2204 6v6 build

[Auke Jolman]

Inspired by the plexi 6v6 I decided to redo my 2204 6v6 I did ladt year bssed on the ceriatone layout.

I took Doug's plexi 6v6 layout and adapted it to 2204. Only the first and second gain stages needed changing. I kept the high and low inputs. I left out the 100 pF on the first tube socket and also the 500 pF cap paralled with the 470k res from the input to the gain control.

It really amazes me how different (i.g) better the amp sounds, at least to my ears.

Has anybody any ideas as how this is possible.

[kagliostro]

Doug's layout are largely better than Ceriatone's  ? 

K

[topbrent]

I put this up last month, perhaps you will find it useful.  It's 6V6 2204 based on Doug's new stout 6v6 chassis arrangement.


http://el34world.com/Forum/index.php?topic=18223.0

[kagliostro]

Nice 

is this a correct schematic of the mod 5 ?

http://cfile26.uf.tistory.com/image/2623AD4B51A5685928B8E4




Thanks

K

[topbrent]

I used this schematic which has a few slight differences from the one you posted.  This version seems to be more or less the standard recipe for the Mod 5, and the one you posted is one of the alternate, slightly different voicings that exists within the same family.   All info gleaned from the Metro Amp forum and from looking at a lot of pictures of completed mod5 amps.


To be true to the schem, I have an "error" if you want to call it that.  On the 2204 Stout Plexi 6V6 layout that I drew, I forgot to draw the .1uf caps on the phase inverter and I just left the .022uf caps that Doug has on his 6V6 Plexi drawing.   
.022uf caps coming out of the PI would be more in line with true 2204 specs and would/could tighten the bottom end a bit.   The mod5 uses the .1 caps to stay closer to 1968 plexi specs and to add a bit of looseness/boom to the bottom end.  YMMV and do adjust to your taste.

[kagliostro]

Thanks

K

[Auke Jolman]

Thanks everybody for chiming in.

Playing through the amo today, I noticed that the bass is a bit to prominent. What can I do to reduce bass a little.

Auke

[kagliostro]

You can work around bypass capacitors and coupling capacitors


K

[sluckey]

I left out the 100 pF on the first tube socket and also the 500 pF cap paralled with the 470k res from the input to the gain control.

I noticed that the bass is a bit to prominent. What can I do to reduce bass a little.

I'd start by putting that 500pF cap back in. Also be sure you haven't left out any other treble peaking caps.

[Auke Jolman]

I'd like to thank you all for giving me directions and helping me by doing that.

I had put in a 0.022 cap instead of the 0.0022 cap. Changed it and now it is voiced the way I like it.

I  did also put the 100 pF cap in aswell as the 500 pF. I removed both because I found the amp to hsrsh that way.

I'm still thinking about the mod 5. Looks very interesting....

With kind regards,

Auke

[sluckey]

I  did also put the 100 pF cap in aswell as the 500 pF. I removed both because I found the amp to hsrsh that way.

The 100 pF on the first tube socket is a smoothing cap, not a treble peaking cap. It should reduce high end hiss and generally slightly reduce treble. It should not make the amp more harsh sounding.

[Auke Jolman]

Thanks for your comment Sluckey. I've put thee 100 pF back in at the tube socket. Didn't make the amp hars sounding as I first thought.

The other day a friend of mine brought in an 1980 Marshall 2203 wuth a bad pot which I replaced. I noticed a 120 pF parellel ovef the 100k anode res. Does this serve the same purpose as the forementioned cap?o

Also he had a 68k res going from the wiper of the gain pot to ground. Is this a common mod and to what end.

With regards,

Auke

[Auke Jolman]

Hi  guys,

Could any body comment on my previous post please. I really would like to know.

Auke

[sluckey]

The other day a friend of mine brought in an 1980 Marshall 2203 wuth a bad pot which I replaced. I noticed a 120 pF parellel ovef the 100k anode res. Does this serve the same purpose as the forementioned cap?o

Yes, it will cut some high freq signal.

Also he had a 68k res going from the wiper of the gain pot to ground. Is this a common mod and to what end.

I've never heard of that. The 68K is just gonna kill a lot of volume, even when turned up to max.

[Ed_Chambley]

Also he had a 68k res going from the wiper of the gain pot to ground. Is this a common mod and to what end.

With regards,

Auke

Auke, here is a link to a friends page who mods marshall amps.
http://home.comcast.net/~mamp17/Misc%20Mods%20and%20Info.html

He has a nice collection of Marshall mods.  As so far as the wiper to ground, to tell you what it was doing I would need more information.  I have done a lot of marshall mods and have never done anything like this.  By Gain Pot, are you referring to the preamp volume pot which is normally a 1MA pot.  I have added resistors in series to hear what a larger pot might sound like, but wiper to ground would make a balance pot, wouldn't it?

Usually the only 68K is the grid stoppers.

[Auke Jolman]

Thanks guys!

Ed, I do indeed mean the preamp volume pot and yes, it was 1M. I replaced the MV pot. He had it done a few weeks ago, but complaint about the fact that the amp got way to loud to soon. Normily he played with the volume on 3 or 4, but with the pot  he had installed, he could not turn the amp past 1.5. I replaced the Alpha pot with a Bournes pot. This fixed his problem with the volume.

I asked him why he had the 68K installed, but he did not even know it was in there....

Auke