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Old 18th September 2006, 02:52 AM   #11
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Thanks guys,
I made the PCB followed the image from passdiy.com, so it's better to find the components as guided.

I'll try to find in local markets if these TIP, IRF are available.

Cheers.
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Old 18th September 2006, 03:06 AM   #12
lineup is offline lineup  Sweden
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Quote:
Originally posted by Babowana

IRF610:
Buy all IRF510/ IRF520/ IRF620/ IRF630 /IRF140 /IRF240/ IRFP250N . . .
And take experiment of sound differences from them . . .
Even if these IRF510, IRF520, IRF610, IRF620 all can be used in lower power stages
IRF610 is popular among builders & designers. Including Nelson.
All these 4 MOSFET have slightly different data.

What I think is, the relatively low input capacitance of IRF610 is a little in favour.
In the Datasheet you will see this value called Ciss and is measured in pF.

In short, the input of a transistor with lower input capacitance
is easier to drive for the circuit attached to its input.
Very big MOSFET with higher Ciss ( >2000pF ) needs more bias current
from predrivers or voltage amp stage, in order to keep performance good.

lineup - thinks IRF610 is a good choice for preamps and headphone amps.
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Old 19th September 2006, 11:50 AM   #13
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hi guys,
What type of transformer should I get for this? 30-0-30 VAC ,??VA?

cheers.
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Old 19th September 2006, 05:08 PM   #14
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I rebuild mine 2 weeks ago. I've got a 30+30 250va (4.35 amps) on mine. Sounds better with a higher current transformer.
250va is a lot. Whatever it calls for double it.

Avel-Linberg- $46 from PartsExpress.com.

They are hard to find. Do a search on Avel-Linberg.
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Old 20th September 2006, 02:22 AM   #15
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Would it be too much for it with the transformer of 30-0-30 300VA?
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Old 20th September 2006, 02:36 AM   #16
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Quote:
Originally posted by likeDIY


300VA?

30VA is big enough . . .
50VA is okay . . .
300VA is also okay . . .
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Old 20th September 2006, 02:40 AM   #17
lineup is offline lineup  Sweden
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30 - 30 will give something like
45 - 45 VDC

Transformer VA can never be 'too large' and powerful.
But certainly be too small and weak.

But there are some few drawbacks with overdimensioned trafos.

1. Cost you extra money, even if you maybe get no noticable result, at the output, from it.
this is a waste of money.

2. Bigger trafos gives more electromagnetical radiation around them.
Not the optimal, especially if housed in same case as your amp circuit.

3. Makes amplifier or power supply very heavy to carry, move and transport.

4. Bigger trafos may have more inrush current spikes.
This is when you swtch on amplifier. This one I am not so sure of.
some one may correct me, if I am wrong.


When building a Nelson Pass amplfier, you can 100% count on
his recommendation for transformer is already a bit 'more than normal'.
So there is no real need or significant improvement going beyond this.
But if you do, nothing bad will happen.
If something will change, it probably some very small improvements
in some measurable data.
But hardly something you notice with your 2 sound sensors at both sides of your head.


lineup cant hear you ... but read you
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Old 20th September 2006, 03:24 AM   #18
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Thanks a lot Lineup!
The reason why I ask that because I already got one transformer with that ratings. So it's good that I can reuse.
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Old 9th October 2006, 02:22 AM   #19
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I couldnt find the TIP29 and IRF610 in local markets, can I use TIP31 and IRF620 as replacement?
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Old 9th October 2006, 06:11 AM   #20
Mad_K is offline Mad_K  Norway
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Those transistors will do
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