Cactus Tube Dudes of Arizona

Get together.

We went to go listen to Dan's system. His horns have 30 pounds of lead shot in the base of each speaker. The sub is up off the floor to tune them to the room. The Ah Tjoeb is hot rodded too. We first listened to the Decware SE34-I (EL-34, 6N1P) , then the Paramours and eventually Dan's home made amps. Dan tried to get away with saying his home made amps needed a few more minutes of soldering before they'd work. So we went and watched him solder for a few minutes. 

Here's a close up of the top side of the amp.

These cool attenuators look like they are single series single shunt stepped attenuators. Dan purchased these "Ultimate Attenuators" from Ric Schultz at Electronic Visionary Systems (EVS). The switches are Elna BV225xxx's. These beasts are no longer made so keep an eye on Audiogon and Ebay if you want to buy a set.

This is the inside of Dan's amp. The case is black powder coated steel.
I like this type of meeting. We got to solder, make music and even make some smoke.  Details on Dan's amp.

This amp has a pentode driver and a pentode output tube wired ultralinear. Originally we listened to the amp with no feedback it was very musical, but didn't have a stable image or much control. However, it sounded very liquid and very listenable.

When we hooked the feedback up per plans, we had to reverse the output transformer secondary winding to keep it from oscillating. With the feedback hooked up, the right channel (and only the right channel) hummed like a swarm of bees in a tin can. We grounded one leg of the filament to stop the hum, but we couldn't find where it was coupling in (like we should of.) Now the amp had image and control, but the musicality suffered. We couldn't stay and play any longer. It's fun tweaking up an amp.

Ideally we would let the amp hum to just find out how the filament is injecting the hum and remove that coupling path. We'd then AC short the filament to ground to get rid of the filament coupling inside the tube.

While we were experimenting on the amp, we used bleeders to discharge the caps. These bleeders had microclips that didn't stay on very well, so we used three of them. One of the times we powered the amp up with one of  the 10K 10W bleeder still attached and after a while I was saying "Do you smell something?" Well the heatshrink tubing on the bleeder was starting to smoke a bit. So we pulled the power plug and put the bleeder somewhere it wouldn't hurt anything while it cooled off. Woo Hoo! A smoking good time!

I had fun at this meeting! I like meetings where the solder gets flung.

Amps:

Dan's Home made amp using a 6SJ7 and 6BG6GA output tube.
Decware SE34-I (EL-34, 6N1P)
Voltsecond's Paramour (Someone said they aren't Paramours anymore because they have too many mods!)

Ed's Hornshoppe Horns with 30 lbs of lead shot in each base.  HornShoppe Forum  The HornShoppe Dan's Horns sound much better than mine. I'll have to pull mine out of the guest bedroom and start tweaking.

Subwoofer: Parts Express "Titanic" 10 inch kit (inputs to sub came directly off the speaker outputs of the power amp.)

In line shunt attenuators "Ultimate Attenuators" from Ric Schultz at Electronic Visionary Systems (EVS)

Ah Tjoeb 4000 CDP re-modified by ModWright

DH labs BL-1's (bought from Upscale Audio)

Oops I didn't get their name.

None

Attendees:

Volt         S.
Boyd        B.
Dan         A.
Mrs. Volt  S.

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14 Dec 2002. 

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