SlagJones Posted May 4, 2009 Posted May 4, 2009 The V3 Vjr had outputs for 4,8 and 16 ohms. Does the speaker ohms have any effect on the sound or are those outputs mainly for more versatility when connecting to multiple speakers and the different ohmage when wired parrallel or series and what not?
Eracer_Team Posted May 4, 2009 Posted May 4, 2009 You typically will not connect a 4ohm speaker and an 8ohm speaker to the outputs at the same time (there are rules of loading). So to answer, not from my ears I haven’t heard a 4ohm speaker sound different than the same brand of speaker rated at 8ohms Now the speakers do sound different from brand to another, you’ll have to experiment on that. There are those that claim to hear the difference between solid core, stranded and cloth wiring in their amps too; I’m not one of those either.
m-theory Posted May 4, 2009 Posted May 4, 2009 There are different outputs for different speaker loads because the output transformer is designed with taps for those speaker loads. If your speaker load is 4 ohms, you plug into that jack, and so on. You don't plug into more than one of those output jacks at the same time. In a perfect world, all three would yield equal output and would make the amp equally happy. In reality, that's not the case. There will be one load that a given amp prefers to see, and the difference can be quite astonishing, in terms of output and overall tone. When I brought my baby will build into my amp tech to have him throw on the scope, we checked output from 4, 8, and 16 ohm taps, under all three load options. We measured anywhere from not even 2 watts of output to just over 14 watts. We identified two tap and load options that the amp was truly happy with, and I use one of them regularly. Some options made the amp virtually angry, as seen by waveform and measured output. The point is, as a general rule, if you stick to what a manufacturer recommends for speaker loads, the amp will tend to perform better than if you stray from the farm. Additionally, the further you stray, the harder it may be on output transformer and tubes, because the amp will be stressed by trying to provide output to a load that it doesn't want to see. The amount of tolerance an amp will have to load mismatches like this varies widely from amp to amp. Some, such as many old Fenders, can tolerate a 100% mismatch either direction without anything more adverse than a slightly warmer transformer. Others, such as the diminuitive Champs, will likely commit suicide via output transformer meltdown if you provide it with such a mismatch. Regardless, straying from the stated design can potentially lead to problems. There's really no way of knowing on a given amp until you put it on a scope and signal generator and test various options. As for mixing speakers of different loads, you need to calculate the load of those speakers, in order to present the proper load to the amp, by plugging into the corresponding output jack. Mixing different loads isn't typically something that anyone would recommend, but ultimately, it's what the amp sees as a load that matters, in terms of whether or not you're going to be abusing your output transformer and/or output tubes.
SlagJones Posted May 4, 2009 Author Posted May 4, 2009 When I said multiple speakers, what I meant was versatility in connecting to different cabinets containing multiple speakers and whether the cabinet has total impedance of 4,8, or 16 ohms. I understand that you don't use more than one output jack at a time. Thanks for the great info everyone.
Steven Lister Posted May 4, 2009 Posted May 4, 2009 The V3 Vjr had outputs for 4' date='8 and 16 ohms. Does the speaker ohms have any effect on the sound or are those outputs mainly for more versatility when connecting to multiple speakers and the different ohmage when wired parrallel or series and what not?[/quote']Speaker ohms do not affect tone -- watts do have an effect -- this is as to the speakers themselves. Amp output ohms do affect tone (although this subject has continued debate). The theory is that an OT operates at maximum efficiency (efficiency = passing greatest % of amplified signal out to the speaker) when all of its winding is used. On multiple tapped OTs, like the VJr, the lowest ohm out uses the least amount of the winding and the highest out uses the most/all. My ears agree. When I switch from 4 or 8 ohm to the 16 ohm output on my Vjr., I notice a increased definition in note complexity -- especially at high volume and high gain levels. So multiple outs are put there for convenience, but they do seem to have tonal significance. Hit every BLUE NOTE baaaby..., I'm going to play on:-"
jefrs Posted May 7, 2009 Posted May 7, 2009 The o/p transformer is most efficient when all of its windings are used. So the 16ohm output, into a 16ohm load, is the one to go for. I can configure my ext cab speakers as 16ohm or 4ohm, the 16ohm config sounds best, the 4ohm sounds muddied. The amp o/p transformer must be loaded correctly. You can put a slightly higher load on but not a lower one. If you run 8ohm and 16ohm in parallel you get 5.3ohm, that gets put into the 4ohm socket, not the 8ohm hole, certainly not the 16ohm socket.
m-theory Posted May 7, 2009 Posted May 7, 2009 The o/p transformer is most efficient when all of its windings are used. The only way to know for sure which tap and load makes the amp the happiest with a given bias point is to throw it on a scope with an audio generator signal into it, and try each tap into all load options. You can put a slightly higher load on but not a lower one. This depends on the amp and the transformer. Again, some older Fenders can tolerate 100% sway in either direction. And, the only way to be certain is, once again, to put the amp on a scope.
jefrs Posted May 7, 2009 Posted May 7, 2009 I was relaying wisdom received first hand from a chap who designs o/p transformers and advice from the tech at Laney. It does not actually disagree with m-therory's first paragraph in the 4 May post above. Given that valve amps and their transformers are tolerant and their designs often sloppy, it is possible to mis-match and get away with it. But it is safest to overload the winding rather than under-load, or it may draw too much current.
Dave Posted May 8, 2009 Posted May 8, 2009 Amps will all be rated in output power for different loads, some go from 2 ohms to 16 ohms. At 2 ohms, the power output will be substantially higher than at 16 ohms, but the load on the amp and the heat generated within the output stage is tremendous! As stated before, the sweet spot is where the amp feels comfortable with the coupling between the output tubes, the output transformer, and the speaker load. The more turns used in the transformer (higher flux, higher impedance) will generate the most pleasing output range. And a user should remember that impedance does not equal DC resistance. The impedance of an amp/speaker combination changes with frequency for a given rated inductance in the output transformer/speaker combo. This alone will dictate how the amp responds at a given frequency and playing habits.
wedgeSG Posted May 10, 2009 Posted May 10, 2009 OK the thread has got my curiosity up so I'll throw this out here for suggestions. My modded VJ has a Hammond 125ESE transformer and Marshall mods. I run out to a 2x12 that has a pair of 16ohm Hellatones. Each of these speakers has two positive and two negative connection terminals. I installed a jack plate that has two jack locations and basically doubled a parallel wiring setup. Running complete parallel wiring to each jack - this eliminates the need for a Y adapter if used in a chain. So 2 -16ohm 12's in parallel = 8 ohm cabinet. With two jacks I go from the VJ into the 2x12 and then with another cable - run into a cab with a single 8 ohm 10". Two 8 ohm cabs = 4 ohms. I start from the 4 ohm jack on the VJ. This being stated referenced against the comments made here about using ALL of the OT's windings at 16 ohms and the benefits therein... am I short changing my setup? Using my current cabs and speakers could this be wired in such a way to improve the output and performance of my components? I don't want to lose any of my current hardware but rewiring for a upgrade is definately do-able. I've actually been quite pleased with the outcome and rarely try to fix what ain't broke... but the idea of getting even more out of it is almost so unbelievable I would just about have to try it just for peace of mind and outright amazement. So how 'bout it guys... have I left some cards on the table somewhere? Wedgie
Steven Lister Posted May 10, 2009 Posted May 10, 2009 .... I run out to a 2x12 that has a pair of 16ohm Hellatones.... am I short changing my setup? Using my current cabs and speakers could this be wired in such a way to improve the output and performance of my components? .... So how 'bout it guys... have I left some cards on the table somewhere? Wedgie Maybe...' date=' but you're going to have to experiment a little to find out for sure b/c there are too many variable to say. On paper 1 + 1 + 1 = 3 but it doesn't work that way with amps/ohms/tone. What I would do is take the simpliest re-wiring route to 16 ohms and see what you think. It's easy enough to do with your set-up of 4, 16 ohm Hellatones in two 8 ohm cabs -- series the cabs and waalaah 16 [rig a jumper wire from the - terminal of one cab to the + of the other and connect the unused +/- of each cab to the amp's 16 outlet'] Test. No, now really test... through the paces, volume levels. Any difference you want to keep? Going from 4 ohms now to 16 should give you the most difference, so if you are going to hear improvement/decline this simple test should provide answers. Good luck..., oh and it's obligatory that anyone begging tone advice on the forum has to report back findings to help everyone else decide what to do. LOL Hit every BLUE NOTE baaaby..., I'm going to play on:-"
Eracer_Team Posted May 11, 2009 Posted May 11, 2009 from what I understand the load to power rating only stands true for solid state as you move from 2ohm, 4, 8, then 16 ohm loads the power changes. With lower ohm-age being of higher power. from what I understand about tube amps is they do not do this change in power rating just because you are using different taps of the OT. What is happening is you are saturating the core of the transformer from one end to the other using the highest ohm tap, where using a lower ohm tap would only saturate portion of the core/wire. Power doesn't change. So what you would be hearing is a change in tone due to the extra wire usage in the OT. What ever you do; don't take your lower ohm load and put it in the high ohm output. You will make the amp work harder and could be disastrous for the amp itself
TWANG Posted May 11, 2009 Posted May 11, 2009 you can run two different speakers off the vj.. isn't it 4ohm into the 8 ohm and and 8 ohm into the 16 ohm? TWANG EDIT IT'S 16 OHM SPEAKER TO 8 OHM JACK AND 8 OHM SPEAKER TO 4 OHM JACK. But I notice gil mentioned the hammond Ot so I'm not sure it works with just any. TWANG
wedgeSG Posted May 12, 2009 Posted May 12, 2009 I'm only using the 4 ohm jack on the VJ. From the 4 ohm jack to the "IN" jack of a 2x12 cab that has a pair of 16 ohm speakers (each of these has 2 positve and 2 negative terminals so the pair of speakers have a total of 4 positive and 4 negaitive connection points.) the "IN" jack connects to half of those and the "OUT" jack connects to the other remaining matched +/- four. Either jack has the same job and will work independantly.... or like I'm doing it now.... from the "OUT" jack into another cab that houses a single 8 ohm 10" 4 ohm tap - cable to "IN" of 2x12 (pair of 16 ohms/parallel = 8 ohms) - cable from "OUT" into single cab with 8 ohm 10" (single 8 ohm/ pos. to pos./neg. to neg.) Thus- 8 ohm cab, into 8 ohm cab. 4 ohm load into 4 ohm tap. As it is now: I can run either the 2x12 or the single 10 into the 8 ohm tap, or "daisy chain" and run both into the 4 ohm tap. The later was the initial idea: getting the fullness and bass of closed-back 2x12 coupled with the high end projection of a half-back single 10" to get a wider total sonic range. It worked out really well, (IMHO), just wondered if my logic was screwy.... Wasn't sure if I was getting that across in my former post.... Wedgie
Eracer_Team Posted May 12, 2009 Posted May 12, 2009 Daisy chaining in combinations works fine as long as you know what the ohm load is and which jack to plug you speakers into. Some like Twang that had a combo with the 8” speaker wanted more with out having to go to the head route. So they kept the 8” speaker connected and added an external speaker(s) but as Twang said; it’s been a while. http://www.bcae1.com/spkrmlti.htm Instead of re-inventing the wheel; I borrowed these comments from the SEWatt FAQ thread below. http://www.sewatt.com/node/18024 From Gil For the power tube to sound its best, it needs to see a certain amount of impedance reflected through the OT. In the case of the VJr, the el84 sees a 5k impedance when an 8ohm speaker load is plugged into the 8ohm jack. Same 5k it sees when a 4ohm speaker is plugged into the 4ohm jack, or 16ohm speaker into the 16ohm jack. But if you double the load the OT sees, by plugging the 16ohm speaker into the 8ohm jack (or 8ohm into 4ohm jack), you also double the impedance the tube sees, which would now be 10k. Go the other way, and you cut the reflected impedance in half. But the power tube wants 5k to sound its best, so... From Twang you can plug an 8ohm speaker into the 4 ohm jack.. WITH a 16 ohm speaker plugged into the 8 ohm jack. I've done that with a combo and an epi cab with an 8 ohm speaker.. and it sounded really good to me
m-theory Posted May 12, 2009 Posted May 12, 2009 from what I understand about tube amps is they do not do this change in power rating just because you are using different taps of the OT. This isn't correct. Changing taps on a tube amp absolutely DOES change the output power, and it can be quite significant. While I was dialing in my Baby Will a couple months ago, my tech ran an audio signal into the amp, and we tested each tap (5.6k and 8.2k, each at 4/8/16 ohms) into 4, 8, and 16 ohm loads. We measured output of barely over 1 watt all the way up to 14.3 watts. Only two tap/load combinations got me above 14 watts, one was the 5.6k 8 ohm tap into an 8 ohm load, and the 5.6k 16 ohm tap into a 4 ohm load. The latter would undoubtedly reduce tube life considerably.
Eracer_Team Posted May 12, 2009 Posted May 12, 2009 Interesting you should say that M, the Baby Will is of course a push-pull amp where the VJ is a single ended tube amp. I'll have to double check the info I have; but maybe you are seeing that on the BW because of the 50% duty cycle of a P-P amp vs the 100% duty cycle of a SE amp. Haven't had time to read this; but it sounds interesting... http://www.transcendentsound.com/amplifier_output_impedance.htm Also when the original valvejunior.com web site forum was created when the VJ's were in their infancy I asked about running the amp at 4ohms as opposed to the 8ohm or 16ohm loads since I knew that a solid state amp would and will increase its power output significantly. The EE's on the site at that time stated that the amp would not produce a variable power curve like the solid state amps' and over the past few years I've read similar things. Just read this thread. http://forum.ecoustics.com/bbs/messages/1/452675.html Tube amps don't operate in the same way solid state amps will when the load is changed. Since tubes are high impedance output devices they require an output transformer to step down their impedance in order to adequately drive a typical loudspeaker load. Higher cost tube amplifiers will have output transformers with multiple taps (2,4,8,16) for various impedance loads to provide the highest power, lowest distortion and broadest frequency response into any speaker. When only one tap is provided the manufacturer has chosen a specific tap/load and then chooses to advertise the amp has the ability to drive any load between such and such value. They are not necessarily lying but they are not telling you the truth either. When the load on a tube amplifier is mismatched by using the incorrect transformer tap, the amplifier will produce slightly more or slightly less power but the wattage will not increase as much as a transistor amplifier under the same conditions. (When multiple taps are provided a tube amplifier should produce the same output voltage at any tap; therefore, a well executed 40 watt transformer coupled tube amp should produce 40 watts at the 4,8 and 16 Ohm taps when the load is properly matched.) A 40 watt tube amp will produce, on average, no more than 45 watts and no less than 30 watts when the tap/load is severely mismatched. When the amplifier manufacturer doesn't provide adequate specifications and the speaker manufacturer just makes up numbers to fit a spec sheet, it is difficult to predict what will happen when the amplifier's load changes. I assume you know speakers are not typically eight or four Ohms throughout their response range. They vary broadly and any particular "four Ohm" (nominal load) speaker might dip to below two Ohms and rise above 30 ohms. Or it might be a very consistent four Ohms over most of its frequency response range. This variation in the impedance curve is important to know when pairing any loudspeaker to any tube amplifier. It is also important to know the electrical phase angle of the speaker at the lowest and highest impedance points in the speaker's range. Impedance and phase angle together determine how "tube friendly" the speakers will be. If you cannot determine these two measurements for any particular speaker (the manufacturer should be able to provide the information you require), you should pair a tube amplifier with a fairly high impedance load speaker. Remember "eight Ohm" speakers vary also and can still be four Ohms or lower at some frequencies
wedgeSG Posted May 12, 2009 Posted May 12, 2009 If I'm reading this right... I think my homework was correct and my setup is good: wouldn't you say? Wedgie
Steven Lister Posted May 13, 2009 Posted May 13, 2009 If I'm reading this right... I think my homework was correct and my setup is good: wouldn't you say?Wedgie Your setup is just fine/matched correctly. But you may well be leaving untapped tone "on the table' date='" as it were -- as well as overworking VJr. at peak loads by using the 4 ohm (least efficient) output tap. Your prior post indicated to me that you were seeking more tone from what you have, if more tone was available. My reply to that remains the same -- you are going to have to experiment to find out for sure. The way to experiment is to change you current setup. With a little re-wiring wizardry you can alter speaker impedence load so that you can use more of VJr.'s OT wiring (and hopefully gain more tone in addition to putting less load/strain on the VJr. during peek load/high volume conditions). Your current setup: 2x12 (16 ohms parallel wired) @ 8 ohm impedence, daisy chained (or again parallel wired) to 1x10 @ 8 ohm impedence =4 ohm into Vjr. 4 ohm output [b']Suggested setup:[/b] 2x12 @ 8 ohm (no change) but wire it in series (not daisy chained) to your 1x10 @ 8 ohm -- that will double your total impedence to 16 ohms -- then you can plug into the 16 output tap of VJr. and see what you think regarding tonal improvement if any. As I said earlier, I have used various speaker combinations matched to the VJr. 4, 8, 16 outputs, and have consistently noted better tone from VJr.'s highest ohm output tap when correctly matched to the speaker load. Granted speaker impedences are not static across their load range. But there is no need to complicate a simple speaker "hook-up" scenario with "amp building" theory. Use the ohm rating of the speaker/cab to make your decisions to wire/match up to VJr. output taps. cgil's quoted comments agree with what I and others are saying --- using more/all of a valve amps OT winding tends to produce a more efficient response -- i.e. improved tone output to the loudspeaker. Hit every BLUE NOTE baaaby..., I'm going to play on:-"
wedgeSG Posted May 13, 2009 Posted May 13, 2009 Sounds like I need to break out the 'ol soldering iron, thanks so much for the help I'll move some connections about and give it a whirl............ Wedgie
Dave Posted May 13, 2009 Posted May 13, 2009 SS amp output stages are generally low impedance outputs that can directly connect to the speaker load. A tube output is a high impedance load that must be matched to the speaker using a matching transformer, sometimes utilizing multiple taps. The SS amp, with its single direct coupled output will vary more widely in its coupling Q match when connected to various impedance loads. Thus, the label on the back of SS amps that states that the power rating is, say, 200 watts at 2 ohms, 100 watts at 4 ohms, and 50 watts at 8 ohms. The user manual usually cautions the user that operating at lower impedances and high volumes can cause early amplifier failure (due to heat in the output circuit). This white paper talks about the relationship between ss direct coupled output circuits and tube output circuits with matching output transformers and the way that the transformer actually responds to overdrive. http://www.peavey.com/support/technotes/hartley/chapter_3.pdf
m-theory Posted May 13, 2009 Posted May 13, 2009 Suggested setup: 2x12 @ 8 ohm (no change) but wire it in series (not daisy chained) to your 1x10 @ 8 ohm -- that will double your total impedence to 16 ohms -- then you can plug into the 16 output tap of VJr. and see what you think regarding tonal improvement if any. Based on my recollection of what my Vjr sounded like into a 4 ohm load vs. 8 ohm load, prior to my octal modding it and going strictly 8 ohm load, I'd say that 4 ohms isn't the amp's favorite place to be. I found the amp to sound noticeably less favorable into a 4 ohm load. Hearing what the 8 ohm sounded like in comparison, but having no 16 ohm load to have compared at the time, I can only assume that 16 ohm would sound considerably better than 4. Definitely worth a try. I'll have to double check the info I have; but maybe you are seeing that on the BW because of the 50% duty cycle of a P-P amp vs the 100% duty cycle of a SE amp. Actually, there's no 50% duty cycle on that amp. It's drawing almost exactly the same amount of current at full throttle as it does at idle, like a SE amp. The EE's on the site Beware the so-called "experts" that live on internet forums! They may very well have a certificate hanging on the wall, upon which they stake their claim of "EE" or "amp tech," but rest assured, those with real world experience don't generally have the time to poke around on message boards all day long! Given the choice between relying upon a tech who lives on the internet and one who buries his head in solder fumes all day long, I'll take the latter, without any hesitation whatsoever. You cannot replace years of working experience with books or diplomas.
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