liverpool effects question

[harris51]

Im working on a way to set a wet/dry rig my question is this: if I run another cable out my speaker jack into a direct box is it affecting the ohm load of my amp Im running the amp right now at 8 ohm(1- 8 ohm speaker) or is a direct box not a load. thanks

[harris51]

also would that be a speaker cable or guitar cable?

[geetarpicker]

It's hard to say but most direct boxes are not set up for speaker output loads. It could be a bad load on the amp. What I'd do is get two resistors, 56k and 1k, 1 watt should be fine. Build a box with the 56k in series with the input, then terminate this resistor to a 1k strapped to ground. Then take your final output off the two ends of the 1k the one side basically ground. This will net a pretty good line level signal, and you could tweak the 56k up or down a bit to vary the level. You can simply plug the dry cab straight into the amp, then use the 2nd speaker jack to drive this speaker level to line level pad. Since it puts about a 56k load on the amp when in parallel with say an 8 ohm speaker load the difference will be a non issue. I'd use speaker cable to the pad circuit, then shielded cable from it's output to your effects setup. I've used this circuit many times to drive the wet side of a wet/dry rig using my original Express amp. Ken himself told be about this basic voltage divider circuit over 20 years ago.

[Reeltarded]

Oh no way! That is silly! You are awesome! I am thinking 25kL pot with a 47k resistor. Wow, that is almost the Marshall variable line out now that I think about it.

Thanks for that screaming freebie, I owe ya one!

[martin manning]

Tried to steer you this way once before Miles: https://tubeamparchive.com/viewtopic.ph ... 303#204303

[Reeltarded]

I remember. You didn't say it like that.

[surfsup]

Hey reeltarded, if you need a schemo for this you can check this thread for a similar line out:

https://tubeamparchive.com/download/file.php?id=25543

As MM said in other thread:

Put a 22-33nF cap across the shunt if you want to simulate a speaker's HF roll-off around 5-7.5 kHz

You can still do this on the wiper to ground of the pot or use a fixed resistor to ground instead of the pot.

A 25k pot with a 1k on the wiper gives you a line out range of 0R to 1150R with a 47k reisistor in series to the OT tap could work nicely. I already drilled an amp for this so I hope to do this very thing soon as well.

[Reeltarded]

Jah! Thinking a pair of switchable caps to the junction of the resistors after a 50kL pot to pick two ranges and have variable roll off. I still need this thing in an attenuator for wveryone else's ease and my piece of mind.

[surfsup]

Ive not done the line out yet but the schemo I re-posted seems to do a 50% ratio to zero. If significant voltage is there, 50% of that might overload whatever is being used as a amp/reamp. It seems a bit too much for his amp now that i think about it...I guess this all depends on how much voltage is being sent out of the amp or if you plan to use it for many different amps like in an attenuator instead of the amp. Hmm maybe a 47kR -> 25kpot||2k7 would be better at about a 5% ratio from 0-10 on the dial. So an amp sending out 20V would send out 1V max on the lineout...30V would be 1.5Vmax

[Reeltarded]

Exactly! My purpose could use a range switch, a roll off select, level and cap select too. Like 10 parts. This should be in every amp anyhow.

To the Batmobile!