Davecv41

I had a similiar Rat Shack xtal radio when I was a kid, and still have it. Probably the best $2.99 gift I've ever gotten. A book called Batteries and Bulbs II that I saw in 5th grade had variable capacitors made out of book sized cardboard covered with 2 pieces of aluminum foil and waxed paper as an insulator. The simple radios I made always worked, but I can't quite follow the magnet wire the author of the article used in his to try to reverse engineer his circuit. It's possible he didn't use a germanium diode, and I've found that crystal earphones oxidize inside and cease to work.

Thanks Bruce and Tom. The fabric did increase the WAF and has kept her off my backside in the 20 or so years since I installed it. I didn't have a way to measure how the fabric changed the sound compared to the original grill cloth, but I don't remember hearing a difference. I have a pair of K-400 horns and have plans for a center channel, though I'm not sure of which type to build. Fortunately I now live about an hour from Mr Crites and can get his opinion, as well as hear some Jubes.

A Google search for Emerson Paper in Oil Capacitors turned up a link on a Fender Stratocaster forum I found interesting. I'd imagine guitar players are critical listeners with their instruments similiar to the way we are with our speakers. Here they compare capacitor types: Capacitor: Orange drop vs Paper in oil | Fender Stratocaster ...

Well, that worked. My homemade 45 amp is in front, and a rebuilt Philco 20 radio is on top. I'll try it again with the left Khorn - a Japanese tube radio kit is on top next to a homemade crystal radio.

Tom, I still have them. Hopefully the pic comes thru...

Selling it? No, those reviewers are actually handing out free bottles of it when they put out anything besides specs and price. Disclaimer: I know someone who works for Monster Cable. I politely declined when he offered to get me some of their product at a discount.

Thanks for your post. I've been inactive here for several years, and am seeing what others have done to their Khorns before I decide on how to improve mine.

I got many of the parts for my 45 and 300B projects from Antique Electronics Supply in AZ www.tubesandmore.com

Nice work, Tom. The grill cloth works well with the Jubilees. I did the same thing with my 1966 KWOs to increase their wife acceptance factor. Back in the '90s when the wife ordered a sofa and loveseat with a green fabric pattern called Cunningham Forest, we got a few extra yards of the fabric. I did the front and side grills of both Khorns. I haven't heard many complaints about their presence since then.

630 volt caps are pretty common. Personally I'd replace every cap there except the silver mica types. And test and replace any of the carbon resistors that test out of tolerance.

An audible difference in volume when running a low power 2 watt tube amp between the left and right channels from a central listening position. In my experience this was absolutely noticeable at low listening levels. I could hear no audible difference when the amp was cranked up though. It would be interesting along the lines of voltage, resistance, and current, to see what is different between your two channels. Something like a test tone fed into both channels of your preamp and measured at the speaker's input terminals with an oscilloscope. If you can hear it, you should be able to measure it, and thus be able to figure out why the amplitude portion of the signal differs between channels.

Wolfbane, would you mind elaborating what your experience was with unequal length speaker wire while using a low power SET amp? Thanks

Mustang Guy, my avatar picture is a common one I lifted off the internet. My mom told me how I was left alone in a room as a toddler and a piece of string was found hanging out of an outlet when she returned. Some of us got bitten by the electrical bug pretty early. Or zapped by it. Dave

I've been playing with wires since I was 7, and soldering since I was about 8, mostly radios and other projects I saw in library books. In high school I accidentally shorted the output of a graphic equalizer and blew the op amp IC; the repair guy at the car stereo store told me to get a roll of desoldering wick and explained how to replace it. In the navy I went to a month long miniature soldering school and got NEC 9527 out of it. I remember one entire day was spent tinning resistors, another whole day was spent bending them so that they fell out perfectly when the board was held upside down. After one of the tasks, the instructor would take the hot soldering iron and stick it straight thru the board and tell the student to repair it. I still clean, flux, and tin everything before soldering it to something else, then clean the flux off with IPA. I've recapped the crossovers in my 1966 KWOs, rebuilt the ones in my Minimus-7s, and built a 45 amp from an article in Glass Audio. A crossover would have been something that a bunch of us here could have assembled before junior high school. Dave retired USN tron chaser

That amp makes me want to abandon my 300B project halfway thru. If you could/would post a schematic, it would probably make me stop drooling.

I saw a tube amp made by Nobsound in the window of a Japanese restaurant last year. I looked it up and it appeared to be a hybrid, tube input with solid state output. Model MS-10D available on Amazon for under $200.

IIRC the recommended practices for DCC are to put a twist in the wire several times per foot to cancel out interference. With DCC you can locate your Power Station(s) and boosters in the middle and not be restricted to a panel. Your trains sound like they draw a lot of current. now is the time to upgrade your locos to can or coreless motors and convert passenger car lighting to LEDs if you haven't done so already.

I think I just drooled into my lap. The bar has definitely been raised on Cornscala construction. Those are beautiful.

Gents, what happens is that the capacitors in tube gear eventually dry out. The largest capacitors are in the power supply, and they're usually electrolytic. If they open up and lose their filtering capacity, you get hum. But if they short, you get an overcurrent in the high voltage section. This could fry the rectifier tube, or damage the power transformer. Tubes are replaceable, but transformers can be expensive or worse depending on the rarity of the equipment. If you think your amp needs to be brought up on a variac, it needs to be serviced. Healthy electronics don't need to babied that way. I've used plastic capacitors in lieu of electrolytics in some of my antique radios hoping they'll last longer, but it may be a long time until I find out if it worked. The only piece I own that I regularly bring up with a variac is a 4 tube Japanese AM radio kit with a 100vac primary.

Just how old are these married Cub Scouts?

The schematic shows a lot of filter capacitors attached to the cathode at pin 8. Get the amp checked and recapped if it hasn't been yet. The selenium rectifier looks like a good candidate to be replaced at the same time.

+1 I'm also curious what you used for the LED dial bulbs. I've used LEDs since I was a teenager in the early '70s but never tried them for dial lights in a tube circuit.

The capacitors dry out from age, so they affect how the speaker sounds.

The first guy to listen to my '66 Khorns didn't like how one of them sounded so he passed. The wife of the original purchaser had a portable CD player connected from the headphone jack to the RCA inputs of an Onkyo receiver. Turning the plug of the offending channel cleaned up the sound. I've been enjoying them for the last 20yrs.

It sounds like leftover flux from soldering. Good soldering practice is to remove it after the solder is cool, but it won't hurt anything if left in place.