spritzer

Those phase splitters are also in the WA22 and I believe they are just transformers. I can't see any power wires going to them there either.

Since I was asked, here is the cheap China amp with the Apex opamps

This week I was browsing the net and I came across this: http://bbs.erji.net/forum.php?mod=viewthread&tid=2239622 Now it is all in Chinese but these were the first pictures of the insides of the Woo Audio 3ES. This was an amp I never really paid any attention to, I'm so fedup with Woo and their sub-par crap, but finding internal pics does warrant a look. First off the pics aren't great but at least there are some schematics there and we need to try to verify they are correct. We have no further info than this as I can't find any more internal pics, so this is what know at this point. First the PSU: Now, nothing new here, same old crap Woo have been building for years but why place the output sockets right next to the power transformers like that? I mean the whole idea behind a two box solution is to place the noisy power transformer away from the amplifier and thus the output, not run the signal back into the PSU and have the output sockets right next to the, rather large, radiation field of the EI power transformers. Makes no sense but things are about to take a turn to the worse: Now... here is where things start to look a bit off and I'm going to see if anybody can spot it without venturing further. Now neither Kevin nor I can read Chinese so the markings on these two schematics that were included meant nothing to us: We focused on the tube schematic and wondered how this could work, I mean it is a simple grounded cathode 6SN7 input with a 300B cathode follower output. We are not dealing with a lot of gain here so at first the schematic had to be wrong, no way to drive electrostatics from this. Then Kevin figured it out, this is just a preamp, the latter schematic is the output for the headphones and what is that... it's a fucking Apex PA97 opamp!!! https://eu.mouser.com/datasheet/2/156/pa97u-1853045.pdf Go on, double check the pinout against the datasheet and look at the recommended values. Now look at the internal picture again and follow the wires, input selector is on the left and the preamp/headphone selector is on the right with the red wires. What's there next to the back panel with 4 identical modules and a shit ton of hotglue? The electrostatic module... which is made up for 4 of these which cost around 100$ each in bulk. This is a 14k$ amp! Now we don't know what is on the heatsinks next to the tubes, has to be a TO220 size part but no way to see what it is. The rest of the schematics make sense though. B+ goes directly onto the 300B plates and there is a grid resistor next to the "G" pin with the cap from the 6SN7's right next to it. Two large resistors next to each filament pin too. Then we have the large, brown, resistors going off the B+ to feed the 6SN7's and two identical plate resistors for it too. . Now what is the problem... well I can't see anywhere on the Woo site which says this is a hybrid amp, they talk about the 6SN7's, 300B's and the rectifier but nothing about a basic opamp outputs for the electrostatic outputs. Let's just quote them: "The new 3ES achieves the most ambitious dream in the audio world". Yeah... not so sure about that... Funny enough, clones of the Stax D10 are surfacing in China now and I have one. Guess what that one uses? Apex opamps.... and I bought one for 250$ shipped to me and it fits in the palm of my hand. Below are the rest of the pics from that Erji post for posterity.

No, I don't dare touch them.

You need a 10K quad pot and they are quite rare. TKD does make those in the 601 series but it is tiny so it would need a PCB to make wiring easier. I'd stay away from the Alps RK27 and the RK50 is only available as 50K.

I've reviewed the pics and nothing stands out to me. Couple of things, the input BJT's are sitting in a socket which is then sitting in another socket, did you try to separate the two? That could be a factor. Now static sound from the volume control is always possible so one thing to try, swapping the input and output wires between the channels.

Please send me some high res pictures as I might be able to spot something wrong. It is also worth it to try and swap the input devices between the channels and see if the problem follows the transistors.

You would need pretty fancy equipment to test them but this could be a THAT340 issue. I'm not sure if you amp has THAT340 as the input (as I've used other parts in the past) but they have been known develop issues.

I watched the entire season on a flight to the US recently and I got PTSD from it... yeah it is very accurate in places.

That's a bit high but not massively so, I doubt that is the issue here. Intermittent issues are so hard to track down but do one thing, try to reseat the input BJT's (they are in the middle of the boards) and see if anything changes.

You can measure at the output connector or just directly behind it on the main PCB inside the chassis. Multimeter set to VDC and just a few millivolts should be present. You measure with regards to ground so the black probe goes onto the chassis or the middle pin on the volume control (either side) marked GND.

Well here is something odd, it's well known how much I "love" the SR-009 and I recently picked up a used one in Japan as a part of a larger bundle. I was just going to move it on as I already had one in my collection so after putting it off for a while, I sat down to test it in my main rig just to make sure it was ok. Now here is the odd part... this one sounds nothing like the other eight SR-009's I've had here over the years. It has a slight forward tilt to it but far better than any 009. It lacks that artificial "boxing in" of voices or the excessive brightness superimposed on everything. I dare to say they are pretty smooth and with proper bass response too. Thinking I was going nuts I grabbed the other set from my collection (which sounds like all the other 009's) and did a double blind test. I had my better half pick songs and hand me either of the two sets (plugged into the same Carbon CC) and this wasn't even close. With the regular 009, just the opening of a song was enough to give them away. That same feeling as with Tyll reviewing the Ultrasone ED10 if anybody remembers that... Now this set is never leaving my collection but why is it like this? It's not a super early one or a late one, I've had both (plus everything in the middle) and they all sound the same. In fact the other set I have here is one of the last ever made and it sounds the same as the very first set I got back in 2011. This set is in the SZ9-1200 range so this has to be a QC issue or something like that. I don't know the history of the set but no mention of it ever being serviced. Earpads feel like new and the whole set feels like new so yeah... not sure what is going on. I first tried tried them on Friday and I've probably logged 10 hours on them by now which is pretty unheard of for me with 009's. Hell, I had to force myself to try the Purrin Rock set which just arrived (those are weird) and now I'm back on the 009's.

No, never had this issue pop up but first thing to check would be the offset voltage. If something would fail, it could knock the servo out of kilter and damage the headphones.

I might do that and also fix that stupid cable entry and how the earpads are mounted. It's on the back burner though as I want to mull it over a bit.

Hehe not sure but I always like to take a basket case and make something useful out of it. I do have some plans for these 009's which might help with them all in the future...

Just don't do any of this, none of it is an improvement and just fucks up the sound for no good reason.

So I bought a lot of modified headphones on ebay, SR-Lambda Signature, SR-007Mk2 and SR-009. They looked to be in rough condition so I thought, worst case I'll tinker with them and have some more spare parts for my stock. Now... the first two units were bad... really bad but I fully rebuilt them from my stock of spare parts. Now I've been fixing up lost cause headphones for 20 years but still, these were the worst I've ever seen. Missing parts everywhere and utterly retarded ways of "improving" them by making everything worse. Now, I had left the 009's in their box until this morning and wow... just wow... So what are we looking at, these are the outside protection grills... taped to the outside of the housing with some rubber/butyl type tape. The earpads are fixed in place with it as well and it covers up the cable entry on both earcups. Now... this is after repairing two utter clusterfucks of incompetence and stupidity but yeah, not prepared for this one. Pull off the earpads and the tape around the cable entry and this is what greeted me. Just look at that soldering, the holes in the dust covers and well... the driver in backwards. These are dipoles like all Stax... it won't change anything to put it in backwards. There was nothing holding the earpads in except more of that glue and notice one missing screw on the driver. It gets worse though... Here is the driver removed and there is no dust cover at all. Yeah...nothing at all. Here is the other channel with just the tape over the cable entry removed. How this is supposed to improve performance is completely beyond me... Here is the housing with the driver removed and just look at all that adhesive residue. That ties into this, the earpads: Now they are utter trash at this point but look at the adhesive residue on them, that is hot glue! The most useless of adhesive which should only be used by kids in arts and bloody crafts! So end results is these headphones are completely fucked. The arc and housings can be used and the cable might be ok but the drivers are probably beyond hope. Add to this all the missing hardware and I'm not sure what I'll do with them. I might try to find a dead set of 009's with driver failure and make one good set out of the two or something creative. Final lesson, if somebody says they are modifying headphones and improving performance... odds are it is something like this.

They did suddenly show up in quantity at Mouser last time so it might happen again. I just found out about it as I had some on order and they suddenly shipped, way ahead of the set date.

Flights and hotel booked.

I'm thinking about it

So if it is anything like this: https://6moons.com/audioreviews/viva/4.html Yeah... this is utterly terrible. To make things worse, those are Rifa caps, known for one thing only... failing internally and presenting a dead short. Plus they are PSU caps, why they are used for coupling is beyond me. This does stink of SinglePower... Some more pics here: https://www.audioshark.org/amplifiers-8/amedeo-viva-visits-suncoast-audio-16591.html Look at this trash, 17k$ and all you get is an Alps RK27 for a volume control that costs less than 10$...

That's very cool. 🙂 The old ones were brass?

My schematic shows 8.2K for that position so not sure what schematic you have. Also check R44 and R45 if the voltages look a bit low.

I think Stax use the new Tung Sol GTB in the 700T so that is new production. Whether you can get them anymore... I'm not sure as they are made in Russia. As for the voltage, the GTB tops out at 450V so it's better than the regular version but still a long way from the 6S4A etc. There is also the 6BL7 but no new production that I know of.

It really doesn't matter, 5% is plenty good so just go with what ever fits.