2. amps-preamps
  3. 148737-3667

Bypassing preamp in disc player when using integrated amplifiers

Own a Primaluna Integrated tube Amp &  Oppo UDP-205 disc player. The amp has a HT bypass input.

My goal is to use only the tube preamp in the integrated amp... and bypass the preamp in the player.

  • Option 1) If I hook up the player's analog outputs to the amp's HT bypass input then I am using the solid state preamp in the Oppo and the tube poweramp section of the integrated. The tube preamp in the integrated amp is being bypassed.

  • Option 2) If I hook up the player's analog outputs to a regular input (anything other than the HT bypass) on the amp's, then the solid state preamp on the player as well the tube preamp in the integrated amp are being employed.... i.e double pre-amping.

  • Option 3) Add an external DAC between the player and the integrated. This allows me to bypass the preamp in the player and employ the preamp in the integrated. But the unfortunate downside is that I need to buy a nice DAC instead of using the relatively nice DAC already built into the Oppo... and also complicates the setup.

The analog output from disc players is always the output from their builtin preamps. Since you cant access the direct output from the built-in DAC inside the CD player.... it sounds like an integrated amp pretty much implies the need for an external DAC in the setup. Please correct me.
roxito
Post removed 
bigshutterbug
381 posts
 
Your post is a bit confusing to me in the way it is worded. You stated "My goal is to use only the tube preamp in the integrated amp... and bypass the preamp in the player." For starters, there is no "tube pre-amp" in your integrated PrimaLuna, it has a simple potentiometer on the front end, that attenuates the chosen input, then that attenuated pre-amp signal goes into the tube input/driver stage of the tube amp section. All of the tubes in your amp receive the input signal after it goes through the front-end potentiometer (attenuator) section of the amp. If you run the variable output of your Oppo 205 player directly into the home theater bypass of the amp (its direct input), you are simply bypassing the input selector and input potentiometer of the amp. You do not bypass any of the input/driver tubes of the integrated amp this way. 
If you do choose to bypass the front-end of the integrated amp in the above way, you may hear some improvement in the overall sound quality, depending on how good the variable output stage of your Oppo 205 sounds. If the Oppo 205 varies it output by way of a digital volume control, you will loose some resolution this way at lower output levels, because the player will be dropping bits to attenuate the output signal. 
If the PrimaLuna amp section has a high input gain, that will mean that you will be operating the variable output of the Oppo in its lower range, causing it to loose some resolution and dynamic range as well. If the amp has a fairly low input gain, that might sound better because the 205 will not have to drop as many bits when attenuating its output, and you should get more resolution. Just be sure you have the 205's output set to "variable" first before you try this, or else your amp will receive the full, un-attenuated analog signal into it, which would be very bad!

erik_squires
16,042 posts
 
I think I see the confusion. The analog output of your player is two sections:

Volume control --> Analog output buffer --> Output connectors


We don't usually talk about this as a built in preamp, but it's similar. What most  audiophiles are concerned with is the volume control, because  many would loose resolution at anything less than full output. The solution is to leave  the player at full output and rely on your preamp / integrated to handle it.


The only way to bypass the analog output section is, as you and Elizabeth point out, to use an external DAC.
roxito OP
22 posts
 
Thanks all for chiming in to help clear my confusion. 

I am kinda trying to get clarity on the functions of the aforementioned stages/drivers/front ends/buffers/vol controls/ etc in the player -> amp signal path.

Erik, I think you understood my underlying confusion. I always thought potentiometer/volume control is means there is a preamp there as well. If I understand you correctly: there is no preamp in the player, and the volume control is just a simple mechanism (digital/analog) to attenuate the signal.

Elizabeth, Here is the background for asking that (confused) question.

I use the dedicated subwoofer output from the oppo and control overall volume from the oppo (while setting the volume on the integrated to max). In this setup, using volume on amp instead means subwoofer volume wont change when I change speaker volume. (In my mind) the benefit of this connection is:
 -  it takes the load off of the amp as it is not handling the bass.
 - allows me to use oppo for settings related to main speaker as well as bass management.

The alternative way to hookup would be: player -> amp -> subwoofer -> speakers. Then (as erik suggests), I can use vol control on the amp.

It seems, the key downside of my current setup is perhaps (as per bigshutterbug)... some information loss due to the player digitally attenuating the signal.

Thanks for any more suggestions and clearing up my confusions.


More to discover