Looking at the circuit again, I noticed Nelson chose to put a 10uF for the power supply decoupling caps after the resistors. Any idea what type of cap it should be?
Thanks.
Oon
Thanks.
Oon
Oon,
I'm using the same type used in the Zen 4 supply decoupling. Look at Digi-Key part EF1106. They are 10uF metalized polyester 100v
Power supplies for F1 and F2 are identical.
Cochleus
I'm using the same type used in the Zen 4 supply decoupling. Look at Digi-Key part EF1106. They are 10uF metalized polyester 100v
Power supplies for F1 and F2 are identical.
Cochleus
Hi Oon,
With regards to your output cap have a look at this - only 63V (which is perfect in this circuit) but 470uF. It isn't cheap but at ~$30 but is maybe a 1/3 of the price of the 947c491k801cbms from Cornell Dubilier and would easily fit inside your chassis.
Audiocaps.co.uk - Arcotronics JSP
I don't know if they would ship out east, but you should be able to find other distributors closer to home.
Note: if you do decide to use audiocap.co.uk then they seem to be a good outfit - I ordered some capacitors and some clips from them, the clips were for different sized capacitors and they got in touch to make sure that I had not made a mistake when ordering which I thought was pretty good service.
It briefly passed my mind to use some of these in my F2J, but then I figured it would be ~$600 per channel for ~10000uF and then reality dawned 🙁
With regards to your output cap have a look at this - only 63V (which is perfect in this circuit) but 470uF. It isn't cheap but at ~$30 but is maybe a 1/3 of the price of the 947c491k801cbms from Cornell Dubilier and would easily fit inside your chassis.
Audiocaps.co.uk - Arcotronics JSP
I don't know if they would ship out east, but you should be able to find other distributors closer to home.
Note: if you do decide to use audiocap.co.uk then they seem to be a good outfit - I ordered some capacitors and some clips from them, the clips were for different sized capacitors and they got in touch to make sure that I had not made a mistake when ordering which I thought was pretty good service.
It briefly passed my mind to use some of these in my F2J, but then I figured it would be ~$600 per channel for ~10000uF and then reality dawned 🙁
Hi Ian,
Thanks for the tip. I think you made a small calculation error. The
One I was looking at was a bit cheaper.
For some reasons not clear to me this one is a lot cheaper than the rest.
Think will stick to this one. All for non audio reasons.
1) I want to have the dubious honour of being the first person on this forum to use a 1kg capacitor. Also with both channels, my cap will be heavier than my tranny. It's all about the bragging rights. Assuming nobody else have already beaten me to it. The capacitor is 4 inch in diameter and 5 inch long.
2} the other factor is, the jfets was developed for power inverters, so was this capacitor. So I thought it makes an ironic story... the pair working together...
3) On a different side of the matter. Using a much smaller capacitor does not reduce the bass response for the f2j. Since it is a current source the current will be the same on all parts of a series circuit. However the increase in impedance will reduce your maximum power output. It will be limited by your maximum voltage swing. The impedance of the cap will become significant at about 40Hz. So if you want to try it I believe the one 490uF you saw at the website will work. 2 might be better but 1 will be OK... In fact if you look up most op amp based low power single rail amplifier it is only about 1000 to 200 uF
Oon
Oon
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Thanks for the tip. I think you made a small calculation error. The
One I was looking at was a bit cheaper.
For some reasons not clear to me this one is a lot cheaper than the rest.
Think will stick to this one. All for non audio reasons.
1) I want to have the dubious honour of being the first person on this forum to use a 1kg capacitor. Also with both channels, my cap will be heavier than my tranny. It's all about the bragging rights. Assuming nobody else have already beaten me to it. The capacitor is 4 inch in diameter and 5 inch long.
2} the other factor is, the jfets was developed for power inverters, so was this capacitor. So I thought it makes an ironic story... the pair working together...
3) On a different side of the matter. Using a much smaller capacitor does not reduce the bass response for the f2j. Since it is a current source the current will be the same on all parts of a series circuit. However the increase in impedance will reduce your maximum power output. It will be limited by your maximum voltage swing. The impedance of the cap will become significant at about 40Hz. So if you want to try it I believe the one 490uF you saw at the website will work. 2 might be better but 1 will be OK... In fact if you look up most op amp based low power single rail amplifier it is only about 1000 to 200 uF
Oon
Oon
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Sorry,
I thought the 947c491k801cbms was $114 each on Newark/Farnell/Element14.
The stacked foil works out about $30 each (the $600 was if I wanted 10000uF, i.e. 20 per channel!).
Ian
I thought the 947c491k801cbms was $114 each on Newark/Farnell/Element14.
The stacked foil works out about $30 each (the $600 was if I wanted 10000uF, i.e. 20 per channel!).
Ian
Interesting. It shows up s $27 in my part of the world. Maybe it is locality dependent. I chose that particular one because it was instock in Singapore. Maybe if you had chosen one that was in the UK, it might be cheap on your side and expensive in mine...
Oon
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Oon
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Wow $27 for 1KG of polypropylene capacitor, you can't argue with that, I shall be interested in your listening impressions when compete!
Hey you can try it too. The one you suggested is of the same value. And it doesn't cost much. And as I have mentioned, in a current source amplifier unlike a voltage source amp, the current is identical everywhere in a series circuit. So there is no roll off in the bass like a normal voltage amp. Just a limitation in power output in the lower bass region....
Oon
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Oon
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Any chance someone can try their f2j with a traditional speaker and tell us a bit about how it sound?
Hi Djnubz,
There would be an amount of rework to make a current source amp work correctly with a voltage source designed crossover.
Parallel crossover elements in a voltage source arrangement become series in a current source arrangement and vice versa.
You should read NP's article on current source amps at Current Source Amps
There would be an amount of rework to make a current source amp work correctly with a voltage source designed crossover.
Parallel crossover elements in a voltage source arrangement become series in a current source arrangement and vice versa.
You should read NP's article on current source amps at Current Source Amps
Ianc13 thanks for the link. I have paged through it and a few other articles by Mr. Pass on the subject. It was more of a, I know it's not supposed to work but has anyone tried it any way, question.
Hi djnubz,
I think the essence of it is the performance will be quite varied and unpredictable. So no matter what one says, you can't generalise for the rest. The issue here lies with the impedance curve for the speaker which will roughly translate to the 'frequency' response. So the peaks of the curve will become peaks in the frequency response. That is why it works better for simple single drivers. At least one can predict the impedance and hence compensate for it..
Oon
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I think the essence of it is the performance will be quite varied and unpredictable. So no matter what one says, you can't generalise for the rest. The issue here lies with the impedance curve for the speaker which will roughly translate to the 'frequency' response. So the peaks of the curve will become peaks in the frequency response. That is why it works better for simple single drivers. At least one can predict the impedance and hence compensate for it..
Oon
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Alright. I finally got around to finish it. I must say the sound is gorgeous. The way it fills up the room with somuch emotion...
Picture included. Yup those two black things are my 490uf output caps.. polyproplene....
I stack my claim as the person who has used the biggest caps there is in his F amp...
Oon
Picture included. Yup those two black things are my 490uf output caps.. polyproplene....
I stack my claim as the person who has used the biggest caps there is in his F amp...
Oon
great work oon, did you need any compensation network to get the F2j to play nicely with your speakers?
Didn't use any however I used a bit of graphic equalizer in my software to reduce the shout. Might be good to add in a zobel network...
Oon
Oon
Reviving an old thread... Are there any power JFETs currently available for building a F2J?
Specifically, I was interested in the UJ3N065080K3S by United SIC. Would this be a viable option for the F2J? If this isn't a reasonable alternative, is there anything else available that I'm missing?
To expand on this, even if it won't perform as well as the original SemiSouth JFETs, would it be an improvement over a MOSFET based F2?
If this has been answered already, I apologize. I've spent a few hours searching and reading threads but couldn't seem to find an answer.
Specifically, I was interested in the UJ3N065080K3S by United SIC. Would this be a viable option for the F2J? If this isn't a reasonable alternative, is there anything else available that I'm missing?
To expand on this, even if it won't perform as well as the original SemiSouth JFETs, would it be an improvement over a MOSFET based F2?
If this has been answered already, I apologize. I've spent a few hours searching and reading threads but couldn't seem to find an answer.
SemiSouth JFETs available here but pricey.
SemiSouth JFET Transistor SJEP120R100 High Performance Audio Amp New 2pcs | eBay
They have been talked about here and believed to be original.
SemiSouth JFET Transistor SJEP120R100 High Performance Audio Amp New 2pcs | eBay
They have been talked about here and believed to be original.
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