Pass D1 I/V for TDA1545

[AudioLapDance]

I've been playing with my old Zen Revised as a mid/tweet amp and love its sound and simplicity.

Since simple is what simple does ... why not pair my simple DACs (TDA1543, 1545) with a simple I/V. Like peas and carrots!

There are a couple of D1 1543 threads but few regarding the 1545.

The Pass D1 For Tda1543

The 1545 problem is a 1-2 punch. It has low I fs (1mA) and a high voltage at the output (3-4 V). This eats up the positive rail swing if biasing the IRF610 at 8-10mA (recommended?)

The original D1 had +-30V, Vs=0V, I=9mA (30 V across 3.3k Rs), and Vd=16.5 (+30V - 13.5V (9mA through 1.5k Rd))

The D1 PCM63 outs 2mA but the 1543 only 1mA. So Rs goes up from 1.5k to 3k to keep the 3Vp output (no buffer at this point just the I/V). But 9mA through 3k is 27V and that's most of the + rail (especially when Vs=4V for 1545!)

Hmmm, what to do? A larger + rail? That's a pain ...
And then I just happened to glance at the old Bride of Zen preamp ...

http://www.passdiy.com/pdf/brideofzen.pdf

It has Vs=4V, perfect! And enough swing to handle the larger Rd=3k, perfect! Just use the bias setup from D1, up the resistances to keep the relative voltages (Rs from 100 to 300, Rd from 1k to 3k, which lowers the bias to a still hefty 12mA) The single 60V rail is easy enough to make from dual 15V secondaries ...

Would this work? Work well? The main difference seems to be the lower resistance at the source of the FET (3.3k for D1, 300 here)? Any comments/feedback?

Any other ideas for a good 1545 D1 I/V?

Cheers,
Jeff

[oneday]

Hi Jeff,

Maybe head over hear, new i/v board imminent that has been the labour of love of several dedicated folk over the past few months.

http://diyparadise.com/forum/index.php?board=5.0

From all reports it turns the very good Monica TDA1545 NOS-DAC into something very very special. I have Monica 2 and the USB version, but gave up trying to keep up with the pace of i/v mods that incl resolving high output impedance by use of an integrated NP B1 buffer stage. Glad to wait now for the revised i/v board to appear to transfer components into, will be much neater.

cheers.. od

[marc brown]

Originally posted by oneday
Hi Jeff,

Maybe head over hear, new i/v board imminent that has been the labour of love of several dedicated folk over the past few months.

http://diyparadise.com/forum/index.php?board=5.0

From all reports it turns the very good Monica TDA1545 NOS-DAC into something very very special. I have Monica 2 and the USB version, but gave up trying to keep up with the pace of i/v mods that incl resolving high output impedance by use of an integrated NP B1 buffer stage. Glad to wait now for the revised i/v board to appear to transfer components into, will be much neater.

cheers.. od

Is the Monica available in a kit form?

[spgjmf]

I just made a jfet boz for my 1543 nos dac...it is magic and works on +12, same as the dac. 6 componets...pretty neat ....

searchf ro jfet BOZ.

good luck,
Jeff

[oneday]

Marc,

I think Yeo gave up on the kit idea, to many build problems, so he doesn't advertise them anymore. Not that he doesn't have them. Anyway, with the new i/v board about to be released, I'm not sure how he'll deal with the DAC side. Best ask him directly.

cheers..od

[oneday]

How's the Monica/Rudolf/B1 NOS dac build going?

Hi jh,

Have been busy upgrading OB speakers and building a capless B1 (fantastic BTW) so have been watching the frenzy of Monica modding from the sidelines, and collecting parts for when the new i/v board is available. Somewhat a newbie to DIY, fun stuff though particularly with forums like here with folk so willing to share their wisdom.

cheers.. od