Problem with Attenuator to Audio-Gd ref 7

[Jsgraha]

I've just received an attenuator 15db - 75ohm (made by minicircuits) to be used with my AP2 and Jkenny MK3.

 

Before receive this attenuator, I used either one of the converter connecting directly to Audio-GD ref 7 using bnc connector.

Everything works fine, using jplay 5.1 as computer player.

 

However, when I introduce this attenuator between ref7 and AP2/MK3, there's no sound.

Ref7 couldn't lock the signal from the converter (usually, if the signal was locked, there's a click).

 

I also have an nfb-12 amp/dac that I used to bring when travelling.

When I introduce the attenuator between dac and converter, nfb-12 can lock the signal.

 

I'm fine using ref7 connecting directly with the converter, but I'm curious with the reason of this, actually.

Hopefully not the sign of my ref7 start to winding down (since I love this dac)

 

 

[lebowski]

sounds like too much attenuation and your DAC not locking onto the signal. I use even higher level - 21db RF attenuators (mini-circuits) between a JK hiFace Mk2 and Audio GD Ref 5 DAC with no problem, however I did get intermittent loss of signal lock when I tried this with a Lavry DA10

[davewantsmoore]

I'm curious with the reason of this, actually.

 

You are attenuating the signal too much for the DAC to receive.

[Jsgraha]

Thank for the feedbacks.

So if I would like to try further (using attenuator), should I go with higher or lower db ? (15 db atm).

[lebowski]

Lower, I would try - 6db. Before you do that try switching the DAC on and off while you have signal going to it, you might find it locks on.

[Nada]

Why attenuate at all?

 

The HiFace-1 was way above SPDIF voltage spec and so attenuation made sense

 

The AP2 / HiFace2 /JKmk3( Wolfson WM8804 SPDIF) put out the correct voltage signal.

 

Its predictable using a 15dB attenuator blocked the signal with a large decrease of voltage down to about 18% taking the signal below triggering the receiver.

 

An attenuator can filter some troubling reflections however with an in-spec device there will be smaller reflections anyway and an attenuator isnt going to do anything for reflections between the DAC SPDIF receiver-internal SPDIF wiring-DAC BNC socket-attenuator.  If you still want to experiment a -1db 75ohm attenuator would be a safer place to start but depending on the setup may still cause drop out.

[Jsgraha]

Thanks for the comments.

Basically, I just would like try different route between the converter (mk3 & ap2, also the incoming Ciunas which will ship with the same 15db attenuator) and ref7, using either direct inject or 15 cm bnc cable or using attenuator.

I think at this stage, I might avoid using attenuator as I can't find a good 1/ 6 db attenuator. Jaycar sell 6db, but the person at the store was unsure whether it's 50 or 75 ohm.

Is anyone know the supposed optimum length of bnc cable between converter and dac?

[gavtron]

I have been trying to help Jo out with this issue.

 

I sold Jo my old ref 7 which he is currently using.

 

When I had it, I was using the following setup: JKSPDIF Mk3  -> 15db attenuator -> BNC Male to Male -> direct into the BNC port on the back of the ref 7.

 

It worked fine and I preferred the attenuator in the path.  

 

I'm scratching my head as to why the setup worked at my place with the same gear, but not at Jo's.. The only variable I can think of is that the mk3 Jo is using is an older one with a switch at the front, and mine has 2 power buttons on the front instead of the switch.  Apart from this I think they're meant to be the same.

 

cheers,

 

gav

Edited May 14, 2013 by gavtron

[davewantsmoore]

I have seen the situation where a certain attenuator was too much for high sample rates.... but lowering to 44.1khz worked.   Try that for science.

 

If it works with no atenuator, just do that.... there's no shame in not using one... and like nada said, there no certainty they will work, depending on the device.

[Nada]

the mk3 Jo is using is an older one with a switch at the front, and mine has 2 power buttons on the front instead of the switch.

 

do they both have the Wolfson WM8804 doing SPDIF out?

[gavtron]

I think they are meant to be the same but not 100% sure.

[Jsgraha]

Really enjoy your (or mine now) ref7 Gav. It's something special

Thanks for selling it to me (and your help as well)