MLA

It's been discussed before, and the outlook is not so good...

On that theme, I got this very interesting link from @mdr30 http://www.monoandstereo.com/2016/11/direct-to-disc-brahms-cycle-sir-simon.html?m=1 I guess in purist terms; one processing step only, no mastering involved... https://youtu.be/qBf3OBMjRAg

Second that. Out of curiosity after Bob's Big Sound amp reviews, I built the M3 a while ago. Regardless of tweaking (bias and supply voltage levels, opamp choice), I can't describe it as neutral; to me it's a warm sounding amp. If the M3 was neutral to me, I can see how the dip which was a killer for Tyll would be noticable but ok to live with. However, I spent an hour with the LCD-4s last week, and in short; I'd buy something on Tyll's recommendation but not Bobs. Two great reviewers, but I hear it more like Tyll.

I don't have one in mine, and it does fine so far...

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.