I got the other channel adjusted to about the same specs as above, one of the irfp240 is hotter than the other, 65 degrees c vs. 50.degrees for the other. Is this normal?
After half hour heatsinks are still cooler than my F5 so I guess all is good.
After half hour heatsinks are still cooler than my F5 so I guess all is good.
In the BAF 2012 speach Nelson says if one wants a positive phase 2nd harmonic to put a source resistance on Q2 and not put any resistance on Q1 but on the schematic for the mosfet transistors the larger value resistor is on the source of Q1. Does anyone knows why Mr Pass designed the mosfet schematic with the larger resistor on Q1? I am sure there is a valid reason and I am just curious. I cannot call Mr Pass Papa because we are the same age.
I am one of the lucky ones who bought the F6 boards early along with the matched jfets and they are to be delivered today.
David
I am one of the lucky ones who bought the F6 boards early along with the matched jfets and they are to be delivered today.
David
You don't know how lucky you are... 75% of the PCB and a tad more than 50% of the Jfet sold in the 2 hours they were up for preorder, before being taken down because the default placeholder prices were (much) too low. The store is honoring it, which I think is great.
They should be back up for sale today or tomorrow, if you want some, order the second you see it, supplies will not last.
The next F6 item in the store will be the PCB and Jensen transformers bundled together.
Wow, I was watching and totally missed it. I guess I'll need to monitor things more closely so I don't miss out
PJN
PJN
Nobody has gave an answer on why Q1 source resistor is larger than Q2 so I am going to assume everyone is in the dark like me. I hope Mr Pass can take time in his busy day to enlighten us on why this is so. I can only admire someone my age that appears not to have slowed down working every day.
I received my F6 boards and matched jfets today and the boards look great. I did not think I would be lucky enough to see them go on sale but I when I heard that they were going to be available I started looking regularly all during the day. I had already started to do point to point on a proto board and had to remove the transformers from the boards which is not an easy task. I know how but it is time consuming but I got them off and they check good. Having made boards makes it far more simple and is worth the cost. I am looking forward to hearing an F6 amplifier.
David
I received my F6 boards and matched jfets today and the boards look great. I did not think I would be lucky enough to see them go on sale but I when I heard that they were going to be available I started looking regularly all during the day. I had already started to do point to point on a proto board and had to remove the transformers from the boards which is not an easy task. I know how but it is time consuming but I got them off and they check good. Having made boards makes it far more simple and is worth the cost. I am looking forward to hearing an F6 amplifier.
David
The source resistor is to change the harmonic structure. It would work just fine with even valued source resistors.
It would totally be worth a listen to try it both ways.
It would totally be worth a listen to try it both ways.
If you want F6 PCB only, order right now... only 4 left.
Also, matched Jfet are live in the store. They will sell out very quickly.
Also, matched Jfet are live in the store. They will sell out very quickly.
That is what I understand from the BAF speech Nelson gave, I am curious just why he chose the higher resistor for Q1. It may be as simple that it sounded better to him that way. I could not find .56 3 watt resistors at mouser so I ordered .62 3 watt. I have considered using equal .47 resistors for both Q1 and Q2. The resistors I have are 5 percent so I may just measure them and use the higher value .47 for Q1. Thanks for the reply 6L6.
David
David
0.56R 3W -- RS02BR5600FB12 Vishay / Dale | Mouser
I also like your idea of using the higher value on the positive rail's mosfet. Do you have a meter accurate at low resistances?
I also like your idea of using the higher value on the positive rail's mosfet. Do you have a meter accurate at low resistances?
So you would use a wire wound resistor. I had a mindset of metal oxide and did not consider wire wound. No I do not have a meter that measures low resistance that well. Mine wanders some at low resistances. I will leave the source resistors high on the board where I can swap them out without having to remove the boards. I have an oscilloscope but not a distortion analyzer where I could see what is going on. A distortion analyzer is on my wish list.
David
David
Had to use WW -- it's the only thing available in such an odd value.
Distortion analyzer is nice, but if you had a decent signal generator, (Hardware, software or App...) you could just build one of these -
Electronic Equiptment - DIY soundcard scope probe
and then make a high-resolution FFT with this software -
audioTester
and see the relative harmonic peaks. 🙂
Distortion analyzer is nice, but if you had a decent signal generator, (Hardware, software or App...) you could just build one of these -
Electronic Equiptment - DIY soundcard scope probe
and then make a high-resolution FFT with this software -
audioTester
and see the relative harmonic peaks. 🙂
Wow!,
F6 is best seller NP F series?
Everything's is Very first ,luckly I got one match pair now out of stock .
F6 is best seller NP F series?
Everything's is Very first ,luckly I got one match pair now out of stock .
Finally getting all the parts together for this build.
In one of Nelsons talks someone in the audience asked how critical the value of the power supply voltage and his response was he had a very large stock of 18Vac dual secondary transformers so that's what he used.
What is the maximum voltage secondary I can use to build this amp as I have access to a very large 24Vac dual secondary?
In one of Nelsons talks someone in the audience asked how critical the value of the power supply voltage and his response was he had a very large stock of 18Vac dual secondary transformers so that's what he used.
What is the maximum voltage secondary I can use to build this amp as I have access to a very large 24Vac dual secondary?
I am happy to report my findings testing the idss for the matched jfets.
The first pair
k170 10.6 idss
j74 10.59 idss
2nd pair
k170 10.6 idss
j74 10.57 idss
I was using a 9 volt battery that tested 9.6 volts. I am very satisfied with the results and how well both pairs matched to each other. Hats off to the Diyaudio store.
David
The first pair
k170 10.6 idss
j74 10.59 idss
2nd pair
k170 10.6 idss
j74 10.57 idss
I was using a 9 volt battery that tested 9.6 volts. I am very satisfied with the results and how well both pairs matched to each other. Hats off to the Diyaudio store.
David
Thanks! That's pretty amazing results, considering I matched them myself and wasn't trying for results that close. (There just isn't the quantity available to make super tight pairs.) And anyway, they don't need to be all that tight for these amps, 10% is more than good enough.
That will make a PSU of approx. 31.5V. I wouldn't try it. And anyway, this amp is really going to want the smallest, shielded transformer for the job. Something like the Antek AS-3218 would be ideal.
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I was wondering who took the time to match these transistors. Great job Jim and thanks.
Stuffed my boards this morning and now is the time to drill and tap holes in my 4U heatsinks. I come from a mechanical, machine shop background so it is not a hard task just time consuming. I have noticed a lot of members have trouble tapping holes, breaking off taps. Breaking taps is the one thing no machine shop wants to do because the tap is harder than any drill bit. On a large tap that has to be taken out the way we did it is to crack them out so on a small tap it is about impossible. Take your time with some lubrication and when the tap gets tight and hard to turn BACK IT OUT to clean the threads. With practice you can feel the tap stretching a little so STOP when it does that. If necessary take the tap completely out, clean the tap of excess filings and start over.
I just thought to include this tapping info for anyone that is interested. I am sure there are better and different ways but this way works.
David
Stuffed my boards this morning and now is the time to drill and tap holes in my 4U heatsinks. I come from a mechanical, machine shop background so it is not a hard task just time consuming. I have noticed a lot of members have trouble tapping holes, breaking off taps. Breaking taps is the one thing no machine shop wants to do because the tap is harder than any drill bit. On a large tap that has to be taken out the way we did it is to crack them out so on a small tap it is about impossible. Take your time with some lubrication and when the tap gets tight and hard to turn BACK IT OUT to clean the threads. With practice you can feel the tap stretching a little so STOP when it does that. If necessary take the tap completely out, clean the tap of excess filings and start over.
I just thought to include this tapping info for anyone that is interested. I am sure there are better and different ways but this way works.
David