Ibanez DE-7 mods thread

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DWBH
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Post by DWBH »

I really really like this delay. The echo mode sounds brilliant. There's a couple of mods though that might interesting to do on this one:
- the old 'trails' mod
- a tone pot for the repeats
- maybe an fx loop.

Here's the (pretty hard to read) schematic:
http://www.ibanez.com/parts/2004_PARTS/ ... DE7-01.pdf

Trails mod
The flip flop circuit kills two signals. One that goes from the compander to the delay chip, and the delayed signal itself. Schematic wise, we're looking at the R33/D5/D4 junction. Killing just the first signal, leaving the delayed one intact, should work - so, keep the base of Q6 LOW at all times - lift D5?

Tone pot for the repeats
The two modes on this pedal are done by switching a distortion/filter circuit in and out on the repeats signal path.
Image
Echo mode goes through this, delay mode doesn't. Don't really care for the delay mode. I was thinking: potentiometer on R31. Watchathink?

Effects loop on the wet signal
Send/Return jacks before R23 or after R21/R20.
There's some RC filtering after the repeats knob: C23/R21/C31/R20. What do you think about messing with those values? These affect both modes.


Any cool mods you want to share?

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Post by DWBH »

Ran some quick simulations and a 5k pot on R31 seems to do the trick - theoretically at least.
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Post by DWBH »

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Post by the3secondrule »

cool - gotta get my DE7 back from a bro, then I'll def be giving the tails mod a blast

Cheers!

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Post by DWBH »

I'm not sure on it. Currently I'm DE7-less, so I haven't had the chance to try it.

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Post by DWBH »

DWBH wrote:Trails mod
The flip flop circuit kills two signals. One that goes from the compander to the delay chip, and the delayed signal itself. Schematic wise, we're looking at the R33/D5/D4 junction. Killing just the first signal, leaving the delayed one intact, should work - so, keep the base of Q6 LOW at all times - lift D5?
Actually I think it'd be better to bypass Q6 altogether, shunting the drain and source pins, besides lifting D5.

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Post by dlab »

Staying tuned to this one, not sure I care about trails, but I'd be interested in a tone knob and/or FX loop for my DE7...

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Post by kev1n »

Did the trails mod work?????

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Post by DWBH »

I just got a new DE-7, so I can finally mod it :twisted:
However, it'll take a while, since my final exams are just around the corner - and unfortunately transistor flip flops and jfet switching aren't the subject in my electronics course :lol:

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Post by kev1n »

Tried the d5 lift. It works, sorta. About 1 repeat is trailed after pedal is switched off, then they cut off like normal. So we are getting somewhere!

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Post by DWBH »

Try bypassing the jfet, connecting gate and drain together, besides lifting the diode.

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Post by kev1n »

Where is the jfet on the board and how do i bypass it? just snip it? Or jumper?

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Post by kev1n »

Yea, dont mess with q6. i broke my de7.

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Post by digitalzombie »

Any updates on how this is being put into practice? Woke up this morning thinking I had to add an fx loop to the wet signal of my DE7. Plus, I'm still what you would consider a 'freshman' with the internet electronics education 101, so any abilities you might have in keeping speech not AS techy... (At least give me time to Google some of this stuff)

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Post by Yonatan »

I'm also wondering if there was any progress on these mods.

By the way, doesn't this pedal provide separate outs for dry/wet. So couldn't all of these features be accomplished externally (with wasting extra space and equipment)?

Effects loop on the wet signal - Run the two outputs into a blender pedal, and insert whatever effects you wanted in between the wet out and the blender.

Tone pot for the repeats - Same as above, substitute with tone changing effect

Trails - This one's harder, I'm thinking of an A/B box before the input e.g. A->DE7 to engage effect, B->directly into blender pedal to have no effect but still get whatever trails are leftover from the DE7. The only problem is that this now leaves 3 signals that need to be mixed: B from the A/B box, and the two outs from the DE7, unless you can just ignore the dry out from the DE7 and take it always from the A/B box e.g. use A/B together to get both wet/dry, and just B to get no effect but trails. But I don't know if that will sound the same as wet/dry from the DE7.

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Post by kroaton »

I did the R31 mod and I'm enjoying it so far.

I was thinking of adding an LFO to slightly modulate the delay time pot (to get pitch modulation on the repeats) and adding a send-return to be able to use my Magnus Modulus and Whammy in the delay path (to get something like this).

Could somebody help me figure out what the best place would be to insert the send-return jacks in the signal line?

Also, has anyone had luck with the trails mod?

edit: Oh, and sorry for the NecroBump, but I thought it made more sense to continue the discussion here considering the cool information that OP scored.

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Post by loylo »

kroaton wrote:I did the R31 mod and I'm enjoying it so far.
Me too! The little drawback of this mod is that by cutting the treble frequencies, it also alters the number of repeats as the total gain is reduced in the feedback loop..
I am thinkink of one way to use a dual pot in order to make up some gain on IC8 while the other part of the pot is cutting the treble frequencies.
kroaton wrote: Could somebody help me figure out what the best place would be to insert the send-return jacks in the signal line?
You have to break the feedback loop between C14 and R26. In fact I desoldered C14 in order to solder cables from the PCB to the send/return jacks, and put the cap directly on the send jack.
kroaton wrote: Also, has anyone had luck with the trails mod?
Not yet. But I suppose an easy way to this is to solder a SDPT switch in parallel of Q6, between its source and drain, in order to bypass the FET in bypass mode.

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Post by loylo »

loylo wrote:
kroaton wrote:I did the R31 mod and I'm enjoying it so far.
Me too! The little drawback of this mod is that by cutting the treble frequencies, it also alters the number of repeats as the total gain is reduced in the feedback loop..
I am thinkink of one way to use a dual pot in order to make up some gain on IC8 while the other part of the pot is cutting the treble frequencies.
I just had a better idea.
I think the best solution in order to make a tone control is to transform IC8B into an active low pass filter and leave R31 as it is.
It would need to put a 10K lin pot in place of R29, pins 1 and 3 between pin 6 and 7 of the opamp sothat the gain remains constant. And put a cap (10n to 47n) between the wiper of the pot and pin 7 of the opamp.

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Post by kroaton »

That's a neat idea, let me know if you go any further with it.

I'm going to be out of town for a few weeks, so I won't get any time to tinker further with the circuit.

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Post by loylo »

OK, I've developped a global mod in the feedback loop of the Echo Mode (around IC8), which let the user dial the tone and the saturation of the repeats.
The first control consist in a tone pot (I actually used a slider) which doesn't alter much the gain of the feedback loop, sothat the number of repeats keeps pretty much the same wherever the tone control is set. I will soon put a schematic and some simulations, but the mod is basically what I described in my previous post.
The second control (a slider also) consist in clipping the feedback signal a little more, and make it controllable from no-clipping to a good amount of clipping. In order to keep the gain constant (same as above) I had to move the back to back diodes outside the feedback loop of the opamp, transforming the original tubescreamer-like configuration into MXR distortion+ like design.

With these 2 controls, you can alter the sounds into dark and saturated repeats, just like a worn tape echo, or keep a cleaner and brighter analog sound, just like a well-conditionned tape echo or a bdd delay.

I'll post all the informations as soon as possible.

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