Amp Tech Thread / Ask a tech Q

inductorguitars · February 01, 2012, 03:36:38 PM

Need a recommendation on a cheap but good oscilloscope. I had a Tek 456, but that is gone with the ex.

Edit:
This one is really close to my house and seems like a good deal.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170775374000&ssPageName=ADME:X:RTQ:US:1123

VOLVO))) · February 03, 2012, 07:37:37 PM

I'm in proper need of a tube tester and an O-scope, myself. Lookin' for that book, by the way. Had a few leads on it.

EDIT: no downloads available.

inductorguitars · February 04, 2012, 12:52:02 PM

Quote from: SunnO))) on February 03, 2012, 07:37:37 PM
I'm in proper need of a tube tester and an O-scope, myself. Lookin' for that book, by the way. Had a few leads on it.

EDIT: no downloads available.

Yea I searched but only found fake links.

Hemisaurus · February 08, 2012, 08:54:07 AM

Never liked the 2212 myself, it always felt kind of cheap, the trace never seemed to focus enough.

Erik, do you happen to have an audio generator that sweeps? I'd trade you a nice HP scope for one. The one with the DMM built in on the top

inductorguitars · February 08, 2012, 01:32:41 PM

Quote from: Hemisaurus on February 08, 2012, 08:54:07 AM
Never liked the 2212 myself, it always felt kind of cheap, the trace never seemed to focus enough.

Erik, do you happen to have an audio generator that sweeps? I'd trade you a nice HP scope for one. The one with the DMM built in on the top

Oh I do. An old HP tube job. I have to get it down from my storage loft in my office.

It's a HP 200ABR (Tho is says 200AB it's the rack mounted version. 4U)

(The 1/4" jack is a mod in this pic)

It hasn't been turned on for years and I currently don't have a variac...

Hemisaurus · February 08, 2012, 03:25:53 PM

We should organise a little jaunt to Bloomington. It's about midway, and we can trade, I think shipping might be a bitch. You can meet the little guy, and we can have pizza or Flat-Top or something.

justinhedrick · February 08, 2012, 04:15:23 PM

Quote from: Hemisaurus on February 08, 2012, 03:25:53 PM
We should organise a little jaunt to Bloomington. It's about midway, and we can trade, I think shipping might be a bitch. You can meet the little guy, and we can have pizza or Flat-Top or something.

take him to avanti's.

Hemisaurus · February 08, 2012, 05:41:22 PM

http://chicagostylepizzeria.com/ would be where I'd go. It's odd, because I never saw a pizza like this anywhere in Chicago.

inductorguitars · February 08, 2012, 06:53:30 PM

Quote from: Hemisaurus on February 08, 2012, 05:41:22 PM
http://chicagostylepizzeria.com/ would be where I'd go. It's odd, because I never saw a pizza like this anywhere in Chicago.

LOL is that an Atkin's Diet Pizza?

The meet up would have to be on a weekend...

My cell number is on my Email me page on my site.

Instant Dan · February 12, 2012, 08:39:10 PM

Can anyone tell me what this noise is at :46? It sounds like a static/white noise when I turn the master volume to 6 or more.

Hemisaurus · February 12, 2012, 09:15:51 PM

Nope, Invalid Youtube Link

VOLVO))) · February 12, 2012, 11:33:56 PM

ruh oh... Sounds ground-y....

Hemisaurus · February 13, 2012, 12:08:13 AM

I'd have someone look at it, in the real world

Erik, that metal plug with the external ground pin scared me a lot, I put on a shiny orange plastic one instead

It was good as the rubber in the cable was rotting too.

Instant Dan · February 13, 2012, 01:10:53 AM

A shot in the dark, but do lights with dimmers contribute to amp noise/hum? The room my half stack is in has lights with dimmers.

Hemisaurus · February 13, 2012, 09:46:02 AM

Yes they do, as do fluorescents, cell phones, TV's (not too sure about plasma and LED ones), microwaves, fridges, washers, heaters, vacuums. Anthing that puts noise on the power line, or electromagnetic radiation in the air. Dimmers are in the former category, the thyristor firing in bursts, will introduce noise on the power line, they probable generate some EM as well. That's why the PA bible, and I think some amp install manals like Crown's, say always keep your stuff on a separate circuit, and well away from.

inductorguitars · February 13, 2012, 03:11:51 PM

Quote from: Hemisaurus on February 13, 2012, 12:08:13 AM
I'd have someone look at it, in the real world

Erik, that metal plug with the external ground pin scared me a lot, I put on a shiny orange plastic one instead

It was good as the rubber in the cable was rotting too.

Yea I forgot about that plug. Hey man it was the 50's.

Hemisaurus · February 13, 2012, 03:24:07 PM

Yeah, no big issue, but then I noticed it's worn and cracked at the grommet end as well, so I'm just going to see if I can add a new cable, got plenty of nice orange 3 core hanging around here.

justinhedrick · February 13, 2012, 04:26:27 PM

Quote from: Hemisaurus on February 13, 2012, 03:24:07 PM
Yeah, no big issue, but then I noticed it's worn and cracked at the grommet end as well, so I'm just going to see if I can add a new cable, got plenty of nice orange 3 core hanging around here.

more importanty, did you get the pizza?!

inductorguitars · February 13, 2012, 08:16:38 PM

Quote from: justinhedrick on February 13, 2012, 04:26:27 PM
more importanty, did you get the pizza?!

No, we went to flat top grill. MY GF is Gluten free, plus that pizza sounds WEIRD.

rayinreverse · February 23, 2012, 10:31:16 PM

What's the scoop on using a mix of kt88s and 6L6s in an amp. Eurotubes have it as an option for 5150s. Think its possible in a Butcher?

Hemisaurus · February 24, 2012, 06:37:13 AM

Well the output sections are very similar, the xfmr have different part numbers though, so it's not a straight copy. The KT's use almost twice as much heater current as a 6L6 though, so it would depend on the capability of their power xfmr. Having recently tried to get transformer info from Peavey, I've discovered it's one thing they won't talk about, which surprised me as they are generally pretty helpful.

I'd email the Eurotubes guy, he seems to have one of every amp in the universe, and would probably be willing to experiment for you

KT88's can get 100W out of a pair, but have similar plate load and grid bias requirements as the 6L6 doing 55W, so I guess the idea should work, as long as the heater supply can handle it.

dunwichamps · February 24, 2012, 02:35:35 PM

Quote from: Hemisaurus on February 24, 2012, 06:37:13 AM
Well the output sections are very similar, the xfmr have different part numbers though, so it's not a straight copy. The KT's use almost twice as much heater current as a 6L6 though, so it would depend on the capability of their power xfmr. Having recently tried to get transformer info from Peavey, I've discovered it's one thing they won't talk about, which surprised me as they are generally pretty helpful.

I'd email the Eurotubes guy, he seems to have one of every amp in the universe, and would probably be willing to experiment for you

KT88's can get 100W out of a pair, but have similar plate load and grid bias requirements as the 6L6 doing 55W, so I guess the idea should work, as long as the heater supply can handle it.

you may need additional bias setup since bias voltage will be different

Hemisaurus · February 24, 2012, 04:02:53 PM

I thought that, then I looked at the datasheet. In the 500V plate range, which is where the Butcher and the 5150/6505 live, they (KT88 and 6L6) are actually both very similar. Hence I imagine Eurotubes selling them as 'without bias mod' sets. I imagine he just matches them up as a quad.

dunwichamps · February 24, 2012, 04:03:47 PM

i have heard he matches them by plate current. the only other concern is spacing, do you have adequate space between the sockets for Kt88s

Hemisaurus · February 24, 2012, 04:22:09 PM

I believe that's why it's a mixed set of the 5150, as there's not the space to do a full KT-88 transplant, hence me suggesting he ask the guy at Eurotubes