..is of course not the correct way to deal with it, because individual attentuation per channel is needed. So there will be a potentiometer (= Rin) per channel, and an input buffer is highly recommended, because the total Rin will be very low due to so many potentiometers in parallel.pacificblue said:
That means for the OP to either use twelve motorized pots with remote control or a twelve-channel pre-amplifier.
There must be a misunderstanding here. The powers mentioned in my post are all 1% THD or nominal output, not average. That is nearly the point, where the clipping protection would just set in, but even with ±25 V rails 14 W is not the average power. The highest possible average power would be 20 dB below nominal (1/100 of nominal) for normal music. Maybe only 10 dB (1/10 of nominal), if you listen to dynamically compressed pop TV or radio stations.danielwritesbac said:
±25 V would give you around 30 W into 6 Ohm. Compared to my recommendation you are more than doubling the heat dissipation.
Clipping would be at around 3 dB higher SPL, but the dissipation limit would be reached below 14 W output. Even with fans SPiKE would limit the power due to overheating to an unuseful level much below 14 W.
More available power means more heatsinking and higher transformer power rating. The TF package raises the heatsinking demands even more. All that results in higher cost and more space reuirements.danielwritesbac said:
Decreased complexity, when it comes to heatsink mounting vs. increased complexity, when it comes to mounting twelve ICs instead of four.
As usual, everybody has to find the compromise that suits him/her best.
Which would look like this?danielwritesbac said:
I think you're entirely correct.
Except, that by my temp probe, the heat doesn't exactly double when you change up to 25v rails. However, any way we look at it, the heatsinking capacity needs to increase. If one voltage could cause an overheat, so will the other that's only 5v different. The problem is insufficient heatsink to cope with the consequences of the load.
How many channels per each of the huge heatsinks, considering the 25v rails?
EDIT: Each 3" length of the extrusion is rated 0.72 C/W; however, the product is 6" long.
EDIT2: Assume 6 ohm speakers as the centrepoint reference.
P.S.
Although I like your chip recommendation much better, the LM3875TF isn't a problem with Artic Silver (works for plastic to metal), and the documentions for amplifier assembly are nearly endless. I think that it has certain advantages that need to be considered. But, we could just let somebody else consider them. 😀 EDIT3: Well, the heatsink figures do need to be sufficient in case someone wants to use LM3875.
Except, that by my temp probe, the heat doesn't exactly double when you change up to 25v rails. However, any way we look at it, the heatsinking capacity needs to increase. If one voltage could cause an overheat, so will the other that's only 5v different. The problem is insufficient heatsink to cope with the consequences of the load.
How many channels per each of the huge heatsinks, considering the 25v rails?
EDIT: Each 3" length of the extrusion is rated 0.72 C/W; however, the product is 6" long.
EDIT2: Assume 6 ohm speakers as the centrepoint reference.
P.S.
Although I like your chip recommendation much better, the LM3875TF isn't a problem with Artic Silver (works for plastic to metal), and the documentions for amplifier assembly are nearly endless. I think that it has certain advantages that need to be considered. But, we could just let somebody else consider them. 😀 EDIT3: Well, the heatsink figures do need to be sufficient in case someone wants to use LM3875.
Ceiling speakers and many in-wall speakers will reach fidelity limits on approximately 10 watts. Given that the figure doesn't include headroom, then approximately 20 watts is a maximal amount. In my opinion, more than "true 20 watt" would not be useful, unless breaking drywall is the purpose. 😉 The difference between this and 40 watts is +3db from the speaker, which may be an unnoticeable difference as it is quite small.
So, what is a minimal amount?
Let's take the Pioneer B20 as an example, and its use, with a tweeter added, for easy listening. The limitation is whatever power it takes to rattle the whizzer. We don't want to listen to noise.
Approximately 6w will do.
bathroom, garage, office, etc. . .
Given that energy conservation and price tag are paramount, then these will do: http://cgi.ebay.com/2-15-watt-4ohm-...ryZ18795QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
There is a thread here on diyaudio.com that lists a few simple tune-ups for these "Sure Electronics Tripath" boards. Adding a speaker output zobel is recommendable.
Option:
Even less expensive is the similar sounds from Sanyo LA4625/8 http://www.datasheetcatalog.org/datasheet/sanyo/ds_pdf_e/LA4625.pdf
Notice that there's no NFB cap needed and no output cap either, despite the fact that it runs on regulated 12v-14.5v quite easily. Its also simple to solder point-to-point or perfboard. Useful power output is similar to the Tripath, as is the sound. Both are BTL.
In these two cases, the heatsink expense is reduced.
So, perhaps we can make one powerful 6 channel amplifier and one lower powered 6 channel amplifier. Then these can be mixed-n-matched as need be for scale-able power?
So, what is a minimal amount?
Let's take the Pioneer B20 as an example, and its use, with a tweeter added, for easy listening. The limitation is whatever power it takes to rattle the whizzer. We don't want to listen to noise.
Approximately 6w will do.
bathroom, garage, office, etc. . .
Given that energy conservation and price tag are paramount, then these will do: http://cgi.ebay.com/2-15-watt-4ohm-...ryZ18795QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
There is a thread here on diyaudio.com that lists a few simple tune-ups for these "Sure Electronics Tripath" boards. Adding a speaker output zobel is recommendable.
Option:
Even less expensive is the similar sounds from Sanyo LA4625/8 http://www.datasheetcatalog.org/datasheet/sanyo/ds_pdf_e/LA4625.pdf
Notice that there's no NFB cap needed and no output cap either, despite the fact that it runs on regulated 12v-14.5v quite easily. Its also simple to solder point-to-point or perfboard. Useful power output is similar to the Tripath, as is the sound. Both are BTL.
In these two cases, the heatsink expense is reduced.
So, perhaps we can make one powerful 6 channel amplifier and one lower powered 6 channel amplifier. Then these can be mixed-n-matched as need be for scale-able power?
Price
As far as price point goes, one of these can run many TDA2050
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=227-2010
.
TDA2050 (only 5 pins):
http://www.st.com/stonline/products/literature/ds/1461/tda2050.pdf
*A pair of these can drive a pair of speakers via a 3 conductor multistrand cable, such as a 14 to 12 ga "outdoor extension cord" from the hardware store.
**Arrangement per stereo pairs can help limit parts count.
.
TDA7265 (stereo+mute with only 11 pins):
http://www.st.com/stonline/products/literature/ds/1478/tda7265.pdf
*Can be run bridged, possibly an advantage (because of the long cables), since bridged has active drive for speaker reference (not reliant on ground); however, this requires two separate conductors per each loudspeaker.
**Use clean pair 220uF//100nF power caps and a single 2uF poly on amplifier boards for lower heat than the circuit listed in the PDF.
*** Kapton--an available insulator.
.
Other money-saver (oversize clip):
Oversize "spring clips" speaker terminals that handle 12ga cable. Availability: Parts Express. These are cheaper, safer, and more reliable than a binding post because they limit mixups, and maintain constant, fierce, steady, pressure on the cable. Audiophiles might say that it miraculously "lifted the veil," but I'd just say that it made good contact, and that reliable contact is more important than decorating the rear end of the amplifier. 😉 As for me, I'm much too clumsy to operate 48 binding posts unscathed, so for me, the point is moot. Also, these are an un-complicated location for output zobels.
.
There ya go sports fans! Scalable power, just one transformer, very low price, and no PCB's needed.
As far as price point goes, one of these can run many TDA2050
An externally hosted image should be here but it was not working when we last tested it.
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=227-2010
.
TDA2050 (only 5 pins):
http://www.st.com/stonline/products/literature/ds/1461/tda2050.pdf
*A pair of these can drive a pair of speakers via a 3 conductor multistrand cable, such as a 14 to 12 ga "outdoor extension cord" from the hardware store.
**Arrangement per stereo pairs can help limit parts count.
.
TDA7265 (stereo+mute with only 11 pins):
http://www.st.com/stonline/products/literature/ds/1478/tda7265.pdf
*Can be run bridged, possibly an advantage (because of the long cables), since bridged has active drive for speaker reference (not reliant on ground); however, this requires two separate conductors per each loudspeaker.
**Use clean pair 220uF//100nF power caps and a single 2uF poly on amplifier boards for lower heat than the circuit listed in the PDF.
*** Kapton--an available insulator.
.
Other money-saver (oversize clip):
An externally hosted image should be here but it was not working when we last tested it.
Oversize "spring clips" speaker terminals that handle 12ga cable. Availability: Parts Express. These are cheaper, safer, and more reliable than a binding post because they limit mixups, and maintain constant, fierce, steady, pressure on the cable. Audiophiles might say that it miraculously "lifted the veil," but I'd just say that it made good contact, and that reliable contact is more important than decorating the rear end of the amplifier. 😉 As for me, I'm much too clumsy to operate 48 binding posts unscathed, so for me, the point is moot. Also, these are an un-complicated location for output zobels.
.
There ya go sports fans! Scalable power, just one transformer, very low price, and no PCB's needed.
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