'AK Mods' SC Class A 15W Amplifier

[Will]

Jul 5, 2012 12:12:25 GMT XTRProf said:

Hi Will,


Confirmed:


Chong 2xLS352 and 2xLS313. Matched, right?

The PS PCBs increase to 16 though since they can do 5A. The final number will depend on final price of each PCB.

Thanks for your usual good effort for the diy community here and elsewhere.


Chong.

Hi Chong,

Just to be really clear on this, the PSU for the Class A power amp should be good for 5A, with a suitable regulator (no one really knows, as none of the pcbs have been made). Also, as mentioned in the PM, this is a dual PSU for both positive and negative voltages. If you want a 5A negative voltage, you'll need a negative regulator, capable of 5A, that is pin compatible with the LM317/LT1033.

I'm repeating this as I really want you to be sure about what you are buying, as the last thing I'd want is for you to buy 16 pcb's that don't meet your needs

On the LS 313 and 352, I'll be able to do a GB for them, but most likely at the end of August. I've not got the time to match them for people, so if matched ones are required you'd need to buy more and match them yourself

[jeffc]

Hi Will

Great news, and sorry to be late, I haven't checked in for a few days. Like you, I plan for dual mono, so..

2 x LS313, 2 x LS352
2 x Amp PCBs
2 x PSU PCBs

And if general interest in more single JLH PCBs, I'll be in for a few, but will suggest a very minor, but useful, mod of extending tracks and adding a couple of extra holes/pads to allow neat fitting of 10 mm pitch 2.2uf caps like these.

au.element14.com/arcotronics/r60df4220506aj/capacitor-2-2uf-63v-10mmp/dp/1679335?Ntt=167-9335

cheers.. jeffc

[Deleted]

And if general interest in more single JLH PCBs, I'll be in for a few, but will suggest a very minor, but useful, mod of extending tracks and adding a couple of extra holes/pads to allow neat fitting of 10 mm pitch 2.2uf caps like these.http://au.element14.com/arcotronics/r60d....35?Ntt=167-9335cheers.. jeffc

Cheapskate! ;D

























Why didn't I think of that !

[Deleted]

Hi Jeff and Alex,
that cap is available from Farnell UK at half the Aussie price the AU price is before tax the UK after tax.
UK for ten £4.08 incl tax delivery free
Au for ten 12.9$ plus tax
at today's conversion that makes Au price for ten £8.50
Makes you think.
Alan

[Deleted]

Jul 5, 2012 22:55:08 GMT drymdrum said:

Hi Jeff and Alex,
that cap is available from Farnell UK at half the Aussie price the AU price is before tax the UK after tax.
UK for ten £4.08 incl tax delivery free
Au for ten 12.9$ plus tax
at today's conversion that makes Au price for ten £8.50
Makes you think.
Alan

Hi Alan
I still have a few Wima 2.2uF left, and more 1.5uF 63V that are suitable. I will need to check my stocks .Farnell is free delivery for online orders here too. Our GST is 10%, what is yours these days ?
( just curious)
Kind Regards
Alex

[Deleted]

HI Alex,
twenty % VAT on most goods, not food, books, childrens clothes, if you eat out it's plus tax
it's a bit of a minefield,
Alan
www.bbc.co.uk/news/uk-politics-18245963

[Deleted]

Alan and Jeff
I have 8 x Wima MKS2 2.2uF 5mm spacing, which is just what I need for the Class A . I still have 19 x 2.2uF from old Dick Smith stocks,(Thanks Dave !) with 5mm lead spacing.If Jeff is willing to accept 8 of them in return for the W & J JLH PCBs he sent me a while back, I would be pleased to send them to him.
Kind Regards
Alex

[XTRProf]

Jul 5, 2012 19:50:55 GMT Will said:

Just to be really clear on this, the PSU for the Class A power amp should be good for 5A ...

you'll need a negative regulator, capable of 5A, that is pin compatible with the LM317/LT1033.

The 5A already make them positive buy. Well, not exactly yet. The total price too.

Jul 5, 2012 19:50:55 GMT Will said:

On the LS 313 and 352, I'll be able to do a GB for them, but most likely at the end of August. I've not got the time to match them for people, so if matched ones are required you'd need to buy more and match them yourself

How much is each? Roughly will do.

[jeffc]

Cheapskate!

Yep ....... I've gotten that reputation somehow?

Actually, when I got a batch of 30 from Element 14 in Nov last year they were much cheaper ...... 30 x $0.378 = $11.34 which I couldn’t go past. They fit Greg's JLH PCBs perfectly, and as I have some left, it would be terrific if those ever so minor mods could be made the RG JLH PCB so they fit this too.

Alex, you’ve already very generously gifted me 8 x 2.2uf 5 mm pitch MKTs that I’ve swapped out of my Class A HA amp JLHs into the single RG JLHs I’ll use for this PSU build, so keep spares for yourself or others more desperate.

cheers.. jeffc

[Deleted]

it would be terrific if those ever so minor mods could be made the RG JLH PCB so they fit this too.

Hi Jeff
Yes, Greg's PCB takes both sizes, however Will is very short on free time these days, so I was trying to save him from more design work.
Kind Regards
Alex

[jeffc]

Hi Alex,

Yes ..... its tought for us "young guys" still workin' for the man to bring home the bacon.

But there's an offer if I've ever seen one, a man with time on his hands ........ can you draw 2 short black lines on the RG JLH PCB artwork, add pads to suite, and hey presto, done !

cheers.. jeffc

[Deleted]

Jul 6, 2012 3:31:50 GMT jeffc said:

Hi Alex,

Yes ..... its tought for us "young guys" still workin' for the man to bring home the bacon.

But there's an offer if I've ever seen one, a man with time on his hands ........ can you draw 2 short black lines on the RG JLH PCB artwork, add pads to suite, and hey presto, done !

cheers.. jeffc

Hi Jeff
Unfortunately it's not that simple. You need a suitable program, the knowledge to use it, and the ability to also include the additional automated drilling details.
Regards
Alex

[Will]

Unfortunately it's not that simple.

Wot he said

Time is the big constraint, so rejigging the layout of the JLH is a no go at the moment, I'm afraid.

Personally, a single rail version of Greg's layout would be close to perfect, in my eyes anyway.....

[Will]

How much is each? Roughly will do.

The ls devices are sitting at £5.62 inc VAT each, plus share of delivery to me and then onward posting.

[XTRProf]

Jul 6, 2012 8:10:51 GMT Will said:

The ls devices are sitting at £5.62 inc VAT each, plus share of delivery to me and then onward posting.

Oh, not so cheap to buy in bulk to match. I will drop the LS order then and look for bulk elsewhere to buy to match.

So now only the "16" PS PCBs for me. Thanks.

[Will]

Jan 31, 2012 1:05:12 GMT @sandyk said:

Updated Schematic.

Q108 has a 120 ohm emitter resistor.
Q103 has a 200 ohm emitter resistor.
Q101 and Q102 have 200 ohm emitter resistors.
The 1N5819 has been replaced by a SF12 diode.
The voltage readings are only a guide, as they were taken with the cover off,and the balance adjustment was not correct due to this.
Alex

P.S.
Will's new PCB may have different component numbering .
Also, in cold climates, if front end balance can't be readily achieved ,we may need to revert back to using the 1N5819 Schottky Diode due to it's lower forward voltage, and put up with touchier set up of the front end balance.
If the difference obtained is just short of achieving complete balance, then replacing Q108's 120 ohm emitter resistor with a 130 ohm 1% MF resistor MAY get you there without reverting back to the 1N5819.

Hi Alex,

Just doing some prep, and was double checking in preparation for creating the BOM.

In your post, you say resistor feeding the emitter to Q103 is 200R, but is 150R on the schematic. Which is the correct value?

[Will]

Hi Chong,

no problem, they are a bit pricey, aren't they? Straight from the UK supplier as well. www.micross.com

I'll update accordingly.

Jul 6, 2012 10:34:19 GMT XTRProf said:

Oh, not so cheap to buy in bulk to match. I will drop the LS order then and look for bulk elsewhere to buy to match.

So now only the "16" PS PCBs for me. Thanks.

[Deleted]

Jul 6, 2012 11:13:37 GMT Will said:

Jan 31, 2012 1:05:12 GMT @sandyk said:

Updated Schematic.

Q108 has a 120 ohm emitter resistor.
Q103 has a 200 ohm emitter resistor.
Q101 and Q102 have 200 ohm emitter resistors.
The 1N5819 has been replaced by a SF12 diode.
The voltage readings are only a guide, as they were taken with the cover off,and the balance adjustment was not correct due to this.
Alex

P.S.
Will's new PCB may have different component numbering .
Also, in cold climates, if front end balance can't be readily achieved ,we may need to revert back to using the 1N5819 Schottky Diode due to it's lower forward voltage, and put up with touchier set up of the front end balance.
If the difference obtained is just short of achieving complete balance, then replacing Q108's 120 ohm emitter resistor with a 130 ohm 1% MF resistor MAY get you there without reverting back to the 1N5819.

Hi Alex,

Just doing some prep, and was double checking in preparation for creating the BOM.

In your post, you say resistor feeding the emitter to Q103 is 200R, but is 150R on the schematic. Which is the correct value?

Hi Will
I think that the attached schematic was posted a while back when Shaun was building his, although it may have been sent via email to interested parties. .
Kind Regards
Alex

Attachments:

[Will]

ooh, ta!

[Deleted]

By the way, where are you buying (when it happens) the LS devices from?

I did a rearch and came back blank everywhere for buying, just data sheets.

[Will]

Jul 6, 2012 17:02:54 GMT @cjarchez said:

By the way, where are you buying (when it happens) the LS devices from?

I did a rearch and came back blank everywhere for buying, just data sheets.

Hi Chris

I'll get them from Micross who used to be Mintech, where we got the other LS devices from in the other GB's. I got the details of this company from Linear Systems who manufacture the LS devices.

If you type in LS313 or LS352 into the search box of the Micross link, you'll see the price breaks, etc and VAT and the £10 delivery charge needs to go on top. It's certainly easier to get them now, as before I had to get quotes and then pro formas to buy them in

One idea perhaps is for someone in, say, Spain or Australia to contact Linear Systems and see who the country distributor is, and perhaps see if they are a little cheaper?

They are expensive but they do ensure that the best performance is had when the amp is built. Alex had to match mpsa18 and bc550 for both hfe and vbe, which I gather gives few close matches out of hundreds tested. With these LS devices, we get better than close on both counts, in a package.

As a general note, it's worth looking at what Micross sel, as they do have a lot of hard to get stuff, like j5xx and lsk389.

[Will]

Quick idea on costings for the pcbs (using makepcb.com)

Amp pcb = £4.23 each
PSU pcb = £2.00 each

cost share of delivery to me = £0.80 per pcb

so a standard build pack of 2 amp pcbs, 2 psu pcbs with share of delivery is £15.66, plus onwards postage to you.

Once all pcb numbers are know, I'll post final costs and we can get things rolling!

With these costs in mind, please let me know if you want to change numbers NOW, as changing the numbers affects the cost directly.

Also, please let me know how many JLH pcb's you want, if any. Once final figures for these are known, I'll pop that cost up.

PCB spec is as follows:

1.6mm thick
70uM (2oz) tracks, gold finish.
Double sided, silk screen on topside.

[Deleted]

With these costs in mind, please let me know if you want to change numbers NOW, as changing the numbers affects the cost directly.

Hi Will

I'm still fine with my order

Syd

[XTRProf]

For me,


Confirm 16 PS PCBs it will still be.

Btw, Will, can post an actual size layout of the PS PCB here to see what "fat" audiophile parts can go in?

Thanks.

[Spirit]

Hi Will.
My order is great
Could you also put me down for enough JLHs for dual mono please?

Cheers!
Phil