NAD 906 Power Amp + Sonodyne Sia 208R as Pre Amp

[sadnabrina]

Dear FMs,

I had recently picked up an used (and pretty old) NAD 906 Power Amp in decent condition from a FM. My intention was to get a feel of NAD SQ and the bit of extra power when used in bridged mode over my existing Sonodyne SiA 208 R. Being on a tight budget I thought if the combo clicks then I will keep the setup for a few years before I can pull in more money to upgrade.

The NAD 906 actually has 3 completely separate stereo amplifiers inside each can be bridged into 90W@8 Ohm Mono.

The setup is as follows -
Source: Denon 1740 DVD Player with a built in Burr-Brown 24-bit,192kHz DAC
Pre Amp: Sonodyne SiA 208 R - used as a source selector and preamp
Amp: NAD 906 -Using 2 of its 3 amps in bridged mode to get 2 channel stereo
Speakers: Sonodyne 2605 V2

Now with this setup I am definitely getting a much improved sound stage, better low and mid response and definitely a much better overall SQ, but the overall volume of the setup seems lower when compared to the SiA 208 R.

With the Sonodyne driving the speakers I would usually have the volume set at 40, while with the NAD, to get the same loudness the volume needs to be pushed above 47. I tried to play at very high volumes and the Amp does not seemed stressed at all even at the highest volume setting. I tried playing around with the soft clip switch but it made no difference.

I thought the additional power of the NAD would result is a much louder output than the Sonodyne. But it is not happening! Why? Can you help?

 

[cyber_cat]

Hi,

With the Sonodyne driving the speakers I would usually have the volume set at 40, while with the NAD, to get the same loudness the volume needs to be pushed above 47.

Different amps have different input sensitivity, no problem here.

Sonodyne SiA 208 R = 65 W ~ NAD bridged = 90. There is no significant wattage difference here. 65 W to sound twice as loud, you will need a 650 W amp.

Cheers

 

[sadnabrina]

Hi,


Different amps have different input sensitivity, no problem here.

Sonodyne SiA 208 R = 65 W ~ NAD bridged = 90. There is no significant wattage difference here. 65 W to sound twice as loud, you will need a 650 W amp.

Cheers

Agree that it is not a significant wattage difference, but 90 W should not be significantly less loud than 65 W. The 90 W rating of the NAD comes with the following statement "Minimum power per chnnel, 20Hz - 20kHz, both channels driven with no more than rated distortion" and IHF Dynamic power is rated at 140W. As per various discussion threads in the forum - NADs are known to be pretty loud as well.

The Volume pot can go from 0 to 63 on the SiA208 and 47 means it is at 3 O'clock position (assuming 0 at 6 O'clock) - around 75% turned - which is pretty high by any standards. Moreover the NAD does not seem to be stressed even a little bit when I played with the volume all the way up to 60 it felt as if I can go much further up.

Is it possible that when using the pre-outs of the SiA208 there is some signal loss compared to what the built in amp gets as input?
Should I try a different/dedicated pre-amp to see if there is any difference?
The source does not have volume control but the NAD has a gain control on the back panel. Can I try connecting the source directly to the NAD while using the gain control knob of the NAD to control the volume? Will that be safe for the equipment?

 

[srisaikat]

Never try to connect a power amp direct to source unless you want to take the heat.

 

[sadnabrina]

Never try to connect a power amp direct to source unless you want to take the heat.

Right boss. Then I must try with a separate preamp. Need someone to spare one for me to try out.

 

[srisaikat]

Ok!, step by step.

First, try the amp with out bridging with Sonodyne Sia 208R as Pre Amp. Tell us what happen to that volume pot.

Second, If the Denon DVD-1740 player comes with volume control then set it to 'zero' before connecting it directly to power amp, then test with NAD with the said bridged mode. Let us know how much volume was needed to get equivalent loudness which you got at 3'O clock setting with SONODYNE as preamp.

Let us know the result.

 

[srisaikat]

One more thing I want to ask, have you used two sets of RCA splitter (each set per channel) during the bridging? Please provide details of connection specs. It will more appropriate if you can upload some pictures of bridging.

 

[srisaikat]

ok, I got it, seeing the picture of back panel from internet I learned the way NAD 906 should be bridged. Still I feel uploading some pictures will be helpful to understand if the connections were ok.

 

[sadnabrina]

ok, I got it, seeing the picture of back panel from internet I learned the way NAD 906 should be bridged. Still I feel uploading some pictures will be helpful to understand if the connections were ok.

I am currently not in the country till next week and wont be able to post actual pictures. But here is a schematic drawn quickly using a downloaded image of the NAD and MS Paint.

Answers to your other queries -
1) Without bridging - the loudness is much lower. Even at the highest volume level it won't give the same level achievable on the SiA208 at 40.

2) The Denon does not have a volume control. But the NAD has a input level adjustment knob. On turning the same the final outout volume goes up or down. Currently it is set at full while playing in bridged mode. Can I try putting it at minimum and connect the CDP directly? But then will need to wait for a few days before I come back and try this out. I will lose my job@home if I ask my wife to do the connections and check the output on my behalf.

 

[sadnabrina]

Here is the schematic image of the connection between the NAD, Sia208 and Speakers. ATTACH]10691[/ATTACH]