Input Level of guitars into Guitar Amps?

[Re-Pete]

I hope some electrically minded folks could help me here with a question... Paging Cagey & Mayfly perhaps?

The input of a guitar amp, where you plug your guitar.... What does it want to 'see' as in input level? Unity gain (0 dB)? +4dB, +10dB...?

Reason I'm asking is I have 3 guitar 'amp' systems..... and I wanna link them up into a wall of death sound. I'm quite aware that if you use a standard A/B pedal that sends out a parallel signal when both employed and weakens the signal (passive pedal). I'm thinking of something like the Boss ES8 but instead of looping up effects, sending the signal of the guitar to the amps on a loop - if that's possible. I think the ES8 can adjust the output level it sends to the loop, and that's got me wondering what the amps actually want to receive...

 

[Sovereign_13]

I think you're after "amplitude".  "Gain" is something else entirely.  When you talk about "unity" gain (or +4dB, etc.), you're talking about the ratio of output to the input of an amplifier.  So a signal coming from a pickup has no "gain".  It's just raw signal.  It does have an amplitude, typically on the order of a few hundred mVpp (that's "millivolts peak-to-peak", which is different from RMS voltage).

When you say you want to chain them together, do you mean you want them all in parallel?  If so, the ES-8 would be a good choice.  What you want is for your splitter to be "buffered" (which the ES-8, and most Boss pedals).  What a buffer does is actively preserve your signal integrity, which helps with long passive signal chains.  You can then adjust the output of the buffered loops so that they match the raw signal from a guitar.

Sorry if I'm being too technical, let me know if something doesn't make sense.

 

[Re-Pete]

I just re-read what I type in firstly. It's all over the place so apologies.

Yes I want to run my guitar through something like an ES8 and instead of switching in or out a pedal loop I want to engage or disengage (isolate) a guitar amp.

But I was wondering what strength a signal comes out of that ES8 Send socket and whether that matched the same strength of signal a guitar amp would normally get...

ES8 is quite expensive and would hate to go down the path of saving for one, only to finally get it and find the loop features can't be used to input into guitar amps. I do have some pedals, but that ES8 has 8 FX loops at your disposal and I'm sure I could link up 3 Loops as guitar amp sends instead.

I suppose I could do more digging on this product save the $$ and insist on a demo at a store before buying,  using amps via a loop instead of the usual Output sockets and see how that sounded... :dontknow:

 

[mayfly]

well,

It's not exactly level that's important in this particular case; It's impedance. Guitars are funny:  they have a relatively high output impedance (say in the order of 20K, depending on the pickups), and most of that impedance is inductance.  Compare this to a dynamic mic which will have 600 ohms output impedance and consequently can drive long cables without much worry.  Anyway, with that guitar lead if there is a resistor of any consequence attached between a guitar's output and ground, it makes a single pole low pass filter.  Too low of a resistance and you can hear the reduction in treble.  This is why folks spend so much time fussing over the value of their volume pots etc.

It's an unofficial standard that any electronic device that's intended to take a guitar or bass as an input has an input impedance of at least 1 megaohm (1M for short).  All your fender/marshall/vox/whatever amps have that 1M input impedance.  You need to have some impedance there, otherwise you'll pull a spinal tap and start picking up radio signals.  But the point is that the established standard is 1M.

Now, if you start linking in several such devices in parallel, you end up with those 1M resistors all in parallel.  This means that the impedance goes down, and the effect on that groovy low pass filter starts to be come noticeable.  If you've got two amps hooked up, then the impedance drops in half to 500K.  Three of them? approx 333K.  Goes down from there.  You can almost feel your top end disappearing. 

So what do you do?  Well, you need yourself a line buffer of some kind.  Essentially it's an electronic device with unity gain, 1M input impedance, and as low of an output impedance as practical (usually a few hundred ohms).  Then you can go nuts and hook up that sucker to as many amp type things you've got! 

Several people make them.  Radial is one.  A quick pass of their website turned up this:

http://www.tonebone.com/stagebugsb15.php

Have fun!

 

[Sovereign_13]

According to the Boss website, if you run the ES-8 with the buffers on you can adjust the signal output level.  What I can't tell is whether or not the buffers are on the "Send" lines or the "Out" lines.

In theory, you should be able to plug your guitar into the input and use the Send lines out to your various amps.  Disengaging a loop would cut off signal to that Send, which would then remove that amp from the equation.  Since you're generally only plugging the guitar into one (or two) jacks, I'm guessing the loops are buffered so you don't have any signal loss when switching between loops.

Truth be told, the only other product I've been able to find that seems explicitly designed for what you want with more than 2 amps is the Radial JD-7, which is 1) a studio-level multi-re-amping rack unit and 2) $$$$.  It would, however, do exactly what you're after with up to 7 amps.  It's a direct-input, line buffer, and signal distributor all in one.

Mayfly's right about impedance, but Boss has you covered there.  The ES-8 has an input impedance of that standard 1M and an output impedance of 1K (less than your typical guitar for sure, but sufficient).  I would expect most signal loopers to be properly designed in order to avoid exactly the problems Mayfly mentioned.

 

[stratamania]

The Boss ES-8 has input and output buffers. The output buffers are on the outs marked output.

You would normally use its so called Volume Loop to insert an amp's preamp into it if you want to run 4CM.

Could you describe what you are trying to connect and the signal path you are trying to achieve?

Someone mentioned parallel, the ES-8 has two mixers and with them, you can run two mono parallel paths simultaneously or if stereo one parallel path of two stereo effects.

Are you wanting to select between different preamps?

If you describe the actual gear you want to hook up and what exactly you would like to do it would make it easier to answer.

Or take a look at the ES-8 manual which you can read online or download.

https://static.roland.com/assets/media/pdf/ES-8_e02_W.pdf

 

[Re-Pete]

The Boss ES-8 has input and output buffers. The output buffers are on the outs marked output.

You would normally use its so called Volume Loop to insert an amp's preamp into it if you want to run 4CM.

Could you describe what you are trying to connect and the signal path you are trying to achieve?

Someone mentioned parallel, the ES-8 has two mixers and with them, you can run two mono parallel paths simultaneously or if stereo one parallel path of two stereo effects.

Are you wanting to select between different preamps?

If you describe the actual gear you want to hook up and what exactly you would like to do it would make it easier to answer.

Or take a look at the ES-8 manual which you can read online or download.

https://static.roland.com/assets/media/pdf/ES-8_e02_W.pdf

OK..

The 3 guitar 'amp' systems I want to hookup are as follows:
1. Kemper Profiler Rack (unpowered)- SP/DIF & audio inputs to audio interface
2. Mesa Boogie Studio Preamp - it's audio output is hooked up to a Palmer PGA-05 active stereo cab sim/DI - from Palmer into audio interface.
3. A valve combo amp - which will run the audio thru a Demeter Silent Box and mic'ed into audio interface.

Now thinking of the ES8 I can run one of these into the usual Output socket....actually two of them as the ES8 has dual outputs...

I think I can adjust the input impedance that the Kemper sees to line level, not sure about that. It's a pretty flexible device that way with it's sockets  assignable a number of ways.

I am hoping for any number of the above amp systems on or off, and be able to assign a couple of pedal loops to them...

Truth be told, the only other product I've been able to find that seems explicitly designed for what you want with more than 2 amps is the Radial JD-7, which is 1) a studio-level multi-re-amping rack unit and 2) $$$$.  It would, however, do exactly what you're after with up to 7 amps.  It's a direct-input, line buffer, and signal distributor all in one.

Mayfly's right about impedance, but Boss has you covered there.  The ES-8 has an input impedance of that standard 1M and an output impedance of 1K (less than your typical guitar for sure, but sufficient).  I would expect most signal loopers to be properly designed in order to avoid exactly the problems Mayfly mentioned.

Been looking at that JD7 for years and it's been similar to what I've wanted....... BUT, there's comment online about their buffers having a 'sound' but that's from sensitive souls on Gearslutz...I doubt it would concern me unless it was horribly unmusical the way a buffer affected the tone. I am a fan of the Radial gear but it's so hard to get here in Australia, and I find myself frustrated looking at their various pieces of gear wishing a product had just one more option or two on it & it would be perfect. In the case of the JD7 there's really only one FX loop.... As I'm looking for a permanent studio setup linking all my pedals & Amps up with various loops that won;t work for the price they are asking. Another product is the GigRig 2, but that's more costly that the ES8 and I'm not sure if that has the parallel FX placement that the ES8 has...

well,

It's not exactly level that's important in this particular case; It's impedance. Guitars are funny:  they have a relatively high output impedance (say in the order of 20K, depending on the pickups), and most of that impedance is inductance.  Compare this to a dynamic mic which will have 600 ohms output impedance and consequently can drive long cables without much worry.  Anyway, with that guitar lead if there is a resistor of any consequence attached between a guitar's output and ground, it makes a single pole low pass filter.  Too low of a resistance and you can hear the reduction in treble.  This is why folks spend so much time fussing over the value of their volume pots etc.

It's an unofficial standard that any electronic device that's intended to take a guitar or bass as an input has an input impedance of at least 1 megaohm (1M for short).  All your fender/marshall/vox/whatever amps have that 1M input impedance.  You need to have some impedance there, otherwise you'll pull a spinal tap and start picking up radio signals.  But the point is that the established standard is 1M.

Now, if you start linking in several such devices in parallel, you end up with those 1M resistors all in parallel.  This means that the impedance goes down, and the effect on that groovy low pass filter starts to be come noticeable.  If you've got two amps hooked up, then the impedance drops in half to 500K.  Three of them? approx 333K.  Goes down from there.  You can almost feel your top end disappearing. 

So what do you do?  Well, you need yourself a line buffer of some kind.  Essentially it's an electronic device with unity gain, 1M input impedance, and as low of an output impedance as practical (usually a few hundred ohms).  Then you can go nuts and hook up that sucker to as many amp type things you've got! 

Several people make them.  Radial is one.  A quick pass of their website turned up this:

http://www.tonebone.com/stagebugsb15.php

Have fun!

Thanx for this info Mayfly. I own a StageBug 6 from Radial that converts the incoming Unbalanced FX signal to a Balanced one (Preamp Bypass FX return for modulation FX like Vibrato/Chorus/Reverb..), into the Kemper. As I've said above, I'm a fan of the Radial stuff but often their products are just one feature shy of being perfect for my requirements.... But that SB6 Isolator is good and the transformer inside does colour the sound, I am sure of it, but it does so musically and can be compensated.

 

[mayfly]

wow - there is no way you need to make this that complex. 

I'm sure that there is some enterprising person in Australia that can make a simple guitar buffer.  I mean hell it's just a single op-amp.

 

[stratamania]

Firstly I can confirm that the Gigrig G2 does not have the ability to do parallel routing. Although it can reorder loops and you can go out to a choice of two amps.

You mention the following:-

The 3 guitar 'amp' systems I want to hookup are as follows:
1. Kemper Profiler Rack (unpowered)- SP/DIF & audio inputs to audio interface
2. Mesa Boogie Studio Preamp - it's audio output is hooked up to a Palmer PGA-05 active stereo cab sim/DI - from Palmer into audio interface.
3. A valve combo amp - which will run the audio thru a Demeter Silent Box and mic'ed into audio interface.

Now thinking of the ES8 I can run one of these into the usual Output socket....actually two of them as the ES8 has dual outputs...

Perhaps it's a typo or misworded, but this is important in terms of signal flow. You can not run anything into an output socket.

So I am going to make some assumptions. The first being that you want to maintain the outputs of the three devices to the existing audio interface.

If so then you can do:-

1. Guitar into ES-8.
2. Various effects in ES-8 loops
3. Do you want to run 4CM with any of the above devices?
3a.    Or do you just want to go into the front end of the devices listed?

If number 3, more information is needed and would potentially be more complex.

If 3a. its quite straightforward.

1. Guitar into ES-8.
2. Various effects in ES-8 loops
3a.
    Boss ES-8 Out 1/L to input of Kemper
    Boss ES-8 Out 2/R to input of Mesa Boogie
   
    You can then select either or both outputs.

    The valve combo amp I think you could accommodate by using the ES-8 volume loop send to the input of the amp.
    If you put the volume loop at the end of the chain the send to volume loop and the amps input will break the signal
    chain to output. So you could have this amp on and nothing going to the final outputs and the other two devices.

  There might be something you could do by putting the volume loop in parallel to allow the signal out to the combo
  amp and also to the outputs of choice.

  Of course additional ABY boxes could be used if needed.

With regard to:-

I think I can adjust the input impedance that the Kemper sees to line level, not sure about that.



If you are going from an output or a loop send into the front end of the Kemper where you would normally plug in a guitar then you are OK, the Boss ES-8 is able to do that in either event.


The first thing that needs working out is the actual signal path, you perhaps don't have the impedance problems you are concerned about.

 

[Cagey]

I agree with Mayfly - this is not a complex issue. You don't need a multi-channel multi-buffered mixing device (like the ES8), you just need the one buffer. The Radial unit he picked out (or one like it) is perfect. The only thing you'll need to keep in mind is whatever amp switching you do needs to happen after the buffer. So, your signal chain would look like: guitar->sfx chain->buffer->amp switch->1 thru n amps. With that setup, the guitar sees a relatively constant impedance, and as amplifier input loading changes due to their being switched in/out of play, the buffer presents a constant load to the sfx chain while compensating the level on the amp side.

 

[Re-Pete]

I agree with Mayfly - this is not a complex issue. You don't need a multi-channel multi-buffered mixing device (like the ES8), you just need the one buffer. The Radial unit he picked out (or one like it) is perfect. The only thing you'll need to keep in mind is whatever amp switching you do needs to happen after the buffer. So, your signal chain would look like: guitar->sfx chain->buffer->amp switch->1 thru n amps. With that setup, the guitar sees a relatively constant impedance, and as amplifier input loading changes due to their being switched in/out of play, the buffer presents a constant load to the sfx chain while compensating the level on the amp side.

After looking at all the suggestions here I realise I was getting too complex. Let's take it back a bit.... I'm using this for home studio.....there's no need to have it all hooked up permanently other than for ease of use & immediacy. It's not like I'm using this rig live & need that sound immediately at my feet.

With that back in my mind I looked for something both Mayfly & Cagey suggested...and found this Palmer Triage.

http://deluxeguitars.com.au/palmer-triage-amp-selector.html

It will hook up all 3 at once if I want that, or one or two.....and it has buffering.

While I don't have the ES8/5 pedal systems to give me pre-programmed sequencing of pedals, this does address the amp assignment. I can re-cable each pedal manually if I have to.... :icon_thumright:

In the meantime, I have been hit with bills (again!) so this will have to take a back seat while I deal with those.

Thank you so much for those who gave their suggestions.