Pars

I wasn't real clear on what the difference was between a pot and an attenuator in TKD terms. Are the TKD CP-2500s that you would buy from say Percy Audio here in the states a pot or an attenuator? I am guessing attenuator judging by the way the couple that I have ohm out rotationally? I hadn't ever noticed that they offer both under the same part #/series before this was pointed out. Sent from my iPhone using Tapatalk

What cases are those? Something like this?

Actually the input ground and output ground are the same (single ground plane). Same for the power ground.

Yes, board ground, should be the same anywhere on the board, probably the middle terminal on the 3-pin connectors.

This is a balanced Dynahi? That is one measurement (offset of O+ to O-). First, you should set DC offset for O+ to gnd and O- to gnd. Get these both as close as possible; should be able to get each to within 5mV without the servo. If you can't, get them as close as possible. Then check O+ to O-. Not sure what these boards have for pots on them. By going back and forth, you should be able to get them all pretty close. EDIT: and have the inputs either grounded or turn the volume pot all the way down.

I wouldn't solder it in, but I use good sockets. Your call however.

Yes, those look good. Are they 2-layer? You aren't home brewing more than that are you? (Don't even know if that is possible).

Yes, I obviously hadn't considered that aspect. My main use would be in front-end stages (Dynalo Mk2 mainly, maybe Dynahi as well). Those seem to have enough emitter/collector resistors / current sources that it shouldn't be a problem, particularly if the V devices were in the BL/V overlap range (high end of BL Idss). I'll look at things some more before I decide whether to get some or not.

Cool... Interested to see pics. Do you have a TKD CP2500 you can test fit, even a stereo pot? Sent from my iPhone using Tapatalk

BTW, I was curious as to why the BL grade of FETs seems to be more popular than the V grade, which has a higher Idss range? People seem to prefer BJTs with higher Hfe... Sent from my iPhone using Tapatalk Not sure what happened to the other post I wrote (on Tapatalk). Why is the BL grade favored over the V grade (higher Idss). In BJTs it seems as though the higher the Hfe the better... Sent from my iPhone using Tapatalk

He replied to me and does have V grade of both available. That fucking Justin And not really smiling happily either

Very cool! So that thing by itself can control the digital attenuator if you don't want to bother with display, etc.?

Anything going on with this? I would take 20 2SJ74BLs...

TO92s are easier than hell to remove. Heat all 3 pins up at once. Ohm them out. Did you verify all transistors with the low offset, presumed working board? Sure you don't have a PNP or NPN swapped or wrong?

Check all of the transistors. Include the SMT ones on the bottom. Something is out of place. Or blown.

Nice build George!

I sent an email to Context Engineering regarding their 6008H-8.5N case (8.5" long) and whether they could cut them to 6.8" (or 6.840") for this application. I have not followed up with them yet.

Also, I don't think you want the board to slide in the slots present in these cases, but instead want the board to not touch the sides. There are some traces (including AC) very close to the board edge.

Nice job! A piece of teflon tubing on the crossed leg might not be a bad idea though.

Happy Birthday Marc!

Thanks Kevin. I guess that interpreting your response is that yes, the GRLV plus would be better and lower noise than the shunt regulator. By invert stuff you are referring to Q14 (pos. regulator) and Q6 (plus current mirror Q1/Q3) and zener? I assume that, like your original dynalo supply, etc., that this is quieter than batteries? I'll source a GRLV Plus board and give this a shot. Not sure if I will buy Salas' board or not (since I would only be using the RIAA portion of it). I may still, though $52 is a bit steep, but it is 2mm / 3oz copper IIRC.

Were the transistors matched? If not, getting to 0V without the servo could get touchy. Even matched, it might not fall perfectly into place.

Output voltage for the GRLV would be 35V. I have 35V tants and also a few OPA445s. 35V rail seems to be what the phono stage uses. Question for those of you who know architecture/PSUs: do you think the GRLV at 35Vdc would be quieter and work better than the raw supply / shunt used for the Salas phono stage? I am guessing it would, but don't know shunt architecture/performance. Shunt shown below, fed by raw DC supply (bridge, 4700uf cap, pair of 10K resistors on output, ~ +45Vdc).

Happy Birthday Dusty!

Speaking of using a GRLV for higher voltages, if I wanted to do somewhere in the range of 40-50Vdc, where would I need to go for voltage ratings with the various caps, particularly the tants? 32Vac secondaries. Thinking that one of these may be lower noise than the raw PSU/shunt setup on a Salas folded phono stage. EDIT: more like 35V. Also, the stock R7/R10 are 1.5K. I noted Kevin saying he went back to 2K precision resistors here for his +/- 20V. 2K would make getting the 35V easier (2K / 4.99K) Sent from my iPhone using Tapatalk