Fixed - thanks! Aguilar DB750 - problems

[lozbass]

Hi, I recently picked-up a DB750 from the US after being very impressed with those I'd tried here. It wasn't cheap but almost new and in pristine condition (the orginal purchaser found it much too heavy...he's got a point). I had the circuit breaker (mains switch) replaced and mains re-wiring job done by a tech here in order that the unit can be used in the UK - something to bear in mind if you're thinking of importing a DB750, an additional cost of around £75.

Aguilar customer service is absolutely superb and the experience of working with them is akin to purchasing a custom bass (think Martin Petersen at the Gallery) - personal and personalised assistance at every step in the process of fitting the switch and re-wiring. However (and this is a BIG problem), the 750 won't fire-up - the circuit breaker trips every time I power on (sometimes even taking out the power in commercial premises). The problem (one that is common in the UK apparently) is recognised by Aguilar - their engineers fit a thermistor to try to get around it: the amp pulls an incredible amount of power on start up and this can trip out the mains and/or trigger the circuit breaker.

So...I have a major difficulty...a stunning amp that is simply unuseable. Has anybody out there had a similar experience with a DB750 and if so, any tips? Alternatively, does anybody know of a top class amp tech in the Manchester/NW area? I'm waiting for Aguilar to advise on a tech in the UK but it may be that they don't recommend UK servicing.

Edited August 18, 2007 by lozbass

[Kiwi]

Would a power conditioner help at all? How do touring professionals cope with the mains supply in different countries?

[Toasted]

Mine is a UK "factory" model (made in the US for the UK market). Mine does trip sometimes, but leaving it a few seconds and retrying normally sorts out the problem

[lozbass]

[quote name='Crazykiwi' post='43734' date='Aug 10 2007, 01:28 PM']Would a power conditioner help at all? How do touring professionals cope with the mains supply in different countries?[/quote]
Hi - thanks for this. I thought about a conditioner but was advised that given the pull of the 750 on power-up, there's little that could cope (at least at a reasonable price). I also thought about a step-down transformer but for the kind of power required, these are expensive (and heavy - maybe 25lbs on top of the weight of the 750 - yikes!) The point about touring is a good one (I have to admit I haven't done any proper touring for more than 15 years!). I suspect that anybody using a DB750 will need two switches/circuit breakers for US/Europe (or an industrial grade transformer and a crew to lug it all around). I think that some bigger bands carry around their own power these days. I'm also told that some users find that a DB750 can bring down the power in decent sized venues - it's a bit of a beast!

[lozbass]

[quote name='Toasted' post='43748' date='Aug 10 2007, 01:47 PM']Mine is a UK "factory" model (made in the US for the UK market). Mine does trip sometimes, but leaving it a few seconds and retrying normally sorts out the problem [/quote]
Again, thanks. I think the 'US made for UK market' models are simply fitted with the 7.5A ciruit breaker (and wired appropriately). I've tried mine in a number of settings now but it simply can't get past power-up. I even managed to take the power down in a biggish commercial building! One last try yesterday and I noticed a small and quick blue flash at the IEC mains socket when trying start-up in a dark room. I've a feeling there's a problem with the power input that's well beyond my knowledge/understanding. I just thought it was worth a try on BC - it could be something common or simple to resolve. I'll contact Aguilar again (truly excellent customer service) but I think my unit needs a professional eye cast over it. Thanks for the help and suggestions.

[chris_b]

[quote name='lozbass' post='43698' date='Aug 10 2007, 12:11 PM']I had the circuit breaker (mains switch) replaced and mains re-wiring job done by a tech here in order that the unit can be used in the UK -[/quote]
I would get a very qualified tech to check this work. Looks like your problem is in this area!!

[Toasted]

[quote name='lozbass' post='43758' date='Aug 10 2007, 01:59 PM']One last try yesterday and I noticed a small and quick blue flash at the IEC mains socket when trying start-up in a dark room.[/quote]

Mine does that, it's just the circuit breaker tripping

[Rich]

So what you're saying is that when you start it up, it'll trip out 13 amp cct. breakers? Ye gods, what on earth is the inrush current like?? Blimey. This is starting to sound like a basic design fault! Or am I being over-simplistic?

[Dood]

really? 13Ax240V thats ummm a draw of 3120W at power up right? blimey!

[Dood]

oh sorry, its a 7.5A circuit breaker. 7.5x240.. still 1800W though! gulp!

[lozbass]

Hi all, thanks for all the comments and help - truly appreciated! On the tech - absolutely right - the guy I used here is good but pro-audio is not his main field. This is big mains stuff and needs to be handled properly. On the 'blue flash' on tripping - again, thanks, this is reassuring (I don't have a problem with pyrotechnics but I do get a bit edgy when my amp appears to be the source) The design fault comment is probably not too far wide of the mark...maybe a design 'issue' though - Aguilar did try to address this with the inclusion of a thermistor (of particular importance in the UK) - it seems to work in most cases but my unit appears to have a different/more extreme problem. No criticism of the company though - the DB750 is a truly exceptional amp in conception, design and performance (in my opinion, of course) and the help from the tech department is simply first rate! On inrush current - yes, it's 7.5Ax240v - 1800 is what I thought (err...what I was told by the local tech) but Aguilar confirm that it can be much higher on start-up. If you've not seen inside a 750, it's worth it - the guts are incredible (and incredibly heavy). Thanks for the insights and help - I'm really impressed!

Edited August 10, 2007 by lozbass

[Stewart]

Have you tried disconnecting the speakers while powering-on?

Can't think of anything else temporary that would help...

[lozbass]

[quote name='Stewart' post='43830' date='Aug 10 2007, 04:22 PM']Have you tried disconnecting the speakers while powering-on?

Can't think of anything else temporary that would help...[/quote]
Hi and thanks - nice idea but yes, I've tried it both ways with the same (negative) result

[Marcus]

I have 2 mates with DB750's both use a Furman power conditioner and have no problems, I borrowed one for a gig once and used it without the Furman, wouldn't even switch on ?

Weird amp..... AWESOME SOUND !!!

I hope you get sorted with it......

[lozbass]

[quote name='Marcus' post='43841' date='Aug 10 2007, 04:36 PM']I have 2 mates with DB750's both use a Furman power conditioner and have no problems, I borrowed one for a gig once and used it without the Furman, wouldn't even switch on ?

Weird amp..... AWESOME SOUND !!!

I hope you get sorted with it......[/quote]
Hi Marcus, thanks - maybe a Furman's the way to go. I'll try to borrow one before investing and see if it makes a difference - I'll certainly report on the result. It's comforting to hear that it's not only my unit that seems to have the problem (though I empathise with those that are struggling). If you know, I'd appreciate advice on the Furman model that your friends are using. Thanks again.

[Oxblood]

Well, it's not just a problem for European users, it seems. Get a load (but not too much of a load - don't want to trip any circuit breakers) of this from across the pond:
[url="http://www.talkbass.com/forum/showthread.php?t=190882"]TalkBass thread[/url]

From what I'm reading, the DB750 certainly is "a truly exceptional amp in conception, design and performance" - but not in a good way! IMHO Aguilar's design staff need to be dragged into the village square and pelted with dung/rotten veg/concrete blocks over this. It's outrageous to market a piece of gear which you know damn well will be powered off ordinary domestic mains supplies, and yet not take this reality into account when designing the power supply stage. It really isn't difficult to design a power supply that has 'soft start' behaviour built in.

[lozbass]

[quote name='Oxblood' post='43868' date='Aug 10 2007, 05:10 PM']Well, it's not just a problem for European users, it seems. Get a load (but not too much of a load - don't want to trip any circuit breakers) of this from across the pond:
[url="http://www.talkbass.com/forum/showthread.php?t=190882"]TalkBass thread[/url]

From what I'm reading, the DB750 certainly is "a truly exceptional amp in conception, design and performance" - but not in a good way! IMHO Aguilar's design staff need to be dragged into the village square and pelted with dung/rotten veg/concrete blocks over this. It's outrageous to market a piece of gear which you know damn well will be powered off ordinary domestic mains supplies, and yet not take this reality into account when designing the power supply stage. It really isn't difficult to design a power supply that has 'soft start' behaviour built in. [/quote]
Hi and thanks - at least I had a laugh when I looked at the link and your suggestion re: the Aguilar people (who seem rather lovely by the way!) I do feel a bit more relaxed about the problem too - maybe my unit isn't peculiar/faulty. The power conditioner idea indicated above seems to have been succesful in some cases so I'll give this a try. On the 'soft start', I agree, maybe this should have been foreseen. I think Aguilar reacted pretty quickly however, and from what I hear, they were sending out/fitting the thermistor in the US for free on early models (I could be wrong here). The major problems seem to have occurred in the UK where our 240v system doesn't seem well-suited to working with the 750. I'll press-on with a Furman and keep all updated - thanks again.

[alexclaber]

I have to say that this need for a power conditioner REALLY bothers me! Do you realise why the power conditioner 'fixes' the problem? Because it doesn't have enough current capacity for the amp, so the current flow is choked at the power conditioner. I agree with Ken, Aguilar should really get some stick for this.

This way that power conditioners choke the mains supply is exactly why they should never be used for high power amps!

I think too often it is forgotten that we in Europe, particularly in the UK where we run on 240V rather than 220V (the claim that we're all now on 230V is simply achieved through changing the tolerances) have much better power for running high wattage amps than in the USA. This is particularly notable with lightweight high power amps where less power is buffered in the power supply capacitors.

Alex

[lozbass]

Hi Alex, thanks for the detailed response and the technical details - I'm really not expert where tech issues are concerned and appreciate the advice. I'm afraid I responded to your PM prior to reading the above and will re-appraise in the light of the details here. Given that one of the reasons for procurement of the 750 was headroom (and that this may be compromised by the conditioner if I understand correctly), then an alternative fix might be called for. I'll wait and see what I get from Aguilar and keep everybody informed. Thanks again (to all!)

[alexclaber]

That's interesting to note that a long extension lead solved the problem for one user. I bet if you use a high gauge (i.e. skinny) lead a good few yards long you'll get a similar affect in terms of voltage and current choking to using a power conditioner without giving Furman any money!

What is particularly bizarre is that this amp is noted for its comprehensive diagnostic testing at switch on causing power up to take quite a while. Did it not dawn on Aguilar that there is a world beyond the Eastern Seaboard and some of us even play bass?

Have you hassled Dave B on talkbass?

Alex

[Toasted]

It's a great amp. I love it to pieces and have no problem with mine

[Hamster]

[quote name='lozbass' post='43698' date='Aug 10 2007, 12:11 PM']does anybody know of a top class amp tech in the Manchester/NW area?[/quote]

Have you tried Dave Lunt in Stockport 0161 432 9698 ?

Hamster

[lozbass]

[quote name='alexclaber' post='43967' date='Aug 10 2007, 08:01 PM']That's interesting to note that a long extension lead solved the problem for one user. I bet if you use a high gauge (i.e. skinny) lead a good few yards long you'll get a similar affect in terms of voltage and current choking to using a power conditioner without giving Furman any money!

What is particularly bizarre is that this amp is noted for its comprehensive diagnostic testing at switch on causing power up to take quite a while. Did it not dawn on Aguilar that there is a world beyond the Eastern Seaboard and some of us even play bass?

Have you hassled Dave B on talkbass?

Alex[/quote]
Hi Alex, thanks again. I suspect your right, a long skinny mains lead probably does the job of the Furman at greatly reduced cost! Sub-optimal though, as you've suggested earlier - the 750 should simply work. Haha - I'd love to experience that much maligned 45 second wait with my own unit. All I have at the moment is an attractive doorstop (if you think industrial-style electronics can be attractive).

You know, I often wonder about the US. I'm not a regular visitor though some of my colleagues are American and others travel regularly. I do get reports of sometimes narrow/domestic assumptions, attitudes and worldviews and this may be reflected in design practice (I'm not in any way criticising our American cousins here - I suspect many of us here in the UK could take a long hard look at ourselves!)

I haven't hassled Dave on Talkbass - I've kept contact direct so far (but once this issue gets resolved, it may be useful to encourage Aguilar to go more public). Thanks again for all the inputs!

[lozbass]

[quote name='Toasted' post='44037' date='Aug 10 2007, 11:12 PM']It's a great amp. I love it to pieces and have no problem with mine [/quote]
You're absolutely right! They are lovely amps (I've been knocked out with those I've used - I wouldn't have spent the money if I'd not been impressed). I'm looking forward to mine powering-up. Thanks for the info on the 'blue flash' - I thought this was a bad sign but it's good to hear others have seen/experienced it.

[lozbass]

[quote name='Hamster' post='44074' date='Aug 11 2007, 12:48 AM']Have you tried Dave Lunt in Stockport 0161 432 9698 ?

Hamster[/quote]
Hi Hamster, thanks very much for this - Dave was going to be my first call if I couldn't resolve the problem with inputs from BC members. I didn't have his number previously - I think Dave designed/built the hand-made pre-amp that I had installed (by Ted Lee!) in a Gibson Ripper in 1981!