(AK) classA HA/Preamplifier.

[pagan]

Hmmm, I can see this escalating if we're not careful. Especially as No2 Son

Will and Robert.

Yes, yes, yes.
It's the kids toys.
we believe you ;D

[Will]

"Dad, can you help me build this?"

"Oh, If I really have too"

[Will]

On-topic, one thing that I would like to point out, is that the file I've put up to make the SC Class A, as a head-amp/preamp, and including the LTP mod, will NOT make the 15W speaker amp. This is because I have removed unused traces.

If you do want to to make the 15W speaker amp, RCS Radio in Sydney sell the board.

You can guess who to ask if you are etching the board for the 15W amp.

[jonclancy]

Latest "Big Cap" pre-proto version of the Mini-JLH PSRR are drilled up. Will be stuffed next week and pics to follow.

[Will]

I wont have chance to make my JLH boards this weekend (away camping with my boys, what more could I want for Father's Day?) so I decided to connect up the SC Class A HA to the one in my SCHA.

Holy frelling chuffing nora! How easy is it to forget the difference that these boards make?!?

This HA doesn't just sound , it sounds..


I tried a variety of tracks and music styles, and they all captivated me for different reasons.

Madonna - Music - Heavily produced, and can sound mashed together on my Pimeta, but on the SCCLAHA (bless you) all the different electronic instruments were separate entities, working together to make your fingers and feet tap along with the beat. The bass was phenomenal, almost overpowering, although not blending into a single 'thump' 'thump'. And this from a pair of K701. It almost made Madonna look younger again, but not quite! Lots of 3D sound stage effects in the mix.

Flobots - Never had it - Guitar, bass guitar and drums working together to keep you grooving in your seat. And then the lady in the group starts singing. Oooh beautiful. Nearly a slight spanner effect. Again music coming through the headphones, not bass or midrange. The band are in front of you, playing just for you.

Depeche Mode - World in my eyes - More electronica, but possibly normal production. First thought is that there is a least another 6 layers of detail that I've not heard before. Dave thingies vocals have lots of echo and you can hear the vocal track being brought into the mix. Again, wonderful presentation.

Xenuphobe - 4 billion Years - Utterly, Utterly sublime. The drums are spacious, the guitar directly hot-wire into your sole as it sings and relaxes you. Quite noticeable that the production is not the best, but the emotion in the music soothes away any concerns.

Dire Straights - Private Investigations S-BR-E - More of the above. Captivating from the start, with you sitting waiting in anticipation for each note from Knoppy's guitar. Investi....gay..shun indeed.

I could go on, Metallica - Master of Puppet 24K DCC recording, Goreckis -3rd Symphony, BT - This Binary Universe and Kings X - Ear Candy -- All good.

The SC Class A HA presents the music is a clear, detailed, powerful and authoritative way. If the music requires delicacy, there is a gentle touch. If it's supposed to have you dancing around the room, you better have a long lead on your headphones. Technically correct presentation, but with emotion as dictated by the song.

Thanks to Alex and Leo for their help in building this amp. Although more challenging than the SCHA, the work and effort I had to put into building this amp (and hopefully some of my posted working will help others) is worth every single moment.

All that is left is to buy a nice case, and get it boxed up. Then I can sit down and listen to some more beautiful music, which is what it's all about.

[Deleted]

And then the lady in the group starts singing. Oooh beautiful. Nearly a slight spanner effect.

Will

? ? ?
Are you saying that her voice almost tightens your nuts ?
Alex

[Spirit]

Yeah... I'm nuts. I think I'll definitely build one of these at some point when I return ;D

BT, Xenuphobe, Depeche Mode... yeah... good taste Will

Glad to hear it's sounding awesome

I'll pick up your caps next friday - after all my exams. Hopefully get them in the post same day too.

Enjoy the camping mate

[Will]

Alex, knew that you'd get that reference!

Phil, no worries about the caps, you concentrate on your exam, MUCH more important! But thank you.

If there is enough demand, I'll be happy to run another group buy for the LS devices. Might be worth keeping in mind any other rare beasties that Linear Systems make that people may want. Mintech have been very helpful so far, so it wont hurt to ask.

[Deleted]

Will
In my early days with Postmaster Generals Department (Telstra) we also had the "Complaints/Fault reporting telephonists in the same building as the Technical Staff. One of the telephonists, Jeanette, had the nickname of "Spanner"
Alex

[Will]

Sound like the lady had similar attributes to a woman who worked in an automotive factory I was an engineer at. Slim, blond hair,great legs, very attractive and always wore fitted business suits, plus stockings (to the trained eye).

We had three presses manufactiring the interior door trims for a family car, with big production boards hung over them, showing production target, actual produced and scrap rate.

Every time she walked down the length of the factory, the scrap rate rose by at least 10%!!

[Will]

Again to help people out, here is the components I used for the DC offset corrector.

Again, I've left out the resistors. All these parts fit the DC offset board I've made available in this thread.

I used 100nF cap I had kicking around, but the part listed below should fit perfectly well.

AD744 Farnell 9604847
100uF 25V caps Farnell 1219466 (same as used for supply rail decoupling on the amp boards.
1uF film Rapid 10-2228
3.3uF film Rapid 10-2202
100nF film Rapid 10-2216

HTH!

[Deleted]

Jun 25, 2009 19:23:19 GMT Will said:

Again to help people out, here is the components I used for the DC offset corrector.

Again, I've left out the resistors. All these parts fit the DC offset board I've made available in this thread.

I used 100nF cap I had kicking around, but the part listed below should fit perfectly well.

AD744 Farnell 9604847
100uF 25V caps Farnell 1219466 (same as used for supply rail decoupling on the amp boards.
1uF film Rapid 10-2228
3.3uF film Rapid 10-2202
100nF film Rapid 10-2216

HTH!

Will
Many other FET input singles may be useable in place of the AD744. I had quite a few of them at the time, and they worked well in that application.
Alex

[Will]

May 10, 2009 5:01:50 GMT FritzS said:

Have anyone a idea for a DC protection with a relay - but for HA use .... threshold abut +- 5 .... 10 mV

This is one thing I miss

David White construct one for his WNA, but I found no schema about.

Just found this, which apparently has been kicking around for a while
[urlhttp://www.amb.org/audio/epsilon12/[/url]

It protects at DC levels of 70mV or above.

I dare say that some of the cleverer souls here would be able to comment on what component values to change to enable a higher or lower shut off level.

How's your build going, Freidrich?

[Will]

For those people that will be wanting JLH PSRR boards, Jon Clancy is currently seeking interest in the Universal Mini PSRR, an update of the JLH PSRR.

rockgrotto.proboards.com/index.cgi?action=display&board=786345&thread=4333&page=1

[Will]

OK, the first few people have had their components through, so to prevent any potential problems in fitting them, here is a quick pictorial.



As you can see, there is some yellow heatshrink on the legs of my LS313/352. Also notice the tab, indicating orientation on the board. Now, although I've only insulated one leg, I suggest that you insulate all three on the side that needs re-arranging.



Now, the emitter legs of both the 313/352 are fed from the same sides of the board, so the legs of the devices have to be swapped over, without them touching. For this you'll need some heatshrink of the correct diameter. I've left the heatshrink off in the photos, for clarity.

Place the heatshrink on the legs that need to be bent and shrink it down. Be careful not to cook the components! Once you have done this, bend the legs as shown. Again, note the tab orientation.





The components are now ready to fit.

Hope this helps!

And yes, I know that some of the components are wonky! They'll get straightened soon enough.

[Will]

First fit into the case.



Please ignore my tat in the background!





Just enough room for the JLH PSRR boards!

The transformers are to be housed in a seperate diecast aluminium box, and hidden out of site. It'll contain two transformers, one per channel.

Of course, normal people would build it with one transformer, one PSU, one JLH PSRR which then feed both boards!

[Deleted]

Will
When you fit the 2 JLH boards, I would be interested to hear your impressions of initially using a single JLH to supply both channels, then an individual JLH for each channel.
So far, I have resisted the temptation to use dual JLHs, as I always seem to have a need elsewhere for one of them.
Alex

P.S.
Don't forget to give the JLHs >48 continuous run in before serious listening.

[Will]

Miguel,

Thanks for the compliment. I'm quite pleased with how it has turned out. I had to use a local machine shop to counter bore the volume knob, but the rest is my own handy work! Given that there is some resonance in the case top and bottom panels, I may use a strip to damp it down, although that would be after any damping of drives etc.

Alex,

I'll do a compare and report back. As the new JLH boards need manufatcuring and such, it'll be at least 4-5 weeks before I get to that stage. It'll be nice to get this part of the casework finshed.

[FritzS]

As you can see, there is some yellow heatshrink on the legs of my LS313/352. Also notice the tab, indicating orientation on the board. Now, although I've only insulated one leg, I suggest that you insulate all three on the side that needs re-arranging.



Now, the emitter legs of both the 313/352 are fed from the same sides of the board, so the legs of the devices have to be swapped over, without them touching. For this you'll need some heatshrink of the correct diameter. I've left the heatshrink off in the photos, for clarity.

Which dual BJT did you use manufactored by Philips?
Did you use the first you get from me?

How's your build going, Friedrich?

I hope I have more time in autumn ;D

You use a nice case - from where you get it?

[Will]

Hi Freidrich,

Those are the LS devices I had from yourself. It actually says Philippines. They are same as the units we got in the group buy.

The case is a Modushop one www.modushop.biz/ecommerce/cat063_l2.php?n=1, 230mm deep. I ordered two, one for the amp, another for my Buffalo, which got me a little discount.

Talking of discounts, I noticed on another forum that they had organised a group-buy of Modushop cases. They had managed to get a 25% discount, up to 30% if numbers were high enough. Just a thought...

[FritzS]

Those are the LS devices I had from yourself. It actually says Philippines. They are same as the units we got in the group buy.

my mistake - I read PHIL.... and think about PHILIPS

[Deleted]

Jul 19, 2009 16:16:18 GMT FritzS said:

Those are the LS devices I had from yourself. It actually says Philippines. They are same as the units we got in the group buy.

my mistake - I read PHIL.... and think about PHILIPS

Friedrich
When I saw the larger can, and those letters, I initially thought the same !
Alex

[PinkFloyd]

Jul 20, 2009 8:14:17 GMT @sandyk said:

Jul 19, 2009 16:16:18 GMT FritzS said:

my mistake - I read PHIL.... and think about PHILIPS

Friedrich
When I saw the larger can, and those letters, I initially thought the same !
Alex

When I saw "Phil" I automatically thought of Philadelphia cheese

[cyteen]

Thinking about the DC offset correction, many people say "I don't like servos". Steve Dunlap over on DIYaudio posted this:

"This is not a conventional servo as it will have no effect on either the low frequency bandwidth or on the sound. The amp will still pass a perfect 1Hz square wave. It will correct for small DC inputs, but will amplify DC if the input level is high enough."

www.diyaudio.com/forums/showthread.php?postid=1726425#post1726425
www.diyaudio.com/forums/attachment.php?s=&postid=1726425&stamp=1233098512

An thoughts about this as an alternative solution?

[Deleted]

cyteen
The simple servo as shown at DIYAudio will certainly work, but is unlikely to be as effective.
One of the reasons for the double capacitance-resistance network at the input was to eliminate any switching clicks/noise caused by the use of an attenuator, insted of the continous action of a normal potentiometer. There is also an additional output filter to reduce any added noise from the opamp itself.
The offset corrector was found in use, to be quite transparent when compared with the preamp of a friend which was otherwise almost identical, but did not use an offset corrector, or (at the time) a 24 position attenuator.

Alex