I know you are not supposed to run a tube amp without having speakers connected to the terminals, but I was wondering if it is harmful to the amp if the amp is on with no speakers connected, but there is no signal being input to the amp?
+4
cci1492
peterh
yel17
monkuboy
8 posters
Speaker load on ST-120
monkuboy- Posts : 45
Join date : 2016-03-23
yel17- Posts : 9
Join date : 2015-04-23
Age : 75
Location : Chicagoland
No speakers, no input signal, no problem,
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
It's still dangerous. A thump on the power line or an airborne discharge will create a signal that is amplified and potentially damaging the output transformer.monkuboy wrote:I know you are not supposed to run a tube amp without having speakers connected to the terminals, but I was wondering if it is harmful to the amp if the amp is on with no speakers connected, but there is no signal being input to the amp?
If you need to have amp powered on without load, shorting the output will protect the amp.
cci1492- Posts : 331
Join date : 2016-05-09
Age : 63
Location : NJ
I know you meant input.
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peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
No i ment shorting the output !cci1492 wrote:I know you meant input.
This is to prevent high voltages building up in the output transformer.
Shorting a tube amp has no immidiate danger, it will increase temp on the plates if
shorted and signal applied.
cci1492- Posts : 331
Join date : 2016-05-09
Age : 63
Location : NJ
Interesting, I thought that winding should always see a load. Very good then, learned something new. So "A thump on the power line or an airborne discharge will create a signal that is amplified and potentially damaging the output transformer" is not a problem with the output shorted. Good to know, thanks.
aguaazul- Posts : 136
Join date : 2012-07-08
Age : 64
Location : Livermore, CA
I connect up a 8 Ohm 100W Dummy Load to the speaker posts on all amps when working on them with power or testing them. It's safer. I screwed them down to a 10" piece of 2 x 4, when I go to work on an amp on the bench, it comes out. I used 2 - 4 ohm - 100W power resistors connected to aluminum angle as a heatsink gives 8 ohm @ 100 watts. Mounted these to the aforementioned 2 x 4. Easy to bang one of these out, you'll be glad you did.
Cheers,
Aguaazul
8 Ohm Dummy Load
Cheers,
Aguaazul
8 Ohm Dummy Load
Last edited by aguaazul on Sat Jun 12, 2021 6:28 pm; edited 1 time in total (Reason for editing : Fixed Photo's)
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edman44- Posts : 24
Join date : 2021-06-14
Age : 61
Location : PENNSYLVANIA
Hello Aguaazul,
I just bought a VTA ST-120 KIT. I was reading your post and wanted to build your dummy load. And was wondering where you bought your resistors from? Sure sounds like something I am going to need. Thanks,
I just bought a VTA ST-120 KIT. I was reading your post and wanted to build your dummy load. And was wondering where you bought your resistors from? Sure sounds like something I am going to need. Thanks,
aguaazul- Posts : 136
Join date : 2012-07-08
Age : 64
Location : Livermore, CA
edman44 wrote:Hello Aguaazul,
I just bought a VTA ST-120 KIT. I was reading your post and wanted to build your dummy load. And was wondering where you bought your resistors from? Sure sounds like something I am going to need. Thanks,
I got them from Amazon!
uxcell 100W 4 Ohm Screw Tap Mounted Aluminum Housed Wirewound Resistors 2 Pcs
Get 4 of them to get your 8 ohms.
Cheers,
Aguaazul
Last edited by aguaazul on Wed Jun 16, 2021 10:36 pm; edited 1 time in total (Reason for editing : Fix Link)
Njrob- Posts : 50
Join date : 2022-05-14
Location : Nj
I have 2 8ohm 100w wirewound aluminum. Is there a limit to duration of use? Of course no input. Thanks.
Tubes4ever- Posts : 167
Join date : 2015-07-14
Location : Star, Idaho
Njrob wrote:I have 2 8ohm 100w wirewound aluminum. Is there a limit to duration of use? Of course no input. Thanks.
No. No limits.
Njrob likes this post
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