Mesa 20/20 Deep Mod

[RectoStudioGuy]

I decided to make sure it wasn't my ears playing tricks on me. So this morning I made sure I powered on the 20/20 with the deep mod enabled, and used ONLY the deep mod for a while. WOW! :shock: What a difference a night's rest on the ears makes - either that, or I've got some other inconsistency in my rig ... because NOW it sounds GREAT with the deep mod enabled, and now switching back and forth between stock and "deep mod" I prefer the deep mod. Hmmm - oh well ... sorry for the false alarm !

Happens to us all. We take hours tweaking tone only to find we don't care for it when coming with cold ears.

 

[Fury]

This may be a stupid question, but does this mod apply to a DC-3 as well?

So...... Does it?

I am also curious about this........anyone?

 

[crane]

You can try it, it won't harm the amp.
The bypass cap is on V3b, 1uF, same as the 20/20 and same position (just before the PI).
http://www.schematicheaven.com/mesaboogie.htm

 

[Fury]

I like the idea of getting a deeper voice from my amp, but I am apprehensive about messing with my amp (original owner of 13 yrs). It would be cool if the Output Level control could be changed to a push/pull knob. I wish I could hear a comparison somewhere or find out if anyone has actually done this to a DC-3 a opposed to the 20/20.

Thanks for the reply. This certainly warrants consideration.

Cheers

 

[djd100]

If you merely remove the cathode bypass cap you'll lose some gain, so it's better to replace it with something around a 22uf 16V or better cap. They're polarized so watch that when you do this, and watch out for any stored charge in the power supply filter caps (best to discharge them or have a pro do the job etc!).

I've done this to mine and it makes the deep mod much better IMO now that it doesn't lose any gain.

 

[Snoopy551]

Do not put a bigger Capacitor,

Most of people remove the capacitor because the Bass are "Fatry"
If you you changing for a larger capacitor, you will add more Bass.

It is not prefer to remove, but it is OK
If you do not want to remove it, put a smaller. :wink:

 

[djd100]

You're misunderstanding the issue. Most people want more bass and removing the cap removes the stock high-pass that's limiting the bass. Removing that Cathode Bypass Cap also cuts the gain of V1, so adding a bigger cap brings back the gain while extending the low frequency response way lower, which effectively makes the input frequency response essentially flat.

If you don't want bass leave it as is (we're talking bass here as opposed to low-mids).

Do not put a bigger Capacitor,

Most of people remove the capacitor because the Bass are "Fatry"
If you you changing for a larger capacitor, you will add more Bass.

It is not prefer to remove, but it is OK
If you do not want to remove it, put a smaller. :wink:

 

[Snoopy551]

OUps,

You are right that is a misunderstood.
if you remove the cap, you will cut the HI frequency.
If you want more Bass add a Bigger CAP.

At this time,
THe fc~ 100Hz,
if you replace by a 10uF instead of 1uF
the fc~ 20Hz.
Personnally, i already tried but i do not like the Bass.
But that is a personnal choice.

 

[djd100]

Yes, that's right. I find that the mod works well with my preamp which is the Axe FX Ultra, which to me can be a little thin in the bass. I like the mod for cleaner type tones, such as Fender, Vox, Matchless etc. The filtered side sounds good for gain tones in standard tuning, though I can easily create the same roll-off curve via EQ if need be, so I'll be modding both sides of my 20/20 most likely, or maybe adding the push/pull switched volume pots.

I think a lot of the people who like the mod are doing high-gain tones in lower tunings, so they need the bass to go lower?

I just purchased my Mesa 20/20 and I'm quite happy with it, a very nice amp indeed!

OUps,

You are right that is a misunderstood.
if you remove the cap, you will cut the HI frequency.
If you want more Bass add a Bigger CAP.

At this time,
THe fc~ 100Hz,
if you replace by a 10uF instead of 1uF
the fc~ 20Hz.
Personnally, i already tried but i do not like the Bass.
But that is a personnal choice.

 

[Snoopy551]

Following few private email,
i put few of my "mesa 20 deep mode pcb" one Bay
Title: Mesa 20 Deep Mode

 

[sasha]

I found the part number for the push-pull pots from Mouser. Here is the pot. As I remember (4 years ago) I did not have to do any shaft modifications to the pots as well. I think that they dropped right in.

so, i finally decide to go on with this mod on my trusty old 20/20 and mouser gives me a ridiculous quote of $120 for shipping the 3 pots to me

do any of you guys have an idea where one could obtain those push-pull pots online? help out a fellow mesa fan please

 

[Tripoutski]

so, i finally decide to go on with this mod on my trusty old 20/20 and mouser gives me a ridiculous quote of $120 for shipping the 3 pots to me

do any of you guys have an idea where one could obtain those push-pull pots online? help out a fellow mesa fan please

Whoa! Where do you live? I looked at their estimation chart and did not see anything like that! It is less that $5 right now for me, but I am in their 1st zone.

 

[sasha]

so, i finally decide to go on with this mod on my trusty old 20/20 and mouser gives me a ridiculous quote of $120 for shipping the 3 pots to me

do any of you guys have an idea where one could obtain those push-pull pots online? help out a fellow mesa fan please

Whoa! Where do you live? I looked at their estimation chart and did not see anything like that! It is less that $5 right now for me, but I am in their 1st zone.

FedEx International Priority -- 90,83 €
UPS Worldwide Express Saver -- 90,83 €

this is copy-pasted from the checkout page... i live in croatia, europe. still can't locate those exact same pots on ebay... nor somewhere closer

 

[sasha]

to whom it may concern :wink:

http://www.smallbearelec.com/Detail.bok?no=619

 

[Gerax]

Hi all

Any infos or pics about the deep mod in the "switchable by Triaxis" version?
I understad it's been posted on the Triaxis Users Group on Yahoo, but they keep bouncing back my request for subscription...

Thanx

 

[markwayne]

If you merely remove the cathode bypass cap you'll lose some gain, so it's better to replace it with something around a 22uf 16V or better cap. They're polarized so watch that when you do this, and watch out for any stored charge in the power supply filter caps (best to discharge them or have a pro do the job etc!).

I've done this to mine and it makes the deep mod much better IMO now that it doesn't lose any gain.

Ahh . . . brilliant! That's what I've been hearing in the original mod that I didn't like. I now have a set of DPDT push/pull pots coming. My plan is to strap two different caps across each set of terminals so I can implement my own pull deep switch to taste.

thanks again,

 

[markwayne]

If you merely remove the cathode bypass cap you'll lose some gain, so it's better to replace it with something around a 22uf 16V or better cap. They're polarized so watch that when you do this, and watch out for any stored charge in the power supply filter caps (best to discharge them or have a pro do the job etc!).

I've done this to mine and it makes the deep mod much better IMO now that it doesn't lose any gain.

Ahh . . . brilliant! That's what I've been hearing in the original mod that I didn't like. I now have a set of DPDT push/pull pots coming. My plan is to strap two different caps across each set of terminals so I can implement my own pull deep switch to taste.

thanks again,

Just thought I'd update my experience with trying to make a 20 watt amp work for loud, classic rock.

I added the push/pull presence pots. I wired them to switch between a 22uF cap and no cap on one side and a 22uF and stock value cap on the other. I have since gigged it twice with my (ridiculously) loud classic rock band. The good news is that the larger caps really bring the bass way, way up and keep the overall gain high. (I even discovered some 60 cycle hum in my preamps that I had no idea existed after removing the stock value cap.) I am going to go back and snip the stock cap so it'll be a straight pull deep mod. However, I don't see myself ever running it without the larger cap in line. The added bottom makes the EL84s sound closer to EL34s. My Marshall patches (courtesy of a JMP1) and my lead tone (courtesy of my MB Studio) sounded glorious. For a small club gig with a reasonable stage volume, this might be the perfect amp.

The down side is that 22 watts is just not going to be enough for this band. Running the amp just past noon, I had serious, power tube compression and crunch all night. On most things it sounded great, but when I needed a clean wah or funk part, it didn't work so well. Sigh. I'll be bringing a minimum of 50 watts a side with this band in the future. I'll probably just start bringing the Mark IV as a power amp for these gigs anyway.

 

[RectoStudioGuy]

or maybe try a 50/50 or 2 Fifty

 

[D2dark]

i just did the 10uF mod and... man, this amp can rip my face off now, I feel afraid for my v30.

 

[Dewdman42]

Have any of you played around with different speakers in your cab to also compensate for lack of beef in the 20/20, or are we all pretty much in love wtih V30's and no way around that? I've thought about switching to G12H30's or something to get a little more bottom end, but the V30's just have that certain sound so I don't know.