Would simple splitter box work?

I was thinking to make a simple splitter box since I am building so many BA combos. The idea is to have one in (from the mic) and four outs (to preamps) for a quick mic pre shoot out to see what suits the best.

Would this work or would I run into some kind of problems since I am feeding four preamps from one mic at the same time?

Yes, loading of the mic won't be optimal, as you usually try to get best power-matching at interfacing to acheive lowest noise. So there's a real chance (depending on the actual mic pre architecture) that the mic will be loaded four times harder than optimum.

An active splitter is probably the way to go - but that isn't without problems either.

Jakob E.

how can we get the mic optimal loaded when hooking up with preamps with transformers? Is there a compensation possiblity to avoid 4fold loading in case of Purusha's setup? In fact I would like to build splitters to allow for live recording shows in case there's no splitterrack available at the venue/PA.

[quote author="tony dB"]how can we get the mic optimal loaded when hooking up with preamps with transformers? Is there a compensation possiblity to avoid 4fold loading in case of Purusha's setup? In fact I would like to build splitters to allow for live recording shows in case there's no splitterrack available at the venue/PA.[/quote]

That's what I never completely understood from those mic-splitter-TXs: they're usually 1:1:1... so the total impedance presented to the mic is lower (IIRIC; at least the 1:1:1:1 I got in the Beyer Groupbuy was like that).

Making the mic-splitter-TX a 1:N:N:N... prevents the heavier mic-loading but would overload the preamp quicker. Any other drawbacks to this approach ?

(As an example, let's assume a triple feed: now each preamp must look like three times its old input-Z.
A mic-splitting-TX with three secondaries 1:sqrt(3):sqrt(3):sqrt(3) would work then. Please correct me if I'm overseeing something.
And note I'm talking about an added TX, not about any TX that might be at the input of the mic-pre's themselves.

Regards,

Peter

I think 3:1+1+1 would be a safer guess..

this still is rather crytic to a poor soul as myself...
Any good reading recommended?

[quote author="gyraf"]I think 3:1+1+1 would be a safer guess..[/quote]
Oops, you're right of course, I got the direction reversed.

But why 3:1+1+1 and not sqrt(3):1+1+1 ?

And apart from 3 or sqrt(3) & direction, would a ratio in the splitter-TX an sich be an usable thing at all ?

Regards,

Peter

But why 3:1+1+1 and not sqrt(3):1+1+1

Because the power transfer from the microphone will, in case of 3:1+1+1, be 1:1 overall. The sqrt(3):1+1+1 (=1.7:3) will load the mic with too low a Z.

Downside of the 3:1+1+1 is that you loose 9-10dB of signal level - but this is unavoidable..

Jakob E.

[quote author="gyraf"]

But why 3:1+1+1 and not sqrt(3):1+1+1

Click to expand...

Because the power transfer from the microphone will, in case of 3:1+1+1, be 1:1 overall. The sqrt(3):1+1+1 (=1.7:3) will load the mic with too low a Z.

Downside of the 3:1+1+1 is that you loose 9-10dB of signal level - but this is unavoidable..

Jakob E.[/quote]

It's obvious I'm goofing here. So let's write down what went on in my head so that we can pinpoint where I made my error :wink:

I didn't consider power but just impedances. I assumed a 200 Ohm source & say 2k mic-pre loading (for one single micpre).
In order to maintain that 2kOhm load for the mic in case of three of such mic-pre's connected I figured that each micpre should now look like 3 times that 2kOhm.
So impedance-ratio 3, and turns-ratio the sqrt of that.
Let's assume three separate TX's inserted, each with its primary connected to the mic & its sec to it's respect. mic-pre input. Each mic-pre now looks like 6kOhm to the mic, and since we have three of them in // we get 2kOhm.

Next step is to merge those three TXs into one TX with turns-ratio sqrt(3):1+1+1 ('impedance-ratio' '3:1+1+1'). Still the same, correct ?

Where did I make the thinking-error ? Did we confuse turns & impedance perhaps ?


Thanks,

Peter

[quote author="clintrubber"]
In order to maintain that 2kOhm load for the mic in case of three of such mic-pre's connected I figured that each micpre should now look like 3 times that 2kOhm.
[/quote]

Peter, will the three preamps connected to the secondary not appear in parallel when the mics are "looking" into the secondary?

-------------2000
200---------2000
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[quote author="rodabod"][quote author="clintrubber"]
In order to maintain that 2kOhm load for the mic in case of three of such mic-pre's connected I figured that each micpre should now look like 3 times that 2kOhm.
[/quote]

Peter, will the three preamps connected to the secondary not appear in parallel when the mics are "looking" into the secondary?

-------------2000
200---------2000
-------------2000[/quote]

Hi Roddy,

Yes, but the see 6k each, not 2k as I think to understand it:

Each mic-pre has its own indep. secondary in the mic-splitter-TX plan. Because of the ratio they look like 6kOhm and three of such TX-secondaries in // give 2kOhm. At least in my mind, but that must be wrong somewhere since I trust Jakobs TX-knowledge & -experience a lot more than my own :!:

Bye,

Peter

Let's bump - can anyone tell me where I made the thinking error three mails up ?
I'd like to understand it.

Thanks :thumb:

Peter

that makes 2 of us...

Its not possible to do this without a major compromise, weather it be not loading the mic correctly or adding an extra splitting transformer (which would then be loaded with 150ohms, for 3 pres, and so would need to be...some bizzare kind of splitter+step down transformer) or making a unity buffer with opamps that keeps the mic and pre loaded the same. Its just not possible in any way I can think, seeing as youre listening for fine tonal differences that are hugely effected by loading/gain structure and the like.

Just patch the mic into each pre and listen. It works for me!


M@

[quote author="mattmoogus"]
Its not possible to do this without a major compromise, ......

Just patch the mic into each pre and listen. It works for me!


M@[/quote]

Bottomline, a fast setup for Purusha would be a switch rather than a tranformer. Switchable between all the pres he wants to check/compare.

sorry, but the above has bamboozled me, but i can see where the first question came from.

if 1 mic feeds 4 pres at the same time, then all pres are getting exactly the same sound source, no slight atmospherics or other voodoo for some body to complain about, 1 source in and straight to 4 tracks.

i would love to build something like this, but it would have to be totaly transparant, please tell me, how do i build this

it's exactly this what's been discussed here, it seems that no passive solution is possible, as the transformers involved mess with the impedance (loading) of the mic AND the pres connected too. Even subtle changes in impedances can alter the mic's and/or pres responses in dynamics and frequenties, making the results from this setup misleading.

yeah... it seems like one of those situations where the very act of testing it disturbs the circuit enough to make the test inconclusive. a switcher makes more sense. In the end you'll probably be switching between the different channels anyway to compare.