idiots guide to amp building

[djftw]

The HCR is an improved version of the Naim regulator boards used in the 250 and 135 amps, designed to power the whole of the amp board, not just the front end.

@Arkless Electronics Jez, would adding the HCR200 boards to my amp address the excessive voltage to the amp boards/low speaker impedance concern we discussed? I have doubts there is room for them in there, but it just occurred to me reading this that it could be an alternative to replacing the transformer that might give a performance lift as well as letting me turn up 4R speakers without worrying too much!

 

[Arkless Electronics]

@Arkless Electronics Jez, would adding the HCR200 boards to my amp address the excessive voltage to the amp boards/low speaker impedance concern we discussed? I have doubts there is room for them in there, but it just occurred to me reading this that it could be an alternative to replacing the transformer that might give a performance lift as well as letting me turn up 4R speakers without worrying too much!

There's not enough room in there! You could need a higher voltage transformer to allow for the regulators as well, depending on the required output power and drop out voltage of the regulators.

 

[djftw]

There's not enough room in there! You could need a higher voltage transformer to allow for the regulators as well, depending on the required output power and drop out voltage of the regulators.

Oh well, it looks like it works with the original Naim reserve capacitors and rectifier from what I can see on Avondale's page, but the cap6s presumably live where the original Naim regulator boards were now...

 

[muchtoofast]

As promised, rear switch pics to fit Modushop Pre Cut Dissipante rear panel: Mouser model number 693-4304.606

2021-03-22_11-35-21 by muchtoofast, on Flickr

2021-03-22_11-34-53 by muchtoofast, on Flickr

Very happy, everything seems to be modular.

 

[piKam]

che tipo di cavo usi per il cablaggio, awg10 / 12/14 ?

 

[muchtoofast]

che tipo di cavo usi per il cablaggio, awg10 / 12/14 ?

Wires by muchtoofast, on Flickr

This for power after the rectification / smoothing cap 6 stage.

 

[Mike Hanson]

This is for power after the rectification / smoothing cap 6 stage.

I've gotten into the habit of doing this with 12AWG, although I suspect 14AWG would probably be fine.

 

[muchtoofast]

I've gotten into the habit of doing this with 12AWG, although I suspect 14AWG would probably be fine.

Yeah, as Mike says, thicker is probably better.

 

[Mike Hanson]

Yeah, as Mike says, thicker is probably better.

With runs this short, I'm unsure that the bigger wire will make a notable difference. However, the small difference in cost makes it an easy decision.

 

[muchtoofast]

From what I can find, for enclosure wiring, at 30 degrees ambient temp:

18AWG is rated at 7A (5.6A on some charts)
14AWG is rated at 20A (15A on some charts)
12AWG is rated at 30A (20A on some charts)

As the ambient temp goes up, current rating changes. Length of cable (which shouldn't matter as these are short runs), insulation type and whether the cable is on it's own or in a bunch, all have an effect of the current carrying capacity.

After further research, at not much more cost, from now on, I think I'll be going for 14AWG+ to be on the safe side Thanks Mike!

 

[Mike Hanson]

I know that 30A seems like a lot, but I wonder how much current is required when a huge musical transient hits. If there's any chance that a smallish wire could restrict that, I would rather avoid it.

 

[muchtoofast]

I know that 30A seems like a lot, but I wonder how much current is required when a huge musical transient hits. If there's any chance that a smallish wire could restrict that, I would rather avoid it.

I'm with you on that one! Any excuse to satisfy my 'I might be missing something if I don't put a bigger one in' obsession, is a good one. I've just got to find a crimp tool that can crimp 12AWG now. Most specify 16AWG max

 

[Mike Hanson]

I've just got to find a crimp tool that can crimp 12AWG now. Most specify 16AWG max

I've got three different crimping tools, for the many different spade connectors. The one that does the 12AWG plugs is a monster.

 

[muchtoofast]

I've got three different crimping tools, for the many different spade connectors. The one that does the 12AWG plugs is a monster.

I bet it is!

 

[muchtoofast]

I recieved my transformer from CW yesterday, plugged it in and voltages seem correct. Difficult to guage what is normal for mechanical hum, being new at this

2021-04-17_01-58-58 by muchtoofast, on Flickr

 

[muchtoofast]

Is +/- 52v too much for the NCC220s?

 

[say it as it is]

How much was your transformer and erase spec is it?

 

[muchtoofast]

£185 inc delivery from Terry at Canterbury Windings. Lovely transformer. Took 5 weeks, but worth it as its a magical solution for going forward with the 42V smaller secondaries for regulation later on.


Model Number TM276B
Continuous power rating: 812VA
Primary: 0-240V @ 50Hz
Electrostatic screen
Secondary 1: 35-0-35V @ 5A rms
Secondary 2: 35-0-35V @ 5A rms
Secondary 3: 42-0-42V @ 0.7A rms
Secondary 4: 42-0-42V @ 0.7A rms
GOSS band
Dimensions: approx 160x80mm
Mounting: M8x30mm bush
In a potted centre
Heavy gauge lead outs... Turned out to be 18AWG
Black acetate finish

My mains is now running at 248v, which after the minicap gives me +/- 52V DC, just wondering whether this is too much for the NCC220s?

 

[mega lord]

52V is fine with ncc200 and I can't see the ncc220 being any different.

 

[mega lord]

My CW transformers don't hum but maybe you have more dc on the mains than me.