new jc circuits

All the parts have to be put together at some point. Have fun!
nanana
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new jc circuits

Post by nanana »

hey all,
i am going to etf tomorrow and, on saturday, will discuss a few new ideas that have been turned into products at silbatone. i wanted to post some of them here so that dave's crowd can have a gander at the same time as the etf people.

as some of you know, i have been designing some things for this most remarkable korean company... i am an old school pocket calculator guy and have only just begun to use sims, thanks to dave and stephie. i tend to build first and analyze later. all these circuits work (they have already been built) and there is some difference between the sims and reality of course... but i hope, with your help, to better understand the ins and outs of these circuits.

this first one is a phono stage. the idea is the lcr network is at the output of the trans.
Attachments
test.asc
new jc circuits
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nanana
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more

Post by nanana »

here are the next variations....

these are triode, cascode and folded cascode.

the folded cascode hybrid is the most interesting one for me. the distortion can be nulled to an enormous degree.

this has been built using a 2SJ72 and an 8416 (12v version of 6922)
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test3.asc
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test3b.asc
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test3c.asc
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nanana
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Post by nanana »

here is the other dc approach. i can post a pic of the board i did for silbatone. this is the "budget" phono. i have done both preamps and amps using this method of direct coupling. it works great with a 6AL5 or a WE412 for the diode splitter. you don't half to use solid state. i also have a servo'd cathode follower buffer that can replace the transformer out. i like the trans because it gives you the rumble filter built in.
Attachments
dc phono.asc
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nanana
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Post by nanana »

here is a pic of the pc board
Attachments
here's a pic of the board
here's a pic of the board
dumping fono.jpg (141.34 KiB) Viewed 11652 times
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nanana
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Post by nanana »

whoops! that's the outside. here's the pc board for the phono
Attachments
phono1.jpg
phono1.jpg (94.93 KiB) Viewed 11647 times
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reVintage
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Post by reVintage »

Hej!
Your circuit will not in any way work in its present form. A pentode must have a defined voltage on top. Either a resistor or a gyrator. With a current source Ua will be all over the place. Also a pentode needs loading to work with low distortion.

In my example I have used tubes suitable for this application: D3a(can also be an E280F), E88CC and 6N30.

But I must admit I don´t fully understand if the floating last part will work :?:.

The way I see it your phonostage is NOT dc due to C4. You can simplify it by moving this cap to between the second and third stage. You can then remove the cathode follower and the second floating voltage source.

I have also added a resistor to compensate for the 4th time constant.

See example 2.

Lycka till med ditt fina bygge med supersnygga kretskort!
Attachments
dc phono2.asc
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dc phono.asc
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dcphono.png
dcphono.png (112.42 KiB) Viewed 11633 times
Brgds
Lars
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Post by dave slagle »

Hey Lars,

Not only does it work, I heard it at CES last year.

dave
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reVintage
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Post by reVintage »

Hey Dave,

Haven´t seen you around for a while.

Of course it will make noise. Maybe you listened to something with other component values than here.

Still A CCS on top of pentode is an absolute nono, load has to be substantialy low and it is still not DC-coupled.Think you showed the loading thing in an earlier thread. Without load you will get gross distortion.

The adjusted one I did above indicates many times lower THD and a reasonable gain in contrary to the first with over 50dB. Another flaw is the thing below the CF that hasn´t very high impedance like a CCS should have.

EDIT: Came to think about a way to keep the CCS. Run the anode load to ground instead. Still has to be like my optimal load for D3a,10k.
Attachments
dc phono2.asc
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Brgds
Lars
nanana
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Post by nanana »

hahahhaahhahah,
lars, you crack me up! they all work really well. but you are absolutely right about C4. that design is not honestly direct coupled. it does allow the filters to be implemented as if it was, though, and that is useful.

the pentode and fet cascode circuits all work extremely well, but you are missing some important details when it comes to why. the pentode/cascodes are optimized as variable current sources. the fixed current source draws more than the bias allows the pentode. where is the current difference? the shunt resistor. that is the key. the gain is the slope of the delta of the transconductance. the transfer characteristic is a straight line. shall i post x/y fotos? when i come home from etf... people here are listening to it as we speak. gain of 1000 and no feedback, 0.2% thd. with a 1/12 SUT, there's a good S/N. there are some caveats, but they are interesting circuits. i have more coming.
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nanana
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Post by nanana »

also, lars, you completely missed the beauty of the reversed diodes... diodes leak, remember. they are analog devices and not perfect. and thank goodness too. i have been doing that circuit for amps since the early 90's. i just wish i could get rid of C4. for the amps i did, but its not stable enough for pre amps. C4 insures it works, by the way. look again.
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nanana
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Post by nanana »

lars, did you run the asc.s? they all work, it's just that the pentode gain is much lower than in reality. these have all worked long before i could use spice. i only just started learning how to use ltspice. dave and stephie are teaching me to do it!
your,
jc
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reVintage
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Post by reVintage »

the shunt resistor.
N,


hahahahah, you really crack me up. Didn´t you check my last .asc/post where I say shunt is the solution. So if you run the input device at extremely low current the 100k will work.

As I have no knowledge in sand, please explain what the diodes do.

So when C4 is actaully in the signal chain why just do as I recommend and use a small plastic at the input of the last triode?

So check my suggestions carefully, they indicate THD many times lower than you states. But we shouldn´t take THD sims to serious just as indications.

So if you have built it from the 90,s maybe it is time for refreshment :wink:.

Hope to continue discussing with you! If you want check my sims I canmail you 6N30. The others you will find here.

Dave, couldn´this very interesting thread be moved to the Phono-section?
Brgds
Lars
sbench
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Post by sbench »

Cute stage, jc! The only electrical quibble I would have with it is that there will be occasions where you overvoltage the 2N4393, due to pops, ticks or whatever. Put in a large input voltage and not the drain source voltage on the FET. It'll work, but you might see short lifespan on those parts.

Enjoy the ETF. I sure wish I were there, darnit.

Stephie <3
nanana
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Post by nanana »

hey stephie!
i wish you'd a been there too! it was fun and i met a lot of new friends. it's a special thing they have going on there... non-commercial/competitive and also at a high level. menno and frank blöhbaum were both showing wild stuff... (arta, a measurement program, and frank had a cool preamp) lots of whacky machines. thomas shick's turntable mods (lenco, amazing)! eckmueller (?) coaxials from 1944... were tremendous.

yes, of course you are so right about the fets. the trans secondary can fly around quite a bit. i have to measure some things but maybe a cascoded fet would be enough? i am more interested in the folded cascode anyway (p fet) and i used the 4393 and the 5460 models only because i don't have a K170 and a J74 model, not that it makes a difference headroom wise. the "normal" power arrangement (B+ instead of B-) works so well, i got a little too excited flipping it upside down.

the pentode circuit is the most fun... the Gm amp thing and the silbatone DA100 amp i talked about at the show will go up here tomorrow, in more detail.

i look forward to meeting up with you at some point. thanks for the help with the spice. you are really giving all of us an amazing gift with your support and wisdom. heal up!

your,
jc
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piotr_grzesik
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Post by piotr_grzesik »

ETF was great, loved your presentation, JC! That pre didn;t sound too bad, either. :D

Some photos from the event, here:

http://s108.photobucket.com/albums/n15/ ... o/ETF2010/

Cheers,
Pete
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J-ROB
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Post by J-ROB »

Your circuit will not in any way work in its present form.
Don't tell that to the 9 people who bought this crazy expensive preamp! They still think it works.

Kudos to jc for busting out with the circuit. If he was coming up with stuff like this in the old days, I might have made it to SP 17.

Next year I will go to ETF, especially if Stephie is going...that event definitely needs more chicks!

J-ROB
nanana
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Post by nanana »

ok, here's the amp circuit. i don't know how to specify transformers in lt spice yet. i can't get it to work/don't know the semantics. so here's a choke loaded output tube... just add the output trans when you edit the asc. and post it so i can learn. maybe slagle can drop in one of his 10k/8ohm models? i am mystified at the results although the dc conditions are spot on! the distortion stuff does not match what i have measured, but who cares? the first tube is a 437, second tube is an Ed (old german 2A3) and the output tube is a DA100.
this can be changed to be to 6C45P, 2A3/45, and GM70. enjoy!
Attachments
DA100 amp.asc
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nanana
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Post by nanana »

how do you take a screen shot? i gotta sleep... i will post a more detailed look at the "Gm amp" tomorrow.
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sbench
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Post by sbench »

Here's a couple mods of the schematic with a 10k to 8 ohm xfmr. You get about 30 watts out as shown.

I added voltages and currents, and made the tube values visible, and labeled a few test points.

Freq response 1dB points show as 10Hz and 45kHz

Enjoy,
Stephie <3
Attachments
DA100 amp[1].asc
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dave slagle
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Post by dave slagle »

hey JC,

The screen grabs are os dependent and on a mac, command shift 4 will allow you to drag over an area to capture.

Stephie did the basics. In spice you "assemble" a transformer by coupling two inductors together with a "k" command.

Image

Look at the input transformer which appears as a pair of 65hy inductors marked L1 and L2. The"K" command above is a coupling command instructing spice to couple L1 and L2 by a factor of 1 (ideal) hence the command K1 L1 L2 1 makes your input transformer do its job.

At the output, I simply added a 36mhy inductor loaded by an 8 ohm resistor and added the new command K2 L4 L5 1 to make it appear as a perfect 10K transformer. A little simple math shows that 10K:8=1250:1=45:.036 so the two inductors coupled with the K2 command behave as a 10K:8 transformer.

I must admit that I am still trying to get my head around the circuit and with the spice file i'm slowly weeding my way through what is going on.

keep up the good work my brother!

dave
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nanana
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Post by nanana »

thanks dave, stephie... i apologize for being such a stubborn luddite. its hard for me to sit down and read the instructions... its more fun reading pippi långstrump to lulu. now i see how you do it. "K" is a coupling factor. and its just the impedance ratio. so simple.

dave, this circuit is super conventional. its just from a B- point of view. its a B+ centric world, you know. it just gives another perspective for direct coupling. the one good thing is its more honest in including the power supply into the circuit. forget about ground and think of the 500 v supply as a small resistor. now, the first stage is a grounded cathode stage with B+ between the load and amplifier. who says it has to be in the same place all the time? its all in series anyway. the whacky thing has to do with the trans secondary. it flies around with the signal gain. stephie busted me on that over the fets in the circuits above.

more soon.
your brother from another mother,
jc
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dave slagle
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Post by dave slagle »

a few other things on the K factor.

if you make the K -1 you reverse phase.
if you make the K 0 there is no coupling.
moving from 0 (none) to 1 (100%) can get any amount of coupling (which equates to leakage inductance)

I get the whole negative supply and ground thing, That PP 6C33 amp I had at noise had an autoformer output and a -230V supply. It just took me a fair bit of time to get the relationships.

see ya at CES!
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nanana
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Post by nanana »

this is the Gm amp schematic. this gives away the whole idea in one easy location. i will explain more. i use a ixycp90 depletion mosfet for the current source. a dn2540, etc. or a pentode, triode jfet combo, will all work. i do not know how to make parts in lt spice yet, but soon perhaps? i really need a model of the 2SK170BL and 2SJ74BL, anyone know how to do that? anyway, the gain is a little higher in reality, but the trend reflects what i have built. these parts values are the same as built and the dc stuff is spot on! bravo lt and sb!
Attachments
Gm amp.asc
here is the schematic
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Gm clip.gif
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nanana
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Post by nanana »

here is a mod of the Gm amp using blohbaums trick of returning the screen current to the plate. the gain is higher and the noise is less. a little less. the transconductance of the transistor is much higher than a tube so the gain is more than the same idea implemented with a tube. i give you the tube version too, and used a 6C45P for the excellent cathode follower performance. please remember that this trick is frank's patent, so don't go selling anything with it. the Gm amp is mine or prior art (haven't seen it before or described as i have...), so HAVE AT IT! make all kinds of stuff. just don't try to patent it or silbatone will cut your nuts off.
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Gm amp 2.asc
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Gm amp rev2.asc
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transistor
transistor
screen circ.gif (136.42 KiB) Viewed 11481 times
tube version
tube version
tube scr circ.gif (135.43 KiB) Viewed 11481 times
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nanana
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Post by nanana »

please understand that i am not one for details and the devil is in the details. the transistor i picked from the list has the hfe but not the voltage ratings. i think a MPSA44 will do the trick. it wasn't on the list. the real gain is somewhat higher in practice... i typically can get 1000 to 2500 gain with low low distortion and wide bandwidth from a D3a. a 6688 gets me 750 to 2000. etc. but it all doesn't matter. i mainly use an E80CF and can get a gain of 250 at .2% distortion. you know what can been done with that? almost anything that needs amplification.

my goal with this is to make vacuum tube op amps for VCO and VFCs. i am working on a modular synth and this circuit is at the heart of it all. i'd like to get close to a gain of 1*10^6 and 0 volts out with as few tubes as possible. this makes it easier.

jc
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pentofax
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GM pentode circuit

Post by pentofax »

Hi JC,

that`s my first time login here. It was great to meet you @ ETF!
the Gm amp is mine or prior art (haven't seen it before or described as i have...), so HAVE AT IT! make all kinds of stuff. just don't try to patent it or silbatone will cut your nuts off.
Prior art is right. I have used this gm-circuit since 2002. It appeared officially in my TEM3200 power amp at the Munich High End Show in 2005. As you know, if a circuit or any other technical solution appears inside a commercial available product it`s not possible to patent it anymore. And I shared this idea with some of my friends - before Silbatone appaered with it. So if Silbatone filed any patent about the GM stage (or anybody else), it will not be possible to grant it.

I fully believe, that you have had this idea absolutely by your own. Sometimes the same ideas appear at different locations on this planet. But patenting this is another story.

My Phonostage, which I just presented at the ETF, works with such transconductance stages in all 4 gain blocks. It was great to compare my phonostage with the one from Silbatone at the ETF. I get about 4500 gain for my PFL200 implementation. The D3a makes even more. And of course I use the trick with the BestPentode transistor. The MPSA44 transistor for transferring back the screen grid current to the anode has more than just noise advantages (by the way, any noise improvement is very welcome in phonostages):

a) it gives you additional gain following the ratio of Ig2 / Ia
b) the circuit has a MUCH better power supply rejection ratio! Why? Because now there is only the current source left between power supply and the signal output. In other words: theoretical there is indefinite high PSRR! Practical it is very much. Consequently I have practically almost no hum nor noise at the output of my phonostage.

As you know, this patent stuff is important for commercial use only. Of course all the DIY guys are invited to use my circuit for their own use as well. I already emphasized this at the ETF2009, where I presented the partition noise avoiding trick (see also my article in LinearAudio published by Jan Didden).

Best Regards, Frank
nanana
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Post by nanana »

hey frank, it was so great to meet you and mind blowing to see your work... i am happy to say i was able to hang out with the big cheeses in stella plage.

silbatone has no patent and would never do that. just wouldn't want anyone else to prevent it or anyone else from working. not to mention, chances are that some old radio guy has done it anyway, and never got any admiration for it.

if you did it when you say, you beat me to the Gm amp, i did it first in 2004. although i was thinking about it since i worked for dick sequerra. and as for the screen summing circuit. i would never use your circuit in my own stuff, frank. i don't work that way. everyone who knows me will tell you that. i do think its clever... you got a thing going on man!
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pentofax
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Post by pentofax »

Hi JC,

just trying to attache an image, I hope it will work. It shows the fully isolated B+ power supply when using this little extra transistor. I use PSpice instead of LTspice, so I cannot post an .asc file.
Attachments
BP_CS_PSRR_v1.jpg
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pentofax
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Post by pentofax »

Great, the picture posting works!

Here come some measurements of my PFL200 GM-stage, which I use in my phonostage. It shows first the open-loop frequency response. The -3dB corner frequency @ open-loop (gain = 73dB) is 13kHz. All in all it beats nearly all semiconductor OPamps in terms of bandwidth and linearity - and it has just one gain stage. The L system of the PFL200 is used for the buffer (very low input capacitance ensures high bandwidth...).


The second picture shows the open-loop gain spectrum measured with the Rohde & Schwarz UPL. The CH2 is the input signal (326.3 µVp) and CH1 the output signal (1.4056Vp). The overall gain for this particular tube was 1.4056 / 326.3µ = 4307 or nearly 73dB. There is almost no THD measurable!
The circuit is absolutely stable in any way (DC, HF) even in open loop connection. The working resistor of the pentode equals to 470k.

The second pic shows the same stage having the feedback closed to a gain of nearly 91 or 39.2dB. Please take note the incredibly low noise and THD and the great hum supression (no shielding box!).



Best Regards, Frank
Attachments
PFVAL10.jpg
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PFL200_VALVO10_OpenLoop470k_THD.jpg
PFL200_VALVO10_OpenLoop470k_THD.jpg (77.42 KiB) Viewed 11433 times
PFL200_VALVO10_OpenLoop470k_FreqMax.jpg
PFL200_VALVO10_OpenLoop470k_FreqMax.jpg (71.38 KiB) Viewed 11433 times
sbench
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Post by sbench »

Cute circuit. The points about noise and power supply rejection are all good advantages. In principle, there is only one functional disadvantage. The anode voltage cannot drop lower than the g2 voltage in this circuit whereas in a standard pentode or the first implementation not returned to the anode, the anode voltage can drop below the g2, thus providing slightly improved dynamic range. In reality, probably not terribly important, but I know some folks who use that "advantage" of pentodes by appropriate bias points.

Stephie <3
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