Pultec clone troubleshoot

[Alexmc1988]

I built a pair on pultec clones. Both pass clean signal and all functions work well. They sound great but one of them has noticeably less low end, even in bypass. When I run pink noise through them it looks like it has a high pass filter on it around 150hz. Any ideas what might cause this?

Attached is a pic of pink noise going through both units in bypass. The left one is pretty flat and the right one looks like it's high passed.

 

[Alexmc1988]

This is the layout I used.

 

[pucho812]

If you have two units  and one is working as it should and the other is not,  then there is a difference between the two.  Start with the obvious, a visual inspection.  You know the problem now you need to find the cause and solve it.  Check every connection, every part. Since it is a diy build you may have installed a wrong part or wired it incorrectly

 

[CJ]

your bypass cap on the 12au7 is no worky,

that's my fist guess at least,

 

[Alexmc1988]

Thanks for the replies! Sorry I'm just now getting back on here. I just had a chance to look it over. Our 2 month old has been keeping me busy! Any way, I touched up some of the solder joints around the bypass cap on the 12au7 and a couple other spots around there. That seems to have done the trick.

Thanks again!

 

[Alexmc1988]

I have 1 more question! I want to use these on my stereo bus. When I run sine waves  through them at 80hz, 1khz, 10khz and also pink noise 1 of them is about .5db louder than the other. I guess thats pretty close but how would I go about getting them spot on with each other? Is there a certain section/component I should focus on?

Thanks!

 

[pucho812]

Well is that with the units set flat(no boost or cut)?

 

[Alexmc1988]

Yep, set flat. Its the same in bypass also.

 

[AusTex64]

Swap the tubes and see if the gain difference follows the tubes.