Need Low Noise Audio Interface for Re-amping

steadystate

steadystate

Fractal Fanatic
As I am going to re-amp with my Axe II (and other amps) using analog connections, I am looking for a quiet audio interface (preferably USB) with at least four ins and four outs (preferably eight ins and outs). Firewire is also OK, as is ADAT optical with word clock.

I have tried a couple of new units from different manufacturers, both of which have exceptional audio band noise specifications, only to find that they are useless for re-amping due to the presence of ultrasonic noise that is intermodulated when sent to a non-linear input such as a distortion generator (an amp). The result is horrendous hiss. The lack of lowpass output filtering seems to be a trend among newer audio interfaces. I don't know why they don't filter this ultrasonic crap out, but they don't.

Has anyone found a multichannel audio interface that is actually quiet enough to re-amp using a high gain amplifier?
 
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I've been using the Focusrite "Scarlett" stuff, personally I only have the 2i2, two channel device, but they have other models with more IO. I've found them quiet and well behaved, no nasties, flat as a flat thing. I'm very happy with mine.
 
AlGrenadine said:
Why not reamp via axefx's usb ?
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For several reasons, one of which being that I often want to record at 44.1. I also can't get the Axe and my other interfaces to operate simultaneously under ASIO in Sonar. Analog solves all of my problems, except noise. Once I get that licked, I'm good to go.
 
RobinMatrix said:
I've been using the Focusrite "Scarlett" stuff, personally I only have the 2i2, two channel device, but they have other models with more IO. I've found them quiet and well behaved, no nasties, flat as a flat thing. I'm very happy with mine.
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Have you re-amped with it? The interfaces I tried (not Focusrite) sounded awesome, until I tried re-amping.
 
steadystate said:
For several reasons, one of which being that I often want to record at 44.1. I also can't get the Axe and my other interfaces to operate simultaneously under ASIO in Sonar. Analog solves all of my problems, except noise. Once I get that licked, I'm good to go.
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Asio4all solves each of these problems too ;)
 
Have you considered trying a re-amping device like a Radial X-Amp. I know it contains a coil for simulating the circuit loading of pickups. Perhaps there is enough high end roll off to prevent the hissing you are hearing. It should be cheaper than a new interface.
 
AlGrenadine said:
Asio4all solves each of these problems too ;)
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This works with one of my DAW programs, but not the other. A quiet analog solution would cover all contingencies.

Kceovaisnt said:
Have you considered trying a re-amping device like a Radial X-Amp. I know it contains a coil for simulating the circuit loading of pickups. Perhaps there is enough high end roll off to prevent the hissing you are hearing. It should be cheaper than a new interface.
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This won't negate the need for a quiet interface. I'd still need to put the raw pickup signal through A/D/A conversion.

Ka_Status said:
I have E-mu 1616m with extremely good converters and instrumental preamps. Good solution for this money.
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Looks like a possibility. I might just contact the manufacturers before purchase to see which ones are filtered and which aren't, if they will answer. I have a feeling that the first-line people won't know what I'm talking about. I hate to buy one, only to have to send it back. That sucks for me, the retailer, and the manufacturer.
 
steadystate said:
This won't negate the need for a quiet interface. I'd still need to put the raw pickup signal through A/D/A conversion.
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Well that is precisely what I was suggesting. That proper signal conditioning circuitry for re-amping would filter out frequency bands useless to the application. Therefore it would negate the need for a more quiet interface. Chasing a converter with a much lower noise floor is setting fire to the house to be rid of termites.

As for your second statement, there should not be any problem with you using the DACs and ADC in your main interface.
 
Kceovaisnt said:
Well that is precisely what I was suggesting. That proper signal conditioning circuitry for re-amping would filter out frequency bands useless to the application. Therefore it would negate the need for a more quiet interface. Chasing a converter with a much lower noise floor is setting fire to the house to be rid of termites.

As for your second statement, there should not be any problem with you using the DACs and ADC in your main interface.
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I see your angle now, but the product description does not specifically address this issue. I need to know what "optimal reach and frequency response" means. There are no specs listed. Thanks for the info. I'll investigate further. I can build my own filters using chokes or even active Sallen Key filters with extremely low-noise op amps, but I'd rather not.

My current interface is quite old and uses a proprietary PCI card, so I'm looking to get a new one anyway. It makes tons of noise in the audible band, so even filtering won't help it for re-amping. The need for a new interface is a given.

I know the A/D converters in the Axe will act as a filter, but since I'm getting a new interface, I want one I can use to re-amp through any amp, including any analog amp.
 
If you've been looking to replace old hardware then that changes the game completely. There should be filtering on all analog I/O to address aliasing and imaging, if that is what you are experiencing so perhaps that will solve itself. Having better SNR and THD characteristics should also help. However, if you are planning to use the AFX front input or consider using analog amps, you should definitely place a reamp device between your line outs and amplifier front end. The frequency response of electromagnetic pickups is limited, operating levels are lower, and circuit load has a great effect on how amplifiers respond, so there is much that could be messing with your signal. It sounds like you are savvy enough that you could even build one yourself.
 
Kceovaisnt said:
There should be filtering on all analog I/O to address aliasing and imaging, if that is what you are experiencing so perhaps that will solve itself.
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I completely agree. Unfortunately, many newer units don't filter out ultrasonic noise generated by extreme oversampling (thinking it won't be a problem). Typically, it isn't, except when running into certain high gain non-linear amplifiers such as a guitar tube amp. The Event Layla24 is an example. Superb noise specs in the audible band (and fantastic sound), but tons of ultrasonic garbage to cause problems when re-amping. I guess they save a buck or two by eliminating the filtering, thinking it won't be needed.
 
steadystate said:
I completely agree. Unfortunately, many newer units don't filter out ultrasonic noise generated by extreme oversampling (thinking it won't be a problem). Typically, it isn't, except when running into certain high gain non-linear amplifiers such as a guitar tube amp. The Event Layla24 is an example. Superb noise specs in the audible band (and fantastic sound), but tons of ultrasonic garbage to cause problems when re-amping. I guess they save a buck or two by eliminating the filtering, thinking it won't be needed.
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? What are you talking about, Steady? AD/DA stages used for audio HAS to use anti aliasing filters. All of them do, no exceptions.
 
Trazan said:
? What are you talking about, Steady? AD/DA stages used for audio HAS to use anti aliasing filters. All of them do, no exceptions.
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I'm apparently having the same problem that some users had with Output 2 of the II. Ultrasonic noise is coming from the output of the interfaces I've tried. It's there. Radio frequency shit. And it causes hiss in some of my high gain tube amps (presumably due to intermodulation). They sure seem to lack filtering to me.

Edit: Confirmed on a scope (Event Layla). Broadband RF noise on the output, starting in the hundreds of kilohertz and extending upward. A homemade choke reduces it substantially,but not enough for re-amping with the wrong amp.
 
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