http://www.voxamps.com/forum/ VOX | Discussion Forums Tag: rms en Wed, 22 May 2013 07:13:52 +0000 http://www.voxamps.com/forum/topic.php?id=6111&page=2#post-34711 Tue, 04 Sep 2012 15:55:16 +0000 vox_davec_dev 34711@http://www.voxamps.com/forum/ <p>Hi Everyone</p> <p>Thought I’d wade in here to set a few things straight</p> <p>1. the VT80+ is capable of doing 120W continuous.<br /> 2. 54W refers to the amount of mains power used and this is a maximum figure.. class D amplification is very efficient and this allows for low power consumption.<br /> 3. it was referred that all other amps that were looked at had a higher power consumption, this would either me class AB solid state amps or Tube amps.. Tube amps consume way more power than the put out.. typically it can take 440W of mains power to run a 100W tube amp<br /> 3. We're sorry to hear about your less than positive experience with VOX captainfruitbat. and on behalf of VOX all i can do is apologise</p> <p>We're not pulling the wool over anyone's eyes, we love VOX and most of all we love our customers</p> <p>Please feel free to contact me directly if you have any further queries<br /> davec "at" voxamplification "dot" co "dot" uk</p> <p>Thanks for your time<br /> Dave<br /> R&#38;D Manager<br /> VOX Amplification </p> http://www.voxamps.com/forum/topic.php?id=6111&page=2#post-34681 Mon, 03 Sep 2012 05:18:35 +0000 captainfruitbat 34681@http://www.voxamps.com/forum/ <p><em>"If it sounds loud enough, it's good enough". </em></p> <p>Agreed, but this one ain't loud enough. It's no louder than the amp I upgraded from.... Of course, in an ideal world I would have tried before buying, including a volume comparison against others, but that's difficult when there are no local Vox dealers...</p> <p>Latest (and final) developments on this issue:</p> <p>1. The power amp in the VT80+ is confirmed as a class D amp with efficiency just over 90%. I got this from an amp tech here in NZ, not from Vox. The amp chip is a Texas Instruments TAS5615, which is capable of max 240 watts into 4 ohms when bridged. The spec sheet can be found via Google. Plenty of power on tap in the amp section then. The trouble is that if the power supply won't consume more than 54 watts (which Vox have confirmed to me), the chip won't see enough power to maintain the claimed RMS output continuously. This is the sort of thing you see all the time on cheaper home cinema amps and powered PC speakers, where the limitation on RMS power is in the power supply rather than the amplifier chip. It's the first time I've seen it on a guitar amp, and it's sad to see. </p> <p>2. My VFS5 footswitch (or the jack socket in the back of the amp) has given up completely now. Either the footswitch doesn't power up at all, or if it does, half the buttons don't operate. No amount of socket cleaning and plugging/unplugging has solved it. Not good considering only about 10-12 hours use home and rehearsal use only. </p> <p>3. The retailer I bought the amp from has agreed to give me a full refund, which I will be spending on another amp. Based on my recent experience, it probably won't be a Vox, which in some ways is a shame, because I've wanted one for years, and I really wanted to like this amp...</p> <p>So sayonara Vox dudes. Enjoy your amps, I know there are a lot of good ones out there, and my experience may not be typical. Maybe I will be back when my budget will run to a "proper" Vox (I'd still love a handwired AC30....). </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34672 Sun, 02 Sep 2012 21:55:45 +0000 tweakfreak 34672@http://www.voxamps.com/forum/ <p>Don't get worked up. It's the way of the world, unfortunately.<br /> 1 - it's just marketing numbers<br /> 2 - you can tell because if the watts "output" is more than the watts "consumed" it is physically impossible. Only sales people can come up with that.<br /> 3 - Korg/Vox is not the same as Vox back in the sixties. All these guys currently care about is profit, no matter how much crap you have to put in the sales brochures.<br /> 4 - you can see for yourself: ask them a question. Do you get a sensible answer? There you go!<br /> 5 - if you want to know the output of your amp, do the following.<br /> = connect an oscilloscope to the speaker.<br /> = play as loud as you can. The output voltage will "clamp" to the max voltage the power supply can produce.<br /> = that gives you a good idea of how much power you get out of the amp at most.<br /> 6 - and, finally, forget about output power. If it sounds loud enough, it's good enough. Period. End of story. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34654 Sat, 01 Sep 2012 22:46:53 +0000 captainfruitbat 34654@http://www.voxamps.com/forum/ <p>EDIT: The Wikipedia link on root-mean-square that Vox referred me to does not work in my previous post because of the period at the end of the link. Correct link is here: <a href="http://en.wikipedia.org/wiki/Root_mean_square" rel="nofollow">http://en.wikipedia.org/wiki/Root_mean_square</a></p> <p>Interestingly, this page has a section on power amplifier efficiency that says:</p> <p><em> "Efficiency is normally measured under steady-state conditions with a sinusoidal current delivered to a resistive load. The power output is the product of the measured voltage and current (both RMS) delivered to the load. The input power is the power delivered by the DC supply, i.e. the supply voltage multiplied by the supply current. The efficiency is then the output power divided by the input power, and it is always a number less than 1, or, in percentages, less than 100."</em></p> <p>I think that description confirms my argument rather than Vox's, don't you? </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34460 Sat, 01 Sep 2012 05:01:15 +0000 captainfruitbat 34460@http://www.voxamps.com/forum/ <p>Another response from Vox Support in the UK. It was pretty brief, but they did answer almost all of my questions. Here's the detail, point by point:</p> <p>1. I asked them to absolutely confirm that 54 watts is the maximum power consumption for this amp. Their response: "Yes, this is correct."</p> <p>2. I asked them to confirm whether the quote 120 watts RMS is a continuous figure or more of a momentary peak figure. Their response: "RMS is an average, the figure is normally quoted when a sine wave is injected into the circuit. As you are from an engineering background, you will be familiar with the math’s and methods involved in reaching this figure <a href="http://en.wikipedia.org/wiki/Root_mean_square." rel="nofollow">http://en.wikipedia.org/wiki/Root_mean_square.</a>" This response actually didn't answer my question, or tell me anything I didn't alreayd know.</p> <p>3. I asked that, if the 120 watts RMS is a momentary figure rather than a continuous one, what is the actual continuous RMS output figure for this amp. Their response: "120 watts RMS".</p> <p>4. I said I agreed with their earlier point that amplifier output depends in part on the efficiency of the circuit design, but asked them whether or not they agreed with me that no amplifier design is more than 100% efficient. They chose not to answer that one.</p> <p>They restated what they told me in their previous email - that the VT80+ does produce 120 watts RMS into a 4 ohm load (although I note they don't use the word "continuous").</p> <p>They closed the email by saying they would not discuss this issue with me any further, and if I felt they were misleading customers, I should take this up using whatever method was appropriate in my country (I'm in New Zealand). I plan to do so, as I believe they are in breach of consumer law here.</p> <p>To sum up: If what they say is correct, this amp can produce a continuous output of 120 watts RMS while consuming no more than 54 watts of power. Am I the only one on here who thinks they're breaking the laws of physics here? Interested to hear what you all think.</p> <p>On a side note, I was in my local music shop yesterday. They are not a Vox dealer, but they do sell amps from Marshall, Fender, Mesa Boogie, Orange, Line 6, Soldano, Gallien Kruger and others. We did a quick, unscientific survey of about 15 different amps of all shapes and sizes. Every single one has a rated power consumption that is significantly higher than the quoted RMS output, and in some cases it is three times or more. Is anyone aware of any amp builders other than Vox who are claiming more power output than power input? I know it's not just the VT80+, their figures for the whole Valvetronix range are similarly supicious. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34342 Thu, 30 Aug 2012 11:00:35 +0000 captainfruitbat 34342@http://www.voxamps.com/forum/ <p>Wouldn't that be nice..... If enough people complain, maybe they will at least solve this problem for newer amps. I know they've got to keep the costs down, but I think they're shooting themselves in the foot here. As a first time Vox purchaser who has owned Marshall, Fender, Hughes &#38; Kettner, Randall, Line 6 and other amps over the last 30+ years of playing, I can honestly say that even though I LOVE the way this amp sounds, the combination of unreliable jack sockets, dodgy quoted power output and non-existent customer service from the distributor here in New Zealand means I will almost certainly never buy Vox again. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34341 Thu, 30 Aug 2012 10:09:01 +0000 voxman 34341@http://www.voxamps.com/forum/ <blockquote><p>Vox should really be giving away free cans of contact cleaner with every one of these amps they sell.... </p></blockquote> <p>Nope..They should just be using better quality jack socket inputs that don't oxidise/stick!!</p> <p>-------------------------------------------------------------------------------- </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34340 Thu, 30 Aug 2012 03:40:42 +0000 captainfruitbat 34340@http://www.voxamps.com/forum/ <p>I actually ran my VT80+ alongside our other guitarist's 30 watt Spider IV last weekend. On clean sounds there really isn't much volume difference. The VT80+ sounds fuller and has more bottom end, but that may just be down to differences in the speaker or the models we were using. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34339 Thu, 30 Aug 2012 01:59:28 +0000 grenadilla 34339@http://www.voxamps.com/forum/ <p>These VT+ amps are not as loud as the numbers suggest. I have the big VT120+ and it is as loud as a set of drums, but the 1 12 and 1 10 amps might not cut it, I figure a 50 watt Marshall is louder tha your VT 80+.The 120+ I have sounds good, but with a ton of bass. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34326 Wed, 29 Aug 2012 05:40:05 +0000 captainfruitbat 34326@http://www.voxamps.com/forum/ <p>No problem. I should point out that I'm still loving the amp despite this issue. And despite the fact that after just a month I'm already having the already-well-publicised issues with the input jack socket and the footswitch socket. Vox should really be giving away free cans of contact cleaner with every one of these amps they sell.... </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34325 Wed, 29 Aug 2012 04:41:26 +0000 lusthaben 34325@http://www.voxamps.com/forum/ <p>Thanks for pursuing this. . .as much as we love the Vox sound, having the facts is vital. . </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34323 Wed, 29 Aug 2012 01:46:30 +0000 captainfruitbat 34323@http://www.voxamps.com/forum/ <p>I have a response from Vox Support in the UK, but it only partially answers my question and seems almost deliberately vague and misleading. Here are the main points - apologies if it's a bit long-winded:</p> <p>1. They have confirmed that the stated power consumption (54 watts for the VT80+) is the MAXIMUM power the unit will draw from the mains supply.</p> <p>2. They say (and I quote) "Output power is most accurately quoted as RMS (an average of the peak voltage multiplied by 0.707) when a specific load is connected, in the VT80+ case - 4 ohm". However, they didn't provide any figures on this, like what the peak voltage might be in the VT80+. The use of the word "peak" makes me nervous here - are they just taking the peak output and multiplying by 0.707 to convert to RMS? Because that's a VERY different scenario than quoting a CONTINUOUS RMS output figure, which is what most guitar amp makers do (including VOX on their other amp ranges).</p> <p>3. They state that there is no fixed formula to calculate output power from input power, because of variation in circuit design and efficiency. This is absolutely true with one HUGE caveat - no amplifier circuit is more than 100% efficient.</p> <p>4. They refer me to a web article that discusses home cinema amps whose quoted RMS output is more than their quoted power consumption. This is completely bogus because such amps have multiple channels, and are often measured with only one channel at a time driven. Such amps are not capable of producing the same power per channel when all channels are driven together due to power supply limitiations. This argument just doesn't apply to a mono guitar amp. (The article is at <a href="http://www.hifivision.com/amplifiers/2481-power-consumption-v-s-output-power.html" rel="nofollow">http://www.hifivision.com/amplifiers/2481-power-consumption-v-s-output-power.html</a>)</p> <p>5. One of the questions I asked them was whether the 120 watts RMS quoted in the VT80+ manual was a continuous RMS figure or a momentary figure. They chose not to answer this.</p> <p>6. I also asked them what the continuous RMS figure actually is, if the 120 watt figure is indeed just a momentary figure. They didn't answer that one either. </p> <p>7. They ended with "I can confirm that the VT80+ will deliver a maximum of 120W RMS into 4 ohms".</p> <p>I have gone back to them for further clarification, and will report back here when I get a response. In the meantime, I am going to assume I have upgraded my 40 watt (continuous RMS) 1X12 Fender Mustang II to what is probably a 40 watt (continuous RMS) 1X12 Vox. Does the Vox sound better than the Mustang? I think so - now that I've started to figure out how the power and master volume controls interact. IS it easier to use? Yup, no question. Is it louder? Definitely yes on high gain settings, but on cleans I'm not convinced. Am I glad I didn't go for the VT40+? You bet..... </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34277 Fri, 24 Aug 2012 04:16:02 +0000 captainfruitbat 34277@http://www.voxamps.com/forum/ <p>I emailed the online retailer I bought the amp from, and got a response in 10 minutes. That's more like it! However, the response doesn't make a lot of sense.... "Basically the VT80+ has up to 120 watts of useable power because of the tube pre amp in it". And also "The Mustang III consumes a lot more power then the VT80+ because it has a screen on it".</p> <p>Given that the tube in question is only a small pre amp tube (about 1 watt I believe), and that the small screen on the Mustang III will only consume a very small proportion of the amp's power, these statements are clearly not valid or sensible. However, to this guy's credit, when I pointed all this out he accepted it and promised to pass my question on on to their technical guy. Watch this space...... </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34276 Fri, 24 Aug 2012 01:38:32 +0000 gregm 34276@http://www.voxamps.com/forum/ <p>Ah, I see. Question on. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34275 Fri, 24 Aug 2012 00:43:56 +0000 captainfruitbat 34275@http://www.voxamps.com/forum/ <p>Really? I've not heard that before. Is that documented anywhere?</p> <p>Every other guitar amp I've ever owned, and every hi-fi amp, and every home cinema amp (we're talking a lot of gear here by the way) has had a quoted power consumption figure that is significantly higher than the quoted RMS power output, in many cases it's double or more. This Vox amp is the only exception to this I have ever seen. That's why I'm questioning it. Believe me I'm happy to be proved wrong about this. If only someone at Vox in the US or the local NZ distributor would repsond to my emails.... </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34274 Fri, 24 Aug 2012 00:09:11 +0000 gregm 34274@http://www.voxamps.com/forum/ <p>54 is a consumer use average. Everything that runs on energy is figured that way. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34273 Thu, 23 Aug 2012 22:30:39 +0000 captainfruitbat 34273@http://www.voxamps.com/forum/ <p>No response yet from Vox USA or the local distributor here in NZ - not even an acknowledgement of receipt of my emails. Nice customer service guys!</p> <p>A little further investigation shows that the 54 watt figure isn't a simple misprint in the manual, because the same figure appears on the back of the amp itself. Contrast it with the Fender Mustang III, which is sold as 100 watt amp and was the other one I was considering buying. It has a power consumption of 310 watts RMS, which is far more believable for a 100w RMS output, particularly when you consider some of the power is needed to drive the preamp and all the modelling electronic wizardry. Even the little 20watt Mustang I consumes 70watts, 16 more than the VT80+. If the 54 watt consumption figure is correct, there is no way that the VT80+ can produce a CONTINUOUS 120 watt RMS or even 80 watt RMS output - if it can then Vox have solved the world's energy crisis by creating something that outputs more power than it consumes. I suspect that the continuous RMS capability is more like 35-40 watts, and the "120 watts RMS" quoted in the manual is more of a momentary peak figure. I love the amp, I think it sounds great, but one of the main reasons I bought it was to get significantly more power than my Mustang II, and I'm just not convinced it gives me that. I am left feeling that I have been misled, which taints the whole experience for me. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34265 Thu, 23 Aug 2012 06:30:32 +0000 iagtrplyr12 34265@http://www.voxamps.com/forum/ <p>Carry on, Captain. I just picked up a VT80+ tonight and find your query fascinating. Vox may be onto something big here, or you may be onto something even bigger. Good hunting! </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34237 Tue, 21 Aug 2012 10:09:47 +0000 captainfruitbat 34237@http://www.voxamps.com/forum/ <p>I have just posed this same question to Vox's importer here in New Zealand. Will post here if I get a response.</p> <p>And if anyone from Vox is listening, please update the contact details on your website for the New Zealand Vox dealership. "www.korg.co.nz" no longer exists, and nor does the email address you have listed. </p> http://www.voxamps.com/forum/topic.php?id=6111#post-34230 Tue, 21 Aug 2012 06:38:35 +0000 captainfruitbat 34230@http://www.voxamps.com/forum/ <p>Well done.... funny and uninformative all at the same time.... :-) </p>