[BUILD] 1176 Rev A - Back to the beginning...

Yes the meter moves to a little below +2VU when in +8 metering and maxes out when metering in +4 with the current adjustments and settings that have been done so far.

Daniel

Djankies said:

Yes the meter moves to a little below +2VU when in +8 metering and maxes out when metering in +4 with the current adjustments and settings that have been done so far.

Daniel

Click to expand...

If you turn up your input a little does the meter dip in that mode (like it's compressing)?

No, in both metering modes (+4,+8) the meter moves with the input knob. If I lower input, the meter shows a reduction in level.

Thanks
Daniel

Djankies said:

No, in both metering modes (+4,+8) the meter moves with the input knob. If I lower input, the meter shows a reduction in level.

Thanks
Daniel

Click to expand...

What about compression?  Try this.

Meter in +4, GR OFF, input at 3 o'clock , output at noon.  Adjust the output so your meter is not completely pegged right. Have it sit near zero.  Now click GR on with the attack pot, do you get some drop?

Mike

I seemed to have actually gotten my problem solved. I used breakaway pin and headers for the zero adjust and the headers weren't making complete contact with the pins. I changed them out and calibrated. Everything seems to be in order. All the calibration went as expected. Just hope it stays working. Going to run it for a while and see how it holds up. On my last fuse, so hopefully this one will hold up for me until the rest come.

Thanks again for everything,  ;D
Daniel

Cool. Keeping it on would help. If she's gonna blow a fuse it'll be on a power up.

Hey Mike,

One more question. I tested for the typical voltages posted on Mnats' site with the same test conditions he lists and everything measured correctly except for the base of Q8 (measured around +19 VDC where Mnats suggests a voltage of 16.93 VDC) and the collector of Q13 (measured -1.5 V against Mnats' +9.76V). Is this anything of concern?

Thanks,
Daniel

Djankies said:

Hey Mike,

One more question. I tested for the typical voltages posted on Mnats' site with the same test conditions he lists and everything measured correctly except for the base of Q8 (measured around +19 VDC where Mnats suggests a voltage of 16.93 VDC) and the collector of Q13 (measured -1.5 V against Mnats' +9.76V). Is this anything of concern?

Thanks,
Daniel

Click to expand...

Q13 yes. But I'd double check that datasheet and re-measure. I doubt you'd get the meter calibrated if that were true.

Mike

Q13 Seems to be at the correct +9.76VDC now. Not sure what the deal was the first few times I measured.  ???

Thanks!
Daniel

Djankies said:

Q13 Seems to be at the correct +9.76VDC now. Not sure what the deal was the first few times I measured.  ???

Thanks!
Daniel

Click to expand...

Give it a spin! I bet you it's working great.

Mike

Hi Mike,

Just received the fuses in the mail today! Thanks so much for those.
Today I put a new fuse in and started playing around with it for the first time. I'm quite new to rack gear and i'm not really sure what standard values I should be looking for. I was measuring THD of the unit with a 500 Hz sine wave at .775 Vrms. I wasn't able to crank the input knob past around 30 before there was extreme distortion. Is this normal? what's a normal signal level that would be going through the unit?  Also,  when turned, the input knob produces static, but only when there is signal running through the unit.  Is there a way to solve that?

Another issue that i'm confused about is wether or not the frequency response is as it should be. For mono files playing through the unit, almost all the bass disappears.  is this normal?

Thanks,
Daniel

Djankies said:

Hi Mike,

Just received the fuses in the mail today! Thanks so much for those.
Today I put a new fuse in and started playing around with it for the first time. I'm quite new to rack gear and i'm not really sure what standard values I should be looking for. I was measuring THD of the unit with a 500 Hz sine wave at .775 Vrms. I wasn't able to crank the input knob past around 30 before there was extreme distortion. Is this normal? what's a normal signal level that would be going through the unit?  Also,  when turned, the input knob produces static, but only when there is signal running through the unit.  Is there a way to solve that?

Another issue that i'm confused about is wether or not the frequency response is as it should be. For mono files playing through the unit, almost all the bass disappears.  is this normal?

Thanks,
Daniel

Click to expand...

None of that is normal unfortunately.

Any idea where any of those problems may lie?

Daniel

Djankies said:

Hi Mike,

Just received the fuses in the mail today! Thanks so much for those.
Today I put a new fuse in and started playing around with it for the first time. I'm quite new to rack gear and i'm not really sure what standard values I should be looking for. I was measuring THD of the unit with a 500 Hz sine wave at .775 Vrms. I wasn't able to crank the input knob past around 30 before there was extreme distortion. Is this normal? what's a normal signal level that would be going through the unit?  Also,  when turned, the input knob produces static, but only when there is signal running through the unit.  Is there a way to solve that?

Another issue that i'm confused about is wether or not the frequency response is as it should be. For mono files playing through the unit, almost all the bass disappears.  is this normal?

Thanks,
Daniel

Click to expand...

This might be a good opportunity to build and use a DIY signal tracer. The easiest method is probably, assuming you don't already have a probe, is to build one with an old guitar cable cut in half and a large value capacitor, 1uF or more. Many plan here and online. The cut end with cap is used to probe around while the end with the 1/4" plug goes into your mixer, etc.

If you can trace the signal from input jack on through the circuit, using the schematic of course, it should be easy to determine where the distortion and high-passing begins. This helps narrow down exactly where the problem is occuring.

Another method is to use an old set of computer speakers or something to build a dedicated signal tracing box, but depending on how you go about it, this can be a more involved (but rewarding) build. No matter how you do it, a signal tracer of some kind will always be a useful thing to have around the lab.

I'm also curious how you're measuring THD?

Make sure you have your orange and yellow output transformer wires tied together.

Mike

Hi Mike!

It's funny that you suggest using a probe, I was looking around the internet last night and came across this video (https://www.youtube.com/watch?v=IEcyDzYAsuU). I am planning on going to radio shack to get all those parts today. I definitely think that will be my next step.

Something leads me to believe the problem lies somewhere within the input stage of the circuit because It seems the output knob has nothing to do with the fuzzy/crackling distortion, surprisingly nor does the input knob , its really the level going in that is the problem. So maybe this is an before- the-board issue? let me know what you think.

I'm measuring THD with a program we used in an acoustics class last semester called SignalScope Pro. (don't worry the equipment im using to get audio in has  around .002% THD)

Orange and yellow are tied off  and soldered 

Thanks,
Daniel

And btw Mike,  wonderful job on that new site, looks amazing.  That's going to be sick when it's fully developed.

Djankies said:

Hi Mike!

It's funny that you suggest using a probe, I was looking around the internet last night and came across this video (https://www.youtube.com/watch?v=IEcyDzYAsuU). I am planning on going to radio shack to get all those parts today. I definitely think that will be my next step.

Something leads me to believe the problem lies somewhere within the input stage of the circuit because It seems the output knob has nothing to do with the fuzzy/crackling distortion, surprisingly nor does the input knob , its really the level going in that is the problem. So maybe this is an before- the-board issue? let me know what you think.

I'm measuring THD with a program we used in an acoustics class last semester called SignalScope Pro. (don't worry the equipment im using to get audio in has  around .002% THD)

Orange and yellow are tied off  and soldered 

Thanks,
Daniel

Click to expand...

Yes, that's exactly what I'm thinking of. That probe will work fine. If you can find a 0.1uF instead of 0.01uF, that will do, and you only need a 400v cap if you plan to use it in tube circuits, but really, understand that even solid state equipment still has deadly voltages in the power supply section, i.e. the primary side of the power transformer, fuse box, and meter selection switch, all have mains voltage on them, so STAY CLEAR of any of that at all times when working inside the 1176 with it plugged in.

Using that probe and some way to amplify what it's picking up it should be easy to trace the signal to where ever it's going wrong.

Later on, if you decide you like working with electronics, you'll end up getting a cheap analog oscilloscope, and you'll instead be able to "see" the signal you're tracing instead of having to rely on an amplifier to listen to it, which sometimes can get loud!

Good luck, and let us know how it goes!

  Alright so I've built that probe and its working wonderfully, Hoping to be able to use that in the future on other electronics. A very useful tool. Was actually able to route the signal from the probe into my computer to get a reading from SignalsSope's oscilloscope, but the distortion/crackling only occurred when variable signal was coming through, so the scope wasn't much help here.

  The "distortion" problem was traced to a bad cable. It totally didn't occur to me that cables aren't only an issue in the studio, but also when building 1176 Rev A's. However, I think (I'm sure?) it also may have been that I was using the wrong type of cable. I wanted to use my interface as a dedicated input so I thought that I could buy a cable that would convert the headphone jack' signal into a usable signal for the 1176. Whoops. pulled apart the cable to take a look at the inner workings and basically what it's doing is taking the signal from T and S (left and right from 1/8) and tying them off at pin 2 of the XLR and splitting the ground between pins 1 and 3 (+ and ground)

WHAT?!

  This obviously didn't do what I thought it was doing. Should have investigated further at purchase.
I'm going to continue tomorrow with running tests (with the correct connections of course)  to ensure everything is as it should be. Fingers crossed.

  Regarding the noisy T-attenuator --seems that this is a common problem when  lack of lubrication, dirt or oxidation is present, and that giving the pot a little squirt of lubrication/cleaner usually solves the problem.  (https://www.youtube.com/watch?v=9ZxNtxOoeWA) Is there a way to get some control lubricant inside the T-attenuator? Haven't seen anything on this yet.

Thanks,
Daniel

This has probably been covered but I have a couple of 2:1 transformers and want to be able to switch
between txf and line balancer depending on what source material I'm going to use.
I have tried to compare the switching between the two but I'm getting a very low output from the txf side.
I just wanted conformation that I am wiring up the switching between these the right way?
Is it anything like I've drawn out? If not could someone advise me on a correct way please.

Regards

Spence.