Guitar Gear Forum

I’ve posted this on a few forums to maximize perspectives:

Howdy gang.

I recently completed my first amp build (a TW Express circuit). Everything fires up, and I'm getting signal through my speakers, though it's very VERY quiet (as in, with the volume on 10, I'm only as loud as someone talking loudly). It's also very muffled. I currently have a full compliment of EL34's and 12AX7's known to be good loaded in there.

I've gone through the amp to make sure no connections are shoddy or missing, and I can't find anything.

and before anyone offers insight about lead dress or component placement, I know. Ken Fisher did it better. My goal is to have an amp that fires up and makes the right amount of volumes. I’ll worry about stability and noise once the volume issue is sorted.

I've attached my voltage chart to the post As well as some photos.

https://imgur.com/a/IWKdUX8

Note: the heater voltages were measured wrong for the chart. I’m actually getting 6.7VAC

I’ve done a pop test (checking voltage at the plates to see when the sound from touching the probe drops) and V1 is noticeably quieter than all others.

I’ve checked the impedance on both sides of my OT primary, and it’s good.

I've also confirmed my input jack is wired correctly.

I’ve also redone my bright switch and fixed all potentially problematic heat shrink connections.

Thoughts?

Best thing to do is trace the signal from the input jack to the end.
Use the schematic to see where the signal enters/exits different components.
Method 1) oscilloscope: input the signal at the input jack, and trace from there.
2) signal injector [youtube]https://www.youtube.com/watch?v=V-UnLEu0S9g[/youtube] If you use this method, don't do like I did, and connect your expensive phone via a cable as the signal generator, even though there's nice apps that generate a sine wave. I found this youtube after 1 second. I'm not recommending it specifically, but it gives you an idea.

long standing member wrote:Best thing to do is trace the signal from the input jack to the end.
Use the schematic to see where the signal enters/exits different components.
Method 1) oscilloscope: input the signal at the input jack, and trace from there.
2) signal injector [youtube]https://www.youtube.com/watch?v=V-UnLEu0S9g[/youtube] If you use this method, don't do like I did, and connect your expensive phone via a cable as the signal generator, even though there's nice apps that generate a sine wave. I found this youtube after 1 second. I'm not recommending it specifically, but it gives you an idea.

Yeah I was going to try putting a 1k sine wave into the input and measuring the VAC at different points along the signal path. I’ve localized the issue to either at V1 or somewhere on the way to V2.

If that doesn’t help me, I was going to build a cable with: headphone plug to .01uf 600v cap to alligator clip and put it into different spots along the path. See when the sound comes out of the speakers properly.

Good luck!
It'll probably be something stupid, and you'll kick yourself.

So, what was the problem?

long standing member wrote:So, what was the problem?

Still working through it. I've tried so many things, but no improvement. I'm going to continue to work through the issues over Christmas.

Figured it out. I had connected the B+4 lead to the wrong side of a resistor