• 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.

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Colt45

Member
Joined 2002
heres my next idea.

OPTs et al are on the way, but i went to test my 807s, and one is shorted :(

main amp (each channel)
I wrote 12AX7 but meant 12AU7, oops..

An externally hosted image should be here but it was not working when we last tested it.


power supply.

An externally hosted image should be here but it was not working when we last tested it.


eye tube VU deal.
(need to change this some.. that voltage divider won't work.. too high impedance. I suppose ill just jack up the plate resistors some, on the eye..) :h_ache:

An externally hosted image should be here but it was not working when we last tested it.


thoughts, etc? :scratch2:
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
SOME THOUGHTS.

Hi,

First of all I'd recommend a 6SN7 iso the 12AU7.
Never liked the sound of the 12AU7.
Or consider a 12BH7A or 12FQ7/12CGFA.

You can also safely ommit the input cap.

Also I would up the filter cap after the choke by putting a # of caps in //.
Up to 500 microF wont do any harm.

Seems you forgot the heaters too.

Cheers,;)
 
C

Colt45

Member
Joined 2002
Yeah, I might try something else for gain.

just kickin' the idea around for now. I have a few 6CG7's, might try them. no 6SN7s though, but they're the same tube, up to a point..

I'll probably throw on volume control when I actually make it, but im usually too lazy to draw it in ;)
 
Brett

Brett

Member
Joined 2002
Re: SOME THOUGHTS.

fdegrove said:
Hi,

First of all I'd recommend a 6SN7 iso the 12AU7.
Never liked the sound of the 12AU7.
Or consider a 12BH7A or 12FQ7/12CGFA.
Click to expand...
Yep. The more amps I build, the more I find the driver is a lerger determinant of the sound. You could also try ECC99, 6H30 or 6N1Ps (if you want to try some of the 6N1Ps, send me your address and I'll send you a couple)

I like 807s, a very nce underrated tube. Someone said recently (perhaps Grand Poohbah dave) that he thought their general lack of popularity was due to topcaps. I'd agree, but that's good, because I like topcaps.
You can also safely ommit the input cap.

Also I would up the filter cap after the choke by putting a # of caps in //.
Up to 500 microF wont do any harm.Seems you forgot the heaters too.
Click to expand...
Ditch the input cap.
Filter capacitance is always nice, providing it's as good as some of the modest caps, so I prefer to // lots of smaller ones.
AC heaters will be fine, and less hassle. Bias the heaters about 40V above ground.
 
C

Colt45

Member
Joined 2002
Thanks guys.

I think i'll try it full blow pentode mode at first, maybe make it switchable to triode..

807 has another brother (other than 6L6 et al). 6BG6G is a octal based 807 with none of that shielding stuff under the mica on the bottom.. slightly less glorious job as a TV sweep.

I think theres something kind of neat about the 'ol 5pin socket though ;)
 
SY

SY

Ex-Moderator
Joined 2002
SYclotron.com
807 is what you use if you're not man enough for a 1625.

They saw service in civilian apps, too- I remember using them in a HF transmitter I built maybe 35 years ago. Ran them waaaaay over their ratings for CW service. If you kept the key down too long, the plates would go off like a flashbulb. The transmitter would only work if you kept your speed above 20 wpm.

But, yeah, they're basically just 6L6s.
 
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