Fender Pre and Bassman Volume questions

[Structo]

As long as those relays fit a DIP socket they're fine unless you are trying something else.

Here is a layout of the D'lite foot switch relays.
Ignore anything that this is switching.
This is just to show how the power is applied and the switching.
Notice how the B+ is connected to one side of the coil then the switch is on the - side of the coil. Completing the - side turns the relay on.

On your amp you can wire to use a TRS jack and plug.

Here is a layout just to show the footswitch wiring.

[Subjecttochange]

Do you think it'd be possible to run an LED on the footswitch when the relay is on?

Run the powered line through LED+resistor into the 3PDT switch. then the return. And, since I am only running one relay- do I really need a TRS? I do have the jack and all if I need it.

I got a pretty sweet little LED that's green or red depending on the way the current flows- I figured I might wire it up so that the switch could change the direction into the LED- making for a "green" and a "red" channel... but that's only if I have a return bypassing the relay I guess. Ok... maybe not

Also- Just curious but I have never heard of replacing the 82k/100k with 120ks. How does that make it lively-er. I think I may try it out. I'm still new to this whole building process... and this project may have been a bit ambitious. But hey- how can you learn if you keep building champs over and over?

[Structo]

Since it is only one function of either one of the preamps you need two wires to run to the footswitch.
If you want an led you can run it in series with the wire.
Not sure about the dual color led, I think you have to run another wire to power the other half of the led.

Here is another schematic that might help.

Of course this is for the D'lite and two relays but it should help to give you an idea of how to go about putting it into your amp and wiring the footswitch.

I think since you only plan on running one relay, you don't even need a regulated supply, just the diodes and caps for the power supply.
I believe this schematic shows a voltage doubler the way the diodes are then R value is chosen to drop the voltage to what you want.
On the D'lite it is a 56R 1W.

As for the PI plate resistors, it is just one of those things you have to experiment with to know if you like it.

Here is Aiken's take on it with some good information about the LTP and the associated resistors.
Concerning plate resistors:
Since there is local feedback in this stage, this is larger than the standard preamp stage output. These resistors also have an effect on frequency response. Higher values will result in less high frequency response.

http://www.aikenamps.com/LongTailPair.htm

[Subjecttochange]

Tested out the addition of my recovery stage ad per the latest drawing (except the cathode is 820R, and there is no resistor into the PI coupling cap).

It gets all sorts of angry crazy noise... not good noise though. I am going to put in a 100k and raise the CC to 0.022uF to see if that helps.

As for the footswitch- I haven't wired it up yet and I just got some last minute stuff to do this afternoon. lame... looks like it'll have to be done tomorrow.

I also was using the D-lite as my only source of relay info. Yeah- I was just planning on simple diode+ a little filtering- straight into the relay- I figured the rest wasn't needed (along with the TRS).

So for those plate resistors- even though they are cutting a bit of the highs- you still feel like they add life to the amp. Could it be more the ratio? Since 100k/82k is almost an 18% differential and 120k/110k is more like 9%? I wonder if bumping up the 82k a bit would have the same effect w/out cutting a bit of the highs (probably not detectable anyway)? Maybe a 1M+100k in parallel?

[Subjecttochange]

With the new recovery stage it is much louder- much more like a 50W amp! But... it sounds like:

A. There is way too much distortion even on low preamp settings.

B. Past say 2:00 on the master volume- it sounds like the amp is overloaded and goes very quiet- like there's just way too much signal trying to get through... what should I check/fix?


EDIT: Oops... no grid leak resistor. I put in a 470k and it's not overloading anymore... just too much drive now... I am going to try raising the cathode cap to 2.2k. maybe a few more tweaks on that gain-stage.

[Subjecttochange]

Still not quite there yet... that last "recovery" stage adds too much drive/clipping- even with a 1M grid leak and a 2.2k cathode trying to reduce the gain.

Also- haven't gotten the switching mechanism working either. Tried wiring it up a few times... and it hasn't worked yet- just introduces a lot of noise. Do you think the best way to wire it is before the first gain stage or right before the recovery gain stage?

I'll draw out a few to see what you guys think.

[Structo]

I think I would try it right before the recovery stage.

Did you try the amp without the recovery stage and just the mixing resistors?

[Subjecttochange]

Yeah I tried the two mixing resistors right before the coupling cap into the PI. It just doesn't have the volume an amp this size is supposed to. I'm still unclear as to why that is though... I mean- I am using the same basic layout as in the wreck or the bassman. Neither amp sports any more triodes in their respective preamp signal paths than my original design... and maybe I am missing it- but I don't see any stages before the PI on vibrato/trem/verb fender models on their normal channels... I dunno.

I did not try using the relay as a switch between the two channels respective mixing resistors sans the recovery. This would alleviate the need for that recovery stage... wouldn't it? I'll probably try both for good measure.

That'll be on the menu for tomorrow.

[Subjecttochange]

There are the arrangements I am going to try. They look ok? Also- I may omit the resistors in the mixing area as I see fit.

Any problems?

[Jana]

just some random observations:

Is that a typo or do you really have 0.47 uf caps for the coupling and tone caps in the fender section?

10uf isn't much filtering for all those pre-amp stages you have in that leg of the B+.

[Subjecttochange]

No... they really are .047uF haha.

Second- the filtering. Should I add an extra 20uF? I thought it was a bit stingy too. Don't know how much that'll help my other issues... but what the heck- I'll test it out... I have got a few turrets left and can fit another E cap.

[M Fowler]

This amp has taken on a whole new life since I last visited this thread.

[Subjecttochange]

Sure has! Welcome back. I'll be back with more updates after the little soldering session tonight.

Had to break for the US/Canada Men's Hockey game.

As much as it would have been nice to see the US win... Canada deserved the game. I just feel bad for Ryan Miller- the guy did great- his defense-men were just out to lunch for most of the game.

[Subjecttochange]

This is the current state... the switching isn't really happening. I mean... I am switching the voltage on/off as it is reading on the fs/relay but the channels aren't switching- in fact- it's still making making some sort of connection with all volumes off.

I currently have the recovery stage out... it needs to go back in though. Fowler was dead on. It needs it. It makes this amp sound like <5W amp without it. What is the best way to implement it without inducing clipping/distortion? Last time I had no cathode bypass cap, a 2.2k cat resistor, and a 1M grid leak resistor as well as both 220k as mixing resistors into the stage and a 100k into the coupling cap on the PI... still induced too much drive.

This is the relay I am using... and I have it wired exactly like the schematic... Should I be using something else or did I just make a stupid mistake?

http://www.mouser.com/ProductDetail/Tyc ... 1osBUvQ%3d

[Structo]

Boy, I'm not sure.
I wonder if it has anything to do with the way the input is connected?

Since the jack goes to both preamp stages.

You may want to try to put the input on the other side of the relay and switch that as well.

Not sure if this will help but I was trying to find another channel switcher that would be comparable to yours to see how they handled the two channels.

Here is a Mesa Maverick, it has a switch or relay on one of the channels and they both go to the phase inverter with nothing special really.

http://www.schematicheaven.com/boogieam ... verick.pdf

Another one:
http://www.schematicheaven.com/boogieam ... toverb.pdf