. um, returning to the topic of this thread (but maybe not 'to die for')...
I am developing a mic preamp solution for myself specific to location ribbon mic preamp-amplification. Since there seems to be plenty of Royer enthusiasts in this forum, maybe I could layout my ideas and get some feedback. Anybody interested?
Comments
Pin 1 and 2 are switched around on that T-power. Tube Mic I rem
Pin 1 and 2 are switched around on that T-power.
Tube Mic I removed the 2 caps on the output by transformer, I think they were to block P48 if you have it turned on by mistake, which I hear can really do a number on your transformer. Also but in a Cinemag trans and Peluso Capsule. Had a bigazz audio grade cap for the final before transformer but couldn't fit it into the body. Sounded pretty good until I focked it up good. Never was satisfide with the noise floor. Probably would work good for a rocker screaming into it. Don't worry about me shocking myself.... I already did it working on the thing. Nothing like a train transformer though!
Speaking of smoking, I already smoked the Time Code card on a Fostex FR-2. Nice puff of smoke from the thing while hooking it up to a TC slate.
We bought 2 of those FR-2s and 1 was DOA and the other I smoked. Fostex has really fast service. Big piece of plastic though!
I have been refining things with this project for quite a while.
I have been refining things with this project for quite a while. I finally tested the unit on the bench yesterday and thought I would post the outcome...
Distortion: 0.004% (+60dB gain, output @ +18dBu into 1.2kohms)
Dynamic range: 108dB
CMRR: >80dB
Frequency Response: 20Hz-40kHz (±0.05dB at all gain settings)
Interchannel Matching: ±0.05dB (20Hz-40kHz at all gain settings)
Interchannel Isolation: 110dB
Battery Life: 10hrs. at spec (plus an addition 10hrs under spec).
As you can see, my unit is measuring extremely well. Now for the listening tests.....
BRH wrote: Just 60db gain? How about putting a tranny in it? If
BRH wrote: Just 60db gain? How about putting a tranny in it?
If you really needed more than 60dB, you could add a transformer (sorry, I just can't bring myself to type t****y). This would get you an extra 6-20dB of gain depending on the model. There would be performance trade-offs, as usual.
My approach was to modify the gain structure of the converter inputs such that I would never need more than 60dB in the first place. I am recording tonight with the latest revisions to the pre-amp. Will let you know how it comes out.
So... what's the verdict? Ya know, Scott..... I used to think t
So... what's the verdict?
Ya know, Scott..... I used to think transformerless pres were better, and maybe they were when using to record to analog tape, but now when using with digital, most transformerless unit's leave me cold. I find as I'm getting older (not much) that I enjoy just a little thicker sound... = tranformer. Not much... not pushing it hard. Benefits are more gain when used correctly. Distortion isn't enough to worry about.
I'm also finding I like just a bit closer mic placement than I used to, even for classical. Funny what age can do for you!
Well, its usually bad form for the cook to comment on the meal,
Well, its usually bad form for the cook to comment on the meal, but I can honestly say I am pleased. The one thing that I can concretely say is that these pre's are stupid quite. SF12 on classical guitar and I could hardly tell I was using a ribbon. Absent was the expected "ssshhsshhsshshshhsshshs"!
Maybe I could post a sample and get unbiased opinions, but I don't know how. Can anybody help?
Brooksy-Baby, I hear you. I like quality transformers and closer micing, as well.
http://www.speedyshare.com/ You can upload files up to 24Mb wit
You can upload files up to 24Mb without any registration and post a link.
I'd be interested in hearing a clip as well.[/url]
Thanks to bap I was able to upload 24/88 samples for everyone.
Thanks to bap I was able to upload 24/88 samples for everyone. I don't want to say too much now, as to avoid undue bias. But there is a thing or two you should probably know. This was a simple archival recording sitiuation of a live recital with limited sound check. Noise acoustically present within the venue included a 120 member audience and a video projector. The projector was mounted in the ceiling above the stage. Thanks to someone's brilliant installation, the projector could not be turned off! We therefore had to suffer with its power supply fan blowing through out the performance. And with the disclaimers out of the way, let the savaging begin...
solo gtr:
http://www.speedyshare.com/666390216.html
Maybe it's the video projector I was hearing. I would have gone
Maybe it's the video projector I was hearing. I would have gone in the back and start flipping breakers, if I was there. In fact, it might be a good idea for someone to come along with you, just for this purpose, and then after the damage is done (or the fix) they would leave, and you could claim you never knew 'said person'!
Pretty nice sound. I think the clarinet is miked a wee bit too close. Too much pad sound, other than that I like it. If those are your Royers, I like them.
How much was the pre turned up? And what was your input impedence?
I think you said 1.2K. If so, why did you choose?
I tried flipping breakers, no luck. The 1.2k I mentioned earlie
I tried flipping breakers, no luck.
The 1.2k I mentioned earlier was the load that the output of the mic pre was feeding under test. This to indicate that the pre can drive a low Z without disturbing it's performance.
The gain was +46dB, if memory serves. The input z of my pre is around 12k.
Cucco wrote: [quote=Zilla]Thanks to bap I was able to upload 24/
Cucco wrote: [quote=Zilla]Thanks to bap I was able to upload 24/88 samples for everyone.
Ahem....
(Dead Link Removed)
Just a thought -
Everyone is welcome to use it - just let me know.
I remembered Cucco's offer after mentioning the Speedyshare link! :oops:
He will post larger than 24Mb!
FWIW, it actually wasn't the projector making the noise. There
FWIW, it actually wasn't the projector making the noise. There was some sort of computer interface up over the projector to make it work. As of a week or so ago, the problem has been solved (was just there today working).
I'll download your samples and take a listen tomorrow. Looking forward to hearing it.
-Ben
stop Stop STOP! I apologies if anyone has said anything about t
stop Stop STOP!
I apologies if anyone has said anything about this before but...
I can't listen to this total utter crap about 'that' T-Powering and Phantom Powering from BRH.
T-Power/T12/Tonarder/AB Power (I believe predates P48/P12) works like this on a XLR plug (adjust pin numbers for signals according on tuchels)
Pin 1 - GND
Pin 2 - Hot & +12v
Pin 3 - Cold & -12v
The danger being this will cook a transformer in a microphone as the DC powering travels through the transformer and gets hot.
Phantom Powering works like this...
Pin 1 - GND
Pin 2 - Hot +48 (or +12/24)
Pin 3 - Cold +48 (or +12/24)
This configuration meaning that the DC doesn't travel through the transformer and blocking caps aren't needed (don't get me involved regarding colouring the signal with caps), it also means it's perfectly safe to use with dynamics, ribbons etc
I'd avoid plugging anything into a phantom powered input which doesn't need it, but it's not going to break if you do (as long as there's a transformer there!). If you plug anything other than a T12 mic into a T12 input, it could damage it because the circuit is completed through the transformer, where as phantom power does not get complete through the transformer as its both +DC.
I'm also lead to believe it's a bad idea to try invert phase by switching pins 2 and 3 when using T-Power
I'm yet to see a flatbed mixer which isn't a portable Audio Developments Mixer, or something designed for location sound for film which can provide T12 without an adapter. (not to say it doesn't exist), but most things with T12 are (google them) SQN's, Sound Devices Mixers, Pro Fostex, gear or any other ENG mixer.
/Rant.
Thanks,
John
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Six years later, it might interest everyone to know that this preamp project matured into a commercially available product. Realized as a coordinated system of 1U packages consisting of power, phantom and dc-coupled preamps. In this way a beneficially customized chain can be built. One can start small and grow into greater channel counts as needed.
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Next is the finalization of a companion, reference-quality monitoring unit.
Thanks for everyone's interest,
Scott
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interesting reading about Pueblo Audio now. I'm looking at other preamps for acoustic music and this looks interesting now. Anyone else use these?
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I don't have any real world experience with T-power. Looking at
I don't have any real world experience with T-power. Looking at it theoretically, T-Power is applied simularly to phantom power. However, the 12v supply has (loosely) one fourth the headroom that a 48V supply would have, therefore things will probably get crunchy as spl gets high. T-power still pumps the supply current down the same piece of copper that your signal is riding on, possibly causing undesirable interactions. T-power still needs blocking caps to keep the 12Vdc out of your preamp's inputs.
It is always best to avoid blocking caps. But there are times when you cannot avoid them. They are virtually always present in tube equipment. However, tube equipment usually has much higher input z as compare to solid state. This higher z allows one to use lower value capacitors which generally sound better than large value caps. For example, a typical phantom blocking cap on a ss mic input is 100uF. Compare that to a 0.1uF blocking cap on a tube pre-amp and you see the difference in value is a thousand fold.
Yo, BRH, on that mic you modded; Which caps exactly did you take out? Be careful, you could let several hundred volts leak into connected equipment, which in turn may start leaking smoke. Many phantom blocking caps are only rated at 63V max. Be careful of shock hazard.