This is an Idea for a Mu-Stage based on the 10M45 chip in place of a Mosfet
(Ref: MU stage Philosophy by Alan Kimmel)
I have not tested this… need to order some parts.
Just wanted to get some feedback from any one that had made a SS Mu-Stage
In general… think this will work?
Also, if I understand it right, the Mu-Stage sets the current 3 or 4 times higher than what V1 needs, then just drains off the extra current via RS1 (the 42K in my schematic)
What is the benefit of setting the current 3 or 4 times higher and just draining off the excess?
(Ref: MU stage Philosophy by Alan Kimmel)
I have not tested this… need to order some parts.
Just wanted to get some feedback from any one that had made a SS Mu-Stage
In general… think this will work?
Also, if I understand it right, the Mu-Stage sets the current 3 or 4 times higher than what V1 needs, then just drains off the extra current via RS1 (the 42K in my schematic)
What is the benefit of setting the current 3 or 4 times higher and just draining off the excess?
Attachments
Benfit is that anode loading is resistor to ground parallel with cathode resistance. More linear but less gain. Also without this resistor one would be forced to use DC feedback to set anode DC current of the same to CCS.
I got the idea of the 10M45 as a ccs from tubelab, and use it now as a ccs for my 6sl7
Grounded cathode amp... Yes, it works great.
I did not find anything on tubelab where the audio signal actually comes off the ccs device…. That is what I’m trying to accomplish here.
Grounded cathode amp... Yes, it works great.
I did not find anything on tubelab where the audio signal actually comes off the ccs device…. That is what I’m trying to accomplish here.
I routinely use the IXYS chip for plate loads, but I have not tried this Mu Stage circuit. I tried several similar circuits that used pentodes wired as CCS's but none of them could drive a DHT well into A2, which was the reason for my experiments at the time. After I added a mosfet follower (PowerDrive) I never went back and experimented with other CCS loaded circuits.
I have seen a circuit similar to this on the web somewhere, except it did not have the current bleed resistor.
When attaching the CCS directly to the plate, a cathode bypass capacitor is needed. You may, or may not need it in this circuit. It affects the gain and the third harmonic distortion.
I have seen a circuit similar to this on the web somewhere, except it did not have the current bleed resistor.
When attaching the CCS directly to the plate, a cathode bypass capacitor is needed. You may, or may not need it in this circuit. It affects the gain and the third harmonic distortion.
I use them them too and also learned of them from tubelab, but I'm sure he mentioned it in a one-liner somewhere. I'm guessing it wasn't pursued in depth because he already has his Powerdrive circuit.
3 minute late edit: Ooops, now there's bad timing. I know someone tried this.
3 minute late edit: Ooops, now there's bad timing. I know someone tried this.
Thanks Guys...
Just ordered the parts, I will let you know in a week or two
if this works or not!
Just ordered the parts, I will let you know in a week or two
if this works or not!
You would do a lot better using two 10M45S in a casocde arrangement (lowers the shunt capacitance) and taking the output from the top of the current set resistor.
The attachment shows DN2540 depletion mode FETs used in this manner. However the circuit is equally applicable to the 10M45S(an enhancement mode FET with an error amplifier which mimics a depletion mode FET). This arrangement works beautifuly and has a very low output impedance.
The attachment shows DN2540 depletion mode FETs used in this manner. However the circuit is equally applicable to the 10M45S(an enhancement mode FET with an error amplifier which mimics a depletion mode FET). This arrangement works beautifuly and has a very low output impedance.
Attachments
Might be wirth reading (http://www.audioasylum.com/forums/bottlehead/messages/108492.html) the sub thread "What does this mean"
I think Doc B's bin' overdosing on the triple chocolate fudge sundays again ! The 10M45s has an impedance of over 10Meg over much of the audio range, and measures around 7 Meg @10Khz.
See this link for details
http://www.pacifier.com/~gpimm/ccs_performance.htm
This figure is substantially increased in the cascode arrangement.
As for them blowing up all the time, all I can say is that I have had zero failures in over 60 chips using plain old 510R carbon comps as 'gatestoppers'.
See this link for details
http://www.pacifier.com/~gpimm/ccs_performance.htm
This figure is substantially increased in the cascode arrangement.
As for them blowing up all the time, all I can say is that I have had zero failures in over 60 chips using plain old 510R carbon comps as 'gatestoppers'.
Once I figured out the gate stopper thing the only ones that I have blown up were provoked by probing around in the circuit with the power on. Sparking the gate treminal to the drain will do it every time. I have built a dozen or so amplifiers with them as the plate load for a 5842 or 12AT7 at 10 mA. I have built two amps with them as the load for a 45 at 35 mA. None have failed.
I have a test design using one in a hybrid CCS with a 6LW6 pentode. It is adjustable to 100 mA and operates with 750 volts on the plate. I haven't zapped it yet.
I have a test design using one in a hybrid CCS with a 6LW6 pentode. It is adjustable to 100 mA and operates with 750 volts on the plate. I haven't zapped it yet.
On the very first plan, I don`t quite what will be the advantage of using a 7.5K resistor. Since the 10m45 will act as a "perfect" current source, why not forget the resistor and only use the 270R for setting the correct current
Maybie, I missing something here...
Could you guess "low output impedance"
I`m currently thinking about substitute my plate choke for CCS in my preamp and I wonder if the Gary Pimm CCs would be a good choice or if the 10m45 will deliver about the same performance.
(when talking about ccs, I`ll usde the low output impedance output)
Maybie, I missing something here...
Could you guess "low output impedance"
I`m currently thinking about substitute my plate choke for CCS in my preamp and I wonder if the Gary Pimm CCs would be a good choice or if the 10m45 will deliver about the same performance.
(when talking about ccs, I`ll usde the low output impedance output)
etalon
I agree entirely.
I haven't measure the output impedance, but it should only be in the order of a few hundred ohms (depending on the tube). If you don't need a low output impedance, try taking the output from the bottom of the current set resistor as well to see which arrangement you prefer.
Why don't you try the 10M45s circuit first to see if you prefer the sound of a ccs to your choke (it's a very cheap experiment), then build Gary's ccs if it works out.
I agree entirely.
I haven't measure the output impedance, but it should only be in the order of a few hundred ohms (depending on the tube). If you don't need a low output impedance, try taking the output from the bottom of the current set resistor as well to see which arrangement you prefer.
Why don't you try the 10M45s circuit first to see if you prefer the sound of a ccs to your choke (it's a very cheap experiment), then build Gary's ccs if it works out.
mach1 said:
Yes, I see that the output should come off the top of the current set resistor, and I will re-do my Schematic using 2 10M45's
I don't understand how the the schematic #2 (mach1) is a mu-follower.
I looks to me like the output would just go through the current setting resistor.... another words we have a ccs loaded grounded cathode amp.
Please telll me I'm missing something here!
With the schematic #1, the output travels from the plate of V1 through the 10M45 via a cupling cap, then out of the cathode "K" of the 10M45
So the 10M45 is acting like the top valve in a grounded cathode - cathode follower config.
Sqerus
You can take the ouput from the top or bottom of the current set resistor.
If you connect to the top you get a low output impedance a la mu stage - however the downside is that you lose the psu isolation that a ccs normally affords
If you connect to the bottom you get a high output impedance roughly equal to the tube's Ri - however the signal is isolated from the psu.
The two factors you are trading off are output impedance and psu isolatation. That's why I suggest that you try both and see which works out best in your application - it only takes seconds to change the connection.
You can take the ouput from the top or bottom of the current set resistor.
If you connect to the top you get a low output impedance a la mu stage - however the downside is that you lose the psu isolation that a ccs normally affords
If you connect to the bottom you get a high output impedance roughly equal to the tube's Ri - however the signal is isolated from the psu.
The two factors you are trading off are output impedance and psu isolatation. That's why I suggest that you try both and see which works out best in your application - it only takes seconds to change the connection.
Hi
Being out of town for next 4 month, I only have my laptop and cheap bookshelf speaker.
I tried it on my low-fi amplifier (USB DAC, 6J1 triode wired loaded by the 10M45, el84 triode wired )
So with a low fi "travel system" my result aren`t 100% accurate but I did hear a difference
To me, the result were clear, the LowZ output sounded better. Not a lot but the lower medium and the subjective extention in the bass convinced me.
Theses result were with a cheapos chinese tube driving the easy load that the el84 represent. I`m looking foward to try it on my preamp and even in my main amp to hear real result.
I`m pretty sure that my preamp (10K Zout) could sound better. Just to see if the CCS will destroy the lovely sound I get from a choke loaded 201A.
Being out of town for next 4 month, I only have my laptop and cheap bookshelf speaker.
I tried it on my low-fi amplifier (USB DAC, 6J1 triode wired loaded by the 10M45, el84 triode wired )
So with a low fi "travel system" my result aren`t 100% accurate but I did hear a difference
To me, the result were clear, the LowZ output sounded better. Not a lot but the lower medium and the subjective extention in the bass convinced me.
Theses result were with a cheapos chinese tube driving the easy load that the el84 represent. I`m looking foward to try it on my preamp and even in my main amp to hear real result.
I`m pretty sure that my preamp (10K Zout) could sound better. Just to see if the CCS will destroy the lovely sound I get from a choke loaded 201A.
etalon,
It's good to hear that being on the road doesn't keep diy diehards from their hobby.
Don't forget that when you replace the plate choke in your preamp with a ccs you will need approx twice the B+ voltage.
It's good to hear that being on the road doesn't keep diy diehards from their hobby.
Don't forget that when you replace the plate choke in your preamp with a ccs you will need approx twice the B+ voltage.
Hi Sgerus and Mach1,
Have you implemented the 2 10m45s in cascaded arrangement yet? Thanks.
Regards,
T.C. MA
Have you implemented the 2 10m45s in cascaded arrangement yet? Thanks.
Regards,
T.C. MA
No...
I gave up on that idea and decided not to use and SS parts in my amp.
Ended up a MU-Follower using my 6sl7.
To me, this sounds better than the SS CCS I started with.
I gave up on that idea and decided not to use and SS parts in my amp.
Ended up a MU-Follower using my 6sl7.
To me, this sounds better than the SS CCS I started with.
sgerus said:
Hi Sgerus,
Thanks for your reply.
Can you elaborate more how the MU-Follower sounds better than the SS CCS (single 10M45s?)?
Maybe the 2 10M45s in cascaded arrangement (much lower shunt capacitance) can take away the ss sound? See the post of Gary Pimmes here:
http://www.diyaudio.com/forums/showthread.php?s=&postid=624299&highlight=#post624299
Regards,
T.C. MA
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