Hi all
Newbie here.
Have picked up a Mikael Abdellah's KT88 SE amp build.
The builder made the speaker outputs with RCA plugs instead of binding posts so I am sending it off to a tech buddy to change these out.
My question is .. Shall I get him modify and change out the input tube to accommodate an ecc83/12ax7 tube?
I have a great selection of ecc83/12ax7's in my collection so would be better for experimentation without buying a bunch of other tubes.
Is the 6n1/6n2 sonically better and should I stick with it?
Cheers in advance.
Niz
New Zealand
Newbie here.
Have picked up a Mikael Abdellah's KT88 SE amp build.
The builder made the speaker outputs with RCA plugs instead of binding posts so I am sending it off to a tech buddy to change these out.
My question is .. Shall I get him modify and change out the input tube to accommodate an ecc83/12ax7 tube?
I have a great selection of ecc83/12ax7's in my collection so would be better for experimentation without buying a bunch of other tubes.
Is the 6n1/6n2 sonically better and should I stick with it?
Cheers in advance.
Niz
New Zealand
12AX7 is very different from 6N1P. It is not good at all to drive the KT88.
You may consider to use 6DJ8 instead.
You may consider to use 6DJ8 instead.
Find a different amplifier circuit that can use your ECC81/12AX7 to its advantage.
Some circuits work better with the ECC81/12AX7 specifications, such as plate impedance rp; mu (u); and transconductance Gm.
You will learn these things as you get more experience.
Note 1:
Off the thread's main subject, but helpful for this amplifier . . . You have 400V B+, it will be more than 400V until the KT88 warms up at power-on.
and, the 6nip takes time to warm up too, so its plate will be at more than 400V at power-on.
So, for the 0.22 uF cap, be sure to use a 600V or 630V rated capacitor there. Do not use a 400V or 450V capacitor there.
Note 2:
The grid resistor for the KT88 is 470k. So do Not use a 6550 there, because it must have 250k Maximum for its grid resistor.
And, 250k will reduce the gain of the 6N1P tube.
Using a grid resistor that is larger than the tubes specified maximum may result in Thermal Run-Away. You do not want to experience that (decades ago, I did experience that . . . Red Plate, not good!).
Happy Building and Happy Listening!
Some circuits work better with the ECC81/12AX7 specifications, such as plate impedance rp; mu (u); and transconductance Gm.
You will learn these things as you get more experience.
Note 1:
Off the thread's main subject, but helpful for this amplifier . . . You have 400V B+, it will be more than 400V until the KT88 warms up at power-on.
and, the 6nip takes time to warm up too, so its plate will be at more than 400V at power-on.
So, for the 0.22 uF cap, be sure to use a 600V or 630V rated capacitor there. Do not use a 400V or 450V capacitor there.
Note 2:
The grid resistor for the KT88 is 470k. So do Not use a 6550 there, because it must have 250k Maximum for its grid resistor.
And, 250k will reduce the gain of the 6N1P tube.
Using a grid resistor that is larger than the tubes specified maximum may result in Thermal Run-Away. You do not want to experience that (decades ago, I did experience that . . . Red Plate, not good!).
Happy Building and Happy Listening!
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Thanks for that.
The amp came with a pair of Svetlana KT88's and a pair of Aperex Brown base XF5 EL34's. To my ears the EL34's sound better with my speakers (Lii Audio Crytal 10's) I will try a few 6DJ8's and see how it sounds. Maybe staying with the Tube that the designer chose for the circuit is best.
hello nizzaloti:
This circuit has been around for a long time and has been reviewed, tested, adjusted, modified, worked over, optimized, played with and more. If you do a few searches you will easily find out everything there is to know about it.
I would look at Audiokarma first and then consider the video series done by Blueglow on Youtube.
Good for you.
Lots of reading to do
This circuit has been around for a long time and has been reviewed, tested, adjusted, modified, worked over, optimized, played with and more. If you do a few searches you will easily find out everything there is to know about it.
I would look at Audiokarma first and then consider the video series done by Blueglow on Youtube.
Good for you.
Lots of reading to do
6dj8 or 6922 tubes are very good in this amp from my experience. Try and find NOS tubes if you can, they tend to be more tolerant of higher voltages for short periods of time.
12at7/Ecc81 would be a better choice than 12ax7. But I won't change the circuit. You have a lot of choices for this circuit as it is.
6aq8/6dj8/6922/6bs8/6bk7..
Find some NOS and try them. I am currently using it with 6bs8.
Have fun
6aq8/6dj8/6922/6bs8/6bk7..
Find some NOS and try them. I am currently using it with 6bs8.
Have fun
6N1P is a very good tube for audio. No real Western equivalent but 6DJ8 is close. 6N23P is Soviet equivalent to 6DJ8.
6N2P is "close" to 12AX7; different construction, similar behavior. Too much gain for this circuit.
If you rewire the tube socket you could try 12AU7 or 12AT7. Not saying it'll sound "better" but they will work.
Amp designers pick tubes for good reasons. Usually best to stick with em.
w
6N2P is "close" to 12AX7; different construction, similar behavior. Too much gain for this circuit.
If you rewire the tube socket you could try 12AU7 or 12AT7. Not saying it'll sound "better" but they will work.
Amp designers pick tubes for good reasons. Usually best to stick with em.
w
Also, Here's a design for an amp that uses 12AX7+KT88:
As you can see, each channel uses both halves of a 12AX7 in a Totem arrangement, perhaps SRPP, I'll defer to an expert on the exact type. Does you no good as you don't have enough holes in your chassis to implement this. But here's what you asked for! Heh.
As you can see, each channel uses both halves of a 12AX7 in a Totem arrangement, perhaps SRPP, I'll defer to an expert on the exact type. Does you no good as you don't have enough holes in your chassis to implement this. But here's what you asked for! Heh.
The Russian 6N1P is a good sounding tube, better than 6922 that some have used to replace it and the 6922 has different operating parameters- not recommended. The Tung Sol ECC85/6AQ8 is reported to sound better than Russian 6N1P but have a gain of 54 vs 38. The tube is somewhat rare. so I would try Tungsram.
f no change use Russian 6N1P-EV. The 6N1P-EV is quieter than 6N1P. I would never use a 12AX7 as it has little drive capacity.
f no change use Russian 6N1P-EV. The 6N1P-EV is quieter than 6N1P. I would never use a 12AX7 as it has little drive capacity.
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