pedroskova said:
I'm slowly selling off all my old Radio Electonics, Radio-Crafts, Radio News (1940s, early 50s mostl -- scanning anything i find interesting), and i seem to recall a news article on such a beast
dave
And speaking of those old mags, and how little is new, just last night i ran across a schematic in one of them (RC Apr 47) for a fully differential 6SQ6>6L6 amp with optional inverse feedback that in recent threads has been termed partial feedback (ref Gary's PP 47 amp and Alex's RH amps)
Add some CCS to the cathodes & you have a modern amp (and maybe change the tubes in the front end to something most of us have actually heard off 🙂)
dave
Add some CCS to the cathodes & you have a modern amp (and maybe change the tubes in the front end to something most of us have actually heard off 🙂)
dave
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6SQ7 was a pretty common tube in old shortwave radios (anyone with a classic SX-28 knows 'em). The triode section is pretty much the same as a 12AX7.
fdegrove said:
Yeah. Though there are a few 14-year olds floating around on other parts around here, I think.
I'm 17, myself.
planet10 said:
My uncle - who is a ham and from whom I inherited this hobby - had a stash of these magazines - some as old as 1930's. I wonder if he still has them. They used to have a ton of small "one tube regenerative" shortwave sets. If you know of an issue featuring a really good one let me know I might be interested in buying that issue(s). Someday I wish to build one, after I am done restoring a 3 tube regenerative Eddystone that is. Yeah Ham radio is my first love.
percy said:
I don't know much about ham stuff... a scan of the table of contents goes up with each magazine. You can follow them as i get them up -- usually 2 a week.
http://www.planetsofta.com/booklist.html
If your uncle has those old mags, grab them (or at least ask him to will them to you). They have all sorts of interesting stuff in them.
dave
BTW: if anyone finds a December 1954 Radio Craft the kid on the cover (no kid now i'm sure) is looking to get a copy of that issue.
(Not 20 watts), and a combination of two existing approaches, but what - SE OTL? First one I believe about two years ago, by Rozenblit.
Ham was the stuff I loved.....G8xxx.
Convergence strikes again.......sim backgrounds.....glowing 807's 6146's great memories....keep it up........
richj (ex merchant N)
Convergence strikes again.......sim backgrounds.....glowing 807's 6146's great memories....keep it up........
richj (ex merchant N)
I have not been active in some time, as KI6BC. Have kept the license and many fond memories..... maybe someday.... Tube AM rig on 10 meters?
BTW, the Sept. 92 issue of QST has a high performance tube regen circuit! It uses two 6GH8's. It was such a good article on the type that I kept a copy of it.
Talking about david berning tube gear--i think his gear is outstanding.He was 1 that deffently did not go by the rules---he made his own rules with amp designs.
Right now i have a custom piece of gear that he had made for his self.It is his OTL circuit in a Luxman 5L15 lab
ref. series integrated.He told me someone had given him the luxman many years ago so he just took all the guts out and used the chassis.Everything is completly hand wired also with his tube phono built in.
It has no bass or treble--just straight through.This one produces 15wts a channel using 6L6--6v6--6k6--many different tubes---of course the watts change with each set of tubes. Being able to tube roll changes the flavour to a great degree.It's an auto baising circuit
It is a one of a kind amp.Sounds very clean and fast.
I'm somewhat new posting at the forum,but i have dropped by for years to read.
regards
Right now i have a custom piece of gear that he had made for his self.It is his OTL circuit in a Luxman 5L15 lab
ref. series integrated.He told me someone had given him the luxman many years ago so he just took all the guts out and used the chassis.Everything is completly hand wired also with his tube phono built in.
It has no bass or treble--just straight through.This one produces 15wts a channel using 6L6--6v6--6k6--many different tubes---of course the watts change with each set of tubes. Being able to tube roll changes the flavour to a great degree.It's an auto baising circuit
It is a one of a kind amp.Sounds very clean and fast.
I'm somewhat new posting at the forum,but i have dropped by for years to read.
regards
Au Contraire -
To the best of my knowledge, I've personally developed a couple unique tube circuit topologies never envisioned by another human being within the last 20 years - one of which I am currently using in a DC-coupled OTL amplifier almost every day, as in input to output gain at 0hz (no servos, no silicon devices in signal path, no significant dc offset/drift at output - you can see a photo of it in the photo section), and another which I used to prototype a transformerless input differential tube microphone preamp with 90+ db common mode rejection up to 1khz with a 3-4 db noise figure.
Myself, I'd resurrect a Stereo 70 with the diff cascode input, triode connected outputs and a passively stiffened ps using polypropylene caps for a low bucks outperformer.
What a coincidink! That's what I use in the differential cascode input of my dc coupled OTLs (this is *not* the unique circuit I referred to earlier).
As I mentioned previously, my OTL is wall to wall direct coupled and I've indeed 'lost' a couple speakers that it drove, but neither was the fault of the OTL - it was merely amplifying some .5 hz motorboating of a poorly conceived line level tube circuit that was driving it upstream. While I've had a few output tubes (6AS7G's) fail over the 17 year life of the amp, none have threatened the health of even the 4.5" woofers (1" vc, paper former) that it was driving & none have failed over the last five years.
Sounds like alot of fun--some nice stuff there.I wish i had what it takes to design gear,but i'm just one of the guys that keeps them in business.
thoriated said:
Hi -
Of course, I shouldn't have really posted that nobody has ever *thought* of the circuit topologies I implemented. I can't even say that what I've done was necessarily the best way to perform these functions. But what the hey. I'm too lazy/cheap to patent and sell them (assuming they would patent/sell)🙂
Btw, someone questioned whether cold cathode tubes would have any advantages for audio over solid state. I'm convinced they would, since vacuum tube interelectrode capacitances have negligible dielectric nonlinearities.
Of course, I shouldn't have really posted that nobody has ever *thought* of the circuit topologies I implemented. I can't even say that what I've done was necessarily the best way to perform these functions. But what the hey. I'm too lazy/cheap to patent and sell them (assuming they would patent/sell)🙂
Btw, someone questioned whether cold cathode tubes would have any advantages for audio over solid state. I'm convinced they would, since vacuum tube interelectrode capacitances have negligible dielectric nonlinearities.
percy said:
Hey! I am 30 untill next month! And only started to think about tubes 2 months ago. I hope I'll know as much as many of the boys here iun 20 years.
Cheers,
rada
Hi, having been weaned on tube circuits at the age of 10, I'm 52 this year and I'll never give up tubes where so many of my age cat have done so. A pity, because there's masses of talent out there.....I've come across so many people who have dumped their tube knowledge for silicon... although I know I'm well qualified to become of one of those old tube age tinkerers.
Naturally we develop our own circuits which become stalwarts........Keep burn'in.
richj
Naturally we develop our own circuits which become stalwarts........Keep burn'in.
richj
Hi,
I am 25, a junior electronics engineer. I am working on valves for 2 years. However, my job is not related to circuits. I hope the knowledge about valves wont be forgetten -I try to get more and more information, even from 50s books-, we should merge our current and slowly incresing knowledge with oldies.
MB
I am 25, a junior electronics engineer. I am working on valves for 2 years. However, my job is not related to circuits. I hope the knowledge about valves wont be forgetten -I try to get more and more information, even from 50s books-, we should merge our current and slowly incresing knowledge with oldies.
MB
Hi there.........alot have asked me about improving the paraphase phasesplitter often used in p-p amps. Chris Bonavolts' site mentions this configuration has low thd.....Not so...I find typ 3-5% dendending on tube condition. However it has a nice gain. The orig circuit cribbed from the GEC 88-50 watt amp is typical (Duncan amps) and provides good performance. Studying the circuit of lower tube (or follower) of the phasesplitter the junction of the 2x 1M dividers is often shown with a 1M to ground. Strictly one doesn't need this resistor as the 0V return goes through the other resistors. The result is a far better balanced HF response.
The circuit shown is the modified I use so much in 3 stage amps. With 20dB NFB one should expect an overall amp thd of around 0.2%. As the circuit operates at a fairly high impedance, the layout should be symmetrical to ensure min HF phaseshift.
richj
The circuit shown is the modified I use so much in 3 stage amps. With 20dB NFB one should expect an overall amp thd of around 0.2%. As the circuit operates at a fairly high impedance, the layout should be symmetrical to ensure min HF phaseshift.
richj
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