Oh Sh#7! Eddie Current Studio B

Can anyone give me some guidance on input impedance and the SB? Thinking of buying a passive Khozmo pre. I’m thinking the 50k or 100k Khozmo should be okay, at least based on @Josh Schor’s experience with switching out the Blue Alps pot in the SB with a 50k Khozmo pot. Does that seem correct? Source would be Yggdrasil LIM.

 

from what I have been told it changes where the area you get sound is, with my 50kohm sound starts at 12oclock for my 94.5 effecient speakers, for my Utopias the sound starts at 9oclock. will not be any difference in sound quality I have been told

 

So I bought Josh Schor's modded Studio B. I'm very excited about it! the stock Studio B is so dry in tone to my ears that I honestly would rather listen to a Cayin RU-6 which at least has life to it.

But Josh's mods along with finding Electro Harmonix 300B tubes to be much wetter than the PX300b or Linlai Cossor have made it very close to perfect in tone. I'm going to have a local friend @uniqusrname swap caps to try to get just a bit more wetness out of it. Technically it is great though and very close to having perfect tone. It is a much better amp than stock, both in technical abilities and in tone. I definitely recommend these mods to anyone considering them.

 

Something happened to the Studio B tonight though and I can't figure it out. I wanted to try my other 83 mercury rectifier tubes again with my current power and driver tubes. So I turned the amp off, and swapped 83 tubes and turned it back on, and there was no sound coming through the headphone jack.

The amp is getting power, all the tubes are warm and lit up, and the LED is on so it's not a fuse. I have checked to make sure no input switches got changed about 10 times, but I didn't touch them between tube swaps anyways. One clue is that the headphone jack seems to be disconnected from the sound of the amp because when I turn the amp on or off, there is no tube warming up/ turning off noise. It is dead silent turning it on and off with sensitive iems plugged in. I should be able to hear some noise from the amp turning on or off. It's like the amp got confused and is not putting sound out of the right output.

Also if I turn the sound way way up, I can hear the music faintly.

The 83 rectifier tube isn't glowing as brightly blue as it usually does, but I don't know what that would mean because it is warm and it is glowing, and so are all the other tubes.

None of my three 83 rectifier tubes create sound out of the headphone jack now all of a sudden. So something must have happened when I changed 83 tubes but I have no idea what. But sound is not reaching the headphone jack, or it is at least muted to a high degree, since there is no weird noises from the amp when it turns on or off with my iems plugged into the jack (I did it accidentally at first, then left them in to monitor this).

Anyone have any ideas? I'm up late tonight and can't listen to my new amp

Thanks!
Whitney

 

when you put the new mercury tube in did you turn on the left preheat switch first and let the tube warm up? did you go back to the other 83 tube?

 

Ye

yes I always use the heater switch I even hsxf s 1min timer on my phone to wait to actually turn it on.

 

did it get switched to speakers by mistake? or is the input switch changed? This happened to me when I had it on speaker

 

definitely not. I checked that scout 15 times as well as the positions on. Y switcher but I didn’t move them when I swapped 83 tubes anyway.

 

Maybe Josh can get you connected with the tech he had do the rectifier modifications. I'm sure it can be fixed. The hard part is narrowing down the issue.

 

I was hoping it was something simple not something I'd have to have repaired I just paid for it yesterday

 

Yeah that certainly sucks but it sounds like something is wack (based on your extensive trouble shooting)...either from potential shipping damage or a bad tube?

Honestly could be something as simple as a loose solder joint or a bad resistor. Who knows without getting a tech to start checking through the circuit and that values are in spec.

 

I do think something came loose in shipping, can your frient look at it?

 

FWIW, I had a couple of things happen when I had a BA that left me less than impressed with EC's quality control.
Finding the causes took quite a while in both cases.

After one channel went wonky, I discovered that a resistor lead had been twisted together with another so tight that, over time, the lead had pulled apart. That was unusual to say the least. The twisted ends were connected to an output tube, and to different sources on the other ends.

When the rectifier voltage meter on the PS pegged upon start-up one day, I found that a solder joint around a transistor lead had completely separated from the hole in the circuit board. A quite small wire lead in a rather large board hole, and the solder had cracked and separated all the way around. I found several more that looked suspect and resoldered them.

Both of these events happened spontaneously , so I 'spose the moral to this story is to check everything in both units carefully. Since both of channels are out, and especially since you said that the rectifier heater isn't as bright as it was, my guess is that the trouble lies in the PS somewhere. Another thing to check is the umbilical connectors. A pin could have gotten pushed in and isn't making contact now.

 

Yeah definitely check the umbilical - if you look upthread a user had a wire in the umbilical come unsoldered I think at the amp end and had to re-solder. There’s a bunch of wires in there performing different duties - one would be AC and one DC for sure, for instance, given the AC heating. To me no sound sounds like a DC thing, especially given it happened around changes in rectifier tube. Before I got a socket saver for my (older, recessed tube socket) SB, a fat base Mullard not making a connection would still allow for the tube filaments in the 300B's/driver tube to heat/light up, but there would be no sound in the headphones.

Also not unusual for EC amps to have screws jostle loose in shipping. In mine, even with extremely good foam injection machine packing from The Music Room, one of the two inductors for the choke in the power supply came loose and it was hanging by one screw. Same thing (and more) happened with @Souldriver’s amp, which was direct from Craig. EC amps are huge and heavy with a lot of connections and screws and yeah, they have a reputation that way, unfortunately…

Sorry you’re going through this.

 

How can I buy a new umbilical cord? it seems like a good thing to try first. It was actually pulled pretty tight so it was making a sharp turn after the amp and into the PSU because it is like the exact minimum distance I can keep the two apart on my shelf. Maybe I can get one a foot longer.

Thanks for the ideas.

 

You’d have to either get someone to build you a new one (fairly simple “GX” style connectors, just need wire and solder and can probably source the connector online relatively easy etc. - still I’m too unskilled to do one myself, likely) or see if someone (Marv?) could get Craig or his tech to send one. I doubt you’d have much luck emailing Craig but I guess it’s a possibility - could also see if @Josh Schor could since Craig has historically been responsive mostly to only those who bought the amp from him. Third option would be someone with a spare, I guess.

If you have a local connection who is able to repair amps etc. ensuring the cable is good should be pretty easy for them as well as repairing if it is not. Just need a multimeter and a power source, I think ( then a soldering iron or new wire to repair, depending).

 

Not sure if Stefan AudioArts is stil making these and if the Studio B is the same as one of the existing versions but:
https://www.stefanaudioart.com/product-category/umbilical-power-cables/

 

Man I remember when those Stefan cables were the most expensive headphone cables out there and now they seem relatively normal compared to some other options… (Cardas’ new one, for instance).

Anyway yeah if they know the pin out or even maybe just connector type I bet you could get a few of the more boutique outfits to make you one as a custom. Ghent Audio in Shanghai has some nice wire and is relatively affordable if you can get him to custom - if you do DHL it’s pretty quick turnaround, like a week.

 

@rhythmdevils I can check the amp if you can send it.