Trouble with high input and clipping

  • Thread starter Thread starter Baltasar Fisk
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Baltasar Fisk

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Hi!

Don't know if I start this thread in the right place but lets give it a shot.

I have purchased a Focusrite Saffire(vertical with white front) and have a large problem with clipping. The problem is located to one of my guitars, an Gibson melody maker SG wich seem to have an output level somewhere around 19k. When I use my telecaster I get around half the input compared to the Gibson. I use both guitars straight into the line-in channel.

So, my question is if there is any way to lower the input-signal without turning the volumeknob down on my guitar =)

Cheers!
 
Baltasar Fisk said:
The problem is located to one of my guitars, an Gibson melody maker SG wich seem to have an output level somewhere around 19k. When I use my telecaster I get around half the input compared to the Gibson.
Click to expand...

Does not compute. An output level around 19k? Level is usually measured in dB. Even if you're referring to frequency that's at the upper limit of human hearing and no guitar I know of can reproduce that.

Make sure you're plugging into a line-in and you have the channel set to "Inst", which stands for instrument. Adjust the gain until you get a MEDIUM level, i.e. keep it in the green. Use the meters in your recording software and look for a peak value of -18 to 6-12dBfs.

Hope that helps.

Cheers :)
 
My bad, maybe I should have left that part. It is not about db but DC Resistance that is approx 19K Ohm.

Anyhow, I have set gain to absolut minimum, put every knob in the internal saffire interface to minimun and I even used the built in compressor and tuned the input there as low as I could.
After all these adjustments it still clips.
 
The input is set to "Inst", right?

What you may be experiencing - and I have never witnessed this before on any interface - is that the output of the guitar is higher than the maximum allowably input level of the interface. I highly doubt that this is the case, though. I didn't even know this was possible. This means that even at the lowest setting, the guitar is still putting out too much level for the interface to handle. This is a common problem with some microphones and low headroom preamps, particularly with LDC's.

19 k ohms sounds really high for guitar pickup resistance. What year was your guitar made? If it's a new 2011 Gibson Melody Maker SG it'll have a 491T humbucker in it, which is the same pickup they put in the SG Standard, albeit without nickle covers. I have one and the output resistance is nowhere near that high.

Maybe something is wrong with your guitar? How does it sound when you plug into an amp?

Cheers :)
 
hi, you might like to check out this thread. There is someone there who apparently had a very similar issue (plus a suggested solution (a pad) as well).

(oops... apparently I can't post a link without making the required 10 posts)

(If you want to search for it, it's at the Music Electronics Forum in a thread titled "DIs sound awful - why?". The initial poster also uses a Focusrite Saffire.)
 
Mo Facta:
Yes, it is set to "Inst" When I switch to "Line" it becomes silent.
And, yes I have the exact same model of the MM SG. I have read though that the pickups in these can be different, don't know why really but for what I know the models have different resistance.
I don't own an amp :(

dai h.:
Thanks, I will dig in to that!
 
Well, like I said, 19K is VERY high for pickup output DC resistance. I shudder to think how many turns of copper wire you'd need on a bobbin to achieve that sort of figure.

I searched and I can't find any pickup with a value that high although I'm sure they exist. I just don't think the 491T falls into that category. The Gibson Dirty Fingers, as far as I can tell, has the highest DC resistance of any Gibson pickup coming in at 16.6 K.

There is either something wrong with your guitar, or your interface.

Have you tried plugging another guitar in?

Cheers :)
 
Yes, I agree with you that it's high. A friend of mine will bring some instruments so that I can check the resistance.
I talked to my local music store and they're pretty sure it's all about the guitar. Might be a combination och things, pup output, pup height etc.

Need the check the resistance first then move on. I'll keep you posted! :D
 
Problem solved!
After lowering the pickup about 7 mm (pretty much to the bottom) the clipping problem went away.
 
Good job! Guess that confirms the problem was too hot a signal clipping the input. There was a similar thread on Gearslutz recently also involving a Focusrite product, so it appears the instrument input design may be less than optimal.
 
Yes, after reading this thread I saw a few other threads on other forums (funny how that happens) reporting similar issues with the newer focusrite interfaces.

From my POV, this is a tell tale sign of manufacturers skimping on components to lower costs. In as few words as I can muster, skimping = lower headroom. In the case of this thread, this is the first time I've heard of a guitar output clipping ANYTHING. It's such a low signal regardless of pickup type it boggles the mind how crap these components have to be.

Cheers :)
 
While lowering the pickups is a work-around, I would still like to know what is happening at the interface.

Which model Sapphire is the interface? Photo?

[h=2]Instrument Inputs[/h]
  • Dynamic Range (A-weighted): 105 dB
  • SNR (A-weighted): 105 dB
  • Frequency Response 20Hz-20KHz +/- 0.1 dB
  • THD+N, -1dBFS, min gain, no pad < 0.0025%
  • Maximum Input Level for 0 dBFS (minimum gain, no pad): -3 dBu
  • Maximum Input Level for 0 dBFS (maximum gain, no pad): -53 dBu
  • Maximum Input Level for 0 dBFS (minimum gain, with pad): +7 dBu
  • Maximum Input Level for 0 dBFS (maximum gain, with pad): -43 dBu
  • Pad Attenuation: 10 dB
  • Crosstalk: > 80 dB
Click to expand...

This is the specification for the current Sapphire 6 USB, from the Focusrite web site.

From this, we see that the maximum input level for DI with pad engaged is +7dBu with gain at minimum. That's about 1.75V RMS (4.9V P-P) by my calculation.

I'd have thought this was a reasonable degree of headroom for an instrument input?

Maximum Line input for the Sapphire above is about +16dBu, so another solution would be to use a separate DI and connect to the line input.
 
It sounds like a classic case of an instrument input with insufficient impedance for some instruments. I would try a quality active DI into the mic (or maybe line) input.
 
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