'AK Mods' SC Class A 15W Amplifier

[Deleted]

Alan'
Do you have a copy of the original article ?
Alex

The relay specifications
www.altronics.com.au/index.asp?area=item&id=S4313A

[jeffc]

Hi Alex,

By chance you don't have the SC article on the Speaker DC Protector kit . I'll pick mine up next week, and it'd be nice to do a little background reading so I half a clue about how it works. I seem to remember a mod or 2 being required too.

cheers.. jeffc

[Deleted]

Attention " Mr. NO KITS" ;D

The relay is from the JQX-13F series. Is this it below ?

www.ebay.com.au/itm/10x-24V-DC-Coil-Power-Relay-DPDT-LY2NJ-HH62P-L-JQX-13F-/290580416911?pt=AU_B_I_Electrical_Test_Equipment&hash=item43a7f1498f

www.ebay.com.au/itm/5x-24V-DC-Coil-Power-Relay-DPDT-LY2NJ-HH62P-L-JQX-13F-/300570409951?pt=AU_B_I_Electrical_Test_Equipment&hash=item45fb647bdf


A single relay :
www.ebay.com.au/itm/JQX-13F-DC-24V-Coil-AC-10A-240V-DC-28V-Contact-Relay-/380411566989?pt=AU_B_I_Electrical_Test_Equipment&hash=item58924bdb8d

[Deleted]

The pot versus stepped attenuator reason is not a very valid reason

Frans
With the attenuator in use originally in an earlier preamp, which was likely not a make before break type, the extra time constant completely eliminated the click problem, which was particularly noticeable when feeding Greg Erskine's "Carlos DX amplifier."
(That is one amplifier that I never wish to hear again.)
Unlike the 15W Class A , the preamp offset corrector does need to be faster acting due to attenuator/ volume control resistance changes,and has been proved to be very effective with this design.
Alex

[Deleted]

Do you have a copy of the original article ?

Alex yes I have all info required to build the item.
Plus I only require the appropriate relay and BC556 as all other parts are in stock.
I'd rather source the relay here in UK if possible.
Since I've a reasonable handle on the practicalities of construction but very little on the theoretical I do require some hand holding in that department.
Buying specified part from Au. would be the easy way out if rather OTT time and cost wise compared to buying from RS Uk who deliver post free and next day.
With regard to the coil resistance I take it that adjustment can be made in circuit.
Many thanks for your assistance.
Regards,
Alan

[Deleted]

Hi All

sorry I'm a little confused.

are the calculated values for OP in Class A for Alex's amp now as follows:

15W Class A into 8ohm
7.5-8W Class A into 4ohm.

so close to the figures originally published by SC.

those figures look easily good enough to drive most speakers to decently high levels in Class A.

so

only speakers that have outrageously low sensitivity and impedance are going to fluster the Class A as it would most amps.

just in case anyone has missed that part of the discussion.

i know that it's confused me a little

do i have that right?

take care

[Deleted]

Feb 25, 2012 2:33:12 GMT jeffc said:

Hi Alex,

By chance you don't have the SC article on the Speaker DC Protector kit . I'll pick mine up next week, and it'd be nice to do a little background reading so I half a clue about how it works. I seem to remember a mod or 2 being required too.

cheers.. jeffc

Hi Jeff

the kit is pretty complete and has a full set of instructions as well as comprehensive how to test its working sheet.

i had no problems with it whatsoever

worked first time

saved my speakers from the Barbi

it's a great kit as usual from the guys down under. well though out and well written instructions with a decent quality board /components.

a snip at the price

i wish we had Jaycar/altronics shops here.

it would make life soooooo much easier
take care

[Deleted]

Origins of the Offset Corrector.
The Offset Corrector was an adaptation of the original used by David Tillbrook in his AEM6000 240W/8 ohms/Channel Mosfet Power Amplifier which was constructed in the many thousands worldwide.
If anyone would like to see tfurther info about it, feel free to contact me.
Alex

Attachments:

[jeffc]

the kit is pretty complete and has a full set of instructions as well as comprehensive how to test its working sheet.i had no problems with it whatsoever

Thanks Shaun,

Nice to know all is straight forward, I've built a few SC kits now and all have had terrific documentation. The Speaker Protector kits have been ready for pick-up for weeks but they seem to be still mining the iron ore for the heat sinks I ordered at the same time . They're due Wed, about a month since order, mustn't be much call for them due to there being few maniacs like me, or Alan willing to have a go at building they own Class A amplifier cases.

cheers.. jeffc

[Deleted]

Hi Jeff,
what are your thoughts on case building?
I've built a great many wooden boxes and have commissions for three to make this spring.
My only attempt at a metal case was for the great SandyK preamp which is about to get a partner. I like to think of that case as a metal duffers first try and made a lot of errors in it's construction.
Thankfully it doesn't distort that great "AK CLASS A" sound.
So I've a few ideas for its mate when I get round to it's construction.
Regards,
Alan

[Deleted]

Feb 26, 2012 21:07:01 GMT jeffc said:

the kit is pretty complete and has a full set of instructions as well as comprehensive how to test its working sheet.i had no problems with it whatsoever

Thanks Shaun,

Nice to know all is straight forward, I've built a few SC kits now and all have had terrific documentation. The Speaker Protector kits have been ready for pick-up for weeks but they seem to be still mining the iron ore for the heat sinks I ordered at the same time . They're due Wed, about a month since order, mustn't be much call for them due to there being few maniacs like me, or Alan willing to have a go at building they own Class A amplifier cases.

cheers.. jeffc

Hey Jeff

how's it going?

any chance of posting a link to the heat sinks you've ordered?

yes i know that you may have done already and I've most likely missed it.

so could be useful for others.

take care

Hi Alan

my Hifi 2000 case is all aluminum 3mm for the back,top,bottom and sides and 10mm for the front panel. the whole case dissipates heat so I'd make those panels pretty thick.

also good bottom to top air flow (especially across the OP devices and regs) greatly helps cooling.

probably not to useful but may help.

take care

[jeffc]

Hi Shaun,

These Altronics ones x 4 ordered through Delsound, my local distributer, who usually give an additional discount to keep your busness .
www.altronics.com.au/index.asp?area=item&id=H0545
And I noticed these 2U rack cases on special ATM when looking for the heat sink link.
www.altronics.com.au/index.asp?area=item&id=H5012

cheers.. jeffc

[Deleted]

Feb 26, 2012 23:32:44 GMT jeffc said:

Hi Shaun,

These Altronics ones x 4 ordered through Delsound, my local distributer, who usually give an additional discount to keep your busness .
www.altronics.com.au/index.asp?area=item&id=H0545
And I noticed these 2U rack cases on special ATM when looking for the heat sink link.
www.altronics.com.au/index.asp?area=item&id=H5012

cheers.. jeffc

Hi Jeff

nice beefy heatsinks look very good for the price.

take care

[jeffc]

Hi again Shaun,

With pine bases and hardwood fronts/backs cut and routered ready for my cases, ventilated 3 mm aluminium tops, yep these heat sinks should act as good fire starters with all this kindling.

cheers.. jeffc

[Deleted]

Feb 27, 2012 5:15:01 GMT jeffc said:

Hi again Shaun,

With pine bases and hardwood fronts/backs cut and routered ready for my cases, ventilated 3 mm aluminium tops, yep these heat sinks should act as good fire starters with all this kindling.

cheers.. jeffc

Hi Jeff

mine does not run very hot so you should be A OK with that sinks and chassis scheme.

just to at the final touch you could put some venting in the base also to allow for air flow on the OP devices.

looking good

take care

[jeffc]

just to at the final touch you could put some venting in the base also to allow for air flow on the OP devices.

Yep that's "The Plan" Shaun
Just need PCB's to figure out neatest most practical layouts before I start drilling big holes all over the place.

With using wood, its going to be some fun fitting IEC power sockets, RCAs, speaker binding posts and the like but I've got a good drill, router etc so in the spirit of "No Kits Please" Alan shall give it my best shot. From your very modest reports , this amp deserves a special effort.

cheers.. jeffc

[Deleted]

Feb 27, 2012 11:19:18 GMT jeffc said:

just to at the final touch you could put some venting in the base also to allow for air flow on the OP devices.

Yep that's "The Plan" Shaun
Just need PCB's to figure out neatest most practical layouts before I start drilling big holes all over the place.

With using wood, its going to be some fun fitting IEC power sockets, RCAs, speaker binding posts and the like but I've got a good drill, router etc so in the spirit of "No Kits Please" Alan shall give it my best shot. From your very modest reports , this amp deserves a special effort.

cheers.. jeffc

Hi Jeff

I've used wooden chassis for my tube builds and I've found that using metal plates for the IEC sockets/speaker OP and RCA inputs works pretty well.

just make the holes and cut outs in Ali plates for the sockets and screw them to the inside of the chassis. you can just cut holes in the woodwork to allow the sockets to stick out. it looks cool with all of those smooth curves even with my limited skills woodwork wise.

finish with some nice lacquer and mmmmmmmmmm looks great.

not the best of explanations but hopefully you get the jist.

using wood chassis is quite common for tube amps and I'm pretty sure that you will find lots of examples on the net. you'll end up with a nice retro looking amp which is going to have the WOW factor in spades.

could be a good place for ideas.

TBH I've found trying to cut and fix those sockets directly to the wood a little problematic. not least tryng to get a good tight fix.

Claus is a RG member has done some lovely work with wood so you could do worse that get some tips from him.

I'll try to find some examples on the tube front.

take care

[Deleted]

Hi Jeff

here is a nice 2a3 project which uses a wooden chassis with the metal plate method i outlined in my last post. so just a tiny little bit OT maybe.


oldheadphones.com/crystal/info/tubeamp.htm



it's obviously not the same amp as Alex's Class A but I've posted it to help those thinking of building their own chassis.

i'd go for a number of plates to allow better spacing of the sockets.

i hope that it helps a little

I've built plenty of amps this way and the fit and finish can end up looking pretty good.

take care

[Deleted]

The only two things I've made that way were an input expander and rehousing a keyboard amp. The expander turned out particularly well.
--------------------------------------
EDIT

I forgot to mention I did mine a little differently. I first made a Naim-esque sled or gondola type chassis. This had all the hardware mounted to it. Then the wooden panels were added with cut outs in all the appropriate places.
---------------------------------------
An absolute must, after careful planning, is decent quality tools for the job.

Who was it who made that really impressive SCHA, or was it a Panda , case, with lovely wood panels and mesh. One of our Australian members IIRC....

>>>>>>>Thanks Alex, here

PS

I've just planned out the new case for my SCHA/USB/I2S combo, it will be all metal and a variation on the theme of my original SCHA case. I hope to go metal buying tomorrow morning! Ha Ha, no I won't, it's a holiday tomorrow

[Deleted]

Who was it who made that really impressive SCHA, or was it a Panda , case, with lovely wood panels and mesh. One of our Australian members IIRC....

Chris
That was nickyboyo's SC HA.Nick is from Richmond just out of Sydney.
Alex

[jeffc]

here is a nice 2a3 project which uses a wooden chassis with the metal plate method i outlined in my last post. so just a tiny little bit OT maybe.

Thanks for the encouragement guys , but Shaun, this wooden case build link is setting the bar just a little high for me. Fronts and backs will be grooved hardwood decking, recessed in on the backside at the sides for the heatsinks and at the top to fit the 3 mm Al top plate. Al back plates for fixtures could make life easier, definately something to consider. Sides will be the heat sinks. Finish with be a rich Jarrah (red) stain for a dull/mat finish (just because I have some and like it). Don't want any gloss, shows up too many imperfections. With a bit of luck I'll end up with something Fred Flinstone would be proud to own. When the heat sinks arrive, I'll do a mock build for a happy snap.

cheers.. jeffc

[Deleted]

Feb 27, 2012 20:56:04 GMT jeffc said:

here is a nice 2a3 project which uses a wooden chassis with the metal plate method i outlined in my last post. so just a tiny little bit OT maybe.

Thanks for the encouragement guys , but Shaun, this wooden case build link is setting the bar just a little high for me. Fronts and backs will be grooved hardwood decking, recessed in on the backside at the sides for the heatsinks and at the top to fit the 3 mm Al top plate. Al back plates for fixtures could make life easier, definately something to consider. Sides will be the heat sinks. Finish with be a rich Jarrah (red) stain for a dull/mat finish (just because I have some and like it). Don't want any gloss, shows up too many imperfections. With a bit of luck I'll end up with something Fred Flinstone would be proud to own. When the heat sinks arrive, I'll do a mock build for a happy snap.

cheers.. jeffc

Jeff that sounds great

but setting the bar a little high? naaaa don't forget I've seen how good your work is (that nice little 9023 you've built). yup silk,mat or wax oil gets my vote it looks cool and hides my mistakes well.

i just posted the link to illustrate what i was trying (not very well) to say re using plates to fix the plugs and sockets. I've found it easier to work that way but others may not.

the happy snap would be appreciated this end

take care

Hi Cris

that nickyboyo Build you linked to is very sweet indeed
a really nice build.

some pictures of the work you mentioned in the above post would be great.

just to mention with DIY cases theres no right and wrong way it's totally free form. I've seen amps built into retro coffee machines so it's all good. do keep safety in mind though

take care

[Deleted]

Feb 6, 2012 16:41:39 GMT @shaun said:

Jan 25, 2012 13:19:18 GMT @shaun said:

Jan 19, 2012 18:33:23 GMT @shaun said:

Jan 8, 2012 11:11:25 GMT @shaun said:

Hi All

just to keep this available.

for the LS device GB so far i have

Will 2x LS352 and 2X LS313
Phil 2x LS352 and 2X LS313
Me 2x LS352 and 2X LS313
Syd 2x LS352 and 2X LS313
Alan 4X LS352 and 4X LS313
Alex 2X LS352 and 2X LS313
Mark 2X LS352 and 2X LS313 (cyteen)
Jeff 2X LS352 and 2X LS313
Jon C 2X LS352 and 2X LS313
Geoff 4XLS352 and 4XLS313

Kits GB

Chris
Syd
Phil
Will
mark (cyteen)
Jon C
me
Geoff x 2 sets

Boards only GB

Alex
Alan
Jeff

Just a quick reminder of where we are at.

We have another friend joining us from down under

[geoff]

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

[Deleted]

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