6N7 - a fun tube!

[Opcom]

I made a 6N7 Jones oscillator transmitter a couple of years ago and it is a slick little unit.

Mike WU2D

That is the very circuit I was referring to in a previous comment.

Great minds having one thought.....

73DG

I can see who the real leaders of this operation are. That transmitter sort of has SBE written on it.. granted the crystal may not pull much.. How is the keying profile on CW? My friend Dennis W5FRS says that just a tiny amount of chirp sometimes makes it easier to copy.

[W7TFO]

The whole story is in all the Jones handbooks from the mid-30's.

Frank J. used it as the basis of many VFO designs before ECO circuits came into vogue.

73DG

[Opcom]

There are some Hammond interstage transformers that might work OK with the 6N7 as a driver to another tube (p-p class A). Some specify 40-60mA in the primary, to drive the next stage grids. The only gripe with Hammond is the transformers spec from 150Hz up ad its hard to say whether that is with all that current flowing or not. So could be good or bad. I'm guessing that at 0.2W from an interstage application the frequency response will be better.

124A   TRANSFORMER TUBE DRIVER CLASSIC   124   
Hammond Manufacturing   
Tube Driver
150Hz - 15kHz
5 Watts
45mA   10K Primary
90KCT Secondary   
insertion loss ±1dB

[The Slab Bacon]

they sound quite good. I have a 124D in my 4X1 rig, no one ever complains about the audio. I think the usable response goes well below 150 cycles. Don't forget that you would be using it for voice and not music. They are a pretty good little tranny for the price.

[Opcom]

Can you say more about the application, what is the driver and what is being driven? That will help me.

[The Slab Bacon]

Can you say more about the application, what is the driver and what is being driven? That will help me.

Patrick,
           If you are asking me, I have it turned around for a 1.5:1 stepdown with a 12AU7 with both sections in parallel (class-A) driving a pair of P/P 2E26 AB2 grids.

I needed a modulator capable of around 20w and I didn't want to waste good audio tubes when I literally had a 5-gal bucket full of 2E26s. With close to 500v on the plates in AB2 those littls mothers can make some serious audio power for their size. (Like capable of in excess of 50w) Which is transformer coupled to the screen of the 4X1 with an ARC-5 mod transformer. (No stinkin controlled carrier)

I originally used one of the standard 3:1 step up drivers and it just didn't have enough BAs to push the modders into the grid current range. This made the audio kinda thin and crappy. When I changed it to the step-down configuration, the audio just came to life. I can make 125% without pushing it hard now. I just had to be able to push the little modders into grid current.

Since this skizmatic was drawn I have increased some of the parameters for dramatically improved performance.

[W7TFO]

Designer snippet:

2 X 2E26 = 1 X 815 (the R2D2 tube).

73DG

[Opcom]

Can you say more about the application, what is the driver and what is being driven? That will help me.

Patrick,
           If you are asking me, I have it turned around for a 1.5:1 stepdown with a 12AU7 with both sections in parallel (class-A) driving a pair of P/P 2E26 AB2 grids.

I needed a modulator capable of around 20w and I didn't want to waste good audio tubes when I literally had a 5-gal bucket full of 2E26s. With close to 500v on the plates in AB2 those littls mothers can make some serious audio power for their size. (Like capable of in excess of 50w) Which is transformer coupled to the screen of the 4X1 with an ARC-5 mod transformer. (No stinkin controlled carrier)

I originally used one of the standard 3:1 step up drivers and it just didn't have enough BAs to push the modders into the grid current range. This made the audio kinda thin and crappy. When I changed it to the step-down configuration, the audio just came to life. I can make 125% without pushing it hard now. I just had to be able to push the little modders into grid current.

Since this skizmatic was drawn I have increased some of the parameters for dramatically improved performance.

I was not originally but I am glad to have as many interesting answers as there are!  Turning the transformer around was something i was going to bring up as drivers are sometimes step down, and the Hammond transformers are listed as step up.

p.s. the 2E26 is a good audio tube according to its success in your application!


It is good news also about the Hammond frequency response sounding good because the alternative is Lundahl and very expensive for that response and quality level. unfortunately there, the spec sheets he has are also a bit confusing to me.

Designer snippet:

2 X 2E26 = 1 X 815 (the R2D2 tube).

73DG

The "evil robot" tube..

[W7TFO]

I built a stero hi-fi power amp with a pair of 815's years (14?) ago, sounded pretty good, didn't get hot, and used Hammond iron all the way thru.  It was biased for true AB2 operation.

I had a set of OPT's wound by them with 10% voltage tertiary windings and fed that back into the driver trans (One of the potted broadcast jobs).  The interstage tube was of all things a 6N7G, paralled P+G.

Made way over the 35WPC my target was in the design, looked way cool with all those plate caps sticking up on those little squatty tubes.

I drove a pair of Altec A7's out in the garage, and at the time I lived in a subdivision so running it hard for any length of time got the neighbors riled up.
 
It disintegrated back into the parts bins, but I'm sure all that stuff is still here somewhere.

73DG

[WU2D]

The  Gimmicks came from somewhere - probably an old article. I will have to look to see if I actually installed them. The Paraset 6V6 oscillator uses a feedback gimmick like that, plate to grid.

[The Slab Bacon]

Designer snippet:
2 X 2E26 = 1 X 815 (the R2D2 tube).
73DG

Believe it or not, I was thinking about using an 815 just to be different. Like you said it is a pair of 2E26s in one bottle. But................... 11 years ago when I built that thing I had 2 815s on the shelf and a 5-gal bucket of 2E26s. Not much thought process there........

[The Slab Bacon]

<snip> ''I was not originally but I am glad to have as many interesting answers as there are!  Turning the transformer around was something i was going to bring up as drivers are sometimes step down, and the Hammond transformers are listed as step up." <snip>

Patrick, the 124D that I have on the shelf was listed to work either way. IIRC, it had the same current handling capacity on both windings. So by chosing the right combination of winding and whether or not to use the center tap and half of a winding for the single ended side, it gives you a lot of flexibility in how you use it.

IIRC, the older AES catalogs from a few years back actually listed it an useable either way. That is where I got the idea from.

[Opcom]

Ok, been a while but this is the right place:

Summary Line up of zero bias common cathode dual power Triodes.

56 -  Medium 7 pin base (use same socket as 1625), 2.5V heater.  Pd 3W per unit or 5.5W.
6A6 - Medium 7 pin base (use same socket as 1625), 6.3V heater. Pd 3W per unit or 5.5W.
6N7 - Octal base, 6.3V heater, Pd 3W per unit or 5.5W.
6Z7 - Octal base, 6.3V, 180V B+, 8W Pd.
1635 - Octal base, 6.3V, 10W into 12K p-p, Pd 3W per unit or 5.5W. Curves go to 500V.
5608 - Medium 7 pin base (use same socket as 1625), 2.5V heater.  Pd 3W per unit or 5.5W. Reliability version.

[VE3LYX]

That style of tube can be a lot of fun however real men use 01As and 45s
don

[W9GT]

Frank Jones used the 6A6 in his famous (1936) PP xtal oscillator circuit....makes a great little breadboard xmtr for playing with CW and QRP.  I have made many contacts with this rig and variations thereof.  I even used a pair of 955 acorn tubes and a pair of 50L6s in the circuit. 6N7 will work fine, as well.

73,  Jack, W9GT

[N2DTS]

Needs varnish or at least a nice stain!
No worries about a fire?