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Topic: Pro-Ject Debut III USB Preamp Advice (Read 16788 times) previous topic - next topic
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Pro-Ject Debut III USB Preamp Advice

I have the turntable mentioned in the title. I suppose it's no big news that the USB-out is sometimes too loud (no gain adjustment) with some vinyl (which results in clipping,) especially nearly every double-LP I own. Much to my dismay it also happens with a few regular ones like my mint original-pressing Black Sabbath "Mob Rules." For about 70% of my LPs it's fine, though "limited" to 16-bit resolution for recording.

My questions are these:

Would it be feasible to use something like the M-Audio Firewire Solo Amazon to record my needledrops from the preamp's RCA-outs to my Macintosh? (I'm using VinylStudio and it's pretty great IME.) If so, would I be able to effectively do so at 24-bit? (I don't imagine I hear any difference, but would like to do so for editing purposes.)

Any recommendations/good advice is greatly appreciated. (I wish I had researched this TT before I bought it. I'm considering trading it in later and getting a regular Debut III or something else in their line-up for under 800 USD...that's just not going to happen anytime really soon. I'm otherwise pleased with this TT's performance, so I wouldn't mind coming up with a good workaround. I get great results with many records and the hardware/software combingation.)

Pretty new to digitizing vinyl, so please forgive my ignorance.
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #1
Absolutely, so long as you run the TT line level outputs into the "Phono" jack on the back of your preamp.  You can take a signal for an external ADC from the main pre-amp out or the tape out.  I do the former since there was for some reason a hum on the tape outs.  For an ADC, I use the 24/96 Tascam 122 mk2.  Total investment would be around $100 plus some cables if you don't already have them.  (Note that for this ADC you need cables with 1/4" TRS plugs.  Amazon has them; search "hosa cpr cable".)

Note: Actually the Tascam 144 mk 2 is cheaper on Amazon at the moment.  Good deal!

Pro-Ject Debut III USB Preamp Advice

Reply #2
@Apesbrain: The OP's turntable has a preamp built in, so the output from the RCAs is already line-level.

@OP: As such, any halfway decent audio interface with "real" line-level inputs - and I'd say the M-Audio Solo definitely qualifies - should give you very good results.  I know I've been very happy with what I've been able to achieve with the output of my Audio Technica AT-PEQ3 preamp into the line in on my little M-Audio Transit USB.
"Not sure what the question is, but the answer is probably no."

Pro-Ject Debut III USB Preamp Advice

Reply #3
Thanks for the replies. Apesbrain: yeah, this particular Pro-Ject TT has a built-in preamp. I appreciate your recommendation for the Tascam. I checked it out and it seems like a really good value. It may actually prove to be less of a pain than dealing with a FireWire interface.

Mixminus1: I always appreciate your help and contributions on this site. I guess I was just worried that it wouldn't be "as good" as the results I'd get from having a TT with a separate preamp. I don't see how the one on this table could be any "worse" than any other solution that doesn't involve tubes or whatever. (Those I don't care about. If I felt the need for a tube-sound it would be in the playback equipment not in the recording itself.)

I just have a few "loud" records that sound too nice (to me--subjective, I know) to not have digitized for the sake of convenience and preservation of the source.
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #4
Clipping via the USB connection is caused by the analogue signal being too hot. The analogue circuitry produces too high a signal level and overloads the ADC input, ahead of the USB interface. The signal will be just as high if fed to any other ADC input, such as those in a Tascam or M-Audio interface unless there is some built-in extra line-level amplification between the phono preamp and the ADC that isn't in the circuit going to the TT's RCA outputs. This is not very likely.

The analogue input to the ADC depends upon the phono cartridge output and the phone preamp amplification. In most purely analogue system clipping is not likely because the phono preamp output is fed to an analogue input with a volume control -- an input level adjuster.

Very few line level input of an ADC have any kind of input level control. The expectation is that the level will be adjusted before it reaches there.

Line level is not closely defined. What is too high a signal level for one ADC, causing clipping, might be easily handled by another, thus no clipping.

There are thus four places changes can be made:
a different phono cartridge
a different phono preamp
a different ADC
a level adjustment, i.e. a line level preamp or a mixer, between the phono preamp and the ADC.

Pro-Ject Debut III USB Preamp Advice

Reply #5
...a level adjustment, i.e. a line level preamp or a mixer, between the phono preamp and the ADC.


So basically (if I'm understanding correctly) the signal is being clipped before it ever reaches the RCA-outs on my TT? If this is so, then I guess the best solution is to wait until I can sell this and get a regular Debut III (sans the preamp) and a proper preamp that can be adjusted. That's a real bummer.

I don't feel like experimenting with cartridges or ripping apart the preamp. Neither sounds like a very easy solution or task I'd want to undertake. The latter would ruin any resale value for sure!

Now I really wish I had done my homework before I bought it.

EDIT: grammar.
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #6
No, Andy's saying that the outputs of the internal preamp are clipping the inputs of the internal A/D converter inside the turntable.  The RCA outs are the same analog outputs from the preamp - pre-A/D converter - and Andy's concern is that they may be so hot that they would still overdrive the inputs of an external A/D converter.

I'm not convinced this would be the case...it would have to be a VERY hot phono pre (which it still may be!).  Since all we have to go on here is anecdotal evidence and experimentation, i.e. I'm assuming you don' t have a test record and oscilloscope just lying around , what kind of Mac do you have?  You've probably answered this before on the forum (and I may well have asked the question  ), but if it's a desktop model - iMac, mini, or Pro - you could try plugging the Pro-Ject's preamp outputs into the line in and seeing what kind of levels you get.

While my mini's input is a bit on the sensitive side, it's still a "reasonably" line-level input.  Even if you have to pull the input level all the way down in the Sound control panel, if you're still getting clean sound and no clipping, I'd say you'd be good to go with any decent USB/FireWire audio interface - hell, you might just try capturing with your Mac's input!

If, however, you still get noticeable clipping, then there's a chance that an external interface might still be overdriven, as well.
"Not sure what the question is, but the answer is probably no."

Pro-Ject Debut III USB Preamp Advice

Reply #7
"it would have to be a VERY hot phono pre"

That is not the case. I've recorded about 750 albums (times some factor of LPs for all the double and triple LP albums and boxed sets, up to 10 LPs each). Except for a few large pops and clicks, nothing has ever clipped. Some albums have had maximum peaks only 0.1 or 0.2 dB below maximum, so I know the possibility exist that I will someday meet that hotter LP, but my cartridge, phono preamp, and soundcard inputs specs work together quite well. The ADC inside the TT is probably nothing special in terms of it's input specs.

However, over the past 8 years that I have been workin gwith LPs I have read a number of posts, on this and other audio forums, about people having virtually every LP they try clip --  using the same soundcard. That means either their phono cartridge put out a significantly higher signal than mine (not uncommon) and/or their phono preamp had more gain than mine.

Just to be clear, I made no recommendation for modifying anything inside the TT, only possibly exchanging the cartridge.

Using the level control of a built in soundcard to lower the recording level will not protect against clipping. Except for a microphone input gain, there are very few such controls that are not acting in the digital domain. That is, the audio is already digitized before it reached the soundcard control panel. If the analogue input level is too high, the signal is already clipped by the time the soundcard's level control gets it.

The level received by a recording program could be down 1dB or 50dB, but the audio will still be clipped. The soundcard control cannot effect that. The adjustment must be made in the analogue domain, between the phono preamp and the soundcard input. This is normally done by adding another piece of analogue equipment, not by modifying anything in the TT.

Pro-Ject Debut III USB Preamp Advice

Reply #8
mixminus1: my Mac is a late 2010 13" MacBook Pro (I also have an Alienware m15x, but I wouldn't use it for such tasks as it's latency is ridiculous and has irreparable sound card issues...you know: Dell "high-end" engineering  .) I guess the headphone jack doubles as the line-in on this particular MacBook.

AndyH-ha: you're basically saying that if I had something like the aforementioned M-Audio FireWire interface -and- a line level preamp or a mixer then I'd get respectable results? Do you know of a good one that I could purchase?
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #9
I can be of only limited help here but you should know about a few possible pitfalls.

Macs have used firewire for a long time, so information should be available: For many years firewire has had problems with audio - unless - the proper firewire controller chipset is used. This is the computer's chipset, not what is in the audio interface. I never used firewire so I don't recall just what the difficulty is.

Texas Instrument used to be the only recommended chipset for audio but I think there is another now. Anyway, if the computer uses an audio friendly chipset, no problem. If it does not, going the firewire route is likely to bring more disappointment.

USB generally works well. USB 1 is adequate for LP recording but lacks the bandwidth for some functions. You mentioned being limited to 16 bits, which could be the ADC but is more likely the USB interface. USB 2 does not have this limitation.

Some bus powered USB audio interfaces are rather noisy. This doesn't appear to be a USB limitation, just a device design limitation. Be sure either that you have good information on the interface's noise floor or you get one with its own power supply.

Notebook power supply design is notoriously bad for audio, producing a high noise floor. This is not poor construction or cheap parts, it is basic design. Generally there is a  major difference between running on battery and running off the mains supply, so unplugging the notebook during recording might be all you need if the problem exists in your computer. There are some solutions for when running from mains power but, reportedly, no one thing works with every notebook and nothing works for some.

This noise might not be noticed with some music, stuff that has a generally high level and relatively little dynamic range. If you have recorded LPs with quiet passages, such as some classical recordings where there can be stretches that are down 50 to 60 dB, you should know if you have anything to be concerned about.

While there is nothing inherently expensive about producing a line level preamp, there seems to be a cultural taboo against offering stand-alone units for less than high-end audio prices. Small mixers can be had at a much more reasonable cost. That being said, I don't know which to suggest, never having used one myself. If there are no readily forthcoming recommendations from this forum, try
http://www.audiomastersforum.net/
where a fair number of experienced recording people hang out.

Another route is building something yourself, if you have experience or want to get into soldering irons. A basic, but good, line level preamp doesn't have to be complicated, and a stand-alone passive attenuator can be fairly simple.

 

Pro-Ject Debut III USB Preamp Advice

Reply #10
The possibility also exist that you might not have recording level issues going from the TT's analogue line level output straight to a soundcard's line level input. As I wrote earlier, line level specs are not exactly a rigid standard. You could certainly try that with  one of your know problem LPs and find out what happens before you go to the trouble and expense of another piece of equipment.

Pro-Ject Debut III USB Preamp Advice

Reply #11
@OP, I now understand and I'm sorry for the misinformation in my earlier response.  When you spoke of taking the TT output from the "preamp" I took that to mean you had a separate stereo preamp in your chain which you could use to reduce the gain.  I see now that by preamp you meant directly out of the line level outputs on the back of the TT.  So, as others have already said, you still may need some way of reducing the TT line out level.  The Tascam models both have L/R gain controls that may be sufficient.

If you have a stereo RCA to 1/8" cable lying around, then try the "cheap and cheerful" test that mixminus1 (and AndyH-ha) suggested above.  Run the TT preamp outs directly into the audio line in on your Mac.  Open up your recording software, set it to record from your internal ADC, and see if one of the problem LPs is still too hot.  Presumably, your software has gain controls that can be used to adjust recording levels.  As mixminus1 said, for those few problem LPs you may be fine just using the Mac's internal ADC for your needledrop.  For that matter, you may prefer the results you get using the internal ADC.

It's a little confusing, but I think this page is indicating that your Mac ADC can create samples up to 24/96 or 24/192?

Pro-Ject Debut III USB Preamp Advice

Reply #12
Well, I do have a RCA-to1/8" cable that I use to occasionally line-in my iPod to my home stereo system. I tried it out as you guys suggested and there was no issues with clipping. I recorded a 2xLP (Trivium's "In Waves") that gave me problems through the USB and it worked well in VinylStudio. I adjusted the volume to max out at around 92% @ 24/192 (overkill, but just for the hell of it.)

I'm concluding from this that there's no problem recording from the on-board preamp to something like the M-Audio... Speaking of that: I feel what you're saying about the possible FireWire issues, AndyH-ha. I'll probably just go with the Tascam that Apesbrain recommended. USB 2.0 is more than sufficient for my purposes. I think you're right about the USB 1.1 protocol used by the Debut III's preamp. I'm pretty certain that's why the needledrops are limited to 16 bit resolution.

I haven't had an opportunity to listen to the results of the Trivium LP rip yet. This may be feasible but I'm still thinking I want the Tascam US-144MKII...it seems like a good bargain and may be a "better" way of getting the job done.

I've always been kind-of aware of possible issues with a laptop and its mains power supply. I have been  just running it on battery when doing needledrops. It's never a problem--the battery seems to last forever on my 13" MBP.

All of your input has been helpful and is not unappreciated. Thanks. 
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #13
"I adjusted the volume to max out at around 92%"

"Presumably, your software has gain controls that can be used to adjust recording levels"

That you turned down the level via the on-board sound card's control panel volume control, making the recording level less than 0dB, does not mean that the audio wasn't clipping. In most cases that adjustment is in the digital domain, after the ADC, so it can't effect the input signal level, no matter where you set it. If it is indeed adjusting in the digital domain, all you are doing is losing resolution by setting it at less than maximum. No recording software can do anything about it either.

I don't know what your audio software is like, but if it allows you to zoom in to see the individual samples, you can look at the highest peaks to see if they are actual audio peaks or flat, clipped off peaks.

Pro-Ject Debut III USB Preamp Advice

Reply #14
Nah, I had it turned all the way up on the Mac's on-board sound settings. The 92% peak was in VinylStudio's line-in level adjustments.

I uploaded a sample if you want to have a look... Sample "In Waves"
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #15
It seems rather strange that a recording application has such a function. What use can it be? Reducing the recording level in the digital domain (the software) just drops bits captured by the ADC? Do you believe that buys you something?

Pro-Ject Debut III USB Preamp Advice

Reply #16
What cartridge is it on the turntable? Just asking because I hear quite a lot of distortion which I guess is because the track is far into the middle of the record, 33 1/3 rpm and therefore suffers from inner groove distortion. Regards.

Pro-Ject Debut III USB Preamp Advice

Reply #17
punkrockdude: it's the stock Ortofon OM5e that came pre-fitted from Pro-Ject. I never hear (or know how to identify) said distortion.

AndyH-ha: I'm still pretty new to all of this so I guess I didn't really believe anything or give it much thought until you mentioned it. I'm gathering from everything you've said that I should have the Tascam (or similar) adjusting volume between the preamp and the computer--and that the volumes on the MBP's internal soundcard as well as VinylStudio (or Audacity) should all be maxed.

...I guess I'm still not understanding if that particular piece of equipment would be appropriate to adjust the sound in the analog domain before it gets into the computer's USB port.
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #18
Quote
I'm gathering from everything you've said that I should have the Tascam (or similar) adjusting volume between the preamp and the computer
No. Between the phono preamp and the Tascam (or any other soundcard/audio interface). If adjusting the level is necessary, an additional piece of equipment is required. This additional piece is a line level preamp or a mixer (which always has a line level preamp built in) or a passive attenuator.

If there is no clipping from your highest analogue input level, you do not need one of these. Their use is very common, but not universal. I have never needed one for vinyl but I have a home made preamp that I may use when recording from cassette (there mostly because I want to amplify the signal rather than attenuate it.)

There are a few "interfaces" that have a mixer built in to the same box as the ADC and the to-computer connection (said connection being USB, firewire, or a PCI card) but they are the exception. I've never played with one so I don't recall who makes them or whether you could save money relative to buying separate pieces.

Pro-Ject Debut III USB Preamp Advice

Reply #19
Alright. Thanks for your reply and your patience, Andy. (I know you've been basically trying to tell me the same thing more than once...sorry.) I guess I'm going to have to locate a line level preamp/mixer and the Tascam/sound card. (Maybe I should just trade in the table and do it "right.")

If anyone has any good suggestions for the pre/mixer or other related ideas please feel free to let me know here or PM. Thanks.
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #20
Have you determined that you get clipping using your on-board soundcard?

If you do indeed want another soundcard, and you are not in too great a hurry, you should first try recording into the new soundcard directly from the phono preamp and find out if clipping is a difficulty you need to overcome -- unless you just like the idea of having more gear, really needed or not.

Pro-Ject Debut III USB Preamp Advice

Reply #21
Yes, this and a few other records seem to clip in VinylStudio when the slider is maxed (and the on board soundcard's is maxed as well.)

I'm researching some Tascam solutions at the moment (and trying to make a lasagna!  ) to definitively ascertain if the volume adjustments are done in the analog domain (prior to AD conversion.) I got some info from a member that seems to indicate that this is indeed the case.

None of this is terribly urgent to me, but I need to research what I need so I can hopefully get on with it within about a month or two.
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #22
I have the turntable mentioned in the title. I suppose it's no big news that the USB-out is sometimes too loud (no gain adjustment) with some vinyl (which results in clipping,) especially nearly every double-LP I own. Much to my dismay it also happens with a few regular ones like my mint original-pressing Black Sabbath "Mob Rules." For about 70% of my LPs it's fine, though "limited" to 16-bit resolution for recording.

My questions are these:

Would it be feasible to use something like the M-Audio Firewire Solo Amazon to record my needledrops from the preamp's RCA-outs to my Macintosh? (I'm using VinylStudio and it's pretty great IME.)


What you describe is of course feasible, but the more relevant question seems to be whether or not it will do you any good.

To summarize what's been said:

(1) How are you observing the clipping? The only reliable way to observe clipping is to base your observations on waveform distortion of known audio signals.

For example, the material on the source may be clipped, and there's  nothing you can do about it.  I use the loudest tracks on test records for setting levels. They are usually recorded with sine waves, which makes clipping obvious. They are generally the loudest tracks that can be reliably cut without distortion. BTW, they double check these tracks with a microscope so whether or not they are reasonably clean is known by other means than simply playing them back. LP cutting lathes can cut tracks that can't be possibly tracked by *anything*.

(2) Please be aware that once you identify true and genuine clipping you still don't know where it is coming from without more evidence. Cartridges can clip (mistracking), preamps can clip (too much gain or not enough rail voltage), audio interfaces can clip for the same reasons, and you can introduce clipping with software, either inadvertently or intentionally.

(3) The point of maximum flexibility is obtained by having both a preamp and an audio interface that both have effective gain controls.

For example, I have problems with too-loud video tapes causing clipping in my VHS ripping setup. The solution was to put in-line passive RCA  attenuators in line with the inputs of my audio interface. Same thing can happen with vinyl or analog audio tape.


Quote
If so, would I be able to effectively do so at 24-bit? (I don't imagine I hear any difference, but would like to do so for editing purposes.)


There's no technical justification for using > 16 bits for digitizing vinyl or anything that is not already digtial, given that vinyl is inherently limited to about 12 bits worth of resolution and it is actually one of the best of the analog audio formats. Only high speed, wide track analog tape is better. 

If your software has 3 bits or more extra resolution as compared to your source material, the losses in the digital domain are so far into vanishing that it is rediculous. Even one extra bit gives you a very useful dollop of additional headroom.

Pro-Ject Debut III USB Preamp Advice

Reply #23
How are you observing the clipping? The only reliable way to observe clipping is to base your observations on waveform distortion of known audio signals.
...
The point of maximum flexibility is obtained by having both a preamp and an audio interface that both have effective gain controls.
...
There's no technical justification for using > 16 bits for digitizing vinyl...If your software has 3 bits or more extra resolution as compared to your source material, the losses in the digital domain are so far into vanishing that it is rediculous. Even one extra bit gives you a very useful dollop of additional headroom.


Thanks for your thoughtful reply and insight.

I'm not observing the clipping in a very meaningful way, I guess. I'll be quite honest with you and admit that I've little idea what I"m looking at/for or how to read a waveform. (I really only have Audacity (and VinylStudio) to work with. Very new to all of this. ...but I'm just seeing the indicator/slider go red and max out at "CLIP" in VinylStudio while recording these records. (Of course the slider itself is disabled over the USB connection from the preamp.)

My preamp really has no effective gain control. I was talking to a friend who has one of those cheap Ion USB tables and he claims his does have a gain knob. (That  got me a little irritated!)

I've actually been pretty happy with the results of the rest of the records. Some only maxed out at 50 to 64% volume, but even those still sounded good. AndyH-ha would say that's wasting bits but there's really nothing I can do and I assume it's far better than having clipping.

Audacity has a clipping indicator. I'm wondering how useful or accurately indicative that would be? (FWIW Audacity seems to only indicate clipping on records in which VinylStudio indicated it as well. I've never seen Audacity's indicator identify clipping on stuff that VS didn't also give me its indication...however effective or accurate they may or may not be.)

I get what you're saying about 16 bits. Even VinylStudio's help says that this is sufficient for most users and only suggests a bump up to 20 if one is really concerned about some extra headrooom.

I suppose I need one of those test records. In your opinion, do you think it's a big deal if the record is recorded at only about 60% of its potential non-clipped volume?
The Loudness War is over. Now it's a hopeless occupation.

Pro-Ject Debut III USB Preamp Advice

Reply #24
Quote
Audacity has a clipping indicator. I'm wondering how useful or accurately indicative that would be?


Audacity can only indicate samples that hit 1. That is all it does. It does not point out clipping, but it very tenuously suggests remotely possible places where maybe clipping might occur. If you zoom in, you'll see the red blocks break apart into lines i.e. the single samples that bump their heads on the roof.

The takeaway is that if you reduce that waveform's gain by an infinitesimal amount, the red lines vanish, but you'll in fact have done absolutely nothing about the waveform's nature, clipping or not.