kx200 question

[jc7070]

Hi, When doing the bias and balance adjustments should you have a load on spkr terminals? I know you jump the center terminals.
Thanks,JC

 

[Dave451]

I always put a non-inductive load (resistors) on the speaker terminals whenever it is turned on on the bench and not running into speakers. This is for the health of your output tubes and transformers. When adjusting balance and bias, it needs to be quiescent, that means no input signal and volume control all the way down.

 

[jc7070]

Thank you dave,will use resistors. I want to try this with my KG4s.

 

[Dave451]

Interestingly, neither the service manual or operating manual for the KX-200 (or the X-200 for that matter) mention connecting the speaker terminals to a load when doing adjustments or even operating the amplifier. This is puzzling, since the rule I've always heard says to never operate a tube amplifier without some sort of load connected to the speaker terminals. Maybe they just assume you know to do it. Below, for example, is the instruction in the X-100 manual:

"The FISHER X-IOO must not be operated before connecting loudspeakers or equivalent load resistors to the Speaker Terminals in each channel; otherwise serious damage to the equipment may result."

You are correct about shorting the center output, which is clearly described in the service manual. Good luck with it!

Dave

 

[Dave451]

Hey, KX-200 into KG4's--excellent! I run my X-200 (factory wired version of your amp) into my Crite's modified (titanium horn tweeter diaphragms) KG4's and it sounds marvelous!

 

[jc7070]

Thank you very much Dave,I will let you know how it turns out!

 

[bhamham]

I'd use load resistors. The Fishers that have headphone jacks and 'off/on' speaker switches, I think it's OK to switch to off to do minor adjustments, like bias settings. There are load resistors built in the circuit on those models, not found on the KX-200. I use Klipsch Quartets with my KX-200 and sounds really nice too.

 

[jc7070]

Thanks bhamham, I use 8ohm power resistors.

 

[jc7070]

Unit is up and running into my kg-4 speakers and sounds great!! Thanks to all.

 

[nj pheonix]

As i understand it , its a quasi myth. Some tube amps are unstable without a load on them. Many in fact (perhaps most) are very stable without a load. Having said that i tend to use resistors during testing and setting. You never know when the amp you're working on is an unstable one. Its cheap and easy.

 

[larryderouin]

I take the path of least resistance. Dummy loads or speakers matching the speaker ohm level for that tap for all tube gear, period. I use a salvaged pair of mini advents with 8ohm drivers in it. I don't like 4 ohm loads so the 8ohm drivers.