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Sony Vfet Illustrated build guide
Sony Vfet Illustrated build guide
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Old 29th March 2020, 08:02 PM   #1041
anilva is offline anilva  India
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Default Finally completed VFET Amp

6L6, thanks for your VFET build guide. After having bought the VFET kit from DIYAUDIO store more than 3 years back, I finally found time to complete the amp. Thanks to the build guide, putting together this amp was a breeze. I managed to setup the VFET bias to 1.5 amps due to big Heatsink’s I had. The amp works wonderfully. The best sound I heard so far. Standout quality is the timbre of voices and instruments.

Thanks Papa for a brilliant design.

I am not fugly in build looks, but quite functional and does the job well. Here are some pictures.

Cheers.
Anil
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DIY VFET, J2, F5T, F6, Aleph J, M2 & 45/2A3 DHT SET Amp, Fostex 206 based BLH, Altec 515 LF & 288 HF Onkens, Tannoy HPD Speakers. EMT950, Technics SP10, Garrard 401, TD124 turntables.
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Old 29th March 2020, 08:04 PM   #1042
Dennis Hui is offline Dennis Hui  Canada
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Sony Vfet Illustrated build guide
Looks great. Congratulations!
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Old 29th March 2020, 08:41 PM   #1043
6L6 is offline 6L6  United States
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Sony Vfet Illustrated build guide
Very nice! So glad you like it, the amplifier is genuinely one of the best ever made.
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Old 31st March 2020, 06:39 PM   #1044
anilva is offline anilva  India
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Default Uneven gain between 2 channels

I have been playing the VFET amp for the last 2 days after the build. I noticed that one of the channels has lower gain than the other one. Is it possible? What should I look at ? Both the channels are biased at the front end and at the VFET similarly.

I will recheck the bias levels once again. There seems to be atleast 3dB difference between the two channels. One Channel has VFETs marking of 81 and 89 and the other channel has 81 and 94 for vgs measurement. Could this be the issue?

Regards
Anil
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DIY VFET, J2, F5T, F6, Aleph J, M2 & 45/2A3 DHT SET Amp, Fostex 206 based BLH, Altec 515 LF & 288 HF Onkens, Tannoy HPD Speakers. EMT950, Technics SP10, Garrard 401, TD124 turntables.
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Old 31st March 2020, 06:49 PM   #1045
Dennis Hui is offline Dennis Hui  Canada
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Sony Vfet Illustrated build guide
The markings and bias should not have the effect you noted.

Did you make measurements? Trying switching inputs, etc?

Also have a look if R3/R4 values are correct.
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Old 1st April 2020, 07:33 AM   #1046
anilva is offline anilva  India
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Quote:
Originally Posted by Dennis Hui View Post
The markings and bias should not have the effect you noted.

Did you make measurements? Trying switching inputs, etc?

Also have a look if R3/R4 values are correct.
Thanks. The problem seems to be from the vintage yamaha preamp, which has a sticky volume control.

Regards
Anil
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DIY VFET, J2, F5T, F6, Aleph J, M2 & 45/2A3 DHT SET Amp, Fostex 206 based BLH, Altec 515 LF & 288 HF Onkens, Tannoy HPD Speakers. EMT950, Technics SP10, Garrard 401, TD124 turntables.
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Old 3rd April 2020, 05:06 PM   #1047
vuongan is offline vuongan  United States
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Default My Vfet Amp

I am gradually completing my vfet amp project after 3 long years
there are a few small changes, instead of using the T heat sink I made into the U heatsink, helping the PCB parallel to the heat sink, saving maximum space inside the chassis
Chassis size now: outside 400 x 320 x 120, inside 235 x 300 x 115, compact for a class A amplifier, I like that
I am having a small problem with my amp, and need your comments and help:
currently i am using 2 separate sources for 2 channels of amp, I have yet to match the mass scores of the 2 channels with the overall mass points of the chassis,
2 channels that work individually are perfect
but I can't bring them to the overall mass point of the chassis, because between the 2 points of the 2 channels mass appear voltage of 12.3 AC, My scopemeter died a B channel when I accidentally created a common point between the two amp channels, I don't know why?
,Why Why Why??? I have checked the rectifier diodes, there is no AC voltage detection between them, the DC sources are clean sources. Can someone help me, tell me what should I check?
and I am designing the front of the chassis, can someone give me an idea?
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Old 3rd April 2020, 05:59 PM   #1048
vuongan is offline vuongan  United States
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Default My Vfet Amp

The problem was solved, because I used the same source for the speaker protection.

I am designing the front of the chassis, can someone give me an idea?
thank everyone !
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Old 11th April 2020, 06:06 PM   #1049
Bones13 is offline Bones13  United States
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Sony Vfet Illustrated build guide
Started back working on my VFet amplifiers (monoblocks) I was chugging along there awhile back, and up to the point of doing adjustments, when I figured out that I had PSU issues. First, I had the wrong transformer voltage (too many different VFets out there, and I picked wrong, not terribly. I also, at that time, could not get the DIYAudioStore power supply boards, as they were out there for awhile. I used a set of PSU boards from ebay, and one of them shorted out right off.

I did start with the full VFET kit from the store, including store matched input transistors.

I took some time off, putting my Aleph J back in service, and subsequently I am using McIntosh MC60 amps, that my dad had in the attic, and getting them reconditioned.

With the enforced home time due to Covid-19, I decided to give them another shot, and got new Antek transformers, and new PSU boards from the DIYStore. I put all that back together on the first monoblock. PSU voltage now 28 as per spec. After an initial setting of values for 1.2v, 1.2v, 100mv, and 0.4mv offset, I tried some rather non-sensitive speakers, and got a bit of sound out. I let it run for a bit more, re-did the values to the above numbers, but when I hooked the speakers back up no sound at all out of the amp. The transistors are all warm, not hot, all the LEDs are lit, and the settings are staying stable. No magic smoke, no pops, no scorched components.

I'm not sure I have the enthusiasm to update the PSU+transformer in the other box at this point.

Where should I even look?
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Old 11th April 2020, 06:10 PM   #1050
Rush is offline Rush  United States
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Quote:
Originally Posted by Bones13 View Post
Started back working on my VFet amplifiers (monoblocks) I was chugging along there awhile back, and up to the point of doing adjustments, when I figured out that I had PSU issues. First, I had the wrong transformer voltage (too many different VFets out there, and I picked wrong, not terribly. I also, at that time, could not get the DIYAudioStore power supply boards, as they were out there for awhile. I used a set of PSU boards from ebay, and one of them shorted out right off.

I did start with the full VFET kit from the store, including store matched input transistors.

I took some time off, putting my Aleph J back in service, and subsequently I am using McIntosh MC60 amps, that my dad had in the attic, and getting them reconditioned.

With the enforced home time due to Covid-19, I decided to give them another shot, and got new Antek transformers, and new PSU boards from the DIYStore. I put all that back together on the first monoblock. PSU voltage now 28 as per spec. After an initial setting of values for 1.2v, 1.2v, 100mv, and 0.4mv offset, I tried some rather non-sensitive speakers, and got a bit of sound out. I let it run for a bit more, re-did the values to the above numbers, but when I hooked the speakers back up no sound at all out of the amp. The transistors are all warm, not hot, all the LEDs are lit, and the settings are staying stable. No magic smoke, no pops, no scorched components.

I'm not sure I have the enthusiasm to update the PSU+transformer in the other box at this point.

Where should I even look?
Post detailed pictures please.

Might be something over looked. Like input wires crossed.

Rush
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