Hi all!
This is one of my last valve project. An OTL headphone amp with a 6N1P in ground cathode for input stage and a 6N6P in SRPP for the output stage.
I've found that the best working point for this tubes are 10 ma for the 6N1P and 22 ma for the 6N6P. The circuit is a classic and in the next post I'll send to you. With my Sennheiser HD590 and AKG K271 Mk2 works really fine, what a sound!!! I have a slight and impercectible hum but I soon resolve it with a choke in the PSU, now I have a CRC cell but it's bettere a CLC; next step.
The case is a bit ugly but I have used some recycled waste from my factory (rivets... like a Douglas DC3... could be a new trend???) 🙂
I bought a lot of russian valves on ebay, different factories and years and works really fine, great sound and incredible price, I'm working with them in my next project: a RIAA-LINE preamplifier.
ciao
This is one of my last valve project. An OTL headphone amp with a 6N1P in ground cathode for input stage and a 6N6P in SRPP for the output stage.
I've found that the best working point for this tubes are 10 ma for the 6N1P and 22 ma for the 6N6P. The circuit is a classic and in the next post I'll send to you. With my Sennheiser HD590 and AKG K271 Mk2 works really fine, what a sound!!! I have a slight and impercectible hum but I soon resolve it with a choke in the PSU, now I have a CRC cell but it's bettere a CLC; next step.
The case is a bit ugly but I have used some recycled waste from my factory (rivets... like a Douglas DC3... could be a new trend???) 🙂
I bought a lot of russian valves on ebay, different factories and years and works really fine, great sound and incredible price, I'm working with them in my next project: a RIAA-LINE preamplifier.
ciao
Attachments
That's quite a nice build, and I do like the rivets... 🙂
Will you post a schematic (since I have made a schematic for 6N23P-6N6P myself 😉?
Just being curious...
Will you post a schematic (since I have made a schematic for 6N23P-6N6P myself 😉?
Just being curious...
Hello
I wish to build this amplifier,
But I have a helmet Grado sr60 impedance 32 ohms.
Work you he(it) with no problem at all or is it necessary to make modifications?
Cordially
I wish to build this amplifier,
But I have a helmet Grado sr60 impedance 32 ohms.
Work you he(it) with no problem at all or is it necessary to make modifications?
Cordially
Hello
I wish to build this amplifier,
But I have a helmet Grado sr60 impedance 32 ohms.
Work you he(it) with no problem at all or is it necessary to make modifications?
Cordially
I wish to build this amplifier,
But I have a helmet Grado sr60 impedance 32 ohms.
Work you he(it) with no problem at all or is it necessary to make modifications?
Cordially
Would it give even lower output impedance if both 6N6P halves were connected in parallel and as a cathode follower instead of SRPP ?
There is also quite high overall gain. Is that much really required ?
There is also quite high overall gain. Is that much really required ?
Very nice, how much did the amp cost you to build? How does it sound?
If you have the power supply schematics, please post it as well.
If you have the power supply schematics, please post it as well.
Capacitors K42 is not the best, K40 would be better.
Assessing the impact of coupling capacitors in the audio amplifier.
http://www.magictubes.ru/ves/kondens.htm
Assessing the impact of coupling capacitors in the audio amplifier.
http://www.magictubes.ru/ves/kondens.htm
Is there any danger in using this kind of headphone amplifier? I mean ... you could have 300V near your brain in case something goes wrong... I'm asking because I talked with a friend about such an amplifier and he was a little bit reserved about it ...
I have just got me some Sennheiser HD650, so I think I will try this out.
But why the cap on the input? And the 1meg in paralell with the pot?
Theo
This circuit is very similar to P. Milletts SRPP design which uses the ECC99. I think this design just uses the Russian equivalent tube.
The P. Millett design runs the tubes at 20mA with a 300 ohm Rk. This design has 150 ohms Rk so the cathode current will be even higher. I am concerned this may exceed the dissipation spec of the tubes used.
The P. Pillet design uses an output transformer to better match the output to the headphones impedance. This circuit has no output transformer so its drive capabilities will be severely limited except for high impedance headphones.
Cheers
Ian
The P. Millett design runs the tubes at 20mA with a 300 ohm Rk. This design has 150 ohms Rk so the cathode current will be even higher. I am concerned this may exceed the dissipation spec of the tubes used.
The P. Pillet design uses an output transformer to better match the output to the headphones impedance. This circuit has no output transformer so its drive capabilities will be severely limited except for high impedance headphones.
Cheers
Ian
Thank'd for the answar Ian.
No problem with running the tube to hot. I will make it inside the safety limit. 6n6p runs fine with 100-150V@20-25mA.
Another matter is the drive capability for my 300 OHM cans. I do not know how to calculate if the curcuit is up to it. Any help is most welcomed.
But back to my Q. Why the 220nF cap on the input, and the 1Meg?
Theo
No problem with running the tube to hot. I will make it inside the safety limit. 6n6p runs fine with 100-150V@20-25mA.
Another matter is the drive capability for my 300 OHM cans. I do not know how to calculate if the curcuit is up to it. Any help is most welcomed.
But back to my Q. Why the 220nF cap on the input, and the 1Meg?
Theo
The 1Meg simply provides a dc path to ground for the grid of the input tube and defines the input impedance. The 220nF provides dc blocking as some AtoD converters are known to have dc on their outputs.
The -3dB point for 220nF and 1Meg is 0.723Hz - should be fine.
Cheers
Ian
The -3dB point for 220nF and 1Meg is 0.723Hz - should be fine.
Cheers
Ian
Drive capability can be calculated from the phones spec. The HD650 are quoted at 102dB SPL for 1V rms input. That's pretty loud but to allow for transient I normally aim for a peak drive capability to 117dB SPL which implies we need another 15ddB of signal or about 5.6V rms. Into 300 ohms, 5.6V rms give a peak current of 26mA. If you run the tubes at 25mA quiescent this is not going to happen.
I have run a simulation of an ECC99 SRPP running at 220V with the Rk values shown in the schematic and this predicts a plate current of 17mA and a plate dissipation of just under 2W a plate which should be OK.
At 3V rms into 300 ohms the simulation predicts a THD of about 0.8%. This should give a peak sound level of 112dB SPL.
At 1V rms the distortion falls to about 0.25%.
To be honest, you don't really need the first tube as the SRPP on its own will have about 20dB gain.
Cheers
Ian
I have run a simulation of an ECC99 SRPP running at 220V with the Rk values shown in the schematic and this predicts a plate current of 17mA and a plate dissipation of just under 2W a plate which should be OK.
At 3V rms into 300 ohms the simulation predicts a THD of about 0.8%. This should give a peak sound level of 112dB SPL.
At 1V rms the distortion falls to about 0.25%.
To be honest, you don't really need the first tube as the SRPP on its own will have about 20dB gain.
Cheers
Ian
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