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Old 4th June 2008, 02:19 PM   #51
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Default Re: #39

Quote:
Originally posted by oldeurope


Hi SY,
I agree, thanks.
Please find a name for this factor.
This factor tells you e.g. if a cathode bypass makes sense or not.
Since I don't like an (electrolytic) bypass cap and its “ESR” influence
this factor is a good tool in triode circuit design.
There are lots of additional aspects the factor helps for.

Kind regards,
Darius
Hi, excuse me for butting in, but if the factor is, as it looks to be, the ratio of load impedance to effective source impedance, then would the term "Damping Factor" be appropriate?

Cheers,

Michael
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Old 4th June 2008, 02:36 PM   #52
SY is offline SY  United States
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Sure, but the problem is connotation. When someone in home audio hears the words "damping factor," 8 ohms is reflexively assumed, as is a reactive load (i.e., the existence of something that needs to be damped).
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Old 4th June 2008, 02:39 PM   #53
Sheldon is offline Sheldon  United States
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Default Re: Re: Transformer #44

Thanks Darius

Quote:
Originally posted by oldeurope
Pull the 6SN7 and measure the voltage drop at the cathode resistor of the output triode.
This is the minimum voltage rating for Chb.
Make sure that the resistor is able to handle the power dissipation.
Ah, right. I could do that safely with the resistors I have for the project (5x5W 27k in parallel), but I see your point. C2 needs to be rated nearly the full B+ for full protection (or, the compensation resistors become fuses).


Quote:
Originally posted by oldeurope
The commercial output transformer manufacturers will kill him, hi hi.
Might not be worth the effort to hire the hit men. Not that many looney DIY'rs willing to wind up transformers. Plus, it's a pain getting laminations and the other components. Anyone need some EI84 lams and bobbins- I've got plenty of extra? I don't really do this to save money, just for fun.

Sheldon
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Old 4th June 2008, 03:22 PM   #54
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Quote:
Originally posted by SY
Sure, but the problem is connotation. When someone in home audio hears the words "damping factor," 8 ohms is reflexively assumed, as is a reactive load (i.e., the existence of something that needs to be damped).
Oh, I see what you're saying. I just assume that Damping Factor means impedance ratio from a circuit design perspective. The origin of the term probably has to do with reactive loads so it may not be the best term for this use.

I have seen the term "Drive Factor" but that may be too ambiguous.

Michael
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Old 4th June 2008, 04:31 PM   #55
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Default triode self linearize factor

Hello,
please read this text :
Quote:
http://coupling-triode.blogspot.com/

Grounded cathode and grounded grid circuit: The triode works here without mutal conductance slope distortions if ... By this methode the triode can be operated linearly without applying negative feedback and this is the way that I have designed the RIAA 2007.
This important aspect is covered by the formula, too.
It is a "self linearize" factor for a triode stage.

Kind regards,
Darius
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Old 12th June 2008, 09:20 PM   #56
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Sorry to confuse the situation with such an off the wall variant.
Quite a bit of this design is unfinished. My question for now:
Do I at least have CHB wired correctly?
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Old 13th June 2008, 09:16 AM   #57
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Default #56

Hm, the question is do you need the compensation (Chb)?
I need it because I am using a triode.
Loftin White needs it because g2 is connected to a tapping of the cathode resistor.
Why do you need it?

I know this thread is against the technical forum rules.
But you try to replace tubes by mosfets, this makes the moderators
happy.
BTW: I think the Triodelington is the better triode replacement.
Please note that the use of BJTs is not against the forum rules.

Kind regards,
Darius
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Old 13th June 2008, 01:19 PM   #58
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IGBT " Mu Starver" may provide a near linear gain for
Mu, but the Vacuum Diode transfer function gives us
Triode law X^1.5 "Plate Resistance". Last I read, the
Vacuum Diode was still considered a Tube? My symbol
for Vacuum Diode may not have been legible as such.
There was none in LT-Spice, I drew the best I could.
This stage with the real plate is the only gain stage.

My depletion MOSFET in the input stage? OK, you got
me there. No tube, but it was only intended to have a
unity gain with low impedance, once all resistors have
been scaled accordingly. Call it an inverting follower...
Unity gain followers are nothing new in this thread.
Without this very low (or at least very stable) driving
impedance, the Mu Starver in the next stage may not
be as accurate.

CHB you say is not relevant due to the MOSFET? But
my circuit has full anode feedback, should respond to
power supply noise at the anode, just as-if a Triode.
Not the high impedance PSRR of the usual FET Drain.
Same theory of operation as O.H. Schade (RCA 1938)
6L6 (Screen not strapped to Plate) Triode emulation.
With a PSRR no better than an emulated triode with
Mu=1, CHB seems very relevant here. Have I missed
something?

Your Triodelington does indeed look interesting, and
might be the simpler circuit. For one or both stages...
But relies perhaps too much on the thermal stability
of Beta... Any local feedback to stabilize the Beta also
messes with the behavior of the Triode... IGBT might
be more stable and linear substitute than BJT here.
Might still need to rely on an unbypassed cathode
resistor to sample a voltage for the gate.

Not yet sure how I would take feedback from the OPT
to linearize my iron with the Triodelington?
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Old 13th June 2008, 01:41 PM   #59
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Default #58

Ups,
ok, I'll never answer again questions in incomplete OT circuits without any component values.

Darius
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Old 13th June 2008, 08:32 PM   #60
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What is the fourth circuit topology I am to ignore?
Plate In / Cathode Out??? allready on it...
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