80s Mod Board in the works

V2a

V2a

Active member
Here's a photo showing a little panel-mounted module with switchable circuits. The first circuit alters the gain "Structure" in a typical 2204-type preamp, and the second circuit (that I call a Cali Clipper) utilizes semiconductors to add distortion/saturation.

Gonna start making a batch of these with black PCBs shortly. Can be added to 2204s, clones, Soldano Atomic 16, Jet City, and many other higher-end amps. Just gotta have ~3 on the back panel for mounting...

rTPDcIg.jpg
 
Nice! Is this inserting between V2 cathode? Different bypass cap/ resistor or more than that aside from the clippers?
Cool idea. Are the pots aligned to be able to go in the speaker jacks on an amp with 4 jacks, or will drilling be necessary?
 
I would assume that anyone savy enough to install the board could do the mods without having to buy a board. The cathodes bypass selections can be done without the external board and the clipping as show is more Friedamesque than Jose, which is not the ideal placement.
 
glip22":1jny4o58 said:
Nice! Is this inserting between V2 cathode? Different bypass cap/ resistor or more than that aside from the clippers?
Cool idea. Are the pots aligned to be able to go in the speaker jacks on an amp with 4 jacks, or will drilling be necessary?
Click to expand...

There are two miniature switches mounted onto the board that also mount to the panel, so new 1/4" holes are required. For the first boards, the switches are 2.5" apart. The Structure/punch switch alters the cathode of the second gain stage, whereas the clipper comes after the cathode follower.
 
scottosan":207lyx1e said:
I would assume that anyone savy enough to install the board could do the mods without having to buy a board. The cathodes bypass selections can be done without the external board and the clipping as show is more Friedamesque than Jose, which is not the ideal placement.
Click to expand...

People could choose to use a board like this one or rig it up in "PTP" fashion without a board. This board idea grew out of my own desire to wire up the two circuits in an amp that I've got listed in the classified section. With little space in that chassis, the board made good sense to me. Your solution might have been different, which is certainly fine with me.

As for the various clippers, there really is no "ideal". Some clippers go early on in the preamp (e.g., Jubilee), whereas some go at the end of the preamp (Jose, Friedman, Cameron, Fortin, etc.). The placement of the coupling cap isn't too critical; you just need to keep DC off the semiconductors (and pot, if one is used).
 
V2a":3metdlkv said:
scottosan":3metdlkv said:
I would assume that anyone savy enough to install the board could do the mods without having to buy a board. The cathodes bypass selections can be done without the external board and the clipping as show is more Friedamesque than Jose, which is not the ideal placement.
Click to expand...

People could choose to use a board like this one or rig it up in "PTP" fashion without a board. One will be tidier than the other, most likely.

As for the various clippers, there really is no "ideal". Some clippers go early on in the preamp (e.g., Jubilee), whereas some go at the end of the preamp (Jose, Friedman, Cameron, Fortin, etc.). The placement of the coupling cap isn't too critical; you just need to keep DC off the semiconductors (and pot, if one is used).
Click to expand...
With the Friedman implementation, more of the clipping is actually coming from the loading down of the cathode follower than from the transistors. The Fortin and Cameron (Jose) implementation allows for a wider variation of clippers to be used and cleans up much nicer and wouldn't be possible with the external board without rewiring the MV and tone stack. Again, just my 2 cents, it would be more appropriate to call it a SAT switch rather than a "Cali Clipper" as that might lead one to believe they are doing a more traditional Jose type implementation, which is not the case. None the less, this will get most people more in the BE type structure and SAT mods.
 
scottosan":1sr1owvh said:
V2a":1sr1owvh said:
scottosan":1sr1owvh said:
I would assume that anyone savy enough to install the board could do the mods without having to buy a board. The cathodes bypass selections can be done without the external board and the clipping as show is more Friedamesque than Jose, which is not the ideal placement.
Click to expand...

People could choose to use a board like this one or rig it up in "PTP" fashion without a board. One will be tidier than the other, most likely.

As for the various clippers, there really is no "ideal". Some clippers go early on in the preamp (e.g., Jubilee), whereas some go at the end of the preamp (Jose, Friedman, Cameron, Fortin, etc.). The placement of the coupling cap isn't too critical; you just need to keep DC off the semiconductors (and pot, if one is used).
Click to expand...
With the Friedman implementation, more of the clipping is actually coming from the loading down of the cathode follower than from the transistors. The Fortin and Cameron (Jose) implementation allows for a wider variation of clippers to be used and cleans up much nicer and wouldn't be possible with the external board without rewiring the MV and tone stack. Again, just my 2 cents, it would be more appropriate to call it a SAT switch rather than a "Cali Clipper" as that might lead one to believe they are doing a more traditional Jose type implementation, which is not the case. None the less, this will get most people more in the BE type structure and SAT mods.
Click to expand...


Well, Friedman is in Cali too, which is part of the reason for the 'cali clipper' name... :)

This design is perhaps more versatile that you may think. The board in the photo has zeners as well as transistors. Both work well, in my opinion.

In your opinion, why does the pre-tone-stack (Jose) Master improve the circuit?
 
V2a":3el49owa said:
scottosan":3el49owa said:
V2a":3el49owa said:
scottosan":3el49owa said:
I would assume that anyone savy enough to install the board could do the mods without having to buy a board. The cathodes bypass selections can be done without the external board and the clipping as show is more Friedamesque than Jose, which is not the ideal placement.
Click to expand...

People could choose to use a board like this one or rig it up in "PTP" fashion without a board. One will be tidier than the other, most likely.

As for the various clippers, there really is no "ideal". Some clippers go early on in the preamp (e.g., Jubilee), whereas some go at the end of the preamp (Jose, Friedman, Cameron, Fortin, etc.). The placement of the coupling cap isn't too critical; you just need to keep DC off the semiconductors (and pot, if one is used).
Click to expand...
With the Friedman implementation, more of the clipping is actually coming from the loading down of the cathode follower than from the transistors. The Fortin and Cameron (Jose) implementation allows for a wider variation of clippers to be used and cleans up much nicer and wouldn't be possible with the external board without rewiring the MV and tone stack. Again, just my 2 cents, it would be more appropriate to call it a SAT switch rather than a "Cali Clipper" as that might lead one to believe they are doing a more traditional Jose type implementation, which is not the case. None the less, this will get most people more in the BE type structure and SAT mods.
Click to expand...


Well, Friedman is in Cali too, which is part of the reason for the 'cali clipper' name... :)

This design is perhaps more versatile that you may think. The board in the photo has zeners as well as transistors. Both work well, in my opinion.

In your opinion, why does the pre-tone-stack (Jose) Master improve the circuit?
Click to expand...
In my opinion, It's not just the placement of the MV, but the placement of the tone stack as well.

The traditional Jose, the MV and tonestack are inline with the 10k and .22-.33uf cap and clippers going the ground off the MV

The Friedman implementation has the 10k and cap and clippers are bifurcated from the tone stack. Now whether that was by accident or design, I do't know but the end result is that the loading down of the CF which in itself causes alot of distortion and volume drop in spite of the clippers. I use some combination of clippers in a Jose circuit that have little to no affect in the Friedman style implementation.

Again, not intended to bash the idea, because it will give alot of the variation the BE offers
 
I don't really care if the Zeners come before or after. I think this is a great idea and I have a home built 2204 with plenty of space to drill in the back that would gladly accept this circuit. Consider me in for one. I trust there will be some documentation on how to wire/ solder this in? What are you thinking price wise? Put me on the list.
 
scottosan":1sh4uf5m said:
In my opinion, It's not just the placement of the MV, but the placement of the tone stack as well.

The traditional Jose, the MV and tonestack are inline with the 10k and .22-.33uf cap and clippers going the ground off the MV

The Friedman implementation has the 10k and cap and clippers are bifurcated from the tone stack. Now whether that was by accident or design, I do't know but the end result is that the loading down of the CF which in itself causes alot of distortion and volume drop in spite of the clippers. I use some combination of clippers in a Jose circuit that have little to no affect in the Friedman style implementation.

Again, not intended to bash the idea, because it will give alot of the variation the BE offers
Click to expand...


I'm not taking this as bashing (of my mod board), and I'm always happy to discuss circuit design. I usually end up learning something new that way.

Most or all of these variations were covered in Kevin O'Connor's first TUT book (mid 90s) and in subsequent installments. Kevin gives a good description of at least most components of the circuits. In my case, I added the blocking cap in the shunt circuit rather than as a series coupling cap because I didn't want to cut the nice traces of the Egnater PCB. And it works swimmingly. There's no real problem of additional loading the CF because
(1) the output impedance of the CF is very low, and (2) the CF is always the first stage to be distorted (see the Blencowe preamp book for a good explanation). And in the case of Friedman's SAT switch, the transistors clip at 4V (the output of the CF can be 100V). That is the reason for the massive volume drop of the SAT switch (and the volume drops in all clipping circuits).
 
Kapo_Polenton":3mx7d99o said:
I don't really care if the Zeners come before or after. I think this is a great idea and I have a home built 2204 with plenty of space to drill in the back that would gladly accept this circuit. Consider me in for one. I trust there will be some documentation on how to wire/ solder this in? What are you thinking price wise? Put me on the list.
Click to expand...

I'll mark you down for one. I haven't firmed up the price but it won't be more than $50 (will try to come in well under that, but my favourite miniature switches are frikken $10 each... grrr). I'll include some documentation and a drill template. I'll also include a statement that the 'kit' should be installed by a qualified technician. You know, the usual 'tube amps can kill you' routine...

-- John
 
I think its a cool idea, given that it delivers the intended tones. I know a player or two who would be able to install this, but would not try to install this same mod within the original pcb. Its all whats familiar to you and how far beyond that you are willing to venture ;)
Plus, it looks like it would be easily reversible.
 
Meant to ask, I know the level of gain that comes with zeners as I have tried that mod in my 2204 but what about the first mod/tweak, how much gain are we talking and what would be comparable? I trust that the mod can be either in or bypassed? Either way I am still in as I have two 2204's. My 1982 stays more or less unmolested and my home build can turn into whatever.
 
Kapo_Polenton":2mmfm9af said:
Meant to ask, I know the level of gain that comes with zeners as I have tried that mod in my 2204 but what about the first mod/tweak, how much gain are we talking and what would be comparable? I trust that the mod can be either in or bypassed? Either way I am still in as I have two 2204's. My 1982 stays more or less unmolested and my home build can turn into whatever.
Click to expand...

Yes, the structure circuit can be bypassed. The second gain stage of the 2203/4 has little gain in the stock configuration. Lots of hot-rodded amps increase this gain by re-configuring the cathode circuit, and many amps make this a switchable function (on my own amps, I have called it punch; some Bogners call it Structure; Friedman calls it 'S'). The Structure switch on my 80s Mod Board can provide a considerable gain boost. The settings are as follows:

UP - highest gain, tight low end
MIDDLE - lowest gain (stock; bypassed)
DOWN - moderate gain boost

Cali Clipper:
UP - on (added distortion/saturation with drop in volume)
DOWN - off
 
Color me interested, especially if it works in a Peavey Windsor! I need to go compare schematics to check that.
 
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