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Old 7th March 2013, 08:43 PM   #1811
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Talking Rambling on

Quote:
Originally Posted by qusp View Post
what makes you think you need a preamp? better to just install a decent ADC in front of the dac IMO.
The thinking behind using a pre-amp stage was the planned use of an ODAC [again], which requires a minimum of 5K Ohm load [higher the better]. Thoughts were ODAC > 10K Ohm Alps RK27 pot > The Wire se-se, in one chassis and The Wire Power Amp in another.

To eliminate the pot, I could alter the input resistors on the se-se and control volume through software...

Currently, not sure on the input Z on the Power Amp in SE AC coupled configuration [not asked / looked], but if it's close to the balanced 600 Ohm [think it was that], then ODAC won't be a happy bunny directly feeding the P A. Hence the intended use of a pot & Wire se-se HPA.

Hopfully, any The Wire DAC will be P'N'P with the rest of The Wire range, or only require a small alteration of the recipient device. Owen?

Sorry if OT...

Paul
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Old 7th March 2013, 08:54 PM   #1812
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Your going to tell me to up the values of R44 & R46 on the PA's + input to compensate for the higher load requirements of the ODAC aren't you. I just know you are ...
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Old 7th March 2013, 11:58 PM   #1813
opc is offline opc  Canada
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Originally Posted by BuildMeSomething View Post
Your going to tell me to up the values of R44 & R46 on the PA's + input to compensate for the higher load requirements of the ODAC aren't you. I just know you are ...
Nah! Input impedance is close to 6k for an SE setup on the power amp, so you should be fine as is. Only in balanced config does it dip down a little lower.

You "could" swap out those resistors and instead use the ones intended for the balanced setup to increase the input impedance to over 30k, but I would hope that any modern SS preamp or DAC would be happy driving the 6k load you have now.

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Owen
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Old 8th March 2013, 12:06 AM   #1814
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you could yes, we went through that in the NTD1 thread. no I simply thought you were talking about Owens dac, which I presume is ESS and will use (optionally) digital volume
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Old 8th March 2013, 09:28 AM   #1815
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Cheers you two Near 6K for the SE version would be fine but don't think the ODAC would be performing at its best. Most of NWAVGuys tests were done with a 100K load, though still not bad into a 10K load.

I'll hunt down and read through the NTD1 thread... more knowledge is always good.

However, with the advent of some new offerings from Owen, it'd be very silly of me to be spending my money else where at the moment.

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Old 8th March 2013, 06:18 PM   #1816
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Hi Owen, I hope this will be helpful for those of us who manually solder SMDs. I built the SE-SE and although it was an awsome unit, the SMD footprint could get a slightly longer pad to make our life much easier. PCB design is part of my job at work and most our boards are subject to manual rework/customization. We use slightly larger footprint than the standard size recommended and ensure SMD pads have a 0.5 - 1.0 mm hang-over beyond the soldering end of the parts. Taller parts get a bigger oversize than thinner parts to ensure soldering tip easy access. The reason being is that a correct manual SMD soldering technique requires the soldering tip to make contact on the pad, not on the part, for a quality, reliable soldering joint. A larger footprint will also help prevent components being populated too closely to each other end-to-end, leaving a room for easy rework or touch-up.

However, if your new design is intended for reflow only, the footprint on SE-SE should be fine.
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Old 8th March 2013, 11:20 PM   #1817
Zsubbo is offline Zsubbo  Hungary
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Originally Posted by opc View Post
You certainly could, but you may need to solder a 10k resistor in parallel with the cap on the VCOM pin to ensure the output common mode voltage is 0.

If you do that, then there's no reason you can't take a single phase of the output (with reference to GND) to drive a pair of headphones.

You should definitely not ground the unused output however, as that would be the equivalent to a dead short for the buffer.

This arrangement will have higher distortion and noise, so I would instead suggest the use of a BAL-SE or SE-SE amp

Cheers,
Owen
Firs of all, thanks for the prompt response !

The reason why I would want to use it like this, is because I have an AKG K1000 and some Grado headphones, so I could use both with it.

I'm cant make up my mind witch amp to build, I'm torn apart between the Wire amp, and between the Gilmore dinahi, any help would be appreciated on this part
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Old 8th March 2013, 11:31 PM   #1818
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pretty different amps, Kevin definitely knows his discrete design and tries to make sure things measure well (comes from working with gigawatt lasers and masers at work I think...) they are very different philosophies, but I prefer the wire, cheaper and smaller too. no question the wire measures better, but I prefer the SQ as well
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Old 8th March 2013, 11:35 PM   #1819
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Quote:
Originally Posted by nattawa View Post
Hi Owen, I hope this will be helpful for those of us who manually solder SMDs. I built the SE-SE and although it was an awsome unit, the SMD footprint could get a slightly longer pad to make our life much easier. PCB design is part of my job at work and most our boards are subject to manual rework/customization. We use slightly larger footprint than the standard size recommended and ensure SMD pads have a 0.5 - 1.0 mm hang-over beyond the soldering end of the parts. Taller parts get a bigger oversize than thinner parts to ensure soldering tip easy access. The reason being is that a correct manual SMD soldering technique requires the soldering tip to make contact on the pad, not on the part, for a quality, reliable soldering joint. A larger footprint will also help prevent components being populated too closely to each other end-to-end, leaving a room for easy rework or touch-up.

However, if your new design is intended for reflow only, the footprint on SE-SE should be fine.
I know what you mean, I have suggested the same with the clearance for vias and planes. however i've found a chisel tip allows contact with the pad, the power supply boards on the 1210 size caps and the inductors were the worst in this regard. of course it will add somewhat to the inductance
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Old 9th March 2013, 12:13 AM   #1820
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Quote:
Originally Posted by qusp View Post
I know what you mean, I have suggested the same with the clearance for vias and planes. however i've found a chisel tip allows contact with the pad, the power supply boards on the 1210 size caps and the inductors were the worst in this regard. of course it will add somewhat to the inductance
Agreed... the close proximity non-tented vias were not the best idea. Any future DIY targeted boards will be more friendly to solder

I'll look into increasing the pad size a little bit, but I don't want to go overboard as the parts will no longer fit in reasonable proximity to one another.

As qusp mentioned, using a chisel tip makes for very easy soldering of the 0805 parts with the current pads. The only aspect I found challenging was some of the vias being too close to the pads, and un-tented.

Cheers,
Owen
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