Question about Session/LTD 400…

[Brett Cooper]

I have both, a Session 400 and an LTD 400. And both of them need normal maintenance. But, the both have a fizzy, croupy distorted sound when certain strings are played on a Telecaster and Les Paul...like 3rd and 4th strings open. It’s not a real strong distortion and I’m having a difficult time in trying to describe it. It really doesn’t sound altogether bad to me but I want both of them right. I’m wondering if anyone else who owns these amps has experience with this. And, if so, did routine service and upgrades fix it.

[Jack Stoner]

The original Session 400 is discrete components (transistors). I had a 90's 400 LTD and it was integrated circuit (op amp) design. Different speakers, too.

From an amp tech viewpoint two different amps.

[Ken Fox]

The small cabinet LTD 400 is the same amp as the Session 400
The bard layout of the preamp is different as it had to be smaller. Schematic is the same

Not sure what would cause the distortion. There are a lot of electrolytic caps in the preamp stages

Recently had two with similar problems. Was bad caps

[Ken Fox]

As there were never board layouts for these amps from Peavey I had to figure out where the components were located so I could do my upgrades for these amps

I used my own numbering system for parts I would replace

Here are samples of an LTD 400 and a Session 400 pre-amp that I did. The last two amps I worked on had a bad C2 or C3 I replaced both. I locate bad caps using an ESR-70 tester. You can get one from Amazon. Equivalent series resistance tester, one of the best tools on my shop.

[Ken Fox]

[Ken Fox]

https://www.amazon.com/Peak-Electronic- ... 5400&psc=1

[Jerry Overstreet]

Unlikely the same condition with both amps, but you might visually check the speaker vent screen for deteriorated foam.
A common condition for older Black Widow speakers. If yours are the original speakers, might take a minute and just take a look.
viewtopic.php?t=213959&highlight=mainta ... aintenance

[Brett Cooper]

I appreciate your response, guys…

I’ve acquired both of these amps in the last month or so. I was very glad to get them.

Jerry, I swapped the speakers in both of them. I put an EPS-15C in the Session 400 and a TT-15 in the LTD. I’m quite sure that normal maintenance/upgrades is going to fix a lot. I thought I remembered reading somewhere on this forum that others had ran into this issue with these amps. When I get them into the hands of a proper technician, I wanted to be sure I gave him all the information necessary to get them right.

[Jerry Overstreet]

I see. Good luck getting your issues resolved.