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Old 9th October 2012, 04:31 AM   #1
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Default what are you pushing with your chipamp?

Curious what kinds of speakers are being put to use with these chipamps.

I'm thinking of building a simple (and kind of cheap) 2-channel crossover and I wonder what's the experience here.
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Old 9th October 2012, 07:51 PM   #2
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chipamps -just like any other amp- can drive any speaker, as long as the load impedance is correct.
can be" whatever".
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Old 1st November 2012, 03:12 AM   #3
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I'm somewhat surprised by this response. Perhaps it has been beaten to death inside of some thread with 9,000 posts that started in 2002?

I'm just trying to catch up, but I've found a few places that seem to contradict post 2 in at least the most general sense.

First, that "just like any other amp" it doesn't matter:

From the nutshell hi-fi site: (about speakers and tube amps)
"In particular, the Ariels are allergic to Krell, Cary, Pass, and Audio Research products; I'm sure they sound great with different speakers, but I can say from experience that these amps just don't work with the Ariels. "

Another from the decibel dungeon site: (about gainclones)
"the speaker should be high efficiency although anything over 89 db seems to work well with those at 93 db+ working better. Horns are an obvious choice, single driver speakers using a higher efficiency driver are good, and I use efficient open baffles. A few folk have even managed to get GCs working with ESL loudspeakers."

The question in #1 seems pretty direct, but perhaps the question could be restated as not whether sound will come out of the loudspeakers, and instead if there is a particular speaker design that has been particularly successful. In particular, is there a strong record of success or failure with 2-way crossovers?
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Old 1st November 2012, 04:01 AM   #4
fas42 is offline fas42  Australia
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My experience is that the power supply used is key, not whether it's a chipamp or not. Use a miserable power supply, and the result will be that only high efficiency speakers will do the job properly. If you instead use a supply that a Krell wouldn't be ashamed of then most speakers will perform nicely ...

The point being, an amp is an amp, the fact that it looks like nothing is neither here nor there ...

Frank
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Old 1st November 2012, 10:39 AM   #5
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by fas42 View Post
My experience is that the power supply used is key, not whether it's a chipamp or not. Use a miserable power supply, and the result will be that only high efficiency speakers will do the job properly.
I just love this.
Put the PSU in it's (rightful) place, but cover your a... by a conditional statement.

The PSU is what drives your speakers.
If your 8ohm, highly reactive impedance, speaker demands a 10Apk transient current then that PSU MUST supply that current without the supply rail collapsing significantly.
Maybe we can tolerate a 10% droop in voltage, or maybe we can only tolerate a 1% droop, but whatever the fine print might stipulate, the PSU must supply the current for all that the speaker demands.

It's the amplifier's job to modulate that current into what we call music.
The amplifier generally finds it's job a bit easier if the rail voltage modulation is kept to acceptable levels. That's our 1% to 10% coming in again.

Speaker efficiency and speaker impedance and speaker reactance all conspire to complicate the current demand.
Low reactance and high impedance and high efficiency reduce the current demand.
High reactance and low impedance and low efficiency increase the current demand.

This is where chipamps in general fall over. They cannot modulate high currents. They are severely limited in current capability when reactive loads demand current.
Give chipamps a chance. Use high efficiency speakers, use high impedance speakers. And if we have a choice use low reactance speakers. As far as I can see and understand, it's passive crossovers after the power amp that lead to the worst of high peaks in transient current demand.
This may point to full range drivers or active speakers as the ideal loads for chipamps and the PSU that has to power this lot.
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Last edited by AndrewT; 1st November 2012 at 10:42 AM.
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Old 1st November 2012, 11:18 AM   #6
fas42 is offline fas42  Australia
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Quote:
Originally Posted by AndrewT View Post
This is where chipamps in general fall over. They cannot modulate high currents. They are severely limited in current capability when reactive loads demand current.
So what would you call a high current? 10A, 20A, 30A? Last time I looked at the spec sheet they said something in the region of 9A peak current, not too bad I would have thought ...

And if that's not enough, simply parallel: just like the discretes do, any number of times.

As mentioned elsewhere, I used a single chipamp with a relative monster of a powersupply to drive a number of classic 2-way enclosures, to ear deafening levels at times. Biggest problem I had was thermal shutdown, better heatsinking next time ...

Frank
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Old 1st November 2012, 11:35 AM   #7
AndrewT is offline AndrewT  Scotland
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I design discrete outputs for 3 (three) times the current drawn by the nominal resistive speaker impedance.
i.e for 100W into 8r0, that requires a Voltage of 40Vpk and a resistive current of 5Apk.
To drive an 8ohms speaker I assume transients can approach 15Apk. Most transients will be far less and some will be higher.

For a 68W into 8ohms capable chipamp, the equivalents are 33Vpk, 4.1Apk resistive and 12.4Apk transient.

The 3886 is specified for resistive maximum of typical 7Apk and high limit of 11Apk. Conveniently National don't mention the pk (peak) in the specification.
But speakers are reactive and when Vce of the output transistors is NOT equal to zero volts the resistive maximum current capabilities of the chipamp no longer apply.
Spike takes over to protect the output stage from excessive cold temperature SOAR and Spike then applies a de-rating factor for warm or hot operation. National do give some data plots of transient capabilities but only for cold operation. I have not been able to determine reactive output current limits for music type transients during warm operation, from the datasheets.
I do know that they are much lower than the resistive output current limit that is typically 7Apk when cold.

And I agree on the heatsinking issue.
I recommend to all builders to double the value given by the datasheet.
If they say 2.4C/W for your typical operation, then I say use 1.2C/W to lower the chip temperature during operation to much nearer the cold values that National specify in the datasheets.
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Last edited by AndrewT; 1st November 2012 at 11:45 AM.
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Old 1st November 2012, 12:50 PM   #8
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Quote:
Originally Posted by imaginarytime View Post
I'm somewhat surprised by this response. Perhaps it has been beaten to death inside of some thread with 9,000 posts that started in 2002?

I'm just trying to catch up, but I've found a few places that seem to contradict post 2 in at least the most general sense.

First, that "just like any other amp" it doesn't matter:

From the nutshell hi-fi site: (about speakers and tube amps)
"In particular, the Ariels are allergic to Krell, Cary, Pass, and Audio Research products; I'm sure they sound great with different speakers, but I can say from experience that these amps just don't work with the Ariels. "

Another from the decibel dungeon site: (about gainclones)
"the speaker should be high efficiency although anything over 89 db seems to work well with those at 93 db+ working better. Horns are an obvious choice, single driver speakers using a higher efficiency driver are good, and I use efficient open baffles. A few folk have even managed to get GCs working with ESL loudspeakers."

The question in #1 seems pretty direct, but perhaps the question could be restated as not whether sound will come out of the loudspeakers, and instead if there is a particular speaker design that has been particularly successful. In particular, is there a strong record of success or failure with 2-way crossovers?
allergic amps, riight..
Bob Carver - Wikipedia, the free encyclopedia
me thinks it mathers not if its a chipamp ro whatever amp.
as long as it can supply proper output -what the load demands- it can drive it regardless of how efficient is it, it does not even have to be a spekaer, it can be a piece of wire, a lighbulb, Your negihbors electric car, it simply does not mather.
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Old 2nd November 2012, 10:10 AM   #9
bcmbob is online now bcmbob  United States
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Just a few days ago I had an experience that fully supports the information Andrew is providing.. About a year ago I built a pair of OB Sunflower speakers. They produce the most refined and balanced sound I have had in my home. The Sunflowers are considered to be on the low side of efficiency. They replaced a pair of top quality DIY MTM speakers with crossovers designed with the industry leading Leap software at Madisound.

In an attempt to "tune" the new MyRef Fremen Edition power amps, I returned the older speakers back into the room. With all those months passing, I was blown away with what I heard. With just a DAC between the speakers and a PC source, the apparent power (SPL) of the FE amps was 2.5 times higher. I could drive myself out of the room with the older boxes. As the MTMs were designed to be part of a 7.1 dynamic HT system, I will stick with the Sunflowers for high quality two channel listening. But there is no doubt about what any amp is driving has as important an influence on what is produced - as is the design of the amp itself.

I have a JC-2 preamp clone build that can bring the SPL of the Sunflowers very close to the MTMs. But apples to apples, IMHO the info Andrew is providing must be taken into account when considering "what can you push with a chipamp ?"
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Last edited by bcmbob; 2nd November 2012 at 10:14 AM.
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Old 3rd November 2012, 10:13 AM   #10
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where did i put my can of snakeoil...
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