Its been a year since posting the first attempt at a Parallel Loop.
The original design goal was
1) In serial mode - as close to the 'original' schematic as possible
2) In Parallel mode - as transperent as possible AND unity gain.
I've done a lot of back and forth and have worn out a couple of wall-to-wall carpets
And if you compare the old and updated schemo, you will notice that the circuit is slimmed down to equal the original dumblelator.The reason for the updated loop, is a desire to build an all-in-one amp head, with built-in loop + a small effects processor (SE70) in the bottom of the cabinet. Hence, all you have to do is connect guitar and speaker cab and off you go.
1) Serial mode is now identical to the regular dumblelator.
2) Parallel mode is trimmed to equal the frequency curve (not the compression) of serial mode, which has a slight mid boost and a slight 12KHz roll off as documented by Glasman in this post: http://ampgarage.com/forum/viewtopic.ph ... sound+loop
Built-in loop - If you decide to do a built-in the loop, you might what to add cable simulation capacitors of 150-200p at the input and at the output. If so, don't forget to add a 47-68p capacitor to the master volume. This is not an easy task, it takes LOT of experimentation to get it right. Just make a search for post by Dogears or Glasman regarding this topic.
Stand-alone loop - If you already have a regular dumblelator, you can add a switch and two resistors+ to caps in order to get parallel operation.
This version of the parallel loop is the best, I can come up with. However, in parallel I miss the compression and must agree with Dogears and others, that you don't get the compression and that the bass notes are different when using a (Kevin O'Conner (KOC)/ Aiken inspired) parallel loop like this one. Therefore, I have ordered a Suhr Minimix2 (inspired by a lot of you guys), in order to test if the regular Dumblelator series mode with the addition of the minimix2 is the ticket to parallel operation (with compression)
Let me hear the verdict if you decide to give it a go.
Happy to share with y'all (but don't nick it NIK)
