F5 with 2SK2013/2SJ313

[jacco vermeulen]

don't think

400mA times 24V is 9.6W
Means the devices would heat up to >80C + temperature rise of the heatsink. (22.5C ambient)

Keeping the dies under 100C would require a 2C/W heatsink for each output device.
Check for yourself how large the heatsink would be.
(or a 0.33C/W heatsink for 6 devices)

 

[Tea-Bag]

Maybe a 12 or 15vac tranny would do well if you don't want a regulated supply. Just a SWAG.

 

[massimo]

Juma, as described in the Serbian forum, used a Fischer SK 56 (30 x 15 x 4 cm) heatsink and reported a temp rise of 21°C.
That heatsink will suffice to dissipate the 9.6W x 6 without becoming too hot (>50-55°C)

 

[jacco vermeulen]

Means a minimum die temperature of 94C at 25C ambient.
Raise the dissipation to 9.6W and die temperature will reach 110C !
(me head count, do the exact math yourself)

 

[Zen Mod]

 

[juma]

As Jacco noticed, power dissipation was my primary concern when I decided to use cap multiplers to lower the PS voltage to +/-20V DC (the transformer I used is 2x19V AC). Not that these MOSFETs are that fragile, but I don't like running things on the edge - reliability is my fetish, I drive Japanese cars only... Soon I noticed that amp sounds better with cap multiplers so I kept them.

 

[GuidoR]

amp sounds better with cap multipliers

Juma, you convinced me, thanks.

Jacco, as you quoted, I don't think, while you've done the math

 

[Samuel Jayaraj]

I've checked RS, Farnell and Mouser, but I can't find the output Mosfets. Any idea about their availability? Can they be substituted with K1058 and J162? Thanks.

 

[Zen Mod]

ask Zhou Fang

 

[juma]

...Can they be substituted with K1058 and J162?...

It will work, but it won't be the same amp...

 

[Samuel Jayaraj]

Thanks. So I will contact Zhou Fang.

 

[jameshillj]

If that's unsuccessful, you can try "utsource" - they have them, at U$1 each.

 

[Samuel Jayaraj]

Thanks for that information. I have mailed utsource.

 

[samoloko]

Juma

you have lowered power lowering rails to 20 V
Is 400 mA @ 20 V the sweet pot
can power be increased If we add more pairs and use original F5 24 V rails
have you think to do balanced amp

 

[juma]

Juma

you have lowered power lowering rails to 20 V
Is 400 mA @ 20 V the sweet pot
can power be increased If we add more pairs and use original F5 24 V rails
have you think to do balanced amp

It's 400mA per MOSFET = 1.2A per channel. Raising the rail voltage, adding more pairs, bridging, going balanced, SuSy - they are all viable options, but I already found what I like the best.

 

[samoloko]

thx for your reply

can I change original F5 1 pair with 3 pairs 2sk2013/2sj313
power supply Is unregulated 23 V total bias 1.6 A
will I get better sound running with more than 1.2 A

regards

 

[Zen Mod]

go back one page and read ;

it's already asked and already answered

think about dissipation per mosfet

 

[NYCOne]

I have to say, I find this idea very interesting. Are there any other reports listening reviews from people that have replaced the native outputs of the F5 with 3 2sk2013/2sj313?

 

[Zen Mod]

Juma's opinion is enough valid for me

 

[generg]

I put the pieces in Aleph P 1.7 and Pumpkin and had a very good impression, much more detailed.....