For a loong time 6JC6A was available on the $1 list. And a Japanese 6JC6A was available in quantity at $0.35 each. The US 6JC6A had great pentode curves (it's a frame grid tube) and the Japan 6JC6A had great triode mode curves (mu60, pic below).
With a big box of them, I never buy any expensive or mediocre triode tubes.
And if you need a lower mu triode (around 30) there was the 12HL7 on the $1 list. (2nd pic below) A cuve tracer selected 12HL7 leaves the best triodes behind, and in pentode or triode it leaves the D3a behind. Got a big box of them too, $1.
The 6LQ8 pentode (frame grid) makes a super triode (mu 50) too. The extra triode included is somewhat like a 12AT7. 6LQ8 was on the $1 list for years too.
There were others.
With a big box of them, I never buy any expensive or mediocre triode tubes.
And if you need a lower mu triode (around 30) there was the 12HL7 on the $1 list. (2nd pic below) A cuve tracer selected 12HL7 leaves the best triodes behind, and in pentode or triode it leaves the D3a behind. Got a big box of them too, $1.
The 6LQ8 pentode (frame grid) makes a super triode (mu 50) too. The extra triode included is somewhat like a 12AT7. 6LQ8 was on the $1 list for years too.
There were others.
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You must have looked up 6LQ6.
6LQ8 is still relatively cheap (for now at least).
By the way, 21LG6, at $4, is nearly the same tube (as 6LQ6) except for the base. Then 31LZ6 gives you the same base/pin-out and higher gm for like $10 or $15.
There are some odd 6DQ5 tubes around that have either a 6LG6 or 6LQ6 for guts too, with an Octal base. Hard to find though.
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Because they’re being sold by that Bangy Bang tubes guy who has spammed search results with his overpriced junk. $60 6AL5s!
nigelwright7587,
Good point about the difference between a cascade stage of two 12AU7 triodes;
Versus a cascade stage of two 12AX7 triodes.
1. Typical gain of cascade 12AU7 might be 12 x 12 = 144
Typical gain of cascade 12AX7 might be 60 x 60 = 3600
3600/144 = 25:1 (27.96 dB)
So, of course, the 12AX7 cascade will have the following characteristics, versus 12AU7 cascade:
More gain
More noise
More microphonics
Oh . . . and high gain and some wiring layout that causes positive feedback = an oscillator
Just my opinion
2. I like both the 12AU7 and the 12AX7 when used according to their characteristics, and their proper application.
3. Some uncommonly known characteristics of grid leak bias:
Which grid leak bias resistor has more noise voltage at the input grid of an input tube?
The noise power of a resistor at room temperature is approximately -174dBm/Hz, so . . .
1Meg grid leak versus 10k grid leak have equal power, but . . .
1,000,000 /10,000 = 100:1
There is 100 times more voltage in 1 Meg Ohm than the voltage in 10k Ohm. (40 dB more voltage in 1 Meg Ohm).
What makes all this work better, is when the 1 Meg Ohm is shunted by 10K impedance from an electric guitar (or whatever that impedance is, but it surely is a lot less than 1 Meg Ohm).
But if the guitar output has less than 1 Meg Ohm of DC resistance, you have to use a coupling cap from the guitar to the 1 Meg grid leak resistor at the amp input.
Otherwise, the grid, with too low of a DC resistance can not develop the proper grid leak bias.
Oh, is that a vote for eliminating the coupling cap, and using cathode self bias? . . . it is in my book.
Just a little math.
Good point about the difference between a cascade stage of two 12AU7 triodes;
Versus a cascade stage of two 12AX7 triodes.
1. Typical gain of cascade 12AU7 might be 12 x 12 = 144
Typical gain of cascade 12AX7 might be 60 x 60 = 3600
3600/144 = 25:1 (27.96 dB)
So, of course, the 12AX7 cascade will have the following characteristics, versus 12AU7 cascade:
More gain
More noise
More microphonics
Oh . . . and high gain and some wiring layout that causes positive feedback = an oscillator
Just my opinion
2. I like both the 12AU7 and the 12AX7 when used according to their characteristics, and their proper application.
3. Some uncommonly known characteristics of grid leak bias:
Which grid leak bias resistor has more noise voltage at the input grid of an input tube?
The noise power of a resistor at room temperature is approximately -174dBm/Hz, so . . .
1Meg grid leak versus 10k grid leak have equal power, but . . .
1,000,000 /10,000 = 100:1
There is 100 times more voltage in 1 Meg Ohm than the voltage in 10k Ohm. (40 dB more voltage in 1 Meg Ohm).
What makes all this work better, is when the 1 Meg Ohm is shunted by 10K impedance from an electric guitar (or whatever that impedance is, but it surely is a lot less than 1 Meg Ohm).
But if the guitar output has less than 1 Meg Ohm of DC resistance, you have to use a coupling cap from the guitar to the 1 Meg grid leak resistor at the amp input.
Otherwise, the grid, with too low of a DC resistance can not develop the proper grid leak bias.
Oh, is that a vote for eliminating the coupling cap, and using cathode self bias? . . . it is in my book.
Just a little math.
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Many of us here know the " big wizard" Lampizator, especially when he started making updates to CD players to eliminate the "harsh" sound of the Dac's used in the vast majority of "entry level" devices.
The solution was to add tubes to the outlet.
I have not heard them, these experiments are not accessible for reasons of cost, freight, etc. etc. here, in the "*** of the world" .....
But many "high-end" CD player manufacturers, I think, copied the idea. The latter is to be confirmed.
Now, I do not pretend to be a defender or a detractor of Lukas, - my knowledge in electronics is not even remotely close to his -, I only recommend reading it to those who do not know him yet ......
So, on the subject at hand, (the OP opened the thread and has had so far only two minor interventions, but I suppose that in times of pandemic we can forgive any tendency to open threads "just to see what happens" , but I think that statement of the thread title, "bad reputation" has already been disproved ! ...... OMG!
That said, I have not seen Lukas propose or mention anywhere in the proposed modifications to so many amps, that 12AU7 should be replaced, why is that ?
Music Angel XD-800MKIII reworking
The solution was to add tubes to the outlet.
I have not heard them, these experiments are not accessible for reasons of cost, freight, etc. etc. here, in the "*** of the world" .....
But many "high-end" CD player manufacturers, I think, copied the idea. The latter is to be confirmed.
Now, I do not pretend to be a defender or a detractor of Lukas, - my knowledge in electronics is not even remotely close to his -, I only recommend reading it to those who do not know him yet ......
So, on the subject at hand, (the OP opened the thread and has had so far only two minor interventions, but I suppose that in times of pandemic we can forgive any tendency to open threads "just to see what happens" , but I think that statement of the thread title, "bad reputation" has already been disproved ! ...... OMG!
That said, I have not seen Lukas propose or mention anywhere in the proposed modifications to so many amps, that 12AU7 should be replaced, why is that ?
Music Angel XD-800MKIII reworking
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I and lots of people were modifying modestly priced CD players more than 30 years ago, replacing op-amp based solid state electronics with tube based circuitry - in my case 12AX7A/5751/12AU7A based. If you dig around on the internet you can find the original articles I wrote for Positive Feedback.
Old hat, and manufacturers offered tubed CD players long before Lampizator came along.
One of my closest friends from Argentina also refers to it as the "***" of the world. It can't be that bad otherwise everyone would leave.
Old hat, and manufacturers offered tubed CD players long before Lampizator came along.
One of my closest friends from Argentina also refers to it as the "***" of the world. It can't be that bad otherwise everyone would leave.
yes, i did a JJ6l6gc pp amp with a 5814 input and the 6SL7 ltp phase splitter drive and i liked the sound very much, the amp is now somewhere "down under".....owner happy....
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One of my closest friends from Argentina also refers to it as the "***" of the world. It can't be that bad otherwise everyone would leave.
It's not so bad, I love my country, I only said it because of the distance to the north, but Australia is also south of the meridian .....
Cool.. I wondered where the expression came from, now I have a better understanding. I guess when we say the "bottom" of the world it has essentially the same meaning...
I've always been curious about the Atacama desert, I don't suppose I will ever get to see it. I have seen the Negev which was probably enough.. LOL
I've always been curious about the Atacama desert, I don't suppose I will ever get to see it. I have seen the Negev which was probably enough.. LOL
It is exactly like this, we are the country of the "bottom" of the world (southernmost), hence the reference to "The prison at the end of the world" was born.
Don't lose hope, you never know.
Conoce la historia de la carcel del Fin del Mundo - Tolkeyen Patagonia.
Don't lose hope, you never know.
Conoce la historia de la carcel del Fin del Mundo - Tolkeyen Patagonia.
Thank you for hinting at this fantastic tool.
There's quite a selection of tubes, and can be accessed here.
