Re: [LAU] [Music] For fun 1 and 2

On Sat, 2 Jul 2016, jonetsu(a)teksavvy.com wrote: the preamp can affect the sound in any number of ways. The most noticable thing I have seen with cheaper preamps has been noise floor. Put the nominal resistance in place of the mic, set the alsa level for the adc to 0 (or maybe plus 18) and use a meter application (meterbridge works) look at the level. The 1010LT has 144DB dynamic range in theory (24 bits), but a good preamp is more likely around 110 (noise at -110dbfs). The LT is likely not that good. These are with the needed gain thrown in to bring the gain up to whatever the ADC is using (probably less than a line level of +4 because the audio PS is only 12v so far as I know) I have two ART pre, the USB Dual Pre.... ok for condenser mics, but the last 5 degrees of gain control sure adds a lot of hiss. They say 48db of clean gain... it doesn't seem to be quite enough for a dynamic mic unless the audio is quite loud to begin with. I also have the USBDualTubePre which claims 65db gain. It is noticably quieter for sure. The mackie CR1604 just works, I have never noticed hiss in that and no colouring, almost sterile. Preamps can also have (or not) a nonlinear transfer character where the positive going half may be amplified differently that the negative or the peaks may be amplified different from the signal close to the zero crossing point (one hopes not actual crossover distortion). Frequency response is another place some preamps are better than others or may sound more pleasing (some times pleasing comes from a non-linear frequency response). Though not likely to affect the AT2050 which has a builtin preamp already, many types of preamp may not have an input impedance well suited to the mic. Dynamic mics are pretty forgiving (SM58s etc), but ribbon mics, raw piezo pickups or crystal mics just sound better if the preamp input is matched correctly. The mackie cr1604 for example, does not sound very good with my piezo pickup either on the mandolin or my acoustic guitar, but both sound quite good going through a Fishman pre. (I have an Fishman amp I sometimes use as a pre as it has line out) I regret to report I do not have a ribon mic at this point (they sound more like an unmiced source even with less than perfect frequency responce of only up to 15k or so) so I haven't tried one of those. I have a delta66 which is sort of in between the delta 1010 and the 1010LT. The deltas have only line level (+4 or -10) with the LT being the one that has the mic pre for two inputs. Considering everything else they have stuffed into the LT I would have to question the quality of preamp. It is not hard to find a mic pre for 3k or more. Hand built ones include the idea of hand picking matched transistor pairs for each stage, transformer inputs or outputs are common too. (some audio transformers may cost as much as the LT...) Mine is probably not that good though it sounds good to me. I get 24 bit adc out mine by taking s/pdif out and into the delta66. My version of mudita24 shows the adc full up position at +18.5 so with the jumper set to the lower gain position, setting mudita to 0db should be right. Check for digital clipping though and modify the setting of the pre and/or mudita to make sure there is never digital clipping. +30db gain overall is not really enough for dynamic mics, preamp required. The sound hole is there, just not under the strings. If the mic is 12 to 18 inches away (if your room is quiet enough :) it should pick up the sound pretty well. I don't know how the "grill" affects the sound, nor how the spreading of the sound hole over so much of the sound board affects things either. You have one so you can listen to it :) -- Len Ovens www.ovenwerks.net