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Post by speedysteve on May 3, 2015 19:14:25 GMT
After the test session today with Martin's Chord on mid bass and John's Behringer Inuke on sub tapped horns I need a change!
I use Topping TP-60 chip amps - They have enough power, but the damping and control on 650w 15" drivers was always in question...
I'm sorted on the sub channel - Can't see how I can better the Berhringer Inuke 1000 on my ultra efficient tapped horns - It sounded sooooo good.
Plus as £145 for the non DSP version, price is great!
Now, I can't afford a Chord (£9000mrp), but would like to explore a beefier silicon amp that can excel in the 90Hz to 300Hz frequency range!
The driver it has to work with is the venerable JBL 2220. Very low Qts and high efficiency (in horn it's 110dB / W).
I know there are probably no amps specialising in that freq range (would be nice though as making an amp perfectly linear 20-20KHz and the associated cost is not needed here!).
What would recommendations be for a cheap amp that can work well on my mid bass channel?
I guess 100WPC into 8ohm would be good.
BTW, we tried the Behringer Inuke on the mid channel and it did not work well, so that kind of amp is out of the question...
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Post by John on May 3, 2015 19:30:50 GMT
The Crown might be worth a try. Awhile back Chris linked in a stunning semi pro amp that would be the ideal choice if you can find it the Chameleon power amp would be my choice
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Post by speedysteve on May 3, 2015 19:37:53 GMT
John, which crown were you thinking?
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Post by John on May 3, 2015 19:47:39 GMT
Hopefully Jerry will come along I know he used one in his full range system and did not have the issues the Behringher has at other frequencies
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Post by John on May 3, 2015 19:50:15 GMT
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Post by pre65 on May 3, 2015 19:58:23 GMT
Quad 606 ?
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Post by speedysteve on May 3, 2015 22:59:51 GMT
Thanks John and pre65.
Will check out the Crown D class and Quad is an idea. I have limited experience of listening to Quad 405's and helping recap a pair.
The 606 is more powerful and a neat unit as it's stereo. 405's could live near each mid bass horn, but then I'd have to shoot the signal down the room. I might be able to borrow a listen to the 405's sometime... Always good to try before committing.
I think these power amps may end up living behind my rack or record rack / amp station so cosmetics do not matter.
There's also a Crown XLS1000 that may be enough for my needs - 215wpc into 8ohms and has quite a nice price tag. Same tech as the
XLS1500.
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Post by ChrisB on May 3, 2015 23:21:49 GMT
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Post by Eduardo Wobblechops on May 4, 2015 5:57:03 GMT
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Post by jandl100 on May 4, 2015 6:44:38 GMT
re: Crown.
I had the XLS1500.
Nice amp - open, powerful, quite well controlled. Didn't have the sheer grip and scale of my old Parasound A21, and the midrange rez was good but not great.
Word on the street is that the XLS1000 is not up to the rest of the range.
After being a fan of class D for many years, I think I am going off them a bit - some I have heard are really musical (i.e. they sound like real music, to me, in a way that most amps don't) and they can be great allrounders but there's a layer of fine rez that even the best that I have tried miss out on. And even the powerful ones like the 300wpc Crown XLS1500 sound like they don't get the grip on the speakers of a really good current-heavy class AB amp like Martin's Chord or the big Parasound.
But if you are comparing them to the likes of a Quad 405 or 606, then yep, the Crown XLS1500 is a way bit better, imho. |
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Post by speedysteve on May 4, 2015 7:27:18 GMT
Thanks guys. Interesting stuff. This covers a few power amps of the Chameleon age... www.hi-fiworld.co.uk/index.php/olde-worlde/311.htmlI had the MF A3CR pre and power once upon a time - Was easily bettered in full range applications by the rather special project build Son Of Heffa 6SN7 / KT88 amp I built. Had a massive mains traffo, soft start silicon power reg, true class A, 25W tail resistors and nice Lundahl output traffos. This was using back using ProAc D25's and then big Tannoys. Here it is as was with a vol pot on (was better as a straight power amp...)   I kept it for a ages and I did try it in my horn systems (early on) and did not find it did anything that special on bass duty. Was large, heavy and hot running... Not bad on the mid horns (JBL2482 compression drivers), but the little EL84 SET amps from Icon Audio are better again for the upper channels. Hence my search for silicon for bass. It is certainly overkill looking at amps as all round competent as say the Chord. I need an amp that everyone says "did the bass ok but the rest was rubbish" - and a price tag to match  |
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Post by Deleted on May 4, 2015 7:44:07 GMT
I'm not a great fan of the 405 - it has a number of quirks that cause it to auto-destruct. The resistors that feed the 15V zeners on the input op-amp are underrated (>0.3W into a 0.25W part) and eventually one goes open circuit. That takes the output to one rail, and the dumb crowbar (diac/thyristor) operates and shorts the output. So first the power transistor dumpers and driver go phut, then the crowbar itself dies, then finally the fuses blow. So first thing to do is replace those resistors as a matter of course. Then one of the electrolytic capacitors on the board is right above a high dissipation power resistor, and cooks - they usually look dark brown with a cracked case. So it is good to replace at least that capacitor, and mount it under the board out of the way of the heat. And while in there replacing the underrated resistors and one capacitor, it is good to replace all the electrolytics on the boards. All in all, unless it has been properly fettled by someone who knows what they are doing, steer clear of a 405. But, since you are driving a horn, which which you say does 110dB per Watt and hence not need much power, have you considered something valved? Usually excel in the midrange if you get a decent one; for example a pair of Quad II. A sensitively restored pair (including preamp, which you don't need) went for £565 in March, item 171688858317. That seems the typical price. And at 110dB per Watt, a 100W amp will have the capability to make your ears bleed  |
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Post by MartinT on May 4, 2015 8:00:33 GMT
Whilst the efficiency requirements suggest not much power is required, the amp needs to have huge damping factor to control the bass drivers. Not a job for valves, really.
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Post by speedysteve on May 4, 2015 8:06:42 GMT
Yes and no craig - I have had a very good valve PP amp - see prev post. Get what you are saying about Quad 405's. Is the 606 clear of those issues? Martin's Chord was not throttled back very far to get it to the right SPL on the mid bass horn - it was getting about -6dB less signal than the other channels. Bear in mind my upper channels are ~115dB/W  I think it is all about cone control and speed in this mid bass application. Pretty much everything that I thought I knew about amps needing to sound nice across the whole freq range is somehow not applicable when you just put them on confined freq bass duty. As we found the Chord did it better than the Topping TP-60 (as you'd expect), but once we got the sub channel really singing the TP-60 was ok filling in the 90 - 300Hz bit. I now want more than OK of course:) The Topping did as well as my 25W KT88 PP valve (admittedly that was with Emience kappa drivers not the JBL2220's that are more valve era and a bit easier to drive. I think I really need to beg, steel or borrow some amps and have a listen / play to see what works. Small and neat would be preferable over huge, hot and heavy:) Keep the suggestions coming and if anyone is close enough to come along and have a listen with an amp (in my price range) that would be great. Could be the Crown offerings do a perfectly good job, likewise the 606. But, how to know... |
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Post by speedysteve on May 4, 2015 8:07:15 GMT
Whilst the efficiency requirements suggest not much power is required, the amp needs to have huge damping factor to control the bass drivers. Not a job for valves, really. Wot he said:) |
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Post by John on May 4, 2015 8:10:17 GMT
Yes agree you need something with a lot of control in the bass the Chameleon would certainly do that if you can find one
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Post by John on May 4, 2015 8:12:52 GMT
Perhaps the amp that Craig made could be used for this
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Post by jandl100 on May 4, 2015 8:43:18 GMT
Not sure you can beat class D amps for damping factor, often a 1,000 or more.
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Post by MartinT on May 4, 2015 8:56:37 GMT
Not sure you can beat class D amps for damping factor, often a 1,000 or more. The Behringer certainly proved that point in tapped bass duties, wonderful control. Perhaps a more refined class D amp, like a Crown, is the solution for the upper bass horn, as has been discussed. |
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Post by John on May 4, 2015 10:37:08 GMT
When I visited to Craig he was using a Douglas Self design that had wonderful mid bass Might be worth a try I am sure Greg can point you to links around the design
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