Valab NOS DAC - subjective listening and modifications - Page 100

doesnt answer your question ernst, but some info on coupling caps

ecp.cc

well depending on the input impedance of your amp you may not be able to do without output caps. they the .1uf input caps will protect against DC, but they may not be enough capacitance to prevent intermodulation/roll-off

MikoLayer- my pcb is blue, the layout is very similar to the red one in the current pictures of the luxury model version on ebay. I am guessing i should just measure the voltage on those resistors you pointed out and use one that is +3.3 volts,

Thanks for the link Wood. A bit of information on that page did manage to answer my question. The capacitor value on the preamp input is related to the input impedance of the preamplifier, that is probably why it is so small. Knowing this, i am encouraged to just bypass the valab's output caps with a bit of wire to see what happens. Can anyone tell me what intermodulation rolloff is?

Give it a try ernst, but if you hear very unpleaseant non-harmonic distortion, then you have intermodulation. If the bass is very thin, then you have roll-off.

actually it would be VERY unusual for your preamp to have an input impedance large enough to avoid rolloff and intermodulation. VERY unusual indeed. the input impedance of your preamp is much more closely tied to the value of the pot it uses.

I am curious now errnst, as to what type of preamp you have?

anyone know what happend to the chamelon thread?

Given inspiration from Pat and further assistance from rhodes54 and his schematic here, I have managed to find property on my 1st Gen PCB for new Wima input caps and the Lundahl LL1572 digital input tranny. With a little benderoo action, I was able to make these connections cleanly. The two empty pads in front of the LL1572 are waiting for a 75R Texas Comp Resistor, which I am still waiting for. For now, I have left the 100R stock SMD resistor below.

Kids are sleeping and wife is in bed reading, so I have only about 10 minutes of lower level listening from a cold Valab and still colder tube amp but my immediate impression is that this is probably the best investment of $25 on audio yet. Clean, no grunge, extreme focus, a melding together of the sound field without losing the stereo separation and air between the notes. Highly recommended.

group buy w/o following HF rules = delete

I'm assuming, anyway.

Nice work mrdon, are you going to use a LL1572 at your source as well?

my preamp is Conrad Johnson PV3

Hi errnst, is this your preamp?

The Free Information Society - Conrad Johnson PV3 Electronic Circuit Schematic

I can see those 0.1uf caps your refer to, are they for certain, input caps, as in dc blockers, they look more like bypass caps?

Thank you!

I am sorry but I don't understand your question. Do you mean from my MacMini?

Hi, mrdon, if its coax out then why not, give you more isolation etc, if there's room in there.

wood, there isnt much point in correcting twice IMO. besides hasnt the mac mini just got optical out? I would assume he is using some sort of USB to coax convertor. could be wrong but I still see zero benefit in transforming to 75 ohms at the mac and then again at the dac. just sounds like a waste of money to me