flyfisher

The OP referred to 'innovations in the bass world' - do we take that to mean [u]unique[/u] to the bass world or merely the adoption of things? Electric basses, jack plugs/sockets, class D amps etc are certainly all good innovations, but not unique to bass and not, I believe, even developed specifically [u]for[/u] the bass world before being adopted elsewhere. Is there anything truly unique in the bass world (at least at the time of its innovation) - apart from low notes?

[quote name='Truckstop' post='967098' date='Sep 24 2010, 08:03 PM']Actually a lot of JJ Cale might be well received.[/quote] We play JJ's version of 'Call Me The Breeze' (heck, it's HIS song!) and most people tell us they've never heard that Lynyrd Skynyrd song played that way before. Goes down well though. We've also played the Taken By Trees version of Sweet Child Of Mine. If we can't think of a cover with a twist, we try to find songs that most people will have heard, but probably not for a long time, e.g. Humble Pie's Natural Born Bugie, Beatles' One After 909, Ocean Colour Scene's Travellers Tune, Hotel Yorba, Oh Sweet Nuthin' - that sort of thing. We've never yet played Mustang Sally.

Has anyone been listening to "Key Matters" on R4 ? I caught the programme on C#, described as an obscure and rarely used key. Fair enough. It also talked about it's "flat twin" D-flat. Now, I had always assumed the two notes and scales were the same thing and the programme did indeed confirm that the scale notes are the same. But, the programme then seemed to suggest they have a completely different mood, based largely on how the notes "fit" in the hand (with reference to the piano) . . . . at which stage it all started to go over my head. It's on listen again for a few more days if anyone is interested. [url="http://www.bbc.co.uk/programmes/b00tt5j1#synopsis"]http://www.bbc.co.uk/programmes/b00tt5j1#synopsis[/url]

A fuse is deliberately designed to be a weak link in a power chain that will blow when too much current (according to the system design) flows. There are usually many fuses in any power chain. In this case, the 3.15A fuse in the amp, the 5A fuse in the plug, the 30A fuse in the consumer unit feeding the power circuit, the 60/100A fuse in the electricity meter, the ???A fuse in the local sub-station . . . etc etc. As the current consumption increases it's fairly obvious that the lowest rating fuse will be the one to blow first. Thus, with a 3.15A fuse in the amp, it doesn't really matter whether the plug fuse is 5A or 13A. It will have no effect on the amp fuse. The previous point about power-on current surges is the real issue, hence the need for a slow-blow fuse in the amp.

[quote name='tauzero' post='957083' date='Sep 15 2010, 12:13 PM']I remain completely unconvinced about the headroom explanation. The signal coming from a bass is of the order of 100-200mV p-p, which is considerably smaller than the supply voltage. It's like saying that you run less risk of banging your head if you jump up and down in the Vertical Assembly Building than if you jump up and down in St Paul's Cathedral.[/quote] A lovely analogy that could be applied to all manner of things, especially in the hi-fi and car worlds.

[quote name='Ou7shined' post='955061' date='Sep 13 2010, 05:19 PM']Basically you have to make sure that every bit of copper is earthed. You do this by connecting it to anything else that is metal. (which in theory is already earthed). It would be impractical to solder to your p/g (plus it would melt) so you can leave an overhang out the top of the cavity and make sure that the copper on the underside of you p/g touches it. Simples.[/quote] That will certainly work for a while but copper tarnishes very readily in the presence of air (copper + oxygen = copper oxide), which will affect conductivity between the cavilty and p/g foils. If the two foils are pressed very hard together then tarnishing may be quite slow but, even so, a length of wire soldered between the foils but long enough to allow the p/g to be removed might provide a more robust electrical connection.

[quote name='BigRedX' post='954380' date='Sep 13 2010, 09:16 AM']And while we're on the subject of on-board pre-amps maybe someone with a good knowledge of electronics (flyfisher?) can explain the attraction to me. I already have tone controls on the pre-amp in my rack, and I would have thought that it's much easier to build a good noise-free tone-shaping circuit when you don't have to worry about getting it small enough to fit into the control cavity of a bass and having to be powered by batteries?[/quote] Well, the only technical justification I can think of is that an on-board preamp will minimise the length of cable that a very small signal has to travel along, which will (theoretically) reduces the susceptibility to noise pick-up on the way to the main amp or rack-based preamp. But we all know that passive basses don't really suffer from inherent noise problems, or none that make them unacceptable otherwise there would be no passive basses, which is why I qualified the above with "theoretically" lest we descend into the realm of hi-fi voodoo and start discussing the merits of gold-plated mains plugs. I agree there are ergonomic and physical issues that are probably more important, which is exactly what I meant with my earlier comment that 'engineering is the art of the compromise'. There are lots of different ways of making a vibrating length of metal make a very loud noise and different people will inevitably choose different set-ups. Ultimately, if you like the tone that comes out of your rig then it will suit you, no matter how it has been created.

Assuming that the speaker connectors are all wired in parallel then the amp will 'see' 3 x 8ohm speakers = 2.66 ohms and the output power will be divided equally between all three cabs. A handy parallel resistor calculator can be found here: [url="http://www.1728.com/resistrs.htm"]http://www.1728.com/resistrs.htm[/url] And, as Merton has pointed out, if this is below the minimum impedance capability of the amp then beware!

Recently bought and collected two Mackie SRM450 powered speakers and stands. Took me about a week to arrange collection but Andy was very flexible and helpful throughout. The speakers have been well looked after and, of course, they work fine. Andy even threw in a couple of XLR leads. Good communication throughout the process making the deal easy and stress-free - exactly what anyone would wish for. Thanks Andy.

[quote name='BB2000' post='953667' date='Sep 12 2010, 04:12 PM']FYI coax cables that handle 10s of amperes at low frequencies are readily available. RG17,18 etc. can handle about 50KW, corresponding to a current rating of about 30A.[/quote] Well, yes, if you want a cable that's almost one inch in diameter.

[quote name='EdwardHimself' post='953629' date='Sep 12 2010, 03:37 PM']My advice would be to not worry yourself about it and get whichever you think sounds better whether it be 18, 9, 2, 27v whatever...[/quote] Spot on advice, which just about covers everything to do with music!

[quote name='munkonthehill' post='953534' date='Sep 12 2010, 01:34 PM']kinda wish I hadnt asked now [/quote] Apologies. I couldn't think of a simpler explanation. I guess the teaching profession is not for me.

Just to clear up a few things . . . Yes, in general, 18V will give more headroom than 9V - assuming those are the actual voltages used by the pre-amp circuit (see below). This may or may not be significant, depending on the pre-amp output signal voltage. There are many different ways of creating a 'plus-and-minus' power supply. Two 9v batteries make it very easy. A single battery makes it a little more complex, but certainly not impossible. Indeed, a single 9V battery could be made power a voltage converter circuit that provided an 18V (or even higher) voltage supply to the actual pre-amp circuit (search for 'charge pump voltage converters' for more info). In other words, extrapolating the "quality" of a pre-amp on the basis of how many batteries it uses is about as valid as using the rated power output of a speaker to determine how loud it will be. Also, consider the overall signal chain from pickup to speaker. If the guitar uses a powerful pre-amp then the main amp will have less work to do, assuming a constant volume from the rig. This might be a good or bad thing depending on the relative characteristics of the preamp and main amp. Engineering is the art of compromise and electronic engineering is no exception. But all the techy stuff pales into insignificance compared to the role of marketing and fashion in such things! After all, we all know that an amp that goes to 11 must better than the run-of the-mill amps that only got to 10, so 18 volts must also be better than 9.

[quote name='markstuk' post='952788' date='Sep 11 2010, 03:13 PM']Found the following over on BGRA - may have some perspective... "Bartolini: "NS2TMB-183", 18 Volts. Bass This is Bill Bartolini's latest and most refined design. It is quieter and more transparent than anything else out there (108 dB S/N, THD .003% @ 100Hz) and really sounds good. [b]To quote from the spec sheet "The (bipolar) +9V/ -9V system allows a completely DC coupled signal path. There are no capacitors to diminish in any way the low end punch, clarity and frequency response of the instrument". [/b]Bill has used wide bands that overlap slightly to avoid the honky sound of other midrange controls. The 250Hz mid could be useful as a cut option when recording." Now all we need to know are the benefits of a completely DC coupled signal path :-)[/quote] [quote name='flyfisher' post='950278' date='Sep 9 2010, 09:33 AM']I've always assumed it makes it easier to provide positive and negative voltage rails to the preamp circuitry, which allows the output signal to sit at 0volts and therefore not require a dc blocking capacitor. In this configuration, the batteries are connected as -9 , 0 , +9.[/quote] I rest my case. Think of it this way. The waveform from the pickup is an AC signal and it will alternate around zero volts (ground). An amplifier - either a bass power amp or a guitar pre-amp - must therefore amplify both the +V and -V portions of the waveform. It is not possible to amplify the -V portion of the waveform if there is no negative voltage rail to supply the amplified negative signal voltage. With an 18V system, the two 9volt batteries are connected together to give 18 volts across the voltage rails BUT the connection between the batteries will be connected to the ground of the power amp, which means that the pre-amp voltage rails are actually +9V and -9V with respect to ground. This configuration allows the AC pickup waveform to be correctly amplified on both its positive and negative cycles. Such a design allows the pre-amp to be DC-coupled to the power amp and eliminates the requirement for a DC-blocking capacitor, which is a good thing as far as frequency response is concerned (for the reasons described in the above quote). With a single 9V battery as a power supply, the pre-amp output can only swing between zero and +9v, so how can the -V portion of the pickup waveform be amplified? The answer is to apply a DC bias voltage to the input of the pre-amp so that the AC pickup waveform is centred around 4.5V instead of zero volts. The pre-amp can now amplify the AC waveform and the output will be a larger AC signal, but still centred around 4.5 volts. The bass amp input will be expecting an AC signal centred around zero volts (ground) so, to remove the 4.5V DC offset of the pre-amp output, the pre-amp is connected to the bass amp via a capacitor, which will only allow the AC signal to pass through it and will block the 4.5V DC voltage offset (hence the term 'blocking capacitor'). Unfortunately, this capacitor will have some effect on the AC waveform, as mentioned in the above quote, which may not be desirable. Hence the advantage of an 18V system, more accurately referred to as a -9V, zero, +9V system, which allows direct DC-coupling of the pre-amp output to the bass amp input. Apologies for the ramble but although simple in principle it's not easy to describe purely in words.

[quote name='ednaplate' post='952060' date='Sep 10 2010, 05:40 PM']How on earth can it be legal or ethical to knowingly import what are so obviously copy instruments?[/quote] Well, aside from the complexity on different cultures having different ethics, the basic answer to the question must be 'it isn't'. But, unfortunately, people break laws. Simple as that. T'was always so and t'will always be.

I'm guessing here, but I can't see it being an "output power" issue - that's not (normally) the purpose of a pre-amplifier. I've always assumed it makes it easier to provide positive and negative voltage rails to the preamp circuitry, which allows the output signal to sit at 0volts and therefore not require a dc blocking capacitor. In this configuration, the batteries are connected as -9 , 0 , +9. There are other ways of achieving +/- voltage rails from a single +V source, but it makes things more complicated and might introduce unwanted noise into the output signal. Could be wrong though.

I understand why a hand-wired or even hand-soldered amp will be expensive but that extra money is obviously going towards the production cost - it will have little or nothing to do with the actual functional 'quality' of the amp. That's a function of the actual circuit design, not the production method. I've always though it odd that "handmade" is generally regarded as "the best" when, in practice, it's a very bad way of ensuring repeatable quality and high tolerances in assembly.

I've often wondered why so-called 'top-end' gear is so highly priced. Do they really use more and/or highly priced components or is the high price just a reflection of the low production volumes? Or, more controversially perhaps, are they just adding sky-high margins because they can get away with it?

I can understand the annoyance of people not being entirely accurate in ads, but does anyone really buy gear based purely on an advert? Surely people already have in mind the stuff they want to acquire, based on detailed experience or having already read-up on things, so they already know pretty much all about the item in question. Or maybe not?

Indeed. Why would a screened cable 'impact on the frequencies' of a speaker signal but not on those of a guitar, mic or any other signal? Screening on lengths of cable used by typical bands will have no practical impact on audio frequencies.

What? Without even [u]one[/u] bum note? Er, leave it with me and I'll let you know . . . . .

The good thing about a passive bass is that you can't really break anything by experimenting (assuming you're OK with soldering and don't cook the components!). But, as hoiho has pointed out, the circuitry in question is just a fairly crude low-pass filter and changing the components will really only change the frequency where the roll-off begins. If you really want to experiment, you could try multi-pole filters to roll things off more quickly, but if you really get into detailed frquency shaping then you might as well keep the bass output as flat as possible and feed the signal into a graphic equaliser to really play around with the tone.

I'm gonna get a Tee-shirt printed with "I've been admonished by Tony Goggle". What an honour! Also, I should have known you'd need two heads to play that bass in his avatar.