5e3 style preamp coupling cap values

[vmazz]

Id like to change the values on one of the coupling caps coming off of one channel of a preamp stage 1 in a 5e3 type preamp stage. Will this effect just the one side? Stock 5e3 is .1 mine has .047 , id like to change one side to a lower value to cut more bass. WHat I dont know is if each channel is independent or not. ANy thoughts are greatly appreciated.
PS this is a dukane PA which is almost exactly like a 5e3 especially in the first stage.
Thanks

[vmazz]

Well I did it and it seems to have killed any gain through the channel with the larger cap ..is that possible....they have to be the same value on both sides?

[pdf64]

Probably you've caused an unintentional problem. Retrace what you did, put the 0.1 cap back, and see if what the mistake was becomes clear.

[d95err]

If you have the standard 5e3 preamp with the "backwards" volume controls, then the controls are highly interactive, and I'm sure anything you do to one channel will affect the other in some way. Changing the coupling caps to smaller values is a fairly standard mod though, and should not have as dramatic effect as you describe. It seems something else went wrong when you did the mod.

If you want the channels to be more independent you could try changing to more conventional volume control wiring and mix the channels with mixing resistors. Plenty of threads about that in the 5e3 forum.

[vmazz]

THanks for the input folks. Ive seen Bruce at Mission Amps mention that he uses a .033 on the bright channel and .047 on the normal, which is what I was trying to do..so I know I must have done something else..probably just a cold solder joint . I will post when I get it resolved . Thanks again.

[Bruce / Mission Amps]

If you are already using .047uF caps then you should put a .022uF in the bright channel spot and reduce the 22uF-25uF bypass cap around the 820 ohm biasing resistor of the 12AY7 to something lower like 4.7uF.

[vmazz]

Ok Bruce...what if im using around a 1k biasing resistor?...will lowering that bypass cap lessen the gain a bit and/or work with the coupling cap as a filter? Thanks for your help.

[vmazz]

Well I succesfully completed some mods...I must have had a cold solder joint initially giving me problems...I have a bright channel with .022 a normal with .047 a bright cap on the volume of the bright channel 150 pf..I changed the first stage bypass cap from 25uf to 1uf ( Bruce suggested a 4.7 but I didnt have one with a high enough voltage rating). I also disconnected a negative feedback loop that was present in this amp Dukane PA 1a385, Im thinking of puttin in a switch or a presence control. I starteed my mods with a new OT too which seems to be working great. Ive learned alot with this project so far. Thanks to all who gave me advice . I am definitely grateful for the wealth of knowledge and gracious talents on this board. Dont stick me on that ungrateful irritating noob thread ...JK...Seriously though , those of us just starting to learn should be appreciative and stop and think about what is being said so we can really understand whats going on in these circuits. I will attatch a schematic for anyone curious..these are great little amps..like a5e3 crossed with a Bassman or something..lots of potential.Dukane 1A385 vers2.pdf