[ARC5] 6AC7 and 6AB7

[Kenneth G. Gordon]

On 5 Feb 2013 at 20:46, Geoff wrote:

> Tube collectors may be after the 1851 if enough of them are around. I just 
> like octal tubes, especially metal ones.

So do I.

> Might make a good swap for a noisy 
> 6K7 followed by a 6L7/6K8 but you need an old tube socket pin as a grid cap. 
> Then just use it on 10-15M where the AVC action wont be hurt too much on a 
> quiet band and images not a bother.

I had thought about using one in a BC-779...

> Yes, the 6CL6 is the 6AG7 equivalent, I also have a bunch but not 50!
> 
> The 12BY7 (also developed for TV) was used in all the Kenwood hybrids as a 
> driver and also several other rigs, also the HFO in the SX-101A.

The 12BY7 was both the oscillator and driver tube in my DX-35 in 1956. Heathkit went to the 
6CL6 for the DX-40 and all subsequent ones.

> Now its an 
> audiophool tube and getting a bit scarce in some places.

Wouldn't doubt it...

> Cant figure where the micanol base has an effect. Ive tried the 6AB7, 6SK7, 
> 6SG7, and 6SA7 in a SX-28 to 44 MHz and didnt see any difference between NOS 
> of either type. Also tried the 6SB7 and 6SB7Y which was developed in 1946 
> for the current FM band. Have to try all in a NC-183 next which goes to 54 
> MHz.

I have tried the 12SG7 in a couple of ARC-5s in place of the 12SK7. I didn't notice any 
difference in gain, but there was a slight difference in the amount of noise.

I put a 6SB7Y into a Hallicrafters S-41G once: it made a pretty big difference over the 12SA7 
on frequencies above 14 MHz., but since I had to install a filament transformer and 
reconfigure the series filament string, it wasn't really worth the effort.

Ken W7EKB