(AK) classA HA/Preamplifier.

[Deleted]

Too many individual alterations to the basic design by those who don't really know what they are doing is only likely to lead to problems, or at least reduced performance.I would prefer to see this HA constructed initially in it's original form, as Will and Leo have already successfully done, and then changes made AFTER the basic HA is working correctly.If people want to add LIghtspeed attenuators or motorised volume controls,delay circuits etc., then they should do that after ascertaining that the HA is performing correctly first.Alex

Hi Alex

That's my take on things.

i will be building to spec because others have and had no problems.

Yes mods could be made but lets get things WORKING first and worry about add ons later when we know what's what.

take care

[Deleted]

Ok, another daft question...

I have the choice between 0.4w and 0.6w resistors in 0.25w physical size.

Can I get away with 0.4w, as they are a fraction of the price of the 0.6w (here).

cheers

[Deleted]

All resistors can be 0.4W.
For safety reasons you could use 0.6W for the 10 Ohm emitter resistors (the 4 in parallel) but not really needed.

[Deleted]

^^^Okey Kokey!

Cheers Frans.

[Deleted]

Chris
When the PCBs arrive, both Will and myself, and others, will be giving additional construction tips, such as with the 4 x 10R parallel emitter resitors, not having them hard up against the PCB, but spaced several mm above the PCB.
Alex

[Will]

Hi Chris,

As Frans says 0.5W/0.6W are the ones to go for for the two groups of 4x10R resistors. This is the one areas that really should have them.

When it comes to setting the bias for the amp, this is the area you measure to set it, with all that lovely clean class A current.

[Will]

Can everyone buying PCB's please check their email, thanks.

[Will]

ALL the pcbs are here! *phew*





emails out to all who who bought the pcbs.

[Deleted]

Will
They look great !
I look forward to building up a few of those.
They are certainly much easier to use than the original bodgied PCBs, and the onboard Offset Corrector is a nice touch.
Regards
Alex

[Deleted]

Is anyone in the UK planning a Jaycar purchase soon, that they'd be prepared to add other peeps bits to, like Shaun did late last year?

I'm after some PSUs and Low ESR caps.
Happy to pre-pay via paypal.

Cheers,
Chris

[XTRProf]

Jan 16, 2011 13:19:35 GMT @cjarchez said:

Is anyone in the UK planning a Jaycar purchase soon, that they'd be prepared to add other peeps bits to, like Shaun did late last year?

I'm after some PSUs and Low ESR caps.
Happy to pre-pay via paypal.

Cheers,
Chris

Err, you are actually quite restricted in your choice of component sizes although it's very good value for money. I will wait for Will's new PS boards which will be mirror image and with better spacing if you can wait.

[Will]

Jan 17, 2011 10:25:02 GMT XTRProf said:

Jan 16, 2011 13:19:35 GMT @cjarchez said:

Is anyone in the UK planning a Jaycar purchase soon, that they'd be prepared to add other peeps bits to, like Shaun did late last year?

I'm after some PSUs and Low ESR caps.
Happy to pre-pay via paypal.

Cheers,
Chris

Err, you are actually quite restricted in your choice of component sizes although it's very good value for money. I will wait for Will's new PS boards which will be mirror image and with better spacing if you can wait.

You'll miss a good chunk of enjoyable music-listening time if you wait for my PSU board!

I'd crack on a see if maybe one of our Australian friends can help Chris out, or perhaps get some of those PSU units from eBay that Jeff linked to.

[Deleted]

Jan 17, 2011 10:25:02 GMT XTRProf said:

Jan 16, 2011 13:19:35 GMT @cjarchez said:

Is anyone in the UK planning a Jaycar purchase soon, that they'd be prepared to add other peeps bits to, like Shaun did late last year?

I'm after some PSUs and Low ESR caps.
Happy to pre-pay via paypal.

Cheers,
Chris

Err, you are actually quite restricted in your choice of component sizes although it's very good value for money. I will wait for Will's new PS boards which will be mirror image and with better spacing if you can wait.

Chris
Do you have a PCB drill so that you can relocate 4 PCB holes to accomodate the physically larger caps such as 2,200uF 35V Panasonic FCs ?
The rest of the parts with those kits are quite usable, as you don't need bloody big red 100uF caps on stilts .
Alex

P.S.
It seems rather unfair to me, to be pressuring Will to hurry up with different PSU PCBs when the Jaycar PSU PCBs are quite usable with a couple of minor modifications.

[Deleted]

Cheers folks, I have a PM that came to my rescue.

Chris
Do you have a PCB drill so that you can relocate 4 PCB holes to accomodate the physically larger caps such as 2,200uF 35V Panasonic FCs ?
The rest of the parts with those kits are quite usable, .
Alex

Alex, I will be receiving some Jaycar PSUs soon enough and yes, I do have a drill press and pcb drill bits.

as you don't need bloody big red 100uF caps on stilts

;D you're a wicked man.

[Deleted]

Err, you are actually quite restricted in your choice of component sizes although it's very good value for money. I will wait for Will's new PS boards which will be mirror image and with better spacing if you can wait.

Hi Chris

to be fair the Jaycar kits are pretty good for the money and I've had no problems fitting the larger psu caps. i also changed the 100uf and 10uf caps to 25v just to keep things safe and with a few bits of creative soldering it all fitted nicely.

Hi Chong

IMHO I've not really found in the past that those caps far back in the reg make much difference to the sound but my ears are getting on a bit so i may be wrong. in my experience the last cap (on the JLH in this case) does affect the sound much more than the first(a reg is only as good as the last cap type stylee) so it may be a good place to start with the expensive stuff. I've had my Jaycar regs and JLH's cooking for the last few weeks now and it's rock solid.

as i say i may have got things totally wrong but it's just a thought.

by the way Frans got it right with the need to load the PSU when testing. varying the load and making sure that the output voltage stays put just confirms that the reg is happy and saves any tears when connecting it up to the signal boards.

again just IMHO

take care

[XTRProf]

Jan 17, 2011 21:41:20 GMT @sandyk said:

Jan 17, 2011 10:25:02 GMT XTRProf said:

Err, you are actually quite restricted in your choice of component sizes although it's very good value for money. I will wait for Will's new PS boards which will be mirror image and with better spacing if you can wait.

Chris
Do you have a PCB drill so that you can relocate 4 PCB holes to accomodate the physically larger caps such as 2,200uF 35V Panasonic FCs ?
The rest of the parts with those kits are quite usable, as you don't need bloody big red 100uF caps on stilts .
Alex

P.S.
It seems rather unfair to me, to be pressuring Will to hurry up with different PSU PCBs when the Jaycar PSU PCBs are quite usable with a couple of minor modifications.

Oh, actually I prefer a bigger size than the Tonerex 2,200uf 42VDC that I'm using now. I'm thinking of 4,700uf. No matter how much drilling till the cows come home and twisting your brain until you landed up in hospital, that wouldn't fit.

Again, wrong deduction. I had said it's for testing purpose for the red caps on "stilt" and whatever soldered in. It's not the final form yet. See here:

So just solder and in test form ............

Also, don't need to pressure anyone. As I said, if anyone can wait.

[XTRProf]

Jan 18, 2011 11:10:23 GMT @shaun said:

Hi Chong

IMHO I've not really found in the past that those caps far back in the reg make much difference to the sound but my ears are getting on a bit so i may be wrong. in my experience the last cap (on the JLH in this case) does affect the sound much more than the first(a reg is only as good as the last cap type stylee) so it may be a good place to start with the expensive stuff. I've had my Jaycar regs and JLH's cooking for the last few weeks now and it's rock solid.

as i say i may have got things totally wrong but it's just a thought.

by the way Frans got it right with the need to load the PSU when testing. varying the load and making sure that the output voltage stays put just confirms that the reg is happy and saves any tears when connecting it up to the signal boards.

again just IMHO

take care

Hi Shaun,

I partially agreed with your statement on boutique capacitor usage. But I totally agreed that the last link, whatever or Vreg before the sound amplification device does make a very audible improvement. I was modifying my MF X-Dac V3 sometime back and took out all the caps that I feel were unneccesary. What shocked me most was when I placed back the 0.1uf just after the Vregs, very close to the analog and digital sections, and the sound was audibly improved. . Yeah, when we use "better" caps there, the sound will change as well. Might not be better, as that's subjective and individual, but the sound will change audibly.

Also, although not to the same magnitude, when I replaced the very first stage downstream PS smoothing caps for the analog section from 2,200uf to 12,000 uf Elna Audio caps (I think as I can't remember correctly as it had been sometime already), the sound became more wholesome and fuller like in LIVE music. Somewhat similar effect went for the digital section PS smoothing caps downstream where I just replaced the 2,200uf to the same value with BG. But the BG, as expected from many same reactions on them, gave a brighter presentation with their inclusion. Anyway, from a highend angle that I'm coming from .........

Anyway, there is no right or wrong in this hobby. It's just what is righter for us. It's good that you discussed it here and shared your opinions on the subject matter for people to also give their opinions and experiences in a cultured way. It's what a great forum is all about.

I also agreed with Frans from the perspective of prototypes when using the test resistors. I have no argument on that. Sometimes, the other sections of a prototype product are being designed and built elsewhere or from different companies. So how to wait for those to come to test in "full uniform"? I had worked in a company with R&D facilities before and seen the design engineers doing those things. It's Groupe Schneider, a famous French company along the line of ABB. But I feel that having done some measurements with a DMM with the Jaycar PSU, it should be A-OK.

Heh, heh, heh .........., tonight will have sometime to fine tune the Jaycar to correct V as boss is away for the whole week. Hip, hip, hurrah!




Cheers!

[Deleted]

Oh, actually I prefer a bigger size than the Tonerex 2,200uf 42VDC that I'm using now. I'm thinking of 4,700uf. No matter how much drilling till the cows come home and twisting your brain until you landed up in hospital, that wouldn't fit.

Is it a good idea to directly load a small VA transformer with such a high value of capacitance immediately after the bridge rectifier diodes.? 1,000uF or 2,200uF would be more commonly used with a transformer of that VA and circuit load requirements.

[XTRProf]

Jan 19, 2011 2:45:11 GMT @sandyk said:

Oh, actually I prefer a bigger size than the Tonerex 2,200uf 42VDC that I'm using now. I'm thinking of 4,700uf. No matter how much drilling till the cows come home and twisting your brain until you landed up in hospital, that wouldn't fit.

Is it a good idea to directly load a small VA transformer with such a high value of capacitance immediately after the bridge rectifier diodes.? 1,000uF or 2,200uF would be more commonly used with a transformer of that VA and circuit load requirements.

Ok, noted. Curious, 4,700uf calls for what recommended VA traffo? Teach me .......... Thanks.

[Deleted]

Jan 19, 2011 3:03:23 GMT XTRProf said:

Jan 19, 2011 2:45:11 GMT @sandyk said:

Is it a good idea to directly load a small VA transformer with such a high value of capacitance immediately after the bridge rectifier diodes.? 1,000uF or 2,200uF would be more commonly used with a transformer of that VA and circuit load requirements.

Ok, noted. Curious, 4,700uf calls for what recommended VA traffo? Teach me .......... Thanks.

Chong
A general rule of thumb would be 2,000uF per amp,which is why I used 2 x 2,200uF in parallel in the 12V 2.5A PSU project. Although I would be interested in Frans take on this subject.
Alex

[XTRProf]

Jan 19, 2011 3:22:48 GMT @sandyk said:

Jan 19, 2011 3:03:23 GMT XTRProf said:

Ok, noted. Curious, 4,700uf calls for what recommended VA traffo? Teach me .......... Thanks.

Chong
A general rule of thumb would be 2,000uF per amp,which is why I used 2 x 2,200uF in parallel in the 12V 2.5A PSU project. Although I would be interested in Frans take on this subject.
Alex

Great! Thanks for loading that into my small computer database in the head ............

[XTRProf]

For the latest iteration of the JLH, for the non CL version, which components can be ommitted? Based on Build BOM v1.1, is it only R12 and Q6? After join across start of R12 to end of Q6 (the purple link), as in circuit diagram, with the rest of the components as BOM valuation? Since this will be a JLH for +/- 20 VDC, all caps must obviously be at least 25 VDC for safety factor reason if discounting all the V drop across circuit. I do understand the caps of 4,700uf can be at 10 VDC after voltage drop at that position.

[Deleted]

Jan 19, 2011 6:19:03 GMT XTRProf said:

For the latest iteration of the JLH, for the non CL version, which components can be ommitted? Based on Build BOM v1.1, is it only R12 and Q6? After join across start of R12 to end of Q6 (the purple link), as in circuit diagram, with the rest of the components as BOM valuation? Since this will be a JLH for +/- 20 VDC, all caps must obviously be at least 25 VDC for safety factor reason if discounting all the V drop across circuit. I do understand the caps of 4,700uf can be at 10 VDC after voltage drop at that position.

Chong
I don't have that BOM in front of me,
but the omitted components for the non CL version.are the base and emitter resistors of the CL transistor, and the transistor itself.(1.8K and 1 ohm ?)
The 4,700uF low ESR caps can even be 6.3V rated as there is only approx. 600mV across them.
The Class A HA DOES use the CL section. The resistors can be 1.8K for the CL base, and 1.0 to 1.5 ohms for the emitter resistor.
1.5ohms can be used because each JLH supplies only half the current of the original design due to using a JLH for each channel.
Alex.

[XTRProf]

Jan 19, 2011 6:35:02 GMT @sandyk said:

Jan 19, 2011 6:19:03 GMT XTRProf said:

For the latest iteration of the JLH, for the non CL version, which components can be ommitted? Based on Build BOM v1.1, is it only R12 and Q6? After join across start of R12 to end of Q6 (the purple link), as in circuit diagram, with the rest of the components as BOM valuation? Since this will be a JLH for +/- 20 VDC, all caps must obviously be at least 25 VDC for safety factor reason if discounting all the V drop across circuit. I do understand the caps of 4,700uf can be at 10 VDC after voltage drop at that position.

Chong
I don't have that BOM in front of me,
but the omitted components for the non CL version.are the base and emitter resistors of the CL transistor, and the transistor itself.(1.8K and 1 ohm ?)
The 4,700uF low ESR caps can even be 6.3V rated as there is only approx. 600mV across them.
The Class A HA DOES use the CL section. The resistors can be 1.8K for the CL base, and 1.0 to 1.5 ohms for the emitter resistor.
1.5ohms can be used because each JLH supplies only half the current of the original design due to using a JLH for each channel.
Alex.

Err, the circuit diagram and BOM numbering of V1.1 is not accurate. Ok, based on what you said then omission for non CL version from the BOM perspective (not the circuit numbering perspective) are:


R1 1R 0.5W
R2 1.8k
Q1 2SA1930 or 2SC5171
D1 and D2 (as they are part of the CL section) 1N4148


BTW, I don't quite understand. You just said that the AHA NEEDS the CL. How come? I thought as long as we have the 317 and 337 Vregs upstream to limit the surge current of the JLH, the CL can be omitted? I don't like the CL in if possible.

[Deleted]

BTW, I don't quite understand. You just said that the AHA NEEDS the CL. How come? I thought as long as we have the 317 and 337 Vregs upstream to limit the surge current of the JLH, the CL can be omitted? I don't like the CL in if possible.

Chong
All made by myself, Will and Leo have included the CL.
I felt that it sounded better with it.It would also act a little like an additional small RC filter.Also, it gives the HA/preamp a small start up delay which can reduce or even eliminate start up thumps/plops.
I suggest you build it using the CL, and then play around without it after you are satisfied that it is working to your expectations.
Alex