'AK Mods' SC Class A 15W Amplifier

[Deleted]

Feb 28, 2012 11:56:26 GMT geoff said:

Thanks for the warm welcome Shaun.

I can povide testimony as to the quality of the AK modded SC Class A 15W amp. I am a friend of Alex and have heard the difference all the mods have made over the years on his prototypes. My current amplifier is one of Alex's older SC Class A 15W builds. Now I desire the full house version and look foward to sharing my interest in this amplifier with the group.

If I may, I'd like 4X LS352 and 4X LS313.

When you are ready, I'd also like complete kits for 4 mono amps as well as 4x boards. The reason being that I already have heat sinks and toroidals for them. I'll build 4 modules now, but would like ythe boards for future use. Many thanks

Hi Geoff

Welcome to RG it's always nice to have company.

OK I've modded the list accordingly so have a quick look to make sure i have your needs met. on the kits we're thinking of everything except coupling caps and resistors which people generally have their own ideas of whats good for them which is as it should be.

i hope that's OK with you

i have a self etched version of Alex's class A PA with duel transformers and regs. i also use his HA/PRE and both are stunningly good in their own right but together they are just magical.

as you say it's quite a different amp from the SC original and the changes that Alex has made make a huge difference SQ wise. it's easy to miss how much work has gone in to the current model but taking a look at the original circuit will give people a clue.

yup I've tried it sans JLH and de-tuned the front end and well IMHO it's not the same amp SQ wise.

i have 2N3811 and LM394H on my front end which sound very nice indeed and I'll look forward to comparing with the LS when the new build comes up.

looking forward to building this fantastic amp with you Geoff.

take care

[Deleted]

Feb 28, 2012 13:09:12 GMT @cjarchez said:

Shaun,

No can do on the old builds from many moons ago
The keyboard amp belonged to the keyboard player and stayed with her. The input expander was lost in a house move in the UK.

Geoff,

Hello! Your four mono blocks sounds interesting, is that biamping or going active? I was starting to think along these lines (active) myself.

Chris

Hi Chris

no worries on that just fishing for ideas.

take care

[Deleted]

Shaun,

The concept is really easy.

Imagine a U-shaped metal plate to dimensions required I__________I.
One end of the U takes all the front panel controls and the other end takes all the socketry.
Then simply apply the finishing panels of choice, Nice 'n' Easy does it...

=I__________ID
geddit

(It took me ages to do those diagrams ;D )

[Deleted]

Feb 28, 2012 22:38:26 GMT @cjarchez said:

Shaun,

The concept is really easy.

Imagine a U-shaped metal plate to dimensions required I__________I.
One end of the U takes all the front panel controls and the other end takes all the socketry.
Then simply apply the finishing panels of choice, Nice 'n' Easy does it...

=I__________ID
geddit

(It took me ages to do those diagrams ;D )

sounds good to me Chris

take care

[Will]

Hi Guys,

Really, really sorry that I've gone quiet on this (and the emails) but to cut a long story short, I've been offered a career opportunity which is taking a bit of sorting out, not least the fact that all my eagle files are on my (soon to be) ex-works laptop.

Hopefully sorted out soon, and if I'm lucky I can get stuck into completing the pcb if I get sent on "gardening" leave

Will

[Deleted]

Feb 29, 2012 20:24:30 GMT Will said:

Hi Guys,

Really, really sorry that I've gone quiet on this (and the emails) but to cut a long story short, I've been offered a career opportunity which is taking a bit of sorting out, not least the fact that all my eagle files are on my (soon to be) ex-works laptop.

Hopefully sorted out soon, and if I'm lucky I can get stuck into completing the pcb if I get sent on "gardening" leave

Will

Hi Will

no worries and no rush

we've had some fun mulling over the hardware requirements and speakers etc.

my amp is really singing now that Alex has sorted my schoolboy error of reversed MPSA out .

however long it takes it's going to be worth the wait.

mmmmmmmmmmmmmmm

gardening duties my favorite.

really nice to hear from you

take good care

[Deleted]

Hi Will,
nice to hear from you, it's all right for us long in the tooth unfit for work types with too much time on our hands.
Like Shaun says we've been kicking around a few ideas and if you hadn't started the thread I'd certainly not be building the AK Mods 15 Watt and I'm sure we can all cut you a little slack.
So take care,
Regards,
Alan

[Deleted]

Hi All,
unlike Shaun my skipping days are over and everything slows down.
However here's some pics of the state of play with my
AK Mods 15 Watt'er.

I've just to cut the board for SPKR PRO build it up and I can move onto the case.
Main boards are still short of the OPs and the BC550/560s
I have them in hand to pop in when I've sorted the SPKPRO.
So there you are Shaun slow but working on it.
Regards,
Alan

[Deleted]

[Deleted]

[Spirit]

No worries re the delay Will
Just gives me time to find a real job so I can afford the shipping on some cases from Hifi2000

Speaking of speakers, I rediscovered that mine are 6 ohm nominal, and 92db@1m, so Class A all the way for me
(My room is not so big)

[Deleted]

Mar 1, 2012 0:27:22 GMT drymdrum said:

Hi Alan

grrreat work on those boards and up to your usual high standards.

slow

naaaa it just has all of your usual attention to detail and class that my builds often lack.

your board work really inspired me to have a go just using a slightly different modus O.

just a small skip now and you're there

take care HFSM

[Deleted]

Hi Phil

what speakers are you using?

take care

Hi Alan (you dark horse you)

I've just noticed those Wireless World speakers you've posted in the LS thread.

they look splendid with their what looks like Kef bass/mids with celeston tweeters, TL tooooo

I've heard the bass units before and they are very good.

care to elaborate on the design a little?

errr pretty please

take care

[mrarroyo]

You guys are good, wish I could build something like this. Enjoy it.

[Deleted]

Hi Shaun,
I built these many moons ago to a design in Wireless World, mid to late seventies. Kefs' yes not sure about the tweeter but Celestion could be. I looked for the design a while back but reckon any paper work was tossed out and a web search got me nowhere, I'm still looking. I think Wilmslow Audio supplied the Kefs, crossover and tweeter. The cabinets are MDF glued and screwed with an outer skin of hardwood ply they were my first true shot at woodworking.
I suppose I could take the back off for a look but they are so bloody heavy I can only walk them corner to corner.
Can't tell you any more without that look and short of them blowing up it wont happen.
Regards,
Alan

[Deleted]

Mar 1, 2012 20:59:19 GMT drymdrum said:

Hi Shaun,
I built these many moons ago to a design in Wireless World, mid to late seventies. Kefs' yes not sure about the tweeter but Celestion could be. I looked for the design a while back but reckon any paper work was tossed out and a web search got me nowhere, I'm still looking. I think Wilmslow Audio supplied the Kefs, crossover and tweeter. The cabinets are MDF glued and screwed with an outer skin of hardwood ply they were my first true shot at woodworking.
I suppose I could take the back off for a look but they are so bloody heavy I can only walk them corner to corner.
Can't tell you any more without that look and short of them blowing up it wont happen.
Regards,
Alan

Hi Alan

from memory.

those flat bass units are constructed using a front and back sheet and a sort of honey combe center (sandwich). I've only seen these made by kef and they are good units. i think that the shape was an attempt to reduce resonance but i may be wrong.

the construction method created a light but stiff drive unit.

nice looking speakers you have

if only my woodwork was up to snuff.

take care

[Deleted]

those flat bass units are constructed using a front and back sheet and a sort of honey combe center (sandwich). I've only seen these made by kef and they are good units. i think that the shape was an attempt to reduce resonance but i may be wrong.

Hi Shaun
Years ago I had a pair of Sony honeycomb speakers.
I replaced them with the DCM QED speakers .
Regards
Alex

[Deleted]

Ooooh, I remember the Sonys, 3 ways, flat bass and a flat mid too.
990 if memory serves.

Don't forget the Linn Isobarik. Love it or hate it, a big beastie.

Sony also used flat drivers in some later cheap speakers but with a different drive set up, can't remember exactly what now.


PS

@will,

Great news on the career opportunity, not much news like this flying around of late. Good on ya!

The extra time is actually quite welcome so no worries at all

[Deleted]

Ooooh, I remember the Sonys, 3 ways, flat bass and a flat mid too.

Hi Chris
I was doing something else, and the phrase "APM33W" suddenly popped into my head .
I guess that must mean that Alzheimers hasn't quite set in yet ?
Regards
Alex

Attachments:

[Deleted]

Hi Alex,

Those are cheaper ones I was refering to. I've just found the 990 I mentioned ( I may be CJ but not CJD )

[Deleted]

Mar 2, 2012 0:09:59 GMT @sandyk said:

Ooooh, I remember the Sonys, 3 ways, flat bass and a flat mid too.

Hi Chris
I was doing something else, and the phrase "APM33W" suddenly popped into my head .
I guess that must mean that Alzheimers hasn't quite set in yet ?
Regards
Alex

Hi Alex

''made for digital'' tooo

i do remember something like these Sony speakers arriving at the shop periodically they had usually done serious house party duties by then. we also had a few isobarik's which did use Kef bass and mid drivers and sounded.

Chris those square Sony's just don't look right to me far to space age superfi superfly.

take care

[Deleted]

Too right Shaun,

For sure the 990s had conventional drivers attatched to the rear of the flat panels!
I'm guessing the 33s were the same?

[Spirit]

Mar 1, 2012 9:59:57 GMT @shaun said:

Hi Phil

what speakers are you using?

take care

Hi Shaun,

A pair of Dali Ikon 7:
www.avhub.com.au/index.php/Product-Reviews/Hi-Fi/dali-ikon-7-loudspeakers.html

A mate of mine worked briefly for a joint where he could get them for wholesale, so I ended up paying $1600

Feeling the tiniest bit overwhelmed with all the stuff I'll need to learn to put together the Class A, having not constructed the AK Class A HA

Cheers,
Phil

[Deleted]

Feeling the tiniest bit overwhelmed with all the stuff I'll need to learn to put together the Class A, having not constructed the AK Class A HA Cheers,Phil

Hi Phil
What do you intend using to give you control of volume?
Regards
Alex

[Deleted]

Mar 2, 2012 3:04:42 GMT Spirit said:

Mar 1, 2012 9:59:57 GMT @shaun said:

Hi Phil

what speakers are you using?

take care

Hi Shaun,

A pair of Dali Ikon 7:
www.avhub.com.au/index.php/Product-Reviews/Hi-Fi/dali-ikon-7-loudspeakers.html

A mate of mine worked briefly for a joint where he could get them for wholesale, so I ended up paying $1600

Feeling the tiniest bit overwhelmed with all the stuff I'll need to learn to put together the Class A, having not constructed the AK Class A HA

Cheers,
Phil

Hi Phil

interesting looking speakers which the Class A should drive with ease. I've not listened to any Dali's but the have a good reputation.

on the Class A construction.

it was my first solid state PA and apart from one silly mistake all was OK.

you'll have plenty of help here if needed so just relax on that.

Alex's pre question is a good one and if you have not done so already you could get in a little practice by building His HA/PRE while you wait.

together they make a great combination

take care