[oneplustwo]

Gotcha. That makes sense. Again, thanks for the education!

 

[oneplustwo]

Amb,

Sorry to resurrect this thread, but how would things change if I changed volume in the digital domain? Would I just follow the same wiring diagram you linked to but pretend the volume knob connections are just "shorts?"

 

[amb]

Yes, You could simply omit the pot and connect direct, but keep in mind that attenuation in the digital domain causes loss of bit-resolution.

Also, running the amp without a volume pot is effectly like setting it to max volume. You'll most likely suffer a loss of S/N ratio running the amp that way and rely on the source's volume control.

Lastly, not all sources have a volume control. Building your amp without a volume control will limit its usefulness with many sources.

 

[oneplustwo]

Thanks Amb,

I know there will be some bit resolution loss but I figure the Buffalo 32 (which will be my DAC) has plenty of bits to spare.

As for the S/N ratio, I hadn't thought about that. Do you think I would be better off using the balanced joshua tree attentuator and leaving the volume control (via volumite) set at maximum? My original thought was that there would be less noise with no attenuation and it would be a good thing. (I'm using the volumite because I want to be able to drive my headphones directly via the Buffalo.)

You're right though... maybe not having the flexibility to use other sources will ultimately drive me to throwing in the joshua tree after all. That being said, I don't really expect to use anything other than the Buffalo!

 

[amb]

You always get the best S/N ratio by feeding a "hot" signal into the amp and then attenuating it to the desired listening level within the amp. This means setting your source to max volume and control the listening level at the amp.

 

[askforwhy]

I found it is not possible to use unbalanced headphone while the input is balanced for 6-channel configuration by simple wiring.
Maybe not a big issue.

 

[amb]

Sure you can. The headphone's common ground-return will go to the active ground channel instead of the "cold" channels.

 

[askforwhy]

Oops, my fault. Ti you are right.

The wiring thing just couldn't keep me awake.

 

[DoYouRight]

Thank you! This was pretty helpful, I am in the process of a 6 board to be fed by a balanced buffalo32

I would like SE and Balanced as well. Basically copying KRMATHIS but with 6 boards so I have active grounds.

 

[johnwmclean]

Quote:

Originally Posted by DoYouRight /img/forum/go_quote.gif Thank you! This was pretty helpful, I am in the process of a 6 board to be fed by a balanced buffalo32 I would like SE and Balanced as well. Basically copying KRMATHIS but with 6 boards so I have active grounds.

Great balanced source, great balanced amp. Are you ever going to need or want to listen SE. Unless there's something I'm missing something, save youself money and time.

 

[oneplustwo]

Once again, resurrecting this thread. Got some more questions since I'm finally actually doing the wiring.

1. When wiring for SE output, would it be best to drive the both combo jacks from R+, L+ only? Or should I drive one with R+, L+ and the other with R-, L-? I think the latter makes more sense.

2A. Should the RCA input jacks be grounded to the enclosure or should they be isolated? I think they should be grounded to the enclosure based on having the sigma and toroids in a separate enclosure.

2B. Should I just connect the RCA and XLR input jack grounds together (to the enclosure)? Similar question for the combo output jacks? Should the XLR pin 1 be grounded with the TRS jack "S" pin and then to the enclosure?

3. The schematic Amb has shows where all the board input signal wires go but how about the board input ground wires? For the wires that go to the volume control, I can just connect them to the ground terminal block of my TPA joshua tree attenuator. But I'm a little confused as to what to do with the ground wires when they go to the switch. I think I can just connect them to the same ground terminal block on the attenuator.

 

[amb]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif 1. When wiring for SE output, would it be best to drive the both combo jacks from R+, L+ only? Or should I drive one with R+, L+ and the other with R-, L-? I think the latter makes more sense.

Just drive them both with the L+ and R+ signal (daisy chain the wires). There is no good reason to make one of them phase-inverted. If you're worried about the amp's ability to drive multiple headphone loads, then stop worrying.

Quote:

2A. Should the RCA input jacks be grounded to the enclosure or should they be isolated? I think they should be grounded to the enclosure based on having the sigma and toroids in a separate enclosure.

This is clearly shown in the "Wiring & ground" section of the β22 website. The example is a 3-ch active ground amp, but a 4-ch balanced one is no different.

Quote:

2B. Should I just connect the RCA and XLR input jack grounds together (to the enclosure)?

Yes.

Quote:

Similar question for the combo output jacks? Should the XLR pin 1 be grounded with the TRS jack "S" pin and then to the enclosure?

Balanced headphone outputs do not use the ground pin (pin 1) at all, so you don't have to connect it. But if you want to, it won't hurt, just daisy-chain it to the TRS portion's sleeve contact.

Quote:

3. The schematic Amb has shows where all the board input signal wires go but how about the board input ground wires? For the wires that go to the volume control, I can just connect them to the ground terminal block of my TPA joshua tree attenuator. But I'm a little confused as to what to do with the ground wires when they go to the switch. I think I can just connect them to the same ground terminal block on the attenuator.

Yes, just connect them all together via a daisy chain and goes to each board's input terminal grounds.

 

[oneplustwo]

Success! Sort of...

When I plug in my SE headphones, the volume control works but at soft levels, it takes a lot of movement to create a difference. Conversely, at the higher levels, it takes very little movement to create a significant difference. There is very little to no background hum.

When I plug in my balanced headphones, the volume control doesn't do anything. Also, I notice significant hum (which changes if I touch the enclosure.)

Anyone have any bright ideas?

 

[digger945]

First idea, grounding. If your using a SE source, and based on what I read you say in post #26 do you have the RCA inputs connected to the amp case or the pcb ground?
Notice how the grounds are connected in the schematics on amb.org.

 

[amb]

oneplustwo, please draw and post a diagram of exactly how you wired everything up, or post some very clear pics.