Hi!
I am listening now to stereo amp with... 2.5W per channel! 😱
Sounds very clean. Stereo imaging is perfect. Even depth is heard well.
Output stage uses 4P1L DH tube, triode connected. Input stage uses triode connected 6J5P tube, loaded on gyrator for minimum tube distortions, green LED in cathode. It is coupled to 4P1L grid through cathode follower made on 6N16B with paralleled triodes, dynamically loaded on current source. It is not a "power drive", it is the way to minimize distortions caused by non-linear grid current, especially when interstage capacitor is used.
The whole thingy is powered from oversized PS with stabilized voltages for -56, +120, +240 and floating 6.3V.
Enjoy!
I am listening now to stereo amp with... 2.5W per channel! 😱
Sounds very clean. Stereo imaging is perfect. Even depth is heard well.
Output stage uses 4P1L DH tube, triode connected. Input stage uses triode connected 6J5P tube, loaded on gyrator for minimum tube distortions, green LED in cathode. It is coupled to 4P1L grid through cathode follower made on 6N16B with paralleled triodes, dynamically loaded on current source. It is not a "power drive", it is the way to minimize distortions caused by non-linear grid current, especially when interstage capacitor is used.
The whole thingy is powered from oversized PS with stabilized voltages for -56, +120, +240 and floating 6.3V.
Enjoy!
Attachments
Looks very nice!
But I don't see the paralelled triodes in the schematic? (Probably because it's still early over here..)
But I don't see the paralelled triodes in the schematic? (Probably because it's still early over here..)
Congratulations to the scheme!
I would like to ask, how is the tension on the resistor R13 / 10 Ohm /
Thanks.
I would like to ask, how is the tension on the resistor R13 / 10 Ohm /
Thanks.
They are shorted out. I remove 4P1L in one channel and unshort resistor in another channel to measure and set 230 milivolt on it.
You can draw it, if you want. 😉
Interesting this.,.... I have a few of those valves here. Might be one to consider for a future project maybe.
Fran
Fran
It is gorgeous tube when triode connected. Sounds better than 2A3.
Attachments
Last edited:
Never heard of that tube, or direct heated penthodes altogether. Seems an interesting little bugger, thanks for bringing it to my attention 😉
Interesting looking little creature. But why the Gyrator on the first stages anode? Wouldn't a simple CCS have sufficed? What are the benefits of this?
Kind of a similar question - could the front end of this be simplified somewhat to run a single b+ ?
Fran
Fran
Hi Wavebourn,
The oversized PS is for minimising the ripple due to SE topology,right?
Any other reasons?
I use the same technik for better or worse, but I was searching for some more info on this.
Alkis
The oversized PS is for minimising the ripple due to SE topology,right?
Any other reasons?
I use the same technik for better or worse, but I was searching for some more info on this.
Alkis
Yes, also better stability on transients. The purpose of this toy was to explore all that is possible to get from this wonderful 4P1L tube.
Also, it would be theoretically better to power filament from 2.1V stabilizer connecting halves of filament in parallel.
Yes, you can use an interstage transformer and more powerful driver, like one more 4P1L. But such simplification would be more expensive.
Gyrator is actually a CCS with servo. In reality exact stable current is less significant than high dynamic resistance and stable anode voltage. When swapping tubes, and when they age, no need to adjust current supplied by CCS: Gyrator adjusts it for you.
I measured output power: it is 2.48W on 8 Ohm dummy load, 100 Hz. Tiny 6N16B-V performs well: 1'st grid peaks on 4P1L are +12V, while available negative bias supply limits the power.
Telefunken designed again, for their German army... Captured from enemy by Red Army, then used for themselves in a bit different envelope. The story is similar to GU-50. Also, one more remarkable tube with similar fortune is 12P17L. Almost like 4P1L, but with more convenient 12.6V indirectly-heated cathode, and fully enclosed in aluminium shield.