Instrument signal muffled. Am I misunderstanding the chain?

[seablade]

Note that you do need a XLR to RCA (or whatever the hifiberry has) adapter along with this.

Not according to the spec sheet linked. You need to connect the XLR to the ‘5’ Header as I mentioned above, which is set up to accept balanced connections according to that spec sheet.

    Seablade

[seablade]

And now replying to myself, their Spec Sheet isn’t completely clear honestly so I may have to eat my words:

5 Connector for balanced input (P6)

INPUT CONNECTOR P6

This allows you to connect an alternative input connector.

1	right +
2	–
3	GND
4	–
5	left +

So it says it accepts balanced connections, but their pinout is for unbalanced, so it isn’t completely clear.

EDIT: And reading their article on connecting dynamic microphones seems to indicate it does not support balanced connections:

Stage microphones usually come with a balanced XLR output. The DAC+ ADC does not support this out-of-the-box.

     Seablade

[x42 (Robin Gareus)]

If you want to go the full DIY route, a suggestion from drwhat on #ardour IRC: http://wiki.diyrecordingequipment.com/projects/categories/di/

[Reuben (Reuben M)]

I would STRONGLY recommend not touching Behringer DIs with a well insulated pole.

While Behringer has released some usable products recently, their DIs were so notably bad in the past that I would not even use them for skeet shooting.

The DI I linked to is still considered one of the ‘cheaper’ DIs but is a workhorse you will find on most stages.

   Seablade

This. x10. Behringer DIs are trash. All kinds of ground-loops and buzzing that no lift switch will ever fix. If anybody is looking for really nice DIs and is willing to spend money, I highly recommend the BSS AR-133 and the Countryman Type 85 FET. But the IMP-2 Seablade mentioned works just fine. It sits in the sweet spot where budget and quality cross each other, sort of like the SM-58, so it acts as a baseline that other DIs are compared to.

[x42 (Robin Gareus)]

Keep the context in mind. @ardour_fa3cv is building an inexpensive “play along” system for bedroom guitarists.

Smashing Pumpkins - 1979

Thingamagig = FOSS guitar karaoke (with lights) No pedals. No amps. No knobs. No presets. No cost. Any guitar. Session: https://github.com/cyrusadkisson/thingamagig-smashing_pumpkins-1979 Red/blue police lights inspired by the video. Stratocaster for the closest tone, downtuned half a step. No loops or vocal effects, just an A/B tone switch in proper 90s alt style.

Rage Against The Machine - Bombtrack - Thingamagig demo

Thingamagig is my Ardour-based lighting and effects project. It standardizes everything (levels, MIDI, lighting, plugins, etc) so that, if your computer is configured to Thingamagig, all you have to do is download the session, plugin in your guitar and mic, and press play. No pedals. No amps. No external equipment. Just a guitar (and lights if you want them). This and more sessions here: https://github.com/cyrusadkisson

(and a couple more from https://github.com/cyrusadkisson?tab=repositories).

A Behringer device would likely not be the bottleneck, and it would still be expensive and over-sized compared to the rest of the components (RPi + hifiberry).

I hope the hifiberry developers deliver. This just needs a simple impedance-converter for the hifiberry. Realistically a hifiberry with Hi-Z will just need some additional resistor, capacitor, and matching the gain-stage. I don’t think you need a ground-lift or transformer at all.

[ardour_fa3cv (Cyrus Adkisson)]

Spoke with hifiberry. The #5 connector is NOT balanced. The datasheet is erroneous.

Edit: But a DAC+ ADC Pro version is in the works (fall release?) which will have a balanced input.

[seablade]

Edit: But a DAC+ ADC Pro version is in the works (fall release?) which will have a balanced input.

That is interesting, let me know what you turn up. Could be fun for projects such as the Zynthian for instance that Robin pointed me to in a different thread. Is this separate from the one with a High Impedance input for your guitar, or is it going to have both?

     Seablade

[x42 (Robin Gareus)]

zynthian mainly focuses on synths. MIDI in -> audio out. The first versions didn’t even have an audio-input.

[seablade]

Ahh good point, I had assumed Balanced Output there as well, but you are correct, that was a poor assumption on my part.

    Seablade

[mike3 (mike@overtonedsp)]

Meanwhile just inserting a 470kOhm resistor before the input, terminated with a 22kOhm to GND and ramping up the input gain by ~27dB will likely produce a better sound, compared to toying eith EQs…

You’re dealing with potentially very small signals already - so having to add another 27dB of gain just to overcome the passive attenuation and get back to the original level (actually this could be wildly off depending upon the input impedance of the soundcard, which we don’t know, but 10K was talked about) - may compromise the signal to noise significantly (unacceptably?).

Whatever the soundcard impedance (Rin) is, will effectively appear in parallel with your ‘R2’ of 22K. Something like:

1 / (1/R2 + 1/Rin))

There probably isn’t enough gain available in the ADC board to overcome the passive attenuation and also get to line level (and you might consider if the right place to be adding such significant gain - before any deliberate overdrive or additional gain effects - is a card supplied by power from a RPi).

These limitations also apply if you use ‘off the shelf’ passive DI boxes - the only difference being that now you don’t know what’s on the soundcard or in the passive box.

If you’re going to have to add external gain, why bother with the hack anyway - just do the design right with a suitable guitar friendly impedance to start with. Why not just wait for the custom DAC+ ADC board with the correct input impedance for guitar, rather than throwing away money on DI boxes or other hacks.

Does the wattage rating on these resistors matter? I’m seeing 1/4 w, 1/2 w, etc on amazon.

If you can burn out even a 1/4W resistor using a guitar pickup, you really need to change your playing style…