I've become enamored of dual-dissimilar triodes recently; spud amps just seem like fun to me. I've built a 6T9 and ECL82 and ECL86 amps.
I recently saw a nice-looking schematic for a 6CY7, a Novar base tube intended for television use originally.
6CY7 Single-Ended Hi-Fi Stereo Amplifier
I happen to have some NOS 6FY7, which are compactron tubes intended for the same purpose as the 6CY7. I looked at the tube data sheets and they don't seem to be very different from each other.
http://www.nj7p.org/Tubes/PDFs/Frank/093-GE/6CY7.pdf
http://www.nj7p.org/Tubes/PDFs/Frank/123-GE/6FY7.pdf
The main difference seems to be the plate dissipation for the output segment:
6CY7: 5.5 watts
6FY7: 7.0 watts
So other than the possibility of more output power, I don't seem to see much different. But I am a newbie. Am I missing something important here?
Thanks!
I recently saw a nice-looking schematic for a 6CY7, a Novar base tube intended for television use originally.
6CY7 Single-Ended Hi-Fi Stereo Amplifier
I happen to have some NOS 6FY7, which are compactron tubes intended for the same purpose as the 6CY7. I looked at the tube data sheets and they don't seem to be very different from each other.
http://www.nj7p.org/Tubes/PDFs/Frank/093-GE/6CY7.pdf
http://www.nj7p.org/Tubes/PDFs/Frank/123-GE/6FY7.pdf
The main difference seems to be the plate dissipation for the output segment:
6CY7: 5.5 watts
6FY7: 7.0 watts
So other than the possibility of more output power, I don't seem to see much different. But I am a newbie. Am I missing something important here?
Thanks!
6FY7 has slightly higher Gm, and the smaller triode has lower Mu than the 6CY7, along with lower RP as to be expected.
Not much difference though.
The tubes bias differently enough that I would not expect to be able to swap tubes without compensating somehow.
ie, they are similar but not interchangeable.
Not much difference though.
The tubes bias differently enough that I would not expect to be able to swap tubes without compensating somehow.
ie, they are similar but not interchangeable.
The 6FY7 (section 2) has about twice as much Mu variation as the 6CY7 (section 2). So more 2nd harmonic in single ended mode. However, that's across 70 mA variation of the 6FY7 versus 40 mA variation for the 6CY7. So 2nd harmonic would be similar for the same power output.
6FY7 is rated for a little less plate voltage (275 V versus 350 V) than the 6CY7.
6FM7 looks fairly similar to the 6FY7, except handles 550V plate V. Could use a higher primary Z OT (and higher B+) to get lower 2nd harmonic.
https://frank.pocnet.net/sheets/123/6/6FM7.pdf
https://frank.pocnet.net/sheets/123/6/6FY7.pdf
http://www.nj7p.org/Tubes/PDFs/Frank/093-GE/6CY7.pdf
6FY7 is rated for a little less plate voltage (275 V versus 350 V) than the 6CY7.
6FM7 looks fairly similar to the 6FY7, except handles 550V plate V. Could use a higher primary Z OT (and higher B+) to get lower 2nd harmonic.
https://frank.pocnet.net/sheets/123/6/6FM7.pdf
https://frank.pocnet.net/sheets/123/6/6FY7.pdf
http://www.nj7p.org/Tubes/PDFs/Frank/093-GE/6CY7.pdf
Thanks, everyone! I suspected that I'd have to fiddle with the cathode resistor on the input triode, am I correct? Is there any other way to change bias in the circuit I linked to?
As to plate voltage, I noticed that the person who created the schematic I linked to in my first post has a B+ of 220 volts, so I thought that this would be OK for either the 6FY7 or the original design, the 6CY7. Thoughts?
As to plate voltage, I noticed that the person who created the schematic I linked to in my first post has a B+ of 220 volts, so I thought that this would be OK for either the 6FY7 or the original design, the 6CY7. Thoughts?
Hello!
Did you come to an end with this project? Or, at least, did you imagine some schematic, or jus use(d) the one from the first post's link.
I am interested in building some small SE amplifier from triodes of that kind....in my area of interest are also: 8CS7/8CM7/6GF7/13DE7/6DR7. For 6GF7 I got a schematic, LT Spice simulated by it's designer, but I had to put in standby this project because of lack of the novar sockets...I will try something with 2 tubes in parallel per channel, because I have some good 2k5/8R transformers, designed for the 6GF7. My initial goal was a small working room amplifier with a good sound, but I will develop the schematic for using also with headphones...I have some 18 ohms planars waiting to get some tube amp sound.
Did you come to an end with this project? Or, at least, did you imagine some schematic, or jus use(d) the one from the first post's link.
I am interested in building some small SE amplifier from triodes of that kind....in my area of interest are also: 8CS7/8CM7/6GF7/13DE7/6DR7. For 6GF7 I got a schematic, LT Spice simulated by it's designer, but I had to put in standby this project because of lack of the novar sockets...I will try something with 2 tubes in parallel per channel, because I have some good 2k5/8R transformers, designed for the 6GF7. My initial goal was a small working room amplifier with a good sound, but I will develop the schematic for using also with headphones...I have some 18 ohms planars waiting to get some tube amp sound.