Rongon:
Your design is spot on. I have used a similar approach in an old Scott 299. Negative power on the long tail like you have - but used 12AX7s instead. Zero feedback as well. Not sure you need the output to go to the grid if the 6SN7. Try without feedback and instead tie the grid of the second half of the 6SN7 to ground. Should have very nice and open sound. What is cool about this design is that it is so simple.
One change I would do is to use smaller caps on your RC coupling to the EL34s. .22uF and 220K will do nicely and likely sound better. Also: you do not need to run the 6SN7s at such high bias. 7V is a bit too high IMHO. I would drop that to around 2.5V. But overall great, simple design. Should sound good with quality parts. Mills WW and teflon caps is a nice modern mix
.
D.
Your design is spot on. I have used a similar approach in an old Scott 299. Negative power on the long tail like you have - but used 12AX7s instead. Zero feedback as well. Not sure you need the output to go to the grid if the 6SN7. Try without feedback and instead tie the grid of the second half of the 6SN7 to ground. Should have very nice and open sound. What is cool about this design is that it is so simple.
One change I would do is to use smaller caps on your RC coupling to the EL34s. .22uF and 220K will do nicely and likely sound better. Also: you do not need to run the 6SN7s at such high bias. 7V is a bit too high IMHO. I would drop that to around 2.5V. But overall great, simple design. Should sound good with quality parts. Mills WW and teflon caps is a nice modern mix
.D.
I have worked with 6SN7 tubes with beautiful results using the old Sylvania blackplates 6SN7GTB's.
These are my favorites with fantastic sound.
A well engineered preamp using 6SN7's will lead to beautiful results with relatively low distortion. I am using un-bypassed cathode resistor since the global negative feedback ties right at the cathode.
After building an amplifier, I always go back and check my load lines using the actual measurements multimeter with the amp at idle. This is good practice because you may find that with the specific tubes, your load lines may be way off with what you originally thought, especially with a "bad" tube which has happened to me more than once.
I noticed this problem with many of the new Russian tubes. It works and will perform with no obvious signs of failure but the cathode current will fall off very quickly shortly after initial running of the tube.
As mentioned above, I find that running the idle current higher leads to great soundstage. I run my first stage at 3.5mA idle.
These are my favorites with fantastic sound.
A well engineered preamp using 6SN7's will lead to beautiful results with relatively low distortion. I am using un-bypassed cathode resistor since the global negative feedback ties right at the cathode.
After building an amplifier, I always go back and check my load lines using the actual measurements multimeter with the amp at idle. This is good practice because you may find that with the specific tubes, your load lines may be way off with what you originally thought, especially with a "bad" tube which has happened to me more than once.
I noticed this problem with many of the new Russian tubes. It works and will perform with no obvious signs of failure but the cathode current will fall off very quickly shortly after initial running of the tube.
As mentioned above, I find that running the idle current higher leads to great soundstage. I run my first stage at 3.5mA idle.
Not on the Chinese versions... Rusky 4 Hole plate sound the best then the triple mica RCA 5692 then the old stock Sylvania GTB's green and yellow labels. Tung-sol old stock oval top plate clear tops are WAY too pricey. I've got a few and I'm sticking to the above. Even the GTBs are getting pricey (for good reason), they used to be under the radar.
Cheers,
Bob
I use nos for critical parts outside feedback. If the 6sn7 is in cathode follower then the new tung sols are just as good or better by one db less distortion. As for betta followers and srpp the section matching is super important , N.o.s tubes excelled in that area by 6 to 8 db better. I never bought new tubes with matched sections in that tube.
Did someone experienced new stocks matched sections for sharing comparisons?
Did someone experienced new stocks matched sections for sharing comparisons?
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