Recording 78 rpm with DC7

[Copper]

Here is what i found, I wrote to the company to tell me what kind of preamp I have inside..

But I found this in english, not to sure what is really mean and how I should set up the VPA... hope is the information you were looking for?

turntable with a built-in line-level preamp and an analog-to-digital converter (ADC) accessible via USB

First, for traditionalists, you can switch out the built-in preamp and connect to a phono input on a stereo receiver or preamp. You will not want to connect to your computer this way, since the cartridge cannot drive a line-level sound card input with sufficient volume, and the signal from the cartridge is heavily pre-emphasized (you would need to use an ?inverse RIAA? software filter to restore the correct frequency balance).

Second, you can switch in the preamp and connect directly to a 1-Volt line-level input (like ?AUX? or ?CD? on a stereo receiver, or the analog input to a computer sound card). If your computer has a superior sound card (as mine does), you might prefer this sort of operation.

Finally, you can just slap the long USB cable into your computer directly, and then use your computer?s sound software to set up a connection to your sound recording program. The TTUSB uses a Burr-Brown ADC chip similar in capability to that used in many other low-priced audio ripping accessories, which means that it provides 44.1k sampling at 16 bits ? good enough for most uses, but a bit limited for critical recording and restoration. Also, I found the signal from the USB to be rather hot, with no apparent way to pad it down. On the other hand, digitizing the sound inside the TTUSB rather than inside the computer is a good idea in many cases, as this avoids the pickup of electrical noise (from CPUs, power supplies, etc.) inside the computer.

[Craig Maier]

I am not sure, but here is my guess:

You do not want to use the USB cable because you have a high performance sound card in your computer.

So, you want switch in the internal preamp and connect the turntables line level output to the line level input of your soundcard.

I am assuming that this output is RIAA since you stated earlier that this turntable has only 33.33 and 45 RPM speeds. So, that would be the most likely configuration for the preamplifier.

After the transfer (in stereo, even though your 78s are in mono) and after the speed change routine has been run, you will want to run the VPA with the "Preamp Hardware" set for "Standard RIAA Preamp" and the Record Type set for either European or American 78s.

Then, de-click the record and convert it to mono using the File Conversion Filter (bottom of the filter menu). Lateral Cuts mostly benefit from a L+R conversion unless one groove wall is much more worn than the other. Vertical cuts like Edison and Pathe' need to be converted using L-R.

Then proceed to the CNF process, etc.

I hope that helps. Keep in mind that I am not familiar with your particular ION turntable.

[wer]

pss - - - Make sure that you reverse your RIAA curve with the VPA only after you have up-converted the speed to real time. Otherwise, the curve correction will be incorrect.

Hi Craig,

I have a bit of a mental problem with that statement.

Assuming the recording on the 78 is a flat level frequency scan from 50 Hz to 6 kHz. Playing it at 45 rpm we would still get us a fairly flat output signal from the cartridge (albeit shifted to lower frequencies), which the pre-amp would then "bend" according to the RIAA specification. If i used the "Reverse RIAA" setting of the VPA NOW, i would be back to my original flat level output signal.
Doing the speed change with this signal would not change the level, but increase the frequencies by the same ratio, ending up with a signal that should be fairly close to the original one played from the 78.

If, however, we take the signal after the pre-amp (with lows emphasized and highs de-emphasized) and change up our speed from 45 to 78, the shape of the curve remains but the frequencies are shifted up by a factor of 1.7. Doing the "Reverse RIAA" now, our turnover and rolloff frequencies no longer agree with the ones of the pre-amp, and therefore the final signal will be anything but level.

Please help me resolve this mental dilemma.

[Craig Maier]

Wer,

I can only state that the only way to get your correct 78 turnover frequency put in the correct place (from a flat transfer) it to change the speed first and then use the VPA to apply the correct turnover. If you are using an RIAA preamp, then you must reverse the RIAA first, but not use the VPA to apply a turnover until after the speed change has occurred. If you are using a flat preamp, always change your speed first and then apply the correct EQ curve.

Craig

[wer]

If you are using an RIAA preamp, then you must reverse the RIAA first, but not use the VPA to apply a turnover until after the speed change has occurred.

I can happily live with that, but imho that is not what was written before:

pss - - - Make sure that you reverse your RIAA curve with the VPA only after you have up-converted the speed to real time. Otherwise, the curve correction will be incorrect.

[Craig Maier]

Sorry - - - I should have said

Be sure that you only impart the correct Turnover curve after you convert the speed to the proper one.

I mis-spoke.

That means a two step process is required if you choose to use an RIAA preamp on 78s and perform transfers with fractional speed techniques. First step after transfer is to reverse the RIAA; next up-speed the transfer; next apply the correct turnover setting using the VPA.

If you use a flat preamp, you can simply transfer the recording at a factional speed, up convert the speed and then apply the proper turnover (Eur or American 78s).

Craig

keywords: fractional speed mastering EQ, fractional speed transfer EQ, EQ for fractional speed transfers

[wer]

Thank you Craig, all clear now.