obbm

[quote name='bassjamm' post='230160' date='Jun 30 2008, 11:06 PM']Right...just had a look at what we're talking about!!! If i needed a transformer, what wattage allowance would i need? Would i be correct in thinking the following? - Using my SVT-II as an example, it's a 300 watt amp. So lets say it was from the US running at the 110 Volts they use, and i want to use it here in the UK...would i need a 300 watt transformer, or would be ok with just any transformer that converted the 240 volt power form the plug into a 110 volt source for the amp? Or...would i need something that can take a lot more than the 300 watts? Thanks J[/quote] Your SVT is 300-watts output of audio signal. It will also output some heat as amplifiers are not 100% efficient. The input power is therefore greater than the quoted output power The manual says the consumption is 460VA which is near enough an output of 500-watts. So input power required is 500-watts. This is the same whether running on 110-volts or 240-volts. Power = volts x amps. In the eample of the SVT you should be looking for a 240-volt to 110-volt step-down transformer with 500-watt capacity. I hope I haven't confused you.

[quote name='silverfoxnik' post='228962' date='Jun 29 2008, 12:26 PM']BUMP!!! As for price, thanks to Merton's amazing nefotiating skills I think we have the 2 rooms for £100! So how about some thoughts as to what would be a fair cost? If we have 30 people on the day at £50 then that will cover it nicely, but if we want to raise a bit more for charity (including Basschat), then maybe £7.50 each? Maybe OBBM can remember what we all paid last year - wasn't it £10 per head Dave? - and we could use that as our yardstick..[/quote] It was £10 per person. The venue was £100. 23 attendees. £130 to charity.

Deputised in a former band as their regular chap wasn't going to turn down the opportunity to play with the Jackie Lynton Band along with John Coghlan (Quo's original drummer). It gave me an opportunity to get out and play again with the Micky Kemp Band who now have the amazing Darrell Bath (ex-Ian Hunter, among many) on guitar. He's like a cross between Keith Richards and Wilco Johnson) and knows where he fits in the mix. Interestingly he plays with his amp facing backwards so he can turn it up without deafening the audience. It was a private party in a 100-year old village hall, so great accoustics, and an ideal opportunity to try out the Orangtino rig. All I can say is wonderful. As things warmed up the dance floor got heaving but unfortunately the conditions of the music license in the hall meant we had to stop far too early. Back to how gigging should be though. Fun.

[quote name='Happy Jack' post='228808' date='Jun 29 2008, 12:19 AM']Yes Dave, I've got both. A 500/7 (the original Verithin) in cherry red, and a 500/6 (the replacement for the 500/7 - don't ask about the numbering) in that strange blackcurrant burst that was popular towards the end of the 60's. I assume it's the 500/7 that you're after?[/quote] I'd be very interested to try the 500/7 please.

[quote name='Happy Jack' post='228479' date='Jun 28 2008, 10:51 AM']In my diary - anyone fancy a selection of vintage Hofners?[/quote] Have you got a Verithin bass? I always fancied one of those.

I'm in. This time I'll bring a couple of basses and perhaps the Orangtino if anyone is interested.

[quote name='phil_the_bassist' post='228457' date='Jun 28 2008, 10:01 AM']Aah, fair enough! I think most of my problem is the my completely, utterly and totally mortifying fear of dying in stage (battery-wise, rather than performance wise!) as it's happened once and I felt like a total pr**k! I'm guessing a small switch between the battery and circuitry would do, just to stop any unnecessary power drainage? I'm a complete beginner when it comes to electrics, hence the stupid questions![/quote] I've used an SR5 for 10 years and never had a battery problem. Always get a good quality battery like a high-capacity Duracell. Three simple tips if you are worried. 1. Always unplug your bass when not using it. 2. Check your battery voltage occasionally with a voltmeter. 2. Carry a spare battery with you. After all it only takes 30-seconds to change.

[quote name='phil_the_bassist' post='228359' date='Jun 27 2008, 11:09 PM']I've got a 2006 SR5, and want to do the same thing, purely for the sake of my wallet *WHY THE HELL ARE 9v BATTERIES SO DAMN EXPENSIVE!!!!* ahem! Does anyone have any ideas/wiring diagrams about how this could be achieved? I don't wanna go crazy and bypass the pre-amp totally, but a switch to give me passive tone and to stop me draining the battery'd be worth its weight![/quote] Firstly I don't know why you are having a problem is with batteries. Mine last for months and months. Secondly it is very difficult to achieve what you want to do on a later SR5 because as previously mentioned the pre-amp uses a balanced input in single coil and series mode with the join of the two coils grounded. You could possibly do it in parallel mode as this only uses a single input to the pre-amp. You would of course be without any controls as the volume control is a part of the pre-amp.

[quote name='dub' post='227520' date='Jun 26 2008, 05:11 PM']My pickup has no dummy coil. I disconnected the input and output of the pre-amp and connected the selector switch to the volume.[/quote] You've answered my question. Yours must be a pre-91 SR5 which has much simpler coil switching. You can't do what you've done on the later version and retain coil switching as the pre-amp has a balanced input.

[quote name='dub' post='227457' date='Jun 26 2008, 03:40 PM']I just bypassed the musicman pre-amp to see what it would sound like before installing a switch. The surprising thing was more output with no pre-amp and no hiss at all. The pre-amp set flat just seems to add loads of top end and hiss, so I'm just going to leave it without the pre-amp connected. I'll have no onboard eq but the output is louder, quieter, less trebly and I won't need any batteries.[/quote] Just out of interest which wire did you intercept and what coil mode is it in?

Are they captive or IEC mains leads? Have you tried different ones? Check for an Earth/Neutral miswire in the plugs if they are not the moulded type.

[quote name='bassjamm' post='226444' date='Jun 25 2008, 08:59 AM']Hmm...just read through that but didn't see that bit. I saw a bit about mixing ohms but it didn't make any sense. I read there that you shouldn't exceed the amps load though as it can cause it to short out. Surely if i were to use the 2.67 overall load of the 2 cabs, on the 4 ohm switch, then i would in effect be putting too much of a load on the amp when in that mode...? But not so if i used the 2 ohm switch?[/quote] It's not about exceeding loads as with a solid state amp. You mustn't think about a valve amp in the same way as a solid-state amp. In a valve amp the output transformer is there to provide a virtual load for the output valves. There are separate output taps so whether you use, in your case, 2-ohm or 4-ohm speakers, the load on the output valve anodes remains the same and that the amp is operating on the optimum part of its load-line. If you put a mismatch on then you are altering the performance characteristics. This phenomenon does not occur in solid-state amps. What he is saying is that if you set your tap to 4-ohms and use a speaker of impedance of equal to or less than that then it should be OK. If you are unsure about this the contact Ampeg technical Support and get the word from them. They designed it so they should be able to advise you according. The other alternative is to get another speaker 4-ohm or 8-ohm cab and do it properly.

[quote name='niceguyhomer' post='226408' date='Jun 25 2008, 08:09 AM']Any progress/news with the modification Dave?[/quote] Not yet Al. The body is still away being fettled.

According to [url="http://www.geofex.com/tubeampfaq/taffram.htm"]this[/url] it would appear that it would be safer using the 4-ohm tap. [quote]The thing you CAN do to hurt a tube output transformer is to put too high an ohmage load on it. If you open the outputs, the energy that gets stored in the magnetic core has nowhere to go if there is a sudden discontinuity in the drive, and acts like a discharging inductor. This can generate voltage spikes that can punch through the insulation inside the transformer and short the windings. I would not go above double the rated load on any tap. And NEVER open circuit the output of a tube amp - it can fry the transformer in a couple of ways. [i]It's almost never low impedance that kills an OT, it's too high an impedance. [/i] The power tubes simply refuse to put out all that much more current with a lower-impedance load, so death by overheating with a too-low load is all but impossible - not totally out of the question but extremely unlikely. The power tubes simply get into a loading range where their output power goes down from the mismatched load. At 2:1 lower-than-matched load is not unreasonable at all. If you do too high a load, the power tubes still limit what they put out, but a second order effect becomes important. There is magnetic leakage from primary to secondary and between both half-primaries to each other. When the current in the primary is driven to be discontinuous, you get inductive kickback from the leakage inductances in the form of a voltage spike. This voltage spike can punch through insulation or flash over sockets, and the spike is sitting on top of B+, so it's got a head start for a flashover to ground. If the punchthrough was one time, it wouldn't be a problem, but the burning residues inside the transformer make punchthrough easier at the same point on the next cycle, and eventually erode the insulation to make a conductive path between layers. The sound goes south, and with an intermittent short you can get a permanent short, or the wire can burn though to give you an open there, and now you have a dead transformer. So how much loading is too high? For a well designed (equals interleaved, tightly coupled, low leakage inductances, like a fine, high quality hifi) OT, you can easily withstand a 2:1 mismatch high. For a poorly designed (high leakage, poor coupling, not well insulated or potted) transformer, 2:1 may well be marginal. Worse, if you have an intermittent contact in the path to the speaker, you will introduce transients that are sharper and hence cause higher voltages. In that light, the speaker impedance selector switch could kill OT's if two ways - if it's a break befor make, the transients cause punch through; if it's a make before break, the OT is intermittently shorted and the higher currents cause burns on the switch that eventually make it into a break before make. Turning the speaker impedance selector with an amp running is something I would not chance, not once. For why Marshalls are extra sensitive, could be the transformer design, could be that selector switch. I personally would not worry too much about a 2:1 mismatch too low, but I might not do a mismatch high on Marshalls with the observed data that they are not all that sturdy under that load.[/quote]

I've gone back heavyish. A single cab that is the same height and depth, but slightly wider than the two 1x12s, but heavier and an amp head that weighs as much as my original 6U rack system. Overall the new set-up is physically only slightly bigger but the tone is huge.

I'm sure I said this a long time ago but bolt the old and the new guards together and using the old one as a template gently open up the hole in the new to match the old one.

File away, carefully.

No need to go down to 2-ohms if you get a secondary power amp. You can run one set of 4-ohm spekers from the Eden. Take a line out to the secondary power amp, and if it's a 2-channel device then you can run a set of 4-ohm speakers from each channel. 6 x 8-ohm cabs in total. Is that enough air movement?

[quote name='Bill Fitzmaurice' post='225034' date='Jun 23 2008, 02:09 PM']The technical acronym for this proceedure is RTFM. [/quote] Indeed it is but I was just being polite and diplomatic.

[quote name='phil_the_bassist' post='224864' date='Jun 23 2008, 11:33 AM']ok ok ok...even tho (several years ago) I did my physics A-level I still have a nightmare getting my head around this whole wattage/ohms thing! Broken down: Low ohms = more watts get through = louder. I get that bit, maybe not the why or how, but I get that it happens. Now, the big question...I've got a Hartke HA5500 (so that's max output 500w@4ohms but it's currently running 250w@8ohms) and I've got a VX215 cab thats rated upto 500w@4ohms. So, they're matched, it should all work OK but on the speaker outputs on my head it's saying '8ohms'. Does anyone know how I can get the full 500w@4ohms? Will I need to send it back to the factory, or is there a secret switch I need to flick? Any Ideas?[/quote] I strongly recommend that you read paragraph 2 on page 8 of the Hartke 5500 User Manual.

[quote name='karlbbb' post='223859' date='Jun 21 2008, 09:53 PM']Do they not make 12-ohm speakers? 12-ohm speakers, 3 in parallel = 4 ohms![/quote] Nope! 4, 8, 16 or 32 ohms. 3 x 16-ohms in parallel gives 5.3-ohms which is the impedance of the Eplifani UL310. Interestingly the SWR Goliath Senior 6 x 10 is also 5.3-ohms. As long as you have a powerful enough amp it makes f***-all difference having 5.3-ohms.

I had a similar problem with some pedals a few years ago. The problem is that some 9-volt power supplies have a well regulated output and some don't. Some pedals have on-board regulation and some don't. If you use a badly regulated psu with a badly regulated pedal you get hum. You don't say which Wall-wart you are using.

[quote name='ben_eat_pie' post='223270' date='Jun 20 2008, 09:45 PM']just wondering if anyone knows or can explain why there are no 3/10 cabs in producion (that i know of anyway), i'd like of with a horn...! might be something to do with wiring and impedance... i havn't a clue... that was a guess! ben[/quote] For starters I suggest that you explore the Epifani range. I think you might find a 310 there. In fact oldhorsemurphy has an Epi UL310 for sale on this very forum. Impedance is generally 5.3 ohms i.e. 3 16-ohm speakers in parallel, but you treat it as 4-ohms.