Question About Flat Capture Workflow

[cubdukat]

I recently purchased a Presonus Audiobox 96 USB audio interface to replace the M-Audio Fast Track Pro I was using before they stopped supporting it (and I got sick of it causing Win10 to crash all the time). I attempted to capture straight from the preamp, only to find that it's not set up to record line sources without some kind of attenuation (they require a DI box), so I also ordered custom audio cables that are made to match the required capacitance and impedance for my cartridge, so I am finally ready to take the plunge into preamp-less vinyl ripping.

I have a couple questions first:

1. Should I used the same rule of setting the recording levels no higher than -12dB;
2. What is the general workflow I should be observing? Currently I'm doing click removal, followed by normalization, CNF, placing markers and converting from 24/96 to 24/48 for importing into my MP3 encoding program. Will my workflow for the new method be similar?

[Craig Maier]

Hi,

I usually set the levels to peak out at around -10 dB so -12 dB is probably fine.

My Workflow: Flat Transfer at 96 kHz and 16 bits. Use the Virtual Phono Preamp to apply the correct curve. Now, use the EZ Impulse filter to remove the clicks. Sometimes I use two passes to get a more effective result. Any that are left over, I use the manual interpolate (I-Key) to remove those. Next, convert to 44.1 kHz and then run the CNF per the normal process. Last, apply any enhancements that you desire to the sound. I hope that helps.

Craig

[cubdukat]

It most definitely does. Thank you very much. It's also given me some ideas on how to handle my workflow with my current preamp until the cables arrive.

[Craig Maier]

Is the preamp you are using a flat one? Use of a flat preamp is the best way to go.

Craig

[cubdukat]

No, it’s a U-Turn Pluto.

So far I’ve been using the virtual preamp approach, and I’ve noticed a definite difference. I wouldn’t call the bass on the Pluto flabby, but it’s definitely tighter with the VP method. The high end seems to be better as well, since the Pluto only goes up to 100uf capacitance, and the cables are 200uf. All in all, I’m definitely liking it

[Craig Maier]

It's unclear what you are doing. I am not familiar with a U-Turn Pluto preamp. Is it RIAA? If so, then it is imperative that you check the VPP box under Preamp Hardware Type / check the standard RIAA Preamp box, and then you can apply whatever curve you desire (look under the presets to see the entire list). If the U-Turn Pluto is a flat preamp, then you must check the Flat Preamp checkbox. Using the wrong type of preamp with the wrong VPP hardware checkbox will result in weird results. Please tell us more about the U-Turn Pluto Preamp.

Craig

[Craig Maier]

I just looked up the U-Turn Pluto preamp on the internet and it is an RIAA type, not a flat type. It has 100 pF input capacitance and 47,000 Ohms termination resistance. With this preamp, you must check-box the Virtual Phono Preamp Hardware type as Standard RIAA Preamp. Otherwise, (generally speaking) the bass will be muddy and the highs will be muted.

Craig

[cubdukat]

Yeah, that was the preamp I was using before. The method I'm using is a pair of custom cables that goes directly into the USB audio interface. The cables were made to be used with a Mac program, but they still work. All they do is they match the 47KOhm impedance and the 200pF Capacitance my cartridge (AT VM95e) would ask for from the preamp.

I seem to have gotten most of it down pat, but I had one other workflow question where click removal is concerned.

Is it better to do that before going through the Virtual Preamp or after?

It turns out I may be doing a new component upgrade. Turns out the Presonus Audiobox 96 USB I'm using doesn't like line inputs, so I'm probably going to replace it with a Presonus Studio 24c. When I tried it with the Pluto, the levels had to be set impossibly low in order to prevent clipping, and even with the "flat" cables, all it takes is one tick on the level controls to go from barely enough to clipped. I need something with more flexibility.

[Craig Maier]

I don't understand how you can transfer a record from a magnetic phono cartridge to a line input on a soundcard. You need amplification in-between. Cables will not produce amplification, only attenuation. So, I am totally confused.

Craig

ps - this is the type of thing that you need in-between your turntable and a line input: https://www.diamondcut.com/AppNotes/...structions.pdf

[cubdukat]

The way the Mac program works is that you are using an external audio interface like the ones you'd use to record, say, guitars, and you set your recording levels through that, just the same as you would a regular sound card. The only difference would be that the input would be lower than if you used a flat preamp, but the results would be the same more or less: a signal with no RIAA curve applied to it. I can send you the link to the Mac program's website; they probably explain it way better than I can, but the same principe works with DC10 as well. I've made a couple dozen really good rips from it so far.

[Craig Maier]

I only know that the signal output of one device must be reasonably close in amplitude to the acceptable signal input capability of the next device in a chain. Other than that, I can not be of much help on this. On one end of that extreme, you will get clipping distortion. On the other end of that extreme, you will get less than optimal signal to noise ratios on your transfers.

Craig

[Marc Hildebrant]

Cubdukat,

You really cannot use the cables "impedance" to provide the needed load for the cartridge. A physical 47K resistor is needed, and the flat preamp from Diamond cut does the job.

I would connect the phonograph to the Diamond cut preamp, and then connect the preamp's output to the "

Presonus Audiobox 96 USB audio interface".

Marc

[cubdukat]

This is a diagram of the actual cable. It looks like they put the resistance and capacitance loads in line, and the ground cable is soldered onto the left channel jack.

I am considering the DC preamp to simplify things, but the gain seems quite low for my cartridges (the two AT carts I have take 4mV and the Grado Black takes 5mV). Also, the Presonus doesn't like line inputs, something I found out only after I bought it.

[Marc Hildebrant]

Cubdukat,

Thanks for the info. I had not seen a cable assembly like that before.

My first thought is that , while it may work, you are still sending a very low level signal through a cable that later is amplified. The best way to minimize the noise is to amply the phonographs output as soon as possible and then send it to a mixer, like a Behringer XENYX 502 or similar to vary the gain into the Analog to Digital convertor.

A flat preamplifier followed by a 2-Bus or so mixer works really well to provide a "healthy" signal to the conversion to Digital.

Marc

[Craig Maier]

To Cudukat -

The attenuation (gain reduction) of the shown cable is going to be determined by the terminating resistance (and impedance) provided on the output side of said cable. So, the gain could be almost anything - - - it's a wildcard depending on it loading. No matter - - - it is an attenuater not an amplifier.