• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

PP 807 stereo amp with 6F8G or JAN 7193 drivers/preamp

Jump to Latest
#22
Perhaps I was a bit harsh on the 807 earlier, I actually have at least two hifi amps and one guitar amp that uses them, plus two more in progress (the SE monoblocks I mentioned plus a PP pentode mono amp for subwoofer duty). I do like them, quite a lot even, but I like them more for their looks, price, availability and versatility than for any particular sonics.
 
#23
I run my triode 807 PP amp at 320v 40ma per tube into an 8k transformer for 6 glorious watts of class a power. Lots of people scoff at how low a power output that is for 807s but I don’t need much power and it really does sound amazing.

I’m currently using triode wired c3m as my driver. Wonderful sound. If you don’t want the weird filament voltage you can also use triode wired 6sj7 for a great sounding, cheap driver.
 
  • Like
Reactions: andyjevans and 6A3sUMMER
#24
Fuling said:
Perhaps I was a bit harsh on the 807 earlier, I actually have at least two hifi amps and one guitar amp that uses them, plus two more in progress (the SE monoblocks I mentioned plus a PP pentode mono amp for subwoofer duty). I do like them, quite a lot even, but I like them more for their looks, price, availability and versatility than for any particular sonics.
Click to expand...

Agian, fair enough. ;-) I find they have a bit of an old-fashioned tube "aura" that some will find appealing. During the pandemic when Russian tube prices went to the moon, I resorted to my 807s and find them different but perfectly acceptible. In SE amps I feel they're remarkably close to the 300B.
 
#26
krca45 said:
For building amp with 807 tubes You should look at STC 807 Application Note and 807 RCA 39 page datasheet + STC 807 43 page datsheet.

You can find them here :

https://frank.pocnet.net/
Click to expand...
Interesting. If fun through input 1 you’ll have a high power guitar amp and a hifi one if run through input two. Never seen that setup for a PI (I’m usually a paraphrase pi guy due to an obsession with 40-50’s guitar amps). What kind of PI is that and what’s the advantage with driving both gripds of the 807’s from two different cathodes?
 
#27
isaacc7 said:
I run my triode 807 PP amp at 320v 40ma per tube into an 8k transformer for 6 glorious watts of class a power. Lots of people scoff at how low a power output that is for 807s but I don’t need much power and it really does sound amazing.

I’m currently using triode wired c3m as my driver. Wonderful sound. If you don’t want the weird filament voltage you can also use triode wired 6sj7 for a great sounding, cheap driver.
Click to expand...
Would you care to share a schematic? I now that there is a difference in guitar/hifi world. In the guitar amp world everyone shares their schematics but some people seems to be a bit annoyed when asked for a HIFI schematic.
Another question. I do use the 6SJ7 as my main preamp tube and just now actually finished my take in an old Gibson Guitar amp made in only 73 copies. Added a spring reverb and used a 6SJ7 to drive the tank. Works really well. A very versatile tube.
Did use a 6SJ7 as a 6L6 driver in a class A guitar amp a couple of years ago. Sounded really good
 
Last edited:
#28
I actually had it built for me. Sorry, don't have a schematic. I gave the builder my ideas and he was mad enough to actually make it! Here's the maker announcing it with pictures: https://www.head-fi.org/threads/oblivion-ultrasonic-studios.902926/post-17216420

Don't think there is anything too fancy about the design. Got the impression that it was actually pretty basic. The tricky part was the power supply, switches for external or internal heater supplies, and setting up the ma meters for each tube. It is a balanced input only with a pair of twin triode inputs design. I believe they are directly coupled to the output tubes. 400v with a 110k anode resistors for the inputs. Variable, regulated (I believe he used the modern Maida boards from this site) B+ from 250v to 400v and fixed bias with adjustment pots for each tube. 8k Monolithic Magnetics output transformers, torrid power transformer. Sadly, the designer/builder has passed away so he won't care if I share the internal construction. Maybe you can tell what the circuit is by looking at it? I know just enough to be dangerous when it comes to amp designs so I won't venture any guesses beyond what I know.

DSC_0285.jpeg
 
  • Like
Reactions: Jerry garrcia
#29
Thanks. Since this is my first attempt at attacking a hifi amp (and mainly use old parts that I have at home) I think I’ll go with the Williamson W2m basic topology but with regulated screens, SS rectifier, massive choke I found in an abandoned chassis, dc filaments and have two PT’s I could use but one (the one I’d like to be used) need some mapping on the primary side since it has a complex input voltage regulation switch and it has just been cut out of the chassis. It is huge though and could probably provide enough current to the both channels. The other one I have and will work is better in a high powered guitar amp of some sort since it already in a circuit that only needs some minor modifications and a new OT for that use.
The problem now is to map the primary side of the PT and find the inductance of the choke. Unfortunately my LCR meter is broken.
IMG_0943.jpeg
image.jpg
 
#31
I was thinking about that but can’t be sure which is the 5V and which is the 6.3V. I do have a variac. Usually the dcr for a 230V input is 50-70 ohms and between each taps they are mostly 2-3 ohms in this one. This is a massive chunk of iron and all secondaries wires are thick solid core.
image.jpg
 
You must log in or register to reply here.
Top Bottom