Nelson Pass Amp Camp Amp #1 questions

[MrRadish]

Hi all, I hope this is the right place to ask this. I bought a secondhand DIY Camp Amp #1 a while ago and recently tried using linear power supplies with it. I'm getting some odd results though and would like to run this past those of you who actually know what you're doing with electronics ('cos I sure don't). This is just plugging stuff in, no actual DIY.

1. Running with the original (19v 4.7A) SMPS supplies the amp sounds great and I have no issues.
2. When I plug both linear supplies in (Maplin test bench supplies with front meters) turning up the voltage on one also turns up the voltage on the other. If I reverse the wires on both the same thing happens. If I alternate so red to black on one and red to red on the other the ammeter hits the end stop hard and is presumably a short (yes, I actually tried that...)
3. If I just have one PSU switched on or plugged in then both channels play normally. The same is true when using the SMPS.
4. If I run the LPSU at 12v the power consumption is about 200mA and everything works. If I turn the voltage up towards 19v the ammeter start to run away ahead of me and hits the end stop (3A). I switch it off at that point so don't know what happens next.
5. Using one or both SMPS the power consumption according to my AC regenerator doesn't change: it's pretty consistently 57 watts above that for my sources, with a little more after first switch on.
6. My first experiment with the LPSU had connectors with metal ends. I've now switched to connectors with plastic ends but I get the same results.

My questions:
Is it safe to have two PSU plugged in and switched on at the same time. It's obviously worked fine for at least three owners using the SMPS, so I'm asking theoretically. I think the amp sounds a little weaker with one, but I may be imagining it.
Is it safe to run the amp at 12v, or will that damage anything?
How many amps should the amp be fed at 19v if running from one supply? I have a 19v LPSU that can put out 5 or 6 amps I believe, but I'm not willing to try it unless that should be fine (it cost more than the Maplin supplies).

Any comments or abuse welcome. :) I don't expect a warranty with a DIY amp so I'm not bothered (and being able to run it off one PSU is actually a bonus), I just want to make sure it's electrically safe.

[Barry]

Hi all, I hope this is the right place to ask this. I bought a secondhand DIY Camp Amp #1 a while ago and recently tried using linear power supplies with it. I'm getting some odd results though and would like to run this past those of you who actually know what you're doing with electronics ('cos I sure don't). This is just plugging stuff in, no actual DIY.

1. Running with the original (19v 4.7A) SMPS supplies the amp sounds great and I have no issues.
2. When I plug both linear supplies in (Maplin test bench supplies with front meters) turning up the voltage on one also turns up the voltage on the other. If I reverse the wires on both the same thing happens. If I alternate so red to black on one and red to red on the other the ammeter hits the end stop hard and is presumably a short (yes, I actually tried that...)
3. If I just have one PSU switched on or plugged in then both channels play normally. The same is true when using the SMPS.
4. If I run the LPSU at 12v the power consumption is about 200mA and everything works. If I turn the voltage up towards 19v the ammeter start to run away ahead of me and hits the end stop (3A). I switch it off at that point so don't know what happens next.
5. Using one or both SMPS the power consumption according to my AC regenerator doesn't change: it's pretty consistently 57 watts above that for my sources, with a little more after first switch on.
6. My first experiment with the LPSU had connectors with metal ends. I've now switched to connectors with plastic ends but I get the same results.

My questions:
Is it safe to have two PSU plugged in and switched on at the same time. It's obviously worked fine for at least three owners using the SMPS, so I'm asking theoretically. I think the amp sounds a little weaker with one, but I may be imagining it.
Is it safe to run the amp at 12v, or will that damage anything?
How many amps should the amp be fed at 19v if running from one supply? I have a 19v LPSU that can put out 5 or 6 amps I believe, but I'm not willing to try it unless that should be fine (it cost more than the Maplin supplies).

Any comments or abuse welcome. :) I don't expect a warranty with a DIY amp so I'm not bothered (and being able to run it off one PSU is actually a bonus), I just want to make sure it's electrically safe.

Does your linear power supply have sufficient capacity? You say when using a SMPS your AC regenerator shows a power consumption of 57W. With a supply voltage of 19V, a power consumption of 57W implies a current of exactly 3A - the limit of the ammeter scale on the LPSU.

[MrRadish]

Does your linear power supply have sufficient capacity? You say when using a SMPS your AC regenerator shows a power consumption of 57W. With a supply voltage of 19V, a power consumption of 57W implies a current of exactly 3A - the limit of the ammeter scale on the LPSU.

I don't believe the Maplin ones do, I think they're rated up to 2.5A (although I'm not sure at what Voltage that was listed). I was only using those as I had two identical ones, so I'll switch to something else if it's just 3A overall. Does using two PSU (presumably in parallel) double the current output so they provide 1.5A each, or does it not work like that?

[Barry]

I don't believe the Maplin ones do, I think they're rated up to 2.5A (although I'm not sure at what Voltage that was listed). I was only using those as I had two identical ones, so I'll switch to something else if it's just 3A overall. Does using two PSU (presumably in parallel) double the current output so they provide 1.5A each, or does it not work like that?

No, I don't think it is quite as simple as that. Perhaps a member who is also a power supply expert can help?

[struth]

No its not that simple, but can be done. Jez might know the correct method.. i would be inclined to just get a bigger linear supply

[Arkless Electronics]

It sounds as if you will need a bigger power supply... but just one! Trying to put voltage sources in parallel will usually end in tears... Get a single supply of 6A or more. Or are you trying to run it with a PSU per channel? This should work...
Don't short power supplies etc like you did!:eek::stalks: If using PSU's without short and overload protection you would have killed them instantly!!

[Arkless Electronics]

Oh and if there are 1000's of uF of caps already fitted in the amp as smoothing caps I would expect little difference from changing PSU's...

[MrRadish]

It sounds as if you will need a bigger power supply... but just one! Trying to put voltage sources in parallel will usually end in tears... Get a single supply of 6A or more. Or are you trying to run it with a PSU per channel? This should work...
Don't short power supplies etc like you did!:eek::stalks: If using PSU's without short and overload protection you would have killed them instantly!!

The Camp Amp is supposed to be dual mono with two PSU, but this one has been built into one chassis. That should be fine and they should still be dual mono, but clearly the PSU connectors are linked in some way (maybe at the power switch). The Maplin test bench supplies are pretty resilient (thankfully) but not quite powerful enough, so as we've worked out its 3A max I'm running it off a single HDPlex PSU instead. I'm not sure it's an improvement, but that may be because I've not used this DC cable before so I'll give it a while before deciding what to do next. The LPSU is slightly noisier through the speakers than the SMPS though, with the cheap SMPS being silent.

[Arkless Electronics]

Well obviously the DC cable is critical:D

There should be no noise from a good LPSU running correctly. If you know how to then separate the power connections in the amp so you you have two completely independent channels. The Maplins supplies should handle one channel each then.

[MrRadish]

Well obviously the DC cable is critical:D

There should be no noise from a good LPSU running correctly. If you know how to then separate the power connections in the amp so you you have two completely independent channels. The Maplins supplies should handle one channel each then.

I might be able to handle that, but I'll leave it running as it is for now. It's consuming 87 watts at the mains, which is to be expected being a linear supply, but I need to keep a check on how hot the PSU gets as it's pretty toasty right now.

[Arkless Electronics]

I had a quick look at the amp camp thingy.... there seems to be no big caps and so the PSU will be fairly critical to the sound. Also although I was avin a larf about the DC cable this does make it more critical! It needs to be thick... 30A or more for best results.

And he's nicked my idea!! I came up with an idea about 20 years ago where I would design an amp for easy self build then charge folk to come and build them together with my help.. another part of the plan was my top chef hi fi nut mate would do amazing food on the evening and help me with the "students" during the day... We had a think about it.. for about 1 minute... before deciding it could work great... if we had loads of money to hire a venue, put the kits together and get insured for it.... :eek:

[danilo]

IF you are happy with the ACA's sounds.
Then simply buy /build this: It Works 'as advertised' Period. build it dual or Mono.. lotsa pointless choices. Cheapish too;)
I certainly wouldn't dick around with something that's likely 'goofy' to start with.
http://www.diyaudio.com/forums/power-supplies/244788-diyaudio-power-supply-circuit-board-v3-illustrated-build-guide.html
Frankly I'd think about buying another ACA kit from the DiyAudio.com 'shop' ...affordable, dead easy and you know it will be done correctly .. or not :-).

[Arkless Electronics]

IF you are happy with the ACA's sounds.
Then simply buy /build this: It Works 'as advertised' Period. build it dual or Mono.. lotsa pointless choices. Cheapish too;)
I certainly wouldn't dick around with something that's likely 'goofy' to start with.
http://www.diyaudio.com/forums/power-supplies/244788-diyaudio-power-supply-circuit-board-v3-illustrated-build-guide.html
Frankly I'd think about buying another ACA kit from the DiyAudio.com 'shop' ...affordable, dead easy and you know it will be done correctly .. or not :-).

It's a + & - 25V supply and isn't regulated....

[MrRadish]

I had a quick look at the amp camp thingy.... there seems to be no big caps and so the PSU will be fairly critical to the sound. Also although I was avin a larf about the DC cable this does make it more critical! It needs to be thick... 30A or more for best results.

And he's nicked my idea!! I came up with an idea about 20 years ago where I would design an amp for easy self build then charge folk to come and build them together with my help.. another part of the plan was my top chef hi fi nut mate would do amazing food on the evening and help me with the "students" during the day... We had a think about it.. for about 1 minute... before deciding it could work great... if we had loads of money to hire a venue, put the kits together and get insured for it.... :eek:

If you'd thought it through further you could have ditched the hi-fi altogether and had the attendees do their own baking, made a competition out of it, and then then sold the idea to the BBC. :)

[Arkless Electronics]

If you'd thought it through further you could have ditched the hi-fi altogether and had the attendees do their own baking, made a competition out of it, and then then sold the idea to the BBC. :)

Hindsight eh?:lol:

[MrRadish]

IF you are happy with the ACA's sounds.
Then simply buy /build this: It Works 'as advertised' Period. build it dual or Mono.. lotsa pointless choices. Cheapish too;)
I certainly wouldn't dick around with something that's likely 'goofy' to start with.
http://www.diyaudio.com/forums/power-supplies/244788-diyaudio-power-supply-circuit-board-v3-illustrated-build-guide.html
Frankly I'd think about buying another ACA kit from the DiyAudio.com 'shop' ...affordable, dead easy and you know it will be done correctly .. or not :-).

Thanks for the link, but whilst I might have a go at building a Camp Amp to teach myself electronics there's no way I'd touch a PSU project - that would be suicide by DIY. I would like to be able to do that, but I need to get some proper training first.

[walpurgis]

Hindsight eh?:lol:

You need eye's in yer bum for that. :eyebrows:

[danilo]

Right.. that's why Nelson is 'famous' and others are not.
Elegantly simple Pass design A amps don't actually benefit from PSU Regulation.
Many have trod that path.. pointlessly. Old notions persist though.

If there are contrary design opinions, discuss them with Pass ?

[Arkless Electronics]

Right.. that's why Nelson is 'famous' and others are not.
Elegantly simple Pass design A amps don't actually benefit from PSU Regulation.
Many have trod that path.. pointlessly. Old notions persist though.

If there are contrary design opinions, discuss them with Pass ?

Whatever:nocomment:

[montesquieu]

Right.. that's why Nelson is 'famous' and others are not.
Elegantly simple Pass design A amps don't actually benefit from PSU Regulation.
Many have trod that path.. pointlessly. Old notions persist though.

If there are contrary design opinions, discuss them with Pass ?

Er I think the you are looking for the Nelson Pass fanboy / love-in forum ... from memory it's on your side of the pond.

[6L6]

2. When I plug both linear supplies in (Maplin test bench supplies with front meters)

I'd love to see a photo of the front panel of your PSUs. I'd also like to see how you are connecting them to the ACA




My questions:
Is it safe to have two PSU plugged in and switched on at the same time. It's obviously worked fine for at least three owners using the SMPS, so I'm asking theoretically.

Possibly, but it depends on how you are connecting things.


Is it safe to run the amp at 12v, or will that damage anything?

It will be fine at 12V, but your output will be somewhere in the vicinity of 1 watt. And that vicinity will be lower...






How many amps should the amp be fed at 19v if running from one supply? I have a 19v LPSU that can put out 5 or 6 amps I believe, but I'm not willing to try it unless that should be fine (it cost more than the Maplin supplies)

Probably just one.


If you really want to make the ACA sound better, get two 24V laptop PSUs. This will increase the power, give you a couple volts more output swing, and let the amp clip later. The only reason why 24V wasn't originally used was cost, there wasn't a 24V laptop brick available in bulk for the price of the 19V ones supplied.



1. Running with the original (19v 4.7A) SMPS supplies the amp sounds great and I have no issues.

Aha! Problem solved. :) :) :)