ColonelForbin Posted May 21, 2014 Share Posted May 21, 2014 Does anyone know if the 1/4" outputs from the JTV have a buffer? I am setting up a semi-complex use of the JTV+HD500+DT25, using both outputs from the JTV, and running the 1/4" into an analog pedalboard before it hits the HD500. I haven't tested this yet, but I was reading up and checking various YouTube vids about placing a dedicated buffer pedal at the front of the signal chain, to compensate for the tonal loss of using several true-bypass pedals. Some very interesting info about this kind of stuff, and a few of the audio tests reveal a very clearly pronounced treble and tone loss. I guess it comes down to basic math, the 15' cable from guitar to pedal, all the patch cables, and the cable run from end of pedal chain to the amp can easily be 50' or more. The side note I did see, is that using a buffer pedal up front isn't needed if the guitar output is buffered, as is the case with guitars that use batteries. I wasn't sure if the JTV was such a beast, or if the battery is used for the variax portion only - it doesn't strike me as an "Active" guitar per se, but this is all relatively new knowledge for me, so I wasn't sure how to look at it! Here is a buffer pedal that I stumbled across, and got me researching all this stuff: JHS Little Black Buffer http://youtu.be/sexnpn-3Dp0 Quote Link to comment Share on other sites More sharing options...
ColonelForbin Posted May 21, 2014 Author Share Posted May 21, 2014 Quote Link to comment Share on other sites More sharing options...
Charlie_Watt Posted May 21, 2014 Share Posted May 21, 2014 I am sure that the output is low impedance - buffered since it's coming from a DAC. Quote Link to comment Share on other sites More sharing options...
snhirsch Posted May 22, 2014 Share Posted May 22, 2014 When the modeling circuitry is off, you are dealing with a conventional unbuffered instrument. 1 Quote Link to comment Share on other sites More sharing options...
Charlie_Watt Posted May 22, 2014 Share Posted May 22, 2014 Very true. Mags are completely passive through the 1/4 inch jack. Not so through the VDI though. Quote Link to comment Share on other sites More sharing options...
jandrio Posted May 22, 2014 Share Posted May 22, 2014 Very true. Mags are completely passive through the 1/4 inch jack. Not so through the VDI though. What r they thru the VDI ? Quote Link to comment Share on other sites More sharing options...
TheRealZap Posted May 22, 2014 Share Posted May 22, 2014 speculating... but i think they are referencing a possible A/D/A conversion that would take place to send the mags out the digital output. What r they thru the VDI ? 1 Quote Link to comment Share on other sites More sharing options...
ColonelForbin Posted May 22, 2014 Author Share Posted May 22, 2014 Very interesting! I guess I will test this out - so it's possible the 1/4" outs vary based on whether the modeling is activated or not. No sense spending $$ on things like a buffer if I don't need it! I suppose it's never a bad thing to have around, I also use a regular old strat with the rig. In this particular example I was looking at sending the 1/4" through the buffer and into the pedalboard while the VDI is sent to the HD500 - which is then joined by the 1/4" from the pedalboard going to the guitar in on the HD500.. I might end up with a tonal mess when I actually get to plug everything in this weekend. Will let ya know what happens! Quote Link to comment Share on other sites More sharing options...
jandrio Posted May 22, 2014 Share Posted May 22, 2014 on a Workbench HD-JTV preset, set "Magnetics Blend" = "Mags" (100%). now, the 1/4" out (VDI also) must (?) vary as per "Preset Volume" setting (range=-20db, +6db)... Quote Link to comment Share on other sites More sharing options...
Charlie_Watt Posted May 22, 2014 Share Posted May 22, 2014 VDI is serial digital as far as I know. I have not scoped it though. Quote Link to comment Share on other sites More sharing options...
sulkbooth Posted May 23, 2014 Share Posted May 23, 2014 Could it be tested with recording both the mags and the variax sound into a DAW, and see the difference in ms? Quote Link to comment Share on other sites More sharing options...
clay-man Posted May 23, 2014 Share Posted May 23, 2014 I am sure that the output is low impedance - buffered since it's coming from a DAC. Should I switch my interface to Line in impedance than? If it has a different impedance than a normal guitar, wouldn't that be harmful to the thing you're plugging it into or not? Quote Link to comment Share on other sites More sharing options...
Charlie_Watt Posted May 23, 2014 Share Posted May 23, 2014 No need to switch your interface. That is more a level thing and the Variax outputs are instrument levels which are lower than line levels. You do not need to match impedance here. What you want is the input impedance of your devices to be higher than the output impedance of your guitar. Passive pickups are higher impedance than a buffered output which makes cable length affect your tone. This is not intended but it's a result of the fact that the pickups have lots of turns of very fine wire. The combination of the pickup and the guitar cable has a LRC resonance so it does modify your tone. The cable is capacitive and the pickups are inductive / resistive. This is a fairly subtle effect unless you go with a very long guitar cable though. 1 Quote Link to comment Share on other sites More sharing options...
mdmayfield Posted May 23, 2014 Share Posted May 23, 2014 A side note, something else to consider - if I'm not mistaken, there will be at least 3-5 ms or so timing difference between the two outputs, which might change based on whether modeling is activated or not. If you're going to mix the signals, that might be something to watch out for, since assuming that's the case, it'll cause some odd comb filtering on the signal. Quote Link to comment Share on other sites More sharing options...
ColonelForbin Posted May 23, 2014 Author Share Posted May 23, 2014 A side note, something else to consider - if I'm not mistaken, there will be at least 3-5 ms or so timing difference between the two outputs, which might change based on whether modeling is activated or not. If you're going to mix the signals, that might be something to watch out for, since assuming that's the case, it'll cause some odd comb filtering on the signal. Yeah, I had that thought too; wasn't sure this idea of using both the 1/4" and VDI outputs would work as a result of that possible signal delay. My original idea was use the VDI into the HD500 then split the signal into two amp models, and place the FX loop into the signal path which I want to run through the analog pedals. I think it may warrant some kind of recording test to the computer, see how everything looks! I guess there are tricks I could use to delay the VDI signal, but at a certain point it becomes just an exercise in nonsense! lol, I am good at that :) Thankfully, it's looking like I will *finally* have some time over this extended weekend to mess about with these various ideas. Another version of this idea I had was use the VDI, then split the variax models and the mags into the two signal paths, and run the mags through the analog pedals. Quote Link to comment Share on other sites More sharing options...
Charlie_Watt Posted May 23, 2014 Share Posted May 23, 2014 3-5 msec delay difference isn't going to be very noticeable. Think of it as playing through two amps that are 3 to 5 feet apart. 1 Quote Link to comment Share on other sites More sharing options...
clay-man Posted May 23, 2014 Share Posted May 23, 2014 3-5 msec delay difference isn't going to be very noticeable. Think of it as playing through two amps that are 3 to 5 feet apart. It will if you're adding other latencies to it from your audio interface buffer. I have an 11ms buffer on my DAW (can go down to 6, but I leave it at 11 for CPU headroom or else it may start buffering with a lot of intense plugins). 11+5 is 16, which is pushing it. Alt tuning adds more latency. It's noticeable when I pay attention, but doesn't hinder playability. Would introduce rhythm problems if any higher. Quote Link to comment Share on other sites More sharing options...
mdmayfield Posted May 23, 2014 Share Posted May 23, 2014 3-5 msec delay difference isn't going to be very noticeable. Think of it as playing through two amps that are 3 to 5 feet apart. Charlie_Watt, yes, you're absolutely right as far as delaying one copy of a signal, vs. not delaying it. The complication comes in when you mix *two* signals, one delayed and the other not. When you mix two identical signals with one delayed a tiny bit, you get a "stuck flanger" type effect (comb filtering) - in fact, this is how a real analog flanger works: it mixes two copies of a signal, one delayed, and gradually varies the timing of the delay. If you have a DAW setup, it's a really interesting experiment to two copies of a track, and nudging one of them ahead or behind just a handful of samples, to hear the comb filtering effect. (Sorry for the continued tangent from the original question!) Matt Quote Link to comment Share on other sites More sharing options...
clay-man Posted May 24, 2014 Share Posted May 24, 2014 Charlie_Watt, yes, you're absolutely right as far as delaying one copy of a signal, vs. not delaying it. The complication comes in when you mix *two* signals, one delayed and the other not. When you mix two identical signals with one delayed a tiny bit, you get a "stuck flanger" type effect (comb filtering) - in fact, this is how a real analog flanger works: it mixes two copies of a signal, one delayed, and gradually varies the timing of the delay. If you have a DAW setup, it's a really interesting experiment to two copies of a track, and nudging one of them ahead or behind just a handful of samples, to hear the comb filtering effect. (Sorry for the continued tangent from the original question!) Matt It's not really that bad. I'll give you an example. I use delays to fake double tracking, and even quad tracking in live/jamming situations. Sounds fine. No comb effect. Quote Link to comment Share on other sites More sharing options...
Charlie_Watt Posted May 24, 2014 Share Posted May 24, 2014 There will be a comb effect if the two signals are identical except for the delay. Some frequencies will cancel and some will be amplified due to the phase shift. Time delay is a nonlinear phase shift. Quote Link to comment Share on other sites More sharing options...
mdmayfield Posted May 24, 2014 Share Posted May 24, 2014 It's not really that bad. I'll give you an example. I use delays to fake double tracking, and even quad tracking in live/jamming situations. Sounds fine. No comb effect. Sure, I'd agree with that too. The 20+ ms delays used for fake double (or more) tracking don't usually cause those kind of issues. The issue I'm referring to only happens with really short delays, like under 5 ms, like what you'd get when mixing two otherwise identical signals, but where one passed through an extra D/A or A/D conversion. Video example: Thanks, Matt 1 Quote Link to comment Share on other sites More sharing options...
ColonelForbin Posted May 24, 2014 Author Share Posted May 24, 2014 I did a little testing of this last night, but nothing conclusive, other than, using a buffer pedal up front definitely made a difference when using the mags on the JTV, but not sure what it did to the variax models. With the 1/4" through the buffer vs without, there was a noticeable decrease in tonal quality without it; using multiple analog pedals, at least 6 or 7 actual FX, plus the buffer and a noise gate. I may try a variation where I split the variax models and the mags, see what happens when I feel the front of the analog signal chain with the FX send. I did notice some odd volume issues when I had a chorus pedal and phaser in the HD500 FX loop; I may have to go back to my original idea of running the chorus in the DT25 FX loop - not sure until I test all this stuff at volume (was just running the two 1/4" outs from the HD500 into my soundcard and monitoring with some M-audio speakers in studio/direct.) Regarding the comb filtering conversation; in terms of the two signals being identical, what happens when the two signals are being processed differently? The two source "dry" feeds are identical, but they are being processed in two different signal paths; wasn't sure if that would still cause the comb effects in a detrimental way? My original idea was to just run the VDi to the HD, then send the 1/4" analog signal out through the fx send. I will try to do some recording tests with some staccato playing to see where the .wav peaks align in the three variations of splitting the signal: 1.) VDI and 1/4" outs from the JTV 2.) VDI to HD500, input1=variax, input2=mags, send input 2 out on amp path B through HD fx loop to analog pedals. 3.) VDI to HD500, use same input for amp A and B, however, send path B out via FX loop to analog pedals. Quote Link to comment Share on other sites More sharing options...
clay-man Posted May 24, 2014 Share Posted May 24, 2014 Sure, I'd agree with that too. The 20+ ms delays used for fake double (or more) tracking don't usually cause those kind of issues. The issue I'm referring to only happens with really short delays, like under 5 ms, like what you'd get when mixing two otherwise identical signals, but where one passed through an extra D/A or A/D conversion. Video example: Thanks, Matt True, though I have to argue: Do you HEAR a comb effect in blend mode? One of the most common things people do when doing a blend effect with the dry and wet signal when the wet signal has latency, is add latency to the dry signal as well for compensation so it's in sync, Are you sure the guitar doesn't do this? Quote Link to comment Share on other sites More sharing options...
Charlie_Watt Posted May 24, 2014 Share Posted May 24, 2014 I suspect that there is little difference I latency in the blend mode since both the mags and model are being processed digitally. Quote Link to comment Share on other sites More sharing options...
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