Any schems showing the slave out?

[Gaz]

I'm feeling lazy. Do any schems/layouts show the slave out found on some Dumbles? Thanks.

[heisthl]

Not sure how HAD did it but an easy way is to connect a 2k2 resistor between the 4 Ohm tap and a jack, then put a 200 ohm resistor across the jack. Or if you want it variable do it like Yamaha.

[Gaz]

That's helpful thanks, I've seen Mesa do it that way too. I also found an old thread with this article, but I just can't figure out what all the extra parts are for???

I was also curious if HAD took the slave out from just after the preamp or at the speaker jack.

[Gaz]

I also have a stupid question? How do I size of the resistors to drop the voltage?

[heisthl]

most of these type of speaker derived slave outputs work on a 10 to 1 ratio, so these designers are thinking they need to reduce the speaker signal to 1/10th to get it to a line level. It's a simple voltage divider. There is so much current available you don't have to worry about drawing the amp volume down.

[Gaz]

Thanks! 10:1, got it. Did you take a look at that attachment in my other post? Can't figure out what the caps are for doing, and of course the article wouldn't dare explain...

[M Fowler]

Henry,

Thanks I have been wanting to add this feature to an amp so getting schooled is great.

Mark

[heisthl]

Thanks! 10:1, got it. Did you take a look at that attachment in my other post? Can't figure out what the caps are for doing, and of course the article wouldn't dare explain...

Probably just fear of direct coupling and possibly too much extreme low end put the .01uF there and the fear of too large a signal put the 220k there and finally fear of high end fizz put the .02uF there.

You should do it both ways and report back on how crappy the caps make it sound

[Gaz]

Thanks! 10:1, got it. Did you take a look at that attachment in my other post? Can't figure out what the caps are for doing, and of course the article wouldn't dare explain...

Probably just fear of direct coupling and possibly too much extreme low end put the .01uF there and the fear of too large a signal put the 220k there and finally fear of high end fizz put the .02uF there.

You should do it both ways and report back on how crappy the caps make it sound [/quote

LOL. Will do.

Here's a few more dumb questions while I'e got your attention:

1. Do the resistor/pot values matter at all as long as I'm getting a 10:1 ratio?

2. What about the resistor power ratings?

3. Does the slave out have to be taken from the same tap as the feedback? I've seen it from the same tap in every schematic I've seen (besides the Yamaha).

I think the answers are no, no, and no, but I honestly don't know why!

[heisthl]

LOL. Will do.

Here's a few more dumb questions while I'e got your attention:

1. Do the resistor/pot values matter at all as long as I'm getting a 10:1 ratio?

2. What about the resistor power ratings?

3. Does the slave out have to be taken from the same tap as the feedback? I've seen it from the same tap in every schematic I've seen (besides the Yamaha).

I think the answers are no, no, and no, but I honestly don't know why![/quote]

1. no 2. in most cases even 1/2 watt is overkill 3.no but why not?
Be bold Be Brave, the formula for power is voltage times current or voltage times voltage divided by resistance. Once you work backwards from wattage and resistance (your 2 known values) and work out the voltage you can then work forwards with Ohms Law (voltage = current times resistance or current = voltage divided by resistance) to solve for current through the 2 resistors you choose, then take the next step and figure the resistor wattage needed from there using the power formula again. Hint: unless you're using 1 ohm resistors, the answer will be amazingly small.

[Gaz]

Thanks, and now that I've got that figured out I'm just more confused!

I'm trying to figure out the values for a 200W amp (which is what I'm working on)...

I read that line level is .775VAC, and I'm guessing the rough 10:1 rule can't be applied to my 200W project because the with the Yamaha values of 47k and 5k my max voltage out would be almost 4 volts.

Assuming the Yamaha is a 50W, then the max voltage out would be just under 2 volts, which seems reasonable. Of course the max out will be more when the amp is cranked.

To get 2 volts with my 200W examples, and sticking with a 5k pot, I'd have to make the upper half of the divider about 100k. That's cool with me, but I'm just curious if this resistance is too high, and mess with the fidelity. If so, is there another way around it to get the voltage down?

Hope my questions make sense! Thanks.

[markusw]

The Fc of the 220k/20n low pass in the pdf seems a bit too low.
With 20n it has Fc of 36.17 Hz.
200p would give a Fc of 3617 Hz, 20p a Fc of 36171 Hz.
Would make more sense to me.

Regards,

Markus

[vibratoking]

I'm trying to figure out the values for a 200W amp (which is what I'm working on)...

I read that line level is .775VAC, and I'm guessing the rough 10:1 rule can't be applied to my 200W project because the with the Yamaha values of 47k and 5k my max voltage out would be almost 4 volts.

Assuming the Yamaha is a 50W, then the max voltage out would be just under 2 volts, which seems reasonable. Of course the max out will be more when the amp is cranked.

To get 2 volts with my 200W examples, and sticking with a 5k pot, I'd have to make the upper half of the divider about 100k. That's cool with me, but I'm just curious if this resistance is too high, and mess with the fidelity. If so, is there another way around it to get the voltage down?

Disclaimer: The following is only valid for sine wave voltages.

For a 200W amp into an 8 Ohm load:

P = V^2/R so V = sqrt(200x8) = 40 Vrms or 40 VAC

Calculating the power consumed in the slave resistor divider with a 47k resistor and a 5k pot:

P = V^2/R so P = (40^2)/52k = 30.8mWrms

Calculating the voltage on the slave out out with a 47k resistor and a 5k pot:

Minimum voltage is 0V
Maximum voltage is (5k/52k)x40Vrms = 3.8Vrms or VAC = 5.4 Vpp = 2.7V amplitude.

Looks to me like the max voltage could overdrive the line input, so if you have a pot, adjust it. BTW, too high of a resistance may make the slave out signal noisy, but the speaker output should be fine. Too low may affect the slave signal and the speaker output. Stay in the range of the values given and all should be fine.

I don't really know the spec so I'll take your word for it. I hope seeing the calculations, helps. This assumes that your amp can drive 200W into an 8 Ohm load. After seeing the math, you should be able to recalculate for a 16 or 4 Ohm load, for instance.

[Structo]

What is the difference between a Line Out and Slave Out?

Or is it the same thing?

Seems like the Slave Out might be a stronger signal (more volts) than the typical Line Out which is used to plug into PA or mixer board.

[Gaz]

I think the terms are mostly interchangeable, but my understanding is that a line out is usually taken from the preamp, sometimes before any tone controls or attenuation, while a slave out is taken from the speaker. The term slave is used because the master amp is used to control the gain and tone, while the slave is just to clean, er... I mean, be clean. Man, call me PC, but I really hate all the master/slave analogy.

Edit: And it's my understanding that both slave and line-out are typically supposed to be between .5VAC and 1.5VAC