Is it normal to have to use the balance control on a preamp?

[phileserver39]

Howdy fellow AR visitors,

I have a tube preamp (Audio Experience Symphonies Plus) which has 3 12ax7 tubes plus a rectifier tube. Here is the link to the product page on YS's site:

http://www.ys-audio.com/sp+.htm

From what I read the center 12ax7 controls the balance.

I notice that with my Sovtek tubes I have to crank the volume knob to the right (to approximately 1:30 on the clock dial) in order to get the image to be centered. Yes, I have played several tracks from different artists, producers, etc.

I think it may be that my tubes are unmatched. Would this cause the volume discrepancy that I am experiencing?

Thanks for your time and expertise,

Jason

[E-Stat]

From what I read the center 12ax7 controls the balance.

What wording leads you to that conclusion? Mr. Sang's Engrish not so goodly or flowing like calm river.

I think it may be that my tubes are unmatched. Would this cause the volume discrepancy that I am experiencing?

Possibly. Try reversing a pair. One tube could be defective such that one of its triodes is not as strong as the other. The balance control is there because many recordings are not equally matched. On the other hand, the issue may simply be that the knob itself is not centered.

rw

[Feanor]

...
Possibly. Try reversing a pair. One tube could be defective such that one of its triodes is not as strong as the other. The balance control is there because many recordings are not equally matched. On the other hand, the issue may simply be that the knob itself is not centered.

rw

Also consider that the 12AX7 tube is "twin triode" and actually consist of two amplfiers in one tube. If is possible that two channels in the one tube are not matched. If you preamp has an odd number of tubes, (other than in the power supply), then it's virtually certain that one tube is handling both R+L channels at one stage of amplification.

As far as I know, a balance control is a very simple device: variable resistor, actually a potentiometer, that siphons off some voltage from alternately the left or right channel in order to achieve balance. A balance control like that will have an extremely minmal effect on the signal, is cheap, and really ought to be provided in any preamp, despite that many preamps don't provide one.

[E-Stat]

Also consider that the 12AX7 tube is "twin triode" and actually consist of two amplfiers in one tube.

Which was exactly my point when I said "One tube could be defective such that one of its triodes..." One tube - dual triodes. Perhaps my wording was not clear. The three tubes are likely implemented as each providing a specific function with each half handling a channel.

rw

[phileserver39]

Thanks guys. I ordered a new, matched set 3 of tubes and will see if putting those in will even out the balance.

[hifitommy]

some recordings arent exactly balanced and likewise phono cartridges. in that case, a balance control can be used as a sort of focus control. once perfect balance is achieved, things snap into focus. try and see if it isnt true.