The tale of Ultrapath and speaker wire.

[3dzapper]

I have had a message from George Wright I copied regarding his 2A3 amps for a while. It says:

"I have tried various different ideas and it seems the first is still the
best, even high grade coupling capacitors do not seem to improve the sound
at all. There is one thing you could do, install a 2 uf 5% 600 VDC poly or
oil filled capacitor from the B+ possitive rail, red lead from everywhere,
to the cathode lug, the lead where the 100 uf 100 VDC possitive end
electrolytic is located. These two lugs are at each end of the center 6 lug
solding terminal inside. As always, make sure the unit has been unplugged
for no less than one hour before attempting. Thank you.
Best regards,

George Wright"

A few weeks ago, I finally got a "roundtuit" and installed a pair of 2uF motor run cans under the hood of the Mono 10s. The difference was immediate. Like taking a mask off a beautiful slim lady. Silky smooth in the mids and treble but something is missing on the bottom end. It would have taken a bit of circuit modification I did not wish to perform to restore the bass to my liking, so I clipped the wires. I wanted to try a larger value capacitor to see if that might help, but there was not enough real estate under the hood for anything I had.

That experience got me to thinking about trying an ultrapath caps in my 300b SET amp. I found a pair of matched NOS Mallory 35uF @ 270VAC motor start caps in my box of tricks and installed them between the B+ and cathode side of the cathode resistor. It sounded wonderful!! After a couple of hours, I started to hear some distortion. I was correct in my assumption that those caps could not take the sustained high DC voltage in that application. Mallory used nice oil I found out when I moved the amp to cut the wires.

I have some 60uF @ 440VAC ASC motor run caps that I have always wanted to try in an ultrapath position. They are just too big. I would have to cut holes and mount them from the top. Not wanting to do that and after reading a bit about ultrapath caps on the web, I decided that some 12.5uF GE motor runs that i had bought for crossovers would be perfect. They are!!! Everything is there in spades, highs, mids and the cleanest bass you've ever heard from a DHT. Things that would overload the amp at 95Db could now be taken in stride without a hint of the clipping that could be heard previously.

Being retired, I listen to my system more than most. I don't spend a lot of time in "critical listening" however.

After that change to ultrapath configuration, I turned up the volume, put on some vinyl and plopped myself down in the sweet spot for some nervana when lo and behold what is that coming from the left Klipschorn? Why it is distortion!!!! Frantic, I check and adjust the azimuth, VTA and tracking force on the TT. Still there, SHEET!! Next I changed inputs on the BBx, still there. Swapped the 6922 tube, nope. Swapped the 6SL7s side to side in the 300b then the 300bs. Then i swapped sides on the speaker wires. The distortion did not move. (Why didn't I think of that first? DOH!!)

I checked all the connections on the ALK that Shawn built and found that It must be a bad driver.(

I have never had a K-55 go bad on me in the 28 years I have had Klipsch. First time for everything I guess. I put in another K-55 in, thgat wasn't it. I had just rebuilt one of the three ALKs I got from Shawn on a normal sized board (He built them to fit inside LaScalas seperating components as far as possible.) I installed that, The danged distortion was still there, not as noticable now yet I could still desern it.

The only thing that I did not change in all this was the run of RCA 12Ga speaker wire from Home Depot. I have a set of silver plated, teflon insulated, OFC cables I made a while ago with dual runs of 18Ga and 14Ga + and - twisted into a single bundle. I have never liked them because of the extremely hot top end. They were the only wires I had that would reach corner to corner so I put them in. EAR BLEED!!!

Luckily, I have Altenuators on my JBL 2404s. I dropped the HF down something I could not do befoer I bought Al's transformers and got a better balance. Still a tad forward but very revealing and the distortion, GONE!!! I can honestly say, for the first time, that I heard something on a familiar LP that I had not heard before. On Jackson Brown's "Stay" I heard two toots on the sax come in just before the solo that had been heretofor obscured.

This is the first time I have ever heard of wire causing distortion. I am thinking of getting a run of Cardas Crosslink. Are there any others, not Munsters, I should consider without breaking the bank?

Rick

[LarryC]

If you need only 7' per side, I can send you a pair of Siltech LS-100 G3 that I have lying around. I haven't looked as yet into how much they cost used. I think you'd find them very smooth and clear, but somewhat spare in the bottom end.

Larry

[3dzapper]

Thanks for the offer Larry but the Khorns are a tad over 20 feet apart, one much farther from the amp than the other.

Rick

[sfogg]

Hi Rick,

Any idea what the capacitance of the speaker cable you were using is?

Perhaps if that was fairly high and the change you made to the amp made

it a little less stable the capacitance in the cable maybe started the

amp oscillating? I'd think that is less likely without feedback though.

Shawn

[3dzapper]

No Shawn. But it was one channel only. The distorion stayed in the left Khorn even when I swapped speaker leads at the amplifier.

Don't know me.

Rick