Non-switchable series effects loop

[shane]

Hi Folks

Can anyone recommend a good non-switchable active series effects loop for a D'lite type amp?
I have someone who wants a D'lite type amp (albeit a 100W 4x KT88 type!) and he wants a non switchable series effects loop ie it will be in all the time.

I looked at the Dumbelator circuit which is cool but, there seems to me to be an awful lot of pots in the chain for a non switching loop! master, send level, return level... all affecting the output into the PI. is there a simpler loop anyones tried successfully?
Cheers
Shane

[Fischerman]

FWIW - the way I usually do it in other amps (just starting my first ODS) is to have a Master Volume for the Lead (dirty) channel and I label it 'Lead Master'. It's purpose is soley for matching the level with the clean channel (usually I don't have a 'Clean Master' but my ODS prototype will). Then I have a Send Level control but that usually stays set at a particular setting...so it usually goes on the rear panel of the amp. But if I changed to rack effects or something I will be glad I have the Send Level control. Then I have a Return Level control but I just label it 'Master Volume' (and put it on the front panel) because that's really how it works from the user's perspective.

So IMO/IME:
1. You'll want at least a Lead Master Volume for the dirty channel so you can match the level with the clean channel...Clean Master is optional depending on the amp.

2. You'll want a Send Level control because you (or someone else down the road) might change effects and they might be sensitive to input levels. You don't want to clip anything (too hot) but you also don't want to screw your S/N ratio (too low).

3. You'll want a Return Level because it determines how hard your PI gets hit and behaves just like a global Master Volume.

If you wanted to eliminate one I would just experiment with fixed resistors for the Send Level and just hard-wire it such that it works with the effects you intend to use. You can always go back and swap a resistor or two if you change to rack effects or whatever. This is basically the way the Send in the SLO is done...just a couple parts changes to change the Send Level.

As far as which loop...there are several in the Files section or other threads here. The loop I usually use is very similar to the loop in a Mesa Dual Rectifier...but I'm gonna start off with the Dumbleator first in my ODS build.

[shane]

Thanks Fischerman, good advice.
I was thinking, looking at the Dumble Master placement, that I could use the Dumbelator circuit but either lose the master(and call the return level in the Dumbelator, the master)

Or keep the normal Dumble master where it is and use it to control the send level and lose the send level control while still using the return level as master.

Theres already a level control at the end of the OD section which should let me balance the levels between clean and OD.
what do you think?
Shane

[odourboy]

I think.. if it an't broke, don't fix it. You taking about messing with the work of the Master (pun intended).

The master volume, for instance, isn't JUST an attenuator that you can yank out of the circuit for the sake of gettig rid of a knob. It's a part of an RC network whose value has been selected in consideration of circuit capacitance to form a filter. Pull it out of the circuit and you put your tone at risk.

My 2 cents.

[shane]

You do have a point and I am certainly very reluctant to mess with a circuit thats so critically well developed.

To be honest if I lost a pot I think it would be the send level!

I may well just build in the Dumbelator and make the loop switchable then leave it to the customer to choose wether he switches it in/out or leaves it in premanantly, just to make my life less full of hard decisions
Shane