Impedance Akai MPC Live 2 Inputs

[trash116]

Hi
Any help on this would be appreciated - I always get confused with this type of thing...

I have an AKAI MPC live 2, I am going to use output 3 to route some sound out to an external effect (guitar effect - Chase Bliss "Warm Vinyl Mkii), and then route it back from the the effect pedal to the input of the Akai Live 2.

I've seen this done on youtube with different pedals - so presume I'm ok to just dive in and do that.... or do i need to worry about levels & impedances.

The out from the MPC is line level, I guess the pedal is all instrument level & the input impedance of the pedal is 1M and the output impendance is less than 1K.

These are the stats of the MPC input:
Line Inputs
(2) balanced
1/4” (6.35 mm) TRS
Dynamic Range 113 dB (A-weighted)
SNR 108.5 dB (1 kHz, +4 dBu, A-weighted)
THD+N 0.001% (1 kHz, +4 dBu, -1 dBFS)
Frequency Response 20 Hz – 20 kHz (+0.0 / -0.1 dB)
Maximum Input Level +16.5 dBu
Sensitivity -13 dBu
Gain Range 29.5 dB

Will i be able to just run an unbalanced cable from the MPC to the pedal and back out into the input of the MPC without worrying about impendance and reamp boxes etc (which i dont really underdstand).

Thanks in advance & sorry if this is an obvious question
M

[Mike Stranks]

No need to apologise... the whole line/inst/mic level thing and impedances causes a lot of people to scratch their heads..

The key thing is you've asked and not just assumed or guessed!

From the specs you've given you'll be fine.

In very simple terms, high input impedances and low output impedances for line levels are what's needed... and that's what you've got. In fact any input impedance should be significantly higher than the output impedance of what's driving that input.

That's a very high level summary and doubtless some of my more technically oriented brethren will be along with "Ah! Yes; but...' qualifiers that add more substance to what I've said.

[James Perrett]

The only thing to watch out for is the level that you send to the pedal. If the pedal uses a typical 9V power supply then it won't handle a full line level but, provided you keep the level down you'll be fine. You'll probably need to turn the input level up on the MPC too.

[trash116]

@James Perrett @Mike Stranks - thanks for the replies.

I've been having a play with doing what i suggested and took note of your advice on volumes.

The results haven't been great... the signal back from the pedal (which is 9v powered) into the line input of the MPC is very quiet (too quiet to be useable) and it also seems noisy (not very clean).

I'm not sure what to do - does anyone have any ideas?

Somebody said this would do the trick:
Radial EXTC-SA Guitar Effects Interface and Reamp Box---- would it? but it's £289 and wondered if there was a cheaper solution?

I have an old Warm Audio WA12 MK1 mic pre-amp - could i run the signal out from the pedal into this then into the line input on the MPC? would this be a good idea to boost the volume? (would i need to engage the HI-Z switch on the pre-amp?)

Sorry for the questions, and thanks for the replies so far,
M

[Hugh Robjohns]

The results haven't been great... the signal back from the pedal (which is 9v powered) into the line input of the MPC is very quiet (too quiet to be useable) and it also seems noisy (not very clean).

I'm not sure what to do - does anyone have any ideas?

The Akai expects to work with balanced line-level signals (nominally +4dBu), while the effects pedal expects unbalanced instrument level signals (nominally -20dBu).

So, you are going to have to attenuate the output from the Akai before feeding it into the pedal, to avoid overload, and boost the level from the pedal going back into the Akai. I'd have expected the Akai to have enough gain range to do that, but presumably you've tried that and it's still insufficient. You'll also need to handle the balanced-unbalanced-balanced format conversion. Impedances aren't an issue in this situation. All outputs are low impedance and all inputs reasonably high impedance, which will work just fine.

Somebody said this would do the trick:
Radial EXTC-SA Guitar Effects Interface and Reamp Box---- would it? but it's £289 and wondered if there was a cheaper solution?

Yes, that would almost certainly do the trick, but as with all Radial gear, it's beautifully made and will last a lifetime, but also scarily expensive.

A few folks around here use the ART Cleanbox Pro which costs around £60. It does the same basic job, except that it uses RCA-phono connectors (intended for domestic hi-fi equipment) rather than quarter-inch sockets for instruments. However, they work at the right kind of level, and with the unbalanced format you need, you'll just need adapters or RCA-phono to quarter-inch TS plug cables to hook up your pedals.


https://artproaudio.com/product/cleanbo ... converter/

The CleanBox Pro converts the format in both directions -- to and from the effects pedal -- with a volume control for the return signal to control the amount of boost needed. And it has two channels for stereo effects, or two separate effects chains.

NB. There also an ART product unhelpfully called the 'Cleanbox' (no 'Pro') which is passive and doesn't provide the level shifts you require. Don't get them confused!

I have an old Warm Audio WA12 MK1 mic pre-amp - could i run the signal out from the pedal into this then into the line input on the MPC?

Yes, using its DI input for the pedal output.

would this be a good idea to boost the volume? (would i need to engage the HI-Z on the pre-amp?)

Yes and yes.

But it doesn't deal with the problem of getting the balanced line output from the Akai down to a format suited to the pedal. In your position, if you're happy to use the WA12 for the return signal, I'd ignore the suggestion above for the Cleanbox Pro and instead just buy an Orchid Electronics Amp interface to re-format the send signal.

http://orchid-electronics.co.uk/Amp_Interface.htm

It's passive, so no need for a power supply and the associated grief. It's built very solidly, performs superbly, and I use one all the time. Highly recommended. It will cost around £56 and, like the Radial box, it will last a lifetime. I reviewed it here:
https://www.soundonsound.com/reviews/or ... -interface

Sorry for the questions

The forum exists to answer questions. No need to apologise.

[trash116]

@ Hugh Robjohns - thanks for such a speedy and thorough response.

Point taken about apologising, but i do have to say sorry for the length of this post....

I think not using the WA12 for the return signal is my preference - so the ART Clean Box Pro looks like a good value for money option.

I am abit confused by the ART Clean Box Pro though - i've looked it up on the internet - but my lack of general knowledge in this area has led me to be confused... could you help me understand it.

You said it works in both directions to/from the pedal.... is my thinking below correct....

(1) MPC to Pedal
Using a 1/4inch balanced TRS cable with one end XLR, I would run that from the MPC to one of the ART's +4dBu BALANCED IN 1 & 2 female XLR connectors(it's a Mono Pedal i'm using).

Using a RCA to 1/4inch unbalanced TS cable, I would run that from the ART's -10dBV UNBALANCED OUTPUT 1 & 2 RCA connectors to the pedal.

I'm guessing this would turn the signal from balanced to unbalanced?

Would it change the signal from line level on the MPC to the instrument level needed by the pedal? or do you just use volume control on the ART to get a good signal by ear?

(2) Pedal to MPC
Using a RCA to 1/4inch unbalanced TS cable, I would run that from the pedal to the ART's 10dBV UNBALANCED INPUT 1 & 2 RCA connectors.

Using XLR to 1/4inch balanced TRS cable I would run that from ART's +4dBu
BALANCED OUTPUT 1 & 2 male XLR connectors to the MPC inputs.

I'm guessing this would turn the signal from unbalanced to ubalanced?

Would it change the signal from instrument level from the pedal back to line level for the MPC? or do you just use volume control on the ART to get a good signal by ear?

-- If my interpretation above of what i've read on internet then that box is exactly what i need like you said Hugh?

Out of interest if my understanding above is right and it does do what i need - it seems great value (and more in my budget than the radial). But i did wonder what makes the Radial EXTC-SA Guitar Effects Interface and Reamp Box so much more expensive?

Thanks
M

[Hugh Robjohns]

(1) MPC to Pedal
Using a 1/4inch balanced TRS cable with one end XLR, I would run that from the MPC to one of the ART's +4dBu BALANCED IN 1 & 2 female XLR connectors(it's a Mono Pedal i'm using).

Using a RCA to 1/4inch unbalanced TS cable, I would run that from the ART's -10dBV UNBALANCED OUTPUT 1 & 2 RCA connectors to the pedal.

I'm guessing this would turn the signal from balanced to unbalanced?

Yes. Balanced to unbalanced and attenuated by around 12dB. Obviously you'll only need to use one channel for your mono pedal.

Would it change the signal from line level on the MPC to the instrument level needed by the pedal? or do you just use volume control on the ART to get a good signal by ear?

Yes, its a fixed amount of attenuation. The volume control only affects the return signal.

(2) Pedal to MPC
Using a RCA to 1/4inch unbalanced TS cable, I would run that from the pedal to the ART's 10dBV UNBALANCED INPUT 1 & 2 RCA connectors.

Using XLR to 1/4inch balanced TRS cable I would run that from ART's +4dBu
BALANCED OUTPUT 1 & 2 male XLR connectors to the MPC inputs.

I'm guessing this would turn the signal from unbalanced to balanced?

Would it change the signal from instrument level from the pedal back to line level for the MPC? or do you just use volume control on the ART to get a good signal by ear?

Yes, it converts from unbalanced to balanced and boosts the level from instrument to line, with an adjustment control if needed.

Out of interest if my understanding above is right and it does do what i need - it seems great value (and more in my budget than the radial). But i did wonder what makes the Radial EXTC-SA Guitar Effects Interface and Reamp Box so much more expensive?

The Radial has better quality circuitry, better construction, specific facilities for the application, is intended for a niche market, and is made in small numbers in Canada. And it says Radial on the front!

The ART is a generic interface for hooking domestic equipment with professional consoles etc, and mass produced in China.

[Humble Bee]

There is also this 4 channel unit from TK Audio:

https://tkaudio.se/portfolio-items/transceiver/

They have also made a one channel unit in the 500 series format iirc.