kruz

dumb G9 question - matching
« on: October 04, 2004, 08:57:16 AM »
Hi all..
i'm strating to populate my G9 boards and i was wondering about stereo matching..
What parts should be worth matching to get equal performances on both channels?
How about the tubes? Is it really worth getting matched pairs?

too many dumb quetions :wink:


gyraf

dumb G9 question - matching
« Reply #1 on: October 04, 2004, 09:16:19 AM »
No reason to match tubes here.
..note to self: don't let Harman run your company..

kruz

dumb G9 question - matching
« Reply #2 on: October 05, 2004, 09:23:05 AM »
Thank you Jakob..
Could you please also explain me why? I'd like to understand while building your great project.
How about other parts? anything worth been matched? (beside the gain switch resistors)

mcs

dumb G9 question - matching
« Reply #3 on: October 05, 2004, 01:22:13 PM »
If you use standard 1% resistors, you don't have to worry. I would use tubes that aren't too far apart, but not nescessarily matched. The circuit uses feedback, so the exact tube specs aren't that important.

Best regards,

Mikkel C. Simonsen

kruz

dumb G9 question - matching
« Reply #4 on: October 06, 2004, 08:26:26 AM »
oh.. feedback..
now i see that.. :oops:
thank you Mikkel :thumb:
Now, thinking about stereo matching i think that the worst part that could compromise the matching could be the 47k log pot for the output.
Well.. i was thinking to swap it with a simple 1x12 Lorlin (stopped at 11 position to get 300° indexing as the input swicth)
I'm trying to use this calculator for the R values for each step:
http://www.quadesl.com/attenuator.html
But it's unclear to me what should i enter in the "total attenuation" field.. :roll:  
any idea?

gyraf

dumb G9 question - matching
« Reply #5 on: October 06, 2004, 08:31:42 AM »
Hi Kruz,

I would recommend that you first build the unit as it is, and then later decide if you need to modify it for stereo operation. My guess is that it won't be an issue even with standard components.

Jakob E.
..note to self: don't let Harman run your company..

kruz

dumb G9 question - matching
« Reply #6 on: October 06, 2004, 08:34:17 AM »
that's fine jakob.. but i'd like anyway to be able to easily recall settings.. i really like to have steps ..

microx

dumb G9 question - matching
« Reply #7 on: October 06, 2004, 11:49:33 AM »
The real issue here, if there is one, is the overall gain of each channel. If you have the gear to do it put a tone say 1khz thru each channel and measure the output . Find the setting on the level control which gives the same from each channel. If the valves are about the same the feedback will equal out the gain. Personally I would not change the pot for a switch as then you will then not then have the fine adjustment you might need to balance two channels into stereo.
Steve


 

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