MLA

I can sort that if not already arranged.

Pots received. Thanks!

I was just wondering whether you just got lucky and escaped the system Payment sent.

Congrats! Enjoy

For all intents and purposes, that's exactly what just happened.

Or a diamond buffer or two ... (or are they better off separated?)

+1. The effort is highly appreciated! I'd be in for the SMD ubal->bal board and a pile of diamond buffers..

Possibly, but it's still fantastic!!!

Really looking forward to that!

Payment sent; shipping address in paypal note. Thanks!

Now it does. Thanks! Must have been the cache of my browser acting up.

Am looking at it but I don't see the input resistors (file diffinput3 right?).

Board files were posted yesterday and you have a working prototype today? Most impressive !!!

with reference to ground?

Cool, very nice that it's going the right way! And yes, since the circuit is inherently balanced, for unbalanced input you need to tie the negative input to ground, same as Dynalo. A prime hum suspect would be the routing of the wiring to the filament supplies. I remember on a tight KGDT build that the difference between hum and no hum was moving the filament cables one centimeter to the left. Literally. Good luck!

Found it; resistor values and hookup is in PSU schematic: Essentially you set up two voltage dividers, one between B+ and ground, the other between B- and ground, and then you connect these to the input and output filament supplies respectively. More info on heater elevation and hum: http://www.valvewizard.co.uk/heater.html. I did the artificial center tap thing they describe on my build to connect the reference DC voltages.

I think the two ohm resistor is fine; what I was referring to is referencing the heater supplies to other DC levels. i think JimL had a nice post on this earlier in this or the other SRX+ thread; I'll dig it out when I get home.

Don't know which PSU and trafo setup you have, but on my build I had to elevate the heaters to get it hum free. If you haven't already, I suggest you try that.

I've bought lambdas from zenmarket.jp. Good webpage and process.

Does 2.9 improve with the port mod?

Well, log audio taper is what I ordered and I'm pretty sure that's what we received. That said, while I've tested all pots I only checked the taper on the first few (which was log audio); the rest I tested for channel imbalance only. If you want to make sure yours is log audio, please remember to test it as a voltage divider (the ladder construction puts resistance measurements off the log curve). Hook it up to a small battery or similar and track Vout from the viper. Should it be the wrong taper, let me know and we'll sort it out.

Many thanks, that looks exactly like it! Did some more reading and that O2 mod seems quite similar to how the M3 bass boost is implemented. I have a spare Dynalo in the basement to experiment with; I will give this approach a try and see what comes out of it.

I did, and that works perfectly when I've got the place to myself and can turn up the volume. However, my social setting requires low volume listening more often than not. At those levels, I need a small bass boost to preserve balance. It's just for convenience; with a switch on the amp I would not have to walk over to the computer to change settings .

On a tangent; the HD800 sound brilliant out of the Dynalo, but I find myself boosting the bass a couple of dB most of the time for it to sound right to my ears. So far I've used digital EQ, but I wonder if someone has a recommendation for how to incorporate a small add-on circuit/daughterboard that could fill the same function inside an existing Dynalo build? I know there is a ton of circuit suggestions out there, but I'm not good enough at this to figure out what would work well with the Dynalo.

Well, with that I guess this GB can be considered complete. Happy building everyone! Should there be any problem with the shipments, let us know, and we'll try to sort that out as appropriate.