (the longer ones) and build my first amp. Parts were selected separately picking from this thread suggestions. Did my homework studying and reading carefully other diyers' experiences on this thread. I'm at my third board and still can't get it to work!! Was hoping someone could help me troubleshoot, maybe posting some of the approximate readings that I should expect at the different stages. I have a 250 VA 30-0-30 toroid, dual rectification with 8x4700uf (4 each rail) smoothing caps. Don't have variable bench power so I set lamp bulb in series with mains (only lights up briefly at power up), have 2x10 ohm 10 watt resistor at main supply and 2x100ohm at +/- pcb supply terminals to make sure I get warned if there is a short. Input ground, speaker, pcb ground all go to the common point on the caps. With no input/no output load everything seems fine at power up, current set to suggested minimum of 10ma (2.2mv across emitter resistor r29), negative rail showing the same reading. Output DC offset around 12mv, trimpot works, resistance across r17 is around 650ohm. All transistors/caps checked for proper forward bias and correct alignment. Have MJL3281A output transistors mated with MJE15032/3 drivers (as per Neil McBride). What happens is that when I finally attach a speaker (no input yet), the "warning" 100ohm resistor on the negative supply side overheats with smoke, forcing me to power off (no time to check music). Also tried with quiescent current set at minimum level, 1.4mv across r29, or 6.4ma (275mv across base/emitter 100ohm resistor r26) which should give hardly no current at all to power transistor with the same result. Any idea what is going on? Thank you very much for any help/suggestion.
Hi all, I'm a newbie who got "bit by the bug". Enjoyed so much this thread that decided to purchase Nap 140-C clone bare boards on ebay (the longer ones) and build my first amp. Parts were selected separately picking from this thread suggestions. Did my homework studying and reading carefully other diyers' experiences on this thread. I'm at my third board and still can't get it to work!! Was hoping someone could help me troubleshoot, maybe posting some of the approximate readings that I should expect at the different stages. I have a 250 VA 30-0-30 toroid, dual rectification with 8x4700uf (4 each rail) smoothing caps. Don't have variable bench power so I set lamp bulb in series with mains (only lights up briefly at power up), have 2x10 ohm 10 watt resistor at main supply and 2x100ohm at +/- pcb supply terminals to make sure I get warned if there is a short. Input ground, speaker, pcb ground all go to the common point on the caps. With no input/no output load everything seems fine at power up, current set to suggested minimum of 10ma (2.2mv across emitter resistor r29), negative rail showing the same reading. Output DC offset around 12mv, trimpot works, resistance across r17 is around 650ohm. All transistors/caps checked for proper forward bias and correct alignment. Have MJL3281A output transistors mated with MJE15032/3 drivers (as per Neil McBride). What happens is that when I finally attach a speaker (no input yet), the "warning" 100ohm resistor on the negative supply side overheats with smoke, forcing me to power off (no time to check music). Also tried with quiescent current set at minimum level, 1.4mv across r29, or 6.4ma (275mv across base/emitter 100ohm resistor r26) which should give hardly no current at all to power transistor with the same result. Any idea what is going on? Thank you very much for any help/suggestion.