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Need gain control...

Postby JRH » 21 May 2012 06:18

that does not have "filters" or other "signal cleaning" qualities.

My issue is high gain. 20db at the preamp, 63 at linn linto.

I purchased a USB HRT LineStreamer which is a very nice and transparent converter. In Audacity w/ many recordings (punk & rock) I'm constantly in the "red". I tried going directly from the Linto to the converter, which is better, but not quite where I want it to be.

What I didn't know is that by going USB it bypasses all software controls, including lowering input volume :(

So, I purchased a NHT PVC (Passive Volume Control) which brought to db down to -6 with peaks about -2, which is where I want to be. Unfortunately, it adds a nasty VEIL to the sound.

Are there other box type passive attenuators that would give me a cleaning sound? Am I even close to going in the right direction?

Your advice would be appreciated
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Re: Need gain control...

Postby Hanuman » 21 May 2012 16:53

JRH wrote:My issue is high gain. 20db at the preamp, 63 at linn linto.

The Linto can be lowered by 10dB, as far as I know, but it doesn't seem like a user-switchable parameter. The preamp gain shouldn't be getting into the picture because line-in to tape-out should have no gain at all.

What I didn't know is that by going USB it bypasses all software controls, including lowering input volume :(

It's not software control that you want but analogue level setting.

So, I purchased a NHT PVC (Passive Volume Control) which brought to db down to -6 with peaks about -2, which is where I want to be. Unfortunately, it adds a nasty VEIL to the sound.

I'm guessing that, due to the lack of buffering, the HF roll-off is occurring in the interconnect cable between the passive control and the ADC. Get a set of inline attenuators from Rothwell and make sure you use them at the ADC input, not the Linto output. Since you've got a volume control now, use it to find the ideal ammout of attenuation and get them to build the attenuators to order.
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Re: Need gain control...

Postby JRH » 22 May 2012 15:00

Lowering the gain is a easy as snipping a wire. Putting it back is a different sorry :)

Yes, I want hardware control, I agree. I also want something that adds nothing or very little to the signal path.

Lack of buffering, HF occurring in the interconnect cable. Please explain more!!

Rothwell inline attenuators, which db value? I've read reviews that state the same thing that I'm gripping about with the NHT PVC. That they have their definite sonic signature. Have you actually heard them?
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Re: Need gain control...

Postby Hanuman » 23 May 2012 17:58

JRH wrote:Lack of buffering, HF occurring in the interconnect cable. Please explain more!!

There are others around here who know much more than I do about amplifiers but, as best I can explain, a buffer stage is present in just about any active preamplifier and its job is to keep the the performance relatively predictable into a wide variety of loading conditions, which in practice usually means cable impedance and capacitance. Without one (like after a passive volume control) your frequency response can be affected more by loading conditions than otherwise, although the extent of this is debatable and debated. It might well have nothing to do with your roll-off but at least it's a possible explanation for your observation.

Rothwell inline attenuators, which db value? I've read reviews that state the same thing that I'm gripping about with the NHT PVC. That they have their definite sonic signature. Have you actually heard them?

I have a couple of sets. I used them on pre-amplifier and power amplifier inputs and was not aware of a sonic signature in either case. 6dB to 10dB ought to do it.

I don't actually think your underlying problem can be properly fixed without recourse to some active amplification of some kind. I had this issue early on. It's pretty poor, I think, that so few ADC manufacturers put analogue input controls on the box or card. Without this basic function you must control the level upstream, with a pre-amplifier or mixer. My solutions to this have been fairly expensive. Initially I ran the phono stage output into a parametric EQ on the way through to a M-Audio 2496 (a PCI card with no level control) then switched to a Digidesign 002 rack and then to a Mytek Stereo96, both with level controls. A lot of different ways of skinning a cat. The other important feature I've got now is that the phono stage I use has switchable output level so a good combination of phono output and ADC input levels can always be found no matter what the record or cartridge is.
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Re: Need gain control...

Postby Rothwellaudio » 07 Jun 2012 15:55

There's an input level control in Audacity - at least, there is in version II which I use. Do you still get overload wuth that set low?
A pair of our in-line attenuators at the input to the soundcard will cure the overload.
However, can't you just turn down the volume on the pre-amp?
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