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Can I use the speakers with this amplifier?, Speakers from broken Micro Hi-Fi System
larswes
post Oct 19 2012, 17:12
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My Philips MCM7 amplifier is broken (bought it 5-6 years ago).
But i think the speakers from the system is still ok.
I consider to buy a new amplifier for the speakers and i found this compact design Dynavoice D-amp.

Do you think this could be a good combination, for music and tv or other source?

From the MCM7 specs:
QUOTE
• Output Power [of my broken amplifier]:
2 x 50 watts RMS, 100 watts total power
• Main speakers [still ok]:
3-Way Bass Reflex
6 ohm impedance
6.5" aluminium con woofer, 2" Tweeter

Dynavoice D-amp
QUOTE
Specifications:
Nominal Power Output (Left & Right Channel (4Ω): 25W + 25W
Nominal Load Impedance (8Ω): 15W + 15W
Main channel: 4Ω - 8Ω
Input Sensitivity: 300 mV
Overload source emf: ≥2V
Frequency Response: 20 Hz – 20 kHz
THD: ≤1%
S/N: ≥95dB
Channel separating degree: ≥70dB

More info about the Dynavoice (sorry only in swedish): http://www.dynavoice.se/dynavoice-d-amp/63/

This post has been edited by larswes: Oct 19 2012, 17:12
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Fedot L
post Oct 20 2012, 00:00
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QUOTE (larswes @ Oct 19 2012, 17:12) *
My Philips MCM7 amplifier is broken (bought it 5-6 years ago).
But i think the speakers from the system is still ok.
I consider to buy a new amplifier for the speakers…
From the MCM7 specs:
“• Output Power [of my broken amplifier]:
2 x 50 watts RMS, 100 watts total power
• Main speakers [still ok]:
3-Way Bass Reflex
6 ohm impedance
6.5" aluminium con woofer, 2" Tweeter”

==========

…i found this compact design Dynavoice D-amp.
“Specifications:
Nominal Power Output (Left & Right Channel (4Ω): 25W + 25W
Nominal Load Impedance (8Ω): 15W + 15W
Main channel: 4Ω - 8Ω
Input Sensitivity: 300 mV
Overload source emf: ≥2V
Frequency Response: 20 Hz – 20 kHz
THD: ≤1%
S/N: ≥95dB
Channel separating degree: ≥70dB”?

These Dynavoice D-amp Specifications are from the:
http://translate.google.com/translate?js=y...history_state0=
And
http://www.tradera.com/12-v-forstarkare-mi...70613_166584511
is another amplifier.

And
“* Specifikationer:
* Output Power: 180W + 180W
* RMS Power Output: 30W
* Peak Maximum Power Output (PMPO): 180W
* Input Power: 12V 6A DC”
How can an amplifier fed by a “12V 6A DC” (i.e. 72 VA) power supply, be “Output Power: 180W + 180W” (360 W!)?

“* Min. THD: <0.005%”
“Min. THD: <0.005%” is an absurdity as an amp’s THD characteristic. Then MAX THD may be 10%, or more?..

And between THD “≤1%” and “<0.005%” (200 times difference between two very similar devices), do you believe it’s realist? Which of the two may be real?

QUOTE (larswes @ Oct 19 2012, 17:12) *
Do you think this could be a good combination, for music and tv or other source?

Why do you wish to buy a 13 V amplifier? Or I’ve misunderstood something? A 13 V amplifier for a home system?
With “THD: ≤1%”? To me, strange for a modern transistor amp.

Why not to buy one of well-known ≈50 W/channel 220 V 50 Hz integrated amplifiers, with a remote control and developed features? And 100 times better THD… There are very moderately priced ones rating 0,01-0,02% THD 20…20000 Hz on the market…
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larswes
post Oct 21 2012, 08:49
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QUOTE (Fedot L @ Oct 20 2012, 01:00) *
Why do you wish to buy a 13 V amplifier? Or I’ve misunderstood something? A 13 V amplifier for a home system?
As I said "now i know more" and that was what I was after when i posted here. I will try to find something not to expensive to replace the Philips amp.

QUOTE (Fedot L)
Why not to buy one of well-known ≈50 W/channel 220 V 50 Hz integrated amplifiers, with a remote control and developed features?
So far i've not found any amp with these spec within my budget. But i found a piece with RMS 2 * 25 W / 220 V that maybe can be ok?
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Porcus
post Oct 21 2012, 15:28
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QUOTE (larswes @ Oct 21 2012, 09:49) *
But i found a piece with RMS 2 * 25 W / 220 V that maybe can be ok?


Wattage on cheap amps are sometimes like selling rubber bands by the meter, so ... hard to tell. You would be surprised to see how much less they deliver when you feed them actual music – then OTOH you would also be surprised to see how little average power you actually play at.

Often the two best indicators of power for a cheaper amp, are (1) weight! At least if it is a good'old fashioned PSU. Switch mode supplies may be much lighter. Then (2) the power consumption (and the maybe the fuse, although that is rarely an indicator for the very small amps). On the back plate you will often see a power consumption rating.


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Arnold B. Kruege...
post Oct 22 2012, 16:08
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QUOTE (Porcus @ Oct 21 2012, 10:28) *
QUOTE (larswes @ Oct 21 2012, 09:49) *
But i found a piece with RMS 2 * 25 W / 220 V that maybe can be ok?


Wattage on cheap amps are sometimes like selling rubber bands by the meter, so ... hard to tell. You would be surprised to see how much less they deliver when you feed them actual music – then OTOH you would also be surprised to see how little average power you actually play at.


I've done some analysis and some casual experiments in this area.

Theory says that steady multitones with equal size components often if not always have peak values that are 8-10 dB higher than their average. In this context a worst case model of music seems like it should fall within this range. IOW a 100+ watt amp (needed to handle the peak voltages) may not clip playing music (even heavily compressed) when powered by a 15-20 watt power supply, given that the power supply puts out enough voltage.

I've found that if you put a fairly big storage cap (e.g. 40,000 uF) across the power supply, you can run 100 watt rms (not PMPO) car audio amps into clipping with speaker loads and music playing, from laptop power supplies putting out maybe a couple of amps at 15-16 volts. (got to be careful to not trip the over voltage protection in the car amp). The cap sorta bridges the gap between peak and average.
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