Hotswitch with two relays

[YardBirdFan]

I have a wacky idea.  I have a H50 amp that I am re-doing.  It was built by another forum member that never got the relay switch system working.  It is the Hoffman H50 Revision D with hotswitch, effects loop and the meat control. 

Here is the idea...  Use two relays so that I can kick in another resistor or potentiometer so that the clean and overdrive modes do not sound so different in volume.  Basically one would do just what the DPDT relay is designed to do in the schematic, the other would kick in a resistor when in OD mode. 

Good idea? 

To go one step further, I am thinking of a 3rd relay to allow putting the effects loop in and out... maybe another pot to adjust the effects return level?

I bet I am overlooking something here.

I think for gaining a couple holes for pots, I could to to a mini switch to change the two inputs into one and have the same Hi/Low input capability.  I also have some switched 1/4 stereo jacks so my effects send can be reduced from two plugs to one plug.

I will post some pics next...

[YardBirdFan]

Here is the schematic this was built around...

[YardBirdFan]

I forgot to mention, I was thinking of going with a stereo footswitch cable to take care of both channel and effects on/off.  LED's for both on board the amp and on the footswitch. 

Here are a couple pics of the amp exterior.

I can post pics of the guts if anyone is interested.  It is a bit of a mess at the moment.

[YardBirdFan]

OK... one gut shot.  This shows the relay socket installed, but accommodations for one more.  I think I can find room for a third as well as one of the new relay power supply circuits.

Many of the wires have been removed since this pic.  My preamp tubes were all getting like 450 volts... so I thought it best to start over since features may change anyway.  The wires used, shielding, heater supply layout and ground were all suspect anyway.

[tubenit]

Here is something to consider.

I would either use two "trim pots" inside the amp or pots on the chassis (either front or back) & use the relay this way. This way you can indeed match up the clean to OD volume level.

With the other relay, I personally would use a mid-boost on the tone stack. The mids make alot of the overdrive tone. The values I have here would give you either a .00125  (.001 & 250p)  or around 500p  values.

Two relays ............... two boosts to choose from.   I attached a SCH schematic for you.

There are a number of other Hoffman Plexi 50w ideas here:
http://www.el34world.com/Forum/index.php?topic=581.0

With respect, Tubenit

[tubenit]

And while it is just a personal thing and not necessarily "better",  I prefer the OD after the clean channel instead of inside it.

With respect, Tubenit

[YardBirdFan]

Thanks tubenit!  Great ideas!  I might go there.  I did fail to mention that the original idea was to have two of the relays triggered by the same switch... that would be one dedicated to kicking in the extra stage, then another dedicated to taming the signal back down AFTER it has saturated the next stage... probably prior to the effects out so any effects device can get its best level regardless of the "mode" that I am in.

One more thing to mention... I am HOPING for the ultimate clean tone when in that mode.  Maybe this isn't the amp to use in persuit of that.  I KNOW this configuration can nail the overdrive thing when the extra stage is kicked in, but can I do Dick Dale sound too?  At some point I would like to build a ReVibe to put into the effects loop.  Maybe for clean I should be building another amp to use 6L6GC blackplates with... dual showman or twin style power.

At some point soon I will need to check in with Doug to see if he has any of the old style relay sockets.  I would need at least one to deal with the existing layout on the board.  I could certainly use the new style for the 3rd relay.

The idea of footswitchable effects of course is to avoid sending signal through the effects at all times... only send out and back when needed.

Your second schematic surprised me.  Is that some sort of transistor component in the overdrive?  Bear with me... I am a novice!

[tubenit]

Two relays triggered by the same switch

Do you mean two switches triggered by the same relay?

You're wanting great overdrive and Dick Dale both with the extra gain stage in?   

The thing you're wondering about is a mosfet used as a cathode follower.  You can do search for more info.

Revibe typically goes into the front end of the amp.

With respect, Tubenit

[YardBirdFan]

No, the same 5V activation voltage passed along from the same switch would activate two of the three relays is what I was thinking.  I might be walking on dangerous territory though.  If the downstream relay that would bring the signal back down should ever fail, It might cause some surprises!

The clean I am hoping for probably isn't going to happen with any EL34 equipped amp.  I would like to do the best I can with this though, having a fairly un-clipped signal much of the time.  Most of my playing is with settings quite clean.

I am going to do some searching on the mosfet cathode.  I have never heard of that before.

[YardBirdFan]

You're wanting great overdrive and Dick Dale both with the extra gain stage in? 

I just re-read my statement.  I sure butchered it.  I better do some better proof reading from now on!  SOOO sorry.

I meant to say "while in the clean mode..."  that is obviously where I would try to emulate Dick Dale clean.  Again, I know this amp isn't go ALL the way there, but I would like to make sure I still have a clean mode that can get as close as I can get. 

In the overdrive mode, I don't want the level to leap up as I have witnessed the hotswitch "on" mode will do.

The hotswitch "on" mode is otherwise WAY cool too... even though I will not use it as often as clean.