DC Loop Mod to Serial Anyone?

I meant to try this the last time my amp was apart and forgot so before I bother has anyone done the mod on a DC series amp changing the parallel loop to a serial? It's simple enough but what do you gain? If for no other reason it seems it may keep things simpler if you have other amps with serial loops and like to use the same effects with all. For me, I have to adjust my effects when going from one type loop to the other. Main question is, does it sound better?

Parallel loops are superior to serial ones, in that they retain a big part of the original signal (all-tube, so to say). Serial means squeezing your tube-tone through tiny effect boxes with (cheap) analog-digital-analog converters powered by 9V batteries.
All you need to use the parallel loop effectively is an effect which lets you choose 100% wet, then you mix 10-20% to the original signal. Voilà! Only if you want to use a noisegate or EQ in the loop you need a serial one. But then you have all the drawbacks I described above.

tetsubin said:

Parallel loops are superior to serial ones

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Well, thats your opinion. There is truth to shying away from putting cheap units into a serial loop, but with the modern electronics we have available to us there are plenty of uses for a serial loop where it will perform far better than a parallel loop.

The rule of thumb should really be, use a parallel loop with crappy effects and use a serial with decent ones. But then again, thats my opinion too.

to keep a balance here, I have no opinion.

GIG4FUN said:

to keep a balance here, I have no opinion.

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Oh come on Gig4fun. Add to the controversy! Your probably thinking that only pussys have parallel loops ain't ya and all the pretty people use serial. Or is it the other way around? :twisted: I need to read my memos more often.

Any more info on this? I've been reading about the mod on other MBs but I haven't come across anyone doing the mod on a DC.

I was trying to use a DOD Bi-FET (junk, I know, but I had it laying around) as a clean boost for leads and it does what I believe is the weird oscillation thing that I've heard happens on some digital effects in a parallel loop. It doesn't happen with any of the other pedals I've tried in the loop (Boss DM-2 & DOD FX40B EQ). Anyway, I'm thinking of doing the serial to parallel mod to use the Bi-FET. I'll put a switch in so I can change between them though.

I guess what I'm asking is why would the Bi-FET have this problem and has anyone actually done the mod to a DC?

1. The Bi-FET was probably designed to be used in front of the amp and not with the levels coming from the loop send. You can't just throw any pedal in the loop and hope for great results.

2. You have to understand the parallel loop: If there's any original signal fed back into the loop you'kk get phasing issues because the fed back signal will be slightly delayed compared to the other (w/o fx) parallel tone stream. It works great with any pedal that can give you a 100% wet output. Then you just set the loop mix to something around 20% or however lound you want to hear your effect.

3. So I'm not telling anyone to not get it modded. Serial loops are mandatory for EQ, noisegates etc. If you wanna use those pedals in the loop I recommend to get a serial loop. But you'll have to be clear what you are losing: the advantages of a parallel loop. A switch from serial to parallel or even two loops (like the newer Mesa/Boogie amps) would be the best option.

4. BUT what I'm saying is probably this: Many problems with parallel loops result from people not getting their knowledge right before fussing around with them - which results in giving parallel loops a bad name. As if they were a cheap or even dumb thing in themself. They are not.

You could get a Suhr Minimix which makes any series loop parallel. Or a line mixer.

Minimix: http://www.suhrguitars.com/tonetools.aspx

tetsubin,

You are probably correct about the Bi-FET being designed to go in front. I just found it strange that a clean boost (preamp) pedal would have enough delay to cause a problem.

My Studio Caliber does not have the GEQ and I would really like to add one in the loop and when I tried last night with the cheap DOD FX30B it did allow me to have more control over the sound but there was a slightly odd sound to it that I was contributing to having a little bit of the 200hz that I was cutting with the GEQ being passed though the parallel loop.

I also would like a clean boost and everything I've put in front of the amp colors the sound (distortion/overdrive) along with the volume boost.

From what I've read and the schematic it looks like a simple mod. I just need to add a switch in one wire going to the loop mix knob.

I didn't know that some MBs now have 2 loops. That seems like a real good idea and I may good that route instead of the switch, although most of what I have laying around that I wold like to use in the loop are somewhat vintage (read no wet only signal) I'm not sure it's worth it for me.

Yeah, in the end it all boils down to a non-technical question: what pedals/effects do you want to use? The strange sound you heard with the EQ wwere probably phase cancellations. Even analog pedals will delay the signal ever so slightly and cause them in a parallel loop which mixes the two signals.
So if you want an EQ in the loop you ain't got no other option then getting a serial loop. But I'd make sure to buy a good EQ because the section between preamp and poweramp is very sensitive. I would always have a strange feeling using a 9V powered pedal in a serial loop - or even one with ADA-converters that digitalize my "all tube" Mesa signal.

P.S.: I might be wrong with newer Mesa amps having both parallel and serial loops - I thought I had seen that feature. But the Diezel VH4S has both for sure.

Here's what Peter Diezel has to say about both loops (from the VH4S manual):
"3.2.3 The Returns: Parallel or Serial?
Which is better for you? Read on.
There are 2 ways to handle effects signals. If you use the serial return, then the signal path of your VH4 is interrupted, the signal is sent to the processor, gets more or less processed, then sent back to the serial return into the power amp. Digital effects units often digitize this signal, then process it, then convert it back to analog, then send it to the amp. This is called ADA conversion. It is necessary for digital effects units to do this to your guitar signal, so that it becomes a digital code which the processor can read and understand. Your tubes, however, need a old fashioned analog signal, so the processor needs to convert the signal back to analog before it goes back to the amp. Generally, even in highest quality effects processors, this causes a change in the original signal, typically a loss of tonality and warmth, also noticeable as a “harder” sound. When you use the serial loop for an effects unit like this, then your signal will have been ADA converted at least once. Tone junkies and vintage freaks alike will more than likely have hives developing by now. But - as always, there is a better way. Use the Parallel loop and the mix control in the front determines how much effect signal is being added to the original signal, which now still flows through the amplifier. There is always an analog connection between the send and return jacks; a parallel loop!
Important: You must set the mix control on the effects unit to 100% wet when using the parallel loop. Otherwise there will be nasty phasing problems resulting in unsatisfactory tone. The signal portion that is unaffected by the mix control in the effects unit would reach the amplifier at a different time due to the cabling, and cause phasing cancellations."

If anyone is interested I have directions, simple diagram and hand written instructions, for changing your parallel to series loop for the DC-5. I haven't done it but it is very easy. I have it in a pdf so unless you have a better way I can email it to you. If you know where I can post it I'll just do that.

Thanks for the diagram MJ!

I just did the mod on my Studio Caliber (DC-2 even though it doesn't say in on the front) but installed a switch so I can switch to the parallel loop if I want to. It worked great. The problem with the Bi-FET and weirdness with the EQ are gone. My delay also sounds MUCH better (smoother if that makes sense).

I was also pleasantly surprised that my cheap the DOD Bi-FET and DOD EQ aren't TOO noisy. Actually the B-FET is pretty quiet but the EQ is a bit noisy. I'm going to pick up a GE-7 and do one of the Allum mods to quiet it down. It seems no one has any mods to quiet the old DODs (not surpising) and I don't feel like testing piles of ICs, etc, myself.

stoneattic said:

Thanks for the diagram MJ!

I just did the mod on my Studio Caliber (DC-2 even though it doesn't say in on the front) but installed a switch so I can switch to the parallel loop if I want to. It worked great. The problem with the Bi-FET and weirdness with the EQ are gone. My delay also sounds MUCH better (smoother if that makes sense).

I was also pleasantly surprised that my cheap the DOD Bi-FET and DOD EQ aren't TOO noisy. Actually the B-FET is pretty quiet but the EQ is a bit noisy. I'm going to pick up a GE-7 and do one of the Allum mods to quiet it down. It seems no one has any mods to quiet the old DODs (not surpising) and I don't feel like testing piles of ICs, etc, myself.

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Does the mod to Parallel give the loop more headroom?

robredo_mattila said:

Does the mod to Parallel give the loop more headroom?

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I'm not quite sure what you're asking. But when the switch is in parallel mode it sounds exactly the same as before, at least as near as I could tell. In serial mode I didn't notice any additional headroom or change in volume between that and the parallel mode. In fact with the pedals bypassed I couldn't tell which mode I was in. Of course I wasn't really listening for that, just how the effects worked in serial mode.

robredo_mattila said:

Does the mod to Parallel give the loop more headroom?

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It's a mod to serial!

tetsubin said:

robredo_mattila said:

Does the mod to Parallel give the loop more headroom?

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It's a mod to serial!

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My mistake!

:lol: :lol: :lol:

Opinions are like.....


Tetsubin, once you have tried a nice quality effects unit, like the G-Major with a Serial Loop, you will never look at Parallel Loops the same again.

My G-Major sounds really good through my DC's Loops, but when I tried it with an older Tremoverb and a few Heartbreakers, there was just no comparison.

I agree about the cheap effects sounding cheap, but hey, that's what they do.




MJ, please send me a copy of the drawing.

Thanks,
Andy

Well it took me a while to get around to it but I finally did the mod so my loop is serial. I was playing at home the other day with my Xpression MFX in the DC-10's loop and the lack of effect was such that I didn't even want to bring my rack to gigs anymore. I could have set the mix pot up higher but that just reduces the original signal and sounds weaker to my ears. Serial made a tremendous difference. I now enjoy my time based effects and have spent the past couple of days re-tweaking the settings. I don't use cheap effects so I wasn't concerned about going serial. The Stiletto uses serial so why shouldn't my DC!

Bottom line is that I suggest you do the mod if you've been considering it.

:lol: :lol: Good news!

I was thinking of doing this today! Now, I have to!

Monsta-Tone said:

:lol: :lol: Good news!

I was thinking of doing this today! Now, I have to!

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Let me know what you think. I can't believe I waited so long to do it.