calling all eqp-1a gurus

Hey everyone,

I just finished putting together a point-to-point EQP-1A based on what I believe is the original schematic and the layout posted in the metas. It works great except for one thing. Whenever I switch to any of the three lower positions with the low frequency selector the audio loses its high frequency content. In the 100hz position it sounds wonderful and all controls operate normally. In the 20, 30, and 60 hz positions it's tubby no matter where the controls are. This also affects the audio in bypass mode as well. (bypass is normal as in the 100hz mode) I've gone over and over all the connections and I'm starting to get frustrated. After hours and hours I can't find anything that appears to be wrong. At the moment all I have is a multimeter. I'm about to order leads for the old scope that I found. Do any of you have any guidance for the meantime while I try to get the funds together to un-cripple myself tool-wise? Any insight or thoughts would be greatly appreciated...

Thanks!

For reference, can you post a link to the schematic you're using?

Peace,
Al.

http://home.earthlink.net/~cayocosta/diy_files/eqp_1a/eqp-1a_schem.jpg

and
http://home.earthlink.net/~cayocosta/diy_files/eqp_1a/eqp1a_filter_schematic.jpg

Hope it's okay to post these...

[quote author="sleepingtiger"]http://home.earthlink.net/~cayocosta/diy_files/eqp_1a/eqp-1a_schem.jpg

and
http://home.earthlink.net/~cayocosta/diy_files/eqp_1a/eqp-1a_schem.jpg

Hope it's okay to post these...[/quote]
Oops, seems to be the same schematic twice & the passive section itself is missing.

I've edited it...

bippity-bappity bump...

It's funny, every time that I think that I'm really starting to understand some things I run into something like this that simply confounds. It's probably the best thing that could happen learning-wise... It'll get sorted out eventually one way or another and maybe a couple of dots will get connected for me along the way... Thanks for looking! This forum is the best!...

THAT'S NOT A MOREFORD SCHEMATIC, IS IT?


:twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :twisted: :evil: :evil: :evil: :evil: :evil: :evil: :evil:
:evil: :twisted: n :twisted: o :twisted:

No wonder you can't figure it out.

I have a different one.

CJ!!!

You're the best! and an endless source of inspirational avatars...

If you feel like sharing it might be a big help. I'm doing the whole thing from Cayocosta's layout as much as anything, and it totally seems to represent what I see in the schematic. But... there's obviously a problem either in the bypass switch or in the capacitors that are brought into the low filter circuit through the first three positions of the low frequency selector. I'm making this thing using a lot of parts (switches, etc - not passives) from the Krohn Hite band pass filter that I posted photos of a few months ago (somebody's gonna shellac me for that, but I couldn't help myself... besides... it would have just sat in disrepair...) and one of the old parts is the bypass switch itself. It looks like a normal DPDT switch but I think I'm going to replace it to see if that's the cause of this problem. I used a new Grayhill switch for the low frequency selector and I'm almost certain that it's wired in correctly....

This thing's driving me a little daffy but other than this little problem it sounds absolutely gorgeous!!

All the best,