AlanP2008

[quote name='elliswasp' post='745802' date='Feb 15 2010, 01:11 PM']its actually very missleading when you think about it they really should find a better way of measuring out volume a db rating or something wattage is really bad aspecially when you get peak power rms music power pmpo and all the others that are massivly over rated to make an amp sound better than it it. Markus[/quote] I don't reallly think that Watts are a problem - they are measurements, etc... and they are what they are. It is *expectations* that are potentially the problem...

[quote name='Bassmouseman' post='745832' date='Feb 15 2010, 01:38 PM']I have a Ashdown MAG 600 and set it so my loudest notes just go into the red. I have spoken to a number of people about the Ashdown meter and most agree that its not very accurate! and its best to not rely on it too much.[/quote] I think "don't worry about it too much" is probably the advice... Get it somewhere around mid-scale - just touching the red if you like, and that should be just fine.... It is a VU meter (and there is no indication of how it is calibrated with respect to headroom etc..) To monitor clipping, a peak meter would be the appropriate device, whereas the VU is an averaging indicator. Therefore, just use it as an indication that there is a decent signal present - I think that's about all you can derive from it... Re: inputs... On the MAG preamp, the high sensitivity input has a very high input impedance - a fet and a resistor to ground of 3M9. The low sensitivity (active) input has a 6dB pad, but more significantly perhaps, a much lower input impedance of 20k. The ABM 500 willl probably be pretty similar.

[quote name='elliswasp' post='745756' date='Feb 15 2010, 12:30 PM']Thanks guy thats pretty much what i figured only reason i was asking is because the mag 300 i had first seemed so underpowered and i could figure out why the cabs i have now have a combined rating of 450w so 600 or should i say 575 should be fine i just think that running 300 threw a system requiring 450w+ was the problem im hoping that this amp will have the guts to cope with it all now. Markus[/quote] ... well, the proof of the pudding etc. etc.... But you probably have *exactly* the same speaker setup now as you had with the combo... although you now have a 575W amp, rather than a 300W amp... However, there is probably less difference than you imagine between 300W and 575W in simple loudness terms.... Still - try it and see... Alan

[quote name='Mr. Foxen' post='744891' date='Feb 14 2010, 03:48 PM']Bear in mind it will make the cab wierd, in that no-one has 2 ohm cabs. Make sure you tippex over the 8 ohm bit on the back. People blindly believe that even with a meter showing otherwise. Get a resistance meter to check, it will probably come up not exactly 2.[/quote] Agree... EXCEPT that the diagram bottom right is labelled wrongly - they are actually shown series-parallel there, and if you use 4x 8ohm speakers like that, it will result in an 8 ohm cab (and it is probably how the 4x10 cab is currently wirted)... If they were really all actually in series, the result would be 32 ohms... Wiring as per bottom left is full parallel, and will get you 2ohms... And correct... DON'T mismatch the output of a valve amp. If the load impedance is higher than that set on the amp, it can result in high voltages in the output stage, potentially causing flash-over of output valves and/or output transformer. If you really must mis-match it it, it is better to have a lower impedance load than that set on the amp (although this isn't exactly good either, and can cause over-dissipation in the output valves, shortening their life (albeit likely not catastrophically)) Alan

[quote name='elliswasp' post='745702' date='Feb 15 2010, 11:46 AM']is there any diffeence in hooking both cabs up to an output each and hooking one up and the running a speaker cable from one to the next would the amp still be running at 4 Ohms as both my cabs are currently 8 Ohm cabs[/quote] No difference - You got it... [quote]also does anyone know anything about these amps as i dont seem to be able to find much about them other than a thread on here wich seems to be fairly good and two others on another forum slateing them to hell.[/quote] I have one of (this family) of amps... They're fine.... The labelling of the buttons under the eq is non-intuitive, and I never use the sub-bass stuff. Start off with the eq all set to the middle, turn up the input gain until you're getting mid-scale on the meter, and go for it... Alan

[quote name='AlanP2008' post='744727' date='Feb 14 2010, 01:00 PM']That is an interesting point. Is there evidence? Or is this just a gut feeling? (In which case, perhaps we shoud be measuring your gut!)[/quote] Ok, sorry - that was far too cheeky! I was previously pulled up myself for suggesting that Xmax was a bit arbitrary.... It was pointed out to me that the accepted method is the point of 10% distortion (I am assuming that there is a bit more to it than that -- frequency and measuring conditions etc., otherwise it *is* a bit arbitrary). I think it was suggested at the time that there were also older, less standardised methods of producing such a figure - I'm not sure why anyone would wish to stick with such a strategy when it is useless as a means of comparison. Xlim being the point you can expect permanent damage... Again, there is not too much point a manufacturer being "ambitious" about that (although not publishing a figure at all seems a bit too coy for words...) It does rather seem that we live in a less-than-ideal world though... Alan

[quote name='stevie' post='744704' date='Feb 14 2010, 12:38 PM']Alan, you have to be careful here because there are different ways of measuring xmax (a bit like measuring car fuel consumption). Eminence uses the most optimistic method, whilst Celestion uses the most conservative. The difference can sometimes be as much as 100 percent. The 4mm xmax given by Celestion is probably the equivalent of around 6mm in Eminence spec sheets (my gut feeling). Other speaker manufacturers publish different figures for xmax so that you can do a realistic comparison (see the B&C website, for example) but Celestion and Eminence only publish one figure which is not directly comparable.[/quote] That is an interesting point. Is there evidence? Or is this just a gut feeling? (In which case, perhaps we shoud be measuring your gut!) Alan

[quote name='Mr. Foxen' post='743998' date='Feb 13 2010, 02:04 PM']If they want a sealed cab, stick them in a sealed cab, they just won't be very bassy. Good for a roaring valve amp though. If you want the ported option, go for the kappalite 3015 (nonLF). Or for the Doom option, build the Celestions into a sealed cab, and make another cab with a Kappalite 3015LF for epic bottom, and run a SS power amp into that, and rag a power amp into the sealed 2x15. This is pretty much my plan.[/quote] As far as I can see from the spec sheet, the most significant differences between the 3015 and the 3015LF are: i) 3015 Xmax=5.9mm, Xlim=11mm, 3015LF Xmax=9.6mm, Xlim=17mm (the LF will take quite a lot more power at low frequencies before it cracks up) ii) 3015 sensitivity= 100.8, 3015LF sensitivity=98.4. (The LF is *good*, but the 3015 is *excellent*) The other point one might spot is that the 3015's on-axis response goes up higher, but as I have seen often pointed out here, the off-axis response (which is much more significant) is dominated by the fact that both of these are 15" speakers, and both will both need some kind of mid-range driver to give them any kind of off-axis top-end (ie. anything much above 1000Hz) at all (but your taste and/or style might not need that). winisd suggests that the LF will give a bit more bass extension than the non-LF.... but in the end, you pays yer money and you takes yer choice - they both seem to be excellent speakers for bass to me (as are the 3012s). Alan

[quote name='RIM Basses' post='743600' date='Feb 12 2010, 11:44 PM']They are Bn15 400x neo drivers, i dont understand the winisd website, im old school. i might just build the cab[/quote] Old school eh? And spurn the use of tools like winisd? I guess you will be carving the panels for your cabs with your bare hands and a stone axe? Sorry, I'm being facetious... it is an unattractive trait... But it is very worthwhile understanding *free* stuff like winisd, and study speaker characteristics a little... In particular, the unique challenge in getting a decent bass response in a sealed box is to build a large enough box (in fact you will need an absolutely gigantic box....) The challenge in a tuned or sealed enclosure (assuming the box is big enough) is in choosing a speaker that will both give you the response you need, and from a practical standpoint, not destroy itself when trying to get decent power levels for the lowest notes - 40Hz ish for low E, 31Hz is for low B... The key parameters in that are the Xmax and Xlim parameters... Xmax being the maximum [u]design[/u] speaker excursion at the particular power and frequency you are considering, and Xlim being the point at which the voice coil is likely to sustain irreparable damage... The spec sheet for the Celestion Neo speakers don't actually state Xlim, but the value for Xmax of all of those I have looked at is [u]much too low[/u] for credible use in a bass cab... (and yes, I know some well rated cab manufacturers use them...) The Bn15 400x has a stated Xmax of 4mm. That compares very poorly with most of the best (for example) Eminence bass speakers ... The Kappalite 3015 LF has an Xmax of 9.6mm, and an Xlim of 17mm, which is really excellent... winisd is able to show you the frequency response of your proposed cab design, determine the porting, and see the real effect of the mechanical limits at various power levels, which should allow you to understand how robust (or fragile) will be your investment in your bass speakers... ... or you could just build them and see - but the likelyhood of being happy with the result are (imho) pretty slim... Alan

[quote name='allighatt0r' post='741338' date='Feb 10 2010, 07:20 PM']But if the cabs are running in parallel, does that not mean that they are both receiving 300 watts?[/quote] No. If the amp is delivering a total of 300W, and there are two cabs of equal impedance, then they will share the total output power...

[quote name='ThomBassmonkey' post='743829' date='Feb 13 2010, 11:16 AM']If both outputs have 8ohms next to them, is it possible that it means you can't just run a single 4ohm cab from it? The only way to achieve 4 ohms is to have 2 8ohm cabs? I'm not an expert anyway so I might be wrong. Any way, it should work out, as has been said, 2 outputs from 240W doesn't mean 120W a side, they're both in the same channel so it'll actually go up to the 350W for both.[/quote] The first part of your posting was correct, but the above is incorrect. Two outputs from a mono amp, each marked 8 ohms, is a reasonable marking but not too helpful (and potentially misleading if you don't understand about speaker impedance). Yes, either one or two 8 ohm cabs can be plugged in, and that would probably be the normal case (and two x 8ohms in parallel gives 4 ohms). However, a single 4 ohm cab may also be used, although that isn't explicitly stated. From the ratings, with an 8 ohm load the amp will provide 240W, with a 4 ohm load it will deliver 350W total, and if the 4 ohm load consists of two 8 ohm cabinets, then those cabinets will share that 350W - ie. 175W per cab... ...And you might also want to ponder on the idea that in an 8 ohm cab containing 4 separate drivers, each of those drivers will be sharing the total that the cab is receiving... Hope this helps. Alan

[quote name='Jateca' post='743111' date='Feb 12 2010, 02:16 PM']How so?[/quote] The basic problem is that the cab is tuned for two speakers.... With just one speaker, the physical excursion of the cone will be waaaaaay more than normal, and could give rise to physical damage...

[quote name='bumnote' post='742962' date='Feb 12 2010, 12:07 PM']I cant find the original article but Steve Rabe of SWR wrote an article where he said the best way to check if a speaker is working correctly is to connect a 9 v pp3 across a lead and check that the cone moves. It is also usefull for checking the speaker are wired in phase I have never done it so i cant confirm this is correct[/quote] It is totally true... and if both speakers don't move the same direction at the same time, and the same amount, then you have a problem...

[quote name='Jateca' post='742022' date='Feb 11 2010, 01:05 PM']Unfortunately, having spoken to the GK contact in the UK, my speaker is out of warranty (I've had it for about 3 years) so they won't replace it and they do not offer a re-cone kit as far as I'm aware. Do you think there's any way I could remove the dust cap from the cone without causing irreperable damage? The only thing I can think of doing is getting at the wires that go to the voice coil and checking them.[/quote] IIRC (from re-coning experience in a previous life...) the dust-cap is simply glued in at the end of a re-coning operation - it is attached to the cone by a circle of adhesive.... I reckon the only way you could realistically go is to cut the centre out of the dust-cap using a scalpel and/or small pair of scissors, and trim it back as close to the cone as possible. It might or might not be possible to pick or dissolve the glue off the cone, but I would say the chances of damaging the cone are fairly high... Once the dustcap is gone, you should be able to see the lead wires to the coil - again, I think the chance of the open-circuit being right there is pretty slim, but you don't have too much to loose I think... On the odd chance you do fix something, you could probably get a gash dust-cap from someone like Wembley - as long as it is larger than the original, it should it's job... Alternatively, if you could get to Wembley (or some other re-coner) there is every chance that they could work out who actually made it, and source a re-cone kit for it. I seriously doubt that GK actually made that speaker themselves, I'm pretty sure the economies of scale are such that it wouldn't be economically feasible. On another point - don't run that remaining (good) speaker at any volume all by itself in that cab (even if you block up the hole), or else you'll be looking for two replacements... Alan

A bit kludgy perhaps, but practical... Do you have some microphone cable with a braided screen - the old-fashioned type that often has cotton or paper padding along with the wires (not this modern stuff with conductive plastic, or fail and a drain wire...) ... if so, you can usually strip the insulation off of, and the cores out of a couple of foot of it, concertina it up, and thread that over the wiring as a screen (don't forget to ground it). Alternatively, you might be able to seek & find some such screening braid as a wireman's product... Or wrap it in a strip, or strips of aluminium foil (if you do this, you could include a drain wire in the bundle, and ground that). You have otions... Alan

[quote name='Mr. Foxen' post='737616' date='Feb 6 2010, 09:02 PM']Think cause its a woofer driver, you get weird in the mids and rolls off loads as it goes higher, needs to be paired with a midrange speaker plus crossover.[/quote] Yes, it does indeed. However, it appears to do a really superior job at the bottom end, which is where the real challenge is...

[quote name='Protium' post='737416' date='Feb 6 2010, 05:20 PM']No one mentioned an *output* transformer.[/quote] I was responding to... [quote]Is there an output for an extension cab on the back? - My money's on a popped transformer.[/quote] ... which seems to associate "output" with "transformer"... my mistake if that wasn't the intention... If the mains transformer has gone, it won't be quiet - it'll be silent... Alan (In fact I have a MAG 400 head here with a "popped" transformer - it's blowing mains fuses, although if it had failed open rather than short, the fuses would be ok, but it would be just as dead...)

I've been looking at 12" speakers for bass cabs, and if you want a Neo, the Kapplite 3012LF looks like a good bet. One problem with many 12's for bass is that they are often excursion limited at very low freqs. Low E and Low B strings... You can't use them anywhere near their max rated power... The 3012LF has an Xmax of 9.1mm (comparatively large) and Xlim of 14.5mm - both very good for a 12. Also, it has a decent sensitivity of 95.5dB, whereas many of the other LF speakers have rather lower sensitivity... Better though, is the 3015LF, with sensitivity of almost 100dB - Loud! (but that's a 15). Play with it in WinISD, and see what you think.

[quote name='redstriper' post='736545' date='Feb 5 2010, 07:00 PM']I just watched the youtube demo of the redeemer and it seems to do the opposite of what I want. It retains the tone with the volume on full, when you decrease the volume. I want the muted tone with the volume turned down to be retained with the volume on full. Unless I'm missing something............... ?[/quote] The tone pot rolls away the top as you turn it down. When full up, you (almost) get the full tonal range of the pup... On the face of it, the tone pot is the thing that you would use to get the tone you want, rather than the volume pot. In all probability though, only the highest frequencies are being affected by the tone pot, and those being rolled off quite severely when it is pulled right down. Possibly, the sound you like is with the response rolling off starting off at a lower frequency, but rolling away fairly slowly. If that is the case, it might be that a larger value of tone cap would do it for you - you'd need to find someone who could fiddle with that with you. Some basses have a switch that selects different cap values - I can't remember what the thing is called - I think the old EB3 was like that... Alan

[quote name='Protium' post='736451' date='Feb 5 2010, 05:29 PM']+1[/quote] ... being a solid-state amp, there is *no* output transformer. One of the best things to do immediately (once to are sure its not the speakers) is to take a lead from the line out or effects send to the effects return of another amp. If there is a good signal there, then the problem is certainly in the power amp. Then if you are feeling brave, you could take the amp out of the cab - 4 plastic plugs on the top of the cab, a screw underneath each one... On the power amp pcb there are two big (1.25") DC fuses - probably 10AT (T=slow-blow). Check whether they are blown or not... If blown, then it is certainly a problem with the power amp. If not blown, it might or might not be the power amp, but there is little else left now. There is an output relay that might have failed, some thermal over-temp switches that might have failed..... and a few other things. Btw - a simple message to ashdown via their site will get you the schematics immediately - but that's only useful if you know what to do with them... I guess they would take it in for repair... they'd be sure to sort it.... ... or you could aways use magic, Harry...

[quote name='redstriper' post='736352' date='Feb 5 2010, 04:05 PM']So is this a flaw with my basses, which could be fixed with some electrical tinkering? Or is it a feature of all jazz bass pups ? My basses are a 1963 Fender jazz and a modern Tanglewood Corvette copy, both with original wiring .[/quote] It is not necessarily a flaw - it is certainly a "characteristic", you could even call it a "feature"... It can be changed somewhat by putting a cap across from the "hot" terminal of the volume pot to the wiper, but the value wold be a matter of experiment, and you might well find that as you rolled the volume down past a certain point it actually ended up with all toppiness and no bass... .... you might try to live with it?

[quote name='Ancient Mariner' post='735636' date='Feb 4 2010, 11:15 PM']I'll believe you, but I also can't explain why some guitars & basses have this flaw and some do not.[/quote] Factors: Pickup type (s/c h/, impedance and inductance Pot value Pot wiring configuration (usually wired differently when there are two vol controls) Presence or absence of a "treble bleed capacitor" Tone pot and cap values (usually always in circuit unless "no load" pot used) Any other unusual factors in the guitar or bass (clever switching, coil splits etc.) Length and capacitance/metre of the guitar cable. Characteristics of the amp input. Stuff I've probably forgotten... Alan

[quote name='Krysbass' post='735008' date='Feb 4 2010, 01:26 PM']I used conductive silver paint, sold by Maplin (you can order online) to screen the electronics cavity on a cheap Stagg fretless I was upgrading. I seem to remember it cost about £7 for a small pot, which was just enough to screen 1 bass. I used foil too, to line the inside of the plastic electronics cover on the back of the bass. This combination works perfectly. Hope this helps.[/quote] This stuff... [url="http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=370261873585&ssPageName=STRK:MEWAX:IT"]http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...e=STRK:MEWAX:IT[/url] is cheap, quicker to apply than layers of conductive paint, easily soldered, and very effective...

[quote name='Ancient Mariner' post='734847' date='Feb 4 2010, 10:42 AM']<snip> which side of the tone pot relative to the volume control the tone cap sits.[/quote] That in itself cannot make any difference. If a pot and a cap were in series, and mounted in a "black box", there would be no way (by measuring electical characteristics from outside the box) to determine which one was first...