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Author Topic: ISP Decimator settings  (Read 7359 times)

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rickeb1

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ISP Decimator settings
« on: Time Format »

I know that there are at least a few of us using an ISP Decimator ProRackG, so hopefully someone can help with this question.  Assume the signal chain is as follows:

Guitar (passive pu's)-> ISP Ch.1 input -> ISP Ch.1 output -> MP-1 input
MP-1 loop send -> ISP Ch.2 input -> ISP Ch.2 output -> MP-1 loop return

First, is this the best chain to use to incorporate the Decimator?  Second, the ISP has buttons for setting +4/-10 db on each channel.  Given the above signal chain, which setting (+4 or -10) should each channel be set to?

I've played around a bit with all the values and it didn't seem to make a big difference, but to be honest, the +4/-10 thing has always been a source of confusion for me, so I'd like to know the correct way to set it.

Thanks!

~ Rick
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MarshallJMP

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Re: ISP Decimator settings
« Reply #1 on: Time Format »

I use mine a bit different,don't use the loop but out A,so Out A to ch2 in and cha2 out to my effects.
I st the cha1 to -10dB and cha2 to +4dB.But you are correct,it doesn't seem to make much difference.
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GuitarBuilder

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Re: ISP Decimator settings
« Reply #2 on: Time Format »

I've got the Stereo Mod version of the ISP Decimator Rack Pro.  I think it's better suited for interfacing with ADA units, because I don't need to use the effects loop.  Here's my setup:

Guitar > ISP Guitar In
ISP Guitar Out > MPx In (I use the Lehle 1at3 to split into three MPs)
MPx Main Outs (L + R) > ISP Inputs (Ch1 + Ch2)
ISP Main Outs (Ch1 + Ch2) > Microtube 200 Inputs (L + R)

Diagram is attached.
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MarshallJMP

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Re: ISP Decimator settings
« Reply #3 on: Time Format »

Well i also have the stereo version but i prefer to use it in dual mono setup because i feel it works better that way.
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GuitarBuilder

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Re: ISP Decimator settings
« Reply #4 on: Time Format »

Well i also have the stereo version but i prefer to use it in dual mono setup because i feel it works better that way.

Interesting!  How does it work better?
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MarshallJMP

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Re: ISP Decimator settings
« Reply #5 on: Time Format »

It seems to work a bit faster and since i'm a high gain player i don't have to worry about getting feedback.In stereo mode it was more sentive to feedback which is normal.In dual mono you first cut the guitar signal and second (in my case) the mp-1 signal.So the gate won't open so fast and will less sensitive to noise gate chatter.
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GuitarBuilder

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Re: ISP Decimator settings
« Reply #6 on: Time Format »

It seems to work a bit faster and since i'm a high gain player i don't have to worry about getting feedback.In stereo mode it was more sentive to feedback which is normal.In dual mono you first cut the guitar signal and second (in my case) the mp-1 signal.So the gate won't open so fast and will less sensitive to noise gate chatter.

Sounds logical!
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rnolan

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Re: ISP Decimator settings
« Reply #7 on: Time Format »

Hey Rick, the -10dbu and +4dbu are for different signal level sensitivities. -10 for inst levels (as they are much lower than line levels, the input circuit is more sensitive (level wise, like mic levels, millivolts)), the +4 is what is considered line level for most devices, designed to take  ~1v so the input is less sensitive and can handle higher level signals without distorting/overloading.  Many input stages handle both without too much trouble (but depends). It's all about getting the gain structure right so there is the best signal to noise ratio.
So with your ISP, as MJMP uses his, the input is set to -10 to handle (provide more gain) the lower inst level signal, as the MP1 A out he uses into chan2 is line level, he sets that to +4.
In the loop you can adjust the loop control to be inst or line level, it's a dual ganged reversed pot so turning up the send turns down the return (as both send and return are controlled by that pot (which is 2 pots working in opposite directions to one another)). The advantage of having it in the loop is the output stays stereo. MJMPs setup uses just MP1 A out then feeds it on to other stuff so is mono at this point.
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rickeb1

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Re: ISP Decimator settings
« Reply #8 on: Time Format »

Thanks for all of the info, guys, I appreciate it!

~Rick
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rickeb1

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Re: ISP Decimator settings
« Reply #9 on: Time Format »

Quote
I use mine a bit different, don't use the loop but out A, so Out A to ch2 in and cha2 out to my effects.

I just rewired things using JMP's approach, and it sounds much better than using the loop, far less tone loss (in fact, almost none).  Thanks for the tip!

~Rick 
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MarshallJMP

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Re: ISP Decimator settings
« Reply #10 on: Time Format »

Ok that will be 500$ for the tip  :lol:
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