VOX | Discussion Forums Tag: clipping

VOX | Discussion Forums Tag: clipping http://www.voxamps.com/forum/ VOX | Discussion Forums Tag: clipping en Wed, 22 May 2013 19:40:51 +0000 tweakfreak on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36518 Sat, 24 Nov 2012 16:43:15 +0000 tweakfreak 36518@http://www.voxamps.com/forum/ I'd be happy with just a single LED that flashes when the phones output comes near 2.5V, or the digital stuff nears it max range. Shouldn't be too hard. Anyway, I built my own little clipping detector that I can stick in the PHONES output. It is not "live", but it helps keep the user presets under control when I am tweaking. randman on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36508 Fri, 23 Nov 2012 21:45:46 +0000 randman 36508@http://www.voxamps.com/forum/ So Maybe the next generation should have output and input pot/metering as my Voodu Valve so not to overdrive the D/A converter? Damm good stuff tweak! tweakfreak on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36502 Fri, 23 Nov 2012 15:22:41 +0000 tweakfreak 36502@http://www.voxamps.com/forum/ Thanks to Timc and Twang! You're really helping things along. Interesting stuff! Also because there is a fairly easy way to create an FX loop using the PHONES output as inserts by changing some of the wiring. Yeah, so in the AD15VT (and AD30VT) the MASTER is after the D/A converters (not before, like I first thought). And the PHONES output is before the tube section. Also turning up MASTER cannot cause clipping in the PHONES output. From this schematic I'd say the phones output would be more like +/-5.5V, but what I see in my VT40+ is +/-2.5V at the phones output. So the VT+ series must be different in that turning up MASTER causes PHONES output to clip at +/-2.5V. In this schematic (AD15VT), IC2A boosts the 1.75Vpp output of the AK4552VT to about 11.5Vpp, which should never clip, given the +/-15V power supply to the IC2A. There is no way the PHONES output would show clipping unless it occurs in the digital modeling section. BTW, 11.5Vpp is a lot of signal to the PHONE/LINE_OUT, but not atypical for studio equipment. With headphones you'd want to turn back MASTER quite a bit, I expect. Assuming the VT+ is a next step from this schematic and the PHONES output is still at the end of the pre-amp section my original argument probably is not incorrect: you don't want to see a clipped signal at the PHONES output of a VT+ amp. twangdread on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36479 Thu, 22 Nov 2012 03:37:28 +0000 twangdread 36479@http://www.voxamps.com/forum/ I took a look at the service manual linked above. The schematics in the AD15_30VT service manual show the phones jack receives its signal from the line-out of the preamp/modeling+FX DSP main circuit board, and when no plug is inserted there, the signal, now labeled preamp out gets sent to the driver of the tube circuit, which incidently doesn't include an output transformer at all and/or some way of the signal of the speaker being connected back into it, but it looks like that has been replaced with some opamp circuits that may emulate the output transformer and speaker impedance effect. So at least in this circuit the valve is not in the circuit when taking the signal from the headphones jack, but is part of the power amp board that is muted when headphones are plugged in. timc on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36473 Wed, 21 Nov 2012 23:20:16 +0000 timc 36473@http://www.voxamps.com/forum/ Tweakfreak, ok, it's for the AD15/30VT so may not be of direct use regards the VT+ but is this any good to you? <a href="http://music-electronics-forum.com/attachments/11022d1284964919-ad15_30vt-service-manual.pdf" rel="nofollow">http://music-electronics-forum.com/attachments/11022d1284964919-ad15_30vt-service-manual.pdf</a> I can't make head nor tail of it myself ... [edited smelling pisstakes] tweakfreak on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36468 Wed, 21 Nov 2012 15:54:08 +0000 tweakfreak 36468@http://www.voxamps.com/forum/ @timc: good point. Gotta look into that. But it means taking the amp apart and doing measurements inside. I don't know when I'll have the time for that. Definitely worth a try though. Another thing: when you plug in the phones, the speaker is quiet. What happens to the tube <-> transformer <-> speaker interaction then? Gotta think about that one! tweakfreak on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36460 Wed, 21 Nov 2012 09:17:06 +0000 tweakfreak 36460@http://www.voxamps.com/forum/ I just saw a service manual of the AD120VT (downloaded from valvetronix.net) and it is clear that the phones output is taken after the output transformer, so the tube sound would also be in the PHONES output in that amp. Voxman, the service manual you mention in <a href="http://www.valvetronix.net/forums/nik-techies-headphone-line-outs-before-or-after-tube-t1012.html," rel="nofollow">http://www.valvetronix.net/forums/nik-techies-headphone-line-outs-before-or-after-tube-t1012.html,</a> is that for the AD120VT? Wouldn't it be nice to see an actual VT+ series service manual... timc on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36455 Wed, 21 Nov 2012 00:00:48 +0000 timc 36455@http://www.voxamps.com/forum/ It could also be that the headphone circuit has a limited output or a limiter, and it's simply that that is being seen? cosmicrepairdude on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36454 Tue, 20 Nov 2012 23:18:04 +0000 cosmicrepairdude 36454@http://www.voxamps.com/forum/ Well, voxman, our esteemed moderator, says it here <a href="http://www.voxamps.com/forum/topic.php?id=1860" rel="nofollow">http://www.voxamps.com/forum/topic.php?id=1860</a> and here <a href="http://www.voxamps.com/forum/topic.php?id=4880" rel="nofollow">http://www.voxamps.com/forum/topic.php?id=4880</a> and here <a href="http://www.voxamps.com/forum/topic.php?id=4212" rel="nofollow">http://www.voxamps.com/forum/topic.php?id=4212</a> and the final word would appear to be here <a href="http://www.valvetronix.net/forums/nik-techies-headphone-line-outs-before-or-after-tube-t1012.html" rel="nofollow">http://www.valvetronix.net/forums/nik-techies-headphone-line-outs-before-or-after-tube-t1012.html</a> . Google is our friend. tweakfreak on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36453 Tue, 20 Nov 2012 23:04:09 +0000 tweakfreak 36453@http://www.voxamps.com/forum/ Anything on the web we can read to educate us? cosmicrepairdude on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36452 Tue, 20 Nov 2012 22:07:34 +0000 cosmicrepairdude 36452@http://www.voxamps.com/forum/ For years, everything I've read, by many folks, including very knowledgeable tech types, has said that the tube is not in the headphone circuit, only the speaker. tweakfreak on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36450 Tue, 20 Nov 2012 21:42:33 +0000 tweakfreak 36450@http://www.voxamps.com/forum/ I'm guessing MASTER control is before D/A, because clipping always and only occurs at +/-2.5V. If a clipped digital signal went through a variable analog amp you would see a clipped signal but at different levels as you turn the MASTER control. The analog part around the MASTER would then have its distinguishable own clipping levels. The Vox signal path shown on p21 of the VT+ manual does not make any distinction between analog or digital system parts, so there's no telling where the D/A converters are. So, my current thinking is that MASTER is followed by D/A and the phones output is taken from that, passed through a filter (speaker "modeling") and fed to the PHONES jack. When no phones are present, the signal goes to the valve reactor. It would still beg the question why the MASTER control setting, since it would be in the digital domain, can not be saved in a preset. In principle that would be an option. Also the manual states that the PHONES output is taken from "before the power amp", which may still mean after the valve reactor. The "power amp" might be the digital solid state thing driving the speaker. (With its own A/D and D/A converters, by the way.) I don't claim to have all the answers yet. cosmicrepairdude on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36446 Tue, 20 Nov 2012 18:27:25 +0000 cosmicrepairdude 36446@http://www.voxamps.com/forum/ How did you determine that the MV comes before the D/A converter? Vox's signal path diagram shows the MV just before the Valve. Since the headphone jack output comes before the tube, but obviously delivers an analog signal, isn't it more likely that the D/A is before the MV, which clearly affects the headphone volume? Or do you think the D/A outputs a signal directly to the headphone jack which then goes on to the valve circuit? voxman on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36445 Tue, 20 Nov 2012 17:35:01 +0000 voxman 36445@http://www.voxamps.com/forum/ Excellent stuff...I just went by my ears, but I had no idea I was so clever! LOL tweakfreak on "The Mythical Master control" http://www.voxamps.com/forum/topic.php?id=6404#post-36443 Tue, 20 Nov 2012 15:35:59 +0000 tweakfreak 36443@http://www.voxamps.com/forum/ Every now and then somebody makes the claim that the Vox VT+ Series amps sound best when the MASTER control is set between 12:00 and 15:00. What's up with that? I did some measurements, and from those I came up with with some thoughts on the matter. The VT+ Series roughly consists of the following parts: 1 - An input part, where the signal from the guitar is fed in, and the analog signal is converted into digital bits: the A/D conversion. From there on it is numbers, not volts. 2 - The Modeling part, where all gain, drive, effects, etc, are applied in the digital domain, which means there is a computer performing all necessary calculations to come up with a number that represents output signal. DSP, or Digital Signal Precessing is what that's called. It is proprietary KORG stuff. 3 - Then there is D/A conversion, turning all the numbers back into volts, going into the next part. 4 - And finally, the Valve Reactor which attempts to put as much tube "feel" as possible into the signal, before it is fed to the power amp and the loudspeaker. It uses information from the modeling part, like certain amp type characteristics, to set up the tubes. (See <a href="http://www.voxshowroom.com/uk/amp/blueVRoverview.html" rel="nofollow">http://www.voxshowroom.com/uk/amp/blueVRoverview.html</a> if you want more detail. It's likely the same principle in the VT+ series.) Measurements As far as I have determined, (and there is some educated guesswork involved here) the MASTER control is located at the end of the modeling part, just before the D/A conversion. I hooked up my measuring equipment to the PHONES output, and watched the output signal. What I saw was this: - turning up the GAIN may cause visible clipping to occur at +/- 2.5 Volt. - turning up the MASTER may cause visible clipping to occur at +/- 2.5 Volt. So, it does not make much difference whether you adjust GAIN or MASTER. In the digital part of the amp, signals can not be higher than +/-2.5V. Now, a closer look revealed something more interesting. With MASTER turned down to 8 o'clock there was no clipping at all. With my modified strat I have tried all amp models with GAIN, VOLUME, TREBLE, MIDDLE, BASS turned up all the way. Some models came close to +/-2.5V, but most stayed well below that clipping level. No doubt a guitar with active electronics or a much higher output may cause clipping, but under normal circumstances, with controls not all being all the way up, there is not much risk of "overdriving" the digital stuff. No amp models showed clipping. That is good and fool proof design! I like that. The only thing left that may cause clipping is the MASTER control. And turning it up will show the signal being clipped to +/- 2.5V at the PHONES output. So, now what? Great story so far, now what's the punch line? Well, you can turn up the MASTER as far as you like, but you have to make sure the analog signal being fed into the valve reactor does not clip! And there's the catch: how can you tell? Answer: you can't. It would have been so simple to add a LED indicator, but they didn't. (So I built my own. Real easy, but that's for another time.) When people claim that the signal sounds "muddy" they may very well hear a clipped signal being fed to the Valve Reactor. It is not so much the tubes causing the distortion, but the modeling part clipping. With MASTER at noon, of all built-in presets, US 2x12 (green) gave me the highest output and might clip a little. Everything else stayed "clean". Conclusion So, is a MASTER setting between noon and 3 o'clock a good idea? I'd say it's a good rule of thumb. Lower than 12:00 will drive the tubes less hard, and higher than 15:00 may cause unwanted digital clipping to become audible. In many cases you can get away with a setting at 3 o'clock. Now you know why, or at least why I think it's an OK rule. voxman on "VOX AGA150 CLIPPING" http://www.voxamps.com/forum/topic.php?id=4874#post-31505 Sun, 01 Apr 2012 18:31:11 +0000 voxman 31505@http://www.voxamps.com/forum/ Turnupthedanger, please post in LOWER case only - see here: <a href="http://www.voxamps.com/forum/topic.php?id=2046" rel="nofollow">http://www.voxamps.com/forum/topic.php?id=2046</a> parsons on "VOX AGA150 CLIPPING" http://www.voxamps.com/forum/topic.php?id=4874#post-31503 Sun, 01 Apr 2012 16:43:36 +0000 parsons 31503@http://www.voxamps.com/forum/ I have this same issue. Seems way to low, volume wise, to be clipping. I am using a Gibson Hummingbird with a Fishman Preamp. Anyone monitoring this forum from VOX? I emailed directly and await a reply. turnupthedanger on "VOX AGA150 CLIPPING" http://www.voxamps.com/forum/topic.php?id=4874#post-25778 Fri, 16 Sep 2011 19:05:30 +0000 turnupthedanger 25778@http://www.voxamps.com/forum/ HI I PLAY A GIBSON J200 WITH A FACTORY INSTALLED FISHMAN AURA PICKUP SYSTEM AND WHEN I NEED PLENTY OF VOLUME WHEN PLAYING WITH MY BAND THE AMP IS CLIPPING SO MUCH IT SOUNDS TERRIBLE ,DOES ANYONE NO HOW I CAN COMBAT THIS PROBLEM . CHEERS DEAN kampanita on "Recording issues ... clipping" http://www.voxamps.com/forum/topic.php?id=2882#post-14709 Tue, 13 Jul 2010 12:46:07 +0000 kampanita 14709@http://www.voxamps.com/forum/ @deadlychicken: Be sure to be using a BETA version of Audacity, i'm using Audacity 1.3 Beta ( Unicode ) that goes right with ASIO ( JamVOX MME ). If you use a commercial version or final release of Audacity, ASIO is not working .... Have a look to my config at Audacity 1.3 Beta ( Unicode ) version: <a href="http://yfrog.com/4raudacitysetupj" rel="nofollow">http://yfrog.com/4raudacitysetupj</a> blacksun3 on "Recording issues ... clipping" http://www.voxamps.com/forum/topic.php?id=2882#post-14618 Fri, 09 Jul 2010 01:19:32 +0000 blacksun3 14618@http://www.voxamps.com/forum/ Cool if it's nearly ok now - reading your first post I thought you did have the problem not only using audacity to record. So let's rock!^^ (And I hope you'll find a solution for no clipping at all, even slight one)