I have a v1 NAIT that has suddenly developed a soft crackle in the output at power on. This occurs immediately (before the mute circuit goes off), is independent of an unaffected by the volume control, and comes from both channels. The crackle disappears eventually, usually in a few seconds, sometimes in minutes, sometimes almost immediately.
This is a daily use amp and was apparently professionally serviced/recapped 2-3 years back by a former owner. I can't find a schematic for the v1 NAIT online anywhere and although it's clear from the symptoms that something must be affecting the power amp section in both channels (thus maybe in the power supply?), beyond doing capacitor swaps I'm not super duper experienced and I'm not really sure where to probe, esp without a schematic. Does anyone have leads or suggestions? Do these symptoms ring any bells?
Thanks!
This is a daily use amp and was apparently professionally serviced/recapped 2-3 years back by a former owner. I can't find a schematic for the v1 NAIT online anywhere and although it's clear from the symptoms that something must be affecting the power amp section in both channels (thus maybe in the power supply?), beyond doing capacitor swaps I'm not super duper experienced and I'm not really sure where to probe, esp without a schematic. Does anyone have leads or suggestions? Do these symptoms ring any bells?
Thanks!
.....bad contact in the on-off switch (clean it, contact spray,.......)
.....a broken/bad soldering point, perhaps around the on-off switch or in the
power supply or sowhat.......
.....a broken/bad soldering point, perhaps around the on-off switch or in the
power supply or sowhat.......
And does it still do that when you disconnect everything except the power to the Naim ---if yes I would agree with MJF that its likely to be a high resistance soldered connection , usually in the output devices .
If it takes longer than usual for the mute to come off then I would agree that the on/off switch has dirty contacts.
Its Naim policy that Naim amplifiers should be permanently left switched on --Nat 3 the on/off switch was moved to the back to emphasize this as its inclined to sound "harsh " until the optimum temperature is reached ( as per Naim ) .
If it takes longer than usual for the mute to come off then I would agree that the on/off switch has dirty contacts.
Its Naim policy that Naim amplifiers should be permanently left switched on --Nat 3 the on/off switch was moved to the back to emphasize this as its inclined to sound "harsh " until the optimum temperature is reached ( as per Naim ) .
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Thanks to you both for the replies. To Duncan's questions: the issue is indeed the same after disconnecting the audio inputs (leaving only the mains power and speakers connected), and is also independent of any input selection on the front.
The mute delay doesn't seem to be obviously longer that it has typically been, (although if it's fractionally different I might not notice)
It sounds like you are both pointing to a potential solder connection issue-- when you say "output devices" what is it that you're referring to here?
(Also is there a schematic anywhere out there on this unit? I'm a bit puzzled to have come up short on one.)
Thanks.
The mute delay doesn't seem to be obviously longer that it has typically been, (although if it's fractionally different I might not notice)
It sounds like you are both pointing to a potential solder connection issue-- when you say "output devices" what is it that you're referring to here?
(Also is there a schematic anywhere out there on this unit? I'm a bit puzzled to have come up short on one.)
Thanks.
"Output devices " == in this case the BJT,s - bipolar junction transistors that connect the last stage of the amplifier to the loudspeakers - IE- the heaviest current devices in the signal path.
You are not alone in looking for a schematic , its been a sore point for a long time --AFAIK its practically "unobtanium " , all the same I will continue looking.
When high current is applied to a soldered joint with a low resistance but not a complete short circuit ( badly soldered joint ) heat is generated ,this heat completes the circuit reducing by expansion the resistance of the soldered connection and so making a complete contact with the circuit.
IF --this is the case re-flow the output devices soldered contacts.
You are not alone in looking for a schematic , its been a sore point for a long time --AFAIK its practically "unobtanium " , all the same I will continue looking.
When high current is applied to a soldered joint with a low resistance but not a complete short circuit ( badly soldered joint ) heat is generated ,this heat completes the circuit reducing by expansion the resistance of the soldered connection and so making a complete contact with the circuit.
IF --this is the case re-flow the output devices soldered contacts.
Duncan (et al): Thanks for the clarification. Here's the update:
I opened it up and worked some Deoxit into all the switches (and the volume pot), and so far, actually to my amazement, it seems to have mitigated the issue.
While in there I considered reflowing the solder on the transistors for good measure but then I realized that it wouldn't really make sense to be an issue that was solved by heating up/powering on the board for a period of time, because even after being on and quiet for a good while the crackle would come back when switching the unit off and then on again immediately.
I'm only cautiously optimistic-- it's possible the jostling around was as effective as the Deoxit so we'll see. I suppose buildup of oxide plus frequent on/off switching could have provoked small arcing? No idea how to think about the problem.
Duncan: for my curiosity, are the output transistors you referred to likely to be the four that are bound into the heat sink structure next to the toroid?
Thanks.
I opened it up and worked some Deoxit into all the switches (and the volume pot), and so far, actually to my amazement, it seems to have mitigated the issue.
While in there I considered reflowing the solder on the transistors for good measure but then I realized that it wouldn't really make sense to be an issue that was solved by heating up/powering on the board for a period of time, because even after being on and quiet for a good while the crackle would come back when switching the unit off and then on again immediately.
I'm only cautiously optimistic-- it's possible the jostling around was as effective as the Deoxit so we'll see. I suppose buildup of oxide plus frequent on/off switching could have provoked small arcing? No idea how to think about the problem.
Duncan: for my curiosity, are the output transistors you referred to likely to be the four that are bound into the heat sink structure next to the toroid?
Thanks.
If the crackle is audible on both channels I would look around the power side for dry joints or a bad power switch. Unless you have dry joints on output devices on both channels - would seem odd they both crackle (if that is the case).
You said Deoxit on the switches help, did you do the power switch?
My Rotel amp would crackle on several channels closest to the power switch, turned out out to be dry joints on a mains switch, which were arcing as a result causing the crackling.
You said Deoxit on the switches help, did you do the power switch?
My Rotel amp would crackle on several channels closest to the power switch, turned out out to be dry joints on a mains switch, which were arcing as a result causing the crackling.
That sounds like them they should be connected directly to the output loudspeaker posts .
You wont find any Zobel network Naim didn't believe in them and I remember at the time Naim,s take on a MM input caused a bit of comment on EW as it used multiple BJT,s to achieve a very low noise floor ( remember we are talking way back in the "old days " here ).
Naim advertised the Nat without giving out any specs as they said---quote- "the amp speaks for itself " .
No large number of IC,s - discrete ruled the day .
Not an amp for the classical music lover - but MUSICAL for other genres , you will gather I like the engineering philosophy , not perfect but perfectly listenable .
Persevere with it , its worth it.
You wont find any Zobel network Naim didn't believe in them and I remember at the time Naim,s take on a MM input caused a bit of comment on EW as it used multiple BJT,s to achieve a very low noise floor ( remember we are talking way back in the "old days " here ).
Naim advertised the Nat without giving out any specs as they said---quote- "the amp speaks for itself " .
No large number of IC,s - discrete ruled the day .
Not an amp for the classical music lover - but MUSICAL for other genres , you will gather I like the engineering philosophy , not perfect but perfectly listenable .
Persevere with it , its worth it.
Naim push all their kit (or used to) to the edge of stability, because it sounds better! (Even if it can oscillate under the wrong load, but what does that matter...)
LOW capacitance cables required Ohdsp Naim,s own make , in any case power supply up-rating was an added benefit.
No problem driving Quad Electrostatics and unusual loudspeaker loads
.
Okay it didn't quite do justice to large speakers but its easy to criticize in hindsight , I could do that with many "beloved " amps of the past era.
No problem driving Quad Electrostatics and unusual loudspeaker loads
.
Okay it didn't quite do justice to large speakers but its easy to criticize in hindsight , I could do that with many "beloved " amps of the past era.
Your talking about the DIN cable not the loudspeaker cable ( Naim,s website ) .
The mechanical connection on a DIN plug/socket is a "cutting " interference fit rather than the inferior RCA socket which is a contact fit , you need gold plated RCA sockets /plugs to keep a good contact.
I haven't heard of this "shaking " the cable comment but if it came directly from Naim can you quote who-where-what so that I can check it out.
The mechanical connection on a DIN plug/socket is a "cutting " interference fit rather than the inferior RCA socket which is a contact fit , you need gold plated RCA sockets /plugs to keep a good contact.
I haven't heard of this "shaking " the cable comment but if it came directly from Naim can you quote who-where-what so that I can check it out.
If you have ever toured there you might have seen it, or just find the references to it on the website.
Sorry I don't "tour " websites only if checking out data , I don't remember this being brought up on EW/WW by any of the engineers .
But just to keep you happy I have just checked out your comment on "shaking " and 3 audio websites all refer back to DIN cable connections not loudspeaker cables.
But just to keep you happy I have just checked out your comment on "shaking " and 3 audio websites all refer back to DIN cable connections not loudspeaker cables.