Questions

jrgoswick · 29th August 2010, 11:54 PM

Doing a mod on a pair on M-501 Onkyo's. I like the amps solo, but need more power. Time to make them monoblocks. I want to shoe them into the same chassis. I'm wanting about 250 to 300wpc. Here are the questions:

1)-use the factory transformers or Krell it out? I'm thinking use the factory ones, saves coin(for other parts) and the output voltage is within spec for the outputs(which will also be used).
2)-Caps-I'm thinking 35,000 to 40,000uF in the primary banks(two amps here) and stacking 1500 to 2000uF at EACH output device. Any thoughts on this
3)-Dual brigdes(4 total)-will help with inrush currents and seperation. ANY thoughts on this appreciated.

I'm using all four pairs of outputs paralleled per side. I've got another pair per side I could add, should I? Only benifit I can see is the ability to drop more current from the power supply for dynamics.

As far as protection, I'm thinking about fusing the outputs rails, and using a 3 second delay for main rail engagement to allow the large banks to stabilize before the outputs switch to an active state.

This is my first DIY at this level(not really a DIY, more of a frankenstien). Please don't fire me to hard, I have high hopes for this project(I've been working on this for about 3 years-gathering parts, studying schematics, ect).

Nelson Pass · 30th August 2010, 11:17 PM

Are you going to be able to fit all this stuff in that chassis?

jrgoswick · 31st August 2010, 02:17 AM

Yeah, it'll fit.

Nelson Pass · 1st September 2010, 09:26 PM

1) Strictly your choice

2) You can stack caps at each device, but they might get
hotter there, and the advantage might not be so great
depending on how you ground them - If you run the ground
wire back to the supply, then it's not so local. If you
ground locally, you might run into noise issues.

3) Quad Bridges if you have dual secondary windings and
four separate cap banks, two for each channel.

jrgoswick · 2nd September 2010, 06:52 AM

1)-The factory transformer has 3 output taps. Effectively two secondaries with one secondary tapped for a slightly lower voltage(35V,68v, and 80v). This will save coin for other parts that will be needed.
2)-Should there be a couple of large caps or a bunch of smaller ones. Smaller ones will give a lower ESR, larger ones will have less real estate and higher ripple(I think that's correct).
3)-Quad bridges it is!

29th August 2010, 11:54 PM	#1
jrgoswick diyAudio Member Join Date: Jul 2010 Location: Arkansas	Questions Doing a mod on a pair on M-501 Onkyo's. I like the amps solo, but need more power. Time to make them monoblocks. I want to shoe them into the same chassis. I'm wanting about 250 to 300wpc. Here are the questions: 1)-use the factory transformers or Krell it out? I'm thinking use the factory ones, saves coin(for other parts) and the output voltage is within spec for the outputs(which will also be used). 2)-Caps-I'm thinking 35,000 to 40,000uF in the primary banks(two amps here) and stacking 1500 to 2000uF at EACH output device. Any thoughts on this 3)-Dual brigdes(4 total)-will help with inrush currents and seperation. ANY thoughts on this appreciated. I'm using all four pairs of outputs paralleled per side. I've got another pair per side I could add, should I? Only benifit I can see is the ability to drop more current from the power supply for dynamics. As far as protection, I'm thinking about fusing the outputs rails, and using a 3 second delay for main rail engagement to allow the large banks to stabilize before the outputs switch to an active state. This is my first DIY at this level(not really a DIY, more of a frankenstien). Please don't fire me to hard, I have high hopes for this project(I've been working on this for about 3 years-gathering parts, studying schematics, ect).

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30th August 2010, 11:17 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	Are you going to be able to fit all this stuff in that chassis?

31st August 2010, 02:17 AM	#3
jrgoswick diyAudio Member Join Date: Jul 2010 Location: Arkansas	Yeah, it'll fit.

1st September 2010, 09:26 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	1) Strictly your choice 2) You can stack caps at each device, but they might get hotter there, and the advantage might not be so great depending on how you ground them - If you run the ground wire back to the supply, then it's not so local. If you ground locally, you might run into noise issues. 3) Quad Bridges if you have dual secondary windings and four separate cap banks, two for each channel.

2nd September 2010, 06:52 AM	#5
jrgoswick diyAudio Member Join Date: Jul 2010 Location: Arkansas	1)-The factory transformer has 3 output taps. Effectively two secondaries with one secondary tapped for a slightly lower voltage(35V,68v, and 80v). This will save coin for other parts that will be needed. 2)-Should there be a couple of large caps or a bunch of smaller ones. Smaller ones will give a lower ESR, larger ones will have less real estate and higher ripple(I think that's correct). 3)-Quad bridges it is!