Butta's 3630 secret recipe

[therecordingart]

Couple questions....

-The 220uf and 2200uf caps....which caps on the PCB am I replacing with these? Next to the power plug there are two different sets of two 1000uf caps, so I don't know which to swap. I'm also not sure where the 220s go.

-As far as the 1uf cap that goes to pin 2 and 5 on THAT 2252....solder to the underside of the board?

-Replacing the power plug....just pull it from the PCB and solder a different one in its place? Am I only doing this so I can use a different power supply?

So far I'm planning on replacing everything listed in these mods except for the diodes. Do those really have to go or should I be ok?

 

[therecordingart]

Also....the link to the 3630 schematic in the meta doesn't work. Does anyone have the schematic?

 

[rascalseven]

Just another post to give props for this mod: Awesome stuff, Butta!

I did the power supply mod, and also altered the star-grounding based on some other bits I found around the internet (don't really know if this new grounding scheme helped as I didn't do comparisons beforehand), and I swapped opamps, though for the audio portions I used different ones than Butta suggested: I found a guy who makes a cool little quad opamp replacement circuit that uses two surface-mount OPA2604's in a TL074 DIP footprint/pinout. I also dropped the timing cap used for Peak reduction from .1uF to .01uF according to the THAT datasheets I read over. Lastly, I removed the -10/+4 switches on the back and hardwired all channels in +4 mode.

I absolutely love these boxes now (I have two), and I actually just had a local recording snob over to my studio last week to track drums (I was playing, he was engineering). This was the first time he's been over, and it was sort of a test to see if we would continue working together in the future. Anyway, he's used to tracking on an api console, tons of amazing outboard, etc. I've got several Neve and API pre's myself, but not a bunch of expensive compressors, and he rather poo-pooed the Alesis units, even after I told them they were modified.

Since I didn't have many other units, he reluctantly patched in three of my four channels and was totally shocked by what he heard. He used them in both RMS and Peak modes, and loved the flexibility and the sound of both units. He stopped short of asking me to mod one for him, but he gushed on them for a little bit, so I was very pleased.

This dude is not quick with compliments either, so I know he was impressed.

BTW, on one of my units I changed the RMS timing cap and resistor values to the values on THAT application notes, but the sound pumped more and didn't sound as musical to me. So I switched them back to the Alesis values (which I think are actually values dbx used.... someone please correct me if I'm wrong here), and the GR character is just awesome... even with insane amounts of reduction (-30dB!!) there are almost no audible artifacts, certainly nothing unpleasant.

Also, I have yet to change any of the 2150's with trim networks for 2180's, though I just got some 2180LC's today, so I'll probably drop a couple in one of them and compare. I'm interested to see what difference 2180's will make.

:green: :thumb:

JC

 

[early3630owner]

I just found this thread last month.
I have one 3630's from the mid-90's.
I would like to do the mod.
Despite all of the excellent info you have put together, I am unable to determine exactly what I supposed to do with some of the mods.

I'd buy the Black Lion mod but it was no longer by the time I found this info.
Does anyone have a clear step-by-step a noobie DIY'er could follow?

thanks

 

[early3630owner]

I finally managed to get all the parts.
Will be doing the mod this weekend or so.
I would appreciate it if someone would let me know if I have the following correct:

1) The A/C jack is only being replaced to accommodate a larger size plug.
Someone mentioned the Line 6 PX-2 PSU negates the need to replace the receptacle.
Are both of these true?

2) The four large caps in the power supply section are being replaced with two short 2200uf 25v caps that fit under the secondary circuit board and two 220uf 35v caps (what did butta mean by 'nice') towards the edge.

3) The four power diodes are being replaced with IN400x model diodes.
It looks like mine are 4001.
Will I gain anything by replacing them with 4003 or 4004's?

4) The three LF347N quad opamps are being replace with MC33079's installed into DIP sockets.

5) The THAT 2252's are being left in place, but a 1uf 50v cap needs it's '+' connected to the 2252's pin 2 & the cap's - to V- (ground? or pin 5 on the same 2252?).
I have a Rev D board.
There are caps at C8 & C26 that connect + to pin 2 on the 2252's they are next to & the trace on the - side leads to a jumper & pin 5, so I'm thinking this is done already.

6) Replacing the two THAT 2150A's with two 2180's installed into SIP sockets with pin 4 removed.

Question:
- Butta talks about cleaning up the ground.
He said it's using 'star' grounding that's not very good, but it wasn't clear to me what he did to 'clean it up'.
Can anyone clarify this?

Thanks once again for taking the time to help.
I really appreciate it.

 

[SonsOfThunder]

I can answer a couple of these, hopefully before you start...

3) No...you want to use a different kind of diode if you are concerned with such. 1N400x are all basically the same except for the voltage.

4) Uh NO.. they won't power up correctly. You shouldn't be cutting any pins on the opamps.

B) I think that several possibilities are mentioned in this thread or perhaps another. Search for 3630.

HTH!

 

[mrc]

I'm sure the PX-2 fits into the stock socket,

 

[smallbutfine]

I agree, you won't gain anything with another IN400x diode, but there are faster diodes that sometimes add a little to sound quality. (UF?)
'Nice' means good sounding (audiophile) like sanyo oscon, panasonics, elna, somting like this...

 

[early3630owner]

Thanks for the replies.

SonsOfThunder
RE: #3 - I will leave the diodes alone if the ones in there are fine.
RE: #4 - My mistake. Cutting pin #4 is for both of the THAT 2180 VCAs SIP Sockets.
I have edited the above post to clear that up.
RE: Question #B - I purchased the MC33079 after discovering I could get them from Mouser through my employer.

mrc
I picked up a 1.7 Amp Universal PSU for $17 with an assortment of tips.
Does anyone know if the 3630 is positive (+) tip or negative (-) tip?

smallbutfine
RE: #3 - I will leave the diodes alone if the ones in there are fine.
RE: #2 - Thanks for the info. The Caps are my greatest concern.

I purchased 25v 2200uf UCC Mini Radial Aluminum Electrolytic Caps (Mouser part#: 661-EKMGG250ELL222MK) to replace the two caps on the rear edge.
These are noticeably bigger than the stock 3630 caps, but look like they fit OK.
I purchased 35v 220uf Nichicon Radial Aluminum Electrolytic Caps (Mouser part#: 647-URS1V221MNA) to replace the caps that sit towards the middle.
These are smaller in diameter and about half as tall (or long) as the stock 3630 caps.
I don't know anything about caps, so I don't know if this will cause any issues or not.
The stock 3630 caps in this position are 25v 1000uf and bigger in size than the stock edge caps, which are 16v 1000uf.

 

[SonsOfThunder]

>>>I picked up a 1.7 Amp Universal PSU for $17 with an assortment of tips.
Does anyone know if the 3630 is positive (+) tip or negative (-) tip?

The output needs to be AC...so its neither + or - :green: A DC supply will not work.

If you want to replace the rectifier diodes you want "soft recovery" types. If you don't know what this means, just leave them alone. They "could" make the unit quieter...


HTH!

 

[early3630owner]

The output needs to be AC...so its neither + or - A DC supply will not work.

uh.. yeah, I knew that...
Thanks for the heads-up!
feel like moron.
will return it & get the PX-2 then!

They "could" make the unit quieter...

Yeah, I got the impression the benefit from changing the diodes was almost negligible.
I don't want to mess those, the Caps are confusing me enough as it is. :?
I hope someone will clear that up for me before I get to that point in the process.
I plan to do the Caps last.

 

[VinceNY]

I own a 3630 vintage 1995 and took a look at it with the following comments, some of which are already part of the mods described here in these posts.

1. Noisy Oamps

2. Lack of buffering at the ouput required to reasonably drive a cable with any length and its associated capacitance. (New)

3. VCA related- Driving the control port with a LM339 comparator configured as a low frequency opamp in series with a 680 ohm resistor.
VCA control port must see a low impedance in order to insure stability and minimize THD and Noise. (new)

4. Insuffucient Energy storage in the on-board power supply (new)

5. Wall Wart- If yours is rated at 9 volts AC the easy fix is to replace it with a 10volt AC or greater unit at 1amp or greater. In general the PSU design is terrible and needs a major rework. The burping that some of you have experienced can occur when the input voltage to the LM78 and 79 15 volt regulators drop below about 18vdc. This causes them to drop out of regulation which impresses an audiable burp on the otherwise Dc voltage.

6. Schematics- both of the schematics that are posted contain errors so beware, although, they are close enough if you use guidance from the THAT data sheets and application notes to resolve any ambiguities.
I must add that tracing the circuitry and generating the schematics is a somewhat daunting task and I certainly can appreciate the effort by the persons who generated them.

Over the next several months I will post the modifications to improve the shortcomings as I see them.
VinceNY

 

[khstudio]

VinceNY,
Good to see you here :thumb:

Looking forward to your findings as well. I have heard great things about the mods that are listed in this thread already but haven't had time to try them on my unit yet.

Thanks buttachunk & everyone for their effort.

 

[VinceNY]

Wall Wart:
Just a quick note to the more is better crowd. Limit the measured AC RMS noload output voltage to 12volts RMS unless you decide to change C4 and C5 (currently 25 VDC) to a higher voltage rating (35VDC).

VinceNY

Kevin
Love the DIY equipment on your website especially the L2A, great workmanship.

 

[khstudio]

[quote author="VinceNY"]

Kevin
Love the DIY equipment on your website especially the L2A, great workmanship.[/quote]

Thank You :green:

I have a TON more to post... Like about 10 Guitar Amps. I love building amps... go figure, I'm a drummer :razz:

 

[AMZ-FX]

For reference, here is my drawing of the power supply:

regards, Jack

 

[khstudio]

Is that the original supply or upgraded?

Not much to it.

 

[AMZ-FX]

That's a drawing of the original to show which caps need to be upgraded.

The 9v regulators connect to the power on the right side and provide +/-9v to the rest of the circuit.

I might upgrade the 4.7uf on the output of the regulators to a good low impedance 10uF electro.

regards, Jack

 

[VinceNY]

I would like to post a schematic for this but currently have no facility to do so. Can anyone help?

3630 Regulator Mods

Here is a schematic for Version 1 of the regulator modifications. Some of the changes are a summary of what has been discussed here and some are new.
If you change C1 and C2 as shown to 2200uF keep the 1000uF caps and put them in the C6 and C7 position. Add 0.1uF chip capacitors(C4a, C5a, C6a, C7a) on both side of the +/- 15 volt regulators to ensure stable operation. Diodes D1a-D4a are added to avoid regulator failure due to output and input shorts required when C6 and C7 gets large like 1000uF. This will also be useful when a probe winds up in the wrong place when making measurements. Add heatsinks to both regulators and don't forget to apply thermal compound between the regulators and heatsinks. Due to the limited space between the regulators you will need to use compact outline heatsinks insuring that the two heatsinks dont make contact and short as the regulators are at different potentials.

Parts List Version 1

Qty Manufacturer Description Part # Cost

2 Panasonic 2200uF 16v Electro. C2,C3 ECA-1CM222 $ .82each
4 On Semi Diodes D1a-D4a 1N4001 $2.27/10
4 Panasonic 0.1uF Chip cer. C4a-C7a ECJ-3VB1H104K $3.96/10
2 AAVID Thermalloy To-220 Heat Sink 577102B00000G .36each

More to Come
VinceNY

 

[VinceNY]

Click on the link below for the schematic, I hope.

Vince NY

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