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Can a quality preamp with transformers lower the noise output on my synth ? Keyboard Workstations
Old 8th September 2011
  #1
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Can a quality preamp with transformers lower the noise output on my synth ?

I think the transformers coupling could act as some noise wall ?
Old 8th September 2011
  #2
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hasbeen's Avatar
While we are on the subject could someone chime in about the use of preamps with HW synths in general? I use a Fantom X6 to get drums to my DAW sometimes until I can get a real drummer. Thanks.
Old 9th September 2011
  #3
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Quote:
Originally Posted by Googlyman View Post
I think the transformers coupling could act as some noise wall ?
A good transformer should pass all the signal pretty well, so noise in the signal won't generally be attenuated. OTOH, isolation transformers may well eliminate ground loop hum, which can be regarded as noise, I suppose.

Cheers,

Otto
Old 9th September 2011
  #4
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AwwDeOhh's Avatar
 

Good gain staging goes along way towards lower noise.
Old 9th September 2011
  #5
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Quote:
Originally Posted by Googlyman View Post
I think the transformers coupling could act as some noise wall ?
i dont

a better preamp may be less noisy than the old one
transformer wont do diddly squat for noise
and could add some
Old 9th September 2011
  #6
Registered User
Hiss or hum?

Using the s/pdif digital output is your best option for a digital noise-free audio transfer.

Excessive hum may be from ground loop hum in your unbalanced cables. Try connecting your AC cables for all your audio gear and the Fantom from the same source. I struggle with ground loop hum, and find that transformer isolation really work. I like the way transformers soften sharp digital sounds too.

Ebtech and Radial have good products (I prefer Radial with Jensen, but Ebtech make products for different applications that Radial don't make).

If its hiss that bothers you - have you optimised your gain structure? I usually set keyboard master volume (analog) to max, for best signal to noise. Adjust digital output level as hot as you can without the sound browning out. (The cheaper converters in keyboards often get crunchy in the top 6dB, well below digital clipping ... make it sound good at the source).

A preamp will add it's own hiss - so choose and set wisely. Do you even need a preamp? You might be able to drive your A/D converters directly with enough level. The creative abuse of a preamp for color is an option, but this generally raises the noise floor, so if you are struggling with noise this may not be a good idea.

I recommend disabling keyboard FX - generally they aren't that great, and are better replaced at mix time. Reverb anyway. That might be adding to the 'noise' in it's own way ... you can get a better, cleaner signal without grainy reverb turn on.
Old 9th September 2011
  #7
Registered User
Turn off phantom power ... sometimes that can add noise for some reason.
Old 9th September 2011
  #8
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BTByrd's Avatar
I may be wrong here, but I don't think preamps will do anything aside from add noise. As amplifiers - increasing the signal that comes into them - won't they just raise the noise floor?

I use my LA610 to add a bit of tube color to synth inputs, and am about to buy a pair of Vintech 500 series pres to use as DIs on my synths. Pres are primarily for adding a bit of color to their inputs (especially useful on digital sources, like my Nord Modular G2 or my Elektron Machinedrum); they're not really helpful for reducing noise. A DI can help if you have a really long cable run though.
Old 9th September 2011
  #9
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If your gain staging is off the preamp might ADD noise. It's about level matching and impedance matching. Level matching is pretty simple to understand.

Check the output impedence on your Fantom. Check the input impedance on your mic amp. A 10:1 ratio is good for load transfer and optimum signal strength ... that is, so you don't lose low end information. But oftentimes, it makes more sense to run your synth into the mic amps. I run my synths into the mic amps because the impedance ratio is more suitable.

If your synth is noisey put a gate on it. If you have line noise get an isolator. ART makes an 8 channel isolator. I have 3 of these and put them between various components.
Old 9th September 2011
  #10
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Quote:
Originally Posted by trashman View Post
I run my synths into the mic amps because the impedence ratio is more suitable.
So, instead of going to a 1/4 instrument input on the pre, you use a DI and go into the mic XLR? Thanks.
Old 9th September 2011
  #11
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Quote:
Originally Posted by hasbeen View Post
So, instead of going to a 1/4 instrument input on the pre, you use a DI and go into the mic XLR? Thanks.
oftentimes you don't want to di because then you have to use the mic circuit for make up gain.

Every piece of gear is different. In general turn the mic amp trim all the way down and just use the level knob if you have one

For example, on my mixer my mic channel input impedance is 3kohm. Recommended impedance input is 50-600ohm. I think my blofeld outputs at 800 or 900 ohm. While not optimal I thought it sounded better going into the mic channel with zero gain then the line inputs.

Level and impedance are not the same.

Impedance FAQ

Here's a good artcile.

Lot's of times if your impedance matches or is good enough but your signal too hot you use "PAD", not a DI to hit the mic amp. Follow me?

The DI matches impedance. So a super high impedance thing like a guitar pick up will never match the impedance on a mic amp, so the DI is necessary. But synths are a totally different animal.

You really have to read the specs on each piece and then do some experimenting.
Old 9th September 2011
  #12
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Quote:
Originally Posted by hasbeen View Post
So, instead of going to a 1/4 instrument input on the pre, you use a DI and go into the mic XLR? Thanks.
yes, I go directly into the mic circuit but turn the trim all the way down. I don't need any! I suppose I could pad the signal (because the impedance matches well enough that I don't need a DI) and then turn the mic amp up. But why? It might simply introduce more noise.

On my interface the mic amp input impedance is 2.2kohm

The direct line input set to accept guitars is actually 700kohm!

The line input is 10k which is typical.

So, as you can see if you have a synth with 500ohm impedance you could use the line input with overkill. But because the impedance mismatch on the mic amps is so underwhelming that the mic amps might you give you a bettter tone depending upon the opamp or transformer. Even without using a DI.
Old 9th September 2011
  #13
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What was key for me was this line right here:
About 600 to 2000 ohms is medium impedance

And also keeping this paragraph in mind:
A few decades ago in the vacuum tube era, it was important to match the output impedance of the source to the input impedance of the load. Usually the source and load impedances were both 600 ohms. If the source impedance equals the load impedance, this is called "matching" impedances. It results in maximum POWER transfer from the source to the load. In contrast, suppose the source is low Z and the load is high Z. If the load impedance is 10 times or more the source impedance, it is called a "bridging" impedance. Bridging results in maximum VOLTAGE transfer from the source to the load.

So, I decided that a mic amp happy to accept 600ohms or 2.2k would be happy with an 600 to 800 ohms synth signal. And I was correct.

In contrast, using a DI in a way simply corrupts your medium to low impedance synth signal to be "reamped" by the mic circuit.

Every piece of kit is designed differently. Grab the manual and read the specs.
Old 9th September 2011
  #14
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BTByrd's Avatar
It depends on the preamp. Some feature a DI that runs through the input transformer so there's no need to use a separate DI for impedance matching purposes.
Old 9th September 2011
  #15
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Unfortunately my Fantom manual says nothing of impedance in the specs. I have always just used the balanced TRS outs to the balanced ins of any pre I have auditioned. I then usually set the gain of my Fantom to max. And use the gain and trim of the pre as I usually do for a mic source.
Old 9th September 2011
  #16
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I have a Kurz with balanced outs and use only balanced cables.

Still the output is a bit noisy.

How can I reduce this ?? cos the sound is superb.
Old 9th September 2011
  #17
Quote:
Originally Posted by Googlyman View Post
I have a Kurz with balanced outs and use only balanced cables.

Still the output is a bit noisy.

How can I reduce this ?? cos the sound is superb.
Depends if the noise is actually on the output of your synth, or if it's coming from the preamp gain.

If preamp gain - get a cleaner preamp (not necessarily a transformer based one. Something like a Grace, GML, or whatever would capture it in it's most "true" form).

If it's just the output of the synth - not much you can do, unless as mentioned said synth has a digital output.

You could experiment with DIing it instead. You could experiment with gain staging (ie turn down output of synth, turn up preamp gain or vice versa) however if the noise varies as well, this won't make a difference (although the less gain the preamps are adding, the less noise they'll add too).
Old 9th September 2011
  #18
Gear Maniac
 

if the noise is from inside the synth... then your only choice is to mod with lower noise parts (for a synth with lots of custom asics like the kurz, probably not a choice at all).

you could try denoiser software after the fact... apparently a couple of those are OK.
I remember the old Cool Edit had a noise reduction feature that worked somewhat decent - you'd record just the noise, analyze it, then record something real, and it would use the noise analysis to take it out.

Sometimes careful EQ can reduce the impact as well, but hard to do without messing up your original sound.

Most 'noise reducers' are targetted as specific kinds of noise - hum, for instance (which can be caused by grounding issues or fluorescent lights), which you can fix, or noise introduced by a preamp/tape stage (traditional dbx NR for instance). But noise in the source? There's nothing that can just magically know what part of the source you think is noise and what isn't; it can only prevent more noise from being added later.
Old 9th September 2011
  #19
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Quote:
Originally Posted by Googlyman View Post
I have a Kurz with balanced outs and use only balanced cables.

Still the output is a bit noisy.

How can I reduce this ?? cos the sound is superb.
On a modern synth you shouldn't really have any annoying noise.

Check your gain staging. You might have some stage cranked. I once had an awful noise on my virus and didn't realize that I had cranked the input volume within the menu pages. I was going nuts until after going thru the menus I saw it was maxed.

Also, cranking the output gain isn't always the best solution. Some synths are designed this way, but many are not. You have to find thy sweet spot that gives u the best s/n ratio.

If you haven't done something foolish like I did, and you have noise that's louder than your output signal, you have a defective part.

If it's simply noisy when the synth goes quiet, you have a lot of self noise: put a gate on it.

You might still be picking up noise from interference, so I still recommend the ART Isolator.
Old 9th September 2011
  #20
My experience is Cant-Squeals have some hiss, some more than others. I used to rebuild them all the time, lower noise analog circuits cut it quite a bit and most should know to shut off all the effects.

Other that that, a noise gate like an Aphex 612/622 works well as does those dbx single ended noise reduction filters. I used to use those followed by an Aphex Type III Anal Exciter to regenerate the lost top end, sans hiss.

Also, if you are using a mic preamp from the balanced synth outputs, that's a no-no. Those are line level outputs, not mic level. Skip the mic preamp and feed it into a line input.
Old 9th September 2011
  #21
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Lmao!

I want the anal exciter for my next model sex party ... Which model is that?


To the OP, I still say read the specs on both devices and use your head. Every piece of gear has it's own specification and design.

I listed the wide variance on mic channel input impedance above: 1 device at 600ohms the other at 2.2k.
Each device fed into the line stage post mic circuit. Mic trim at zero simply passed the signal thru. However, the impedance was perhaps a better match.

Another example, on my apogee mini me one would think the 1/4 plugs were for the line input. Wrong! These were designed for instruments! Another time I was baffled by why it sounded so terrible. The line input was in the xlr and apogee designed it so that all the user did was turn the mic amp all the way down.
Old 14th November 2011
  #22
Gear Head
 

Quote:
Originally Posted by Jim Williams View Post
followed by an Aphex Type III Anal Exciter to regenerate the lost top end, sans hiss.
LMFAO!!! hehhehheh
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