Would using a 16ohm speaker damage my SE output transformers? - Page 2

Pano · 16th September 2012, 03:22 PM

Quote:

Originally Posted by flatheadmurre

Enough so you get the power needed for listening !

What I really meant was - "If it is not advisable to run a tube output unloaded, how much load do you need?" Would 100 or 600 ohms on an 8 ohm tap be enough? If yes, then 16 ohm speakers on a 4 ohm tap should be just fine, right?

kevinkr · 16th September 2012, 03:29 PM

I've not had problems with loads of up to 100 ohms, but would not recommend running much more than 16 ohms on 4 ohm taps as this is unknown territory to me..

flatheadmurre · 16th September 2012, 03:53 PM

It´s the reflected load on the tube that´s interesting, not what load you have on which winding.

Somewhere a long the line the tube starts misbehaving with a to light load, then you have reached the limit.

As long as there is enough load on the transformer to prevent voltage building up creating shorts there shouldn´t be a problem ??

Vinylsavor · 16th September 2012, 04:14 PM

Hi!

The amp will not get destroyed if you run it with a 16 Ohm speaker unless it is extremely poor designed. In that case it could also be destroyed with a 4 Ohm speaker if run hard. Keep in mind that the speaker impedance varies over a wide range for most speakers. Even a 4 Ohm speaker can have impedance peaks well above 30 Ohms in the bass region.

In my experience many speakers benefit when they are being driven from a lower impedance. As suggested you can experiement with resistors in parallel. But keep in mind that a big portion of the power will then get burned in the resistor. A resistor will linearize the speaker impedance. This may or may not yield a sound improvement. Experiment and use what works best

Thomas

wa2ise · 17th September 2012, 12:55 AM

Quote:

Originally Posted by flatheadmurre

Headphones are sensitive devices and what a speaker eat chew and spit out will kill the headphones.

And it won't do your ears any good either.

Do be careful you don't have the volume up too high when you connect your headphones.

Francois G · 17th September 2012, 02:40 AM

Quote:

Originally Posted by kevinkr

I've not had problems with loads of up to 100 ohms, but would not recommend running much more than 16 ohms on 4 ohm taps as this is unknown territory to me..

Kevin,

I'm surprized at your reply.

Is it simply your personal "unexplored territory" that made you say that or do you know of theoretical reasons why it may be harmful to drive more than 16 Ohms from a 4 Ohm transformer tap?

The question was about safety, not fidelity. It is reflected load that matters, is it not?

Francois

kevinkr · 17th September 2012, 05:47 AM

Quote:

Originally Posted by Francois G

Kevin,

I'm surprized at your reply.

Is it simply your personal "unexplored territory" that made you say that or do you know of theoretical reasons why it may be harmful to drive more than 16 Ohms from a 4 Ohm transformer tap?

The question was about safety, not fidelity. It is reflected load that matters, is it not?

Francois

Perhaps you are reading too much into my reply..

In the case of a zero feedback amplifier there is a point where effectively even though there is "something" connected to the secondary it no longer constitutes an effective load, and under fault conditions there is probably greater potential for excessive voltage to be developed across the primary in the event the output tube is driven into hard clipping or cut off. (flyback) This is probably far higher than the numbers discussed here, but without knowing anything about the amplifier I can't put a hard fast number on what is ok and what isn't.

Without scope, the specific amplifier and load on the bench I can't reasonably state what maximum value of load might be safe under worst case circumstances. All I'm actually saying is "proceed with caution" and I am just one voice amongst many here.

cotdt · 17th September 2012, 02:24 PM

I tried it and it works perfectly fine with 16 ohm speakers and 25 ohm headphones on the 4 ohm output. It is off triode-strapped EL84's. Thank you kevinkr and everyone else.

cotdt · 17th September 2012, 03:12 PM

I just tried my 600 ohm headphones and it works too!

palmas · 18th September 2012, 08:59 AM

Not a problem even to let the the speaker unconnected, at least in all my designs and constructions!
I just use good quality transformers and use a fixed load of 220Ohm inside the amp.
I test run them unloaded to see if there is any problem and there never was...
Also run them with 2Ohm and appart from the small reducing in frequency response, never had a problem.

16th September 2012, 03:29 PM	#12
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	I've not had problems with loads of up to 100 ohms, but would not recommend running much more than 16 ohms on 4 ohm taps as this is unknown territory to me.. __________________ "Extraordinary claims require extraordinary evidence." - Carl Sagan

16th September 2012, 04:14 PM	#14
Vinylsavor diyAudio Member Join Date: Feb 2002 Location: Lindau	Hi! The amp will not get destroyed if you run it with a 16 Ohm speaker unless it is extremely poor designed. In that case it could also be destroyed with a 4 Ohm speaker if run hard. Keep in mind that the speaker impedance varies over a wide range for most speakers. Even a 4 Ohm speaker can have impedance peaks well above 30 Ohms in the bass region. In my experience many speakers benefit when they are being driven from a lower impedance. As suggested you can experiement with resistors in parallel. But keep in mind that a big portion of the power will then get burned in the resistor. A resistor will linearize the speaker impedance. This may or may not yield a sound improvement. Experiment and use what works best Thomas __________________ http://vinylsavor.blogspot.com/

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16th September 2012, 03:53 PM	#13
flatheadmurre diyAudio Member Join Date: Mar 2011 Location: Jarna	It´s the reflected load on the tube that´s interesting, not what load you have on which winding. Somewhere a long the line the tube starts misbehaving with a to light load, then you have reached the limit. As long as there is enough load on the transformer to prevent voltage building up creating shorts there shouldn´t be a problem ??

17th September 2012, 02:24 PM	#18
cotdt diyAudio Member Join Date: Oct 2005	I tried it and it works perfectly fine with 16 ohm speakers and 25 ohm headphones on the 4 ohm output. It is off triode-strapped EL84's. Thank you kevinkr and everyone else.

17th September 2012, 03:12 PM	#19
cotdt diyAudio Member Join Date: Oct 2005	I just tried my 600 ohm headphones and it works too!

18th September 2012, 08:59 AM	#20
palmas diyAudio Member Join Date: Jun 2007	Not a problem even to let the the speaker unconnected, at least in all my designs and constructions! I just use good quality transformers and use a fixed load of 220Ohm inside the amp. I test run them unloaded to see if there is any problem and there never was... Also run them with 2Ohm and appart from the small reducing in frequency response, never had a problem.