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Poll: Anyone interested in me posting mic pre samples

Discussion in 'Microphones' started by DonnyThompson, Feb 27, 2015.


Anyone interested in me posting audio comparisons of transformers and op amps on an ADK AP1 mic pre?

  1. Yes

  2. No

    0 vote(s)
  3. Don't Care

    0 vote(s)
  4. Go Away, Donny

    0 vote(s)
Multiple votes are allowed.
  1. DonnyThompson

    DonnyThompson Distinguished Member

    I'm willing to post audio samples of various Input Tranformers and Op Amps on an ADK AP-1 mic pre, if anyone is interested.

    But I don't want to go through the time and effort of doing this if it's not of interest.


  2. Boswell

    Boswell Moderator Distinguished Member

    Yes, very interested. Sounds like a fair chunk of work, though, so don't lose sleep because of it!
    pcrecord likes this.
  3. DonnyThompson

    DonnyThompson Distinguished Member

    I'm happy to do the recording, as it helps me to get to know the color/characteristics of each of the components, and combinations of the various trans and op amps - I just don't want to take the time to post them here if no one is interested. ;)

    But for you Bos... ? Anything. ;) LOL It's the very least I can do for you - after all the times you've helped me through the technical-electronics jungle... :)

  4. DonnyThompson

    DonnyThompson Distinguished Member

  5. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I'm always interested to learn how gear sounds. So yes, I'll listen to your samples very closely.
    May I suggest you use at least one mic everyone has (ex sm57) I feel that certain mics will get better prespectives on pre than others so at least a few are needed to compare.
  6. DonnyThompson

    DonnyThompson Distinguished Member

    well, I've already started, using a 414... I suppose I could do a few comparisons with a 57, though.
  7. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    You do as you please Donny. I suggested that because I'm sure more people have a sm57 that a 414, and it's always fun to hear how a good pre can make budget mic sound. ;)
  8. MrEase

    MrEase Active Member

    Hi Donny,

    I agree that it should be an interesting experiment but will need to be done in a very controlled way to get the most from the effort. Please make sure you keep as much as possible "equal" between takes!

    I find that it is always intriguing (as I'm sure Boswell does) to observe the different outcomes. What I find though is that many will condemn or praise some particular IC or other without taking in to account the circuit surrounding it. Op-amps have such varied characteristics that every circuit should optimised, so dropping in an alternative does not necessarily reveal the Op-amp but rather the circuit it's in. Nevertheless an interesting task but for me, as a designer, I'd also like to see the circuit schematic's that yield the results.

    Now transformers are largely a different matter as their construction can vary wildly. I've designed many different types of transformer (mainly for R.F. frequencies rather than audio) but it is crucial to get a good design for either type. Of course the circuit will also affect the outcome but perhaps to a lesser extent due to the compromises made in transformer design. Perhaps some photo's of the transformers would also help so the type of construction can be seen.

    I look forward to hearing your results.

    P.S. I was so tempted to vote "Go away Donny!" :<)
  9. DonnyThompson

    DonnyThompson Distinguished Member

    I've done as Marco suggested, and recorded several different takes, using various transformer/op amp combinations, with an SM57. It's probably smarter to do it this way, as the 57 is much more common in home studios, and I realize that not everyone has an AKG 414EB laying around.

    MrEase - the transformers included are: a Sowter 9820, a Lundahl 1538, a Jensen J-110-C, and a stock ADK.
    The Op Amps are: a John Hardy 990C, an ADK Vintage, a Cinemag, and a Seventh Circle Audio SC25.

    I can supply the info as to which sample uses what combination, but I don't have access to any schematics for these. I've been told that companies like API are pretty guarded about letting that data out to the public, although I do know that there are a lot of API 2520 "clone"s on the market. I believe the John Hardy is one of these. Whether or not it sounds exactly like an API is, I suppose, dependent on how well you know the API, along with an individual's perception of the sound, and, in what context it's being used - the mic, the vocalist, the environment, the style, etc. - all of which seems to play more of a bigger part than anything else, when determining whether someone likes it - or not.

    I wouldn't be the least bit surprised to learn that many of these designers keep their technical info close to them. From what I've read, it's almost like making fine wine, and each developer has their own kind of "vibe" when it comes to designing and building these components, and it's that "character", that fingerprint, that gives them their reputations, so I would totally understand why someone like yourself would prefer that their designs and schematics not end up all over internet audio sites for everyone in the world to download. ;)

    I didn't buy these trannies or op amps - for that matter, I didn't buy the preamp, either - a friend of mine is lending me this ADK AP-1 pre while his house (and studio) are being remodeled, and these are the various models of transformers and op amps that he sent with the pre.

    He thought I'd get some use out of it - he knows I've been looking recently at purchasing one high end mic pre (budget $800-$1000), and I will admit that I am intrigued by the "pop and swap" design on this preamp, which allows the user to swap out any tranny or Op amp without having to solder, or, even having to use any tools, either. You simply line up the leads to the socket, and pop them in. They come out just as easily.

    One thing I've noticed - besides the obvious (and sometimes not so obvious) differences between the Trans/Op Amp combinations, is that this pre is whisper quiet. I've had the gain up to the max on this thing, and it's dead silent.
    The guys who built this pre obviously put some time and care into it.

    I'll post some samples later today, and probably through out the weekend, as my time allows.


    pcrecord likes this.
  10. dvdhawk

    dvdhawk Well-Known Member

    I would echo Mr. Ease's sentiments about methodology. If it is done with a reasonably scientific approach (no more than one variable at a time, if possible), I would be VERY interested in hearing the results.

    Measure and document everything you can, and maybe don't tell us which combination is which - letting the listener form a impression of the sound without bias. Then at a later date reveal which clip used which combination.
  11. DonnyThompson

    DonnyThompson Distinguished Member

    well, here's how I did it:

    I sang the same 8 bar, single voiced verse of a song that I wrote. This takes out the bias of any familiarity of a song that you've already heard.
    I sang it into an SM57, on a stand, with the mic position never moving.
    I did my best to remain the same distance from the mic, on axis, every take.
    No gain changes were made on the pre at all. The gain control remained in the exact same position.
    There has been no EQ added at all, either on the way into the DAW or afterwards,
    The same goes for gain reduction.
    The only variable was the combination of transformers and op amps in the pre.
    I changed only one component on each take - I never changed both the transformer and the op amp at the same time.

    Remember guys, I did this for my own benefit first.
    I wanted to have a reference of what the pre sounded like - vocally - with different combinations of transformers and op amps, so I could determine what might work best for something that I was working on.

    This was as "controlled" as I could get in the room that I am in. I'm not in a lab or an anechoic chamber, so the results of this might not meet your own criteria for a controlled environment.

    The thing that I'm not sure of, is if I have the room left on my SC account to make all of these .wav files. I might have to limit this to MP3's.

    I'll up load to SC and start posting within an hour or so.
  12. DonnyThompson

    DonnyThompson Distinguished Member

    Here's the first crop of samples.


    Preamp: ADK AP-1
    Input Gain Setting: 50%
    Mic: Shure SM57
    Distance to Mic: 3-5"
    No added EQ or GR

    In each sample, the transformer remains the same.
    The only variable in the following samples is the Op Amp.

  13. DonnyThompson

    DonnyThompson Distinguished Member

    Upon listening to these, I can tell you that these don't sound nearly as good as the original .wav files do. The above files are MP3 360kbp. The quality is not the same.
    I don't know what to do about this... as I don't believe I have enough space on my SC account to use waves.
  14. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    That's a recurring dillema these days. I wonder if we could find a better place to share our files.
    I always could put them on google drive to be downloaded but that meens no realtime player. :unsure:
  15. paulears

    paulears Well-Known Member

    What would be good would be to use a common recorded source - maybe something pure like a sine wave, and then maybe a square wave. It would be interesting to see if the different preamps introduce something other than gain - distortion and harmonics would be fairly easy to spot. It would also be possible to look at the noise levels. I'm very interested in the differences between them, but (as I guess I'm a bit of a sceptic) I'd like to see real evidence rather than subjective stuff. We all hear differences, we've done this before, but we always seem to disagree on what exactly is 'better'.

    I've had an ear infection for a while now, and while I've had it, all my studio work has been off - I'm having to do most of the mixing again. While I had it, my impression was I lost the top end, which I compensated for, but now I'm discovering the mixes and the eq are just wrong. I expected that the mixes would just be too bright, which I could compensate for. However, the whole sound is just wrong. So maybe, what the preamps do is not just frequency response and they do other things. Any kind of result that is objective would be very useful. Just not quite sure how to do it. Donny's done a great job so far - maybe I can collect the same sound with all my preamps - please note, no truly posh ones, because I'm a non-believer, but I do have all sorts.

    Any suggestions for what the test tones could be?
  16. DonnyThompson

    DonnyThompson Distinguished Member

    Well, I agree with you that it would probably be more accurate, scientific. It would be easier to measure distortion. and if I was building one, I'm sure it would be necessary to use those types of stimulus to determine the things that matter in the specifications.

    But - as artistic users of the gear, we don't record or mix square and sine waves: we mix music - voices, instruments, those things that our ears find musical and pleasing.

    Personally, I'm able to relate a lot more to how a pre sounds using a vocal or acoustic guitar, than I am a sine wave.

    Yes, one is certainly more scientific than the other - but far less artistic and pleasing to the ear. I want to be able to hear how things like breath, and "S's" sound on a certain pre, certainly more than how a square wave does, because those are the nuances I work with and listen for in my everyday mixing.

    Just my opinion. ;)
  17. DonnyThompson

    DonnyThompson Distinguished Member


    Okay... so I'm in the process of uploading mono .wav files. Perhaps these will make a difference.
  18. DonnyThompson

    DonnyThompson Distinguished Member

  19. paulears

    paulears Well-Known Member

    Good opinion, just my perhaps unique viewpoint. I just wonder if the reason I just can't get into this pre-amp thing is that maybe what I get from eq and processing could be the same thing - a difference in tone/timbre/overall sound? If I bought a preamp and discovered I liked what it did, then I'd want to know what it was actually doing - when we went digital, people didn't like the sound, so started to develop plugins and stand alone devices to simulate the old sound.

    All the little tricks people do, like replacing capacitors in condenser preamps in the mic, result in 'something' changing, and I'm curious enough to want to know what it is?

    The mics I sell have samples of how they sound on common instruments - nylon and steel guitars, saxes, clarinet etc - and just recently I had to re-record them because I lost the little spreadsheet that told me that 123.wav was a specific mic. I tried to work it out by listening, but couldn't. They were different, but in the end, I gave up.

    I'm getting the impression that if I do the tone test, I might actually reveal errors in the preamps I use on a daily basis. That would kind of contradict my feeling on preamps.
  20. paulears

    paulears Well-Known Member

    On the samples - my preference is 4,3,1,2 I like 4 best because it is warmer and gentler. 2, the one I prefer the least, would still be perfectly acceptable if I didn't have access to the others.

    I've also got a problem. The difference is far greater than I'd imagined, and this suggests my own selection of less 'posh' ones could be equally coloured. I've never done an A/B, just recordings on different sessions and sources. I'm going to have to listen to those again on some different kit and see if the order remains the same.

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