Line Out Mod

steveb63 said:
I would like to run a line out from my Marshall PB 100 attenuator.

A way to control the volume from the new line out would be useful as well.

So what I'm really trying to say is: @Amp Mad Scientist , could you please help me out and walk me through this procedure?

Thanks for any help or input.
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OK
I'll be back in a couple days. I'm backed up at the moment but I'm coming back here shortly.

In the meantime, I think other members will also have good suggestions.
 
steveb63 said:
I would like to run a line out from my Marshall PB 100 attenuator.

A way to control the volume from the new line out would be useful as well.

So what I'm really trying to say is: @Amp Mad Scientist , could you please help me out and walk me through this procedure?

Thanks for any help or input.
Click to expand...
Though I'm not familiar with a lot off attenuator circuits (including the Power Brake), of the ones that I am familiar with, the line out circuitry is usually taken directly off the input to the attenuator, so is "pre attenuation". The line out circuit is typically a resistive voltage divider network that will "divide" off a signal that is in the range of 1/10th the amps output voltage. As such, the attenuator's line out is essentially the same thing as an amplifiers line out that is derived from the secondary winding of the output transformer. Because the line out circuit is also essentially in parallel with the speakers (load), the resistance of the voltage divider network must be sufficiently high so as to not mess too much with the speaker loading (impedance). Ideally the line out circuitry would feature a volume control, though this isn't always the case. Some also feature tone controls.
Here's a couple of example schematics I just pulled off the net.
The first is the Weber Mass 100 that features an adjustable level (volume control) line out with a switchable tone control stack.15930415926317696375633278473077.png
As can be seen, the line out circuitry is directly off the attenuator input & aside from the switchable tone stack, the circuitry is very simple.
The second is the much simpler line out circuit used in the Weber MiniMass, fixed level (no volume control) & no tone control. 15930417408097556482922793518271.png
The voltage divider is made up of a 10k & 4k7 resistor, again directly off the attenuator input.
I use a Weber Mass 200 attenuator that feature an adjustable (volume control) line out with an adjustable treble correction tone control. I could draw the schematic from if you like.
I'm sure you could find many, many more line out circuit examples on the net to take ideas from. Hope this helps. Cheers
 
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Thanks

I think the above will be just fine.

The line out will go to my rec interface, then get speaker and cabinet I/R, volume and tone are not needed.

Thanks for the above info, I'm going to start doing some reading etc. ..

Much appreciated, thanks again.

Steve
 
ivan H said:
The voltage divider is made up of a 10k & 4k7 resistor, again directly off the attenuator input.
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I noticed that in the schematic, these resistors are rated at a 1/2 watt. This is another example of my lack of proper knowledge of electronic circuits, but I don't understand why there's such a low voltage signal going into the line out jack while there's a bunch of wattage going thru the rest of the attenuator... :unsure:
 
syscokid said:
I noticed that in the schematic, these resistors are rated at a 1/2 watt. This is another example of my lack of proper knowledge of electronic circuits, but I don't understand why there's such a low voltage signal going into the line out jack while there's a bunch of wattage going thru the rest of the attenuator... :unsure:
Click to expand...

Good question, one of these pros will let us know.

I'll mainly be running my Thirty watt Marshall through it, most definitely want enough protection....

Amp Mad Scientist is coming up with a design for me in the near future.

Mainly be doing this as a "paint by numbers" being that I'm woefully ignorant on this subject.
 
syscokid said:
I noticed that in the schematic, these resistors are rated at a 1/2 watt. This is another example of my lack of proper knowledge of electronic circuits, but I don't understand why there's such a low voltage signal going into the line out jack while there's a bunch of wattage going thru the rest of the attenuator... :unsure:
Click to expand...
To put it into easily understood terms, the speakers, or speakers & the attenuator take care of the high current that the output tubes deliver. You see, the speakers, or speakers & attenuator present a much smaller impedance than the line out's voltage divider (& input impedance of whatever it's plugged into). Electricity is lazy, so takes the path of least resistance. If the speakers or the attenuator's current soak were not hooked to the amps output, those little half watt resistors would fry in an instant. Cheers
 
ivan H said:
To put it into easily understood terms,the speakers and/or speakers & the attenuator take care of the high current that the output tubes deliver. You see, the speakers and/or speakers & attenuator present a much smaller impedance than the line out's voltage divider (& input impedance of whatever it's plugged into). Electricity is lazy, so takes the path of least resistance. If the speakers or the attenuators current soak were not hooked to the amps output, those little half watt resistors would fry in an instant. Cheers
Click to expand...

Thanks for that easy to understand lesson.

I will post what I think my plan is, with pics. It will take me a couple of days to find the time.

When I do, would sure be helpful if you could give me your opinion, I really don't want to hurt my JTM 45...… that would not be good!

I appreciate your time, thank you.
 
RVA said:
Alternatively, I have Weber attenuators that I want to move. They are high quality, load bearing units snd they all have a line out
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Yes, but I already have the Marshall attenuator, or I'd for sure jump on a Weber. I run my Fender rig with a Mass Lite 50.

If I change my mind, I'll definitely hit you up, love Weber's products.
 
It's labeled "ez bake oven", has my attention.

I have been using it for a few years with no troubles.

Hmmmm
 
steveb63 said:
I really don't want to hurt my JTM 45...… that would not be good!

I appreciate your time, thank you.
Click to expand...
No, that would not be good at all, best not do that, & glad I could be of help.
Amp Mad Scientist said:
Fun Time Bio Lock-down Quiz: Can anybody spot the mistake in this schematic?

View attachment 45289
Click to expand...
We're off Bio Hazard lockdown here, thankfully (which is why I haven't been at TTR of late, so much to catch up on), so I'll let others have a go first, before I supply an answer regarding what should be rectified in this schematic. Cheers
 
ivan H said:
No, that would not be good at all, best not do that, & glad I could be of help.
We're off Bio Hazard lockdown here, thankfully (which is why I haven't been at TTR of late, so much to catch up on), so I'll let others have a go first, before I supply an answer regarding what should be rectified in this schematic. Cheers
Click to expand...

You see the error?
Not many people see that.
 
Yes, I do & good catch on that. If you hadn't drawn attention to there being an error I would most likely have just quickly glanced at the schematic without noticing it. We'll see who else picks up on it. Cheers
 
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