The Single Power ES-1/2 repair and restoration thread - Page 7

Second and third posts finally updated

It's my pleasure Kane.

A little progress report. The amp chassis sanded down to the bare metal and with all mounting holes for the new terminal strips drilled and countersunk. I've also sorted out the back panel so it's now dual mono with RCA/XLR inputs on each side (with a switch to choose) and loopouts for both types. There is now only a single umbilical in the middle. I've also changed the front panel a bit to accept Marc's teflon Stax socket. There are now extra holes on the top panel to accept the 4 panel mounted trim pots per channel and the 5 test points. I also added spots to secure 3 perfboards, one which will hold a voltage divider network for the HE90 output and two which will hold input transformers should they be needed to perform phase splitting for the SE input.




The PSU cover has also been stripped and drilled with ventilation holes. Now they are both off to be refinished so I can start rebuilding the amp.

These are for Kane:








This was just the first test fitting and the amp is nowhere near ready but I'm getting there. The PSU is as is outlined in the first few posts (Blue Hawaii PSU with 4*500uf/500V caps plus two separate PSU's, one regulated to give the C- supply needed to properly bias the tubes and the other is for the status led's) and the amp section is rebuilt from the ground up using the schematic posted on the first page and much better parts then Mikhail ever used. When I'm done then I'll post an internal pic.

Thanks but ehhh.... no thanks since. I'd have to buy everything new for it and it might just be cheaper to get a chassis made and some new transformers from SumR... I'll add a list below I made for a friend detailing what was reused from the stock amp in this build:

Pretty crazy huh...

To have full control over the operational parameters of the amp then you really need all those pots and test points on each side but the layout is mostly based on necessity. The test points are all mounted in holes which are too large for them so I used these M6 spacers (with another one on the inside) to make up for it. I also counter sunk all the screws which meant I had to fully layout the amp in my mind before I sent it off to be powder coated. Only one issue came up but that was easily fixed without butchering the finish...

The chassis is indeed terrible and simply putting the two halves together can be a pain with only 4 screws. While the design works for the amp, with everything bolted to the top plate, it is simply idiotic for the PSU as the switches, led's and connectors are all mounted to the top half yet the PSU components are on the bottom.

How about just SRX (the original name of the Stax design) or ES-X...

They will come as soon as I've received the missing 6 resistors (should show up tonight with all the T2diy stuff) and tested the beast. I did check the filaments yesterday and everything lights up just fine.

It's a sad story all around with the ES amps but there is a way to make it right, just involves a lot of work. There is a way to salvage the amps without completely stripping them like I did, mostly it involves building the simple TL783 based C- supply, fixing the filament wiring and installing a proper, adjustable, bias supply. Personally I'd just discard the DC filament supply since with some care taken with the placement of the filament wiring the amp is dead silent.

Your amp Neil was a particularly bad case though. Major work needed to put it right.

I posted these in the Stax thread but they should be here as well:

I decided to open it up to relocate two wires which were too close to the filaments and snapped a picture:



The wiring may look like a bit of a mess but it really isn't. Filaments are kept well away from anything else and power is kept away from the signal lines. The layout could have been better but I was stuck with the crap SP layout so I tried to make the best of it. The signal path is much simpler now and doesn't use the terminal strips as a part of it, i.e. everything is wired component to components and they are all properly supported. The only part lacking is are the green Nichicon caps, I should have supported them a bit better and will likely fix that sometime. The RCA sockets are still not hooked up as the amp may need input transformers since the gain is not high enough. For the time being it does work with hand picked tubes but some Lundahl 1544a's would be perfect for that role. Simply using a balanced source makes this a non issue but all my gear is SE only and will likely stay so for the foreseeable future.

All components are top quality, the majority of the resistors are PRP audio grade with some Caddock MS-132V's as well. All power resistors are Mills and Kiwame plus some 2W Riken's thrown in for good measure. The pots are all Bourns 3540S, 10 turn precision wire wound.

The real problem was finding coupling caps that will work in this amp. Most are rated at 630V but that really isn't enough in this role with +/-430V PSU voltages. The ideal choice then are Mundorf which are rated at 1200VDC but they couldn't be too big so I settled on the Supreme line. At 20$ they aren't cheap but not terribly expensive either. There are also two 100uf caps per channel in this amp, Mikhail used standard Black Gates but I used non-polar Nichicon ES. Ideally film caps should be used here so the Nihicon's will not stay for long.

The terminal strips were some I've had for years plus I reused some from the SP build. The XLR connectors are Neutrik and the RCA's are Cardas GRFA. All signal and power wiring is Belden 83006, teflon coated SPC. The filament wiring is from the stock amp but tightly twisted to minimize interference.

Here is an old pic of the PSU from when I was testing the C- and led supplies:



The only big changes from this picture is a proper terminal strip for the filament wiring and I've added some random ventilation holes.

Now, how does it sound? Not bad at all and far, far better then when I initially powered it up. Compared to my BH (which I built as well) the ES-X does lack a lot of the focus and sheer power of the hybrid beast and the FR isn't as ruler flat. The HF does lack some sparkle and presence, the midrange doesn't have the projection of the BH and is a bit thicker then it should be. The bass goes deep but is a bit too round and boomy for my tastes.