Recomended Voltages

[W2INR]

I am reworking a Ranger 2 I picked up at NEAR-Fest in the fall.

I am using a pair of 6550's in the modulator. I am currently running about 300Vdc on the screens and about -30 on the grids.

What is the optimum voltages to run on the box? I know from experience that the 6550's come into their warm sound running around 65%.

Any thoughts?

G

[W3NP]

I put a pair of 6550's in my Ranger to withstand the higher voltages that resulted from the solid stating of the power supplies. Currently running 317v on the screens and -33 on the grids. I pretty much did all of the standard Timtron mods to mine with the exception that the audio chain was left basically stock except for a few component value changes for better freq response. I use it mainly as a CW rig but it does sound clean on AM. No recommendations here, just a report.
I had the 6550's from a CE 200V that I had back in the early 80's - glad I hung on to the spare tubes.

[W2INR]

Thanks for the input. It looks like I am running the tubes at similar voltages.

G

[k4kyv]

What is "warm sound"?

[KI4YAN]

"Warm", "tubey" sound occurs when the tubes are run in a range where they produce 5-10% second harmonic distortion, but very little third or fifth harmonic distortion. The even harmonics produce a pleasing effect to the ear, similar to the way a simple major chord sounds "better" than simple minor chord. Getting above about 10-15% however, starts to actually sound distorted, so best to avoid an unusually-high-distortion amplification stage.

It's been tested and tested, proven and disproven, only to be proven again in audio circles, and this IS something you can measure on a scope, and hear with your ears. Not trying to be condescending here, just trying to head off that argument.

Sometimes, Ultra-low-distortion is not what you want, but it is handy.

[KM1H]

Here is where the warm and looney crowd hang out, its always good for a laugh.

http://www.audiokarma.org/

Carl
KM1H

[Mike/W8BAC]

Here is where the warm and looney crowd hang out, its always good for a laugh.

Hay Carl,

I joined the Sansui user group at audiokarma a few years ago when I rebuilt my old quad receiver. The collective was a big help locating hard to find replacement parts and a few people really knew my rig inside and out. They really helped me out. Kinda like the people here helping others and not poking fun.

I don't think I would characterize them as "loony" at all. One guy even volunteered a copy of the original manual at no charge. A good, friendly bunch. If somebody here was looking for tech help on vintage stereo gear I would recommend audiokarma as a start.

Mike