What is this mod to 2204

Brontosaur · Post by **Brontosaur** » Mon Feb 07, 2011 4:15 pm

I took out the low input because I didn't use it.

I'm still tweaking things but I keep amazed at the loads of gain and punch it can deliver now.

I added a resonance control (thanks to Novosibir I went from 1M /.0047uF to 250K/.0022uF), which tighten the lows, a variable feedback (220K pots to the 8 ohm tap) and two switches to add diode clipping (arrgh) : 5V Zeners at MV and and a LED combo at V2 cathode. It's like cooking : adding salt or pepper, garlic or parsley, sour cream or onion make the the recipe tastier !

I may gig it soon.

MVDW · Post by **MVDW** » Tue Feb 08, 2011 8:25 am

Hey Brontosaur. Sounds great. I was wondering where you've put the zeners, across the normal MV or across a Jose MV?

I don't have a Jose MV and I was wondering if it works the same way with a normal MV. Cheers.

Brontosaur · Post by **Brontosaur** » Wed Feb 09, 2011 7:02 am

I put them across the normal MV. The effect is subtle, and emphasizes as you put more gain. Enough for me, I use it to have more sound shaping options. Some may consider it useless but it helps tailoring your - already good - tone.

Moreover, I had to fill the empty input holes

!

MVDW · Post by **MVDW** » Wed Feb 09, 2011 7:52 am

Cheers. I'm about to do this to my build, you can check it out here:
http://forum.metroamp.com/viewtopic.php?f=7&t=34552" onclick="window.open(this.href);return false;

I'm going to get me some zeners, maybe 5V or 20V, and a couple of normal diodes, see what's best. Then if I like it, I'll get a push-pull pot to switch them in and out. Have you tried putting them before the tonestack in the typical Jose master setup, just without the master pot? I'm wondering if it matters if you put them there, or after the tonestack like a normal MV.

I was on some sort of a quest to get a super aggressive sounding Marshall. I'm almost there. My build has a switchable extra gainstage in front of a 2204 so the effect might be more noticable.

Brontosaur · Post by **Brontosaur** » Wed Feb 23, 2011 4:14 pm

Groovenut wrote: A 100k grid stopper has been added to the second GS as well as a 1M grid resistor. The grid resistor has the effect of changing the output impedance of the 1st gain stage as the gain is turned up and reducing bass a small amount. This is where things get really interesting. The treble peaker has been removed and there is an additional 100k in // with the usual 470k giving a total series resistance of 82k. I cant really tell what the shunt resistor is there. If it is a 470k or a 100k. I would guess a 100k this would decrease the bass from the second stage.

I'm curious about those changes if put on a normal 2204. How much bass the grid stopper would reduce ?
Would that affect gain ? I can't figure it. Have to open the amp desolder, etc.

fusionbear · Post by **fusionbear** » Sun Apr 29, 2012 11:47 pm

How are you guys liking this mod? I am going to start my build this week and want to avoid adding a gain stage. I really like the classic 2203 sound, but with just a little more saturation/gain. I don't want to use the PPIMV mod.

jerrydyer · Post by **jerrydyer** » Mon Apr 30, 2012 3:54 pm

if you just want more saturation and gain I wouldnt use that schem at all. heres a quick mod for you to check out if its a standard 2203.. put a 2700 pf over the gain pot, the in and out. just see if thats the right direction and then we can get back a little bass we might lose doing something else.

fusionbear · Post by **fusionbear** » Mon Apr 30, 2012 11:01 pm

jerrydyer wrote:if you just want more saturation and gain I wouldnt use that schem at all. heres a quick mod for you to check out if its a standard 2203.. put a 2700 pf over the gain pot, the in and out. just see if thats the right direction and then we can get back a little bass we might lose doing something else.

Hello Jerry,

Silver Mica? Or what do you like? Are you talking about the wiper and the in into the pot? Thanks!

jerrydyer · Post by **jerrydyer** » Tue May 01, 2012 11:42 am

you can use whatever. I had some cool mustards at 2700pf sound killer right there. over the in and out (wiper and in ) might lose a little low end. put a 22uf over the 820ohm going into the tone network, or a 1uf is fine. depending on the amp. some get flubby there. I like changing that first cap after the first gain stage to a 1000pf from 470pf. these tow alone will give you a nice boost. change the 10k res on v1b to 4.7k or 2.2k depending on your amps response to it. or leave the 10k and bypass it iwith a 1uf. (soldano and some others)

fusionbear · Post by **fusionbear** » Mon May 07, 2012 1:20 am

jerrydyer wrote:you can use whatever. I had some cool mustards at 2700pf sound killer right there. over the in and out (wiper and in ) might lose a little low end. put a 22uf over the 820ohm going into the tone network, or a 1uf is fine. depending on the amp. some get flubby there. I like changing that first cap after the first gain stage to a 1000pf from 470pf. these tow alone will give you a nice boost. change the 10k res on v1b to 4.7k or 2.2k depending on your amps response to it. or leave the 10k and bypass it iwith a 1uf. (soldano and some others)

I ended up using 1750pf on the gain pot. I tried 2700pf, 2200pf, a little too much for me. I tried the 1uf over the 820, but that added a lot of hiss even though it sounded really thick. So, I changed the 10k on V1b from 10K to 5.6K and that sounded really great. I am going to leave it like this for a little while and play it. You know how amps settle down after some hours on them.

I fired up this amp and my Splawn and A/B'd them through the same Splawn cab. Wow! I didn't notice how much more upper-mids there are in the Splawn compared to this circuit. I am going to post my amp in the DIY thread so as not to derail this thread anymore...

uiovbged332 · Post by **uiovbged332** » Wed Jul 06, 2022 2:23 pm

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