Hi FX8 fans
new Toshiba TTA004B_Q/TTC004B_Q (hfe about 210..others about 85-100)
I did the VAS transistor update at my other FX8 too. Be aware that you have to adjust the bias again because of the higher hfe of this toshiba transistors.
i changed to ceramic caps to the Wima film caps. Sound is now better, give me more chest of the singers and better impulse response.
chris
new Toshiba TTA004B_Q/TTC004B_Q (hfe about 210..others about 85-100)
I did the VAS transistor update at my other FX8 too. Be aware that you have to adjust the bias again because of the higher hfe of this toshiba transistors.
i changed to ceramic caps to the Wima film caps. Sound is now better, give me more chest of the singers and better impulse response.
chris
Hi
Additionally i change the PSU rectifier - from KBPC to the active rectifier by Prasi for each rail. Without done the Quasimodo snubber for the transformer i am very happy with this change. Very clear sound as i had the experience with the ACA PSU for a friend. Maybe the transformer snubber in the old configuration should be done more necessary then now with the active rectifier. the sound is very nice. You should try this. additionally i have 2 Volts more at each rail. 😉
LT4320:
here
chris
Additionally i change the PSU rectifier - from KBPC to the active rectifier by Prasi for each rail. Without done the Quasimodo snubber for the transformer i am very happy with this change. Very clear sound as i had the experience with the ACA PSU for a friend. Maybe the transformer snubber in the old configuration should be done more necessary then now with the active rectifier. the sound is very nice. You should try this. additionally i have 2 Volts more at each rail. 😉
LT4320:
here
chris
Hello again
i have done some changed inspired by some threads:
my feedback after listening :
i like the sound of FX8 but the lack of fine high frequencies and compress feeling at higher volume is marked by me as disadvantage. the mids a very good and the bass is controlled and not boomy but somethimes "too controlled". but okay.
this amp can help if you have a boomy room or a loudspeaker which need less low freuency power to have a blanced feeling.
after my changes i compared with the VSQA amp. the difference i noticable. no stress in higher frequencies, flute and singers are clear and feels not compressed.
try it and give me feedback.
kr
chris
i have done some changed inspired by some threads:
- gate resistor change at the N ch mosfet 100--330R (maybe too high?)- i looked at a lot of Lateral threads and there are always changes of the gate resistors.
- snubber between Drain and Gate - like in the VSQA thread- 220pF and 47R in serie - to avoid HF oscillations.(the smal 0,25W resistor is under the yellow tube)
its recommended by AKSA that it is for high transconductance MOSFET and/or higher rails but it works with my LATERals (Renesas) and just 34V.
my feedback after listening :
i like the sound of FX8 but the lack of fine high frequencies and compress feeling at higher volume is marked by me as disadvantage. the mids a very good and the bass is controlled and not boomy but somethimes "too controlled". but okay.
this amp can help if you have a boomy room or a loudspeaker which need less low freuency power to have a blanced feeling.
after my changes i compared with the VSQA amp. the difference i noticable. no stress in higher frequencies, flute and singers are clear and feels not compressed.
try it and give me feedback.
kr
chris
Attachments
Hi Chris,
that reminds me of the old 2SK134/2SJ50 in the Crescendo or something else.
Between the drain and the gate of 2SK134 an extra 33pF was fitted, and between the source and the gate a 330pF capacitor, because lateral mosfet are not equal, but symmetrical driven.
Are you sure the capacitors must be equal ?
Peter
that reminds me of the old 2SK134/2SJ50 in the Crescendo or something else.
Between the drain and the gate of 2SK134 an extra 33pF was fitted, and between the source and the gate a 330pF capacitor, because lateral mosfet are not equal, but symmetrical driven.
Are you sure the capacitors must be equal ?
Peter
Have you tried the capaticitors? I will try if i have the time...i have 2SJ162/2SK1058 built in, perhaps they are different to the reneas mosfet, dont know.
2SJ162/2SK1058 are Renesas ...former Hitachi.
yes i tried the caps 220p+47R as snubber at the Drain-Gate (see pic)
yes i tried the caps 220p+47R as snubber at the Drain-Gate (see pic)
May be i am wrong, but i think to use 330pf and 33 pf is the better way, because the pf value of the lateral transistors is different. Your snubbers are equal, i think because the VSQA Amp uses the same power transistors (as i have seen) at the output.
I will try as i wrote. It is the same difference as in the datasheet of the old 2SK134/2SJ50.
If you have success with your snubbers all is fine...🙂
Peter
I will try as i wrote. It is the same difference as in the datasheet of the old 2SK134/2SJ50.
If you have success with your snubbers all is fine...🙂
Peter
Good evening,
anyone interested in experimenting? I have the MIRO360 boards for sale, which I no longer use because I have too many amplifiers.
Best regards.
Guglielmo
Italy
anyone interested in experimenting? I have the MIRO360 boards for sale, which I no longer use because I have too many amplifiers.
Best regards.
Guglielmo
Italy
Hi Bart
ECX10P20 Plastic Lateral MOSFET...and the compl.
actually not in stock
Lateral MOSFETkr
chris
The Exicon Transistors are in stock at audiophonics
https://www.audiophonics.fr/en/comp...x10n20-transistor-mosfet-2sk1058-p-15183.html
7,5 Euro each...
Profusion has sold out. 🙁
Gretings
Peter
https://www.audiophonics.fr/en/comp...x10n20-transistor-mosfet-2sk1058-p-15183.html
7,5 Euro each...
Profusion has sold out. 🙁
Gretings
Peter
https://eu.profusion.uk/at_en/audio/transist/lateral-mosfets
Their list is a bit confusing, but shows in-stock options.
Their list is a bit confusing, but shows in-stock options.