Distorted and Low output on my T15

[xhavepatiencex]

I recently built one, and I am getting +/- Right around 18v at both points, I have checked over everything a few times and cannot find any problems. I am getting a very low output around -30 and its distorted and the more I turn it up just the more distorted it gets without raising the output anyone has any ideas what may be wrong?

[tpryan]

What DC voltages do you measure at:

U1, pin 6
U2, pin 1
U2, pin 7
U4, pin 6
U3, pin 1
U3, pin 8

Let us know what you find.

[xhavepatiencex]

ok, I am out of town for the weekend I will post what I find monday or tuesday!

[xhavepatiencex]

This is what I got.

U1 Pin6 - 0.00v
U2 Pin1/7 - 0.00v
U3 Pin1 - -0.19v Pin8 - -0.49v
U4 Pin6 0.00v

[tpryan]

If you have a signal generator, set it to produce a 1KHz sine wave at a level of about -35 dBu (23mV). The precise level isn't critical. Apply power to the T15, set the gain control at step 6, and turn the trim control fully CW. Measure AC volts at the same test points as well as directly at the output of the generator. Let us know what you find.

[xhavepatiencex]

I do not have a signal generator could I use my DAW sending a signal out into the pre amp?

[tpryan]

could I use my DAW sending a signal out into the pre amp?

Sure.

[xhavepatiencex]

Ok, so I did the test. I set my t15 to have the full fader so I just took readings at the fader all the way down and all the way up.

For the fader down.

u1 pin6 the signal was jumping from -1v to 2v
u2 pin1 0.00v pin7 jumping from 0.00v to 2v
u3 pin1 -0.13v pin8 -0.49v
u4 p6 0.00v

fader up

u1 pin6. Same as before
u2 pin1 0.06v pin7 -1v jumping to 0.50v
u3 pin1 -0.08v pin8 -0.53
u4 pin6 1.5v to 2.5v

the output while full up was jumping around while full up to.. and the output measure in my daw was not much more than the signal I was feeding it. just much more distorted.

[tpryan]

The test signal was a steady sine wave?

You had your meter set to measure AC voltage?

What is the output connected to? Are you driving a balanced input?

What happens to the voltages at U3 if you disconnect the output cable?

[xhavepatiencex]

yeah, it was a steady output, and my dmm was set to the right setting. It was driving a balanced output. I will see what removing the output cable does to u3.

[xhavepatiencex]

nothing really happens when i remove the output cable. voltages are about the same. they seem to jump around slightly too. Any other ideas?

[tpryan]

Try replacing the line driver U3.

[xhavepatiencex]

ok, where I live has zero electronic suppliers are 5532's by chance something that can be used for this because I have a few laying around if not. Could I get a new line driver from you?

[tpryan]

You can probably get a few free samples from Mouser - if not send an e-mail to sales. A 5532 will definitely not work.

[xhavepatiencex]

I got the part the t15 works great now. Thanks a bunch!