Thanks, just watched it, got it, will build it! Also I do have a very good 10amp variac.
Q5 & Q6 question
I'm unclear on the order of the parts for mounting Q5 and Q6 supplied with the supplimental kit. Does the mica insulator go in between the MOSFET and the heat sink? I would assume it does but it is slightly wider than the heat sink so I figured I'd ask.
Thanks for the help.
I'm unclear on the order of the parts for mounting Q5 and Q6 supplied with the supplimental kit. Does the mica insulator go in between the MOSFET and the heat sink? I would assume it does but it is slightly wider than the heat sink so I figured I'd ask.
Thanks for the help.
I think there is a small typo in the PDF posted on the First Watt site. Where it says:
Now we are going to bias up the front end Mosfets. We will be looking at the
voltage drops across R5 (T6 and T7) and R6 (T9 and T10) as well as the DC
offset at T18 (relative to ground) while adjusting the trim pots P3 and P4
It should have the voltage across R6 measured at T8 and T9. It has the correct test points mentioned later.
Now we are going to bias up the front end Mosfets. We will be looking at the
voltage drops across R5 (T6 and T7) and R6 (T9 and T10) as well as the DC
offset at T18 (relative to ground) while adjusting the trim pots P3 and P4
It should have the voltage across R6 measured at T8 and T9. It has the correct test points mentioned later.
I believe it has been mentioned previously but I am glad others are now mentioning it because it means more are getting built. Non critical typo.
🙂
🙂
My supplemental kit arrived the other day (very fast service), now hoping to see the essentials kit show up to start the ball rolling.
Hope that you guys have better luck than I'm having. I've gained an extra volt on each rail after changing the power supply to a standard First Watt type, removed the Jfets from one channel and put them through the analyser again with curve tracing and they seem fine, just as they should be. Changed the 2n5551/5401 for the ztx types but the problem remains; low gain and distorted output when driven by my BA3. I have even tried the output from the pre-out on my Marantz AV amp but to no avail - same result!
It's probably staring me in the face if only I could see it, I'm convinced that it has to be in the front end somewhere.
Any ideas welcome.
Regards, John
It's probably staring me in the face if only I could see it, I'm convinced that it has to be in the front end somewhere.
Any ideas welcome.
Regards, John
I would like to help John, but my knowledge in this context is highly deficient:
EEE.
That is English and Electro Engineering.
Regards,
Gyuri
EEE.
That is English and Electro Engineering.
Regards,
Gyuri
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I promise you, tomorrow I will make some measurements on voltages of my amplifier.
Maybe it helps.
I can't stop to listen to music now.
I suggest to future builders to use a variac and a light bulb tester at the same time.
Pre set variac starting point to set amp's DC power voltages to cc. half of the full voltages. It prevent (I think) to cook the SONYs, which can occurs with lower voltages.
Remember what Papa said:
"I suggest that you raise the AC line to voltage over a period of less than 5
seconds."
It was the sentence caused some headache to me.
That is why I did so as above.
It works for me.
Maybe it helps.
I can't stop to listen to music now.
I suggest to future builders to use a variac and a light bulb tester at the same time.
Pre set variac starting point to set amp's DC power voltages to cc. half of the full voltages. It prevent (I think) to cook the SONYs, which can occurs with lower voltages.
Remember what Papa said:
"I suggest that you raise the AC line to voltage over a period of less than 5
seconds."
It was the sentence caused some headache to me.
That is why I did so as above.
It works for me.
Everything is now in stock, and orders should ship in the next 1-2 days.
The VFET status page has been updated with current information:
Sony VFET Kit Status Page - diyAudio Store
We'll offer batch 3 around February 6th, as usual email notifications will be sent out, in order of when you signed up on the list, however based on previous sales I am quite sure there will be enough for everybody and the remainder will list in the store to the public. It won't be ready to ship for a few months.
The VFET status page has been updated with current information:
Sony VFET Kit Status Page - diyAudio Store
We'll offer batch 3 around February 6th, as usual email notifications will be sent out, in order of when you signed up on the list, however based on previous sales I am quite sure there will be enough for everybody and the remainder will list in the store to the public. It won't be ready to ship for a few months.
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just to share,
my package stucks in customs clearance in germany for over a week now 😡
anyway, it´ll come soon enough 😀
my package stucks in customs clearance in germany for over a week now 😡
anyway, it´ll come soon enough 😀
Hey, John,
I have an idea what do you check, assuming that your amp's DC voltages are O.K..
Put a about 2.2VAC 50Hz signal on input.
An audiocard output can be good, and there are online signal generators, like this:
Online Tone Generator - Free, Simple and Easy to Use.
Choosen 50Hz, because it can be measured most of the DMMs.
(In my case it is about 2.2VAC RMS, because this is the level, where my amp started to clipping.)
Measure AC signal at T18, there should be about 17.3VAC.
While output shows about 14VAC RMS.
It is almost exactly 16dB, as Papa stated in the article.
This is a triumph of science and engineering, as I used to say.
Kind regards,
Gyuri
I have an idea what do you check, assuming that your amp's DC voltages are O.K..
Put a about 2.2VAC 50Hz signal on input.
An audiocard output can be good, and there are online signal generators, like this:
Online Tone Generator - Free, Simple and Easy to Use.
Choosen 50Hz, because it can be measured most of the DMMs.
(In my case it is about 2.2VAC RMS, because this is the level, where my amp started to clipping.)
Measure AC signal at T18, there should be about 17.3VAC.
While output shows about 14VAC RMS.
It is almost exactly 16dB, as Papa stated in the article.
This is a triumph of science and engineering, as I used to say.
Kind regards,
Gyuri
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