I have a natural reluctance to use anything with a vacuum tube in it. Vacuum tubes bought me a great deal of food over the years and I think they’re best left in their grave. I talked to a tube preamplifier user a while back and asked him how long he had been using his amplifier. He told me and I asked him about changing the tubes. He gave me The Blank Look. Tubes are very fancy light bulbs and they age, change characteristics, and burn out.
Did your tube amplifier stop working when you dropped it? Did you have to stop and sweep up the glass?
I did take a different tube pre apart once and I was surprised, but not shocked at what I found. They don’t amplify anything with the tube. It’s just there to create That Robust Tube Sound and that’s it. All of the actual heavy lifting is modern solid state components.
But that’s just me. A performer in the shop was using a 1947 Gates tube microphone amplifier for vocal work. He draped the house in black when it failed because I couldn’t get it working again (output transformer failed – inside the windings).
FWIW I’ve not used the Art Tube MP either but I have used other equipment by ART and have been pleased with it. Whilst not sonically the best on the market, the ART equipment that I’ve used has been as good or better than other equipment in the same price range and has been refreshingly well built. I’m not a big fan of tubes either, at least not for microphone pre-amps, though I know plenty of people that swear by them.
So 7 pages of posts later I went to read back the first posts… and (not surprisingly) I found out that now I’m considering the options I ruled out in the beginning because of the budget… The Art USB Dual Pre name just kicked in again and I’m convincing myself (well I guess I already knew this just was trying to fool myself into too optimistic beliefs) that you can’t get good quality at a very low price…
So what began as a choice between which low budget usb mic to get has reached the point of which not-so-low-budget mic preamp interface should I get for my not-so-low-budget non-usb mic…
Koz already convinced me that I should get a PV6, only thing making me having second thoughts about it is this Art USB Dual Pre which has the advantage of being more portable (it’s small, lighter and can run just from usb power and/or 9V batteries, but still having the option for external power supply).
Thinking out loud: maybe I should simply get both and then return the one I don’t want to keep (which could get me in trouble if I don’t want to return any )
I have a process whereby you can use the PV6 and the Macbook as a Digital Audio Workstation enough to sing (or perform) overdubbing and multi-layer recordings with no delay error. I use the Effects Send sound pathways in the PV6 in addition to the straight show channels to do this. I’m going to work this into a web page any minute now.
It’s very difficult to get a preamp and computer to do that. So you might decide to keep both. The tube device for its sound (if you like it) and the PV6 for its mixing ability. The two are perfectly compatible with each other and the PV6 Tape-Out will plug directly into the MBP. They were intentionally designed to do that.
I understand you can get a PV6 with a USB service built in. I have no experience with that.
Good thing about the Art USB Dual Pre is that it should work out-of-the-box without the need for any drivers or software… (just like the t-bone micplug does)
On other news… I’ve successfully reconnected the wires on the t.bone micplug and it’s working again.
Meanwhile I’ll try to find or build a simple 48V power supply for the phantom power and check how the mic will sound directly connected to my soundcard’s line/mic input.
We warn people about those English words. Stereo Line-In (blue) is very different from the mono Mic-In (pink). Very few sound cards have provision to switch between them allowing you to use one connection for both. The best sound cards that provide one connection have little “tick” sounds when they switch because they’re using mechanical relays to do the work. We are talking about managing 0.002 volt analog signals with a noise floor a thousands times lower than that. I need to drop by Tesco later and pick up some more zeros.
Chances are if you have a PC laptop, you have a Mic-In and many of these high-level, stereo production tricks are closed to you. If you have a much larger deskside, you probably have both pink and blue.
I have a dedicated soundcard inside my PC, it has only one input for both line-in and mic-in, although inside it has two separated circuits for each, which are selected (from the software) by an internal relay
Edit: and the plug is a 1/4" (6.3mm) female jack and it isn’t either blue or pink, it’s black and gold
The New Japan Radio NJM5532 and Texas Instruments R4850 op-amps are used for the line-in/microphone input. Asus chose to use miniature relays to do the switching between line-in and microphone modes. My theory is that the relays route the signal through the NJM5532s for the line-in, or the R4850s for the mic mode. The use of relays to switch the routing eliminates the signal loss that you would get if you used solid-state switching.
They also say that:
To the left of the AV100, you can see the Cirrus Logic CS5381 ADC used for the analog inputs. The DJ100 is apparently an AC’97 codec DAC (C-Media CMI9780), and therefore the microphone section of the AC’97 feature set is used as a pre-amp for the microphone (and front panel microphone). AC’97 is not synonymous with the highest quality, but as this soundcard is tailored toward high-end audio playback, it’s not really an issue. You could always get a proper microphone pre-amp if you wanted to do some production-level recording from a microphone. The microphone input cannot be configured as balanced anyway.
Nonetheless I’d still like to give it a try…
Connecting the mic to a preamp and then the preamp to the line-in on the soundcard (selecting the input as line-in and not mic) is another setup that I’d like to try… I’ve tried to connect my Marantz CD Player to the line-in and it seems to be quite noise free… so if I connect a decent mic preamp with line output I’m hoping to get a good signal too…
My quest here would be mostly to find out which ADC would be better… the ADC in a mic preamp + usb output VS. soundcard ADC + a preamp with 1/4" line out
There’s plenty of DIY circuits for that on the Internet. Really good regulation/smoothing is the key. At one time I was considering building a box for 5 pp3 batteries and a cap across the output - 45v should be close enough, but the cost of batteries put me off. For solid state microphones the current draw is really tiny.
If you get round to making one, good quality capacitors are essential as many off-the-shelf electrolytics will produce an unacceptable amount of leakage noise.
Black Gate caps are probably OTT and are hard to get hold of. Elna Cerafine and Nichicon FG are good and more reasonably priced, but again are difficult to get hold of in Europe, but Panasonic FC are good and readily available (CPC, Farnell, RS, …)
LOL - I spotted that yesterday.
Finally got to hear and play with your latest audio sample. This is a pleasure to work with
I’ve had a go at tackling the noise problem.
In this sample I first ran a 6dB/octave high pass filter at 20Hz to remove the DC off-set and a bit of sub-sonic rumble (was that a car going past near the end of the track?) The HP filter seems to work a bit better than the “Normalize” effect for removing DC off-set on this sample as the DC off-set amount drifts a bit (sub-sonic). Then Amplified close to 0dB.
Then I used a subtle amount of noise reduction using Gnome WaveCleaner. The amount of noise reduction was set very low (0.25 on a scale of 0 to 1.0) and the “gamma” setting dropped down to 0.5 (this helps to preserve transients).
Finally I used the noise gate with a fairly slow attack/decay.
Definitely useful doing this as it appears that there is an undocumented change in Nyquist which means that the Noise Gate effect is not compatible with Audacity 1.3.11! (I’ll have to investigate this further).
The result is very close to the sample from Koz (23-sample-with-silences-Keypex). You can hear a slight difference if you listen carefully to the decay on the final note. In the Keypex version you can hear the noise level creeping in as the note decays (before the gate kicks in). Also, in the original track there is a slight “bump” sound just after the note stops (your hand on the guitar?) which has disappeared in the Keypex version. In this version the noise reduction has removed the hiss from the last note and the “bump” is still audible (though on a production job I’d probably remove it). http://audacity.easyspacepro.com/examples/noise_removal/23-sample-with-silences-NR.flac
That will probably work pretty well. A lot of the poor reputation of AC’97 comes from the very poor quality analogue components that are typically used in the analogue end of on-board sound cards. Also the high gain required for microphone pre-amplification is much more demanding than dealing with line-level.
With a reasonable mic pre-amp I’d guess that the difference will be subtle. Getting the 50dB or so of gain to boost the mic level signal up to line level without introducing noise and distortion is the hardest part.
If you want another project to hang around for several years, you may be interested in this snippet that I stumbled upon recently: SSM2019 monolithic pre-amp chip
Most probably… I was recording in the living room (which is where I temporarily have my PC), where the cars passing in the front road can be heard more than I wished for…
The 10m cable I got is a couple of meters short to allow me to take the mic into the free room on the other side of the appartment… (option here is to use the laptop instead). Other place I tried to record the acoustics where terrible and the sound was too boomy…
You can hear a slight difference if you listen carefully to the decay on the final note. In the Keypex version you can hear the noise level creeping in as the note decays (before the gate kicks in). Also, in the original track there is a slight “bump” sound just after the note stops (your hand on the guitar?) which has disappeared in the Keypex version. In this version the noise reduction has removed the hiss from the last note and the “bump” is still audible (though on a production job I’d probably remove it).
The “bump” is probably my fingers going back to the strings after the final chord… You can also hear some breathing during the play
If you want another project to hang around for several years, you may be interested in this snippet that I stumbled upon recently: viewtopic.php?f=27&t=27426
That looks interesting… and it’s available for less than 5 euros at farnell… I may as well add it to the order I’m been thinking about placing at farnell for the last year or so… (still trying to finish that never-finished list of components…)
Although the problem here, as in any “sensitive” electronic gear, is to get/make a good power supply…
I plan on posting an update on the initial post of this thread once I got everything sorted out and settled… So that the newcomers may just quickly read the short version of a very long thread…
<<<Definitely useful doing this as it appears that there is an undocumented change in Nyquist which means that the Noise Gate effect is not compatible with Audacity 1.3.11!>>>
That would go right around me. I’m doing this in 1.3.7.
And yes, that’s why I wanted at least one long slow note decay at the end. If you’re going to have troubles with processing tools, that’s the place damage is going to occur.
If your circuit has no coils at the input, then you get to fool around with not only balancing the 6k8 DC feed resistors very carefully, but balancing the coupling capacitors as well. Remember, they have to be large enough to pass the lowest frequency of interest plus extra to avoid low frequency current noise, and well behaved enough to work with no DC bias on them in the event you never turn the +48 volts on.
The worst curse of phantom power is not what happens when it’s running, although that can be fun. When you turn it off, it dumps a sudden 48 volt charge into the amplifier system. This would be the delicate, noise tuned, super low distortion amplifier system. I can’t find it immediately, but someone made a phantom system that faded the battery supply on and off to avoid that sort of damage.
<<<Also, in the original track there is a slight “bump” sound just after the note stops (your hand on the guitar?) which has disappeared in the Keypex version.>>>
But not all of the versions. The one before this one had a different threshold of noise sensing and the bump came through. I changed the threshold to get rid of it because it came through not as a polished-wood/string/musician activity, but a “pish” of noise.
Delicate events near the noise threshold are very important when messing with this process.
I guessed that, and it helped to identify the problem. Since Nyquist has been updated it is now (correctly) more fussy about whether values are integers or floats. Just adding a dot has fixed that problem. However, I’ve clearly learned a thing or two since I wrote that (almost a year ago) and I’ve identified a couple of other bits that should really be improved. Apart from the coding being rather inelegant, there is virtually no error checking in it and the attack/release times are totally inaccurate. I’ve added some error checking to prevent silly values from breaking it so I just need to sort out the timing issue and tidy it up. Hopefully get that done this week.
@Koz, this would be a good time to say if you want a feature for measuring the noise level, or are you now happy with using the Amplify effect to do that?
As a matter of taste, I’d do that as well. Creative use of noise gating.
Here’s one such circuit, though I’m not convinced that the voltage regulation is really adequate for high quality recording, though that will depend on how forgiving the microphone is:
)
