current draw
Hi... !
Just to add a further tought, because of the latest post.
First, I would sincerely doubt that there is a Broskie Autobias circuit... maybe John has patented the circuit (no pun intended)? And what autobias circuit whould that be, the one related to fixed bias autobiasing, or the one related to automatic bias autobiasing? You know, there are a lot of other people, of which some did it commercially (i.e. Bill Beard of Beard Audio, and many others...), who did something about autobiasing circuits
Further, I did not try any of the mentioned approaches for myself, since I have never had the need: with cathode resistors there is no particular need to improve on the current draw, unless you are into PP amps, which I am not, definitely... but, I can tell you that when 6C33C start to drift, and they start immediately, especially if not new or in particularly good condition and shape, meaning each and every one of them directly out of the box -- they drift considerably... and I sincerely doubt that the effects of an autobias circuit for fixed bias applications like the ones described by Broskie (or made by others) would do the trick, and would not be audible while doing the trick: we are talking about serious instability here...
Best regards to all,
Aleksandar
Hi... !
Just to add a further tought, because of the latest post.
First, I would sincerely doubt that there is a Broskie Autobias circuit... maybe John has patented the circuit (no pun intended)? And what autobias circuit whould that be, the one related to fixed bias autobiasing, or the one related to automatic bias autobiasing? You know, there are a lot of other people, of which some did it commercially (i.e. Bill Beard of Beard Audio, and many others...), who did something about autobiasing circuits
Further, I did not try any of the mentioned approaches for myself, since I have never had the need: with cathode resistors there is no particular need to improve on the current draw, unless you are into PP amps, which I am not, definitely... but, I can tell you that when 6C33C start to drift, and they start immediately, especially if not new or in particularly good condition and shape
, meaning each and every one of them directly out of the box -- they drift considerably... and I sincerely doubt that the effects of an autobias circuit for fixed bias applications like the ones described by Broskie (or made by others) would do the trick, and would not be audible while doing the trick: we are talking about serious instability here... Best regards to all,
Aleksandar
This will happen only if either you run them at very high current and high dissipation and/or if you don't burn in them correctly.
I have experience of 30+ 6C33C tubes that all show very small drift in my application, (SE and OTL amps) but I am very careful to burn them in correctly and I don't use more than 40-50W dissipation for each tube. It seems to be very important to bake them out with only heater power applied for at least one hour before applying anode power.
Regards Hans
Actually I did experiment with some of the autobias circuits on the Tubecad web site a few years ago. Some were quite complex, that adjust the grid bias in response to changes in cathode current. They are pretty complicated and prone to oscillation and sudden death. Some of the simple circuits are basically CCS's in series with the cathode. These work, but you still dissipate the same power in the cathode circuit as a big resistor. The big resistor does work, but dissipates about 10 watts per tube.
For now I have put the regulator triodes aside, since I have thousands of tubes to play with. I have a large box full of 6AS7G, so I will experiment with these again at a later date.
For now I have put the regulator triodes aside, since I have thousands of tubes to play with. I have a large box full of 6AS7G, so I will experiment with these again at a later date.
INFAMY?
Hi to all!
At the cost of it being an infamy...
You know, I used to like J. Broskie... but our paths diverged. He is too much into his own stuff, and I am too much into mine.
At the bottom, it says "All rights reserved" -- whatever that means. In the text, he says that he does not believe in patents... but his friends (a story I've already heard or read on his pages") blah, blah.
And above -- support the journal by buying software... he means "support the writer", but says "journal". A pityful excuse.
I've got nothing against him, or his work... but I do think that people should talk straight, not beat round the bush. GIVE ME SOME MONEY if you like my products... that is correct way to say it. Or is it that in the USA it is politically correct to be a beggar?
Regards to all,
Aleksandar
Hi to all!
At the cost of it being an infamy...
You know, I used to like J. Broskie... but our paths diverged. He is too much into his own stuff, and I am too much into mine.
At the bottom, it says "All rights reserved" -- whatever that means. In the text, he says that he does not believe in patents... but his friends (a story I've already heard or read on his pages") blah, blah.
And above -- support the journal by buying software... he means "support the writer", but says "journal". A pityful excuse.
I've got nothing against him, or his work... but I do think that people should talk straight, not beat round the bush. GIVE ME SOME MONEY if you like my products... that is correct way to say it. Or is it that in the USA it is politically correct to be a beggar?
Regards to all,
Aleksandar
I'm not sure why you're conflating the copyright notice and JB's musings about patents. One has nothing to do with the other.
I also don't see the "begging" you're referring to, only some soft-sell pitch for the product John sells, his software. And that's sold at a pretty reasonable price (strictly IMO).
I also don't see the "begging" you're referring to, only some soft-sell pitch for the product John sells, his software. And that's sold at a pretty reasonable price (strictly IMO).
Web space costs money. You can use a free hosting service which is supported by some one else's advertizing, or you can pay for web hosting and advertize your own products. What is the difference. The site viewer is always free to ignore the advertizing.
I have purchased 3 of the Tubecad simulators, and found that they work well. I personally think that his web site and the time that he invested in it was worth the money that I sent him. Some of his ideas may be different, but they make you think.
I have been funding my web site out of my own pocket for 3 years. I have come to the point where the material that I want to add to the web site will raise the cost, which I can recover by selling circuit boards, or adding Google Adds. Does that make me a beggar? I can not afford to give away $50 USD each month for web space.
I have purchased 3 of the Tubecad simulators, and found that they work well. I personally think that his web site and the time that he invested in it was worth the money that I sent him. Some of his ideas may be different, but they make you think.
I have been funding my web site out of my own pocket for 3 years. I have come to the point where the material that I want to add to the web site will raise the cost, which I can recover by selling circuit boards, or adding Google Adds. Does that make me a beggar? I can not afford to give away $50 USD each month for web space.
It is funny to see how some people talk about themselves without even being aware of it. Your begging for some attention for a long time in this forum. Well the fact is your RH amps don't get the attention you would like to and then you go mad and attack other people's work, other people's opinions.
I'm fed up of your ridiculous ideas, what's a name anyway? Is Alvaro(my real name) more revealing to you than Stalker?
Broskie's own stuff is to be a very talented guy, you are not on the same level.
Uh Oh, it is starting again.
Every one is free to experiment in their own way. If we didn't we would all be building the same amps. The RH feedback concept does work, but it is one of many possible ways to connect local feedback around an output stage. I believe it was mentioned in an Audio Xpress magazine article recently.
I think we need to agree to dissagree and stop dissing each other, before this whole thing starts looking like the audio assylum stuff.
This started up with mention of the Broskie auto bias circuit. I tried it a couple of years ago, I didn't like it, I took it apart. No need for dissing the guy, because one of his next ideas might be a winner. If we collectively pi** him off and he stops writing, then we all lose some potential good ideas.
Back to the original topic, The JJ and Svetlana EL-34's arrived yesterday. My workload will probably keep me from experimenting soon, but the results will posted when they are done.
Every one is free to experiment in their own way. If we didn't we would all be building the same amps. The RH feedback concept does work, but it is one of many possible ways to connect local feedback around an output stage. I believe it was mentioned in an Audio Xpress magazine article recently.
I think we need to agree to dissagree and stop dissing each other, before this whole thing starts looking like the audio assylum stuff.
This started up with mention of the Broskie auto bias circuit. I tried it a couple of years ago, I didn't like it, I took it apart. No need for dissing the guy, because one of his next ideas might be a winner. If we collectively pi** him off and he stops writing, then we all lose some potential good ideas.
Back to the original topic, The JJ and Svetlana EL-34's arrived yesterday. My workload will probably keep me from experimenting soon, but the results will posted when they are done.
Hi tubelab,
I think your statement holds true for anyone. Besides, if you actually put stuff together and play with it, that affords a person more respect in my book than one who doesn't. Even if the results differ from someone else's.
I am looking forward to what you come up with. How's the cleanup going?
-Chris
I think your statement holds true for anyone. Besides, if you actually put stuff together and play with it, that affords a person more respect in my book than one who doesn't. Even if the results differ from someone else's.
I am looking forward to what you come up with. How's the cleanup going?
-Chris
Most of the storm related mess has been cleaned up. I am still waiting for shingles to fix the roof, but they are scarce right now. We lost a week of work which must be made up before the end of the year, which limits my play time.
I found a Japanese 6CA7 in my junk box. I didn't mind torturing this one so I subjected it to some severe testing last weekend. The curves looked similar to the Mullard that I tested earlier. I also noticed that the plate would begin to glow at about 30 watts. The plate in this one was bigger than the Mullard.
I experimented with connecting all three grids together, and plotting curves from zero bias to +14 volts in two volt steps. The curves looked very pentode like but the Mu was over 100. Unfortunately the linearity was poor.
I found a Japanese 6CA7 in my junk box. I didn't mind torturing this one so I subjected it to some severe testing last weekend. The curves looked similar to the Mullard that I tested earlier. I also noticed that the plate would begin to glow at about 30 watts. The plate in this one was bigger than the Mullard.
I experimented with connecting all three grids together, and plotting curves from zero bias to +14 volts in two volt steps. The curves looked very pentode like but the Mu was over 100. Unfortunately the linearity was poor.
Winged C Svets vs JJs
Tubelab and others,
I was browsing my VDV70/100 Amp work book last night in search of inspiration for a redesign (currently its PPP EL34 triode mode with ECC99 Comon Cathode/Concertina - that is just the original Menno circuit but with ECC99 in place of the 12AU7). My output impedance measurements from 6 months back show that the "Winged C" Svetlana gave significantly lower output impedance than the JJ Electronics EL34 at the same bias current. A bit strange since on purely sonic characteristics into my nominally 6 Ohm VAF DCX speakers I thought that the JJs sounded marginally better. I'm going to repeat these tests to confirm these results.
In both cases however the Output Impedance with zero global feedback is too high. I did run Sovtek 6550 in place of the EL34 as a trial and that gave much better Zout with decent sound BUT the limited separation of the output tubes (dictated by the PCB) and a tight mechanical construction (VDV2100/PAT4006 output tranny too close to the output tubes) gave me heat management problems with the side of the output tranny closest to the output tubes reaching 80 degrees C compared to 60 degrees C when using the EL34s - needless to say I'm back with the EL34s.
Cheers,
Ian
Tubelab and others,
I was browsing my VDV70/100 Amp work book last night in search of inspiration for a redesign (currently its PPP EL34 triode mode with ECC99 Comon Cathode/Concertina - that is just the original Menno circuit but with ECC99 in place of the 12AU7). My output impedance measurements from 6 months back show that the "Winged C" Svetlana gave significantly lower output impedance than the JJ Electronics EL34 at the same bias current. A bit strange since on purely sonic characteristics into my nominally 6 Ohm VAF DCX speakers I thought that the JJs sounded marginally better. I'm going to repeat these tests to confirm these results.
In both cases however the Output Impedance with zero global feedback is too high. I did run Sovtek 6550 in place of the EL34 as a trial and that gave much better Zout with decent sound BUT the limited separation of the output tubes (dictated by the PCB) and a tight mechanical construction (VDV2100/PAT4006 output tranny too close to the output tubes) gave me heat management problems with the side of the output tranny closest to the output tubes reaching 80 degrees C compared to 60 degrees C when using the EL34s - needless to say I'm back with the EL34s.
Cheers,
Ian
Hey guys sorry to bump a mega old thread- but I was curious of people's opinions a decade later.
I have to admit I'm a complete circuit noob, but to me it makes the most sense to tie G1, G2, and G3 together as a "super grid".
Otherwise a symmetrical arrangement of tying G1 to G2, then tying G3 to the Anode.
I have to admit I'm a complete circuit noob, but to me it makes the most sense to tie G1, G2, and G3 together as a "super grid".
Otherwise a symmetrical arrangement of tying G1 to G2, then tying G3 to the Anode.
I'm sorry can you explain further? Again I'm a complete noob at this, but I don't see how using the g1,2,3 of the EL34 as a large "single grid" would be any different than the normal control grid in a real Triode. They aren't connected to the cathode, so shouldn't the voltage swing of previous gain stages just make it work like a true Triode?
There is a difference between a large "super grid" made from connecting three grids together, and a single grid triode.
In a "normal" triode there is one grid, usually evenly wound and spaced rather close to the cathode. There are triodes made with a variable pitch created for the purpose of creating a variable gain amp, but these are not often used for audio.
Within those constraints two entirely different tubes could be made just by varying the pitch of the grid wire winding. Assume a cathode creating a "cloud" of free electrons around itself, with most of them attracted toward a plate with some positive charge applied to it. With nothing between the cathode and plate, most of the electrons emitted by the cathode will eventually reach the plate....."unlike charges attract." The negatively charged electrons will be attracted towards the positively charged plate.
Add something like a coil of wire (the grid) between the cathode and plate. If a large negative voltage is applied to this grid, many of the electrons emitted by the cathode would be repelled back toward the cathode since the grid has a larger negative charge that the cathode, and the electrons it emits. "like charges repel" The cloud, or space charge will be compressed toward the cathode, and shrinks.
If a positive charge is applied to the grid, the electrons from the cathode will be attracted towards this grid, and a few will strike it, but most will continue toward the plate with a larger positive charge.
If the grid has few turns of wire with a lot of empty space between the turns, many electrons could pass through it relatively easily, so a large negative voltage would be needed to cut the tube current completely off. Large amounts of signal voltage would be required on this grid to get a reasonable change in plate current. This would be a tube with low Mu, but if well constructed it could have good linearity since few electrons would actually collide with this grid since it was mostly air.
If you took the same parts, but built a tube with many turns of wire, closely spaced there would be less opportunity for electrons to flow unimpeded to the plate since there are more grid wires in the path and the area between them is small. This would be a medium Mu tube.
If the turns of grid wire were space very tightly few electrons would get through to the plate, and only a small negative voltage could create an impenetrable wall for the electrons, such that no current flows to the plate. This would be a high Mu triode.
Indeed there are several tube types where the only change is the pitch of the grid wires. The 12AU7, and 12AX7 are similarly constructed (given two tubes from the same vendor and dates) except for the grid pitch.
Taking a pentode like the EL34 and tying all three grids together creates a tube with 3 grids, each of different pitch and spacing from the cathode. Even with zero voltage (same as the cathode) on the grids, an electron will have a tortuous path from the cathode to the plate. This would be a high MU tube, and it would require near zero voltage to cut the tube off, and likely some positive voltage on the grids to get things moving. There are many more variables than just the grid pitch at work here, so the "positive voltage needed" generalization may not always hold true. I know of one tube that has 5 grids, and tying all of them together into one "super grid" does indeed make a nice triode.....the 6BE6.
In a "normal" triode there is one grid, usually evenly wound and spaced rather close to the cathode. There are triodes made with a variable pitch created for the purpose of creating a variable gain amp, but these are not often used for audio.
Within those constraints two entirely different tubes could be made just by varying the pitch of the grid wire winding. Assume a cathode creating a "cloud" of free electrons around itself, with most of them attracted toward a plate with some positive charge applied to it. With nothing between the cathode and plate, most of the electrons emitted by the cathode will eventually reach the plate....."unlike charges attract." The negatively charged electrons will be attracted towards the positively charged plate.
Add something like a coil of wire (the grid) between the cathode and plate. If a large negative voltage is applied to this grid, many of the electrons emitted by the cathode would be repelled back toward the cathode since the grid has a larger negative charge that the cathode, and the electrons it emits. "like charges repel" The cloud, or space charge will be compressed toward the cathode, and shrinks.
If a positive charge is applied to the grid, the electrons from the cathode will be attracted towards this grid, and a few will strike it, but most will continue toward the plate with a larger positive charge.
If the grid has few turns of wire with a lot of empty space between the turns, many electrons could pass through it relatively easily, so a large negative voltage would be needed to cut the tube current completely off. Large amounts of signal voltage would be required on this grid to get a reasonable change in plate current. This would be a tube with low Mu, but if well constructed it could have good linearity since few electrons would actually collide with this grid since it was mostly air.
If you took the same parts, but built a tube with many turns of wire, closely spaced there would be less opportunity for electrons to flow unimpeded to the plate since there are more grid wires in the path and the area between them is small. This would be a medium Mu tube.
If the turns of grid wire were space very tightly few electrons would get through to the plate, and only a small negative voltage could create an impenetrable wall for the electrons, such that no current flows to the plate. This would be a high Mu triode.
Indeed there are several tube types where the only change is the pitch of the grid wires. The 12AU7, and 12AX7 are similarly constructed (given two tubes from the same vendor and dates) except for the grid pitch.
Taking a pentode like the EL34 and tying all three grids together creates a tube with 3 grids, each of different pitch and spacing from the cathode. Even with zero voltage (same as the cathode) on the grids, an electron will have a tortuous path from the cathode to the plate. This would be a high MU tube, and it would require near zero voltage to cut the tube off, and likely some positive voltage on the grids to get things moving. There are many more variables than just the grid pitch at work here, so the "positive voltage needed" generalization may not always hold true. I know of one tube that has 5 grids, and tying all of them together into one "super grid" does indeed make a nice triode.....the 6BE6.
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