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Old 26th January 2009, 12:16 AM   #761
Salas is offline Salas  Greece
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No problem, only your dissipation on the CCS Mosfet is gonna go up to 2.2W with 40V DC in. You gonna be secure against off limits mains drop on the other hand.
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Old 26th January 2009, 12:53 AM   #762
Salas is offline Salas  Greece
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Default Re: 28V Led Shunt

Quote:
Originally posted by RCruz
Hi Salas

Should I build two shunts (one for each channel) or is it overkill ?

Ricardo
Don't know for sure at the moment, off course cartridge channel separation isn't demanding at all, and the shunt has very low output impedance so not to let channels inter modulate enough. Someone would say it may pass without a benefit. But Cygnus X1 always uses double supplies and says he can hear it doing better. I will know more soon, because we are planing with Michael a good build with subjective tuning on good parts selection and two LED shunts with two 100VA mains toroids in a full width box. It has already started. A few stuff from Ebay and we will know what benefits and what is not.
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Old 26th January 2009, 04:51 AM   #763
es44 is offline es44  Denmark
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Quote:
Originally posted by salas


You can even bypass R1 (the 100R resistor under first stage JFET) with a 1000uF Panasonic FC or Elna Silmic or Black Gate NX 6.3V and it will become 41dB gain without further changes.
That easy ?

I will try that. admitted, i don't have any "high grade" stuff, but will, as a test, use a couple of Frako's i have in stock.

Thanks a lot for advise Salas.

Best regards
Ebbe
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Old 26th January 2009, 10:38 AM   #764
Salas is offline Salas  Greece
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Quote:
Originally posted by es44


That easy ?

Yes it will work that easy. It is just not the best way if you have a very good system and you are looking not to listen to any electrolytic capacitor sound quality. On the other hand, in tubes world such ways are used and many people even ''cook'' their tone using parts quality sonic colors.
Try with the Frakos, and if your system has the analysis to still show any cloudy quality of them after 48 hours of play, just parallel one little (sub 1uF) film cap across each Frako. It will open up.
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Old 26th January 2009, 11:21 AM   #765
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HI Salas

the shunt I still make for driver stage are one for channel as diode and caps but with only one trafo
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Old 26th January 2009, 11:34 AM   #766
Salas is offline Salas  Greece
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Still better than one.
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Old 26th January 2009, 08:11 PM   #767
iko is offline iko  Canada
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Just want to thank you guys for all your help again, I've finished the prototype last night. It's a bit too early for comments, since I haven't had the opportunity to listen much to it. However, the initial impression is tight strong bass, ok highs, but not great mids. I don't mean to say this as a negative comment; the preamp sounds very clear, nice tone, but just didn't hear that "special" sound yet. More tuning is in order.

Unfortunately in the batch of jfets I had there were none with an Idss of 7-8mA, all were higher. Another batch of 100 pieces came today, so I'll be doing more matching soon.

salas, would you say that all of the four jfets should be in the 7-8mA, or just some?
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Old 26th January 2009, 09:06 PM   #768
Salas is offline Salas  Greece
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Only the gain stages JFETs must be matched. The buffer one and the Zener CCS one, no problem. Just don't use extremes for those.

Wait for 48 hours of total play before you substitute any passive part. It will open up and mellow significantly.
For nice mids, your R input load, 47k series RIAA resistor, 16n RIAA cap and interstage cap are crucial. At least Kiwame, Silver Mica, and K40u-9 PIO. Also listen without your extra 150pF input cap. The Grado has low inductance, I don't think that the cap is doing any good there.
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Old 26th January 2009, 10:51 PM   #769
RCruz is offline RCruz  Switzerland
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Default 1st PCB ever

My first atempt on the schunt pcb.

It is the pdf image in negative

Hope the circuit is ok.... I had to hand paint everything over the lazer transfer because it was full of flaws.... I added some gotic artwork !

Ricardo
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Old 26th January 2009, 11:00 PM   #770
Salas is offline Salas  Greece
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Hey, hey, hey, RCruz decided to take the situation in control! Congrats. Get a black pen and touch up any tiny voids in black if you have...
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