Effects loop

[Leif H]

I'm trying to find a point to point amp that has an effects loop. I've searched the forms and haven't found any threads with this subject, so I know that someone will point out the one thead I missed.

I like to use delay, just a hint, and have given it some thought to putting in an effects loop in a 5E3 or a Vox AC type.

I'm wondering if I split the input to the Phase Inverter at the Coupling caps

I don't want to get into needing transistors or FET's that I've found in new production amps.

Any advice would be appreciated.

[Chuck H]

I'm not clear on what you mean by splitting the input to the PI. As for FET's and such, there's no rule that says you must use a SS device as your amplifier in an effects loop. You do need an amplifier though because you need to "pad" the signal down late in the preamp (to about 1 volt AC signal with the amp at full tilt) when it is typically too high voltage for most effects. Then you "send" to the effects loop and re-amplify to the voltage you had before you padded the signal. Effects loops are typically placed right behind the PI in the signal chain.

With a 5e3 type amp you could limit your circuit to one channel (though a 5e3 is really about the interactive channels) and use the other channels triode as the re-amp stage or you need to add a tube (or transistor) to re amplify the signal. My most recent design has an effects loop and is a PTP amp. Here is a layout:

[Wilder Amplification]

What's wrong wtih FETs? I sell and use the Steve Miller designed SDM FX loops in my amps. They're tonally transparent...it absolutely WILL NOT color your tone. It uses high voltage N-Channel depletion mode DMOS FETs that operate off of the amp's B+ rail (devices are rated for 500V drain-source voltage). Because of this, they are capable of reproducing the full signal swing at the recovery stage without clipping/distorting the signal.

[Enzo]

Why does the amp need to be point to point? If you just want to steal the circuit, what does it matter how it is assembled? Loops circuits are simple, if you find one made on a dreaded circuit board, it would be simple to recreate it on a terminal strip.

With that in mind, look at Fender Pro Tube models like the Pro reverb or the Twin Amp, or the Supersonic, or the Vibroking Custom. Or even the Peavey 5150, B-52 AT100,