Strange 5150 issue

[mr.L.]

This weekend I reamped some guitars through a borrowed 5150 and the signal I got from the preamp out is really strange. There is a huge hump at around 120 hz on the palm mutes (way more than can be dealt with using some multiband comping) and the signal is much more dynamic (in a negative way) than I expect from a high gain amp .

I reamped the same parts through a Mesa and checked with some amp sims and these issues weren't present so I'm pretty sure it's not the DI's or the reamping chain.

On the 5150 I'm using the green channel with the bass around 6 and resonance at about 5 (probably doesn't influence the preamp output). Not very extreme settings basswise I would think. Mids are around 2,5 and highs around 6.

Since there are several persons on this forum with great insight in amps, I thought I ask around. Anyone has a clue what the issue might be? Thanks in advance!

 

[Vinny]

I've heard from several people that the preamp out sounds weird.
Try recording form the FX loop

 

[TheWinterSnow]

The FX loop sounds like garbage. The preamp out sounds as dynamic as micing it with a real cab. Its just the way the amp is period, it has dynamics. Don't worry so much about what the recorded signal looks like, dial is what sounds good and call it a day.

 

[HvO]

do you checked the red channel or only the green?

 

[Omega_Void]

Preamp out is a high-impedance output, I believe, so it's not suitable for plugging into the 10k to 47k of a typical line-in.

 

[mr.L.]

Thanks for the replies. I'm gonna check the red channel later today and check whether the fx out returns the same kind of signal. The problems from the preamp out aren't as apparent from the sound coming from the cab. Unfortunately I can't turn it up loud enough to really sound good through the cab, otherwise I wouldn't be bothering recording the preamp out anyway.

Btw I'm running the preamp out back into a DI so the impedance shouldn't be a problem.

 

[Wolfeman]

Btw I'm running the preamp out back into a DI so the impedance shouldn't be a problem.

Say what?

 

[mr.L.]

I was referring to Omega Void's comment about the preamp out being high impedance. Is this incorrect?

Oh yeah I keep the cab correctly connected to the head of course.

 

[Wolfeman]

Usually high impedance is anything above 10k, that's why I'm confused.

 

[mr.L.]

yeah the 5150 manual says the following about the preamp out: "load impedance: 47Kohm or greater" so that would qualify as high impedance or am I not understanding this correctly and might it be better to run it straight into a line input?

 

[mr.L.]

Another question: Would it be safe to connect the speaker output to a DI box and run the parallel out of the DI back into a speakercab or would this fry the poweramp?

 

[Wolfeman]

Another question: Would it be safe to connect the speaker output to a DI box and run the parallel out of the DI back into a speakercab or would this fry the poweramp?

Well your amp would be fine, but could the DI handle the signal?

 

[mr.L.]

I have a BSS AR-133 that has a -40 pad option, so I think that would work. Would it be best to use two speaker cables in this case (amp ->speaker cable-> DI -> speaker cable -> cab) or use a normal jack cable between the amp and the DI and speaker cable between DI and Cab.

 

[AHChris]

Another question: Would it be safe to connect the speaker output to a DI box and run the parallel out of the DI back into a speakercab or would this fry the poweramp?

I know that the Countryman Type 85 DI is capable of handling power amp signals...

EDIT: you can even see it´s capable of that

 

[TheWinterSnow]

yeah the 5150 manual says the following about the preamp out: "load impedance: 47Kohm or greater" so that would qualify as high impedance or am I not understanding this correctly and might it be better to run it straight into a line input?

That would mean that the preamp out is a low impedance output and could be used in a 47K impedance line in. So you should just plug the preamp out into the interface. A DI would work, but really there would be little if any difference.

 

[Omega_Void]

yeah the 5150 manual says the following about the preamp out: "load impedance: 47Kohm or greater" so that would qualify as high impedance or am I not understanding this correctly and might it be better to run it straight into a line input?

Oops, thought it needed more than that. My bad.

Line input spec is 10k minimum for unbalanced. 22k is pretty common, but 47k is not, so check the documentation on your interface. You may still need a DI.

High and low Z are relative things, depending on the expected source.

A guitar fx unit for example might have inputs labeled "hi-Z" at 1Meg for the guitar, and "lo-Z" at 10k for line-level sources.

By contrast, for a dynamic microphone 10k would be high impedance.