Mark A. Gulbrandsen said:
Mark,
I believe you started with a matched quad.
http://www.diyaudio.com/forums/showthread.php?postid=923330#post923330
Do they drift with use? What is the difference (in volts) that you measured?
grimberg said:
they weren't matched fer sure , they just are the same ......and anybody who will say that to you is sorta liar.......just rethink-how big is possibility to match two gass toobz in entire working region?
but -if they are in ballpark of 3 to 5 volts at needed current ,that is more than good .
anyway ,there are used here for plate voltage reg,where difference of 10 volts is hardly hearable
Choky,
That's what I understood from the data sheet, where the regulation is stated to be within 2V to 4V, depending on the current. What I don't know is how widely the operation point varies in any random lot of 0D3s. Mark's statement surprised me because I expected the operating point differences to be small.
That's what I understood from the data sheet, where the regulation is stated to be within 2V to 4V, depending on the current. What I don't know is how widely the operation point varies in any random lot of 0D3s. Mark's statement surprised me because I expected the operating point differences to be small.
I think 10% is about as close as you're going to find 0D3's and I read in its specs somewhere the stated tolerance but I can't remember which manufacturers specs that was. 10% is how my quad was when I measured them. Mt statement above reflects how a pass transistor can multiply the value of a capacitor. The 0D3's are not going to do that so starting with very clean DC is paramount!!
Mark
Mark
don't bother with this - they're good or they're brokengrimberg said:
just put them in right current spot and enjoy
sometimes too much thinking is waste.....tnx to Greats from past , some good things are already invented........and proved
there is no need for some "better" solution than gas toob for plates,at least in this example
at least I didn't hear better solution in my tests
and- will anybody choose SS or tube stab HERE,that is theirs decision and way of thinking,but nobody can persuade me that any other stab is better than plain vanilla shunt toob
tip:
think in dynamic outlines (terms),not static
Mark A. Gulbrandsen said:
pass xsistor and gas toob aren't in same world of intentions;
one is series
other is parallel
on the end ,just result is important and that is reflected from dynamical characteristics of each reg.
to paraphrase old books-best interaction between source and load is when their (respective) U-I characteristics are intersected at 90 degs
some food for thought
anyway....every approach need different conditions
gas toob needs somewhat cleaner preceding voltage, but series reg (and I mean every series reg ) need somewhat lazier load
what is just difference and what is virtue,who knows
and- on the end just your ears can decide
tip:
when you gonna shave 100V of initial voltage,how much clean voltage you need on start?
you can start with sissy doubler ,if you want
Zen Mod,
Do you mean that to say that clean voltage is not as important because of the amount of voltage dropped by the gas tube reg?
Do you mean that to say that clean voltage is not as important because of the amount of voltage dropped by the gas tube reg?
Hi,
Most unused NOS gas discharge valves were pretty good if kept within a reasonable working area.
Problem is, I think, that most of what you find on the market nowadays is either used or somewhat flaky.
If you'd have a box of 50 truly unused OA2s for instance, matching wouldn't be a big deal as most were usually pretty much spot on anyway.
All in all and within the context of your design you'd be much better off with a cleaner supply than with a minor variation in voltage although I do like to keep the two stereo channel as identical as possible as I hate channel imbalance.
Cheers fellas, 😉
Most unused NOS gas discharge valves were pretty good if kept within a reasonable working area.
Problem is, I think, that most of what you find on the market nowadays is either used or somewhat flaky.
If you'd have a box of 50 truly unused OA2s for instance, matching wouldn't be a big deal as most were usually pretty much spot on anyway.
All in all and within the context of your design you'd be much better off with a cleaner supply than with a minor variation in voltage although I do like to keep the two stereo channel as identical as possible as I hate channel imbalance.
Cheers fellas, 😉
Zen Mod said:
Hi, I received the Edcor XPWR022 300V/150mA (NOT center tapped!) plus 15V/1A transformer today (Thanx Lyndon!) My question is; if there is no center tap on the this Edcor secondary how does one connect the return ground? I see how it is connected in bridge mode but was interested in trying the 2-Schottky diode full wave suggestion by Zen Mod.
Could someone explain the obvious and I’m sure simple explanation to me??
The link shows different illustrations of full wave and bridge but all show a ground connect via either secondary CT (for full wave)or bridge rectifier.
http://www.hammondmfg.com/pdf/5c007.pdf
Stan
Without CT make it 4 Schottky diode full wave bridge. Following the diagrams you provided, connect the rectified lead marked (-) to chassis.
few questions
one for Lucky : what happens with your Edcor xformer and preamp ...overall ?
to Mark: did you make comparison between toob shunt reg and sand one?
one for Lucky : what happens with your Edcor xformer and preamp ...overall ?
to Mark: did you make comparison between toob shunt reg and sand one?
Gridstoppers with 12B4
Here's a question for you 12B4 line stage experts. Actually, a couple questions.
1. Are you using two gridstopper resistors, one to each grid connection (Pins 2 and 7)? Or are you using just one resistor connected to just one pin? If just one resistor, do you leave the other grid pin unconnected, or jumpered to the other grid pin?
2. In my 12B4 linestage, I have a 100K volume control feeding the tube. If I omit the gridstopper entirely, and just wire the wiper directly to both grid pins, there is no RFI, oscillation or other nasties, which would seem to indicate the gridstopper is not needed. However, if I turn the volume control down all the way, effectively shorting the grid to ground, there is a horrendous noise. Using a 100R gridstopper cures the noise at zero volume, but the sound quality suffers, and I've tried a number of different types of resistors. So what's going one here? What causes this noise when the grid is shorted to ground, and is there any way around this other than using the gridstopper?
FYI, I'm using a simple (temporarily) audio circuit----8.2K plate resistor, 500R cathode resistor unbypassed---255 V. B+ and 21ma. The B+ is regulated by dual mono VR tubes fed by a CCS network. It sounds very good, but a lot better without the gridstopper.
Thanks for any comments/advice.
Dave
Here's a question for you 12B4 line stage experts. Actually, a couple questions.
1. Are you using two gridstopper resistors, one to each grid connection (Pins 2 and 7)? Or are you using just one resistor connected to just one pin? If just one resistor, do you leave the other grid pin unconnected, or jumpered to the other grid pin?
2. In my 12B4 linestage, I have a 100K volume control feeding the tube. If I omit the gridstopper entirely, and just wire the wiper directly to both grid pins, there is no RFI, oscillation or other nasties, which would seem to indicate the gridstopper is not needed. However, if I turn the volume control down all the way, effectively shorting the grid to ground, there is a horrendous noise. Using a 100R gridstopper cures the noise at zero volume, but the sound quality suffers, and I've tried a number of different types of resistors. So what's going one here? What causes this noise when the grid is shorted to ground, and is there any way around this other than using the gridstopper?
FYI, I'm using a simple (temporarily) audio circuit----8.2K plate resistor, 500R cathode resistor unbypassed---255 V. B+ and 21ma. The B+ is regulated by dual mono VR tubes fed by a CCS network. It sounds very good, but a lot better without the gridstopper.
Thanks for any comments/advice.
Dave
Hi Dave,
1. No I did not.
2. It did happen to me (noise on 0 volume) and I changed the ALPS Blue I'm using which cured the problem. My 12B4 'til now does not have grid stoppers and use ALPS Blue.
Disclaimer: Not an expert
1. No I did not.
2. It did happen to me (noise on 0 volume) and I changed the ALPS Blue I'm using which cured the problem. My 12B4 'til now does not have grid stoppers and use ALPS Blue.
Disclaimer: Not an expert
Salectric,
Those are interesting results. I haven’t needed a stopper in my 12B4 designs before either. I wonder if your pot has some open trace areas down near zero volume, and the grid, far from being grounded, is actually going momentarily open. That could make horrendous noises. Do you have a “safety” grid leak resistor from the grid/wiper to ground? I always use one and recommend it to others. Try putting a 1 Meg MF or greater to ground. The data sheet lets you go as high as 2.2 Meg when the tube is cathode biased as it is here. It will only slightly change the volume pot taper. That would be easy to try to see if it helps.
If that doesn’t help, then you may indeed need a stopper. I’m a bit surprised that 100 ohms is so audibly inferior than using nothing, but I accept your opinion. I might be tempted to slip on a ferrite bead near the grid pin instead in that case. The best solution would be to re-evaluate your layout, but that may be an upheaval. Are all connections relatively short and tight to the tube? Do you have any extra stray capacitances to ground? I firmly believe that people would need fewer and/or smaller grid stoppers (on any tube) if they adhered to basic RF wiring principles.
Finally, although you didn’t ask: You’ve kept your cathode unbypassed. Understandably, you probably wanted to avoid the sound of a big bypass cap (or caps). I have found that a bypassed 12B4 stage can sound great, but you’ll have to fiddle with bypass cap combinations a bit. The benefit is that your output resistance would then drop from about 3100 ohms to near 1000 ohms. That often helps with sound character, depending on the cable driven and the load on the far end. Gain would pop up from about 7.8 dB to about 15 dB, which may or may not be useful to you. If your present gain and higher output resistance suit your present application, then there is nothing wrong with the unbypassed cathode either.
EDIT: To add an answer to your question about wiring the two grid pins. Out of habit, I always wire all pins on any tube with multiple grid or cathode leads to reduce inductance. This may be totally unnecessary in most audio applications, but why not do it anyway since it adds little or no cost? If you do add a stopper, try a 200 ohm resistor in each grid lead with the input ends tied together. That gives you 100 ohms with lowered inductance.
Those are interesting results. I haven’t needed a stopper in my 12B4 designs before either. I wonder if your pot has some open trace areas down near zero volume, and the grid, far from being grounded, is actually going momentarily open. That could make horrendous noises. Do you have a “safety” grid leak resistor from the grid/wiper to ground? I always use one and recommend it to others. Try putting a 1 Meg MF or greater to ground. The data sheet lets you go as high as 2.2 Meg when the tube is cathode biased as it is here. It will only slightly change the volume pot taper. That would be easy to try to see if it helps.
If that doesn’t help, then you may indeed need a stopper. I’m a bit surprised that 100 ohms is so audibly inferior than using nothing, but I accept your opinion. I might be tempted to slip on a ferrite bead near the grid pin instead in that case. The best solution would be to re-evaluate your layout, but that may be an upheaval. Are all connections relatively short and tight to the tube? Do you have any extra stray capacitances to ground? I firmly believe that people would need fewer and/or smaller grid stoppers (on any tube) if they adhered to basic RF wiring principles.
Finally, although you didn’t ask: You’ve kept your cathode unbypassed. Understandably, you probably wanted to avoid the sound of a big bypass cap (or caps). I have found that a bypassed 12B4 stage can sound great, but you’ll have to fiddle with bypass cap combinations a bit. The benefit is that your output resistance would then drop from about 3100 ohms to near 1000 ohms. That often helps with sound character, depending on the cable driven and the load on the far end. Gain would pop up from about 7.8 dB to about 15 dB, which may or may not be useful to you. If your present gain and higher output resistance suit your present application, then there is nothing wrong with the unbypassed cathode either.
EDIT: To add an answer to your question about wiring the two grid pins. Out of habit, I always wire all pins on any tube with multiple grid or cathode leads to reduce inductance. This may be totally unnecessary in most audio applications, but why not do it anyway since it adds little or no cost? If you do add a stopper, try a 200 ohm resistor in each grid lead with the input ends tied together. That gives you 100 ohms with lowered inductance.
Preamp Work in Utah...
Interesting information on that pot, Brian.
So it is SuperBowl day in the States, but I am heading up to Bountiful, Utah to visit Mark and to work on the 12b4. To answer your question, Choky, we don't know how the custom transformers and the gas shunt vs. solid state compare as Mark has devoted his time totally to the
Krell Klone II project. Now that he has mailed out the orders, we are going to fiddle. Wish I could whisk you and Brian out here. We could put Brian in either Mark's Tek scope display room, or his collection room of working antique tv's (tubes, Brian, tons of weird tubes!). And Choky could try to figure out Mark's messed up Aleph projects and wrestle with the too friendly labrador.
Arnold, you aren't a pro? I would think you are!
Ciao, for now...
Lucky Lyndy
Interesting information on that pot, Brian.
So it is SuperBowl day in the States, but I am heading up to Bountiful, Utah to visit Mark and to work on the 12b4. To answer your question, Choky, we don't know how the custom transformers and the gas shunt vs. solid state compare as Mark has devoted his time totally to the
Krell Klone II project. Now that he has mailed out the orders, we are going to fiddle. Wish I could whisk you and Brian out here. We could put Brian in either Mark's Tek scope display room, or his collection room of working antique tv's (tubes, Brian, tons of weird tubes!). And Choky could try to figure out Mark's messed up Aleph projects and wrestle with the too friendly labrador.
Arnold, you aren't a pro? I would think you are!
Ciao, for now...
Lucky Lyndy
Lucky,
Yes, I would love checking out Mark's Tek scope display room. What does he have there?
I've got my own Tek that needs attention today. I bought a used Tek 2430A DSO. I've replaced 7 known-bad parts in the switching supply so far and it still isn't switching yet... I'm thinking lightning surge.
Yes, I would love checking out Mark's Tek scope display room. What does he have there?
I've got my own Tek that needs attention today. I bought a used Tek 2430A DSO. I've replaced 7 known-bad parts in the switching supply so far and it still isn't switching yet... I'm thinking lightning surge.
Brian... Do you mean the scope was hit by lightning? Those switchers can be a pain to repair and sometimes the best way is to just get another parts scope. If it was hit by lightning I bet the damage is more than just the power supply. The vert. input devices may also be fried and there may be a short on another board causing the switcher to stay in shutdown. My 7904A scope uses a switching supply and it too was DOA but simple replacement of the 2 main filter caps got it going again. From my experience as a bench tech lightning damage is always more then just skin deep. I just took a quick look at your servcei manual and your scope has those custom hybrid IC's in it... try to stay away from those. Some of those IC's are impossible to find new today.... another scope is the only place to get em. All but one of my TEK scopes are discreet although some do have a few custom DIP IC's in places like the VERT front end and other locations. Sopme TEK labeled IC's are just selected off the shelf parts too.
Mark
Mark