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02-16-2006 Post does not mapped to Knowledge Tree
peter foster
Australia
Posts 40
Joined on 02-16-2006

Post #: 1
Post ID: 2089
Reply to: 2089
Driver tubes, grid leak biasing, and fidelity

Dear Romy,

I have been reading the threads on GoodSoundClub about your journey with development of the Melquiades and Super Melquiades amplifiers.  They are very interesting to me.  I am pleased that your purpose was to produce a particular amplification result that was in your "mind-eye" so to speak to drive your horn speakers and that you did not feel constrained to operate within what may have been conventions.

I hope that you do not mind answering some of my questions about the Melquiades now that you have some time of experience using them.

---

The thread mentions:
I feel that 6E5P has own very interesting "puss" as Tony Soprano would describe it. This "puss" has something to do with dynamic viscosity and with its ability to sound "dynamically inelegant"....Some people see Melquiades as a 633C-base amp but I see the Melquiades as two stages SET with 6E5P driver...(if I am not mistaken about those PP) and he clamed that all of the amps, though sound differently still were able to express the 6E5P's signature....And since the 6E5P has quite a lot of own power (8W plate dissipation) then it asked to try it..

My question:
By "dynamic viscosity" do you mean the reluctance of an amplifier to be dynamic, i.e., the degree to which an amplifier sounds like it is bogged down, usually as a result of a poor rise time on transients, i.e., poor HF response, or a tube which is badly biased and loaded wrongly which is typical of many tone control stages in generic junk tube amps of the 1950 / 1960 era ?

---

My understanding:
The curves for the 6E5P in tetrode are not a happy picture, but with triode connection it is okay. The 6C33C needs a lot of drive voltage since its amplification factor ( µ factor ) is very low.

My question:
The 6E5P is a russian tube and perhaps the 6CL6 is a near equivalent so instead of 6E5P could 6CL6 be used or even EL84 with equally good results ?

---

My understanding:
It appears that the amplifier does bias a 6E5P with two gas tube regulated positive and negative voltages so that a negative voltage can be derived from a resistance divider and applied to the input tube grid.  While some holy audio priests say electro caps are forbidden ( unless perhaps thay are Black Gate or some other expensive brands) there is not much wrong with a Nichicon 1,000 uF cap to bypass cathodes.  At 100Hz they have 16 ohms of reactive impedance and there does not seem to be much evidence that their sonic signature can be detected in any AB tests.

My question:
Did you consider instead using an electrolytic and R used to provide cathode bias ?

---

The thread mentions:
It was 10PM and it was like an instant bliss. It immediately reimbursed me with the exact sound that I was visualizing for quite along time. It slowed down the brutal and unreasonably fast dynamics, it harmonized and coordinated everything and set the correct relation and reasoning between the pitches, it created completely different phenomenal (!) bass and it basically made up the Milq sound in a way in which it is know today.

My understanding:
I can understand that by not using an input coupling cap the amplifier can produce quality bass.

My question:
Do you still believe that the brutal and unreasonably fast dynamics were corrected by the method of biasing the input tube?

My question:
If so, then could the same result be produced by using a standard 0.47 uF coupling cap with 150k bias R then -3dB = 2.2Hz, with no perceivable sonic difference.

---

My understanding:
Milking voltage on a resistor is the use of what was known as grid leak biasing. This is where a 10Meg ohm R is used instead of say a typical 220k. There is always some very low current flow in a bias resistor feeding a grid, enough to usually cause about say -0.1V appear at the end of a 220k in a small power tube, and when 10M is used, the same current flows, but gives a voltage of -9V at the grid if the bias resistor is grounded at its other end.

My question:
Now that you have some time of experience with the amplifiers, have you found this to be a reliable biasing method ?

---

My lack of understanding:
I am not sure of the output impedance for the amplifier, however, if we have a triode with Ra = 80 ohms, its load would be about 320 ohms at the anode, so the RL/Ra = 320/80 = 4.0, so the damping factor is 4. If the load match was for 6 ohms, then the OPT has a Z ratio = 320/6 = 53.3:1, so the source R = 80ohms/53.3 = 1.50 ohms, so if the speaker is 6 ohms, it is being fed from a source of 1.5 ohms, so if the speaker Z fell to 3 ohms at some F the output voltage would fall considerably.  The price for no FB is high output source resistance unless the OPT ratio is high. Higher than standard OPT ratios make an amp inefficient, but the higher the load used with a low load match the lower the THD/IMD becomes, and fidelity is improved.

My question:
Do you think that it could actually be this lower THD/IMD that has lifted the veil so to speak and simply the improved fidelity that is making you so happy with the results ?

Regards,
Peter.

02-16-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,515
Joined on 05-28-2004

Post #: 2
Post ID: 2091
Reply to: 2089
Re: Driver tubes, grid leak biasing, and fidelity

 peter foster wrote:
By "dynamic viscosity" do you mean the reluctance of an amplifier to be dynamic, i.e., the degree to which an amplifier sounds like it is bogged down, usually as a result of a poor rise time on transients, i.e., poor HF response, or a tube which is badly biased and loaded wrongly which is typical of many tone control stages in generic junk tube amps of the 1950 / 1960 era ?

Actually, the Milq has no problems with dynamic; in fact it is the most dynamic amplifier I even heard. By the "dynamic viscosity" I did not mean the dynamic itself by rather the dynamic of dynamic, or the dynamic of changing the dynamics. I mend sound do not “dive” into nothingness and do not rise to some kind of dynamic absolute but rather it moves across the dynamic range according own some kind of pattern. Sometime it has “sticky” dynamic of dynamic and sometime aggressive dynamic of dynamic. It has own brain and has own reasoning… Interestingly that this own “reasoning” make sound much more like acoustic sound.

 peter foster wrote:
The 6E5P is a russian tube and perhaps the 6CL6 is a near equivalent so instead of 6E5P could 6CL6 be used or even EL84 with equally good results ?

6E5P, in the given application, with the given biasing method is the hart of the amp. I am sure you might fine a lot of tubes that might swing the same voltage and fulfill other electrical requirements but it will have a very little to do with sound. 6E5P and the way in which it was used was use explicitly because the very specific sonic characteristics. Would the 6CL6, EL84/6N14P have the same sonic qualities? Whatever it will be it will be a totally different amplifier about which I have no business to comment.

 peter foster wrote:
It appears that the amplifier does bias a 6E5P with two gas tube regulated positive and negative voltages so that a negative voltage can be derived from a resistance divider and applied to the input tube grid.  While some holy audio priests say electro caps are forbidden ( unless perhaps thay are Black Gate or some other expensive brands) there is not much wrong with a Nichicon 1,000 uF cap to bypass cathodes.  At 100Hz they have 16 ohms of reactive impedance and there does not seem to be much evidence that their sonic signature can be detected in any AB tests.

I religiously against Black Gate capacitors and religiously against the Sound that Black Gate create. Furthermore I have very-very high prejudices against people who feel that Black Gate capacitors are useful for sound. From my point of view those people juts have no idea what to listed while they are listening.
 peter foster wrote:
Did you consider instead using an electrolytic and R used to provide cathode bias ?

To ground cathodes was the very primary objective of the entire design. I see no reasons to lift cathodes from ground.
 peter foster wrote:
The thread mentions:
It was 10PM and it was like an instant bliss. It immediately reimbursed me with the exact sound that I was visualizing for quite along time. It slowed down the brutal and unreasonably fast dynamics, it harmonized and coordinated everything and set the correct relation and reasoning between the pitches, it created completely different phenomenal (!) bass and it basically made up the Milq sound in a way in which it is know today.
My understanding:
I can understand that by not using an input coupling cap the amplifier can produce quality bass.

Nope, you misunderstood it. We never even consider using the input-coupling cap. Input input-coupling cap would be necessary to support the language of amplification ceremony but not for the purpose of amplification.
 peter foster wrote:
Do you still believe that the brutal and unreasonably fast dynamics were corrected by the method of biasing the input tube?

I would not use word “corrected”. The current Milq’s biasing did change the sound very dramatically and in very right direction. Was it “correction” or not I do not know. I personally do not think so because a “correction” presumes the something was initially right and then got screwed. The Milq was not created by “correcting” the wrong things but rather by attempt of creating of the initially right things.
 peter foster wrote:
My question:
If so, then could the same result be produced by using a standard 0.47 uF coupling cap with 150k bias R then -3dB = 2.2Hz, with no perceivable sonic difference.

Why do you need a coupling cap? The topology, the superstructure of the amlifers, requires a coupling cap to blocs DC from inputs. Does Sound require this coupling cap?
 peter foster wrote:
My question:
Now that you have some time of experience with the amplifiers, have you found this to be a reliable biasing method ?

Peter, why do you have a question about the reliability? I personally did not experience any problems but what kind problems even theoretically could be? The positive bias tube goes down? So what, when a source is connected then the positive bias tube serves no purpose and the DC voltage is grounded on the source output. You actually could pull the positive bias tube out of the socket while the amps is paling with no problems. The negative bias tube goes down? So what, the tube goes down and stops to regulate. The negative bias supply become form 148V 195V that will raise the fist tube bias from minus 3.4V to minus a few volts higher, effectively closing down the first tube. The raise of the bias will not be anthem too strong to rise above the max bias voltage for the tube. I have many-many time during the assembling and testing when I did all imaginable things with the biasing tubes and I did not detect any issues with reliability.
 peter foster wrote:
My lack of understanding:
I am not sure of the output impedance for the amplifier, however, if we have a triode with Ra = 80 ohms, its load would be about 320 ohms at the anode, so the RL/Ra = 320/80 = 4.0, so the damping factor is 4. If the load match was for 6 ohms, then the OPT has a Z ratio = 320/6 = 53.3:1, so the source R = 80ohms/53.3 = 1.50 ohms, so if the speaker is 6 ohms, it is being fed from a source of 1.5 ohms, so if the speaker Z fell to 3 ohms at some F the output voltage would fall considerably.  The price for no FB is high output source resistance unless the OPT ratio is high. Higher than standard OPT ratios make an amp inefficient, but the higher the load used with a low load match the lower the THD/IMD becomes, and fidelity is improved.
My question:
Do you think that it could actually be this lower THD/IMD that has lifted the veil so to speak and simply the improved fidelity that is making you so happy with the results?

I disagree that there is such a thing as standard OPT ratios. More loaded tube is slower, has more harmonics and more blunt parabola with a tone rolls to it’s peach. More idle tube has shaper sound; more steep the parabola profile and fewer harmonics. (Let disregard the inefficient as something that is not important). I would not know what “lift the veil” would mean. The sound after amplifier should have (as close as possible) a correct (acoustic-like) harmonic content, across the spectrum and across the dynamic range. All the rest is the business of the loudspeakers. Of course me, like anyone else made a number of tests how to load the plates of the 6C33C to my specific drivers. In my case, if I am not mistaken the HF/MF and Upper bass channel is loaded to 1200Ohm (single plate of 6C33C) and LF channel to 625 (Full 6C33C)

Rgs,
Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-17-2006 Post does not mapped to Knowledge Tree
AnonymousUser
Posts 19
Joined on 11-27-2004

Post #: 3
Post ID: 2094
Reply to: 2091
Re: Driver tubes, grid leak biasing, and fidelity

peter wrote:
By "dynamic viscosity" do you mean the reluctance of an amplifier to be dynamic, i.e., the degree to which an amplifier sounds like it is bogged down, usually as a result of a poor rise time on transients, i.e., poor HF response, or a tube which is badly biased and loaded wrongly which is typical of many tone control stages in generic junk tube amps of the 1950 / 1960 era ? 
 
Romy replied:
Actually, the Milq has no problems with dynamic; in fact it is the most dynamic amplifier I even heard. By the "dynamic viscosity" I did not mean the dynamic itself by rather the dynamic of dynamic, or the dynamic of changing the dynamics. I mend sound do not "dive" into nothingness and do not rise to some kind of dynamic absolute but rather it moves across the dynamic range according own some kind of pattern. Sometime it has "sticky" dynamic of dynamic and sometime aggressive dynamic of dynamic. It has own brain and has own reasoning. Interestingly that this own "reasoning" make sound much more like acoustic sound.

---

peter wrote:
The 6E5P is a russian tube and perhaps the 6CL6 is a near equivalent so instead of 6E5P could 6CL6 be used or even EL84 with equally good results ? 
 
Romy replied:
6E5P, in the given application, with the given biasing method is the hart of the amp. I am sure you might fine a lot of tubes that might swing the same voltage and fulfill other electrical requirements but it will have a very little to do with sound. 6E5P and the way in which it was used was use explicitly because the very specific sonic characteristics. Would the 6CL6, EL84/6N14P have the same sonic qualities? Whatever it will be it will be a totally different amplifier about which I have no business to comment.

Peter writes:
My understanding had been that biasing method is a method of setting up a given tube so it works with the wanted anode current at idle with the wanted anode voltage and these conditions are met by somehow applying a correct grid DC voltage and that properly implemented biasing could always be done several different ways and the tube would have exactly the same harmonics and sound during normal AC signal operation.

---

peter wrote:
It appears that the amplifier does bias a 6E5P with two gas tube regulated positive and negative voltages so that a negative voltage can be derived from a resistance divider and applied to the input tube grid.  While some holy audio priests say electro caps are forbidden ( unless perhaps thay are Black Gate or some other expensive brands) there is not much wrong with a Nichicon 1,000 uF cap to bypass cathodes.  At 100Hz they have 16 ohms of reactive impedance and there does not seem to be much evidence that their sonic signature can be detected in any AB tests. 
 
Romy replied:
I religiously against Black Gate capacitors and religiously against the Sound that Black Gate create. Furthermore I have very-very high prejudices against people who feel that Black Gate capacitors are useful for sound. From my point of view those people juts have no idea what to listed while they are listening.

Peter writes:
Sorry Romy, perhaps I was not clear in what I wrote but I wish to understand the engineering if that is possible of how one well implemented method of biasing such as grid leak biasing produces a different sound from an amplifier over another well implemented method of biasing such as using a Nichicon 1,000 uF cap to bypass cathodes.

---

peter wrote:
Did you consider instead using an electrolytic and R used to provide cathode bias ? 
 
Romy replied:
To ground cathodes was the very primary objective of the entire design. I see no reasons to lift cathodes from ground.

Peter writes:
My understanding had been that cathodes are considered by many audio and radio engineers to be grounded when they have an R&C circuit between cathode and 0V.  The R allows a DC voltage to appear across itself according to Ohms Law, V = I x R.  But at audio signal F the C forms a low impedance path for current.  3,200 uF has 0.5 ohms of impedance at 100Hz.  At 0.001Hz, getting close to DC, the cap impedance is quite high, and is 50,000 ohms.  At 2 kHz where the ear is most sensitive the 3,200 uF has Z = 0.025 ohms, or extremely low in comparison to the other circuit impedances where it is located.  However, in the past, C used for the C in the R&C signal bypass circuits were often only 25uF across say 500 ohms of R, so at LF there was always some unwanted current FB with a phase shift that reduced the bass response slightly. But even so, where ZC = R is at 12.8 Hz.  With C = 1,000 uF the pole between 500 ohms and 1,000 uF is at 0.32 Hz, so bass response roll off due to R&C bypassing cannot easily be measured and the amount of cathode current FB at signal F is entirely inconsequential.

---

peter wrote:
The thread mentions:
It was 10PM and it was like an instant bliss. It immediately reimbursed me with the exact sound that I was visualizing for quite along time. It slowed down the brutal and unreasonably fast dynamics, it harmonized and coordinated everything and set the correct relation and reasoning between the pitches, it created completely different phenomenal (!) bass and it basically made up the Milq sound in a way in which it is know today.  I can understand that by not using an input coupling cap the amplifier can produce quality bass.
 
Romy replied:
Nope, you misunderstood it. We never even consider using the input-coupling cap. Input input-coupling cap would be necessary to support the language of amplification ceremony but not for the purpose of amplification.

Peter writes:
My understanding had been that input caps are quite okay at amp inputs if they do not reduce the response wanted from the amps.  Some people who want the best bass response possible, believe they can achieve that by using all solid state amps which have no cap couplings within and have a squillion dB of NFB which is greatest at DC.  Some other people are happy with -3dB response at 10Hz, so then using a 0.47 uF cap to feed a bias R of say 200k will produce a "pole", i.e., -3dB point at 1.7Hz, which is so far below the 10Hz that at 10Hz the additional C-R coupling will only make a level change of a fraction of a DB and for human beings it would be quite inaudible.

---

peter wrote:
Do you still believe that the brutal and unreasonably fast dynamics were corrected by the method of biasing the input tube? 
 
romy replied:
I would not use word "corrected". The current Milq's biasing did change the sound very dramatically and in very right direction. Was it "correction" or not I do not know. I personally do not think so because a "correction" presumes the something was initially right and then got screwed. The Milq was not created by "correcting" the wrong things but rather by attempt of creating of the initially right things.

Peter writes:
My understanding had been that there would be no engineering explanation for why well implemented biasing methods in class A signal tubes should change the AC operation and distortion character of the tube.

---

peter wrote:
My question:
If so, then could the same result be produced by using a standard 0.47 uF coupling cap with 150k bias R then -3dB = 2.2Hz, with no perceivable sonic difference. 
 
Romy replied:
Why do you need a coupling cap? The topology, the superstructure of the amlifers, requires a coupling cap to blocs DC from inputs. Does Sound require this coupling cap?

Peter writes:
My understanding had been that when connected to a preamp with DC at its output, this DC could be amplified, and many speakers do not like DC.  Also, slow moving signals below say 10Hz including DC can be regarded by many people as nuisance garbage so a cap is put in at the front end to keep such stray signals out.  Less stray LF noise would perhaps improve the sound.  As long as the pole at the amp input is low enough the cap has not much effect.  Most tube amps are bandwidth limited devices which means that because of their OPT and coupling caps, the F range is limited. So most good tube amps will go from 5Hz to 65kHz at low levels, but some would be quite distressed with a high level signal of 5Hz at full power because of OPT saturation effects; even at 1/10 of full power, 5Hz will cause saturation in some OPT. But luckily, music F rolls off fast below 30Hz.

---

peter wrote:
My question:
Now that you have some time of experience with the amplifiers, have you found this to be a reliable biasing method ? 
 
Romy replied:
Peter, why do you have a question about the reliability? I personally did not experience any problems but what kind problems even theoretically could be? The positive bias tube goes down? So what, when a source is connected then the positive bias tube serves no purpose and the DC voltage is grounded on the source output. You actually could pull the positive bias tube out of the socket while the amps is paling with no problems. The negative bias tube goes down? So what, the tube goes down and stops to regulate. The negative bias supply become form 148V 195V that will raise the fist tube bias from minus 3.4V to minus a few volts higher, effectively closing down the first tube. The raise of the bias will not be anthem too strong to rise above the max bias voltage for the tube. I have many-many time during the assembling and testing when I did all imaginable things with the biasing tubes and I did not detect any issues with reliability.

Peter writes:
My understanding had been that tube aging does not rest well with grid leak biasing and that grid leak biasing was confined to AM radio makers who used it in preference to other methods primarily for cost purposes.

---

peter wrote:
My lack of understanding:
I am not sure of the output impedance for the amplifier, however, if we have a triode with Ra = 80 ohms, its load would be about 320 ohms at the anode, so the RL/Ra = 320/80 = 4.0, so the damping factor is 4. If the load match was for 6 ohms, then the OPT has a Z ratio = 320/6 = 53.3:1, so the source R = 80ohms/53.3 = 1.50 ohms, so if the speaker is 6 ohms, it is being fed from a source of 1.5 ohms, so if the speaker Z fell to 3 ohms at some F the output voltage would fall considerably.  The price for no FB is high output source resistance unless the OPT ratio is high. Higher than standard OPT ratios make an amp inefficient, but the higher the load used with a low load match the lower the THD/IMD becomes, and fidelity is improved.

Peter wrote:
Do you think that it could actually be this lower THD/IMD that has lifted the veil so to speak and simply the improved fidelity that is making you so happy with the results? 
 
Romy replied:
I disagree that there is such a thing as standard OPT ratios. More loaded tube is slower, has more harmonics and more blunt parabola with a tone rolls to it's peach. More idle tube has shaper sound; more steep the parabola profile and fewer harmonics. (Let disregard the inefficient as something that is not important). I would not know what "lift the veil" would mean. The sound after amplifier should have (as close as possible) a correct (acoustic-like) harmonic content, across the spectrum and across the dynamic range. All the rest is the business of the loudspeakers. Of course me, like anyone else made a number of tests how to load the plates of the 6C33C to my specific drivers. In my case, if I am not mistaken the HF/MF and Upper bass channel is loaded to 1200Ohm (single plate of 6C33C) and LF channel to 625 (Full 6C33C).

Peter writes:
Okay, about 600 to 1,200 ohms for 1/2 a 6C33C will do, so about 400 ohms for a whole tube, and that's not far away from a guess of 320 ohms.  400 to 1,000 ohms would give the better fidelity, but less maximum power, which is okay if we have horns where max power is irrelevant.

Peter writes:
My understanding had been that OPT ratios for triodes RL should exceed 4 x Ra and for pentodes and tetrodes which have loads = 0.9 Ea / Ia, where Ea is the idle anode voltage, Ia is the idle current, RL << Ra.

---

Regards,
Peter.

02-17-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,515
Joined on 05-28-2004

Post #: 4
Post ID: 2095
Reply to: 2089
I am not an electrician.

 peter foster wrote:
My understanding had been that biasing method is a method of setting up a given tube so it works with the wanted anode current at idle with the wanted anode voltage and these conditions are met by somehow applying a correct grid DC voltage and that properly implemented biasing could always be done several different ways and the tube would have exactly the same harmonics and sound during normal AC signal operation.

Peter, I disagree with many assumptions you make. You view a circuit only from a perspective of propagation of currents but there is a lot more to it.  Defiantly to set the different parts of the circuit to operate within the wanted conditions is a noble task but is it sufficient enough for shaping Sound? No all aspect of Sound might be described by harmonic patterns, measured by distortion analyzer and extrapolated inot voltages and hertzes. If it would be so then probably any person who has a multi-meter and scope would have good sound in his/her listening room: as you know it is not the case..  Furthermore the most hard-core "electricians" in audio usually end up with most disable-sounding amplifiers.

Anyhow, there are many biasing method and despite that all of them in the end set a given tube to work with a wanted anode current at idle with the wanted anode voltage but Sound that this tube /stage produce will very different with different biasing method. It would vary form tube to tube, from application to application and we can’t not blindly look at it using a targeted plate current/voltage as an abstract reference. To understand that it requires embracing very different thinking about the entire mechanism of amplification, it’s goal, the definition of success, and to clear recognize the differences between the essential foundation of process and a language (superstructure) that exists juts to support the survival of the process’s foundation.
 
 peter foster wrote:
My understanding had been that there would be no engineering explanation for why well implemented biasing methods in class A signal tubes should change the AC operation and distortion character of the tube.

In case of Milq’s first stage, there are explanations (I have writhen about it) but I do not believe to those explanations and I have many contra- arguments against those explanations. Once again, if you look tan the biasing of the Melquiades first stage ONLY from a perspective of maintaining a necessary negative potential on grid then it would not make any sense to you.
 peter foster wrote:
My understanding had been that when connected to a preamp with DC at its output, this DC could be amplified, and many speakers do not like DC. 

Peter, first off all Milq has no DC it inputs (the is what the positive gas tube is for). Second, if it has then what would happen? Absolutely nothing. I played Milq in past with many-many volts at input and it only affect sound when you switching volume control…
 peter foster wrote:
  My understanding had been that tube aging does not rest well with grid leak biasing and that grid leak biasing was confined to AM radio makers who used it in preference to other methods primarily for cost purposes.

The gas regulators tube when they age they pick some nose and nothing else. There are no even theoretical issuers with the ratability of gas tubes in my case. It used in many many many circuits as voltage reference… how many of them you have seen to went down? If the gas tube do go down then it juts stop regulate, nothing else. Also, I do not care about  “AM radio makers who used it in preference to other methods” as they had totally different objectives in thier design and used gas tubes for totally different purpose. Peter, if you stop to look at the Milq as at a “voltage arrangement devises” then you might discover that the gas tubes in Melquiades used not for a voltage regulation but as the current decoupling devises.,,
 peter foster wrote:
Okay, about 600 to 1,200 ohms for 1/2 a 6C33C will do, so about 400 ohms for a whole tube, and that's not far away from a guess of 320 ohms.  400 to 1,000 ohms would give the better fidelity….

Of course all configurations (more loading and less loading) were heard and evaluated. Frankly speaking, Peter: how you might propose that something might have a “better fidelity” without knowing the compliance of the specific drivers and without performing the actual listening?
 peter foster wrote:
My understanding had been that OPT ratios for triodes RL should exceed 4 x Ra and for pentodes and tetrodes which have loads = 0.9 Ea / Ia, where Ea is the idle anode voltage, Ia is the idle current, RL << Ra.

Perhaps, but I do not follow those rules. Dima, proposed initially to start loading the plate with 10X but then, playing with plate voltages, current and combining the section of the secondary we end up with whatever we and up.

Rgs,
Romy

 




"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-17-2006 Post does not mapped to Knowledge Tree
AnonymousUser
Posts 19
Joined on 11-27-2004

Post #: 5
Post ID: 2099
Reply to: 2095
Re: I am not an electrician.
Dear Romy,

I appreciate your patience with my electrical questions.

As a good friend mentioned to me when discussing the unsolved mysteries of tubes amplifiers "I look out at the stars, the God Of Triodes winks at me, I know I cannot know what a God knows".

Regards,
Peter.
02-17-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,515
Joined on 05-28-2004

Post #: 6
Post ID: 2100
Reply to: 2099
My very different objectives

 AnonymousUser wrote:

I appreciate your patience with my electrical questions.

As a good friend mentioned to me when discussing the unsolved mysteries of tubes amplifiers "I look out at the stars, the God Of Triodes winks at me, I know I cannot know what a God knows".
Peter,

I would not share the vision of your friend. I do not like the mystification and if I (or anyone else) do not know answers then it doe not mean the answers do exist. For some people the birth of speckled and spotted sheep from while parents might appears as a mystery that God of Triodes winks but for the shepherd Jacob, when he proposed his demands to Laban, it was not a result of super-magic winking but rather the outcome of reasonable and targeted actions. I would propose the Melquiades effect is the result of targeted materialization when a desire of getting a certain sound involuntarily filters out the methods that might not serve this Sound. Was this find accidental? Yes in a way, but neither Dima nor I were paying attention to the God’s winking but rather to the delta between the targeted and achievable Sound. My personal mind, whatever is left, does not question anything further then getting good Sound. When I get it then I discard the process and exercise Result. Dima, as a professional radio-engineer, does care about the inner-reasoning of the processes and perhaps you need to talk with him about the theory of the Melquiades’ under-hood.

Rgs,
Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-22-2006 Post does not mapped to Knowledge Tree
deemon
Posts 23
Joined on 05-25-2004

Post #: 7
Post ID: 2121
Reply to: 2100
Re: My very different objectives

Grid leak bias is not reliable itself . Grid current is very low and grid resistor is very big , the circuit become very sensitive to all destabilizing factors - capacitor leak , humidity , temperature . And when we apply a big input signal to the tube - average grid leak current can change too , it will recharge input capacitor and change operation point of the tube , so I don't like this bias method ...

Dima

02-22-2006 Post does not mapped to Knowledge Tree
peter foster
Australia
Posts 40
Joined on 02-16-2006

Post #: 8
Post ID: 2122
Reply to: 2121
Re: My very different objectives
Dima, thank you for your explanation.

I would very much appreciate understanding "the inner-reasoning of the processes and . . . about the theory of the Melquiades and under-hood".  I am sure that there are many other people who would also be very interested in the same.

Regards,
Peter.
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