I bought an 807 tube at a flea market this weekend. It was love at first sight -- it's a beautiful tube.
On doing some research, I see the 807 is somewhere between a 6L6 and a 6L6GC, closer to the latter. Has anyone tried wiring up a converter socket (a la the converter for the "super" 6BG6 http://www.vacuumtubes.com/6BG6.html) so it can be used in an octal socket? Has anyone tried an 807 in a Simple SE?
The thought of being able to try NOS 807s for $10-15 each (rather than $50+ each for NOS EL-34s) in my Simple SE is very appealing.
On doing some research, I see the 807 is somewhere between a 6L6 and a 6L6GC, closer to the latter. Has anyone tried wiring up a converter socket (a la the converter for the "super" 6BG6 http://www.vacuumtubes.com/6BG6.html) so it can be used in an octal socket? Has anyone tried an 807 in a Simple SE?
The thought of being able to try NOS 807s for $10-15 each (rather than $50+ each for NOS EL-34s) in my Simple SE is very appealing.
No it is actually closer to the former. Most surplus 807's come from the WWII and post war era and they were made with 6L6GA or 6L6GB innards. The maximum screen grid voltage rating for an 807 is 300 volts. The maximum for most 6L6GA, or GB is between 325 and 360 volts depending on which book you read. Either way they don't work at 400 volts.
Most Simple SE's run the B+ well over 400 volts which will make life pretty unhappy for an 807. I played with some 807's and 1625's during the development of the Simple SE and found that most of them will not handle 435 volts at all. There are a few later vintage 807's that are probably made with 6L6GC innards and they will work well. These are fairly uncommon and hard to identify.
There have been a few Simple SE's built with lower voltage transformers that will work with the 6L6G. These will work with the 807 but the power output is a bit lower. I built one with a surplus transformer that has a B+ of 355 volts, but I am currently running trioded 6V6's in it. Two very nice sounding watts per channel.
Thank you, George.
That's too bad. They are very pretty tubes, and I am very happy with my Simple SE. I guess I'll have to come up with some other bottom-feeder way to play with NOS tubes.
Maybe I'll try out the super-6BG6 hack from vacuumtubes.com...
And thanks again for making it all possible for me and so many others!
Se807
Gordon Rankin wrote a DIY article about a SE807 amplifier in the one of the early Sound Practice issues. All of the Sound Practice issues are downloadable for free if you look hard enough. He even got Mike at Magnequest to wind the OPT, they are probably still available. Mike used the same size core as a Dynaco 451, it was huge to say the least.
Craig
Gordon Rankin wrote a DIY article about a SE807 amplifier in the one of the early Sound Practice issues. All of the Sound Practice issues are downloadable for free if you look hard enough. He even got Mike at Magnequest to wind the OPT, they are probably still available. Mike used the same size core as a Dynaco 451, it was huge to say the least.
Craig
Hi Shoog,
Can you describe more how you wired up your pentode driver for your RH807? A schematic will be nice.
Dog Fish What about this one? Claims about 18 watts.
http://sarris.info/main/807-single-ended-tube-amps
i was going to post this for critque perhaps some help to add another two 807's for about 35 watts
http://sarris.info/main/807-single-ended-tube-amps
i was going to post this for critque perhaps some help to add another two 807's for about 35 watts
This was one of my first projects and I built it as both a SEPP version and a choke loaded parafeed version. I didn't know much about the partial feedback principled at that time so never substituted a pentode for the front end.
Since then I have built multiple partial feedback amps the proper way.
It shouldn't be to difficult to sub in a pentode (the 6AU6 would be a good candidate) look at the datasheet and shoose an operating point which gives a similar plate voltage. A simple cap filtered resistor network should be adequate for the screen supply. Consider it a learning experience.
Someone else was considering this - try posting a new thread titled help building a pentode driven RH807 and i am cedrtain you will get all the help you need.
Shoog
Vol. 1, No. 2. I couldn't find it online, but figured out that you can buy a CD with all 16 issues of Sound Practices (from the former publisher, I assume) via eBay. Looks like a good investment.
Shoog, thanks for the recommendation. It looks like a nice simple design, very appealing.
If I didn't want to parallel it, do you think I could just drop the 2nd pair of tubes. But I guess that gets me back to the RH807 (since this derived from a doubled-up RH807).
I've got a couple old 6BG6-G's that I believe are 807 in a different format. Worked fine with my Simple SE, but I'd suggest a cathode bias resistor around 700ohm or higher. With 560ohm I got red plates fast.
It sounded good. Better than anything else I've tried, but I wouldn't expect the same result with the dissapation tuned down.
It sounded good. Better than anything else I've tried, but I wouldn't expect the same result with the dissapation tuned down.
Obviously, I can't hear a word you're saying. Are you trying to say that this picture isn't a recommended practice? Really?
(Ken-Rad and National Union 6L6 'metal' tubes being stress-tested. They've been playing for ~15 minutes. I can't see any red plates...)
Rick
Attachments
Well, the paint hasn't peeled off of them yet, but the insides are likely screaming in pain.
I was enrolled in a 3 year vocational electronics program in a public (poorly funded) high school. It was 1967 - 1970 so our "education" came from textbooks printed in the late 50's and our "lab equipment" consisted of scrap from Homstead Air Force base. So we had tubes, lots of tubes. It was in this class that I learned how to really "make em glow." We did have a bunch of Eico power supplies, and you can connect as many as 10 of them together to make an incredibly large amount of power! The most plentiful tube in our stock was the metal 6L6. There were hundreds of new in the box RCA's. I will bet that I killed at least 50 of them. Back then I successfully got over 100 watts out of a pair of these things. We didn't have distortion measuring equipment, and the old RCA oscilloscopes barely had traces, so the distortion was probably a zillion percent, but no one cared!
On a dare, I proved that you can indeed make the outer metal jacket glow red. It required some non standard connections though. It stunk up the entire lab.
Courtesy of Homestead AFB, we had several Stromberg Carlson PA amplifiers that used 4 6L6 type tubes to make about 100 watts (mono). I decided to hotrod one of those and use it for a guitar amp. Since they came without tubes, I used the metal 6L6's. I made two important discoveries in one day.
Discovery #1, pin 1 on a glass 6L6 type is not used. Some amps, including the Strombergs use pin 1 as a tie point. In this case it was connected to the screen supply. The metal 6L6 connects the outer shell to pin 1. The paint will peel after repeated overloads on some tubes exposing some bare metal.
Discovery #2, The foil cover on the second Steppenwolf album (CD's weren't invented yet) conducts electricity!
Shoog is right, the pentode for the RH design is a fine idea. The variable plate reisitance of the triode will deliver a signal-varied change in FB level. The near-constant( and high) plate Z of a pentode deals with this situation very well. The E-Linear simplification of the Schade-ing plate-to-grid also very much likes pentodes...
cheers,
Douglas
cheers,
Douglas
I have attached my holy grail http://www.retrovox.com.au/STC807.pdf (Second to my radiotron manual)!!
if only i was good at algebra!! Note the max plate voltages dependant on the configuration. The Sarris design i mentioned is configured in tetrode with 500v plates.
The THD is quite high. Triode ( lower plate voltage) or tetrode Class A push pull looks better
if only i was good at algebra!! Note the max plate voltages dependant on the configuration. The Sarris design i mentioned is configured in tetrode with 500v plates.
The THD is quite high. Triode ( lower plate voltage) or tetrode Class A push pull looks better
Obviously, I can't hear a word you're saying. Are you trying to say that this picture isn't a recommended practice? Really?
(Ken-Rad and National Union 6L6 'metal' tubes being stress-tested. They've been playing for ~15 minutes. I can't see any red plates...)
You can turn your PCB upside down and put tubes in a pot with an oil. You will be surprised!
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