'AK Mods' SC Class A 15W Amplifier

[Deleted]

the loudsspeaker protection kit is still listed at jaycar as a back catalogue item for Internet order only for half the price that Altronics list it for.

Hi Shaun
Perhaps that is due to many SC projects appearing some time later in the U.K. publication Everyday Practical Electronics ?
The SC DAC for example, has only recently been published in that magazine.I will soon have colour scans of part 3 of that article if anybody who has built it wants a copy.
Regards
Alex

[Deleted]

Nov 28, 2011 23:18:38 GMT @sandyk said:

the loudsspeaker protection kit is still listed at jaycar as a back catalogue item for Internet order only for half the price that Altronics list it for.

Hi Shaun
Perhaps that is due to many SC projects appearing some time later in the U.K. publication Everyday Practical Electronics ?
The SC DAC for example, has only recently been published in that magazine.I will soon have colour scans of part 3 of that article if anybody who has built it wants a copy.
Regards
Alex

Hi Alex

yes could be the case I've seen that mag so I'll have to take a closer look next time.

which brings me on to the question of loudspeakers and the protection off.

I've got a nice pair of £5 per pair from a charity shop for stunt speaker duties. I've had them for years now and always wheel them out for first switch on and music duties. i know that with the speaker protection board they should not be needed but for the price it's a little insurance.

no need to play catch the cone with the more expensive ones.

take care

[Deleted]

As for what's next, well how about a DIY HD-projector?

I have a feeling you're not joking

Syd

[Deleted]

I haven't had breakfast yet,so I am not fully awake yet.

H'mmmm! and we're just off for a bit of shut-eye.........being not fully awake either. ;D

[Deleted]

Having considered Alex and Will's input on my proposed PSU
here is the current schematic..................it's getting close to laydown
just spend some time now on which higher amperage and faster diodes to go for then a few days at the layout.
Sorry Will traffos are in Santa's sack so no soak test till the 25th,
that'll let the dust settle a bit.
Thanks Alex and Will much appreciated.
Regards,
Alan

[jeffc]

Hi Alan,

This whole article contains a wealth of useful information, just in case you haven't looked though it before. See Rectified Diodes that faster diodes might not necessarily be better and could possibly be worse in this application, at least according to ESP

sound.westhost.com/power-supplies.htm

Not keen on toroidal transformers for amp applications either.

cheers.. jeffc

[Deleted]

Nov 29, 2011 2:26:42 GMT jeffc said:

Hi Alan,

This whole article contains a wealth of useful information, just in case you haven't looked though it before. See Rectified Diodes that faster diodes might not necessarily be better and could possibly be worse in this application, at least according to ESP

sound.westhost.com/power-supplies.htm

Not keen on toroidal transformers for amp applications either.

cheers.. jeffc

Jeff
It's not just about diodes that are fast. They also need to be slow recovery.
Alex

[jeffc]

Point taken Alex,

Bit slow in mental recovery myself but Rod Elliott does offer very informative and down-to-earth summaries of important stuff to consider.

cheers.. jeffc

[Deleted]

Jeff
Apparently there is a fairly new diode from ON that is very good in this respect. It was mentioned by "Barrows"in another forum.
I can't find the details at present.
Alex

[jeffc]

Alex,

I have 8 x 1N5404 as well as 8 x 15A rated MUR1520 TO220 and 4 x 8A rated MUR820 TO220 all from ON. Might use the 4 x MUR820 for a 'hot rodded' Salas DC-B1 but either of the others are looking for a good use

cheers.. jeffc

[mrarroyo]

Nov 28, 2011 11:42:24 GMT @sandyk said:

What have you been smoking lately Alex?

Smart Yanks ! ;D

Thanks!

[Deleted]

Might use the 4 x MUR820 for a 'hot rodded' Salas DC-B1

[Deleted]

Hi All

My birthday transformers where delivered safely this afternoon.



so ordered on Saturday and delivered Tuesday. pretty good going but usual for Airlink.

2X 230V 2X 20 160VA with ESO1 electrostatic screen and EMI/RF shield,

just on the rectifier diodes

would it be better to use a bridge package rather than individual diodes?

I'm just thinking that those TO22O type ones may need heat sinking where as the package ones just bolt to the chassis.

if people think that there will be big SQ issues with package bridge type ones then it could be worth the extra effort of going MUR820 which i have from the Salas build.

just thinking

any input most welcome

take care

[Deleted]

Hi Shaun,
after the hint from Jeff and reading his ref. to a hotrod salas I had a look at the MUR820.
RS have them by Vishay at .50p each so I might go with them and make provision for a bit of sinking on my boards.
Also decided to look at spade lugs/or terminals rather than Con. blocks
Also looked at the Jaycar SPk Pro Kit.........that looks a reasonable buy @ £13.50 incl postage.
buying 5 units.
Do you know if we'd get lumbered with Tax at this end.
Alan

[Deleted]

Hi Alan

Do you know if we'd get lumbered with Tax at this end.

I've never had a tax bill from the Jaycar orders yet but there's always a first time i guess.

take care

[Deleted]

Hi Alex,
by slow recovery I take it you are referring to something like this.......................
Fast recovery/ultra soft diode 10A 1200V IXYS DHG10I1200PM

RS have them

Qty Unit Price
25 £1.24 each incl. vat
100 £1.11 each incl. vat
Alan

[Deleted]

Crikey!

You guys don't hang around, I've hardly given this any thought and you lot are taking in deliveries already


coughs, choking on the smoke of those ahead

[Deleted]

Time to Kill.........................Time to Kill
your time will come.

[Deleted]

Nov 29, 2011 17:19:21 GMT @cjarchez said:

Crikey!

You guys don't hang around, I've hardly given this any thought and you lot are taking in deliveries already


coughs, choking on the smoke of those ahead

Hi Chris

just making hay while the sun shines

take care

[Deleted]

Nov 29, 2011 13:08:07 GMT @shaun said:

Might use the 4 x MUR820 for a 'hot rodded' Salas DC-B1

You would need 8.
I am still using the KBPC1004 10A 400V bolt on bridge rectifiers as per the original B.O.M. I have thought about trying individual
"audio" diodes instead , but never got around to it, as I find it hard to believe that any residual diode switching crap would get through the regulated PSUs AND the JLH with it's extra 40dB or thereabouts of noise reduction. Besides which, you could always solder suitable capacitors across the terminals of the external bridge rectifiers.However, if using PSU PCBs like those recent versions from Will, you can't use bolt on bridge rectifiers.
The MUR820 etc. would not need heatsinks.

Alex

P.S.
If any intending constructors would like a copy of the original SC 15W amplifier articles, please send me a PM.
Also,for those who have constructed the SC DAC, I can supply scanned colour copies of part 3 (also parts 1 and 2) of the SC DAC
which goes into the final set up and remote control use etc.

[Deleted]

Nov 29, 2011 17:11:21 GMT drymdrum said:

Hi Alex,
by slow recovery I take it you are referring to something like this.......................
Fast recovery/ultra soft diode 10A 1200V IXYS DHG10I1200PM

RS have them

Qty Unit Price
25 £1.24 each incl. vat
100 £1.11 each incl. vat
Alan

Hi Alan
I did mean soft recovery.There should be plenty of similar types available with lower ratings, and also a little less expensive.
Alex

e.g.

Diode,rectifier,fast recovery,10A,600V,TO220AC,DHG10I600PA

australia.rs-online.com/web/p/rectifier/0462221/

[Will]

Nov 29, 2011 14:15:08 GMT @shaun said:

Hi All

My birthday transformers where delivered safely this afternoon.



so ordered on Saturday and delivered Tuesday. pretty good going but usual for Airlink.

2X 230V 2X 20 160VA with ESO1 electrostatic screen and EMI/RF shield,

just on the rectifier diodes

would it be better to use a bridge package rather than individual diodes?

I'm just thinking that those TO22O type ones may need heat sinking where as the package ones just bolt to the chassis.

if people think that there will be big SQ issues with package bridge type ones then it could be worth the extra effort of going MUR820 which i have from the Salas build.

just thinking

any input most welcome

take care

Happy New Birthday Traffos!

They look nice and solid Shaun, we just need the pcbs to connect up to it

My star type heatsink for the 327/337 turned up today, very quick delivery. The seller includes a very nice letter, and a tempting offer on some radio kit. I've been tempted on an DIY FM radio for a bit, but I must resist!

[Will]

I think that at the currents we are looking at, these to220 diodes seem to be the best bet and easy enough to do on the pcb. Silicon Carbide seem to be the new 'must have' audio diode, and are coming down in price. Not sure which types are the better ones. These Cree ones can be had for £3 odd.

If it helps keep the pressure of Alex, I'm also happy to pass the SC class A article on to those building.

[Will]

Do you know if we'd get lumbered with Tax at this end.

Alan, I didn't get caught this last time, so go ahead. The last order took 5 days to get from Australia to work, so very quick.

If you are making an order with Jaycar, I might ask a favour of you.

[Deleted]

My star type heatsink for the 327/337 turned up today, very quick delivery. The seller includes a very nice letter, and a tempting offer on some radio kit. I've been tempted on an DIY FM radio for a bit, but I must resist!

Hi Will

yes mine arrived today as well he must have posted at the same time

so we have some spare.

on rectifiers

I must say that my gut instinct goes with Alex re the Rectifiers.

but

in the interest of discovery maybe some of those nice Silicon Carbide ones would be good to try. it would be a shame for the sake of an extra few quid to not try them.

let's not spoil the ship for a h'pence of tar.

or if you make space on the board for TO220 rectifiers then people could choose there own poison.

if we reach a consensus then a GB looks like a good idea.

on the boards well no rush on that front.

it's just a time of year for me to stock up a little before the new year belt tightening kicks in.

there is still plenty to do prep wise JLH, soft start (i know no real need for one but i quite like the idea of having one anyway), transistors to match, resistors to sort out. umbilical connection between PSU and Class A to think on.

yup plenty to do.

I've pushed out some of the SC class A stuff also. so am more than glad pass on more of that.


take care