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AVR Hack for Pre- outs

Amarendra

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Dear FMs,

Was just wondering if it is possible to hack an AVR without pre-outs to provide preamp signal to be fed to an external amplifier. After some R& D came across the following 2-3 options to get it done:

1. Surgery- open the AVR , find the signal path between preamp and amplifier board and solder a wire from the preamp FL, FR and ground out to an unused RCA port on the back of the AVR. However considering the price of an AVR it is difficult for most of us to use this option although it can be easily be done by FMs with some tinkering experience. The result will be the same as having pre-outs to an otherwise sealed AVR.

2. Use a High Level - Low Level converter: this is something which is used in car audio to connect an external amp to a factory fitted car amp without pre amp outs.
The converter basically converts the high wattage speaker signal to low wattage signal which can be safely fed to another amplifier. However I am not sure if this device meant for car audio can handle a large wattage signal coming from an AVR meant for center/ FL/FR (don't mind the use of technical words such as wattage since I don't belong to "that" field)

3. Use a professional converter such as Behringer DI 4000- for about INR 3,900 (for 1 channel) to about INR 9,000 (for 4 channels), this seems like a viable option. The only requirement will be that of a XLR to RCA converter to feed the output to the RCA ins of a power/ integrated amp.

If we can use any of the 3 methods above then there won't be a need to buy expensive AVRs (except for more channels). We can simply add power amps and run the show.

There is not much of material on the above approach. If any of you have tried these methods or have comments on what could work please let me know.

Thanks !
 
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elangoas

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have comments on what could work please let me know.
Though i have never tried your idea, it sounds interesting to add pre-outs to an AVR (if that is possible).. Guess, it would require a skilled person to do that (or) someone who understands electronics very well..

Good luck, and keep us posted on what you decide to do..
 

MaSh

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Definitely worth a try if it's your spare receiver sitting idle. If not, better to get an older marantz nr series with pre outs and start enjoying the movies quicker.

MaSh
 

Amarendra

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Definitely worth a try if it's your spare receiver sitting idle. If not, better to get an older marantz nr series with pre outs and start enjoying the movies quicker.

MaSh
Currently I have a Pioneer LX 302 and a Denon 2500H hence movies is not a problem. This is more an attempt at exploring possibilities. Wish I had a cheaper entry level AVR- would have tried option 1 (surgery) on it :)
 

bornfi

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If only for fl and fr, if the receiver has headphone out, would that work too because I think it is preout equivalent?
 
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greenhorn

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your reciever has hdmi out - does it allow dts/ac3 over it ?
if yes, then get an hdmi to spdif box + a spdif to 8 channel converter
 

Amarendra

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your reciever has hdmi out - does it allow dts/ac3 over it ?
if yes, then get an hdmi to spdif box + a spdif to 8 channel converter
I have so far not seen any quality HDMI/ SPDIF to analog converters. Also in this method we would be relying upon the converter's DAC which is most likely to be inferior to the one used in a mid range AVR ?
 

greenhorn

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well, your AVR doesnt have a 8 channel DAC from which the pre out is readily available.
Yes it will be inferior to the dac in the avr, but compared to using a high level to low level convertor, it could go either way
If your intention was to bypass the internal amp of your AVR, why buy one in the first place without surround pre outs.
 

Amarendra

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well, your AVR doesnt have a 8 channel DAC from which the pre out is readily available.
Yes it will be inferior to the dac in the avr, but compared to using a high level to low level convertor, it could go either way
If your intention was to bypass the internal amp of your AVR, why buy one in the first place without surround pre outs.
It is not a question of whether I or someone can buy or not, it is a question of whether it is doable or not and in an elegant manner.
 
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rpmahale

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I have requested Profx service technician to provide me pre-out of front channels in my Denon AVR 2113, but he refused to provide as company doesn't allow for any such modifications. How it will work with local service center is big ?. But certainly main pre out is very helpful in increasing power of front channels which allow more power to other channels with increase in overall headroom.
 

Amarendra

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I have requested Profx service technician to provide me pre-out of front channels in my Denon AVR 2113, but he refused to provide as company doesn't allow for any such modifications. How it will work with local service center is big ?. But certainly main pre out is very helpful in increasing power of front channels which allow more power to other channels with increase in overall headroom.
I have ordered a Rockford Fosgate converter from high level to low level. Will let you know how it goes.
 

Amarendra

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I have requested Profx service technician to provide me pre-out of front channels in my Denon AVR 2113, but he refused to provide as company doesn't allow for any such modifications. How it will work with local service center is big ?. But certainly main pre out is very helpful in increasing power of front channels which allow more power to other channels with increase in overall headroom.
The passive high to low voltage converter arrived yesterday. I connected it to the front left and front right speaker outs of the Denon 2500H receiver. The outputs of the converter were connected to the RCA ins (CD) of the Rotel RA 10 amplifier. The Front Left and Front Right Speakers were connected to the Rotel's FL and FR terminals. I disconnected all other speakers from the AVR so that I could do some critical listening and understand distortions in sound if any.

I carefully turned on the AVR and the Rotel with both dials (volume) at Nil and played a Vinyl through a TT connected to the Denon AVR. First I increased the Denon volume gradually to see if there were any temperature spikes anywhere (heat) and then turned up the Rotel to about 9 o clock. I was pleasantly surprised to be greeted by sweet music. No distortion- humming or hiss of any sort. There was a slight spike in low end and some sparkle at the top end. I was taken aback by the bass since I had never heard my bookshelves produce such bass before. However it wasn't fatiguing or overpowering the other frequencies.
I was listening to music very critically yesterday and checking temperatures of the AVR, Rotel and most importantly the passive converter. The Rotel was slightly warm around the heatsinks and the Denon was warming up slightly.
I was listening to music for almost 2 hrs yesterday from Jagjit Singh to Bob Dylan to Bollywood songs streamed from Amazon music.

After 2 hrs, the Rotel remained warm not hot. The AVR was warmer but I guess this was due to continuous 2 hrs use and the converter was as cold as a cucumber.

Impressions regarding sound in general:

1. Slight uptick in low frequencies- which added positively to the experience.
2. Complete silence on hiss- hum
3. Very wide soundstage- sometimes going outside the speaker width
4. Vocals were crystal clear- in fact in one of the tracks I could feel Kumar Shanu running out of breath at the bottom end :)
5. Vocals seemed elevated from the rest of the sound field and I mean literally- centered but slightly gaining in height- don't know if this is good or bad but sounded good.

Cons:
1. AVR is still using the amp section (cant bypass this unless I open the AVR and bypass the amp)
2. The signal is going through 2 preamps- the Denon as well as the Rotel. This will continue unless I connect a power amp.

I will continue to test this for a longer duration and then order another one for the center channel :)
 
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