Hello All,
I have several of these and wondering if one can ground the mutual cathode and set each triode with different negative grid bias so that I can use one section as preamp and the other two as push pull output.
I think that it can be done as long as the current in all the sections is the same.
What do you think?
Thanks.
Glass_painter
I have several of these and wondering if one can ground the mutual cathode and set each triode with different negative grid bias so that I can use one section as preamp and the other two as push pull output.
I think that it can be done as long as the current in all the sections is the same.
What do you think?
Thanks.
Glass_painter
Several years ago there was a Hundred Buck Amp Challenge. It was a competition to make a guitar amp for less than $100 in parts cost. I explored several designs early on and one of them used two tubes and a mosfet.
The output stage used a 6MD8. I simply used three or four (don't remember) generic red LED's in series from the cathode to ground. These developed about 10 volts? (again, I don't remember exactly) of cathode bias. Each tube section had a resistor from it's grid to ground so all the bias came from the cathode voltage. One section was intended as the reverb driver so it was a stand alone SE amp stage. It was tested, but never used. The other two sections formed a push pull power amp section which delivered a little over 1 watt cleanly, almost when driven well into clipping. The phase inverter was an LND150 mosfet in split load configuration. The OPT's were small Antek toroids. This part of the amp worked perfectly.
The preamp section used a 6MN8 biased with a single red LED. Each triode section was configured as a voltage amplifier stage. I tried several different configurations but the perf board implementation was always plagued with oscillation, and eventually the entire design went into the box of dead projects to be robbed for parts. I believe much of it still exists (I stole the transformers), and I may try to work on it again some day.
The output stage used a 6MD8. I simply used three or four (don't remember) generic red LED's in series from the cathode to ground. These developed about 10 volts? (again, I don't remember exactly) of cathode bias. Each tube section had a resistor from it's grid to ground so all the bias came from the cathode voltage. One section was intended as the reverb driver so it was a stand alone SE amp stage. It was tested, but never used. The other two sections formed a push pull power amp section which delivered a little over 1 watt cleanly, almost when driven well into clipping. The phase inverter was an LND150 mosfet in split load configuration. The OPT's were small Antek toroids. This part of the amp worked perfectly.
The preamp section used a 6MN8 biased with a single red LED. Each triode section was configured as a voltage amplifier stage. I tried several different configurations but the perf board implementation was always plagued with oscillation, and eventually the entire design went into the box of dead projects to be robbed for parts. I believe much of it still exists (I stole the transformers), and I may try to work on it again some day.
ecll800 power amp conversion
Hello all,
The ecll800 is a two pentode triode tube utilizing mutual cathode and internal connections so it can serve as a single tube small power amp.
My question is can I use the same topology to build an amp utilizing 6MD8 tubes which are triple triodes with mutual cathode.
Logically, I do not see why not.
Your comments are welcome.
Glass painter
Hello all,
The ecll800 is a two pentode triode tube utilizing mutual cathode and internal connections so it can serve as a single tube small power amp.
My question is can I use the same topology to build an amp utilizing 6MD8 tubes which are triple triodes with mutual cathode.
Logically, I do not see why not.
Your comments are welcome.
Glass painter
Please do not start multiple threads on the same subject which is against the forum rules. Your threads have been merged together.I think the ECLL800 triode has mu of 1.5. As I said, you will need to use feedback to get low gain (x-1) using a conventional triode. The other two valves in the ECLL800 are pentodes, so different from the triodes you have. Why do you want to start from a different circuit for a different valve with different characteristics? Do you enjoy setting yourself difficult technical challenges? Or do you somehow think that a circuit for three valves in one envelope must be similar to any circuit for three valves in one envelope?
Hi DF96,
I am an R&D engineer by trade and have been developing new stuff for as long as I can remember - though not in this particular field.
I like minimalistic designs and in this special case would like to build a three element single tube per channel pp headphones amp without self split - this is the challenge, I am not sure it is possible.
So yes, looking for new ways to bend existing designs or come up with new ones.
Anyway, the tube I have for this task are: 6U10, 6av11, 6MD8.
Any help is appreciated.
Glass_painter
I am an R&D engineer by trade and have been developing new stuff for as long as I can remember - though not in this particular field.
I like minimalistic designs and in this special case would like to build a three element single tube per channel pp headphones amp without self split - this is the challenge, I am not sure it is possible.
So yes, looking for new ways to bend existing designs or come up with new ones.
Anyway, the tube I have for this task are: 6U10, 6av11, 6MD8.
Any help is appreciated.
Glass_painter
FWIW you could also use a 2 resistor voltage divider to reduce the gain. However feedback will have the benefit of reducing the Zout.
By the look of the datasheet for 6AV11 it's electrically the same as a 6CG7/6SN7 with a lower total Pd. The three separate cathodes allows for a cathode follower design for the output stage,
Cheers.
By the look of the datasheet for 6AV11 it's electrically the same as a 6CG7/6SN7 with a lower total Pd. The three separate cathodes allows for a cathode follower design for the output stage,
Cheers.
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You might be able to make this work by amplifying one channel as a common-mode signal and the other as differential. Only one PP output stage is necessary in this case, but you'll need two output transformers; one PP and one SE type.
Here's another off-the-wall idea: I think the Murray SEPP circuit might be made to work pretty well with a triple triode per channel. PDF link from another thread here: http://www.diyaudio.com/forums/atta...bes-old-mains-transformers-murrayoriginal.pdf
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