Can i use a 8 ohms resistor instead of the speaker ??
Laurentdangelo
want to use the preamp section with an other power amp, but it seems that i
need to load the power output of the head ??
Thanks. Laurent.
Kevin D. Kissell
> On my amp head, can i use a 8 ohms resistor instead of the speaker ?? .....i
> want to use the preamp section with an other power amp, but it seems that i
> need to load the power output of the head ??
Yes. But of course you need a resistor big enough to handle the
current coming out of your amp. You should have seen the ones
I had to use (in parallel) when I was working on my SVT...
Mike Schway
"Laurentdangelo" <laurent...@wanadoo.fr> wrote:
If it's a tube amp, yes, you HAVE to have a load. If it's a solid state
amp without an output transformer (95% of SS amps don't have an output
tranny), you won't need one.
If you need an 8 ohm load, it has to be able to handle the full output
of the amp. 100-150W wirewound resistors cost around $15-20, or you can
make up a 4x4 series-parallel array of cheaper 10W resistors which will
give you 160W capacity. You'll need lots of air space around the
resistors. They'll heat up.
--------------------------------------------------------------------
Mike Schway | [Picture your favorite quote here]
msc...@nas.com |
--------------------------------------------------------------------
Gary Gerhart
<Kev...@paralogos.com> wrote:
>Yes. But of course you need a resistor big enough to handle the
>current coming out of your amp. You should have seen the ones
>I had to use (in parallel) when I was working on my SVT...
>
1000 1/2w 4ks ?? ;-)
Gary Gerhart
www.GerhartAmps.com
Kevin D. Kissell
Nah, 2 150W 8ohm ceramic-coated coils. And the suckers got
hot enough to scorch the wood they were mounted on. It might
bave been cheaper your way, but I knew that the probability
of my getting that many solder joints right was essentially zero. ;-)
Laurentdangelo
................but .................do i need to have a 100Watts resistor
if i dont use the power section of my amp head (output level to 0) ??
(if output level =0 then output voltage will be low so, amount of power will
be small, isn't it ??)
bye.
"Laurentdangelo" <laurent...@wanadoo.fr> wrote in message
news:at56nv$9jk$1...@news-reader11.wanadoo.fr...
Kevin D. Kissell
> thanks everybody !!
>
> ................but .................do i need to have a 100Watts resistor
> if i dont use the power section of my amp head (output level to 0) ??
>
> (if output level =0 then output voltage will be low so, amount of power will
> be small, isn't it ??)
At this point you really do need to say what make/model of amp
you are talking about here. Most guitar amps control the output
level by modulating the preamp gain - an output level of zero
wouldn't drive the power amp (so you could use a lightweight
load), but you wouldn't get any pre-amp output, either.
Mike Tulley
<laurent...@wanadoo.fr> wrote:
>thanks everybody !!
>
>................but .................do i need to have a 100Watts resistor
>if i dont use the power section of my amp head (output level to 0) ??
>
>(if output level =0 then output voltage will be low so, amount of power will
>be small, isn't it ??)
IF you never turn it up by accident, you don't need a resistor at all,
but perhaps a small resistor would be a good idea. If it starts to
smoke, it will remind you to turn the power section back to 0!
By the way, a 1500W electric space heater is about 10 ohms. Add a 100W
light bulb in parallel with that, and you have a load that will
protect your amp even if you run the output at full power, and will
light up to remind you that it is on. Just cut the plug off of an
extension cord and replace it with a 1/4" plug (or whatever fits the
output of your amp).
Mike T.
Dave Curtis
I've got an electric heater that measures 8 ohms. It'll handle about
12 amps.
Tony Hwang
Why not just pull the PA tubes, even PI tubes then?
Tony
tubeguy
"Laurentdangelo" <laurent...@wanadoo.fr> wrote in message
news:at56nv$9jk$1...@news-reader11.wanadoo.fr...
steve eaton
"Dave Curtis" <beth...@adelphia.net> wrote in message
news:7mvcvuceo9484h5o3...@4ax.com...
Should be good for about 1000w I'd think.
JTM50
If there is then you need one.
Pulling the power tubes and using the effects loop send as your pre out (if
your amp has one) is the best Idea.
Lloyd
in article at5ke6$2co$1...@news-reader12.wanadoo.fr, Laurentdangelo at
laurent...@wanadoo.fr wrote on 12/11/02 11:38 AM:
Mike Schway
JTM50 <lgi...@telus.net> wrote:
> he key here is that there can't be a signal going through your power tubes.
> If there is then you need one.
> Pulling the power tubes and using the effects loop send as your pre out (if
> your amp has one) is the best Idea.
May not be a good idea if the filter caps are rated close to operating
voltage. Removing output tubes will cause B+ to increase 25-30% That
may be too high for the caps (also your preamp will be running with
hotter plates...you may not like that sound).
--Mike
JTM50
Lloyd
in article mschway-923729...@netnews.attbi.com, Mike Schway at
msc...@nas.com wrote on 12/10/02 9:14 PM:
Ken Gilbert
> light bulb in parallel with that, and you have a load that will
problem here is that the 10r resistance only occurs when the element
is at operating temperature, dissipating 1500w, and has 120vac across
it.
at lower temperatures the resistance will be MUCH MUCH lower, probably
a fraction of an ohm. the positive temperature coefficient causes the
operating resistance to go up as it gets hot, and naturally limits the
current/power dissipation.
ken
CJT
Are you saying there are amps out there that will self-destruct if
the output tube heaters open? That doesn't sound like a very good
design.
Mike Schway
wrote:
> Mike Schway wrote:
> > Removing output tubes will cause B+ to increase 25-30% That
> > may be too high for the caps (also your preamp will be running with
> > hotter plates...you may not like that sound).
> >
>
> Are you saying there are amps out there that will self-destruct if
> the output tube heaters open? That doesn't sound like a very good
> design.
>
Not really. It's not going to be an immediate thing. After all, folks
can safely leave their amps on standby without blowing their first stage
caps, but extended standby with under-rated filters (in amps where the
first stage is charged when in standby) may not be a good idea.
Besides, if your output tube heaters open, you'll know it and will shut
it down before too long. (Usually only one tube will fail at a time,
though)
crow
sinks on it would be a good idea - these things get HOT.
epp
geetar67
Where can you get higher wattage resistors? I was thinking of making a -20dB
L-pad in the meantime till I can get an attenuator. For -20dB @ 8 ohms @
30W, the resistor values are 7.2 ohms/26.7W and 0.89 ohms/3.3W. Do these
have to be the exact values, or can you ballpark them? Are certain types of
resistor (e.g., wirewound) better for this application than others? Certain
brands? Thanks,
--
Arch
crow
get 'em from Mouser or some surplus houses I know of. A "mil spec" 30 watter
is good for 50watts in the real world (in my experience).
j'epp
"geetar67" <geeta...@SPAMyahoo.com> wrote in message
news:BA1E4DDE.3B75%geeta...@SPAMyahoo.com...
Steve Cowell
"geetar67" <geeta...@SPAMyahoo.com> wrote in message
news:BA1E4DDE.3B75%geeta...@SPAMyahoo.com...
You'll be OK with an 8ohm 25watt and a 1ohm 3watt... or you can buy the
150watt adjustable L-pads from MCM. They're less than $20, IIRC.
__
Steve
.
geetar67
>
> "geetar67" <geeta...@SPAMyahoo.com> wrote in message
> news:BA1E4DDE.3B75%geeta...@SPAMyahoo.com...
>> Where can you get higher wattage resistors? I was thinking of making
> a -20dB
>> L-pad in the meantime till I can get an attenuator. For -20dB @ 8 ohms @
>> 30W, the resistor values are 7.2 ohms/26.7W and 0.89 ohms/3.3W. Do these
>> have to be the exact values, or can you ballpark them? Are certain types
> of
>> resistor (e.g., wirewound) better for this application than others?
> Certain
>> brands? Thanks,
>
> You'll be OK with an 8ohm 25watt and a 1ohm 3watt... or you can buy the
> 150watt adjustable L-pads from MCM. They're less than $20, IIRC.
Thanks for the tip, Steve!
--
Arch