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Author Topic: What Battery Preamp (w/48v) to expand MixPre?  (Read 4733 times)

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SMsound

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What Battery Preamp (w/48v) to expand MixPre?
« on: April 16, 2021, 07:14:51 PM »
I ended up with a MixPre 6 for classical/opera recording after copious reading here, and it's been fantastic. However, sometimes I really could use 6 mics instead of 4 (i.e. get mics on MixPre inputs 5 & 6 via the 1/8" TRS input).

What are some options you're all using for an external 1ch or 2ch preamp with 48v power that can be battery powered like the MixPre?   Ideally I'd like the preamps to be similar to Sound Devices' (i.e. clear/neutral).

Offline old and in the way

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #1 on: April 16, 2021, 07:56:38 PM »
If you have a spare 1300 the sonosax sxm2d2 is bad ass and the pres are world class . if no spare coinage there are Sound devices pre's that can be had on ebay or maybe the yard sale

Offline DavidPuddy

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #2 on: April 16, 2021, 08:41:21 PM »
Sound Devices Mixpre/Shure FP24

They pop up in the yard sale every now and then
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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #3 on: April 16, 2021, 08:43:03 PM »
The standard answer here is going to be the Shure FP24 or Sound Devices mix pre (the original older, design) They are both not too expensive used, have the same electronics and can be internal battery powered. (Although we use our Mix Pre with an external battery typically.)


edit to add: LOLz- puddy must have beaten me to post by seconds!    LOL
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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #4 on: April 16, 2021, 09:03:47 PM »
I have to agree that various MixPre preamps work well. I use a USB MixPre2 on channels 5 and 6, but also am very happy using a Naiant Tinybox which is considerably smaller. Those too pop us for sale from time to time.
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SMsound

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #5 on: April 17, 2021, 02:31:27 AM »
The standard answer here is going to be the Shure FP24 or Sound Devices mix pre (the original older, design)

Thank you all---this is great. Would it be correct to say that the FP24/Mixpre-D sound the same as the Sound Devices MM-1 and MP-1 (single channel battery-powered preamps)? They all seem to have identical 66dB gain.

Also, looks like Shure made various other mixers in the FP line, like the FP33. Were these also made by Sound Devices? Do you all prefer the FP24 just because 2 pres is a convenient number?
« Last Edit: April 17, 2021, 03:26:11 AM by SMsound »

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #6 on: April 17, 2021, 09:31:32 PM »

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #7 on: April 17, 2021, 10:12:44 PM »
If push came to shove and I needed phantom power and 20 dB gain on inputs 5-6 I would use what I already own, the Beyer MV100. 2 channels XLR in, mini or RCA unbalanced outputs only. Powered by 2x 9v batteries, runs approx 5 hours on a pair of Neumann KM140s before gain drops.


I prefer the Shure FP24 or MixPre2 but I bought this thing a long time ago and it still works great. Same form factor as Sonosax SX-M2 but rather different circuitry.
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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #8 on: April 18, 2021, 01:09:47 PM »
Some other small two-channel pre-amp options are the Aerco MP-2 and the audioroot offerings. I don't have any personal experience with the audioroots, but I have heard some nice recordings made with them. I love my Aerco; it has a reputation for being "warm", but I think it is pretty transparent.

Offline morst

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #9 on: April 18, 2021, 10:19:58 PM »
Some other small two-channel pre-amp options are the Aerco MP-2 and the audioroot offerings. I don't have any personal experience with the audioroots, but I have heard some nice recordings made with them. I love my Aerco; it has a reputation for being "warm", but I think it is pretty transparent.
Do you have to remove 4 philips screws from the back of the Aerco to change batteries?
There was an old box called a Reutelhuber, which led to the N-Box, I believe, via the R-Box, and the Oade Brothers sold some nice 2-channel units of their own design and construction.
Aerco, Oade and the BillBox (Bill R!) were all quite highly rated for their time, but I wonder how well they stand up to our modern RF world of wifi and cellphones etc?
I used to run my KM140's with the "active cables" but when I got my Sound Devices Mixpre6, I heard crazy interference when I plugged them in and listened with headphones. So much for miniature mounting options!
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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #10 on: April 19, 2021, 07:04:59 AM »
^ There are two options for internal powering of an Aerco: either three nine volt batteries or rechargeable LiPos. The LiPo option has been available for quite some time; my Aerco is a decade old and has them. The only issue with those is that the spacing is pretty tight, so replacing them is not super easy. I seem to recall that someone here (spyder9?) decided to abandon the rechargeables for this reason, although I was able to find some new ones (with a bit of effort). You need to open the case for the 9Vs, but not the LiPos. They are also quite flexible with respect to external powering. Per Jerry (Chamkis), "there is a built-in switching power converter to provide +/- 16 volts for the preamp and 48 volts for the mic, so you can also feed 9–18 volts DC in an external coaxial power jack on the side. The external power jack is floating so you can use a positive or negative or no ground system, so it's very flexible about sharing camera or other available power."

Jerry also says that they are very well shielded with respect to RF. Anecdotally, I have never heard any interference (even when using my phone next to the pre), but that is a sample size of one!

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #11 on: April 19, 2021, 08:04:55 PM »
i might be open to parting with my Shure FP24, its pretty minty. pm me
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Offline morst

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #12 on: April 19, 2021, 10:39:28 PM »
^ There are two options for internal powering of an Aerco: either three nine volt batteries or rechargeable LiPos. The LiPo option has been available for quite some time; my Aerco is a decade old and has them. The only issue with those is that the spacing is pretty tight, so replacing them is not super easy. I seem to recall that someone here (spyder9?) decided to abandon the rechargeables for this reason, although I was able to find some new ones (with a bit of effort). You need to open the case for the 9Vs, but not the LiPos. They are also quite flexible with respect to external powering. Per Jerry (Chamkis), "there is a built-in switching power converter to provide +/- 16 volts for the preamp and 48 volts for the mic, so you can also feed 9–18 volts DC in an external coaxial power jack on the side. The external power jack is floating so you can use a positive or negative or no ground system, so it's very flexible about sharing camera or other available power."

Jerry also says that they are very well shielded with respect to RF. Anecdotally, I have never heard any interference (even when using my phone next to the pre), but that is a sample size of one!
That's insanely cool that the power input is not polarity-dependent!?!!
For LiPo I guess you repurpose a camera or cellphone battery of appropriate physical size and power capacity!?
(I had to look up with a LiPo was!
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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #13 on: April 20, 2021, 08:58:48 AM »
^ The LiPos Jerry used were from those fancy remote-controlled helicopters. When I felt like I should replace them, I went about 75 miles to a big RC shop, sat with their battery guy, opened up my Aerco, and let him take a look at the batteries and connectors. It took him about fifteen minutes to get me set up with some new ones...

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #14 on: May 09, 2021, 05:26:26 AM »
There's Marenius add-on mic amp for the Sound Devices 633 sale on BBList.
The asking price is €400

https://www.bblist.co.uk/item.php?item=69562

SMsound

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #15 on: May 09, 2021, 11:48:00 PM »
This thread has been super helpful.

What has been everyone's experience with the 1/8" TRS input (channels 5/6) on the MixPre-6? 

I keep looking at the great options in this thread, then cringing at the thought of my tracks depending on a 1/8" TRS connector... :hmmm:

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #16 on: May 10, 2021, 12:58:16 AM »
This thread has been super helpful.

What has been everyone's experience with the 1/8" TRS input (channels 5/6) on the MixPre-6? 

I keep looking at the great options in this thread, then cringing at the thought of my tracks depending on a 1/8" TRS connector... :hmmm:

It's not bad at all in my limited experience. Of course, it's noisier than the XLR inputs but if you're recording amplified music, it's not an issue.
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SMsound

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #17 on: May 10, 2021, 03:59:50 AM »
It's not bad at all in my limited experience. Of course, it's noisier than the XLR inputs but if you're recording amplified music, it's not an issue.
Thanks.  I'm recording classical/opera, so noise matters---how much extra noise are you getting?  Any trouble with static from the 1/8" TRS connection wiggling/not being perfect? I do wish the mixpre's would have used 1/4" TRS for some extra surface area to make the connection.

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #18 on: May 10, 2021, 04:47:54 AM »
Thanks.  I'm recording classical/opera, so noise matters---how much extra noise are you getting?  Any trouble with static from the 1/8" TRS connection wiggling/not being perfect? I do wish the mixpre's would have used 1/4" TRS for some extra surface area to make the connection.

The TRS jack on the MixPre has a screw thread. There are actually TRS connectors that can screw onto such a thread. I have attached a picture of the connector I'm using with my tinybox. These types of TRS connectors are usually used on pocket transmitters. However, I currently don't have my MixPre here and therefore can't confirm that the screw thread of the MixPre sticks out enough for the connector to be able to lock onto it. But it might be worth a try. In the worst case you might have to remove the nut from the MixPre's TRS jack (don't worry - the connector is fixed to the PCB, the nut is not needed to secure it).
« Last Edit: May 10, 2021, 04:57:04 AM by Sebastian »

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #19 on: May 10, 2021, 01:09:41 PM »
The TRS jack on the MixPre has a screw thread. There are actually TRS connectors that can screw onto such a thread. I have attached a picture of the connector I'm using with my tinybox. These types of TRS connectors are usually used on pocket transmitters. However, I currently don't have my MixPre here and therefore can't confirm that the screw thread of the MixPre sticks out enough for the connector to be able to lock onto it. But it might be worth a try. In the worst case you might have to remove the nut from the MixPre's TRS jack (don't worry - the connector is fixed to the PCB, the nut is not needed to secure it).
Holy wow, will ya look at that?
Mine's got a thread exposed which MIGHT be enough to get some grab?! My room is super dusty.

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SMsound

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #20 on: May 10, 2021, 05:26:24 PM »
^^ Just checked my MixPre-6 (Gen 1)---looks like I have just 1/4 of a thread exposed. Might by a YMMV thing with screw on TRS.

I am still really curious about extra noise from using an external pair of preamps into the 3.5mm TRS connector---can anyone comment (before I pull the trigger on some nice battery preamps)

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #21 on: May 10, 2021, 05:38:59 PM »
I am still really curious about extra noise from using an external pair of preamps into the 3.5mm TRS connector---can anyone comment (before I pull the trigger on some nice battery preamps)

From a technical standpoint any extra noise depends on the external preamp being used. The 3.5 TRS connector does not "add" any noise. It probably has a similar signal path to the ADC as the rest of the inputs, with just a different gain stage. And the specs don't list a different equivalent input noise level for it. So as long as you're using a low-noise external preamp, I don't think you'll have any problems. Especially if you're running the Aux/Mic input at unity gain.

SMsound

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #22 on: May 10, 2021, 06:01:35 PM »
I am still really curious about extra noise from using an external pair of preamps into the 3.5mm TRS connector---can anyone comment (before I pull the trigger on some nice battery preamps)
I don't think you'll have any problems. Especially if you're running the Aux/Mic input at unity gain.

^ Very helpful. I'm looking at a Shure FP24 external 2ch pre (and some of the other Sound Devices ones). If I understand correctly, then you're saying that on my MixPre-6, I should set the gain on Ch. 5 and 6 to zero, and use the external FP24 pre's to add gain to the mics?
« Last Edit: May 10, 2021, 06:47:56 PM by SMsound »

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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #23 on: May 10, 2021, 10:43:08 PM »
zero on the mixpre may or may not be "ideal", but its a fair bit of testing to determine the optimum level for S/N, and diminishing return at that.

the "tape out" of an FP24 is an easy mini-to-mini-connection to the mixpre aux in and runs at +11dBFS
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Re: What Battery Preamp (w/48v) to expand MixPre?
« Reply #24 on: May 11, 2021, 01:29:54 AM »
zero on the mixpre may or may not be "ideal", but its a fair bit of testing to determine the optimum level for S/N, and diminishing return at that.

the "tape out" of an FP24 is an easy mini-to-mini-connection to the mixpre aux in and runs at +11dBFS


Thanks!  Just called around and have a MixPre-D on the way.  I didn't realize the MixpPre-D and FP24 have 3.5mm tape output.  I've actually never used a tape output before before---is there any disadvantage to using it vs. the XLR outs? (Cringing again at the thought of my recordings depending on not one, but two 3.5mm jacks...)

 I had planned to either:
-Buy/make a two-XLR-F to 3.5mm TRS stereo breakout cable to go from the MixPre-D's two XLR's outputs to the MixPre-6 3.5mm TRS input. 
Or
-buy/make an TA3F (mini XLR) to 3.5mm TRS cable to go from the Mixpre-D's mini XLR unbalanced output.



Thank you all for all of the help!

 

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