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Old 22nd March 2015, 04:11 AM   #11
marsupialx is offline marsupialx  United States
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I knew I should have finished Cubie faster. Now there is this one to build. Looks like it can be made to fit the same case. Thanks, Juma!! ps I thought you were working on a circlotron with lu1014s.

Last edited by marsupialx; 22nd March 2015 at 04:17 AM.
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Old 22nd March 2015, 11:38 AM   #12
juma is offline juma  Serbia
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Yes it'll fit in the same box - the PCB is about the same size (the new one is 5mm wider), the same output devices are used, PSU and current/voltage/dissipation requirements are also the same.

I drew the PCB so that placement of output devices is the same as in the first Cubie so it's easy to take the old PCB out and solder the new one in.

That LU1014 circlotron is something that's been cooking for a long time but somehow I never managed to bring it to the end (too many versions and ideas and too many other projects - this is not my job, just a hobby so the time it's allowed to consume is limited...)
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Old 22nd March 2015, 12:51 PM   #13
fab is offline fab  Canada
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Any reason why it does not include the double feedback arrangement like the F5 or your variations of the F5.
Also, in your build you seem to have an input cap with few caps in parallel. Can you share your thoughts and/or experience on what type and combination and values are best.

Have you considered lowering vas degeneration resistors value. I have found that it can sometimes improve perceived dynamics.

Thanks
Fab

Last edited by fab; 22nd March 2015 at 01:03 PM.
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Old 22nd March 2015, 01:49 PM   #14
juma is offline juma  Serbia
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Quote:
Originally Posted by fab View Post
Any reason why it does not include the double feedback arrangement like the F5 or your variations of the F5.
F5-like circuit has a single input pair with fixed (let's neglect the P3 addition) degeneration that connects to ground so sources/emitters come naturally as symmetrical feedback points. It's not exactly the same case here where we follow the idea of symmetrical folded cascode gain cell (BAF2013 preamp) where sources' circuit is "loaded" to GND with a single, current-swing/gain-determining resistor that presents itself as a feedback point. Of course, it can be done in a F5-like manner but it would raise the complexity without a benefit and the DC offset would have to be dealt with in a less elegant manner.

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Also, in your build you seem to have an input cap with few caps in parallel. Can you share your thoughts and/or experience on what type and combination and values are best.
Yes, it's a precaution measure since all kinds of gadgets are used as signal sources all the time and some of them leak DC. The combination of Philips MKC and WIMA MKP10 caps I find very neutral. Caps are no big deal by themselves, it's how they are used - take a stage with high output Z , couple it to a stage with low input Z, use the filter-like cable (I had a chance to test very expensive ICs with more than 1nf capacitance per meter) and you are in trouble - every coupling cap will leave a hearable signature.

Please don't turn this thread into futile, never ending discussion about caps, cables and other trivia...
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Old 22nd March 2015, 01:56 PM   #15
fab is offline fab  Canada
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Quote:
Originally Posted by juma View Post
.....

Yes, it's a precaution measure since all kinds of gadgets are used as signal sources all the time and some of them leak DC. The combination of Philips MKC and WIMA MKP10 caps I find very neutral. Caps are no big deal by themselves, it's how they are used - take a stage with high output Z , couple it to a stage with low input Z, use the filter-like cable (I had a chance to test very expensive ICs with more than 1nf capacitance per meter) and you are in trouble - every coupling cap will leave a hearable signature.

Please don't turn this thread into futile, never ending discussion about caps, cables and other trivia...
It has never been my intention to hijack your thread.

Thanks
Fab

Last edited by fab; 22nd March 2015 at 01:58 PM.
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Old 22nd March 2015, 02:27 PM   #16
juma is offline juma  Serbia
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No fab, you are a great guy to talk to, and thread-hijacking is not a big deal anyway.
It's just that caps, cables and similar trifle are such a boooooring subject...

Last edited by juma; 22nd March 2015 at 02:31 PM.
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Old 22nd March 2015, 08:58 PM   #17
fab is offline fab  Canada
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Ok I understand, thanks Juma.
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Old 27th March 2015, 02:14 PM   #18
mikvous is offline mikvous  Greece
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Could this circuit work with +/- 25V rails?Any changes needed?
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Old 27th March 2015, 02:53 PM   #19
juma is offline juma  Serbia
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Sure. Change R14 to 15k/0.5W to dislodge few mA from Q6,7 i.e. to keep their Pd at no more than 200mW. Of course, Rbias needs changing too since less current means lower voltage drop across it and that lowers the current through output stage, but that will depend on your Laterals' Vgs/Id characteristic anyway...
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Old 28th March 2015, 03:24 AM   #20
ammel68 is offline ammel68  United States
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Does anyone know of a good source for the 2SK1058 and 2SJ162?

Thanks...
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