PT2399 & BTDR-2 Delay \ Reverb Combo Build Comparison

[Cybercow]

Hoping to learn more about the differences between the "Ancestral Apparition" pcb\schematic by GuitarPCB and the "MoodRing" pcb\schematic by MadBean. By their respective descriptions, both units do essentially the same thing - Delay & Reverb.
I've not built either yet, but am considering one of them for my next build. The following points are supplied to support the discussion\questions.

1)  Both designs employ the PT2399 and the BTDR-2H medium as the primary devices to incorporate 'delay' AND 'reverb'. And, they both use a quad opamp; however, the "Ancestral Apparition" appears to use one of the opamps for VB stabilization, but the "MoodRing" uses all 4 opamps in the signal path. (Note the fourth point below please.)

2) The "MoodRing" calls for 88 components, where the "Ancestral Apparition" calls for only 52 components. This suggests the "Ancestral Apparition" will cost slightly less to build.

3) The "Ancestral Apparition" does not sum the BTDR-2's outputs, using only output #2; whereas the "MoodRing" sums the BTDR-2's outputs. Is there an aural difference between summing those outputs as opposed to not?

4) The "Ancestral Apparition" utilizes two 78L05 (5v, low current - 100 mA) voltage regulators, but the "MoodRing" calls for a single 7805CT (5v 1A) voltage regulator. On this point, I'm unsure which is the superior design when taking into consideration opamp utilization referenced in the first point.

5) The "Ancestral Apparition" employs the non-inverting input of the opamps for the signal pathing but the "MoodRing" uses the inverting inputs. I'm curious about the explanation of the difference on this point. Might it just be a means of reducing the component count? Or is there some other inherent difference?

6) The "MoodRing" places a pair of "clipping" diodes at the input of the BTDR-2. The "Ancestral Apparition" does not have these "clipping" diodes. Are the diodes intended to add a bit of "dirt" into the signal?

7) Both units employ a "tone" control AFTER the effect processing. Would the control of the "tone" be cleaner if the tone control were placed BEFORE the effects processing? Or what about adding a pre-tone control before the effect processing in conjunction with existing tone control design?

I'm just thinking out loud here and hoping someone has some insight and\or experience with (either of) these two builds.

Lastly. . . What other similar PCB's might be available that utilize both the PT2399 and BTDR as primary devices for a Delay\Reverb combo build?

Thank you for your time and consideration.

[samhay]

Hi, and welcome to the forum.

Can you include schematics to the 2 circuits of interest please?

>What other similar PCB's might be available that utilize both the PT2399 and BTDR as primary devices for a Delay\Reverb combo build?

http://www.diystompboxes.com/smfforum/index.php?topic=107226.0
The schematic, etc have been re-posted on the 3rd page of the thread.

[bean]

3 - Summing the outputs is suggested in the application note, IIRC. Is it totally necessary, no, but there's also no reason not to do it unless one is worried about part count.
4 - The BTDR is 3 PT2399 in parallel, so the Moodring has a total of 4 PT2399. A 78L05 taps out at 100mA max. It might be sufficient to run the circuit plus the additional op-amps but I thought it better to step up to the 7805 on the MR for more current on tap.
5 - The MR is modeled around a very typical analog delay type design. I personally find the inverted setup easier to mix dry and effect signals than non-inverted.
6 - The LEDs are not used to create dirt - they are to clamp the signal going into the PT2399 and BTDR when the Dwell pot is set very high to prevent oscillation.
7 - The MR has a pre-emphasis filter going into the delay and reverb section, but I think you make a good point that an actual tone control going in could be beneficial.

Last thing - the MR "delay" section is less an actual delay but rather used to simulate room size. IOW, the very modest amount of delay you get from the PT2399 can be used to change how long it takes the reverb to 'reflect'. But, you could increase the amount of delay time available by increasing the pot from 10k to 25k or 50k. However, you are also going to encounter more noise with the longer delay times.

[Cybercow]

samhay - Thanks for the greets. Here are the schematics for each . . .

And that "Space & Time" verb unit appears tasty. I've not yet examined the schematic, but will soon. Thanks!

[Cybercow]

Brian - thank you for the detailed response(s). As an experienced bench-tech, everything you said makes perfect sense. Thank you for taking the time.

(I'm also the fellow who emailed you about the MoodRing pcb.)

Regards,
Mark Davis

[Cybercow]

Sam, Brian - I must say, each of your designs are admirable. Love 'em both. I particularly like the "tails" feature of the "Time & Space" build with the soft-switching option. While the "Ancestral Apparition" is the simplest of the three options thus far, I'm more likely to go with more complexity for a finer level of control.

Questions for Sam: Does the "PIC12F675P" require "programming" before use in the "Space & Time" build? And, is there a PCB for your "Time & Space" build available?

Questions for Brian: Based on how I'm interpreting the "Mood" control, does it also adjust the "tone" as well as the amount of reverb - or just "Reverb"? Is "tone" a control that will be going into your 'deluxe' version?

Thanks guys. Awesome work.

[samhay]

>samhay - Thanks for the greets. Here are the schematics for each . . .

Thanks, but http://endprod.com/schematics/... seems to redirect to a disney page.

Here's the build documents.
http://www.guitarpcb.com/PDF%20Files/Ancestral%20Apparition.pdf
http://www.madbeanpedals.com/projects/Moodring/Moodring2015.pdf

>Does the "PIC12F675P" require "programming" before use in the "Space & Time" build? And, is there a PCB for your "Time & Space" build available?

Yes, the PIC would need to be programmed, but you could build the simpler version, which uses a physical switch in place of the microcontroller and relays.
No, there is no PCB. However the perf layout could be easily converted to an etchable PCB layout.

In any case, I hope this design gives you a few more design decisions to mull over.

p.s. the Mood control in Brian's Moodring is a tone control. It uses the same approach as the Big Muff Pi tone control.
For more reading, try: http://www.muzique.com/lab/tone3.htm

pps. Re summing the BTDR outputs. The two outputs from the BTDR are taken from different points in the circuit, thus they are not identical. As a result, I would advocate summing them in preference to leaving one disconected. An even better option can be to build a pseudo stereo reverb if you have any interest in a stereo rig.
e.g. http://www.diystompboxes.com/smfforum/index.php?topic=115955.0 (I will re-post the schematic, etc).

[Cybercow]

Sam - thanks for all the great tips. I have the PDF's for both of those builds, I was just trying to post the converted JPG files on my site. Apparently, I was in a hurry and somehow fouled the links. 

And, yes, I am interested in (and use) a stereo rig, so my build will ultimately have stereo outputs. I'll likely build mine with smart output so it will know only the LEFT output is plugged when using only one output.

Cheers!