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Old 26th December 2004, 10:06 PM   #611
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Hi Fuling,

Quote:
Originally posted by Fuling
Thanks for the reply!

Seems like I better catch one or two of those transformers before they go out of stock then!

I already have one huge 750VA 2x24V toroid at home that might be useful in the PSU, some 65-70VDC should give about 200W or so I guess.
Smells like fan cooling...

Cheers!
500 VA toroid output:

Click the image to open in full size.

For your application you will probably need a heatsink a little larger than this.

Main heat depends on the bias setting and the overall voltage. If you can abide the slight noise fan cooling does dramatically reduce the heatsink size.

Large fan(s) running slowly to reduce tip speed is best.

Thermal tracking bias is recomended for higher powers.

Best wishes,
Susan.
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Old 26th December 2004, 10:22 PM   #612
Fuling is offline Fuling  Sweden
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Looks good!

For once, fan noise is not an issue!
No living creature would be able to hear a 120mm fan through the sounds we create when we rehe****

Would four pieces of IRFP260N be sufficient here, or do I need more?
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Old 26th December 2004, 10:26 PM   #613
Fuling is offline Fuling  Sweden
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Stupid censorship thing...
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Old 26th December 2004, 10:42 PM   #614
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Hi Fuling,

Quote:
Originally posted by Fuling
Looks good!

For once, fan noise is not an issue!
No living creature would be able to hear a 120mm fan through the sounds we create when we rehe****

Would four pieces of IRFP260N be sufficient here, or do I need more?
One pair of matched IRFP260N should be fine for these power levels.

Bias probably about 250 mA per mosfet to start with as you have a higher supply voltage.

Use a third mosfet for the tracking bias.

What sensitivity, impedance speaker drive units will you be using?

Best wishes,
Susan.
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Old 26th December 2004, 10:56 PM   #615
Fuling is offline Fuling  Sweden
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Hi Susan

One pair seems a little puny for this job, the average power level is quite high when playing bass guitar.
Better safe than sorry I guess.

Havenīt decided on the speaker yet, but Iīm leaning towards a 200 litre bass reflex box with two 96dB 8 ohms 15" drivers.
Should be able to deliver quite impressive SPLīs
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Old 26th December 2004, 11:24 PM   #616
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Hi Fuling

Quote:
Originally posted by Fuling
Hi Susan

One pair seems a little puny for this job, the average power level is quite high when playing bass guitar.
Better safe than sorry I guess.

Havenīt decided on the speaker yet, but Iīm leaning towards a 200 litre bass reflex box with two 96dB 8 ohms 15" drivers.
Should be able to deliver quite impressive SPLīs
Should be VERY impressive.

Each mosfet is rated at 300 watts, 35 amps at 100 degrees centigrade (chip temp) continious, 200 amps pulsed.

Using a pair you are dividing the load across two mosfets. Then with a 2:1 (ish) step down you are trading current for voltage.

Main limitation is the bias level (which will also depend on the wire diameter of the 120 volt windings).

Hope this helps.

Best wishes,
Susan.
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Old 27th December 2004, 02:08 PM   #617
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Default Tube variant

Hello Suzan, all,

Interesting design.
I'm curious about the comparison made with the tubed WE25.
Somewhere in this thread it was mentioned that the design of Suzan can also be made with tubes. I guess the tube must be in a kind of follower configuration.
Alas I'm unable to design this myself.
Any interest of others to give it a try?

Best regards, Arjen.
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Old 27th December 2004, 02:28 PM   #618
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What will be advantage, do it with tubes ? What do you waiting ?
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Old 27th December 2004, 02:58 PM   #619
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Hi Eva,

You asked that before, but it was not answered, yet is very important as there is no NFB.

Cheers .......... Graham.
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Old 27th December 2004, 08:06 PM   #620
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Apologies for that last comment being so out of place.

I have been having terrible probs with my e-mail / Internet connection, with outages of digital signal continuity upsetting my computer.
I was answering Eva's post about playing loud piano music, which somehow appeared as if it was the last entry in this column, and thus I thought that it had been repeated.

Now that I am back on normal line again I see different and normally progressive postings.

Cheers ............ Graham.
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