[BUILD] Hairball Audio - Elements

[Echo North]

I would suspect soldering issues. Particularly the large caps, examine the lead that connects to ground and confirm there is good contact. Probably the biggest thing I see in those repairs. 90% of my repairs are solder issues.

You can also swap op-amps to make sure you don't have a bad op-amp....which is rare.

 

[Parabola]

Okay I will try all this.

 

[camshash]

Hello. I built 3 Gold kits last night and this morning. I took my time and put them like an assembly like to make sure I put every part in the correct place.

One of them works perfect with no issues.

The second one is intermittent. I might work and then it completely loses signal. Then it can start working again.

The third one doesn't pass signal at all. To make sure I don't have any loose joints, I reheated the solder to make sure it was flowing properly. Still nothing.

All the phantom LEDs are working.

Any thoughts?

Did you go through all the test points listed on Hairballs website?

 

[Parabola]

I seemed to have figured it out, thanks all!

 

[chromaserve]

Hi... finished two Bronzes and have two observations of which I don't know if they could arise from build errors. While the basic sound is great,

1. the noise level is noticeable higher than with other API style pres (including one based on the Eisenaudio board that is now the Silver) when I put the same op amps in and use dynamic microphones or not-so-loud condensers (AT Pro37) on soft sources.
   
   
2. on the 1-3 highest gain settings depending on the opamp, all my 2520 style Opamps (GAR1731, GAR2520, CAPI0252,Fivefish DOA12, Red Dot) go into inaudible oscillation (VU needle on my Bento 8 Pro rack is slammed, the sound is lower in volume than on lower gain and it starts getting slightly distorted),
   while with e.g. the original Raindog, the GAR918 and the AM10 it goes all the way to the top without oscillation / volume loss. Still, some more noise than on other equivalent amp.

I remember reading this issue with lower gain on highest setting before: [BUILD] Hairball Audio - Elements
"The only issue I'm having is the 11th and final gain position tends to drop the signal significantly.", maybe the oscillation was not noticed then.

 

[wstratton]

Hi there, I've built a couple of Coppers, which have been great, but am having some issues troubleshooting my third Copper build. The output is lower (the gain has to be cranked to get a similar signal to the other two, almost as if the pad were permanently engaged), and the d.i. input does not pass a signal, but it does disengage the XLR input. I've tried swapping the op-amp, and I will go through the list of other troubleshooting strategies on the Hairball website, but I'm just writing in case anyone has any thoughts on what direction to focus on.

 

[wstratton]

Never mind, fixed, at least for now!

 

[ElliotGKnapp]

I built a Copper and used it at home on an extender for about a month, then sent it off to a new owner. On arrival he's reporting a ringing feedback associated with the Output knob: "if the output knob is at anything less than fully clockwise (max), there’s a loud ringing like you’d hear with a PA or guitar amp feedback. This happens whether phantom power is engaged, or pad or polarity. The high pitched sound doesn’t go up or down in level either, as knobs are turned, it’s consistent."

This wasn't happening at home during testing, so I'm curious if you have any ideas what might be the cause--I've built several Elements and this is the first issue I've had! Hoping to get a jump start on troubleshooting when the module returns.

 

[ElliotGKnapp]

Please disregard the above--we ruled this one out as a usage issue. For anyone else who might experience this, the user was running the Copper into the front of a Focusrite Scarlett interface and had the interface preamp gain cranked up in addition to the Copper gain--when reduced to a level more appropriate for the accommodation of an outboard preamp, the issue went away.

 

[Lebansky]

Hello, having a problem with a Copper build. Everything works good, but I'm getting no phantom power. Double checked orientation of polarized caps, placement of transistors. Re soldered all points on +48 switch and components in the +48 box. I have continuity from the switch to the edge card as well. Also checked the rack to make sure it had correct power. Any help would be greatly appreciated. Thanks!

Edit: problem solved, it was the rack not the module!

 

[emrr]

Re: Hairball Gold

I was digging around the various Jensen and John Hardy data sheets on the JE/JT-16, and noticed varying Zobel values depending on the era.

It's 4K32/680pfd on the 1984 JE-16-A/B sheet and also says "Previous data sheets recommended
an RC network of 3K6/820pF. The following specifications refer to the currently recommended network, which yields improved performance.“

That 1984 data sheet has greater detail on measured transformer impedance versus frequency, not seen on more recent sheets. Impedance is lower at the higher audible frequencies.

The later/current JT-16 data sheet is 4K52/620pfd.

The John Hardy booklet shows the original 3K6/680pfd in the example circuits, but the updated 4K52/620pfd as on the later JT-16 data sheet in the M1/M2 drawing.

It's 3K6/680pfd in the Gold.

We're talking about mostly indistinguishable differences in the treble shape, square wave response, and Z loading, but maybe more critical when you get to ribbon mic loading.

From Mike at Hairball:

That circuit was "designed" by Jens Jungkurth at Eisen Audio for us, so I wasn't involved in the tuning choices. Jens is pretty detail oriented and tends to have his own processes and preferences when it comes to zobels, loading etc.

 

[Chrome Heart]

I just finished a Copper and it won’t send 48v to the card edge. It gets as far as R402 and R403 but doesn’t cross the resistor. It does on my gold build which works great. Strange thing is the 48v circuit parts are the same.
can’t figure why it won’t go to pins 8 and 10. I’ve pulled the parts and remounted them, resoldered the switch… nothing.

 

[Chrome Heart]

UPDATE:
Phantom power works on the XLR when the 1/4” direct Jack is inserted. Could it be a faulty Axicom D2n?

 

[Chrome Heart]

UPDATE:
Phantom power works on the XLR when the 1/4” direct Jack is inserted. Could it be a faulty Axicom D2n?

Well, I’m at a loss. I’m getting 48v to the switch but it isn’t getting to the input tranny. Gone through every component and solder point. In DI mode it’s getting to 8 and 10 on the card edge, but not in mic mode.

I know this isn’t a very active thread.

 

[dmp]

So it sounds like you have +48v going into the 6k8 feed resistors (measured where the 470R meets them) but not on the other side (in mic mode). Also I'll assume the rack slot is known to be good. When you switch from DI to mic mode, somehow the phantom voltage is being pulled to ground. Either the mic/DI relay has a bad solder bridge, the pad relay or phase relay, or the transformer primary have a problem. Because the 6k8 resistors are fairly big, the phantom voltage can be pulled down fairly easily if there is a solder bridge to a ground.
This kind of a gremlin can be tricky to figure out. But there is definitely a problem somewhere and you just have to find it.
The quickest way to troubleshoot IMO is to start pulling parts one at a time until the phantom voltage works, then carefully start testing and replacing parts. Multi pin parts are tough to remove without damage with just a soldering gun. Best way is to get a hot air workstation so you can melt the solder to all the pins at once to remove the part. Then clean up the PCB with a desoldering gun and 99% alcohol before resolding.

 

[jabe]

I'm building a Silver and wondering about the impact of R606, the resistor in series with the OT primary. According to the component guide it is "used to limit output short circuit current, and to drive the output transformer less efficiently for audible effect" and suggests a value from 10R – 150R. The Copper and Gold use a 43R there so I presume I could follow suit and call it day, but am curious if anyone has played around with that "audible effect".