it was a Broskie CCDA line amp, no, i did not hear any difference in sound , i did not measure the gain but i am pretty sure there was a drop in gain...
mu in a pentode is in the high 300's, it is mostly ignored, mu in any 12a*7 triodes varied to 100, a triode is like a Thevenin voltage source, a pentode is like a Norton....
tube parameters vary from tube to tube, even with the same part number, even between manufacturers, and yes even between sections inside of an envelope, just goes to show that no two things are exactly alike...
"even Eimac's 1500 Watt triode has the same relationships as the 12AX7" yes they are triodes, but you treat them accordingly....
^the orange is squeezed to get the juice....the quest for knowledge never ends till the day you die...
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My comment was meant to point out that this is all old news, well-documented, been there/done that. It's all in the data sheets, which are readily accessible at frank.pocnet.net (which is a fantastic resource!).
Organizing a little data, in the quest for knowledge.
NB - Some of the data on the Russian tubes is a little suspicious. I'm not sure I believe that the max plate voltage for a 6N23P is 300V, or that its max heater-cathode voltage is 200V. But hey, maybe I'm wrong. Has anybody tested this?
Also, MerlinB measured the heater current of a few ECC88 and E88CC tubes and found that they all drew 300mA (at 6.3V). He found that the ECC88 did not draw 365mA as shown in the data sheet. Go figure.
Organizing a little data, in the quest for knowledge.
NB - Some of the data on the Russian tubes is a little suspicious. I'm not sure I believe that the max plate voltage for a 6N23P is 300V, or that its max heater-cathode voltage is 200V. But hey, maybe I'm wrong. Has anybody tested this?
Also, MerlinB measured the heater current of a few ECC88 and E88CC tubes and found that they all drew 300mA (at 6.3V). He found that the ECC88 did not draw 365mA as shown in the data sheet. Go figure.
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there is a context, tubes in the cutoff conditions can have much higher plate voltage than datasheets suggest..
else, maximum plate dissipation limits what voltage you can apply..
for peanut tubes, a small percentage of plate dissipation ratings, that is why these peanut tubes are hard to die...
6KN8 = Japanese version of 6DJ8 or 6922
6EU7 = 12AX7 with a different pinout (for reduced noise)
6DT8 = extremely similar to 12AT7 but with a 6.3V heater (12DT8 has 12.6V only heater, no heater center tap.)
The others are not easily found in the US, so I don't worry about them.
i have those tubes, btw, i also made a similar chart like yours many years ago but lost them when my hardrive crashed, can you make an exel file so i can add to it and post here? thanks...
Double Blind test, with multiple listeners, and an independent operator changing the switch position (and the operator did not know which switch setting selected which tube?
Either 2 identical stereo preamps with different tube types in one preamp versus the tube types in the other preamp;
Or, the identical music signal (like Either Left Or Right signal from a CD player, not both) paralleled to both the L and R channel inputs, and an output switch to listen to the output of the preamps L channel, then to the preamps R channel?
No "audio memory" required to do these listening test.
Anything less might be suspect.
I remember a double blind test run at an early VSAC conference, but that one required "Audio Memory" to do the mental comparison.
Years later I ran a double blind test at the last VSAC conference (but that one was flawed, because I did not use a single speaker, instead of the two speakers that had slightly different positions (and those two positions relative to the listener's ear(s), and the multiple listeners that may have been in front of them, cutting off the direct sound (and with respect to one speaker, but not the other).
We learn when we set up such a double blind fold listening test.
Just my opinions.
Have fun setting up such a test!
Either 2 identical stereo preamps with different tube types in one preamp versus the tube types in the other preamp;
Or, the identical music signal (like Either Left Or Right signal from a CD player, not both) paralleled to both the L and R channel inputs, and an output switch to listen to the output of the preamps L channel, then to the preamps R channel?
No "audio memory" required to do these listening test.
Anything less might be suspect.
I remember a double blind test run at an early VSAC conference, but that one required "Audio Memory" to do the mental comparison.
Years later I ran a double blind test at the last VSAC conference (but that one was flawed, because I did not use a single speaker, instead of the two speakers that had slightly different positions (and those two positions relative to the listener's ear(s), and the multiple listeners that may have been in front of them, cutting off the direct sound (and with respect to one speaker, but not the other).
We learn when we set up such a double blind fold listening test.
Just my opinions.
Have fun setting up such a test!
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i am not advocating people did what i did in my amplifiers, or that they do as i did, i would even go so far as to say, "folks do not try this at home" that is for me alone, but i share them if only to tell others that there is a world out there that you may have not seen...
The relationships of u, rp, and Gm are pretty much the same for most . . .
Triode Wired Pentodes and Triode Wired Beam Power tubes.
(Triode Wired u, essentially the g2/g1 u, and etc for Gm and for rp).
Quite similar to an air filled adjustable volume room with the Three way STP relationship.
Vary any one factor, and . . .
Having designed and built a few triode wired pentodes, and lots of triode wired beam power tubes, I have experienced those relationships
of u, rp, and Gm.
Your Mileage May Vary
I have also done a fair amount of Tube Rolling of different types of tubes, Triode wired pentode versus beam power tube;
and multiple types of triode wired beam power tubes versus each other.
Your Mileage May Vary.
That is what I am sharing, just my experiences.
Triode Wired Pentodes and Triode Wired Beam Power tubes.
(Triode Wired u, essentially the g2/g1 u, and etc for Gm and for rp).
Quite similar to an air filled adjustable volume room with the Three way STP relationship.
Vary any one factor, and . . .
Having designed and built a few triode wired pentodes, and lots of triode wired beam power tubes, I have experienced those relationships
of u, rp, and Gm.
Your Mileage May Vary
I have also done a fair amount of Tube Rolling of different types of tubes, Triode wired pentode versus beam power tube;
and multiple types of triode wired beam power tubes versus each other.
Your Mileage May Vary.
That is what I am sharing, just my experiences.
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true much like the Pi to the circumference and diameter of a circle, but in that case, fixed unlike in case of tubes..
mu varies as cathode currents and plate voltages in a tube varied, never fixed to all points, vaies...
in my case i never tell people, i let them talk back to me, that way i learn a lot since i know how i made the amp, they don't, but their feedback is a gem for me that i treasure...
TonyTecson,
Thanks!
As I already stated . . . of course different voltages and currents will change u, rp, or Gm.
If you yank on any one of the three . . . one or the other remaining two factors will vary, or even both of the two remaining factors will vary.
Thanks!
As I already stated . . . of course different voltages and currents will change u, rp, or Gm.
If you yank on any one of the three . . . one or the other remaining two factors will vary, or even both of the two remaining factors will vary.
If there is differences, what is the dist spectrum changes ? And in what circuit ?
to be honest about it, myself did not hear significant difference, but the audiophile who listened to it said he would take the 6n23 line amp since it beat his bugle boy 6dj8 in the same line amp, that was the last time isaw that preamp...he took cash and gave it to me, who am i to complain....???
I measured some 100 ECC88-style tubes in a preamplifier line stage. The curcuit is an SRPP with B+ = 300V. The cathode resistors are 1.5k, the lower resistor is not bypassed. The input signal is 1V/1kHz, measuring BW is 400Hz to 30kHz. The tubes were mostly red paint Tungsram, some Siemens, Mullard, Dario, Adzam, and a few 6N23B-EV. The average gain was around 14x-15x, S/N around 111-113 dB, k=0.4%-0.5%. In general, the Russian tubes has a little more gain (15x) but other than that there was no significant difference in S/N or k. The (Tungsram) PCC88 tubes had less gain (13x-14x) and somewhat higher noise (-110dB). The heating was 6.3VDC throughout.
All in all, there were more differences between the individual devices than between the different vendors.
I did not conduct a listening test between one and the other, just picked the highest gain with highest S/N an lowest k% (a compromise).
All in all, there were more differences between the individual devices than between the different vendors.
I did not conduct a listening test between one and the other, just picked the highest gain with highest S/N an lowest k% (a compromise).
The lower cathode resistor is not bypassed . . .
That may be one reason why tubes with u = 33, the gain is only 14x to 15x.
But the distortion is lower without the bypass cap there, up until the signal voltage to the grid is the same as the bias voltage
(less dynamic range without the bypass cap because of the lower gain, but lower distortion because of the 'missing' bypass cap.
That may be one reason why tubes with u = 33, the gain is only 14x to 15x.
But the distortion is lower without the bypass cap there, up until the signal voltage to the grid is the same as the bias voltage
(less dynamic range without the bypass cap because of the lower gain, but lower distortion because of the 'missing' bypass cap.