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Cheap amp to get 11 channels out of a denon x4700h

tomtan

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I'd like to do 7.1.4 with my AVR-X4700h and as such I need an external amp. I looked and that amp can only power either the height 2 or the front speakers.

Since I really don't want to spend much money, I think heights 2 might make more sense. Those are SVS elevation speakers with 8 ohm impedance and "Recommended amplifier power: 20-150 watts."

What would be a good cheap chinese amp for this use case? I was thinking of maybe using the AIYIMA A07

Bonus since I'm also going to get an amp for two tactile transducers I plan to add (Aurasound AST-2B-4 Pro (4 ohms, 50 Watts RMS ), would there be a good 4-channel amp I could use or would it just be better and cheaper to get two amps?
 

rationaltime

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In my opinion your setup suggests a used commercial or consumer amp off
craigslist would be a consistent match for taste.

However, recently I purchased a small Topping amp off ebay to give to a friend.
I also purchased a small Fosi Audio amp for another set up. Both seem to work
well. As far as I can tell they were made in the same factory. From pictures it
appears the Aiyima products come from the same place. These all use amplifier
chips from manufacurers with good reputations. In my case they claim TI power
amp chips.

I already gave away the Topping amp, but the Fosi amp is still not in its final set up.
So, I have it to play with. It comes with tone controls and drives two way speakers
with 8 inch woofers plenty loud enough. It also has bluetooth input, which can be
helpful for debugging at set up. It looks like the Topping brand is attempting to
move up scale, but for an amp I see no reason to choose Topping over Fosi Audio.
Other than the TI data sheet I would not believe any of the claimed power numbers.
Still there seems to be anough audio power.

I purchased those amps used off ebay. They have been showing up there regularly
with attractive prices. Based on that experience I decided to purchase a new Fosi
amp (still inexpensive) with more features for another location. It has not arrived yet,
so I can't report. These are 2 channel amps, but cheap enough for you to try out,
especially if you buy used.

If you are planning to add magic fingers to your chair, I think the frequency range
would be much lower than the speakers. To me a 4 channel amp does not feel
like a good fit. I would also be inclined to worry about the electrical characteristics
of the load. If it were my expensive AV receiver I would not use it to drive those
heavy solenoids. How can you tell how hard you are driving those things? An
older big amp might better tolerate the abuse.

Well, that is my opinion.
 
OP
T

tomtan

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Mar 28, 2019
Messages
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In my opinion your setup suggests a used commercial or consumer amp off
craigslist would be a consistent match for taste.

However, recently I purchased a small Topping amp off ebay to give to a friend.
I also purchased a small Fosi Audio amp for another set up. Both seem to work
well. As far as I can tell they were made in the same factory. From pictures it
appears the Aiyima products come from the same place. These all use amplifier
chips from manufacurers with good reputations. In my case they claim TI power
amp chips.

I already gave away the Topping amp, but the Fosi amp is still not in its final set up.
So, I have it to play with. It comes with tone controls and drives two way speakers
with 8 inch woofers plenty loud enough. It also has bluetooth input, which can be
helpful for debugging at set up. It looks like the Topping brand is attempting to
move up scale, but for an amp I see no reason to choose Topping over Fosi Audio.
Other than the TI data sheet I would not believe any of the claimed power numbers.
Still there seems to be anough audio power.

I purchased those amps used off ebay. They have been showing up there regularly
with attractive prices. Based on that experience I decided to purchase a new Fosi
amp (still inexpensive) with more features for another location. It has not arrived yet,
so I can't report. These are 2 channel amps, but cheap enough for you to try out,
especially if you buy used.

If you are planning to add magic fingers to your chair, I think the frequency range
would be much lower than the speakers. To me a 4 channel amp does not feel
like a good fit. I would also be inclined to worry about the electrical characteristics
of the load. If it were my expensive AV receiver I would not use it to drive those
heavy solenoids. How can you tell how hard you are driving those things? An
older big amp might better tolerate the abuse.

Well, that is my opinion.

Thanks, the one advantage I have is that because I'm based in Hong Kong, it's slightly cheaper to buy CHIFI stuff like Fosi etc... On the other hand, second hand things tend to be rather expensive when I search, to the point where it's often been cheaper to buy new from amazon (shipping from US with amazon is free) than to pay for what I see in facebook marketplace.

One thing I've been wondering for the amp driving the two height channels, how does it stay in sync if I lower the volume on my denon AVR? Will I need to manually also lower the volume on the amp too? or does lowering the volume on the AVR lowers the volume on the pre-amp signal?


For the "magic fingers" (I love the name) for the chair, I do plan to add a dsp before the amp for this to manage the crossover cut off to 50hz or so. It's true though that I don't think having a perfect amp matters for those and instead an older cheaper amp would be perfect.

EDIT: Spent some time browsing facebook marketplace here, the only reasonably priced amp I could find is the onkyo-a-9010 for 115 usd. Not sure if that's great value.

EDIT2:
Well if I'm reading the specs for that Onkyo correctly, maximum total harmonic distortion of 0.7% at 4 ohm => 43dB sinad... That seems like mostly garbage? or am I completely misunderstanding this?
 
Last edited:

rationaltime

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Though I am not familiar with your equipment, I expect the AV receiver to have
variable line level analog output that tracks the master volume control. I don't
know if or how the receiver might adjust the signal to achieve "surround sound".
The manual should describe how it assigns the output channels.
 
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