pfsmith0 Posted March 17, 2015 Share Posted March 17, 2015 Some of you may remember the EQ/FX frequency response and IO Gains I measured a while ago. With all this talk on Cab DEP Parameters I decided to take my HD500 back into the lab and make measurements to see what these are doing. The question I have is what companion amp should I use (I cannot choose a cab w/o choosing the amp first)? It should be clean so it doesn't perturb the signal very much. I'm thinking the Blackface or Soldano Clean. Thoughts anyone? Also, which mic & cab? I'd like these wideband & flat if possible. I only want to vary the DEP parameters and hold the amp/cab/mic fixed. Otherwise, the report will be too busy and it will be hard to tell what's going in. What I'll do is measure the amp frequency response w/o cab, then add the cab (w/ some mic), measure that, then vary the Cab DEP parameters and measure those. So, which amp? Which mic? Which cab? Thanks 1 Quote Link to comment Share on other sites More sharing options...
MartinDorr Posted March 17, 2015 Share Posted March 17, 2015 I think you want to spend some time on good baseline measurement w/o an amp, cab, or mic. Next add the amp w/o cab/mic/ER ... add one modelling piece at a time so you can see their impact. I used BF double in the past for similar thing w/o successs (see below). Tried this route before with iPhone/iPad SignalScan SW and a Behringer AD/DA interface and found that I could not get a flat signal level through the HD in a pass-through setup (Guitar or Aux in) using sweep or noise input. I always got oscilations on the output no matter what pad/line, Bypass or Master volume setting I tried. SignaScan was set to generate a 0dBFS output signal, the Behringer produced a -20dBV analog signal. I ran 1 of the Behringer analog stereo out channels as reference back into the Behringer analog input to SignalScan and the other through the HD before coming back to the Behringer. Wrote my problems off as SignalScan probably being not up to the task, but looking forward to what you find. I also tried going out HD affect send or coming in with effect return and even going out to a DT via L6 Link (digital) and then tapping into the DT effect send with no preamp selected in the DT. All scenarios showed the same kind of oscilations. Sorry, no reason to recommend a specific amp, cab, or mic. I never made it to that point to have reasons for or against specific choices. Quote Link to comment Share on other sites More sharing options...
pfsmith0 Posted March 17, 2015 Author Share Posted March 17, 2015 Thanks Martin. I use the Guitar/Aux input and SPDIF output and was able to get a very flat/wideband response. My audio analyzer is the APx525 by Audio Precision, a very nice, very expensive analyzer that has never let me down. Thanks Hurghanico. Sounds like a good option. I'll start there unless I hear from others why this would be a bad option. Quote Link to comment Share on other sites More sharing options...
barneybrown Posted March 17, 2015 Share Posted March 17, 2015 Hi, I'd advise against using the Flip Top Bass amp for this experiment as I believe the Microphones available for this amp are different to all the other amps in the POD. Barney Quote Link to comment Share on other sites More sharing options...
spaceatl Posted March 17, 2015 Share Posted March 17, 2015 regardless of what amp you choose, I would say shoot the amp with the NO CAB Option first....This might help find out the flatest amp model....you could opt for the flattest mic you find at this point...probably need to settle on a mic so this doesn't take you a million years as there are so many permutations... Although I have never measured it, The Hiwatt seems the least colorful amp to my ears.... PRE models would be a lot cleaner, but you would likely then figure out that the cab models are a little bit different for the PRE models even though they have the same name... Quote Link to comment Share on other sites More sharing options...
MartinDorr Posted March 18, 2015 Share Posted March 18, 2015 PRE models would be a lot cleaner, but you would likely then figure out that the cab models are a little bit different for the PRE models even though they have the same name... I think that by itself would be surprising to me because using pres does not imply any power amp or Cab the user may have. I could imagine though that using Line 6 Link to connect to a DT (which often implies that pres are used instead of full amp models) may change the Cab model because the HD may 'know' what the expected DT speaker is via Line 6 Link connection. Clearly wildly speculative, but I still think more likely than changing Cab models based on pre versus full model selection. Quote Link to comment Share on other sites More sharing options...
amsdenj Posted March 18, 2015 Share Posted March 18, 2015 The Flip-Top Pre amp is the only amp (that I could find) that has Hi-Fi boost/cut flat-in-the-middle tone controls. However it also has a pretty significant low-pass filter or high cut, even without any speaker cabinet. You could use that amp with any cabinet to study the cabinet parameters in order to at least limit the impact of the amplifier on the study. The 4038 Rbn mic is probably the flattest microphone. But I agree with hurghanico, its the relative differences the cabinet parameters make that is of interest. The particular amp and tone setup should be normalized away by using the same amp combination and only changing just the cabinet parameters. The difference between the two explains the impact of the parameters. And thanks for doing this study. I think it will be very valuable and a great contribution to the community. Not sure why Line6 wouldn't provide this information directly based on the design of the parameters, rather than the overly simplified descriptions in the manual. Of course we should use our ears to assess the impact of these parameters, and keeping the descriptions high level is fine for casual users. But deep parameters are probably not that interesting to casual users. Quote Link to comment Share on other sites More sharing options...
amsdenj Posted March 18, 2015 Share Posted March 18, 2015 "ascendant melodic minor scale located on the semitone just after the root of a functional dominant seventh chord" Ok, now I've got to go try that. Regarding the "deep doc", why couldn't Line6 contribute that to a sticky in an Advanced Users forum? Quote Link to comment Share on other sites More sharing options...
pfsmith0 Posted March 22, 2015 Author Share Posted March 22, 2015 Well, I went and made the measurements but the system crashed while trying to export to Excel (aaargh!!), so I'll have to go back and do it again next weekend. However, I did notice that the RES LEVEL knob controls a narrow high-Q peak in the 100-200 Hz region, depending on which cab's being used. When set to 0 the peak is barely noticeable. When set to 0 the THUMP and DECAY knobs have very little effect. As RES LEVEL is increased, THUMP makes it even larger. Once those frequencies are excited, the DECAY control determines how long it takes for those frequencies to subside. If you don't want that peak, turn all 3 levels down to 0. LOW CUT is just a variable high pass filter. Adjust that to remove any muddiness you don't want. I'll take the unit back in and publish graphs once I get a successful export. 2 Quote Link to comment Share on other sites More sharing options...
duncann Posted March 22, 2015 Share Posted March 22, 2015 Well, that's really useful information. Finally some real data about what these parameters actually do. I, and I'm sure lots of others, will be looking forward to the detailed data. Thanks for doing this. Quote Link to comment Share on other sites More sharing options...
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