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Sound Devices preamps

Discussion in 'Preamps / Channel Strips' started by aracu, Sep 30, 2005.

  1. aracu

    aracu Active Member

    I'm wondering if anyone who has used the new Sound Devices
    recorders could comment on the preamps...are they comparable to
    well liked transparant preamps such as Millennia, Grace, DAV etc.
     
  2. Sonarerec

    Sonarerec Guest

    I had a Sound Devices USBpre for a while, and the pres in that were better than Marantz but not even in the same universe as those you mentioned.

    Rich
     
  3. aracu

    aracu Active Member

    Thanks Rich, thats pretty much what I expected.
     
  4. DavidSpearritt

    DavidSpearritt Well-Known Member

    Do not lump the USBPre preamps in with the new generation in the SD recorders or the highend preamps in the 442. This is not a useful comparison.
     
  5. recordista

    recordista Active Member

    To elaborate a bit on what David brought up, the 442 (like other Sound Devices field mixers) has transformer-based preamps which are very immune to noise problems and consume very little power. My 302 can run 8-12 hours on 3 AA rechargeables! The 7-Series' lithium packs allow for a much larger power budget, and use a class A biased discrete frontend pair. I'd place them in the same league as the Grace.
     
  6. aracu

    aracu Active Member

    If they are in the same league as Grace pres it's very impressive
    for such a small device.
     
  7. Cucco

    Cucco Distinguished Member

    Wow Kurt -

    to place them in the same realm as the Graces is certainly a compliment! I don't mean to sound skeptical or cynical, but, really? :!:

    That's a hard thing to imagine - looking at the circuitry involved and what not, the Grace (IMO, one of the finest pres on the market) should smoke the SD pres. Though, I'm not trying to trash the SD pres. One of the location film guys up here uses the 2 channel SD and LOVES it. I'm just trying to wrap my head around that.

    I mean, I've done a lot of gigs with a pair of 201s and 4 mics to hard disc, but rest assured, that setup was pretty darned expensive. If I could get the same results out of the SD, I might just take the plunge. (Of course, it has to be added to my "To Buy" list and then all has to be re-prioritized, then I have to sell my wife on letting me drop my own hard-earned money on it..... Well, we'll see...)

    J.
     
  8. recordista

    recordista Active Member

    Where did you get Grace and SD circuit diagrams?

    Like Grace, Millennia, Midas, ATI, TRUE, and many other well regarded modern transformerless solid state designs, the 7-Series preamps use a class-A biased discrete LTP frontend followed by an IC (often an instrumentation amplifier) gain stage. The devil is in the details, of course (particularly with regard to things like supply rejection and overload at low gain settings) and different designs will often have have rather different distortion spectra.

    I still advise anyone contemplating the purchase of a 7-Series recorder to hold off buying external preamps until you have lived with the onboard preamps for awhile.
     
  9. aracu

    aracu Active Member

    Its interesting to hear your evaluation of these pres. If they are
    as good as dedicated pres such as Grace, than an ultimate
    minimalist recording chain could consist of one Royer sf-24
    mic and a Sound Devices recorder, very easy to transport.

    A way of completely maxing out a Sound Devices 744t and using
    it to it's full potential could be, for example, using a Royer sf-24
    through a Grant preamp, on it's channels 3 and 4, which have
    no internal pres, and running simultaneously 2 DPA 4006's
    through it's channels 1 and 2 internal pres and recording the result as two stereo or four mono wav files, to be able to also adjust the mix afterwards.

    If there is anyone reading this has tried using these pres/ADCs (Sound Devices 722 / 744t) for recording acoustic ensemble music, please let us know how it worked out for you.
     
  10. Cucco

    Cucco Distinguished Member

    In truth, I've never seen the SD innards. I have however seen the Grace (as I've owned/own/used) almost their entire product line. As for the Grace, I'm never content to look at the outside of a box of metal. Usually my first thing with any studio device is to pop the top. Only after I've looked at its guts do I rack it.

    (In truth, I know enough to make me dangerous, but I am no EE. I can usually recognize basic good design and I've seen it in the Grace. My only thought in it against the SD stuff is purely a size issue. Grace packs their components in there. Well, not really packs, but if you were to try to fit the Grace componentry into a SD device, you wouldn't have much room left for anything else.)

    I don't doubt their pres are quite good. I just have to assume that there would be some compromise given their size, what they share a chassis with and what power issues there are.

    J.
     
  11. aracu

    aracu Active Member

    I wonder how a Sound Devices 722 or 744t would handle an AEA r88 stereo ribbon mic, on it's own, if it could give it enough gain and impedence.
     
  12. recordista

    recordista Active Member

    Michael does make some beautiful gear.


    Have you looked inside a V3? You'll see a much tighter package (but the same basic design) thanks to the SMT componentry. Some users have commented that they prefer the sound fo the V3 preamp to that of the 201, possibly due to the shorter lead lengths and reduced number of dissimilar metal junctions. SMT is not inherently bad as most audiophile press would have you believe. There are quality metal film resistors and good caps available, but you won't find them in mass-produced gear.

    Being standalone preamps, the 201/801 (like the Millennia and others) use high rail voltages to make their +28 output spec and also require a very low output impedance for driving very long cables. As an integrated device, the 7-Series (like the V3) is able to relax those requirements a bit, since the preamps only need to be able to drive the ADC to FS (though you'll find that in order to increase S/N the input of modern ADC chips is heavily padded.) Lower rail voltages and a known output load usually translate into less heat dissipated in the driver stage of the preamp, allowing it to be squeezed into a smaller package. You might also notice that both the V3 and the 7-Series use their aluminum cases to dissipate a fair bit of heat.
     
  13. Cucco

    Cucco Distinguished Member

    The Lunatec is indeed a very nice pre. I also agree that smt is not necessarily bad - just a booger to fix.
     
  14. If there is anyone reading this has tried using these pres/ADCs (Sound Devices 722 / 744t) for recording acoustic ensemble music, please let us know how it worked out for you.
     
  15. mdemeyer

    mdemeyer Active Member

    I recently got a 744T and will be using it for some acoustic recordings this holiday season. Will do some comparisons with my normal rig (Hardy M1 into Benchmark AD2404-96).

    As part of my pre-flight checkout, I did some measurements of the A/D and mic pre in the 744T and found something very unusual in the mic pre. The noise floor of the mic pre (not the A/D through the line inputs) has a really high noise level at low frequencies, while being very quiet in the upper frequencies. Here are two plots showing the noise floor of the Hardy M1 (red) vs. 744T (blue). Both were terminated with a 150 ohm MF resistor, and the M1 was run into the 744T line inputs with the gain set to zero.

    (Dead Link Removed)

    (Dead Link Removed)


    You can see in the two plots taken at 40db and 60db gain (I usually operate somewhere in this range), that the 744T has a rapidly rising noise floor with decreasing frequency. The M1 is very slightly noisier from 800Hz up (at 40db gain) and quite a bit noisier at 60db gain above 100Hz. But its noise floor is dead flat, while the 744T is anything but. I'm expecting the 744T will sound quieter given the ear's sensitivity to noise vs. frequency, so am anxious to try it with my M130/M160 MS setup. It might sound really quiet!

    I sent these plots to Sound Devices, and they confirmed that this is the designed performance. They didn't say it specifically, but I asked if this was a form of 'noise shaping' to improve the weighted (and audible) noise level, and their response did not suggest otherwise.

    Hope you don't mind me cutting and pasting some of this from the other thread, but this thead has a title that might help more people catch this. Anyone seen this kind of performance in another piece of gear?

    Overall, I think the 744T, which I will use mostly to record 4-channels on dual AES inputs, is a really sweet unit and will lighten my load, speed setup, and cut down on the worries (and grey hair) inherent in PC-based live recording.

    More to follow after some real recordings are made...

    Michael
     
  16. ghellquist

    ghellquist Member

    I do. And I am generally always happy with the results.

    Here are (some not very good examples). A large church. Rehearsal, hence the talk. Soloist to the right of the stage. Mic stand about 15 to 20 feet from orchestra. No level settings, so both are increased about 15dB in post. Ran out of web space, if anyone has more I will be glad to post the files to you in original shape (44.1 24bit). (I will have to remove them in a few weeks to make room for next project)

    http://hem.bredband.net/trombonisten/SF24.mp3
    http://hem.bredband.net/trombonisten/Schoeps.mp3

    Mics are Royer SF24 and Schoeps MSTC64, same position. Direct into SD722. No processing.
    A little bit of noise is added by the mp3 process, most of it is from the location as such.

    I have several other examples with SD+Schoeps.

    Two are here, more what you would expect to hear from noise level. Not sure but these probably have low cut both.
    http://hem.bredband.net/b121263/F1.mp3
    http://hem.bredband.net/b121263/M1.mp3

    Gunnar
     
  17. aracu

    aracu Active Member

    HI GUNNER, really nice comparison. The Schoeps sounds
    sharper but the Royer sounds richer and less digital. I've
    been thinking of getting two Royer SF1's and using them
    as a stereo mic with an adjustable stereo angle.
     
  18. BRH

    BRH Active Member

    Very interesting about the 744 and the low frequency noise floor. I must add my 2 cents, for what it's worth. Haven't used the 744, but thought about buying the 702 or 702T.

    Consider this, for thought. These recorders were designed for film dialog, and generally would have the lows rolled off during post, so this low frequency noise would never be heard.

    I haved used the mix pre and seemed fairly clean & transparent. Not only that, you could run over it with a truck and it would still work, something that happens during film shoots.

    Anybody used the Fostex FR-2?
     
  19. aracu

    aracu Active Member

    I don't think you'll have a problem with the Sound
    Devices recorder pres and low frequency noise. It
    seems to be a theoretical issue which is not audible
    in recordings for some reason.
     
  20. aracu

    aracu Active Member

    I made a careful comparison of the Sound Devices pres
    with Gordon V pres the other day, using an extremely
    low output ribbon mic, a B&O BM5, (a mic which could
    probably make any preamp seem noisy if trying to
    record quiet instruments), and cranking the pres to 70
    decibals max. The Sound Devices pres had slightly more
    hiss, and had a definate over emphasis in the lower
    frequencies, compared to the Gordon, which had what
    sounded like a fine balance from low to high frequencies,
    and sounded much more three dimensional and transparent,
    although also too hissy with this particular mic.
    A B&O BM5 mic modded with RCA ribbons has a
    frustratingly beautiful sound to go along with such a
    low nearly unusable output level for quiet sounds.
    The Sound Devices 744t has an interesting feature that I
    want to try out with other ribbon mics, which is that line inputs
    3 and 4 can be set to add up to 18 decibals to whatever
    the external separate preamp is set to. So a 70 decibal
    preamp can be used as if it had 88 decibals.
    It also has an ms monitor and ms monitor/converter to
    stereo, which work great. My only criticism is that it looks
    like you cannot monitor an ms pair with the remaining 2
    channels simultaneously, you rather have to switch back
    and forth between the two pairs of mics, if a pair is set to
    ms.
     

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