Re-boxing SB2

[Patrick Dixon]

I'm think about re-boxing my modified SB2 in a metal (ally) box. I will probably ground the box (although I suppose I don't have too since there are only low voltages involved), and I'm wondering what effect this will have on wireless reception. Obviously the external antenna will be unaffected, but there's an internal one too.

Anyone got any thoughts or experience they could share?

Is the existing (plastic) box zinc sprayed, since that seems to work OK?

[seanadams]

I'm think about re-boxing my modified SB2 in a metal (ally) box. I will probably ground the box (although I suppose I don't have too since there are only low voltages involved), and I'm wondering what effect this will have on wireless reception. Obviously the external antenna will be unaffected, but there's an internal one too.

Anyone got any thoughts or experience they could share?

Is the existing (plastic) box zinc sprayed, since that seems to work OK?

The antennas won't work in a metal box. It should work fine with a single antenna though.

You could also look into getting some "pigtail" cables to bring the connector(s) our to the back panel.

The connection on the card is called "MMCX" and the back panel is called "SMA" (reverse polarity SMA to be specific). Some googling should turn up a few choices as these cables are used a lot by antenna hackers.

[seanadams]

Sorry, meant to say "UFL", not MMCX for the internal connector (MMCX was for SB1's 802.11b card). UFL is also known as IPEX.

Something like this should work. Just drill a hole and screw into the back panel:

http://www.netgate.com/product_info....roducts_id=144

[Patrick Dixon]

Sean, many thanks.

If I ever get it done I will post some pictures for you. I have made a few mods to the audio circuitry though, and comparing it to the standard SB2 is like chalk and cheese. Decent though the standard SB2 is, the mods make it a real giant-killer. Shame you're not closer or you could come for a listen! (Plenty of room for parking here).

[Robin Bowes]

Patrick Dixon wrote:
> Sean, many thanks.
>
> If I ever get it done I will post some pictures for you. I have made a
> few mods to the audio circuitry though, and comparing it to the standard
> SB2 is like chalk and cheese. Decent though the standard SB2 is, the
> mods make it a real giant-killer. Shame you're not closer or you could
> come for a listen! (Plenty of room for parking here).

Patrick,

Care to share with us what you've done?

R.

[Patrick Dixon]

Robin,

I sprinkle loads of fairy dust on my soldering iron tip and then get stuck in

I'd say my mods fall somewhere between the simplicity of the Red Wine Audio mods and the butchery of the 'hacksaw' approach. I've reworked the PSU (using Andy Weekes' fabulous SuperRegs), the clock and the output op-amp, and upgraded some of the component types. I need to rebox it now, so that it's in two matching boxes.

If you're in the UK and reasonably located wrt Bristol, email me and maybe we can arrange a listen.

firstname dot lastname @at-view.co.uk

[Robin Bowes]

Patrick Dixon wrote:
> Robin,
>
> I sprinkle loads of fairy dust on my soldering iron tip and then get
> stuck in

Heh.

>
> I'd say my mods fall somewhere between the simplicity of the Red Wine
> Audio mods and the butchery of the 'hacksaw' approach. I've reworked
> the PSU (using Andy Weekes' fabulous SuperRegs), the clock and the
> output op-amp, and upgraded some of the component types. I need to
> rebox it now, so that it's in two matching boxes.

I have about 4 SuperRegs that I had intended to use on my Art DI/O ADAC
but having heard the SB2 I've decided that I'd be better of using them
in the SB2.

What have you done to the PSU? I seem to remember, from some schematics
Sean/Dean posted, that a couple of SuperRegs would do the trick - one
for the DAC and another for the output stage. Although, I'd probably
take the audio out directly from the DAC chip and bypass the opamp.

And the clock - I thought the SB2 has remarkably low jitter. Did you see
much improvement after the clock mod? What have you done to the clock?

> If you're in the UK and reasonably located wrt Bristol, email me and
> maybe we can arrange a listen.

Well, I'm in the UK but alas live just north of York so Bristol is a
little out of range!

Cheers,

R.

[Patrick Dixon]

I have about 4 SuperRegs that I had intended to use on my Art DI/O ADAC
but having heard the SB2 I've decided that I'd be better of using them
in the SB2.

I've only used one - but I'm going to try two next.

What have you done to the PSU? I seem to remember, from some schematics
Sean/Dean posted, that a couple of SuperRegs would do the trick - one
for the DAC and another for the output stage. Although, I'd probably
take the audio out directly from the DAC chip and bypass the opamp.

I'm still using the opamp - although not that exact type!

And the clock - I thought the SB2 has remarkably low jitter. Did you see
much improvement after the clock mod? What have you done to the clock?

Jitter can never be too low - see Sean's post for some hints.

Well, I'm in the UK but alas live just north of York so Bristol is a
little out of range!

Shame - if I'm ever heading that way I'll let you know.

[Robin Bowes]

Patrick,

Sorry if this sounds a little blunt...

I could keep replying, asking for ever more detail, but you seem to be a
little reticent.

Would you care you share with us what you've done, or do you have
reasons not to do this?

Thanks,

R.

[Andrew L. Weekes]

I think the SB2 would be worth your attentions, mine is sounding bloody marvellous at present, to the point I now feel it's little different, and possibly slightly better, than my main CD player (which cost a 4-figure sum)!

Having heard Patrick's last week, with super-reg's installed it sounded amazingly good.

This is all still without actually using any of my super-reg's (yet) in mine as I need to do a re-box to allow this, I do have one used as an external linear supply replacing the standard wall-wart though.

The things I've done to mine, in some approximation of sonic importance are: -

1) Added a linear regulator (3-terminal at present) to the 'HCU04 (currently fed from the internal 14V)

2) Disabled the 12MHz clock and the SPDIF from the 'HCU04

3) Routed the clock directly to the DAC

4) Added an external linear supply (5V)

5) Changed the analogue decoupling electrolytics for polyester film caps (with 0.5R in series)

6) Changed the output op-amp for an AD8066

7) Re-jigged the o/p stage to be a 2-pole Bessel filter and using polystyrene caps in place of the ceramics

8) Changed the coupling electrolytics between DAC and op-amp and op-amp o/p for Elna Silmics

9) Changed the op-amp bias voltage decoupling for a film cap

1-4 are by far the biggest winners in my view, and I'm certain there are large gains to be had from much better reg's all around, my intention being to replace all the analogue supplies with super-reg's (14V, 5V, 3.3V) once I get the box drilled and ready to receive the SB2!

I'll then examine whether the internal switchers cause any problems, now they are isolated from the critical analogue /clock functions.

Andy.