I have something else for the good builders of the DIY Sony VFET to try. This is an idea employed by the Zen V9, it’s commercial variant the F3 and others. Wait until the amp has had a good run-in period.
Add a Nichicon KW series 470 uF, 100V capacitor in parallel with the big 10,000 uF cap on the output stage cards. Best done on the underside where the wire leads of the 470 uF can be soldered onto the snap-in style pins of the big cap.
Add a Nichicon KW series 470 uF, 100V capacitor in parallel with the big 10,000 uF cap on the output stage cards. Best done on the underside where the wire leads of the 470 uF can be soldered onto the snap-in style pins of the big cap.
I have the ACP+ ready to start tomorrow (there will be some machining and case building involved), and I have Wayne’s Line Stage PCB and Parts, but not the PSU nor pot nor connectors, so that will require more planning.
Really excited about all the projects. But this one was the crown jewel. I really love what the VFET amp has brought to our system.
Thanks all for the good wishes and comments!
Rafa.
Ok... so, lets talk about cooking! Boiling eggs, frying chips... that sort of cooking! I have my heatsinks at 44°C ~ 48° as well (around 20C ambient)... but the top of the Sony device reads 75°!
I was trying to find anyone else reporting measurements of the actual devices, but I find mostly everyone seems to have reported only the 50°C at the sinks.
This (in Chinese or Japanese) PDF seems to report Tj at 120°C: http://www.amplimos.it/images/2SJ18-2SK60.pdf , so... maybe 75°C is not unreasonable?
The IRF250 also reports a similar operating temperature range (they are as hot as the Sony VFETs in my rig).
As a side question, what difference in temperature from the actual internal devices to their own TO-3 encasing do you think can be reasonable? From the device to the heatsink there is a good 65% loss of heat. I hope the device's own casing is a bit more efficient? If we calculate the same 65% or so effectiveness, the internal devices would be at 120°C.
I hope all these temps are expected? I'd like to enjoy this amp for many years!
Thanks for any feedback, best regards,
Rafa.
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Yep, obviously when going biamping and driving the mids, Fc fomed by the low pass of the LS impedance and the output cap is less important
...But thing is I only have one VFET
I was more wondering regarding single amp application and the addition of the suggested bypass cap, as I haven't read the relevant thread on the other amps
...But thing is I only have one VFET
I was more wondering regarding single amp application and the addition of the suggested bypass cap, as I haven't read the relevant thread on the other amps
Hi.
If these are your speakers, you may wish to have a look at this review.
Totem Acoustic Rainmaker loudspeaker | Stereophile.com
Claude,
Yes, I have tried adding the 470 uF caps in parallel with the big output cap already. Very happy that I did. They improved the clarity of the upper midrange and treble by a small yet significant amount. I chose the value of 470 uF in hope of improving a wider bandwidth, and because that is what I already had available in the Nichicon KW series. I’m sure there is a range of values that will work well. The First Watt F3 uses 220 uF, as I recall. It is important to use the highest quality audio series, and I have those KW series caps on hand because they are at the top of Nichicon line of audio grade electrolytics.
Yes, I have tried adding the 470 uF caps in parallel with the big output cap already. Very happy that I did. They improved the clarity of the upper midrange and treble by a small yet significant amount. I chose the value of 470 uF in hope of improving a wider bandwidth, and because that is what I already had available in the Nichicon KW series. I’m sure there is a range of values that will work well. The First Watt F3 uses 220 uF, as I recall. It is important to use the highest quality audio series, and I have those KW series caps on hand because they are at the top of Nichicon line of audio grade electrolytics.
Regarding the temperature of the output devices – yes they do run hot, touchable for about two or three seconds in my amp. I found that their mounting screws could be tightened a little. Carefully with strong finger pressure. That helped.
Hopefully everyone is remembering to use extra split washers under the mounting bolts for the aluminum L brackets. The mounting bolts are just a little too long and need stacked washers to prevent bottoming out.
Hopefully everyone is remembering to use extra split washers under the mounting bolts for the aluminum L brackets. The mounting bolts are just a little too long and need stacked washers to prevent bottoming out.