• 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.

quicky rebuild 6v6 to 807

Status
Not open for further replies.
Jump to Latest
M

mrneedle

Member
Joined 2011
#1
Hi

I have everything ready to build 2x 6v6 pp mono blocks.

but my better half likes the 807 coke bottle shaped tubes better than the newer 6v6.. i've searched for 6v6 coke bottle shaped tubes but a matched quad is pretty expensive...

I was planning on using the dynaco schematic found at diyaudioprojects

while traveling home just now, i was searching ebay and saw a nice matched quad of 807's for a very good price.

is it worth the effort, or even possible to use the 807 instead of the 6v6?
 
#5
that's 2 quick responses 🙂

well for her it's all about the looks, but seems (as I already thought ) I should stick to the 6v6 tubes then.

an adapter is a nice idea though, and power is not an issue, any clues on how to?

thanks for your replies
 
#7
heater current wouldn't be a problem. the power transformers have higher specs than needed already.

I had a quick look at the datasheet 807 / 6v6gt

seems the 807 wants 0.9 amps and the 6v6gt wants 0.45 amps

so that would be 1.8 amps + a 6sl7 0.3amps = 2.1 amps

and the PT gives me 3 amps, so that would be fine...
 
#12
mrneedle said:
Hi

I have everything ready to build 2x 6v6 pp mono blocks.

but my better half likes the 807 coke bottle shaped tubes better than the newer 6v6.. i've searched for 6v6 coke bottle shaped tubes but a matched quad is pretty expensive...

I was planning on using the dynaco schematic found at diyaudioprojects

while traveling home just now, i was searching ebay and saw a nice matched quad of 807's for a very good price.

is it worth the effort, or even possible to use the 807 instead of the 6v6?
Click to expand...

I have some good tested used ST-shape 6V6G if you are interested. PM me.

Gary
 
#14
Wavebourn said:
Yes, it is possible to use 807 instead of 6V6, but 6V6 tubes are more linear.
Click to expand...

No they are not. Look at the spec sheets. The minimum THD spec for PP 6V6s is 3.5%, and 1.8% for the 807.

This is one of those cases of measure better, sound worse. The difference is in the harmonic "personality" of the types. Running open loop, PP 807s make less distortion, but more of what remains is H5 and higher. When doing the Twin-T test on an open loop 807 design, the residual was damn near a sawtooth. It definitely showed up in the sonic performance where certain program material was all but unlistenable, due to something hard to describe that was hiding behind the music that was very hard to stand for very long.

With 6V6s, (and 6BQ6s, and the rest of the 6V6-oids) the residual from the Twin-T test is nearly a pure sine at three times the test frequency. It's almost all H3. This tends towards an overly "edgy", "aggressive" sound when running open loop. Even though the sum total of the distortion is higher, it's not so hideous to listen to. The distortion doesn't become truly nasty until you're running nearly to the clipping point.

This has already been taken into account, and in his "white paper", O. H. Schade recommended feeding back 10% of the plate voltage to the grid with parallel local NFB to help tame the 807's harmonic nastiness. With 6V6's, all you really need is enough gNFB to take the edge off. 807s need the extra help to attain sonic excellence, but once you've added the lNFB, they do sound great.
 
Status
Not open for further replies.
Top Bottom