Patchwork Reloaded: Circuit Optimization and Board Layout.

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destroyer X

destroyer X

R.I.P.
Joined 2004
youtube.com/channel/UC9xnp-350vDnDhEpNv_XVxg
I have mentioned your name into my "BiAmp release" video

YouTube - Audio amplifier test - Dx TriAmp

If you dislike that, then just let me know and i will remove your codename (Mjl21193) from the video.

I was saying good things about your amplifier.... i was just fair..do not need to thank me because of that.

- "To Ceasar what belongs to Ceasar..to the Lions what belongs to Lions"

Yeah... the recording resulted awfull (will make another one)...maybe you will dislike your name there because of that.

ahahahahah!

regards,

Carlos
 
MJL21193

MJL21193

Disabled Account
Joined 2007
There are some full power tests further back in this thread (I think). It's in excess of 140 watts into 8 ohms. Running it on a 4 ohm load is fine but make sure there is a good heatsink. 2 ohms is NOT recommended.

The max rail voltage for this (indeed, the voltage it was designed for) is +/-56VDC. To use a lower rail voltage would require changing the frontend cascode voltage divider (specifically R4), R11 to adjust current thru the VAS and R27 to adjust the current thru the frontend. Gain would need to be adjusted also - R26.
 
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MJL21193

MJL21193

Disabled Account
Joined 2007
The current capacity of the amp would be exceeded and the outputs would fail.
Is a 2 ohm load a serious option? This was initially designed for an eight ohm load but will do 4 ohms fine. For a 2 ohm load, rail voltage would need to be drastically reduced.

EDIT: Sorry OS, we posted together.
 
MJL21193

MJL21193

Disabled Account
Joined 2007
454Casull said:
So what is the current capacity, then? Is there no overcurrent protection?

The rails will be fused for each channel, yes.

EDIT: I assume that fast-blow fuses are preferred. What value should they be?
Click to expand...

The fuses are the overcurrent protection - there isn't any built into the amp itself.
I have 4 amp fastblows on my 6 channel:

Picture 285.jpg

That's 2 fuses per channel - one on each rail. None blown yet.
 
A

AndrewT

R.I.P.
Joined 2004
2pair 1943/5200 on +-56Vdc (40Vac 6% regulation transformer +-23500uF Re=0r22) can do ~140W into 8ohm 60degree phase angle
It can manage to drive a moderate reactance 6ohm speaker to about 170W to 180W, if you keep the output devices cool.

4ohm 40degree phase angle is asking too much of the 1943/5200 pair for good reliability.

3r0 is near the resistive load limit and confirms that 6ohm is about the minimum speaker load.

More robust output devices would allow slightly lower load impedances.
 
MJL21193

MJL21193

Disabled Account
Joined 2007
The only other output device that I'd recommend for this are the MJL21193/94. These are practically indestructible.

What is your design goal here? To use these as the power amps for active multi way speakers? If so, you will be hard pressed to drive these amps to overload and retain your hearing.
My good friend Andrew always likes to point out the worst case, the theoretical break point but this doesn't jibe with reality. Reality is that these amps, built as designed will suit your needs. If you are using one amp per driver (real drivers, not the shite you find in cars) you will not be able to damage them.
 
radio

radio

Banned
Joined 2009
MJL21193 said:
I have had several months of listening to the original amp . Although I didn't put it in a case, I used it every time I did any work in my lab. I have had a few different amps to compare to it, mostly DIY, but none have been it's equal, including my Yamaha htr.
This may be due to it's high power - I don't have anything else that can put out more than 100 watts. The difference is mainly in the bottom end - there is more authority to the bass, it seems more solid. This could be a delusion on my part, but I'm usually tough on my creations, not giving credit where it's not warranted.

In any case, I have a six channel amp project planned and I thought I would put my effort to use by using this design for the amp modules. I set about refining the circuit, subtle changes to improve performance, lower distortion. I have changed the output devices to MJL21193/94, as I have many of these and would need 12 of each for the six modules. Other changes that I'll be going through and looking for advice on.

The new schematic:
Click to expand...

Many regards!:)
Scheme amplifiers is excellent! Please give PCB for it!
Question: ate MJL4281A/MJL4302A transistors can be replaced with MJ15003/MJ15004?
Thank you in advance!:cloud9:
 
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