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TrueRTA Fun: GK and VTDI Content

Discussion in 'Amps and Cabs [BG]' started by Kro, Feb 23, 2018.


  1. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    I've been thinking it'd be fun to actually purchase one of the higher resolution versions of TrueRTA for some time now to play around with, and given that I took a "mental health" day off of work today, my curiosity finally got the better of me.

    I figured it might be fun to share some frequency response screen grabs that I took with the gear I have on hand once I got everything configured, calibrated, and up and running. :)

    First up, is my beloved 1001RB with 1001RB-ii preamp. There have been a number of threads I've seen on here with users claiming what flat is for these guys, largely, from what I can tell, based on brother/sister amps in the GK family. @fdeck did a great assessment of the BL600 which is supposed to be similar to a 400RB-iii (I think he also later did some testing on an MB unit), and Bass Gear mag did a write-up of the MB800 - that is also supposed to use a similar pre, but none of those flat settings were anywhere near close to what I was getting from my own personal testing.

    So just for fun, because I had the tool and the gear at hand, I decided to do my own experimentation. Just for reference, here's what the 1001RB-ii preamp looks like with knobs at noon:

    GK Only post.png

    Here's what I consider the best way to get flat - between messing with various levels of contour and even presence, there were other options that all came within 1dB of flat (none that I'd seen previously), but this one had the best high and low extension of those I tested:

    flat post.png

    And drumroll please, the settings that pertain to the curve above (sorry for the crappy cell phone shot):

    (keep in mind I'm taking a feed from the send, so boost isn't involved)
    IMG_20180223_152423210~2.jpg

    Really enjoying and having a lot of fun getting to know the TrueRTA software - I think that it's going to prove to be a very useful tool in the future!
     
    Last edited: Feb 23, 2018
  2. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    Next up, I wanted to see what my VTDI that I feed into the front of my 1001RB was doing. Sorry for the decreased levels here: since it goes into the front of my GK the VTDI is usually set at instrument level or thereabouts (not nearly as close to unity as I thought though, it turns out)!

    Anyways, without further ado, this is what the curve for my VTDI looks like with my personal settings:

    Sansamp Only2.png

    My settings, that I have set up specifically to play nicely into the front end of my GK - bite and speaker sim in:

    small.jpg

    And just for fun, here's how things look with my VT going into the front of my GK with similar settings to those in my first post, but with just a hair of presence (9:00) dialed in:

    Sansamp+GK post.png

    Alright, that's all I have to share for now - I'll undoubtedly be messing around with things more tonight. Sadly, I don't have much additional gear to try out with it (aside from my large stable of GK amps, I'm not much of a gear hound). But, if anybody has any requests for things that I can test out with what I do have, I'd be happy to oblige!
     
    Last edited: Feb 23, 2018
    LiveToWin, BrentSimons and Al Kraft like this.
  3. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Cool, looking forward to seeing what else you test. BTW, try running your input gain a little less hot, it looks like things are ringing a bit in most of those screen shots.
     
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  4. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    5c4.jpg

    OK, got it. Sorry, I'm a totally newb when it comes to this ;) - I noticed that, but wasn't sure why it was happening. Having it be due to potentially too high of an input gain makes sense though, I'll try that. Thanks!

    Awesome, already some additional things for me to try out tonight! :D
     
    Last edited: Feb 23, 2018
  5. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    There are some other settings that could be relevant too, like the number of averages or the response ballistics. But usually I find that gain structure is the primary factor. You can just change your scaling to get the best possible resolution, once you resolve the ringing.

    I've been using True RTA for many years, feel free to PM me if you have questions or just want to trade some test files. I'm not really comfy with posting too many on TB these days due to the CUP thing, even though no one has ever called me out for it.
     
  6. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    LiveToWin, nolezmaj, jchrisk1 and 2 others like this.
  7. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    That's also very similar to an older TB post that showed optimally flat settings for the MB500 based on instrumented measurements. I'm just guessing that the inherent GK voicing and tone stack settings have a fair amount of consistency, at least across a particular line (e.g. MB series).
     
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  8. 10 2 1 10 all the way round the world.
     
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  9. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    It is relatively close, but just one thing to note - and this could just even be due to typical pot variability, but I also needed to utilize the contour in my version. Those same EQ settings that I posted but with contour off had a noticeable bump around 500Hz.

    A slight contour boost to pull down the hump that I was getting between the other mid EQ points, and a small correction with lows and treble, and it fell pretty nicely into place. :thumbsup:
     
  10. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    So last night things got a little interesting, not so much on the GK side that we're all more familiar with, but on the preamp side with my VTDI by itself. There are already a number of excellent threads analyzing earlier versions of the VT Bass pedal, and some others that look at later versions as far as what the independent bite and speaker sim buttons do, though there doesn't appear to have been too much exploration as to what exactly blend is doing.

    With that being said, I did a bit of knob turning mostly based around my current blend setting of 50%, with this being my signal prior to bite or speaker sim being engaged. Drive is also fully counter-clockwise.

    Screenshot 2018-02-24 05.59.33.png

    I wanted to sweep blend to see if there might be any odd issues that might arise from it - loss of low end, odd filtering, but pretty much it stayed the same and just moved consistently up or down based on level. Highs were still slightly accentuated by the SansAmp side compared to the dry portion even with no bite or speaker sim, but that's not really unexpected. Just for example, this is the same setting as above, but with blend fully clockwise - relatively consistent.

    Screenshot 2018-02-24 06.07.59.png

    Alright, now putting blend back to 50% where I normally run it, lets take a look at speaker sim and bite, drive still off. This is where things appear to get interesting, at least to me.

    Bite on, speaker sim off first. Not surprising.
    Screenshot 2018-02-24 06.12.09.png

    Bite off, speaker sim on. Hmm alright... that's an interesting divot there at around 4k...
    Screenshot 2018-02-24 06.13.53.png

    Bite on, sim on, and keep in mind this is still with drive fully ccw. Good lord.
    Screenshot 2018-02-24 06.16.20.png
     
  11. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    So based on that last capture, I figured I'd look at a blend sweep just for reference to see exactly how the signal is affected with various levels of blend.

    Blend fully CCW:
    Screenshot 2018-02-24 06.26.56.png

    Blend 9:00
    Screenshot 2018-02-24 06.27.59.png

    Blend 12:00 (as above)
    Screenshot 2018-02-24 06.28.59.png

    Blend 3:00 (Sansamp starts to beat the clean signal into submission):
    Screenshot 2018-02-24 06.30.16.png

    And lastly, blend fully clockwise:
    Screenshot 2018-02-24 06.31.37.png

    Some of you may have noticed that in my very first post of this thread, I showed what my usual SansAmp only signal looks like, that used settings extremely similar to those above with blend at 50%, but that there was no valley. The only difference in my settings was drive, which I normally keep around 11:00.

    Just for reference, this is what I'm referring to. Same as above, blend 50% but with drive ~11:00:
    Screenshot 2018-02-24 12.29.48.png

    I haven't actually done a drive sweep at this point (kids just woke up, need to take a break!), but my mind is already super curious what's going on. Is the drive adding additional signal strength to the SansAmp side so that the blend really isn't 50/50 at that point? Or could it be something to do with the harmonics that the drive imparts... very curious!
     
    Last edited: Feb 24, 2018
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  12. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    Plus, the MB800 uses FETs instead of Op-Amps (which I believe are used the RB's), so that will also introduce some variability. All-in-all, though, they have very similar approaches to achieving "flat."
     
    Kro likes this.
  13. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    So I'm about to start testing these hypotheses. One way that I can think of to start testing this is to determine which blend setting has the largest valley - as I'd assume that the largest point of cancellation will be when the signals are both closest in equal strength. For drive at 0 (fully ccw), I just verified that it is indeed with blend at noon.

    For drive at 9:00... lets see... yup the valley is most prominent with a blend setting of around 10:00. This seems, at least to me, to indicate that the blend doesn't in any way compensate for SansAmp side level. Drive boosts the SansAmp side signal, and needs to be offset by a lower (higher? ... more ccw) blend level to compensate. Fascinating.

    That didn't take as long as I had suspected, any fault with that logic?
     
  14. seamonkey

    seamonkey

    Aug 6, 2004
    It is an eye opener to see what is really going on.
    Do you have a loopback curve with nothing inserted, just interface out to in
    It can be good to have this baseline in case it is not flat.

    TruRTA can also measure the distortion. It would be interesting to see those numbers.
    With an EQ the same curves can be drawn, but distortion is going to change the sound differently than just eq.
     
  15. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    Nothing else inserted, and I have a high enough version of True RTA that it lets me calibrate the system as you noted. Can confirm that it's dead flat with nothing else inserted.

    Here's my system in a closed loop with nothing else in between but the cable:
    Screenshot 2018-02-24 13.00.47.png

    Interestingly, this is the signal through the VTDI in bypass:
    Screenshot 2018-02-24 13.01.43.png

    Still learning the ropes as far as measuring the distortion effectively. Will look into that in the future, and I completely agree.
     
    Last edited: Feb 24, 2018
  16. seamonkey

    seamonkey

    Aug 6, 2004
    It is just amazing what a good interface and good software package can do these days.
    And for a fairly low price!
     
  17. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    Seriously... I was just thinking earlier about how, with the things that I've already been able to explore, I've already got my money's worth out of the software. Incredible.

    Also, integrated audio that now comes with the better main boards is pretty fantastic in this day and age. Long gone are the days of needing dedicated audio cards IMO. I'll still use an outboard interface for recording to have a bit more flexibility, but for stuff like this I don't even bother.
     
    Passinwind likes this.
  18. hsech

    hsech Work hard. My Social Security needs a raise.

    Jun 27, 2012
    Central Iowa
    With my old hearing, these tests are meaningless.

    nosedive-e1413383002202-620x266.jpg
     
  19. Kro

    Kro Supporting Member

    May 7, 2003
    New Jersey
    So, from all of these tests, what adjustments did I make to my personal, everyday settings? Well... almost none. Mostly, these tests just allowed my eyes to confirm much of what my ears already knew, though with the added insights that I found out in posts 10, 11, and 13 with issues that might come about while using the blend. I had suspected these even before downloading TrueRTA - wanting to see if they were there was actually a motivating factor for me to first want to check it out actually.

    After this round of testing, using both eyes and ears, I did ever so slightly tweak down my VTDI highs and mids to now look like the shot below. I also nudged up my level a bit to be closer to actual unity.

    IMG_20180224_133106294~2.jpg

    Here's a new shot of the VTDI through the GK preamp (contour off, presence 9:00, and EQ nooned) but with the pad on to bring down the level - looks pretty much the same. A lot of the noise in the signal actually appears, I think, to be coming from the VTDI drive, as it isn't a clean setting with my instrument. I haven't played around with any other settings that @Passinwind noted earlier, but just from significantly bringing down the level, not much has changed.

    Screenshot 2018-02-24 13.48.13.png
     
    Last edited: Feb 24, 2018
    Passinwind likes this.
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Just beware of measurement artifacts that often plague all measurement systems. There are some VERY significant ones that plague those such as TrueRTA and similar packages, things like low/high frequency ground loops, unintentional clipping or limiting/bounding of inputs, extraneous high frequency noises, and something that can be really costly... trying to measure a high current bridged output... a good way to destroy a laptop or tablet under some conditions.
     
    Kro likes this.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Mar 8, 2021

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