Harsh Digital to Glorious Analog in 1 weekend!!!!

[codhead]

"Na just a metaphore no need for banning. I might get a slap on the hand from Amy though LOL !!"

When did Klipsch get to be so PC? My mind may be playing tricks on me,

but I swear that not too long ago there were a bunch of pics of babes

with speakers (old Klipsch ads) on this site. If I'm not mistaken, the

link was titled "Exploited women of the 70's" !!!

[TBrennan]

Dean---Indeed, I'm not averse to using a little EQ myself. I'm now using a Citation 17 preamp with my Teac and 605s and using the EQ to add a little sparkle to the top of the Altecs, they being a little shy on top. I just might plug my Thorens record player into it too.

Of course all who understand compression drivers understand the need for some form of EQ with most of them.

[Deang]

Craig, technically - filter shaping is a form of EQ, something people should think about when they are deciding on a network. Finding the "best" positioning for the speakers is too, and so are room treatments. When a horn is mounted to compression driver, a lot of good things happen. Unfortunately, a smooth FR isn't one of them.

[tgourlie]

NOSValves

I guess I wasn't absolutely clear. There is still a hum from the

woofer. I took care of the extreme right channel hum. I

think it may have been a crossed connection at the RCA input. As

I was cleaning I noticed it was corroded.

So I still have a hum and a hiss, I can hear it if I listen

closely at the listening position. With my ear at the speaker, unacceptable

noise in my opinion.

Correct me if I am wrong, but if the filter caps are dry, there is no

other way around it but to get it fixed.... Right. Am I going to

get noise from a high eff speaker regardless??? Is that just the

tube nature?

somewhat of a newbie at the tube game. Know how they work, etc,

but never troubleshot one. ANy help from you guys would be great.

Thanks

[3dzapper]

"2nd I added a 17 tube, push pull monster in the form of an Audio Research D-76A(a pair of matched, original, GE 6550A's for each channel, and one more to regulate). Right off the bat it had a hum in the right channel and a lot of static. After some cleaning and deoxit, it is now reduced to a low stereo hiss that is only audible with my ear next to the horns. After speaking with AR service, we narrowed it down to the filter caps causing the hiss/hum that is left over. Now I must decide if the hiss, that I can not really hear at the listening position, is worth the $500 filter cap replacement surgery. And for some reason the 1st 12AX7 for the left channel is not glowing at all, but the left channel is working, so it does pass signal???"

Let's go back to the beginning.

As Craig said earlier, the PS caps would be more likely result in a hum than a hiss. Unless there is diode hash from the SS rectifier. That could be ameliorated with PS bypass caps and more modern FRED rectifiers. Not knowing the age of the AR, replacing the PS caps might just be prudent maintenance.

The hiss you hear is just as likely from a noisy tube or carbon resistor. Swapping tubes from channel A to B if the hiss moves one by one replacement could find the culprit. If it is a resistor, an oscilloscope or signal tracer would be needed to find the offending component.

If you like the amp, send it off to AR for an upgrade/repair or to maybe save some money(?), Craig has the necessary diagnostic equipment/experience as do others.

My $.02 anyway.

Rick

Edit: If anyone is interested in a schematic of the AR D76, here is a link:

http://www.arcdb.ws/D76/D76.html

[pauln]

Don't be so hard on Tom. We all know that he has a wire in his ear which seems to act up when he listens to some Klipsch products.

[NOSValves]

tgourlie,

No.... noise that is audible from your listening position is not normal from a properly working tube rig. For the most part if there is noise you should at the very least have to be standing right up in front of the speaker to hear it. With really well built and tweaked tube gear you should have to put your ear up to the horns to hear it. Hum should not be heard at all. (Hum will completely come from the woofer).

If your experiencing hum just out of one channel it usually means its something other then the main B+ power supply since almost all designs share the B+ power supply in both channels so usually if the main power supply is going bad the hum would be in both channels.

If you have not already you might want to try swapping all the front end tubes (small signal tubes) from channel to channel one by one and see if the hum follows a tube. Beyond that it most likely needs some work.

Craig

[tgourlie]

Thanks for input. I am going to swtich the tubes around and see if I can get one channel perfect.