Low recording input level

[polywave]

Hi Everybody,
I've been re-arranging my audio setup again. Of course, it doesn't behave like it used to. Now, it seems, when I want to record from my audio devices via my preamp and line in, the recording level in DC6 is down around -50db. When I opt for "what you hear" and play something through WMP, I get the same low recording input level. In both cases, the recording level increases as I increase the gain of the driving device.
So, now that I've told my sob story, are there any sympathetic souls out there that may have an idea as to what I might have done to break my setup, and what I can do to restore the recording function?
TIA,
Harold

[Craig Maier]

Could you describe in more detail the exact equipment that you are using and exactly what is connected to what? Start with the turntable, then the preamp type, what preamp input you are using for the turntable output, etc.

[polywave]

Ok,
So now I've REALLY done it! I installed a Juli@ and now I can't seem to record anything. I can play music through Windows Media Player, but I can't get it to appear in DC6 when I Rec Pause (the recording device in DC6 is Juli@ Ch12).
Also, now my old volume and mute buttons on my keyboard no longer work. I went into Volume>Options>Properties and set the Playback and Recording settings to Juli@ Ch12 also. Granted, I have a Logitech wireless keyboard, so maybe I will not be able to use it for volume and mute with the Juli@?
Help!
Harold

[Craig Maier]

This wreaks of a sound card driver problem or a resource clash. Is this soundcard sold by Tracer? I think so in that the product sounds very familiar to me. I would give them a call and go through the whole thing with them on the phone. Their number is:

1-717-764-9240

[polywave]

Thanks Craig,
This card is one that is recommended by Tracer. I bought it because I want to interface my turntable to my preamp and card using balanced connections. *

[DougMac]

Thanks Craig,
This card is one that is recommended by Tracer. I bought it because I want to interface my turntable to my preamp and card using balanced connections. *

What is your preamp? Is it the one sold by Tracer, the CPT 1000-B? I'm trying to determine if your preamp has balanced outputs. Also, I notice that Tracer no longer lists the Juli@. Did you buy it elsewhere? There seems to be some pieces missing from the puzzle.

Doug

[polywave]

I bought my Juli@ from DJDeals.
As to the preamp, I'm using a B&K PT3. This preamp has worked fine for recording from my tape deck, turn table and cd player in the past. It also has an AM and FM tuner that recorded well. The output level of the preamp is 8V, that was plenty of input signal for the Audigy LS.

My woes with the Juli@ is
1) None of my normal volume and mute functions work from my keyboard
2) I cant record "what I hear".

My plan at this point is to try to understand better how sound works on PCs, and maybe I'm not setting this up right. I would like to continue with the Juli@ because I'm convinced that it sounds quieter than the Audigy LS, and that when I get the balanced connections from my turntable implemented then recording from my audio stack will sound better too.

Is the ANYBODY out there has has sucessfully installed and recorded with a Juli@ that would be willing to share their setup with me? Or am I beating a dead horse here.....

TIA
Harold

[DougMac]

I bought my Juli@ from DJDeals.
As to the preamp, I'm using a B&K PT3. Harold

I looked at the PT3 manual at the B&K site and I didn't see and balanced output connections.

Tell us what you know about balanced vs unbalanced connections.

Doug

[Craig Maier]

A Balanced Input provides no benefit when driven by an Unbalanced Output. If you need a preamp having a balanced output, I designed one for Tracer. We (Diamond Cut) do not carry it, but you can call them to find out about it. I do not remember its model number. They are mono-blocks, so two are required for stereo.

[polywave]

I know that the PT3 doesn't have balanced outputs. But everyone want's to know what setup I have. I have no intention of using the PT3 for the phono preamplifier.

I will either buy the PT1000 (unlikely at this point since I learned about it in the New Way article that I learned about the Juli@), or I will design and build one myself (I already do this kind of stuff for a living, anyway).
I have been researching audio preamps, and a preamp based on the INA103 should provide more than adequate performance for an MM phono preamp with balanced outputs.

But first, I need to get past installing the blasted Juli@! Or return it and try to find a sound card with balanced inputs that works.

This is what I think I know about balanced vs single ended:

Single ended signals are at the mercy of environmental and electronic circuitry noise for two major reasons:
1) Ground loops effectively couple electromagnetic interference (EMI) directly into the wiring, and through the inputs of the amplifiers.
2) Unintended current paths can flow in the wiring of electronic circuits and cause current/voltage noise at amplifier inputs.

Induced noise can easily exceed the noise levels needed for a MM turntable cartridge system with 50-60dB of dynamic range. Assuming 3mV output (full scale into 47Kohms) from the MM cartridge the preamp input noise calculates to 3uV for a 60dB S/N ratio. I think I've managed to reach this noise level in some circuits .

Balanced differential signals are routed via a shielded, twisted pair. Because the twisted signal wires are physically close to each other, magnetically induced noise current is equal on both wires and will cancel (because current is induced in opposite directions).

Ground referenced (common mode) noise is canceled by an instrumentaion amplifier because instrumentation amplifiers by design provide common mode rejection (CMR is down 130dB from 10Hz to 200KHz & 40dB gain for the INA103). Plus, the shield will shunt any stray voltage noise to ground (doesn't do squat for magnetic noise).

So, if I'm out to lunch on this stuff any mentoring will be appreciated.
Harold

[Craig Maier]

The key thing that you did not mention is the preamp input vs the preamp output. Making a preamp with differential (balanced) outputs is one thing. Tracer sells the one that I designed. But, a differential input is another matter. It is no big deal to make a differential input low level preamp, but it is a big deal to modify a turntable tone arm to be compatible with that configuration.

ps - the most important aspect of the balanced configuration is the fact that the ground loop current does not travel through one of the two signal pathways. It travels through the shield alone with none of that current appearing on a signal line - - - thus no
{Inoise} X {Zconducter} normal mode noise Voltage insertion can occur.

[polywave]

Thanks for that feedback.

I'm a little foggy about modifying a turntable tone arm to be compatible with a differential amplifier. Would you please elaborate on that?


Thanks,
Harold

[Craig Maier]

Existing turntables typically use two tiny single conductor coaxial cables to connect the head shell to the turntable chassis and then out to the preamp. That only provides two conductors for each channel, with the shield carrying not only the signal return path, but also the noise signal.

You would need to establish a system wherein the cable shield only carries noise current and no signal current. That implies ripping out the existing tone arm cableing and installing tiny two-conductor shielded cables, one for each channel.

That is a big task since it would also involve modifying the head shell connector up to the phono cartridge. It would also be a bit of a challenge to find tiny enough two-conductor shielded wire which would not effect the mechanical action of the tone arm.

[polywave]

I see what you mean about the tonearm wiring, thanks Craig.

I think I've had enough of this high quality, low noise phono stuff. The Juli@ card prevents me from using the normal volume and mute function on my keyboard, so I'm going to remove it and put the Audigy LS back in ($130 down the drain).

I'll just finish digitizing my LPs using the single ended setup and get on with life.

[Craig Maier]

If you keep the cables short with heavy shields (for low shield impedance, thus low noise level injection), you should be fine with a standard unbalanced setup. Be sure to plug all of the audio equipment and computer into the same power strip; this will help reduce ground loop interference with the low level circuitry. And of course, keep the turntable a few feet away from all electronic equipment, especially monitors and power transformers.

As for your problems with the Julie@ soundcard, I personally would not give up that easily; I would call them and find out what they think that the problem might be. Perhaps the hardware has failed, - - - who knows?