Zilla wrote: If the caps are rated at 25v or less, then the +/-24v supply will stress them and cause them to eventually fail. Either carefully inspect the device to be powered, or stick with a +/- 18V supply.

This is a good point, but maybe there is more to consider. I am now wondering what the TRP's internal rail voltages are...

rfreez wrote: Let me admit that the question was a bit hypothetical. On a recent trip to a village 3 hours away from my city i came across an old church...

Interesting. How did you get to that village? Is driving a possibility? I wouldn't want to be schlepping such a huge battery power supply onto buses or asking porters to carry it!

which other mic are you using that requires >50dB of gain?

avenson sto2 microphones... these are ultra sdc omni microphones with a 28dB noise figure. When micing a plucked guitar from a foot or more, it easily requires more than 50 dB of CLEAN gain. I have heard samples of a guitar mic'd similarly through a gordon audio mic pre and it was WAY cleaner... (also i frequently use an re20 which sucks some serious gain as well).

As a matter of fact, i don't own the apogee or the TRP or any ribbon mic. I have a lowly MOTU 2408 mk3, the quadmic preamp, half a dozen random microphones... For the work we are currently doing (mostly radio commercials and suchlike) it is more than adequate... However, a project we have signed up for recently should facilitate an upgrade in gear and i'm looking at making it a setup i can easily move around for remote recordings.

Interesting. How did you get to that village? Is driving a possibility?

The village is in the border of tamil nadu and andhra pradesh.... there is a decent road off the highway which ends 3 Km from the church after which its a "kuccha" road... We made it all the way in a small car (tho' the aforementioned 3Km was not comfortable...) It was apparently set up by some cult based Church in the 60s and since after they left (or were forced to leave), a couple of rooms are being used by the forest department (where i happen to have some connections). Also the current occupants have a "make do" electricity provision for their minimal purposes, but apparently voltages fluctuate severely and there are frequent power cuts as well...

Another thing is that in this particular place, i spent about 20 mins and just sang in a few places (i am NOT a singer) and it sounded great... I really have no clue how instruments and small musical ensembles will sound in there and have no experience to gauge the same... all i know is that its big, quiet and has a lot of reverb which "sounded" pleasing to my ear at the time... (so my question is more about "what does it take to power a small mobile rig" than anything to do with this particular venue).

thanks and respect,

rfreez wrote: avenson sto2 microphones... these are ultra sdc omni microphones with a 28dB noise figure.

Do they require phantom power?

rfreez wrote: The village is in the border of tamil nadu and andhra pradesh....

Sounds good to me...

rfreez wrote: As a matter of fact, i don't own the apogee or the TRP or any ribbon mic.... (so my question is more about "what does it take to power a small mobile rig" than anything to do with this particular venue).

Me thinks this information changes things for the better. Now we are not restricted to making square pegs fit in round holes. With the previous constraints removed we may engineer (if only as a mental exercise) a system which solves your particular problems more ideally. So let us list some the conditions we are dealing with...

1. Recording of acoustical instruments with modest SPL's.
2. Locations are fairly remote, limited access.
3. Unreliable or absense of electrical power.
4. Hard-disc multi-track recording required.

Please add anything which may have been overlooked. We also need to list some goals. That is to say, which qualities would you like to achieve in this recording. Since no system can satisfy every desire, it is helpfull to list those qualities which are most important to you...possibilities like...

1. Low noise?
2. Sense of space?
3. Realistic tone/timbre?
4. Multi-channel release?
5. ???

I have my own ideas, but maybe someone else would like to take a crack and offer solutions which over-comes conditions and achieves goals?

Zilla wrote: With the previous constraints removed we may engineer (if only as a mental exercise) a system which solves your particular problems more ideally.

This sounds like fun, even if it only turns out to be a theoretical exercise. Keep the information flowing...

With the previous constraints removed we may engineer (if only as a mental exercise) a system which solves your particular problems more ideally.

Thanks very much, zilla.

Regarding what I want to do with the gear...

Record up to 8 channels at up to 24/96 resolution in:

*1 Remote locations without stable or guaranteed power such as old churches, historical monuments etc.

*2 Studios... so that i can be independent of the house gear. Here in chennai, we have a few old studios that have good rooms, but NONE that are updated with optimal gear for acoustic music recordings... hardly any matched pair of microphones, NO ribbon mics, mostly only yamaha o2r and tascam low end mixing consoles, very poor headphone monitoring and distribution systems... This city has a famous and unique (film session) string section often used by international producers, but there is not a single engineer here who is conscious of the basic tenets of acoustic music recording.

*3 Live concerts in less than perfect venues, where i mostly close mic with dynamics.... I have done TOO MUCH of this type of work in the past, and was for some time strongly against recording under such suboptimal circumstances, but of late, i have begun to feel that the music is more important than everything else, so if the situation warrants it for whatever reasons, i must be prepared for the same...

*4 Solo overdubs in hotel rooms... My "day job" at this time is working as composer/musician/engineer with my partner, and in our new work with films, we expect to be traveling to mumbai and hyderabad, to record vocalists and on occasion, instrumentalists... and i do believe that for this type of close mic'd solo overdub situation, a hotel room is frequently the most sensible option.

For all situations except *1, power should not be a problem...

I intend that some of these jobs will make me money and some will be for my (soon to be) ghetto style acoustic indian music recording label which i plan to run without a financial profit motive...

I want a completely mobile system, which i can downscale to the size that me and my partner together can easily carry on flights for the said hotel room recordings (along with a midi keyboard and personal effects).

I seem to prefer dynamics for many of the situations (i love the re20 and sm7b for vox), and over the last few days (since my last post here) i have been experimenting (for the first time) with a pair of ribbons (cascade fat heads), and i suspect that ribbons are going to a play a significant part in my microphone collection.

To sum up:

I need a recording system with:

* 8 channels @ 24/96
* 4 pres for condensers, 4 for ribbons/dynamics, low noise overall is important
* power conditioning
* headphone distribution for 12 people

The Apogee Ensemble, 2 x AEA TRP, basic power conditioner and headphone amp will fit into a 4 space rack... the rest of the stuff will fit into a couple of boxes... For most situations this should be portable enough...

So, if there is a better way to do this, please bring it on!

Respect and gratitude,
rfreez.

PS: Many times i think... "screw all this, just get an SD702 and a couple of mics", but that only works for the jobs that are unlikely to make me money... and this is third world india, and i am not rich, so i cannot afford multiple setups :)

rfreez has provided a quantity of things to think about. I just have the time to respond to this one thing right now...

rfreez wrote: Many times i think... "screw all this, just get an SD702 and a couple of mics", but ...i cannot afford multiple setups :)

I totally agree with this ECONOMIC consideration. If one is going to need a DAW to perform post-production (editing, mixing, mastering), it might as well serve for the recording process, as well. Since I have found lap-tops to be completely adequate and reliable, this is the choice I have made. Having a dedicated remote device like a 702 or Nagra is very slick, and a nice luxury. I, however, feel it is economically wasteful.

Zilla wrote: Having a dedicated remote device like a 702 or Nagra is very slick, and a nice luxury. I, however, feel it is economically wasteful.

Hmmm...

To me, 12 months ago a statement like that would've been waving a red flag in front of a bull! But these days I find myself in agreement; laptop-based systems have become very reliable over the last couple of years.

I doubt there would ever come a time that I'd choose a laptop-based system over my Nagra V for any job that was within the Nagra's capabilities (in terms of inputs, tracks and required sampling rate). It is too well designed to become technically or ergonomically supplanted by a laptop-based system. But from an economic point of view, the laptop-based system makes sense; the savings stack up nicely against the compromises.

My current laptop is an IBM ThinkPad (T43) and it has totally changed my perception of laptops. It is such a reliable and rugged machine. After 18 months of use, including three trips to the Himalayas (for general computing duties, email, and backing up files only) it has won my trust. I've recently been contemplating hooking an audio interface up to it as a secondary system in case something happened to the Nagra (heaven forbid!) and also for multitrack work.

The ThinkPad can't go where my Nagra V goes (you can't use a laptop-based recording system while hanging over the side of an elephant or running through a nomad market following a drunking musician who has a great voice) but for the more sedate jobs, it's a viable solution that makes good economic sense.

A Nagra or Sound Devices or similar is fantastic for recording, but that's all you can do with it...

rfreez wrote: The Apogee Ensemble, 2 x AEA TRP, basic power conditioner and headphone amp will fit into a 4 space rack... the rest of the stuff will fit into a couple of boxes... For most situations this should be portable enough...

This is a system I would call 'transportable' rather than portable! Nonetheless, it addresses all of your needs - assuming you had a source of remote power, as discussed earlier in this thread. I can't think of a significantly better alternative unless you can afford one of those Cantors. [Dammit, just peed my pants again. Excuse me...]

Back again.

Have you checked out the Metric Halo products? Their Mobile I/O 2882 might be a worthwhile alternative to the Ensemble. It appears to have four balanced mic ins for your condensers, and four TRS line inputs for the outputs of your TRPs. Perfect, and you're not paying for XLR mic inputs you don't need. It also has a "DC power system for wall, FireWire bus, and battery operation world-wide". Looks like you could pack it into a laptop bag with the laptop. Perhaps it is better suited overall to your remote applications than the Ensemble?

What headphone amplifier are you thinking of? It is hard to go past the Behringer PowerPlay Pro units in terms of bang for buck. Especially the HA8000; eight stereo headphone amps, each capable of driving two sets of cans. That means you can have up to eight musicians with individual level controls, or up to sixteen if you pair them up. How many headphones do you have? Are headphones on the shopping list?

With all of that stuff crammed into a 4U rack and considering the temperatures in India, maybe you'll need a larger rack to allow for some ventilating space between units?

Have you checked out the Metric Halo products? Their Mobile I/O 2882 might be a worthwhile alternative to the Ensemble.

Two days ago I used a uln-2 with a pair of cascade ribbon mics... incredibly clean and inspires much respect.... it offers 72 dB of gain on the microphone inputs...

The 2882, however offers only 40 dB of gain, and I know beyond a point of doubt, that it is insufficient for many purposes... particularly with ultra SDC mics from earthworks and the like...

The Ensemble offers 75 dB of gain on the mic inputs... The other reason why the Ensemble makes sense for me is that it can function as a stand alone converter... I've been thinking of getting an m-audio box with ADAT inputs so that I can run Pro Tools LE... Most of the bigger studios where I do tracking work have PT, and It'd make things much easier.

What headphone amplifier are you thinking of?

[[url=http://[/URL]="http://www.furmanso…"]Furman HA6-AB [/]="http://www.furmanso…"]Furman HA6-AB [/] Its got some great, practical features...

It is hard to go past the Behringer PowerPlay Pro units in terms of bang for buck.

Well thats what I thought... I have a Behringer HA 4700 (its a 4 x 3 device, about $30 cheaper than the HA 8000) at my studio, it served me for just about a year (well, sort of... one of the 4 channels never worked, but I wasn't going to ship it back to the US to get that sorted, the remaining 9 channels was plenty much for my overdub booth... ) I called my tech guy and he said that its most likely got surface mount components and will probably have to be junked :( In any case I have not followed up on it, i'm using a 4 channel cheap ass standby that my tech made for me, for now. Anyway, I've begun to sort of be very wary of them... i used to monitor through a small behringer mixer, but on a vague suspicion, I bypassed it and connected my monitoring system directly to my 2408 mk3 and the difference was bloody obvious... And i ain't got no golden ears on the sides of my head...

On another note, I just got the most recent edition of "Recording" magazine, which has a review of the TRP... Review sounds sort of lukewarm to me... basically Scott Dorsey says that it greatly extends the upper frequency response of ribbon mics (albeit in a smooth way), and also suggests that it may be a bit too much in some caes, and, besides extending the HF range may actually deny us the classic ribbon sound... anyhoo... Also he strongly recommends not trying it with conventional moving coil mics, which is a deal breaker for me... second hand info... it bugs me to no end that i hardly get to hear any interesting gear, here in india...

thanks for the discussion y'all...

rfreez wrote: The 2882, however offers only 40 dB of gain...

Only 40dB of gain? Are you serious?

Looking at the pdf manual I just downloaded, that appears to be the case. How under-achieving...

rfreez wrote: The Ensemble offers 75 dB of gain on the mic inputs... The other reason why the Ensemble makes sense for me is that it can function as a stand alone converter...

Good points.

rfreez wrote: I have a Behringer HA 4700 [snip] at my studio, it served me for just about a year [snip] ...one of the 4 channels never worked [snip] I called my tech guy and he said that its most likely got surface mount components and will probably have to be junked

Yeah, I am sure it will all be surface mount. They may as well save extra money on screws and spot-weld the box shut, because it is certainly cheaper to buy a new one than it is to repair it.

The Furman product looks good, with the ability to drive speakers and so on.

rfreez wrote: The 2882, however offers only 40 dB of gain, and I know beyond a point of doubt, that it is insufficient for many purposes... particularly with ultra SDC mics from earthworks and the like...

But your earlier stated goal was...

rfreez wrote: ...low noise overall is important

Along with the ultra small condensers, you also mentioned ribbons. Both types of microphones are much noisier than more normal sized condensers. So it appears that either...

a) You where mistaken about your previous goal. The imparted tone/timbre of these particular mics is actually more important to you than low noise.

b) Noise is still important but you do not fully grok microphone noise specifications.

If (b) is the case, you should realize that even with the cleanest pre-amp, the ribbons and ultra sdc will still be much noisier than a mic with greater sensitivity. One would rationalize that if noise is important, it would be wise to select a mic with high sensitivity and low self noise. Therefore ultra sdc and ribbons may need to be rejected. This then allows us to relax the gain requirement in the mic-preamp. We can then fit this new insight with our other goals (cost, portability, power consumption) to correlate final criteria from which we may choose a product (or design/build our own).

I was hoping I had planted a seed for discussion which would analyze the problems first; list technologies and techniques which help solve them and reject others, and then find available products which most ideally fit our needed criteria. So far the discussion has been the opposite. Searching for products first is like waging the dog by the tail. Often problems are not studied at their root, and a less then ideal solution is wastefully purchased.

I was hoping I had planted a seed for discussion which would analyze the problems first; list technologies and techniques which help solve them and reject others, and then find available products which most ideally fit our needed criteria. So far the discussion has been the opposite.

Can you help me understand what you mean? As far as the topic goes, I have found the most suitable solution (thanks to everybody). Then upon your suggestion that maybe we can find a better "system", as things are quite open, I detailed my requirements, the sort of work i do and the list of solutions i have found so far... i was inquiring if there are any better ideas.

Along with the ultra small condensers, you also mentioned ribbons. Both types of microphones are much noisier than more normal sized condensers. So it appears that either...
a) You where mistaken about your previous goal. The imparted tone/timbre of these particular mics is actually more important to you than low noise.
b) Noise is still important but you do not fully grok microphone noise specifications.

zilla, i have already admitted that i'm a novice in the serious acoustic music recording. But i have used most types of microphones, most recently, a couple of ribbons (with much joy) are being tested everyday. And i have used avenson sto2s extensively (ultra sdc, 28 dBA noise spec). I do very much like the timbre of the mics in certain applications (relatively loud percussion, mostly), but when i try them with solo violin, veena or other such, noise becomes audibly disturbing... when i said low noise overall is important, i meant that because i have a fancy for using mics that have high self noise, i would like the rest of the system to be as sympathetic as possible. I should have been clearer.

Incidentally, i record one project every year with a dutch guy who is very into minimalist modern music. He uses a lot of barely audible noises and suchlike in his work. I would never use the avensons or ribbons on him. I use the least noisy mics that i can get my hands on. Tone is a little less important here than noise levels. So different horses for different courses, and i would not want the preamp to be the limiting factor.

Also, i have a preconception that the last 10 dB of gain on most preamps tends to be quite noisy. Anybody care to clarify? (on the occasions that i have used high end pres, i've never had to drive them that hard, but on mackies and FMRs and RMEs, and Joe Meeks, that seems to be the case). Which is why i felt the 40 dB that the 2882 offers will be quite a bottleneck.

Anyhoo, what does "grok" mean :)

Respect,

rfreez wrote: Anyhoo, what does "grok" mean :)

As from the book "Stranger in a Strange Land" by Robert Heinlein. Basically to have a very deep, internalized understanding of something.

rfreez wrote: Also, i have a preconception that the last 10 dB of gain on most preamps tends to be quite noisy. Anybody care to clarify?

Probably because single-stage pre-amps (the majority) start to run out of open-loop gain. As you increase the gain of a typical amp, you are actually DECREASING the amount of negative feed-back. NFB is used to lower distortion and noise in an amp circuit. For example, lets say you have an amp with 60dB of open-loop gain and you set the forward gain to +35dB. This leaves you with 25dB of corrective NFB to lower noise and distortion. Now lets turn up the gain to +55dB. This leaves only 5dB of NFB, so the output will now be 20dB noisier than at the 35dB setting. This also explains why many preamps sound different at different gain settings. Its due to varying amounts of NFB.

Zilla wrote: For example, lets say you have an amp with 60dB of open-loop gain and you set the forward gain to +35dB. This leaves you with 25dB of corrective NFB to lower noise and distortion. Now lets turn up the gain to +55dB. This leaves only 5dB of NFB, so the output will now be 20dB noisier than at the 35dB setting.

The reason it sounds 20dB noisier with 55dB of gain rather than 35dB is that you are amplifying the noise of the input by another 20dB. Very little of the extra noise is due to the reduction of NFB.

The input noise is made up of thermal noise from the source impedance plus noise generated in the input stage before the feedback loop. You reduce the first factor by keeping input impedances low and the second factor by appropriate circuit design. It's a big subject that occupies the minds of audio circuit designers the world over, and has been covered in other threads and on other boards. It's also a much wider topic than audio - medical electronics, radar, communication receivers all challenge designers to produce the lowest noise inputs and still stay within a budget.

Boswell wrote: The reason it sounds 20dB noisier with 55dB of gain rather than 35dB is that you are amplifying the noise of the input by another 20dB. Very little of the extra noise is due to the reduction of NFB.

Yes, there are are a multitude noise sources to consider (power supply, grounding, etc..). In my (imperfect) explanation, I was trying to address rfreez's observation of pre's that become extremely noisy at high settings. It has been my experience that many pre's will suddenly "give up the ghost" above a certain setting; when the noise makes a marked, exponential increase where the expected s/n ratio is not maintained. I attribute this to running out of olg, but I am sure that is not the only mechanism.

Short on the generator idea.

Honda makes some portable and quiet generators. They are the Honda EU series.

I'v tested the Honda EU10i. Its light and very quiet.
The specs sais it gives 900Wrms and gives 52-57dB@7. I have no idea why they list it at 7meters, but thats what the specs sais.

They also have a 12v outlett of 8,3A
-
1 full tank gives you 4,5 hours on 100% load and 8 hours on 25% load.
-
Just a tip.

The solarpannel solution sounds nice thow :D

edit: Oh!. and they are computer controlled so you can parallell two of them to double the effekt. Funny and possible very usefull.

Zilla wrote: It has been my experience that many pre's will suddenly "give up the ghost" above a certain setting; when the noise makes a marked, exponential increase where the expected s/n ratio is not maintained.

I have noticed this often, especially on mic preamps built into mixing consoles. In my experience, the exponential increase usually begins just beyond the 2 o'clock position on the gain knob. So whenever I find myself needing to put the gain knob at 2 o'clock or higher, I contemplate using a more sensitive mic...