Pinnochio i use Jung super regulators on my Dac because Borbely super shunts don't fit in the DAC chassis. ( my next build is Twisted Pear Buffalo As you have - with Borbely all jfet IV and Super shunts) Yes you can use the Clarity's and just remove the 220ufs on the output of the cap multiplier - try that to get a sense of the preamp powered by just film caps - you need to keep the 2 electrolytics that bypass the resistors to ground. But you do need a very good regulator in front of it -or the preamp will lack bass and dynamics because the output cap is now so small it relies more on the preregulator as part of it's performance. John used a shunt in the Blowtorch ( I believe after a LM 317 pre pre regulator so he used in total 3 active stages of regulation and filtering along with chokes as well ) You can get 30 volts out of a Jung if the components ( caps ) are rated correctly and resistors appropriately scaled
- watch out for the current source in the Jung regulator it may need a lower resistor value to source more current to the pass transistor base - you'll know if it needs it because it will work fine without a load or lightly loaded, but fails to regulate when fully loaded - you'll think some thing you did in the build is wrong, but it can be the pass device being base current starved. Read Walt's current sources articles there are better low capacitance TO 92 transistors to use for the current sources ( not the pass devices) SanyoS A1016 and 2SC 2362, their pinout requires lead bending, but not too bad.
I've heard there is a version of the Jung regulator that used film caps and fewer electrolytics to remove the electrolytic DA and sonic signature, but it was never released because it's too prone to ossicilate when parts substitutions are made.
From what I can see of John's Vendetta phono and Blowtorch the final regulator in each is the cap multiplier with a 0.1 Relcap output cap -in previous comments John prefers Relcaps.
Also the MIT RTX polystyrenes aren't too expensive or large in size .
- watch out for the current source in the Jung regulator it may need a lower resistor value to source more current to the pass transistor base - you'll know if it needs it because it will work fine without a load or lightly loaded, but fails to regulate when fully loaded - you'll think some thing you did in the build is wrong, but it can be the pass device being base current starved. Read Walt's current sources articles there are better low capacitance TO 92 transistors to use for the current sources ( not the pass devices) SanyoS A1016 and 2SC 2362, their pinout requires lead bending, but not too bad.
I've heard there is a version of the Jung regulator that used film caps and fewer electrolytics to remove the electrolytic DA and sonic signature, but it was never released because it's too prone to ossicilate when parts substitutions are made.
From what I can see of John's Vendetta phono and Blowtorch the final regulator in each is the cap multiplier with a 0.1 Relcap output cap -in previous comments John prefers Relcaps.
Also the MIT RTX polystyrenes aren't too expensive or large in size .
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@ticknpop, thanks for the feedback!
To all of you building the preamp and not wanting to source the 2SK389/J109 and instead use the 2SK170/J74. If you want to keep this in thermal bond, here's a nice sink I found on another thread.
I'm about to order 12 of Type 0. If anyone wants some, please let me know (North America only please).
Here's the link to thread. See post #237
http://www.diyaudio.com/forums/group-buys/135359-toshiba-dual-jfet-heatsink-24.html
Thanks
Do
To all of you building the preamp and not wanting to source the 2SK389/J109 and instead use the 2SK170/J74. If you want to keep this in thermal bond, here's a nice sink I found on another thread.
I'm about to order 12 of Type 0. If anyone wants some, please let me know (North America only please).
Here's the link to thread. See post #237
http://www.diyaudio.com/forums/group-buys/135359-toshiba-dual-jfet-heatsink-24.html
Thanks
Do
Hi JC,
Could you please give me some pointers... Need a little help if you don't mind...
I've changed the feedback resistors to change the gain from 15x to 5.7x and all is fine with one of the JC-80 amp but the second one seem to sag at a specific volume level. Volume is 20K on input.
What I'm seeing is up to a certain level, the image is centered but then at the 31.5dB everything shift to the left channel and very little can be heard from the right. I've changed the volume ladder and same issue. Changed all connected equipment and same issue.
Changed my 2SK389 and J109 to dual 2SK170 and J74 but same issue... The only thing left to change is the IRF9610 / 610 but I cannot find where to buy good matched sets as I don't want to match them by myself. I was buying them from TechDIY but he does not have anymore...
This particular amp always had this issue from the beginning but with a gain of 15x it was much less pronounced.
I don't know if I should change all resistors and IRF output Mosfets... Is there a drop in replacement for the IRF9610/610 that is better more linear? I've heard 2SK2013 / J313 ??
The other amp seems to be behaving just fine
heeeeeellllpppppppp please!
Do
Could you please give me some pointers... Need a little help if you don't mind...
I've changed the feedback resistors to change the gain from 15x to 5.7x and all is fine with one of the JC-80 amp but the second one seem to sag at a specific volume level. Volume is 20K on input.
What I'm seeing is up to a certain level, the image is centered but then at the 31.5dB everything shift to the left channel and very little can be heard from the right. I've changed the volume ladder and same issue. Changed all connected equipment and same issue.
Changed my 2SK389 and J109 to dual 2SK170 and J74 but same issue... The only thing left to change is the IRF9610 / 610 but I cannot find where to buy good matched sets as I don't want to match them by myself. I was buying them from TechDIY but he does not have anymore...
This particular amp always had this issue from the beginning but with a gain of 15x it was much less pronounced.
I don't know if I should change all resistors and IRF output Mosfets... Is there a drop in replacement for the IRF9610/610 that is better more linear? I've heard 2SK2013 / J313 ??
The other amp seems to be behaving just fine
heeeeeellllpppppppp please!
Do
Is that an EB all jfet power regulator or EB old power supply regulator LM317 based
It's Erno's all fet Super Shunt.
Be carefull the original used 2SK389 amd 2SJ109 unobtainable dual Toshiba jfets. Even the single jfet substitutes 2SK170 are getting harder to find, the 2SJ74 are discontinued and hard to come by. The pass devices are 2SJ313 and 2SK2013 Toshiba Fets - again discontinued so you need a stash of Japanese jfets and fets if you want to build them. They are very good - my Borbely DAC, phono stage, crossover, with Borbely and Blowtorch preamps run on 16 of them. As I listen to them at this moment I never cease to be amazed. I got some of Evul's dual jfet heat sinks a couple of years back - they help.
Be carefull the original used 2SK389 amd 2SJ109 unobtainable dual Toshiba jfets. Even the single jfet substitutes 2SK170 are getting harder to find, the 2SJ74 are discontinued and hard to come by. The pass devices are 2SJ313 and 2SK2013 Toshiba Fets - again discontinued so you need a stash of Japanese jfets and fets if you want to build them. They are very good - my Borbely DAC, phono stage, crossover, with Borbely and Blowtorch preamps run on 16 of them. As I listen to them at this moment I never cease to be amazed. I got some of Evul's dual jfet heat sinks a couple of years back - they help.
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Borbely DAC is I/V stage and output buffer only. It replaces the output stage of other 's CD players or DAC's . I use it in an Assemblage DAC 3.1 with balanced BB 1704 and Pacific Microsonics PMD 200 which i feed the digital front end with Dexa regulators because theres no room.
I am working now on Twisted Pear buffallo 3 with Borbely super shunts for the Borbely outout stage and Borbely shunts for the digital board - just needs 1 of 5 volt supply to feed on board Trident shunts so even dual mono is not bad for space and parts.
I am working now on Twisted Pear buffallo 3 with Borbely super shunts for the Borbely outout stage and Borbely shunts for the digital board - just needs 1 of 5 volt supply to feed on board Trident shunts so even dual mono is not bad for space and parts.
Borbely DAC is I/V stage and output buffer only. It replaces the output stage of other 's CD players or DAC's . I use it in an Assemblage DAC 3.1 with balanced BB 1704 and Pacific Microsonics PMD 200 which i feed the digital front end with Dexa regulators because theres no room.
I am working now on Twisted Pear buffallo 3 with Borbely super shunts for the Borbely outout stage and Borbely shunts for the digital board - just needs 1 of 5 volt supply to feed on board Trident shunts so even dual mono is not bad for space and parts.
I am working now on Twisted Pear buffallo 3 with Borbely super shunts for the Borbely outout stage and Borbely shunts for the digital board - just needs 1 of 5 volt supply to feed on board Trident shunts so even dual mono is not bad for space and parts.
I'll send you the schematics and show you what I've changed. I'll do this tonight
Thanks
Do
Hi John,
Just sent you a PM.
Basically, all sims were done in PSpice in this post # 101
http://www.diyaudio.com/forums/analog-line-level/206797-jc-80-ebay-pcbs-power-train-11.html
and on post # 100 sims had done this ""If you reduce the value of R17, R18, R19 and R20 to 330 ohms, it will drop the gain to about 5.7x (15.2dB)" from 15.3X. This also increases the bandwidth from 2Mhz to 15Mhz which is not always better...
So if I have my two JC-80 playing music, up to a certain level voices and whatever instruments that are usually centered in some music pieces slowly start shifting from right to left when increasing the volume to a certain level. Then it goes from bad to ugly as if one of the amps gain is not capable of following. Almost sagging... I've changed all the gears around but nothing will do... No I'll check if there's a voltage drop but I did change PSUs and same results. Thinking it was my R2R ladder I swapped the R2R modules left to right and the problem remained on that channel then swapped the JC-80 and then it followed...
I don't know what to try next. R17, R18, R19 and R20 set the gain which was initially to 15.3X so I lowered to ~5.7X.
This volume shifting was always there but much worse now that I have changed the gain... Could it be the opamp in the servo? I've soldered a few times on one of the pads of the opamp... Could heat damage on the opamp cause this kind of issue?
Thanks for your support
Do
One testable thing that would give those symptoms is if one channel of electronics is loading the volume control too heavily. Can be tested by replacing the volume control with fixed resistors in line from source switch to electronics, maybe about 100K to 1M Ohms. This will exaggerate differences in input impedance to make them more audible.
All good fortune,
Chris
All good fortune,
Chris
I was going to buy a Goldpoint attenuator for something else but could use it for testing?
Do
The theory to be tested is that one amplifier channel's input impedance is too low, and is loading down the signal from the volume control. This loading will be greatest where the volume control's output resistance is greatest. With an AC voltmeter or a scope this is trivially easy to test. Without either, a believable test would be to feed both channels' amps from identical large fixed resistors and to listen.
If you hear a significant difference, the next step is to figure out what's causing the impedance imbalance. On a new DIY construction this is almost certainly a wiring error. I personally *never* make any mistakes, but I've known people who might make a little tiny error occaisionally.
All good fortune,
Chris
I think that Chris is on to something important, Penn. Please check it out. Your problem is something like that, I suspect.
As far as getting into 'tweaks and mods' to improve this design as it is presented here, I am not well equipped, at the moment, to offer any.
Even the circuit boards offered here originally, have significant, and perhaps necessary changes to them, that differ from the original JC-80 design, and enthusiasts seem to have taken to doing even more changes, and I just don't have the time or energy to follow all of them. However, I think I should put up the original JC-80 circuit circuit schematic, just for comparison, when I find the file.
As far as getting into 'tweaks and mods' to improve this design as it is presented here, I am not well equipped, at the moment, to offer any.
Even the circuit boards offered here originally, have significant, and perhaps necessary changes to them, that differ from the original JC-80 design, and enthusiasts seem to have taken to doing even more changes, and I just don't have the time or energy to follow all of them. However, I think I should put up the original JC-80 circuit circuit schematic, just for comparison, when I find the file.
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