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Look in the Stax thread for the current archive location. Sent from my iPhone using Tapatalk

OK I would measure them. Typ is 1.7V; max is 2.2V. We used to match LEDs for these, more important back when there weren't pots for offset. OK I've seen or heard of resistors being mismarked. Since you have the same problem on both boards, unlikely however (unless it is the whole batch of one value).

Doubtful that you fried any devices unless you connected the power backwards. When you say you replaced resistors with 340R, these were the 500R resistors? And those clear LEDs, have you verified their forward voltage as 1.7V with a meter? No PNPs where an NPN should be and vice versa? All resistors ohm out as their marked value?

Did a quick search back for copper weight and saw the 3oz recommendation. Ran across the special audiophool cable that blew up some poor guys actual KSA5 and found that those fucks are still in business! Revelation Audio Labs jeebus...

The PNP and NPN should not show low resistance (i.e., short) to each other. They will probably show some resistance, but I would assume it would be in the K ohm or higher range. None of the tabs should show a short to the L bracket. I couldn't tell in your pic what was under there or whether you had the shoulder insulating washers (such as Mouser 532-7721-7PPS). If the N and P were shorted together, you probably wouldn't be seeing approximately correct V+/V- (assuming the PSU was connected to the amp boards when you took your measurements), as they would be connected to one another via the shorted collectors. Just a shot from looking at the pics. EDIT: and I think Jose was asking if you had decreased the bias. Personally, IMHO, this amp is designed to run at 750mV/75mA bias, so that is what you should be running, and it shouldn't effect offset (i.e., you should be able to get the offset down into the sub 5mV range at that bias).

Very cool!

Should be the same... 0mV Sent from my iPhone using Tapatalk

What does V+ and V- look like? Also, with the amp off, set your meter to ohms and check continuity from each output device tab (tab, not the screw) to the heatsink. Also, check from a tab on one of the first 4 devices on the left to the tab of one of the 4 devices on the right side. Sent from my iPhone using Tapatalk

They should all be 0V, or very close. Ideally ~1mV or so without the servo. They will drift, so more realistically between +/-2mV or so, O+ and O- to Gnd. Inputs grounded or pot at 0. EDIT: looking at your picture above, what are you using to isolate the outputs from the heatsink bracket? Thermal TO220 pads are best for this; I would not depend on thermal compound for this. Also, it does not look like you have insulators under the screws for each device? The tabs on these are live (collector of each device) and MUST be insulated; whether you use nylon or PEEK screws, or steel screws like you are, but with the nylon step insulating washers. Sent from my iPhone using Tapatalk

Agreed, been watching it as well, and like it.

You probably should have something on there. Most people seem to mount them to the case bottom. On mine, which is uncased so far, I use a clip on heatsink like this:

sbeylo, it is the slots for the TKD CP2500 that you have to make sure they plate.

I ran some numbers yesterday at finer points and came up with this. I used a bench supply set for 1.007V (and had to adjust as I was running these to keep it there), feeding both deck inputs at once.. I used the same DMM on both sides (HP3468), moving the test clips at each pot position. I took the voltage from wiper to ground for each deck (V1, V2) and used 20 log(V1/V2) to calculate the dB difference. It was slightly above 0.5dB around the area that I was listening in (position 39). If I didn't do this correctly, let me know

Nah, he just said "that other forum" or something like that...

Happy Birthday Al! I hope you have a great one!

I'd adjust for max or close to the bias you are looking for (750mV??) and then measure ohms across the trimpot(s). Even though they are parallel to the 500R, you should be able to tell approximately what end of their travel they are at, and go from there as to what needs to be done.

Because of the 1k in series with the pot, the lowest you can go with the pot at minimum is ~333 ohms (1k || 500R). Normally, the 500R is replaced with a 620 or 680R because you can’t go high enough in resistance. It appears that on this amp, the problem is going low enough? If that is the case, replacing the 500R won’t do anything to solve this. I was looking at R23/34 because in the Ss Dynalo, there aren’t trimpot such as you have here. These resistor positions are what is used to change bias, unless I am not analyzing the schematics correctly. Sent from my iPhone using Tapatalk

I'll have to defer to those that have built this version of a dynahi as I have not.

No, not the ones by the trimpots (I don't think). This is the schematic I have; not sure where R23/R34 are on the board layout. I would definitely change out the 500R by the trimpots (R1 and R4 on the schematic) with the 620R or 680R. I see that there are 1K resistors in series with the trimpots; even so, you cannot get the effective resistance of 11K || 500R above ~478 ohms. With 620R, you can get it to about 586R. I wouldn't think that putting the OPA445 in should have the negative effects that you are seeing. dynahibalbjt.pdf

Had to refresh my memory on the original dynalo/dynahi. Yes, you should replace those resistors with the 620/680R to give yourself adjustment range. What do you have in for the bias resistors (R23/R34)? The schematic I have shows 100R, but I think most use 500R?

Mouser had the MJF15xxx parts in stock, but is out of the MJW2119x parts. Arrow has all of them in stock, and are reputable. I'm not sure if you could use the MJW21195/21196 instead (which Mouser does have in stock). I seem to recall Kevin saying those are fine. Looking at the datasheets for both, I can't spot any difference, but of course there must be something. https://www.head-case.org/forums/topic/12269-goldenreference-low-voltage-power-supply/?do=findComment&comment=732948

Yes, you're right, and an oversimplification on my part.

“Voiced” is the other term I see used for I assume the same thing. As in “voiced to produce the designer’s signature sound” or some such inane bullshit. If this is a tube amp with coupling caps (and between stages), etc. then there are things you can or could do. A direct coupled SS amp, not so much. Sent from my iPhone using Tapatalk

RIP Stephen Hawking!

Ugggh! Sorry Nate and other NEers!