Tim,
What is the purpose of the 3.3meg resistor between the anode and grid of the 5814? With the tone control network do you need the .22 mfd cap between the network and the ground? On a matter of personal taste, I'd find the caps in the network not giving enough variation - I'd prefer a larger cap in the bottom part of the bass pot set up and the same for the treble pot.
Best wishes with the construction.
What is the purpose of the 3.3meg resistor between the anode and grid of the 5814? With the tone control network do you need the .22 mfd cap between the network and the ground? On a matter of personal taste, I'd find the caps in the network not giving enough variation - I'd prefer a larger cap in the bottom part of the bass pot set up and the same for the treble pot.
Best wishes with the construction.
I think the 3,3Meg resistor is used for biasing the 5814. The cathode resistor is large valued(22k), I don't know the quiescent current through this tube, but I think the current will give a voltage drop over the cathode resistor which is greater than the needed biasvoltage.
So the 3,3Meg and 1Meg resistors is used as a voltage divider to raise the grid voltage for proper biasing.
So the 3,3Meg and 1Meg resistors is used as a voltage divider to raise the grid voltage for proper biasing.
Yes,
The 3.3meg will affect the bias, but I was wondering if it was necessary in a cathode follower stage - I've never used a resistor in that position when I've used a cathode follower, and I cannot recall seeing a circuit using one. It may well be necessary (I haven't worked out the bias position of the cathode follower), I'm just curious about it!
The 3.3meg will affect the bias, but I was wondering if it was necessary in a cathode follower stage - I've never used a resistor in that position when I've used a cathode follower, and I cannot recall seeing a circuit using one. It may well be necessary (I haven't worked out the bias position of the cathode follower), I'm just curious about it!
Lesse..
12AX7 - not really needed.. could probably drop down to an 'AU or 'AT7 instead..
I figure around 2mA bias minimum in the CF (yes the 3.3M biases it at ~40Vk, and also loads down the tone circuit a little). 12AU7 really starts working at 5mA, so why not make a CF that works well too?
I could just as well use self-bias in the cathode, but this will fix it at a much more stable point.
The .22uF fixes the ground return for the tone controls. I could just as well short it, and place a cap in series with the output (going to the 5814 grid; come to think of it, it could be a smaller cap and still work, hmm!).
I'll see what Duncanamp's TSC says about the larger caps...
Edit:
Didn't see your post, Tube Dude..
I sure could omit the first coupling cap, and only use one to fix the tone circuit's AC ground (as shown). But it's probably best this way anyway, after all if a strong DC signal is applied to the input, it would shift the operating point of the entire setup. Only two stages, not much to worry about, but meh.
Tim
12AX7 - not really needed.. could probably drop down to an 'AU or 'AT7 instead..
I figure around 2mA bias minimum in the CF (yes the 3.3M biases it at ~40Vk, and also loads down the tone circuit a little). 12AU7 really starts working at 5mA, so why not make a CF that works well too?
I could just as well use self-bias in the cathode, but this will fix it at a much more stable point.
The .22uF fixes the ground return for the tone controls. I could just as well short it, and place a cap in series with the output (going to the 5814 grid; come to think of it, it could be a smaller cap and still work, hmm!).
I'll see what Duncanamp's TSC says about the larger caps...
Edit:
Didn't see your post, Tube Dude..
I sure could omit the first coupling cap, and only use one to fix the tone circuit's AC ground (as shown). But it's probably best this way anyway, after all if a strong DC signal is applied to the input, it would shift the operating point of the entire setup. Only two stages, not much to worry about, but meh.
Tim
He could choose to apply the cathode resistor to a negative voltage instead of ground, then the voltage divider would be unnecessary.
I think it's a bit tricky to dc connect the cathode stage when it's a tone control in front of it.
As I have said before, I dont know the quiescent current through this tube but I can try to make some assumptions.
The voltage divider will raise the grid voltage to about 46V, if say that the biasing voltage should be about 5-7V the current through the cathode resistor will be about 2,3-2,5 mA and this will also be the quiescent current(am I correct?).
I think this maybe a bit low for this tube, I'm not very sure.. I leave it to some of the experts to decide, I'm just a newbie in this game.
Tube_Dude said:
I think it's a bit tricky to dc connect the cathode stage when it's a tone control in front of it.
As I have said before, I dont know the quiescent current through this tube but I can try to make some assumptions.
The voltage divider will raise the grid voltage to about 46V, if say that the biasing voltage should be about 5-7V the current through the cathode resistor will be about 2,3-2,5 mA and this will also be the quiescent current(am I correct?).
I think this maybe a bit low for this tube, I'm not very sure.. I leave it to some of the experts to decide, I'm just a newbie in this game.
LOL!.. A negative voltage supply would add five, maybe ten components in exchange for a few more volts of performance, and just to get rid of one resistor to +V.
Sorry, but it is funny
Yes, around 2-3mA is what I'm going for, more or less.. it should be okay, since 22k is a good load for it, though pretty close to the Rp at this current level. Won't matter much if you ask me, since it won't be going over 10V anyway.
TSC shows that the larger bottom caps gives more even boost vs. cut, thanks for that suggestion. (Using 2.2nF for lower bass cap, 470pF for lower tone cap.)
Tim
Sorry, but it is funny
Yes, around 2-3mA is what I'm going for, more or less.. it should be okay, since 22k is a good load for it, though pretty close to the Rp at this current level. Won't matter much if you ask me, since it won't be going over 10V anyway.
TSC shows that the larger bottom caps gives more even boost vs. cut, thanks for that suggestion. (Using 2.2nF for lower bass cap, 470pF for lower tone cap.)
Tim
what is the purpose of the three inputs with the 3-ganged pot and the parallel outputs??
this is a question about topologies for ya'll tube experts:
I was just recently reading some tube articles... what is the general wisdom about a circuit called 'totem pole'?? The author was swearing by them, but you know about authors...
this is a question about topologies for ya'll tube experts:
I was just recently reading some tube articles... what is the general wisdom about a circuit called 'totem pole'?? The author was swearing by them, but you know about authors...
Sch3mat1c said:LOL!.. A negative voltage supply would add five, maybe ten components in exchange for a few more volts of performance, and just to get rid of one resistor to +V.
Sorry, but it is funny
Yes, you are right, a negative supply would increase the number of components. But I just said it was a another way you could do it, and it was not meant as a reply to you, it was not meant as an advice to you either. It was actually meant for bournville.
And please don't make fun of me, as you probably have recognized I'm just a newbie, and I try to learn, and I do a lot of mistakes.
But I'm only 21, and I didn't grow up with vacuum tubes. None of the members of my family works with electronics either, so I didn't grow up with a "DIY electronics father" or something like that.
My interest for vacuum tubes started about 3 years ago, and almost everything I know about tubes I have learned by my self by reading books, searching the Internet and so on.
And I have only constructed and build one tube amp so far, indeed I'm currently working with my second tubeamp these days.
So please show some goodwill, and try to learn me some about tubes instead.
Back to your design...wouldn't a quiescent current of 2-3mA be a bit low for a driver stage?
I have learned that ECC83 will not work satisfactory because of the low driver ability of this tube, instead I have learned that a cathode stage should use tubes with larger platecurrents giving them a better ability to drive difficult loads.
Well, I don't know, Sch3mat1c. I've liked your ideas in the past, but this one seems a bit citrus.
So you want tone controls to deal with your loudspeakers? Once adjusted, they will be left at that optimal setting? Why not dragoon someone with a loudspeaker measurement system into helping you to sort out the loudspeakers' anechoic response, then tweak room positioning until it sounds nice?
I do, however, agree that passive tone controls are less worse than active.
Your balance control will theoretically introduce crosstalk due to wiper/track resistance. This probably isn't a practical problem.
Why are you apparently mixing all your inputs together? It's hard eliminating crosstalk between sources, yet you are doing it on purpose.
I want to be quite clear about this. I have no intention of upsetting anyone. These are my thoughts, and they are guaranteed malevolence-free, caffeine-free etc.
So you want tone controls to deal with your loudspeakers? Once adjusted, they will be left at that optimal setting? Why not dragoon someone with a loudspeaker measurement system into helping you to sort out the loudspeakers' anechoic response, then tweak room positioning until it sounds nice?
I do, however, agree that passive tone controls are less worse than active.
Your balance control will theoretically introduce crosstalk due to wiper/track resistance. This probably isn't a practical problem.
Why are you apparently mixing all your inputs together? It's hard eliminating crosstalk between sources, yet you are doing it on purpose.
I want to be quite clear about this. I have no intention of upsetting anyone. These are my thoughts, and they are guaranteed malevolence-free, caffeine-free etc.
Ah, that's where the White comes from in the WCF!
Back on topic..
It's OK Gunderz, I understand. Like saying "use windows, not linux"? It runs the computer, but one's less convienient... Meh, bad analogy (depending on how computer-savvy you are ).
I don't see why passive is worse than active...I only took passive because I'm not sure how I'd implement active.
The three mixed inputs are for my general audio purposes: radio, computer and aux. I use the radio optionally - right now I have a similar setup with my stereo 6V6 SE, computer on all the time, set to normal listening level so I can hear what's going on (Trillian, Windows alerts, etc.). If I want to listen to the radio, I turn up that input. Since the computer is still being mixed in, I can hear alerts. I cannot switch between inputs because this would cut out the computer altogether.
The tone controls are just to make it sound better...so what if my room and/or speakers aren't flat.. I got 'em from the trash pile, and even as-is sound just great.
Dunno what you mean by citrus...oranges are sweet, but you're hard-pressed to find someone who thinks lemons and limes are sweet, so I don't know what is meant with that word.
I'll mostly leave them alone, but right now I find I need a little more tone when listening to MP3s, so it'll move a little.
I don't see any harm from crosstalk, either between channels or inputs. The inputs are isolated by 200k (if each is in series), and each itself is shunted by 100k, so the actual crosstalk is like 1/4 or something. A high ohmic level in any case, certainly not enough to worry about.
I don't see any reason to fear stereo crosstalk...opinions?
Tim (stop replying so fast, I have to post these big messages to keep up! )
Back on topic..
It's OK Gunderz, I understand. Like saying "use windows, not linux"?
It runs the computer, but one's less convienient... Meh, bad analogy (depending on how computer-savvy you are ).I don't see why passive is worse than active...I only took passive because I'm not sure how I'd implement active.
The three mixed inputs are for my general audio purposes: radio, computer and aux. I use the radio optionally - right now I have a similar setup with my stereo 6V6 SE, computer on all the time, set to normal listening level so I can hear what's going on (Trillian, Windows alerts, etc.). If I want to listen to the radio, I turn up that input. Since the computer is still being mixed in, I can hear alerts. I cannot switch between inputs because this would cut out the computer altogether.
The tone controls are just to make it sound better...so what if my room and/or speakers aren't flat.. I got 'em from the trash pile, and even as-is sound just great.
Dunno what you mean by citrus...oranges are sweet, but you're hard-pressed to find someone who thinks lemons and limes are sweet, so I don't know what is meant with that word.
I'll mostly leave them alone, but right now I find I need a little more tone when listening to MP3s, so it'll move a little.
I don't see any harm from crosstalk, either between channels or inputs. The inputs are isolated by 200k (if each is in series), and each itself is shunted by 100k, so the actual crosstalk is like 1/4 or something. A high ohmic level in any case, certainly not enough to worry about.
I don't see any reason to fear stereo crosstalk...opinions?
Tim (stop replying so fast, I have to post these big messages to keep up!
)- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.