[Lvivske]

I have an issue with pre-amp and EQ noise on a couple setups and thought in-line RCA attenuators would be the solution to try. I'm building some cables and thought DIY'ing my own or building them into the interconnect cables would be the perfect solution. I figured either -6db or -10db might be the sweet spot, as muting is -20db and a bit overkill and I just want to lower the noise floor and compensate by boosting signal from my DAC and/or volume pot because on both I'm basically stuck at 9-o'clock

One online guide says 6.9k ohm (signal) + 4.7k ohm (to ground) would work for -10db, and another guide on youtube suggested 6.8k ohm + 4.7k as well (or 5.6k & 10k for -6db), however, a guide on the Hoffman forums says use 56k & 22k(!) and an old thread on audiokarma said 47k + 47k (?)

What are the right resistor values to go with?

One amp is coming between an EQ and power-in, while the other is after the EQ in the tape loop. The second amp has a tape-input sensitivity of 150mV/47k ohm, and the EQ has an output impedance of 75ohms (stats)

bonus question: does the shielding on the input end go to ground? I've seen conflicting information online, where some say to only ground one end and make a cable directional "with a drain," while others say ground both ends "in the japanese style"

 

[enregistree]

Attenuation makes sense for vintage gear, or generally if you happen to have too much gain in the system…

I suggest that you add 4k7 in series at the load end of the cable
and 5k6 between signal and ground for –6dB
(use 6k8 & 2k4 for –12dB).

The math behind it can be done with online voltage divider and parallel resistors calculators.

The cable is directional (it will not attenuate when reversed) and the shield on the input end goes to the ground.

 

[Lvivske]

Attenuation makes sense for vintage gear, or generally if you happen to have too much gain in the system…

I suggest that you add 4k7 in series at the load end of the cable
and 5k6 between signal and ground for –6dB
(use 6k8 & 2k4 for –12dB).

The math behind it can be done with online voltage divider and parallel resistors calculators.

The cable is directional (it will not attenuate when reversed) and the shield on the input end goes to the ground.

thanks! I tried calculators but I was basically a monkey with a typewriter

I'll try out 4k7 + 5k6 (ground) and maybe buy a few more to try 5k6 + 10k (like the youtube guy suggested for -6db) as a backup

(so resistors on output end, 1 resistor to ground on the plug, cut the shield; and ground the shield on the input end)

 

[enregistree]

Exactly, like this:

 

[lantian]

The formula goes like this
V out equals to output resistor divided by summ of both output and input resistor and then multiplied by Input voltage.
Would always recommend going 10kohm resistor for signal and whatever is needed for shunt. For my luxman made a divider with 10kom input and 560ohm shunt to get around 160mv for it's input. Works like a charm. Generally suggest having input resistor close to 10k or more if possible to prevent any kind of roll of on either end of frequency spectrum.
If your input sensitivity is 150mv that's what you should aim for. For that would recommend a 1k shunt resistor and 10k input you'd get around 180mv going into your amplifier.

 

[Lvivske]

I may try that on a second set, right now trying the 4k7 + 5k6(gr) enregistree suggested on one amp and it did a great job at knocking out the noise generated by the Schiit EQ without compromising the frequency response. (kinda hard to swap cables around and come back to compare, so hot swapping between one amp with and one without and both sounds equally normal)

On the other amp I wanted to try these on though, it wasn't strong enough, so may need to up the resistance but its not much of an issue in the first place

edit: after some further listening, i think the FR may be affected in a way, like it loses some vibrancy in exchange for that blacker background.