Hiraga 20W class A

[Glogov_Kolac]

Do anyone who build this amp can tell me something about resistors in PSU (CRC filter) and how this resistor improves the sound. Also I'm interesting for PSU voltage. I'am using about 18.5 VDC and constantcurent draw of 1.3A.

[njepitt]

Originally Posted by sandyhooker

The parallel resistor is no big deal.The resistance at that point is 470 ohm 5 watt which could be a combo of two 3watters. The rail caps are a simple refinement which may make little or no difference in performance.

I agree that these are no big deal (this is what I meant by "trivial"...). By "that point" you mean R11/R12 and R13/R14, right? If so, then this is half the resistance in the original, suggesting that you could easily use these boards with the original voltages by putting just one of the resistors, and still put the second one in and try increasing the rails later... (or the other way around, I guess...)

I'm not sure why I 'm doing this project but if for no other reason I can make a comparison with my ZEN(s).

As chance would have it, I am doing a mini-aleph-j with BF862 to do the reverse comparison, among other things.... (check out

Is a mini-Aleph using BF862 possible?

to see all the good advice I received, if you're interested.)

There is no bias or other info included with this package . I'm eyeing a cap multiplier for power but also considering CLC.Can do about 68,000uf without spending a dime. There is no reason why I'd have to adhere to 22v rails and may decide not to .Have a 24vct 10 amp trans sitting idle.

Again thanks for the help

Original bias is around 0.5 A, if memory serves (Dan?) but with the higher rails and lower resistance values maybe the kit is designed for higher? I use a cap multiplier with all of mine, which has worked well, although YMMV.

As a final thought, I agree with Dan that maybe this should be moved to the other thread - since it plainly is about the Monstre and not the Hiraga 20W in this thread's title...

Cheers

Nigel

[Pano]

The resistors in the PSU are part of the line noise filter. The work as a sort of low pass for line noise. You will notice that there is one large cap (per rail) ahead of the resistor and 2 after. As the resistor will limit current a bit, the big caps downstream help to supply peak current.

As far as I remember, the amp design does not have a very good PSRR, so a lot of effort and care need to be taken to keep noise low. Thus the copper bars in the PSU and very symmetric wiring.

Running at 18.5V is going to take some important recalculation of bias. It's easy to go too far and burn up the amp. I know!

[njepitt]

Originally Posted by Glogov_Kolac

Do anyone who build this amp can tell me something about resistors in PSU (CRC filter) and how this resistor improves the sound. Also I'm interesting for PSU voltage. I'am using about 18.5 VDC and constantcurent draw of 1.3A.

Which amp are you building? Le Classe A 20W, or Le Monstre 8W?

Originally Posted by panomaniac

...Running at 18.5V is going to take some important recalculation of bias. It's easy to go too far and burn up the amp. I know!

If Glogov_Kolac is building the 20W Classe A then 18.5V is pretty normal... the original article gives +/- 19 to 21 volts... Bias is given as 0.8 to 1A. I wonder if this thread is starting to get confused between these two amplifier designs.

Cheers

Nigel

[Glogov_Kolac]

This thread is about 20W version. My amp is one of theese with BD139/140 and BD249/250 transistors.

[Pano]

Originally Posted by njepitt

I wonder if this thread is starting to get confused between these two amplifier designs.

Yes! Well at least I was.

You are correct, sir.

[danieljw]

Hi Guys,

Le Monstre uses 0.5-0.6A bias.

Le class A 20W uses 0.8-1.5A bias depending on version

CRC filter in Le class A 20W is as panomaniac says.

hope this helps

-Dan

[sandyhooker]

Originally Posted by njepitt

I agree that these are no big deal (this is what I meant by "trivial"...). By "that point" you mean R11/R12 and R13/R14, right? If so, then this is half the resistance in the original, suggesting that you could easily use these boards with the original voltages by putting just one of the resistors, and still put the second one in and try increasing the rails later... (or the other way around, I guess...)



As chance would have it, I am doing a mini-aleph-j with BF862 to do the reverse comparison, among other things.... (check out

Is a mini-Aleph using BF862 possible?

to see all the good advice I received, if you're interested.)



Original bias is around 0.5 A, if memory serves (Dan?) but with the higher rails and lower resistance values maybe the kit is designed for higher? I use a cap multiplier with all of mine, which has worked well, although YMMV.

As a final thought, I agree with Dan that maybe this should be moved to the other thread - since it plainly is about the Monstre and not the Hiraga 20W in this thread's title...

Cheers

Nigel

Oddly I'm doing a Hiraga thing ,have mini-aleph and am somewhat involved with BF862 and have been in touch with the same Serbian High Tech Mafia .
Would be interested in your take with your Hiraga.

[njepitt]

Originally Posted by sandyhooker

Oddly I'm doing a Hiraga thing ,have mini-aleph and am somewhat involved with BF862 and have been in touch with the same Serbian High Tech Mafia .
Would be interested in your take with your Hiraga.

Hi Sandy,

To avoid polluting this thread with stuff which is off-topic perhaps we could put discussion of the mini-aleph-j stuff in the thread I mentioned above. (It sounds terrific...)

By my "take" do you mean my (subjective) comparison of sound of the two? Delighted to talk about any of this stuff, but I should point out that my Hiraga 20W has been retired in favor of the Pass F5 in the living room (main rig) for a while now, so I can only compare with the Le Monstres, which are farther from the original design. This might also be better in the other thread, since it doesn't really have anything to do with the amp in the title of this one.

Cheers

Nigel

[whitesnake]

Hi, guys! What do you think about the scheme, it is good?
What do you think about the electronic components enclosed in red on the scheme in my post?

I think these electrics elements limit the ability of the amplifier. What do you think about this?

Do you think that, they are only for the limited bandwidth and they are necessary?

What happens if we remove it?