Sony vFET Amplifier Part 2

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#2,681
Correct, front panel LED wiring. They're color coded, red for positive PSU voltage, blue for negative PSU voltage. They're a visual reminder for the polarity of the sides/sections of the PSU, which hopefully helped avoiding wiring mistakes upon assembly. Guess I'll find out tonight 🙂
 
#2,682
Hi Jlithen,

Do you know the Idss of your jfets? Assuming you need no more than 5V
for Vgs to bias up the mosfets then you should be ok if the Idss is over 7mA.

If the Vgs voltage needed is actually close to 4V then even the minimum
BL/B grade Idss of 6mA should work.

Hopefully others can share their experience.

Cheers,
Dennis
 
#2,685
Dennis Hui said:
Hi Jlithen,

Do you know the Idss of your jfets? Assuming you need no more than 5V
for Vgs to bias up the mosfets then you should be ok if the Idss is over 7mA.

If the Vgs voltage needed is actually close to 4V then even the minimum
BL/B grade Idss of 6mA should work.

Hopefully others can share their experience.

Cheers,
Dennis
Click to expand...

Hi Dennis,

Ok, I understand how you mean.

BOTH Fairchild FETs I just tested had VGS = 4.54V @ 10mA ! (no need to match VGS)

I think I will complete one channel in a couple of days and let you know how it worked out for me.
I have BL and GR ranks of 2SJ74/2SK170, maybe some other usable JFETs too.

Thanks!
//Jonas
 
#2,691
I want to present my acknowledgments to all those who, in some way, contribute to the "diyaudio" community.

I would also like to express my gratitude to Jason and everybody else that has contributed to materialize the "diyaudiostore" and all its projects.
This store has become, whitout a doubt, one of the most trustworthy sources for DIYers from all around the world.

Thank you guys.

😀
 
#2,692
With Idss around 7mA on JFETs and VGS = 4.54V @ 10mA on Fairchild FETs I get about 500uA bias on the Fairchilds 🙂
Better increase the values of the resistor as Papa said.

I do not even have suitable quality 1k trimmers at home.

Our electronics store in out fantastic little town has decided to stop selling Bourns and moved to some chinese brand "ti" or something like that. I do not dare to use them.
But they have some cermet trimmers from BiTechnologies.
Anyone have any opinion about them?
I think they look like good quality.
 
#2,694
An email has been sent to everyone on the VFET kit mailing list. The email contains your "group" number and the exact time that your group will be sent an invitation to pre-order an essential kit from batch 3. The invitations are spaced exactly 12 hours apart and the time is specified so you know exactly when your email will arrive and you can be available at that time to take action. If you have any questions regarding this process, you didn't get your email, etc, please contact store customer support directly (don't post in this thread and please don't send me a PM) via email at contact@diyaudiostore.com. Thank you!

For any general information about the kits, please check the Sony VFET kit status page on the store.
 
#2,695
To anybody that has finished this kit: how does the temperature look like after an hour of idle time?

I must decide between the 4U deluxe (300mm deep with single heatsink) or the 4U Dissipante (400mm with 2 heatsinks) to fit our warmer summer climate. Yesterday it was 38 degrees C, and can easily go to 43 here. I don't want to go the 5U Deluxe to keep costs down.
 
#2,696
henryve said:
To anybody that has finished this kit: how does the temperature look like after an hour of idle time?

I must decide between the 4U deluxe (300mm deep with single heatsink) or the 4U Dissipante (400mm with 2 heatsinks) to fit our warmer summer climate. Yesterday it was 38 degrees C, and can easily go to 43 here. I don't want to go the 5U Deluxe to keep costs down.
Click to expand...

You can never have too much heatsink! 😉
 
#2,697
Okay, let's see, this is fairly straight forward.

According to https://www.modushop.biz/site/index.php?route=product/product&path=71_149_161&product_id=341 the 4U 400mm deep heatsink has a temperature coefficient of 0,38 C°/W.

According to https://www.modushop.biz/site/index.php?route=product/product&path=71_149_161&product_id=342 the 5U 400mm deep heatsink has a temperature coefficient of 0,28 C°/W.

With ±28V at 1A each you'll have about P=U*I=60W of dissipated heat per channel. With the 4U 0,38 C°/W you'll ideally have a temperature rise of 0,38°C/W*60W=22,8°C.

With the 5U 0,28 C°/W you'll ideally have a temperature rise of 0,28°C/W*60W=16,8°C.

Add to that your ambient temperature and choose whichever heatsink reliably stays below, say, 60°C.

Edit: I think there is a typo on the modushop website, since the temperature coefficient for the 4U 300mm is listed lower than the temperature coefficient for the 4U 400mm, which can't be true.
 
Last edited:
#2,698
Rodeodave said:
Okay, let's see, this is fairly straight forward.

According to https://www.modushop.biz/site/index.php?route=product/product&path=71_149_161&product_id=341 the 4U 400mm deep heatsink has a temperature coefficient of 0,38 C°/W.

According to https://www.modushop.biz/site/index.php?route=product/product&path=71_149_161&product_id=342 the 5U 400mm deep heatsink has a temperature coefficient of 0,28 C°/W.

With ±28V at 1A each you'll have about P=U*I=60W of dissipated heat per channel. With the 4U 0,38 C°/W you'll ideally have a temperature rise of 0,38°C/W*60W=22,8°C.

With the 5U 0,28 C°/W you'll ideally have a temperature rise of 0,28°C/W*60W=16,8°C.

Add to that your ambient temperature and choose whichever heatsink reliably stays below, say, 60°C.

Edit: I think there is a typo on the modushop website, since the temperature coefficient for the 4U 300mm is listed lower than the temperature coefficient for the 4U 400mm, which can't be true.
Click to expand...
Which all indicates that henryve must use the 5U case and switch it off when ambient rises above 43 degrees [emoji6]
 
#2,700
Rodeodave said:
Okay, let's see, this is fairly straight forward.

According to https://www.modushop.biz/site/index.php?route=product/product&path=71_149_161&product_id=341 the 4U 400mm deep heatsink has a temperature coefficient of 0,38 C°/W.

According to https://www.modushop.biz/site/index.php?route=product/product&path=71_149_161&product_id=342 the 5U 400mm deep heatsink has a temperature coefficient of 0,28 C°/W.

With ±28V at 1A each you'll have about P=U*I=60W of dissipated heat per channel. With the 4U 0,38 C°/W you'll ideally have a temperature rise of 0,38°C/W*60W=22,8°C.

With the 5U 0,28 C°/W you'll ideally have a temperature rise of 0,28°C/W*60W=16,8°C.

Add to that your ambient temperature and choose whichever heatsink reliably stays below, say, 60°C.

Edit: I think there is a typo on the modushop website, since the temperature coefficient for the 4U 300mm is listed lower than the temperature coefficient for the 4U 400mm, which can't be true.
Click to expand...

No typo I guess: when going 4U 400mm you have two heatsinks of 200mm per side of 0.38K/W resulting in 0.19K/W total.
So 4U will be sufficient for that 60 Watts.
 
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