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Old 19th December 2011, 01:53 AM   #1
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Default Using a single triode as a .......

common cathode driver / buffer placed after a transformer DAC I/V.

Plan is, is to use a single triode from a 6H30P as a simple common cathode driver/buffer to feed a preamp ( a Pete Millet based Lo Mu pre).
The idea is to keep it very simple; Use a CCS on the B+ and a 9v NiMH as the cathode bias, then just have a 4.7uf coupling capacitor on the output with a 470K R load.

Idealy, just want to use 1/2 of the 6H30P for each channel.

pros? cons?

As it is, I'd like to stay away from using the tube as a cathode follower.

JD
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Old 19th December 2011, 02:27 AM   #2
kevinkr is offline kevinkr  United States
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My experience with battery bias has been that nimh are markedly inferior sounding to nicads (internal impedance is higher, and there are some other issues depending on battery that result in poorer measured linearity), and I have switched entirely to grid bias in so far as battery bias is concerned - less convenient in most cases but since you are using a transformer for I/V conversion just connect the negative terminal of a conventional (not rechargeable) 9V battery to the secondary of your I/V transformer. Bypass the battery with a decent electrolytic and you are done.

YMMV...
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Old 19th December 2011, 02:54 AM   #3
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I'd like to keep this thread directed to the question of the triode.

Thanks for the suggestion re: battery bias, but that is information / assistance that I am not requiring.

Jeff

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My experience with battery bias has been that nimh are markedly inferior sounding to nicads (internal impedance is higher, and there are some other issues depending on battery that result in poorer measured linearity), and I have switched entirely to grid bias in so far as battery bias is concerned - less convenient in most cases but since you are using a transformer for I/V conversion just connect the negative terminal of a conventional (not rechargeable) 9V battery to the secondary of your I/V transformer. Bypass the battery with a decent electrolytic and you are done.

YMMV...
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Old 19th December 2011, 03:13 AM   #4
kevinkr is offline kevinkr  United States
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OK.. Why ask here if you are uninterested in comments related to your proposed topology?

So what exactly is there to discuss?
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Old 19th December 2011, 04:14 AM   #5
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The question asked about the usage of the triode. Since it is a DIY Tube forum, I thought this would be the best place to ask specifically of that circuit element, which is what I believe I did. The "other stuff" I mentioned, does not relate directly to the question, just periferal, non esential to my question, information.
I would appreciate answers regarding the tirode usage as asked, and not comments about the non-essentials, as they do not effect the "use" of the circuit element in the manner that I asked the question.

If I changed the battery as suggested or looked at different loading, comments on the "other parts" etc... my question would still remain unanswered regarding the usage of a single triode in a common cathode output circuit, therefore your first reply does not address the issue I desire information / experience/ and yes, comments.

JD

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OK.. Why ask here if you are uninterested in comments related to your proposed topology?

So what exactly is there to discuss?

Last edited by Jeffrey Davison; 19th December 2011 at 04:21 AM.
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Old 19th December 2011, 04:30 AM   #6
kevinkr is offline kevinkr  United States
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I don't see how biasing the triode is not in some way related to your question, however if you feel it is not, then I assume that the only question you are asking is whether or not this triode should be used as a common cathode stage (anode follower) or a cathode follower in which case you need to provide some additional information which would include at a minimum the expected voltage at the output of your I/V transformer, and the required drive voltage of whatever else it is driving. Provide some additional information and it is likely that you will get some good answers.

Frankly it would seem simple enough to try it both ways and decide for yourself based on the gain structure of the rest of your system. A single triode with the proper I/V transformer should provide more than sufficient gain and adequate drive if the rp is low enough to drive whatever follows. You did not frame your question well - it was not clear to me what you were asking, and I thought I had something useful to contribute.

Don't expect people here to adhere all that closely to your guidelines unless you would prefer that no one respond at all. It is likely that your responses to my comments have already scared off a few potentially helpful participants.

I was attempting to be helpful when I posted my original comments so on that note will I end.
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Old 19th December 2011, 04:40 AM   #7
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Jeffery, you asked for pros and cons. And that is exactly what Kevin gave you. Information that directly relates to your circuit proposal. Kevin won't say this because he's probably too much of a gentleman, but you come off like a snob. And I learned something new tonight. When designing with a 6H30, bias is a non-essential.
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Old 19th December 2011, 05:21 AM   #8
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maybe I should just rephrase the initial question.....

what are the pros and cons of using a single triode in a common cathode circuit as an output/buffer/driver stage?

Din't mean at all to sound snobish, just trying to see if a common cathode singal triode would work well enough. What is good and what is bad, in light of using 1/2 of a 6H30P.

That's all the information that I'd like to know at the moment. IF I decide to use it, then I would ask for comments on the "support" components to make it work the best.

sorry for any confusion.

JD
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Old 19th December 2011, 05:49 AM   #9
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common cathode take something like a E90CC E92CC differend gain levels . its a cheap tube
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Old 19th December 2011, 07:54 AM   #10
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Are you asking if using one section of a double triode is better than using the two sections in parallel? Sure it will work. I've never used that tube, but supposedly it is a good tube for that purpose. However, I'd just use the transformer as output device directly. Assuming (oops, I am diverting the subject too) you have a current out DAC into a low ohmage resistor then into the transformer, you'll have a good low impedance drive for the cable and preamp. The only reason to build a tube stage after the tranny is more gain. I use my CDP with only a 50ohm resistor as the I/V converter into a Lundahl 1:1 transformer. The signal level is about the same as my phone pre, so relative to my DVD player, I turn the volume down a tad when watching movies. Oops...sorry, didn't answer your question.
The pros of using a single triode vs many in parallel is simplisity. The single triode section can probably run hotter than when using both b/c of heat from the neighboring triode isn't an issue. This may potentially be good? Cons is higher impedance, but is it high enough to matter, think not. Sorry man, I'm not helping. At least I can give my vote to running transformer direct, no gain stage at all.
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