Lundahl LL2765 Headphone Amp Project

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nicoch58

nicoch58

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Joined 2004

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adamus

Member
Joined 2008
I am currently listening to a 6e6p-dr spud amp. Salas High voltage shunt supply, parafeed (obligato caps) and 10k - 300r - 32r. 180v on the plates, CCS loaded with ixtp08n100d2 cascode (really really simple little circuit), and diode bias.

I think it sounds amazing. Testing on the scope, its wonderful.

The 6e6p is a wonderful sounding tube, so full. I have a/b with the siemans d3a (180v, 22ma) and the 6e6p is my favourate, slightly full mids. The d3a is wonderful up top... but the 6e6p wins out. and its £3.
 
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jwags81818

Member
Joined 2005
Gungnir said:
OK, so put in the screen control resistors, which I stupidly forgot to install and nothing changed. I addes 100uf to the power supply and hum was cut in half!! So, going to add another choke and more capacitance, its weird because the hum sounds like 60hz not 120, but I dont have a scope to check. Amp does sound amazing! Will post pics when I get a chance. This sounds much much better than my OTL amp. Gain isnt super high, but it is high enough. I do have an issue with the volume pot not tracking equally during low volumes (its a cheapo pot) - it will get changed out in due time for something better.
Click to expand...

I had the same problem and it was a cheap volume pot. swapped it out and nomore hum.

Jeff
 
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pred

Member
Joined 2004
Hello all, I am toying with the idea to make a headphone amp. For the better sake of me looking at the LL2765 output connections, I can not imagine how to do it with one switch. This means that if I want to switch between two headphones with impedance of 50 or 600 ohms I would have to resolder the wiring, use some kind of ugly jumpers or some clever scheme with relays. Is there anyone who is seeing what I am not?

Thank you in advance.
 
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audiowize

Member
Joined 2005
Work backwards from the voltage your 600 ohm headphones are going to want, then make that available on a lower winding configuration on the OT. This will make the noise floor more reasonable as well. The transformer is rated to put out 13V on the secondary when configured as a 4.6K:32, do you have 600 ohm headphones that could make use of that much voltage? (that's 300mW into 600 Ohms, hot!)
 
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audiowize

Member
Joined 2005
Why do you want the lower ratios to begin with? If you want to accomplish that switching, you will need a substantial rotary switch. From all the tube headphone amps I have made over the years, I can tell you that the 5K:600 configuration is very likely to be a total waste of time.
 
nicoch58

nicoch58

Member
Joined 2004
pred said:
Hello all, I am toying with the idea to make a headphone amp. For the better sake of me looking at the LL2765 output connections, I can not imagine how to do it with one switch. This means that if I want to switch between two headphones with impedance of 50 or 600 ohms I would have to resolder the wiring, use some kind of ugly jumpers or some clever scheme with relays. Is there anyone who is seeing what I am not?

Thank you in advance.
Click to expand...
test the config as difference load 50/600 reflect difference load on plate of tube... B>C are quite easy
 
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