I would like to make a(nother) low-powered EL84 amp.
Rationale:
-EL84 has just the mu we want to drive another EL84
-With the same tube, we get distortion cancellation under a specific bias and voltage setting
-It is a VERY linear tube, and distortion should be extremely low with a CCS load
-Can make a low powered speaker amp, preamp, headphone amp, or driver stage for a 300B, 845, GM70, etc.
-The GE and Sylvania EL84 sounds very similar to a 45 DHT, but has the advantages of indirect heating. The Russian and Chinese tubes won't give that DHT sound, unfortunately.
To accomplish these goals I will use a CCS loaded driver stage and fixed bias on the output EL84. One can use a 12V battery or an adjustable power supply to adjust bias current.
Rationale:
-EL84 has just the mu we want to drive another EL84
-With the same tube, we get distortion cancellation under a specific bias and voltage setting
-It is a VERY linear tube, and distortion should be extremely low with a CCS load
-Can make a low powered speaker amp, preamp, headphone amp, or driver stage for a 300B, 845, GM70, etc.
-The GE and Sylvania EL84 sounds very similar to a 45 DHT, but has the advantages of indirect heating. The Russian and Chinese tubes won't give that DHT sound, unfortunately.
To accomplish these goals I will use a CCS loaded driver stage and fixed bias on the output EL84. One can use a 12V battery or an adjustable power supply to adjust bias current.
An externally hosted image should be here but it was not working when we last tested it.
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Two of my goals for this project are:
(1) to compare the typical cathode bias for EL84 versus fixed bias. I really like the idea of a 9V battery, but have never tried.
(2) to evaluate the sound quality of EL84 as driver compared to others I've used to drive EL84 in the past such as 6DJ8, 12A*7, 12BH7, 5687, etc.
(1) to compare the typical cathode bias for EL84 versus fixed bias. I really like the idea of a 9V battery, but have never tried.
(2) to evaluate the sound quality of EL84 as driver compared to others I've used to drive EL84 in the past such as 6DJ8, 12A*7, 12BH7, 5687, etc.
Have a look also at Thorsten Loesch's "Legacy" amp with SV83/EL84 pentode mode driver for 300B.
http://community.fortunecity.ws/rivendell/xentar/1179/projects/legacy/Legacy.html
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SB
http://community.fortunecity.ws/rivendell/xentar/1179/projects/legacy/Legacy.html
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SB
Have a look also at Thorsten Loesch's "Legacy" amp with SV83/EL84 pentode mode driver for 300B.
http://community.fortunecity.ws/rivendell/xentar/1179/projects/legacy/Legacy.html
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SB
Hi Sven
Regarding this Legacy you posted the problem is the power supply.
I'm interested to assembly a Legacy but with another Power Supply.
Do you have some hints to give me?
Thanks
Jones
I just drew this on a piece of paper. Can you guys look this over before I start building?
An externally hosted image should be here but it was not working when we last tested it.
Based on my tests with many triode connected pentodes with CCS loading I think that the first EL84 will work well with smaller anode current, say 10 mA.
It's linearity is improved if the grid resistor of second EL84 is increased.
The maximum recommended by Philips is 300 k.
It's linearity is improved if the grid resistor of second EL84 is increased.
The maximum recommended by Philips is 300 k.
I just drew this on a piece of paper. Can you guys look this over before I start building?
I did the same, CCS loaded EL84, 10mA, but LED biased, as the first stage in a headphone amp. I was shocked to hear how good some Siemens EL84 sounded, better than any other small pentode I had tried in that position.
Russian 6P14P-EV did not sound as good.
Combo 7189 Bias on Leslie 10x Amps . .
Hi, I'm a little late to this discussion, but came to it while looking at Leslie's model 10x amps.
They have a rather interesting arrangement of Biasing; Cathode loads of 33 Ohm/500uF 6V and -12V applied via 270K to the G1 grids.
I would love to hear the views of the Cogniscenti on this design!
My idea is to use the unit as a 3.1 Home Theater system, with the Pedal amp (large OPTX) as the bass driver, the C and Tibia amps as left and Right channels, and the C# as the Center.
I do understand fully that these are NOT Hi-Fi amps by any stretch of the imagination, but then neither is my auditory sensor subsystem.
I am freshly retired and now finally able to spend as much time as I want playing with valves.
Reference: http://www.captain-foldback.com/Leslie_sub/Leslie_schematics/103.gif
Hi, I'm a little late to this discussion, but came to it while looking at Leslie's model 10x amps.
They have a rather interesting arrangement of Biasing; Cathode loads of 33 Ohm/500uF 6V and -12V applied via 270K to the G1 grids.
I would love to hear the views of the Cogniscenti on this design!
My idea is to use the unit as a 3.1 Home Theater system, with the Pedal amp (large OPTX) as the bass driver, the C and Tibia amps as left and Right channels, and the C# as the Center.
I do understand fully that these are NOT Hi-Fi amps by any stretch of the imagination, but then neither is my auditory sensor subsystem.
I am freshly retired and now finally able to spend as much time as I want playing with valves.
Reference: http://www.captain-foldback.com/Leslie_sub/Leslie_schematics/103.gif
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