Discussion in 'Digital & Modeling Gear' started by moonblack, Jun 11, 2015.
Bias can have a significant effect on clarity if your Master is set high up.
Exactly my point... If you play with the Bias and Bias X, you might add something in there that is not noticeable at low volumes but more at loud volumes. Just thinking out loud. Might be interesting to revisit some patches with different combinations of Bias, Bias X, Hum, Gain and Master Volume.
I did some messing around last night. Ended up turning DEP master, hum, sag, bias, and bias X all to ZERO. It made the amps super quiet but got rid of a lot of the nasty buzz. Also, if you turn the master way up so you hear a lot of the crossover distortion or whatever, then you can hear a big difference with the bias controls. Nothing is getting rid of it completely though. And it's odd, I tried playing with JUST the Vox preamps last night too, going into an IR (IOW, no power amp model); I could hardly get any grit. It seems most of the OD is coming from the power amp, which is why those of us who don't love the power amp distortion are having a rough go with some of these models. Isolating the preamp really helped me to see (hear) what distortion was coming from where.
As germanicus says, increasing Bias will tame the distortion a bit on some (not all) of the models. It won't take it out altogether on any of them, which is weird if if Bias on 10 does in fact represent Class A operation. I still feel like the distortion issue is a little more complex than just class A/B crossover, but I won't pretend to have a better idea.
Otherwise, I agree with Jose's point about Master and Ch. Volume being the most relevant parameters.
The manual actually calls this out explicitly. I noticed this a couple of hours into wondering why Bias etc. controls were so subtle.
"Master Adjusts the amount of power amp distortion. This parameter is highly interactive with all other power amp parameters—the lower the Master is set, the less effect the other controls will have."
Another good reason (the best reason IMO) to vote up the request for separate power amp blocks. I'd like to be able to identify the offending power amps and avoid them, rather than having to avoid the entire pre-amp/power amp package.
Got some pretty decent edge of breakup sounds running the AC15 preamp only into the HiWatt full amp model set squeaky clean, into an IR. I think if they isolate the power amps to allow those alone in a block as we have discussed (Jose provided an Ideascale link a few pages back), then that could really solve a lot of issues.
Also, since I was having a hard time driving the AC15 preamp only (even with humbuckers), I put a Klon with gain at 0, tone at 7.5, and level at 9 to give it a pretty clean boost, maybe a little coloration. Seemed to work pretty well. The only problem is this chain of klon --> ac15 preamp --> full clean HiWatt amp model --> IR takes up a lot of DSP. More than I think it needs to in order to attain the tones.
Yep, this is definitely something wrong with the firmware.
Hopefully Line 6 will address your issue soon.
Aren't there any EE's with sound engineer/guitar amp experience out there who can give us a detailed description of what "cross-over distortion" is and its relationship to Class B, Class A/B, and Class A amplifiers, as well as any other distortion concepts we may be missing (like at the Phase Inverter, etc.)? I'm assuming, while it may be more pronounced in Class B amps, it's also a factor in Class A to some extent. (I'm also kind of assuming if you are out there lurking, you're probably laughing at us fumble around here.... )(I can't even imagine what the Line 6 guys are thinkin', especially given that they've done a lot of A/B testing with the actual amps)(I need to go take that A/B test that they put up.... )
It would also be nice if the amp list not only included which have a Master Volume IRL (thank you @benadrian ), but also what class they are, (and what EXACT model was modeled (year, tubes, etc.)).
It would be nice to set a bar for expectations.
The problem is you'd likely have to be an EE with sound engineer/guitar amp experience to fully appreciate the answer. (I have a BSEE myself, but I haven't designed an analog circuit since I was an undergrad - and that is a long time ago.)
This is actually one of the lighter reads I've found on the subject of Class A amplification. Interesting, but probably tldr/ minutia for many: http://sound.westhost.com/class-a.htm
What Vox preamps without power amps? I thought you could only separate the whole amp (pre and power amps) from the cab. If you mean you turned the Master Volume to zero, my understanding from these threads is that this just changes the volume of the preamp going into the power amp, so you'd be hearing just power amp. I'm confused.
There are preamp blocks, amp blocks (preamp and power amp), amp and cab blocks (preamp, power amp, and cab), and cab blocks. The only thing we don't have is isolated power amp blocks! I totally forgot until yesterday that we could isolate the preamp. You just choose "preamp" from the menu instead of "amp."
I think the preamp blocks are mainly there for people who want to use their own outboard tube power amps into a speaker cab on stage or what-have-you.
Right now, you can have JUST the preamp (this is meant for running the Helix into an external power amp & cab) in a block but not JUST the power amp.
^^^What scook said...
Since we're on the topic of using Helix's preamps with external power amps and cabs, I thought the DT series amps sounded pretty damn good with the HD500X. I bet something like that could be really, really great with Helix.
Thanks for the tip I will gave that a try today
Off topic, but whenever I see a posting from @scolfax, I think for a micro second that David Gilmour has chimed in.
Apparently I missed that! Thanks.
I've tried my DT25 with Helix using Line 6 Link and MIDI. It sounds great but I'm not positive that I'm going Helix preamp into DT25 poweramp and cab or am I actually going Helix preamp into DT25 preamp, poweramp and cab.
Right, because the DT25 preamp is basically the preamps from the HD series, correct? Would be best if you could just bypass that, I'd imagine. Would be interesting to know for sure.
That explains why I didn't notice much difference with the Bias controls. I usually have the Master control set to 5 or lower, depending on the amp. This is one of those RTFM cases, ain't it? LOL