Vitreous Enamel vs Wirewound Resistor - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th February 2004, 02:05 AM   #1
diyAudio Member
 
Join Date: Feb 2004
Location: Silicon Valley
Default Vitreous Enamel vs Wirewound Resistor

Greetings,

I'm gathering parts for my first tube project and most of them will be ordered from digikey.com.

In the spec that I have there is a high-power wirewound resistor for the output tube cathode. But I could only find "vitreous enamel" type with the suitable resistance/wattage value.

Are there any reasons not to use one or it can be freely substituted for a wirewound resistor?

Thanks!
  Reply With Quote
Old 10th February 2004, 06:19 AM   #2
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
Are there any reasons not to use one or it can be freely substituted for a wirewound resistor?
What's the wattage we're looking at?

I'd only use WW types in that position if they're of the non-inductive type.

Vitreous enamel ones are often magnetic, steel endcaps and leadout wires.

Cheers,
__________________
Frank
  Reply With Quote
Old 10th February 2004, 06:59 AM   #3
diyAudio Member
 
Join Date: Feb 2004
Location: Silicon Valley
Default Wattage

Thanks!

Nominal wattage will be 9-12W, depending on how hot I'll run the tube (6AS7G). I guess I need to overrate the resistor to keep the temperature reasonable, don't I?
  Reply With Quote
Old 10th February 2004, 07:03 AM   #4
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
"Vitreous enamel" refers to the protective coating over the (wirewound) resistor...
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 10th February 2004, 07:07 AM   #5
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
Vitreous enamel" refers to the protective coating over the (wirewound) resistor...
Yep. These are often the smaller wattage ones whereas the higher wattage ones are often clad in aluminium housings and need cooling from the metal chassis for best operation.

Cheers,
__________________
Frank
  Reply With Quote
Old 10th February 2004, 10:08 PM   #6
diyAudio Member
 
Join Date: Feb 2004
Location: Silicon Valley
Greetings,

Thanks for the explanations!

In a supplier catalog I've also found "T220 Style Thick Film Power Resistors" and "Aluminum Housed Wirewound Resistors"- both with high tolerance and in the suitable wattage.

Are there any preferences for one over another?
  Reply With Quote
Old 11th February 2004, 01:13 AM   #7
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Default Re: Vitreous Enamel vs Wirewound Resistor

Quote:
Originally posted by Valverine
Greetings,

I'm gathering parts for my first tube project and most of them will be ordered from digikey.com.Thanks!
Vitreous enamel is what they use to make toilets, in Europe, Japan, the Unites States even that bung-hole New Jersey!.

"What Trenton makes, the world takes" -- the old NJ cr*pper
  Reply With Quote
Old 11th February 2004, 01:54 AM   #8
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Yup, they wind resistance wire on pottery and fire it to a nice kiln glaze. Works great, doesn't it? Especially when you can run them red hot for much longer than any other type...

Tim
__________________
Seven Transistor Labs
Projects and Resources
  Reply With Quote
Old 11th February 2004, 03:55 AM   #9
diyAudio Member
 
Join Date: Feb 2004
Location: Silicon Valley
It's good that they don't make wirewound toilets in New Jersey ...

Anyway, picked up some nice 25W wirewounds in aluminum housing today in a local electronics surplus store.

Thanks, guys!
  Reply With Quote
Old 13th February 2004, 09:38 AM   #10
AV8R is offline AV8R  United Kingdom
diyAudio Member
 
Join Date: Feb 2004
Location: Cambridge
Default Vitreous Enamel Resistors

It's a pity that Americans are somewhat ignorant about these devices from the other side of the pond!

WELWYN have been making these since time immorial. they cover wattage ratings fron 21/2 to 14 watt. Because of their construction are very quiet and low noise. Are relatively non magnetic (since no metal is absolutely non magnetic in absolute terms). Their reliability is very good and the inductance is low i.e, similar to other wire wounds. The purpose of the vitreous enamel was to protect the wire from oxidizing at elevated temperatures. they are rated to a maximum of 350 deg C.

Values from 0R1 to 100K depending on wattage. have a loook at the Farnell cataloge at www.farnell.com/uk

The TO220 style power resistors are thick film types and do not handle short term overloads well and are noisy. Vishey this and Vishey that come on. Just very expensive thats all.

Aluminium clad need heatsiking to realize their wattage rattings and the voltage rating between resistive element and case is only good for 160 volt AC. so no good on tube HT circuits.

Go forget about toilet humour.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wirewound Pot Law Fake with Wirewound Resistor wrenchone Solid State 6 13th September 2007 06:45 AM
Is a Vitreous Enamel wirewound resistor a good replacement? erkess66 Parts 1 8th December 2006 09:26 AM
Wirewound cathode resistor Klimon Tubes / Valves 12 30th August 2006 10:19 PM
Enamel finish bjackson Multi-Way 11 26th April 2005 07:40 PM
large value wirewound resistor... contaxchen Parts 3 15th April 2004 05:22 PM


New To Site? Need Help?

All times are GMT. The time now is 03:34 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2