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Old 2nd August 2008, 09:35 PM   #1
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Default The Missing element in Chipamps> how to achieve tight kick drum bass with chipamp?

How many chips + filter capacitance to be be used to get kickdrum bass to be tight...

I read many reviews that these amps are not muscle amps and are weak at producing tight bass is it true?

can anybody give suggestions that how to achieve bass as tight as using Bryston 4BSST amps or so?

please help me...

thanks,
Ken
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Old 3rd August 2008, 01:26 AM   #2
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one thing you can do to get better tight bass is A hefty power supply! at least 10000uf per channel.
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Old 3rd August 2008, 08:43 AM   #3
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i was thinking to use 47000uf per channel but wanted to know anything else required...

I was thinking to build 6 chips BPA 300 with 47000uf per channel...

But is that the only reason?
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Old 3rd August 2008, 09:33 AM   #4
AndrewT is offline AndrewT  Scotland
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is your 47mF split into +-23.5mF per channel?
Is per channel the total for the BPA300 or per chipamp or per dual channel chipamp?
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Old 3rd August 2008, 01:50 PM   #5
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Let me tell u my actual loudspeaker configuration..

1.1 inch dual concentric tweeter
6.5 inch mid-bass from wavecor
10 inch Scanspeak 26W Revelator woofer..

now I want to drive the speaker which can easily serve enough power.

I read reviews about Jeff Rowland Concentra with Wisdom Audio M-50 where a 12 inch UNderHung voice coild woofer is being driven by the amp which has 6 chips in BPA config but there was no slam but still the amp was giving enough power. But I really need to calculate the figures...

Jeff Rowland himself said that no speaker can take beyond 8 amps of continuous current since the voice coil wire guage itself cant pickup that huge amount of current. So he said it serves the purpose...

Some people say that Jeff Rowland Model amps and Concentra are atmost performing amps which has LM3886 chips in their model...

http://www.audioasylum.com/forums/am...ages/7578.html

Here the only doubt is that how to get that slam from the chip amps...

I finall thought to build a 8 chips in BPA 400 configuration so that the amp can feed atleast 1 amp of continous power to feed my speaker.

I was planning to buy Bryston but after reading review of
http://www.audioasylum.com/forums/am...ages/7578.html

I just step back since It looked foolishness to spend arround 3000 Pounds for an amp where one can build a superb amp like concentra for a very fraction of price..

JUST JUST JUST one thing which bothers me is the bass.. since I will be using Scanspeak 10 inch Revelator woofers it sucks tons of current from the amp.

Any professional please guide me...

I am planning to build either of the following...

BPA 300 with 6 chips in bridged and parallel + with 47,000 ufd for all chips...

BPA 400 with 8 chips in same config as above with 60,000ufd

my problem is not something that i will be always banging at full volume but even at the lower volumes the bass should be tight enough..

ANY experts please guide me...
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Old 3rd August 2008, 03:37 PM   #6
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Hi rhythmdiy,
I suppose you are using a Scan Speak 26W/4867T00 woofer which can be seen here http://www.bmm-shop.nl/Product.asp?Product_ID=4683

You donīt give us much information about your loudspeakers, are they diy ones? BR enclosures? Volume used? In case they are diy ones have you measured the woofer for T/S parameters?

The data sheet for the above driver says a VAS of 223 l but the measurement in the German Klang&Ton shows 148 l . Qts doesnīt differ much 0,3 vs 032 and a Fs of 18.75 Hz vs 18 Hz is noting to write home about. But the difference in VAS is more than I would have accepted. BTW I have rejected Scan Speak drivers because of the vast tolerances that shows up and not just in this case.
If you are a well-known manufacturer (like a Swedish one) you may return the unacceptable ones, but they may hit the diy market instead.

Iīm very interested in rhythmical music as reggae and afro music.
The reproduction of the bass notes are essential; improvements here have a synergistic effect on the mid range and high frequencies as well. But itīs also the other way around. You canīt look at one parameter more than temporary if you are going to succeed!

You may or may not be on the right track when you concentrate on the amp. My guess is that you overlook a few other important things.

I can only give you some hints of how to achieve a dynamic sound for the bass.

Use DC coupled amps, because phase errors add to each other in a system. If you need a high pass filter such as a rumble filter keep it in the "turntable chain".

Use an active filter for the bass amp and hence the woofer, any coil between the amp and the woofer will consume energy.

Room acoustics and speaker placement and listening position will be of very much importance. Room treatment such as bass traps is necessary in most rooms. You can equalize some but it wanīt help to solve a fundamental problem with room modes.

Decouple the speaker from the floor so that the floor doesnīt act as a delayed sound source. I use feet called the SD-feet and this is a big improvement as the concrete floor is more "silent" now.

Think of the system as precisely what it is; a rather complicated system where you have to focus on the totality.
Your amplifier hypothesis may be verified or not if you borrow a really potent power amp to start with. Itīs probably not only a question of delivering enough power but how to handle the back-EMF from the speaker as well.

Eight amperes? It depends on so many things Iīm always sceptical about such figures. For how long duration? Does it apply to big PA drivers as well?
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Old 4th August 2008, 07:02 AM   #7
CJ900RR is offline CJ900RR  Sweden
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Im not an expert in that way that Im able to calculate stuff in the advanced way in theory like our good source AndrewT and others. Im more of a build-and-see-guy, but this is my experiance.

2 pieces of this boards bridged: Click the image to open in full size.

together with an unregulated power supply ( => 1000VA) and 47000uF/channel, is able to deliver a punchy rappid bass that I think would live up to your demands.

I've been using this for a week now and the bass is deep, natural and does not take over the sound (witch I hate), until it's really meant to. I have been making many different amps and my experiance is that bridge/parallel-config together with a heavy powersupply gives best performance.
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Old 4th August 2008, 10:10 AM   #8
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Hello All,

It is sounding to me (no pun intended ) like everyone who has posted to far has plenty of amp, with plenty of speed. One thing concerning the huge amount of capacitance some of you are using: Are the caps a bank of smaller ones, or are some of you using a single 47,000uf cap?

A bank of smaller caps is faster! For instance, if I wanted 10,000uf of capacitance on each rail of a power supply, I wouldn't use a pair of 10,000uf caps. I would use 2 pairs of 2200uf, and 2 pairs of 3300uf.

Another thing that hasn't been mentioned yet as far as correctness of bass is concerned: Make sure the signal is getting to your speakers in the correct polarity! In the real, acoustic, world the beginning of any acoustic sound begins with a pressure wave. To reproduce it accurately via electronics, a pressure wave will be recorded as a positive rise in current, and the rarefaction immediately after the pressure wave will be recorded as a dip towards the negative rail. You have to make sure that when your system is trying to play back that pressure wave, it is pushing the speaker cone OUT, not pulling it in. That's why the pressure wave is recorded as a positive rise in current!

Now, does checking polarity involve doing complicated tests? No. You can do it that way if you like, but simply swap the connections on the back of your speaker, red for black, on BOTH speakers. If suddenly the bass sounds correct, especially on a bass, or kick, drum you have found the issue. The fix? If you only listen to one source, you're done!

If you listen to more than one source, here's a hint: Most CD players invert polarity. A correctly set up turntable does not. Tuners generally do not. Tape decks generally do not, but that depends on what was used to record the tape. The iPod inverts.

There are many solutions, of varying degrees of cost and difficulty, but there are many nice preamps out there that can handle the problem on the fly, by pressing one button, even though sometimes that button is incorrectly labeled "phase invert".

Don Taylor
BrassTeacher
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Old 4th August 2008, 02:14 PM   #9
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A check list to eliminate possible faults may be a good thing. The problem can be up to a few things that together contribute to the non optimal sound. Or it can of course be up to one important factor like the power amp isnīt capable of delivering the current needed.
Fault finding usually takes time because you have to check the possible errors that have some sort of hierarchy in your mind in order of probability. But in reality, the order can be reversed so the fault that was the last on your list was the one you should have started with.

Excuse me for being a bit theoretical, I am still not convinced that the problem is due to too little current when driving the speakers.

I can be wrong about this, but speakers and especially the cooperation between the drivers is crucial. In addition the woofer has to return fast enough after the pulse of e.g. a kick drum. The used woofer has a relatively high Cms value of 0.9 which means the suspension is soft. This also leads to the low Fs of 18 Hz.

I read about the claims made by Talon ( a loudspeaker manufacturer) some years ago, that a low Fs isnīt always a good thing because the cone of the woofer has not much support from the suspension to return to rest, and thus has to rely solely on the current driving the voice coil.

Itīs true that different amps have different abilities to control the drivers of a loudspeaker. Damping factor is a somewhat complicated matter and has been discussed on this forum.

I can only advise you to check the hypothesis that the problem is caused by the amp. Try to borrow an amp that has a documented ability to produce kick drum bass.

Itīs much about synergy so what one person reports about an amp is not generally true. Hi-fi magazines often make claims that are not valid.
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Old 5th August 2008, 04:36 PM   #10
weissi is offline weissi  Europe
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As with all chipamps, they are very limited with impule current delivery. You should at least parallel 2 or more of them if you wan't them to perform on par with Scan-Speak Units...

As of now I don't think that much capacitance in the PSU will help that much. Just look that at least 100uF are placed as close as possible with thick traces to the chip's. Maybe 1uF film caps directly at the power pins....
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