[frigginloony]

  hey guys, does anybody know the output voltage of the XLR balanced pre-outs? specifically when it is set to bypass?

according to Oppo preamp output is rated at 4.6 volts.

 

[djsunzi]

Please let us know how it goes...

So I got the adaptor and ran it from the balanced output and it plays same volume as from the xlr output. Sound has much better soundstage and definition. Worth the US$20 I paid for the adaptor. It's basically 4-pin xlr male to 1/4 inch female stereo.

 

[OhMyGodPancakes]

  according to Oppo preamp output is rated at 4.6 volts.

Awesome thank you, follow up question, If I buy one of these attenuators: http://www.ekmpowershop16.com/ekmps/shops/rothwellaudio/balanced-in-line-attenuators-3-p.asp 
How much will the voltage be lowered to with the -10db, -15db, or -20db options?

 

[frigginloony]

 

  according to Oppo preamp output is rated at 4.6 volts.

Awesome thank you, follow up question, If I buy one of these attenuators: http://www.ekmpowershop16.com/ekmps/shops/rothwellaudio/balanced-in-line-attenuators-3-p.asp 
How much will the voltage be lowered to with the -10db, -15db, or -20db options?

well since the site says it has >120 DB my uneducated guess would be 0.552 for 10 db , 0.828 for 15 DB and 1.104 for 20 DB but be warned that's just a calculated guess and I would certainly contact Rothwell for correct figures on that Pancakes if the voltage is critical for you. 

 

[Hooster]

So I got the adaptor and ran it from the balanced output and it plays same volume as from the xlr output. Sound has much better soundstage and definition. Worth the US$20 I paid for the adaptor. It's basically 4-pin xlr male to 1/4 inch female stereo.

 
The  balanced headphone output, which is in a way also XLR I presume. I am not surprised. In my experience the headphone output that is driven by a discrete class A amplifier is significantly higher quality than the XLR and RCA outputs on the back of the unit which are driven by op amps (Sadly Oppo was not able to configure the HA-1 to use the class A amp to drive the RCA and XLR outputs at the rear. I have discussed this with them and the reason they gave for not going this was "compatibility problems". I am not sure what compatibility problems they are talking about, but it is what it is.)
 
I have used the headphone output to drive a power amplifier and I find it produces superior results to the RCA on the back.

 

[MRC001]

Page 29 of the manual says the XLR output level is 4.6 +/- 0.3 Vrms. They say that's measured in HT Bypass mode with volume at max.
 
If there's any difference in quality between the headphone output and the XLR line out, the specs don't show it and I don't hear it. They're both excellent.
 
PS I use the HA-1 XLR balanced outputs to drive an Adcom 5800 which has 26 dB of gain. It matches quite well. The volume knob is very linear and I'm typically around the middle of the range (11:00 - 3:00) depending on how "hot" the source is.

 

[Hooster]

  Awesome thank you, follow up question, If I buy one of these attenuators: http://www.ekmpowershop16.com/ekmps/shops/rothwellaudio/balanced-in-line-attenuators-3-p.asp 
How much will the voltage be lowered to with the -10db, -15db, or -20db options?

 
Why don't you just not use it in bypass mode and use the volume control as an attenuator?

 

[OhMyGodPancakes]

   
Why don't you just not use it in bypass mode and use the volume control as an attenuator?

Well the issue is you select bypass based on input rather than output so it's an all or nothing kind of thing.

 

[Hooster]

 
Well the issue is you select bypass based on input rather than output so it's an all or nothing kind of thing.

 
1. Bypass selected and and an attenuator placed in the signal path.
 
2. Bypass not selected and the volume control used to attenuate the signal.
 
Can you explain how these will produce a different result?

 

[OhMyGodPancakes]

   
1. Bypass selected and and an attenuator placed in the signal path.
 
2. Bypass not selected and the volume control used to attenuate the signal.
 
Can you explain how these will produce a different result?

Well my objective to control the volume at the amplifiers, and my issue is that the balanced amp has a maximum input voltage of 2.8V. So without this, there is significant distortion. 

 

[Hooster]

 
Well my objective to control the volume at the amplifiers, and my issue is that the balanced amp has a maximum input voltage of 2.8V. So without this, there is significant distortion. 

 
My tip would be not to use the balanced out at the back of the amplifier at all. Use the 4 pin XLR at the front of the HA-1 and an adapter to connect it to your amplifier. Use the volume control to attenuate the signal so you do not overload the input of your amplifier. 
 
The headphone outputs at the front are significantly higher quality than the XLR and RCA on the back. They are discrete class A while the outputs on the rear are driven by op amps. 

 

[Hooster]

 
If there's any difference in quality between the headphone output and the XLR line out, the specs don't show it and I don't hear it. They're both excellent.
 

 
The fact is that to me there is a clear difference between the op amps driving the RCA and XLR out on the back and this:
 
"A Class A amplifier conducts signal over the entire range of the input signal cycle. The output transistors are biased to operate in their most linear range, and there is no crossover distortion caused by switching the signal between two push-pull devices. The HA-1's power amplification circuit for the headphones is Class A built with discrete transistors. The discrete design allows us to hand-pick and match the best parts to build the HA-1."
https://www.oppodigital.com/headphone-amplifier-ha-1/headphone-amplifier-HA-1-Features.aspx
 
Why would Oppo go to the trouble hand picking the best parts for a class A output stage with discrete resistors if they could have achieved the same result with an op amp? Maybe you need better headphones/speakers.

 

[MRC001]

  The fact is that to me there is a clear difference between the op amps driving the RCA and XLR out on the back and this:
... Why would Oppo go to the trouble hand picking the best parts for a class A output stage with discrete resistors if they could have achieved the same result with an op amp? Maybe you need better headphones/speakers.

Whether it's discrete, and whether it's class A, are independent. You can run opamps class A, and many preamps / amps do. Discrete designs are not inherently superior to opamp based designs. Either can be designed and built to be audibly transparent; which to use depends on the application. What matters is the component selection, circuit design, power design and isolation, and build. And most importantly, the type of load it will drive. This is a critical point.
 
To answer your question regarding this last point: the headphone output has totally different requirements from the line out, so it's no surprise Oppo built it differently. Compared to the line out, the headphone out has to deliver 10,000 times more power to 500 times lower impedance with potentially wild impedance vs. frequency fluctuations. The differences in the way these two stages are designed & built don't necessarily have anything to do with one giving better more transparent sound. In fact, delivering and dissipating that kind of power forces them to make design choices that could make it slightly LESS transparent than the line output.
 
Whatever differences one hears using the headphone output versus the line out may disappear in a level match double-blind test. And even if some listeners can differentiate them in a level matched double-blind test, there's no way to attribute those differences to discrete components or class A operation. In fact, even if some listeners can hear the difference and consistently prefer X over Y, it doesn't necessarily follow that X is better than Y in any objective sense. X might be better than Y, yet it is just as likely that X has some euphonic distortion that the listener likes.
 
In short, one cannot infer anything about objective quality from subjective preferences or from A/B tests. Nor can one infer that the differences in the way the two stages are designed & built has anything to do with sound quality.

 

[MRC001]

 
Well my objective to control the volume at the amplifiers, and my issue is that the balanced amp has a maximum input voltage of 2.8V. So without this, there is significant distortion. 

 
2.8 V input to the HA-1 should be fine. The HA-1 specs on page 28 say the XLR input accepts up to 18 Vrms. The RCA input accepts up to 9 Vrms.
 
As for output, the HA-1 XLR output will vary from 0 to 4.6 Vrms, depending on the position of the volume knob.
 
The HA-1 should work just fine in your situation so long as you don't use bypass mode, and don't turn the volume up too high.

 

[MRC001]

  well since the site says it has >120 DB my uneducated guess would be 0.552 for 10 db , 0.828 for 15 DB and 1.104 for 20 DB but be warned that's just a calculated guess and I would certainly contact Rothwell for correct figures on that Pancakes if the voltage is critical for you. 

Assuming they're measuring their attenuation dB as voltage, not power:
 
Vdb = 20 * log(V1 / V2)
So:
-10 dB would be a voltage ratio of 3.16:1, for example 1 V drops to 0.32 V.
-15 dB would drop 1 V to 0.18 V.
-20 dB would drop 1 V to 0.1 V.
 
Use the least amount of attenuation you can, to keep the voltage as high as you can, to keep the S/N ratio as high as possible.