Sounds like your tubes have some heater-cathode leakage. The solution is to use a different tube.
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Crack;Bottlehead OTL - Page 111post #1651 of 81053/21/13 at 10:25am
Head-Fi's Best Sellerspost #1652 of 81053/21/13 at 1:08pmQuote:
OK, will do! This humming noise comes and goes if you tap on the tube with a pencil and then comes back after a bit.
Is there a technical reason for what's happening like part of the guts that aren't supposed to be touching actually are, or something? The guy I bought the tube from claimed it tested 95/95 and had 'no microphonics.' Meanwhile if you tap it lightly with a pencil it sounds like a mule kicking a spring reverb in a guitar amp.post #1653 of 81053/21/13 at 1:19pmpost #1654 of 81053/21/13 at 1:21pmpost #1655 of 81053/21/13 at 2:07pm
I gave him the benefit of the doubt that the postman was playing football with the package on the way to my house.
The hum isn't all that loud (you quit hearing it as soon as you start playing music at low volume.) How risky is it to use leaking tubes though in terms of them going 'full short' ??post #1656 of 81053/21/13 at 2:12pm
As long as it isn't crackling or popping it will probably be OK. And sometimes the hum can reduce with some burn time. Sometimes not.post #1657 of 81053/21/13 at 2:29pm
This is a circa 1943 RCA 6AS7G. I noticed people online doing things like baking them in the oven to 'dry out' the bakelite base in case of shorting that way. I presume the heat generated while being used would cause that moisture to flee the base though. I'm going to test the 'bulb' from the base to make sure it's not loose tonight. I'd love for it to quiet down because I really like the way it sounds. I need to befriend someone locally with a tube tester and the knowledge required to use it.post #1658 of 81053/21/13 at 3:15pmQuote:Originally Posted by silverhead
This is a circa 1943 RCA 6AS7G. I noticed people online doing things like baking them in the oven to 'dry out' the bakelite base in case of shorting that way. I presume the heat generated while being used would cause that moisture to flee the base though. I'm going to test the 'bulb' from the base to make sure it's not loose tonight. I'd love for it to quiet down because I really like the way it sounds. I need to befriend someone locally with a tube tester and the knowledge required to use it.
Not sure what circa I have, but I've got no noise. I can post a pic tonight of it. In fact have three spares.post #1659 of 81053/21/13 at 3:51pm
How do the pins look on that tube silverhead? Back in mid-2011, I had an RCA12bh7 blackplate with an unfortunate hum issue, and Doc suggested buffing the pins with fine steel wool as a possible fix. I used fine grain sand paper, in the absence of steel wool, and then inserted and removed the tube a dozen or so times. The hum was completely eliminated.
I don't know if this has the same probability of success on a power tube, but I figured it would be worth tossing out there.post #1660 of 81053/21/13 at 10:25pm
I get after everything that comes to the house with Caig DeOxit D5 and Q-tips. I can try to burnish the tips, but they're already pretty clean and newish looking I have 00 steel wool to try though. My guess is that it took a hard knock on the USPS truck. I have more coming in the mail.
I've been trying to score oddball 12AU7 equivalents to see what sort of differences I hear as well. It's been fun.
Edited by silverhead - 3/21/13 at 10:28pmpost #1661 of 81053/21/13 at 10:49pmpost #1662 of 81053/21/13 at 11:13pmQuote:
Hard to say. I've been looking around for awhile and it seems they basically go for the price of the kit, if they are built well. Everything I've read on the bottlehead forums is pretty wary of buying prebuilt kits because if any issues show up down the road they are hard to pinpoint. If the kit isn't built well it could easily be a mess.
edit: Should also add you shouldn't sell the kit for more than it costs directly from bottlehead on the head-fi forums unless you are a member of the trade.
Edited by elwappo99 - 3/21/13 at 11:14pmpost #1663 of 81053/22/13 at 12:21ampost #1664 of 81053/22/13 at 4:07pm
it is a DIY kit, but bottlehead will assemble it for a fee im pretty sure. I was part of the first groupbuy i believe for the Crack amp . I don't really use the amp anymore but still deciding on whether I want to keep it or not, I have an emotional attachment too actually since I built it. I haven't been on head-fi for awhile, pursuing other hobbies. The only thing I cant seem to live without is IEMs though.post #1665 of 81053/22/13 at 4:37pm
We no longer build amps for customers. My techs are hired for R&D work and they don't have the time to fit kit assembly into their schedule any more. But anybody can build one of these kits. There are literally thousands of Bottlehead kits out there that have been built by beginners.
- Crack;Bottlehead OTL
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