Author Topic: L2 Bead ? What is it?  (Read 15555 times)

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Marek

L2 Bead ? What is it?
« on: June 06, 2004, 06:08:45 PM »
Hi!

I'm looking @ this schematic

http://www.tubefreak.com/v-twin.gif

and there is L2 where it just says 'Bead'.

Now, can somebody pls point me to a pic of this 'Bead' thing? Anywhere in internet. :-)

I tried to google for it, but... nothing helpful came up.

Thanks in advance.

Marek

R.G.

L2 Bead ? What is it?
« Reply #1 on: June 06, 2004, 06:13:59 PM »
It's a bead of ferrite magnetic material. It's used to make RF-suppressing inductors.

By the way, that 1H inductor value is probably wrong, unless there is a big iron core inductor in there.
R.G.

Quick IQ Test: If anyone in a governmental position suspected that YOU had top-secret information on YOUR computer, how many minutes would you remain outside a jail cell?

Marek

L2 Bead ? What is it?
« Reply #2 on: June 06, 2004, 06:40:28 PM »
O, that was a quick response... :-)

I don't have the original unit, I was just trying to make a cab sim from that schematic.

Thanks about the info on those beads, and about the 1H inductor. Why do you think that the value (1H) is not correct?

I was so happy when I found a small transformer with 1,2H inductance @ Conrad.de.   I thought I simply put that one in the circuit, but now that you tell me that it might be wrong...

Should it be more or less Henrys?

Thanks,
Marek

Eric H

L2 Bead ? What is it?
« Reply #3 on: June 06, 2004, 08:09:16 PM »
Quote from: R.G.

By the way, that 1H inductor value is probably wrong, unless there is a big iron core inductor in there.


Mesa has used large-value inductors in their eq's for a long time, RG  --in the graphic section of the boogies, anyway. I see no reason to doubt that scheme on this basis. I've seen a similar scheme elsewhere that had the same value.

-Eric
" I've had it with cheap cables..."
--DougH

Marek

L2 Bead ? What is it?
« Reply #4 on: June 07, 2004, 05:42:17 PM »
Is this the 'L2' we're talking about?

http://www.jktcompany.com/img/3_l.jpg

toneman

L2 Bead ? What is it?
« Reply #5 on: June 07, 2004, 09:54:21 PM »
YeP!
those look like em.
I know 1 synth manufacturer that draws them as inductors.
technically i guess they are, but as RG says "not 1H".
they actually have their own ANSI nomenclature.
i thought an inductor had to have at least one winding??
Probably just a good point1 bypass cap would suppress
all those highfreaks, or was that Freqs??
Definitely hi?
all choked up.....
tone
TONE to the BONE says:  If youTHINK you got a GOOD deal:  you DID!

Nasse

L2 Bead ? What is it?
« Reply #6 on: June 08, 2004, 11:11:43 AM »
:roll: I quess such "bead" is used to filter radio freq interference and suppress frequencies above audio, maybe designer wanted to prevent such things bouncing back to that 386 chip feedback loop

I have seen some schems (some mic preamps and such) and one ready made kit I owned with thing named "bead" and there was just instruction in the text like "few turns of copper wire around small ferrite bead"

If it works without the bead I think it does not have audible difference

Marek

L2 Bead ? What is it?
« Reply #7 on: June 08, 2004, 11:23:01 AM »
Aha, so just take some copper wire and turn it few times around the ferrite thing?

And...  c'est tout?


OK, I'll try that.

Greetings,
Marek

Eric H

L2 Bead ? What is it?
« Reply #8 on: June 08, 2004, 02:12:42 PM »
Quote from: toneman
YeP!
those look like em.
I know 1 synth manufacturer that draws them as inductors.
technically i guess they are, but as RG says "not 1H".

tone

Look again, there are 2 inductors. L1 is 1H.
This is the only cab-sim I've seen with a large inductor as part of the speaker-sim which makes it  an interesting circuit.  
If you back up at that site you can look at schemes for the boogie's --which have 5-band eq's using inductors (.02H to 1.2H) instead of gyrators --unusual, but they've done it for years. if you look at  some of the other amps you will see different versions of cab-sims, and they all employ 1H inductors. I haven't seen the inside of a Boogie with a graphic-eq, but those inductors can't be that large, physically.

http://www.tubefreak.com/mesa.htm
http://www.tubefreak.com/subway5.gif
http://www.tubefreak.com/mk4-5.gif

YMMV

-Eric
" I've had it with cheap cables..."
--DougH

toneman

L2 Bead ? What is it?
« Reply #9 on: June 08, 2004, 03:15:48 PM »
if the inductor(that's how it's drawn) is indeed a 1H,
that's *one henry*, and, as RG said, "that's a mighty big inductor"!!
i probably could use it to filter the battery charger for my electric car.  
:shock:
A ferrite bead, straight thru, no turns,
 has very little (actually measurable)inductance,
especially in the audio band.  
It's regularly used in RF(RadioFrequency) stuff.

An inductor to "simulate" a speaker(coil) is novel.
:?
Inductors *were* (always)used B4 gyrators, that's all there was.
After opamps got cheap, most EQs went that way, eliminating inductors.
Inductor size is related to power handling capability.
So, definitely, for this application, definitely on the smallish side.
so why the 1H label?? typo??  Maybe meant point1??
How small *could* U make a 1H inductor???
:?:
inquiring minds etc etc
tb
TONE to the BONE says:  If youTHINK you got a GOOD deal:  you DID!

toneman

L2 Bead ? What is it?
« Reply #10 on: June 08, 2004, 03:26:55 PM »
here's some links on inductors--

this tells how 2 wind them--
http://www.ee.surrey.ac.uk/Workshop/advice/coils/

this gives theory--
http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/55-509-1/Ch6.htm

searching at www.mouser.com, only returned Hammond transformer
stuff for the large sizes.
LOTs and lots of uH(that's micro henry) stuff--
http://www.mouser.com/index.cfm?&handler=data.listcategory&Ntt=*1*%2b*henry*&terms=1+henry&Dk=1&D=*1*%2b*henry*&N=0&crc=false
TONE to the BONE says:  If youTHINK you got a GOOD deal:  you DID!

Paul Perry (Frostwave)

L2 Bead ? What is it?
« Reply #11 on: June 08, 2004, 08:38:11 PM »
One Henry isn't REALLY big, it's only twice the size of a 500 millihenry wah inductor!

toneman

L2 Bead ? What is it?
« Reply #12 on: June 08, 2004, 10:07:09 PM »
There Ya go, Paul.
Size *does* matter!
Guess i won't B using it for my EV.
tb
TONE to the BONE says:  If youTHINK you got a GOOD deal:  you DID!


ErikMiller

L2 Bead ? What is it?
« Reply #14 on: June 09, 2004, 08:21:48 AM »
I used to think that a 1 Henry inductor would be HUGE, like when dealing with capacitors, where a 1 Farad cap is bigger than any I've seen.

Then I started cloning old Fender tube amps, and their power supplies often call for a 2 to 20 Henry inductor for filtering. They are not huge, they look like small transformers.

Marek

L2 Bead ? What is it?
« Reply #15 on: June 09, 2004, 10:18:09 AM »
Ya man, but wher do u get thoz inductors?

No, really, where did you get them back then? Custom made ?? :-)

Greetings,
MArek

lovekraft0

  • Guest
L2 Bead ? What is it?
« Reply #16 on: June 10, 2004, 05:44:55 AM »
I use a Mouser submini transformer primary for a 1.5H choke in my varitone circuits ( and so does Torres, and several other guitar hotrodders). I think the part # is 42TL021, and it's tiny, as in about 1/2" in all directions. Cheap, too! :) Might work here if you adjust the caps.