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This is my first post on the forum and my first foray into building an amplifier from modules. Will the Buffalo 3 provide me with 8 channels of balanced voltage output when used in voltage mode?
I am just getting ready to build an 8 channel amplifier based around a miniSharc from MiniDSP, the Buffalo 3, and some Hypex UcD amplifiers. I plan to use the Buffalo 3 without an I/V and connect the DAC directly to the amplifiers. I am hoping that I can use a single Buffalo 3 to get 8ch of balanced output.
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You can, but you will want to use a simple low pass filter to help keep up the natural quantization noise from the DAC. This filtering is built into our output stages, but you will need to add it yourself.
Also you will need to remember that the output will have VCC/2 common mode DC - so you will likely need AC coupling with either a capacitors or a transformer.
Cheers!
Russ
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No caps are required if you are using the standard UCD modules. There are caps on those already.
P.S. I think you'll like the IVY3 with modified UCD modules better than the other way around.
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Just want to chime in. Way back (way back!) I tested my UcD180 with a high-offset source. It resulted in power supply pumping. The caps on the UcD are between input amplifier and the modulator - as far as I know the circuit. Correct me if I wrong. Edited by user Sunday, February 16, 2014 6:44:08 PM(UTC)
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Bruno himself mentioned input caps on the retail UCD's (not the OEM's, those might be different) and no input caps on the nCore modules. For the time being I'm going with what he said, as he designed them.
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Thanks for the super quick response, Russ, and thanks for the additional input.
I had intended to put a simple RC filter before the amplifier (this is something I am familiar enough with), but was unaware of the need for any additional circuity. Do I need to be concerned about AC coupling with the UcD modules?
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I have similar plans as comiezapr. MiniShark DSP plus Buf3 in 8 channel config. I'm curious to hear if you (comiezapr) got it to work?
I'm also playing with the thought of using the voltage output mode of the BUf3 but there are a few things that are not clear to me:
1. How do you configure the Buf3 for Voltage Output mode?
2. Where will the voltage outputs be available?
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I haven't had the time to put everything together and have a listen yet so this is not absolutely confirmed information. Hopefully in a week or two (or three, or four) I can finish my project.
The choice of voltage mode vs current mode isn't some setting on the board, but just a choice of what output stage to use after the DAC. For my purposes I am pulling the signal off the headers on the board, using an RC filter on each output (2 RC filters per channel because it is balanced, for a total of 16 RC filters), and then using an AC coupling capacitor on each output. In my case the AC coupling capacitor is built into the Hypex amp module (confirmed by Hypex) so I really just use an RC filter.
As a direct response to your questions:
1) You do nothing to configure the Buf3 for voltage output mode. Just be sure to filter and AC couple the output before it hits your amplifier.
2) The "voltage outputs" and "current outputs" are the same outputs: the well labeled pins on the Buf3.
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Cool. Thank you
I'm eager to hear about you project. Can I ask you about the RC design. What is the fc frequency and the R and C values?
I’m also curious to know if there are any problems with the I2S connection between miniShark and Buf3.
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I'm planning to do a low pass filter at around 80khz. This might change though, so I'll give the details when I can actually confirm it works and sounds good.
There have been a few other folks that we're able to connect the miniSHARC with the Buf3, so I expect no problems there. The pinout of the miniSHARC is well documented. The real issue for me was that the inputs to the miniSHARC were limited so I additionally have a miniDIGI. Using the miniDIGI + miniSHARC + Buf3 complicates things slightly because you need to make your own cables.
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