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Old 5th September 2010, 01:48 AM   #11
EUVL is offline EUVL  Europe
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The balanced circuit I published is optimised for 6 ohm load, chosen to be midway between 4 & 8 ohm. I have not measured any IRF devices, so I am not going to make any recommendation for those. Maybe you could ask Nelson.


Patrick
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Old 5th September 2010, 08:22 AM   #12
NYCOne is offline NYCOne  United States
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I would be honored of Mr Pass would advise.

If anyone has experience down this path, input would be appreciated. I would be surprised if I was the first person trying to make a balanced F5 with the IRF components.
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Old 16th October 2010, 07:29 AM   #13
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Balanced F5 new question

Is it reasonable to power a balanced F5 using a single supply?
As the ground in F5 concerns the input only, i mean there is no decoupling cap, and as i am the happy owner of several 25v beautiful german potted transformers (from shuro)
I contemplate to do so.
Though, as i will risk expensive matched 2sk 1530/ sj201 and i have no spare, i would prefer to be shure first.
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Old 16th October 2010, 08:16 AM   #14
EUVL is offline EUVL  Europe
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Yes, the advantage of a balanced circuit is that it draws near constant current from the PSU even when drying heavy load. I would not do it any other way (than supplying the two halves with one PSU and one Cap, as you have drawn).

BTW Schuro Tx are not really the best you can get. And single point matched k1530/J201 are not that expensive (about 100 Euros for 8).

But to make full advantage of the balanced circuit, you should consider :

1) dropping voltage to 20V or below and increasing bias current to at least 2A per FET (and watch dissipation max 32W per FET);
2) implementing the 5R degeneration trick on the J74 if you use Toshiba MOSFETs;
3) dropping the MOSFET source resistor value to 0R22;
4) using the Xed version of the balanced circuit.

Nothing new, all published before over the F5 thread.


Patrick

Last edited by EUVL; 16th October 2010 at 08:21 AM.
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Old 16th October 2010, 09:10 AM   #15
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EUVL, since you mentioned it, what's your preference when it comes to transformers?
I'm on the lookout for a couple of projects.
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Old 16th October 2010, 09:12 AM   #16
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Thanks, Patrick, for your fast reply.

I have been following the F5 thread since the begining and ( i believe) I am aware of your recommendations.

Quote:
1) dropping voltage to 20V or below and increasing bias current to at least 2A per FET (and watch dissipation max 32W per FET);
I think you mean per rail.
As i will be using single 25v Ac transformers ( paralleled windings), i will get about 33v DC rail to rail, which corresponds to your schematic.

Quote:
BTW Schuro Tx are not really the best you can get.
Are they so bad? They seem to be silent nevertheless. They are screened too. What is their issue? Regulation?

Last edited by bobodioulasso; 16th October 2010 at 09:20 AM.
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Old 16th October 2010, 09:41 AM   #17
EUVL is offline EUVL  Europe
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Schuro is OK for the price, but they are not using oversized cores for the rating, which is what you want to do for Class A.

We took the plunge and bought a few Piltrons recently.
They are really very well made. Whether they are worth the money is up to you.

Otherwise we use the same supplier as Peter Daniels.
Not perfect (mistakes with wiring now and then), not cheap, but amongst the top 3 we have tried.

And for real audio use, you should not encapsulate with porting compound.

For the balanced F5, you consume 130W. So 500VA minimum.
We use 650VA for ours, per channel that is.


Patrick

Last edited by EUVL; 16th October 2010 at 09:44 AM.
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Old 16th October 2010, 10:03 AM   #18
EUVL is offline EUVL  Europe
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OK, I have a soft spot today.

For those of you who want to build the balanced (Xed) F5 using my circuit (i.e. Toshiba MOSFETs), here is a one-time offer.

If you can :

1) get approval from Nelson for a PCB offer from the DIYA forum;

2) convince the moderators of the forum to take care of the sourcing and sales of the "EUVL Xed-F5" PCB,
in the same fashion as the other single ended F5 Design;

3) find someone who can convert my design from Autocad to Gerber;

4) find someone to volunteer to build the first proto based on the PCB offered
(to debug and to take over answering questions for the building process later),

then you can get that person in (3) to contact me so that I can give him instructions of how to layout the PCB as per my current design, plus component placements and bill of material, etc.

The following preconditions apply :

a) Sales only through DIYA, and profits donated to the forum.
b) I retain the rights to the layout.
So the Gerber files are only known to me and the DIYA forum.

When you are ready, send me a PM.


Good luck and happy building,
Patrick


PS This balanced circuit requires a balanced input signal.

Last edited by EUVL; 16th October 2010 at 10:19 AM.
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Old 16th October 2010, 10:43 AM   #19
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Quote:
Originally Posted by EUVL View Post
We took the plunge and bought a few Piltrons recently.
They are really very well made. Whether they are worth the money is up to you.
I think Plitron = Amplimo in Europe. Please correct me if I'm wrong.
I do have an 800VA Amplimo trafo. They're not cheap (far from) but mine looks and feels beefier than most 1000VA ones I've seen from random suppliers.

As for your offer, I really hope it goes through!
Unfortunately the only help I can offer is to cross my fingers and commit to buy the boards once they become available.

Last edited by TheShaman; 16th October 2010 at 10:46 AM.
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Old 17th October 2010, 12:33 AM   #20
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Quote:
Originally Posted by EUVL View Post

If you can :

1) get approval from Nelson for a PCB offer from the DIYA forum
[/COLOR][/B]
Done.

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