Hello,
I'm on the search for suitable tubes for a simple parafeed headphones amp.
What I've got:
- A 270Vdc/60ma regulated B+
- A 12.6Vdc or 15Vdc @1A supply.
- A pair of 10K-7K/300-32 transformers.
- A pair of ss CCS or gyrator, so anode voltage will be at about 200V.
I'm considering tubes with µ in between 25 and 40, lowish rp, medium power dissipation (at least 3w, more is better).
For now, I've been looking at ecl84/pcl84 (pentode section, triode strapped), at the 6ag7/6P9 (again, triode strapped), the el83/pl83 and the 6922 (sections in //).
Any obvious or less obvious tube I'm missing ?
I'm on the search for suitable tubes for a simple parafeed headphones amp.
What I've got:
- A 270Vdc/60ma regulated B+
- A 12.6Vdc or 15Vdc @1A supply.
- A pair of 10K-7K/300-32 transformers.
- A pair of ss CCS or gyrator, so anode voltage will be at about 200V.
I'm considering tubes with µ in between 25 and 40, lowish rp, medium power dissipation (at least 3w, more is better).
For now, I've been looking at ecl84/pcl84 (pentode section, triode strapped), at the 6ag7/6P9 (again, triode strapped), the el83/pl83 and the 6922 (sections in //).
Any obvious or less obvious tube I'm missing ?
Use ECL84 triode as a voltage amplifier and pentode as cathode follower with high current.
Other good tubes are EL86 and EL36 etc. (including russian equivalents).
The principle I mean is something like this:
Other good tubes are EL86 and EL36 etc. (including russian equivalents).
The principle I mean is something like this:
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I've built a parafeed headphone amp like this and it works well for 150 ohm headphones but if you want to drive 32 ohm ones, then I agree with artosalo; cathode follower or source follower as output stage. Using ccs as load for both stages should optimise performance.
Take the output from the "mu out" of the ccs/gyrator, and you'll have a lot of driving power. I'm building a line stage that's basically the same layout, and accidentally found out, headphones sound great when I connect the parafeed cap to the mu out.
With a mu of 2? Looks to me he wants a single gain stage, so this probably wouldn't suffice.
How about 6H30, E182CC, 6N6P, ECC99, or 5687?
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I have built a parafeed spud. It takes E186F/ D3a / 6J9P and equivalents, *triode strapped*. In my opinion, these space-age, high transconductance pentodes sound much better than the usual double triodes.
E55L makes a great Spud amp at about 2W output. Single gainstage.
The only issue been the OT which should be in the range 2-4K rather than 7-10K.
Shoog
The only issue been the OT which should be in the range 2-4K rather than 7-10K.
Shoog
Thanks needtubes ;-) I think the 6N6P will be my backup solution. I'm going to try the 6E5P first.
Btw, one has to be careful connecting the parafeed to the µ-follower point of a gyrator;
+: you indeed get a very low output impedance
-: to avoid a large low frequency bump, you'll end up needing a much bigger parafeed cap.
+: the tube is operating at almost constant current.
-: the power supply is not seeing a constant load anymore
Btw, one has to be careful connecting the parafeed to the µ-follower point of a gyrator;
+: you indeed get a very low output impedance
-: to avoid a large low frequency bump, you'll end up needing a much bigger parafeed cap.
+: the tube is operating at almost constant current.
-: the power supply is not seeing a constant load anymore
Thanks Shoog, Vincent77, that's more in line with what I'm looking for.
Out of curiosity: did you compare the 6J9P to the more expensive western tubes ? How did it fare ?
Out of curiosity: did you compare the 6J9P to the more expensive western tubes ? How did it fare ?
For me, the E186F is the best of the bunch. Russian 6J9P, 6J11P are OK, and I didn't like 6J52P.
Resurrecting this old thread as this amp is finished, finally using a pair of 6E5P.
The schematic is very simple, similar to the "torpedo" (it's using the same output transformers, 10k to 300-32 from edcor). Besides the different operating points, the only differences are a RC damping network to tame the rising very low frequencies and a lm2596 as regulator for the heaters.
It sounds good to me. The external transformer helps with noise.
Some (bad) pics attached.
The schematic is very simple, similar to the "torpedo" (it's using the same output transformers, 10k to 300-32 from edcor). Besides the different operating points, the only differences are a RC damping network to tame the rising very low frequencies and a lm2596 as regulator for the heaters.
It sounds good to me. The external transformer helps with noise.
Some (bad) pics attached.
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