crate vc5212 reverb tweeks

[mjojo]

Hi, my vintage club 50 reverb is terrible. has anyone done any mods to improve the response with this circuit .when used it isn't really noticeable even when cranked except for a nasty long tail when you stop playing.I've seen other people mention this with this model and I'm hoping someone has a solution because this amp is the best thing i've come across in my 8 yr. amp quest.Getting a schematic is impossible. but the vc3112 is at the blue tube site and other than mine being a class ab the pre and reverb circuits are the same. Any suggestions could only help.Also the mid control has very little response range on the lead channel, and ideas with both these problem would be greatly helpful. Thanks

[Gtr_tech]

I have the 3112 and yea, the reverb is pretty useless. I've thought about using an LM386 chip pwr amp to drive the pan input, but the pan would need to be replaced with one that has a lower input Z. Thats essentially the same idea as a stand alone Fender reverb unit where the pan is driven by a 6V6/output transformer. I'm not that big on reverb anymore so it hasn't been a huge priority. If/when I get around to doing the mod I'll post about it here.

[mjojo]

Thanks, I was more on the line of wondering about a couple resistor value changes in the circuit at this point but if you come across a solution please let me know and thanks alot.

[Gtr_tech]

Its just a low rent way of driving a rev tank as it sits. There are really much better ways to go about it. Using both sections of a dual op amp paralelled for starters would be much better.

[mjojo]

Thanks gtr tech, thats more involved than its worth to me. I have digital reverbs to use but it would be nice to have the amp have a better stand alone reverb of its own.It sounds fine if it wasn't so in the back ground. What the hell are these designers thinking of.I think i'll put my attention on getting a better mid response swing from the lead channel. I removed to caps when i first got the amp because there was way to much treble happening in both channels.Now if i can work out the mid thing this thing will be the perfect amp for me. I can't find any mods for this amp any where on the net so I guess I'm on my own. Thanks for your input though.

[Gtr_tech]

Here's what I did to mine (and basically every MV type amp I own):

Cut and paste from alt.guitar.amps

> Second request for your mods.

> All I've done was pull out the preamp tubes and put in some NOS 12AY7. It
> sounds a lot better.



Alright kids....now follow along.....
http://www.schematicheaven.com/newam...112_preamp.pdf

Start by removing the jumper in line with pin 7 of V1 and add a 68k
grid stopper. Remove C2 (.047u) and replace with .022u. Remove C41.
Thats it for the clean side.


Replace R67 (1M) with 68k, Jumper the end that connects to C41 to the
input jack tip (high side of R1). So far we've seperated the 2
channels, but driving both input stages simultaneously through their
own grid stoppers.


Next remove R59 (1M). It won't be needed since the dirty channel's
input stage is referenced to R1 so the grid won't want to float.


Remove C1 (.0022) and replace R11 (220k) with 100k at least half watt,
1 watt preferred. The cathode components for stage 1 are already where
they should be, but I'd recommend replacing the .68 tantalum with a
mylar or similar...I don't trust the tants as they have a tendency to
short.


Leave C10 alone (.01u).
Remove R6 (1M) and replace with 1000p/.001u cap. Low V is fine. I'm
not picky about type here 'cause its just shunting highs to gnd....no
need for spendy gourmet types.
R68 (470k) and C55(470p) are where they should be...leave 'em. Good
idea to replace the 470p with a better type tho since its in the
signal path.


Now normally I'll use a 1M pot bypassed with a good quality .001u cap
for the "gain" control, but I didn't have any miniature pcb mt 1 megs
on hand (just ordered more) so for now I left the 250k in there (but
forgot to bypass it so it loses highs when rolled down). It sounds ok
that way, season to taste. I'll change this one to 1M eventually.


Remove R15 and C12. Remove C11(470p) and replace with .01u. Remove
R16, replace with wire jumper. Remove R66(47k) and replace with 470p.
Remoce C13(.022) and replace with 470k/470p in parallel. Leave
R69(470k).


Now for stage 2s cathode circuit. remove R14(4.7k) and replace with
2.7k. Also in parallel with that 2.7k install a .68 cap and 1k
resistor in series so that the cap goes to gnd. I did this on the
solder side of the pcb.


Thats it for the pre circuitry...unless I've forgotten something
The stage 3 cathode components I left as is. An unbypassed 820 here
will do and thats what I'll normally use, but I didn't see it making a
big difference. I left the 250k "level" control....but I'll use a 1M
here too.


Now all thats left is to get the voltages in the front end a little
higher. The run about 240-250 as they had it. This circuit wants to
see closer to 300 to operate as intended.
Find R22(4.7k 2w) and replace with 1k 2w.


Ref supply/output/PI section:
http://www.schematicheaven.com/newam...112_preamp.pdf


Find R32 and R31(both 4.7k 2w) and replace them both with 1k 2w. That
should get you close enough for rock 'n' roll to 300v....mine measured
around 292v at the high side of the first stage plate load resistor.


Thats about it....yer done.
I *highly* recommend using .001 bypass caps on your gtr's vol pots.
This pre circuit is very touch sensitive and with just a bridge
humbucker there's a good range of tones and responses across the range
of the vol knob. Same with a neck single....it really cleans up nice
with the vol rolled down with "vintage" output singles.


Lastly....I'd recommend using an EQ pedal in the loop. Even with the
highs rolled full down and the mids about halfway, there's still some
brightness that some may not like. With an EQ in the loop you can cut
the extreme high end down to get rid of unwanted fizz while bumping up
some mids for a more meaty tone.


If anyone actually performs this mod, lemme know what you think of it.
If it proves popular (it already is in my area as I've put this pre in
a lot of JCM800s, Laneys, plexi RIs, etc and they all love it) I may
concider offering a kit with all needed parts and instructions. Not a
bad idea....I need to make notes for each model amp this goes into in
the future.


<enters Craig Fergusen mode> Take THAT Torres!

[mjojo]

After i get my jaw off the floor I'll try to comprehend what this all means. I'm not sure where this will take me sound wise because the only issue i have is the mid range on the dirty channel. This is to risky for me to attempt all these changes at this time when the only other amp i have to play out with is a ss peavey which i leave in my trunk for a backup.Thanks for your info I'll have to think this one over.

[Gtr_tech]

Well what it does sonically is tightens up the response of the OD channel. Its much more focused and well mannered post-mod....and less noise too since now theres only 3 stages in the OD side. If all you want is more mids then the best way to go about that is to use an EQ pedal in the loop....but there's that bizarro T/R/S jack for the loop so you'll have to make cabling to deal with that. THe schemo details what's what on that jack. Any attempt to do it passively will likely bring up high end along with the mids unless you design a L/C filter network. See the drawing for an Ampeg V-2 for an example of an inductor based mid control.

[mjojo]

Thanks, I have more than enough info at this point.This amp is almost perfect already with the effect processor modeler i'm using and the two cap removals. If i needed to do all the changes listed i would just get something else instead. At this point I'll just mess with the lead tone stack here and there when I have nothing better to do.Thanks alot

[Gtr_tech]

If you're using some modelling thing in front of it, why are you worried about what the amp sounds like? You'd be hearing the sound of the effects device way more than the amp. Just max out the tone stack and use the EQ on the effect thing.

[mjojo]

I use it both ways and even with the pedals the amp still matters in how they sound to me.

[Gtr_tech]

Typo alert.....I just caught this archiving the mod instructions for when the kits are ready to go.

Leave C10 alone (.01u).
Remove R6 (1M) and replace with 1000p/.001u cap. Low V is fine. I'm
not picky about type here 'cause its just shunting highs to gnd....no
need for spendy gourmet types.
R68 (470k) and C55(470p) are where they should be...leave 'em. Good
idea to replace the 470p with a better type tho since its in the
signal path.

"R6" should be "R76". R6 is the plate load for stage 2 in the clean channel....wouldn't work very well with a cap in its place.

[clintonb]

Here's what I did to mine (and basically every MV type amp I own):
<bunch of mod instructions>

I just saw this post (months after the fact) while searching for Crate mods. I was looking to "defizz" the distortion channel on my Crate Vintage Club 50 2x12 combo. I also wanted to increase the mids and lower the gain so I could turn the level control up higher to fatten up the tone. So I really appreciate your posting.

I recently bought a rack setup (Randall RM4 modular preamp, Peavey Classic 60 power amp, Randall SL+ and JTM modules) that cost me about three times as much as the Crate, even though I bought most of the stuff used. In most respects I like the Crate better, in other respects I like the Randall setup better. So I'm not totally happy with either setup. They both need some modifications. But after reading your post, I'm thinking I would be better off if I sold the Randall gear and modified the Crate instead.

It appears that you just take some stock master volume amp and change/remove/add components until it matches your preamp design.

Is there a stock preamp design out there that sounds similar to yours?

I'm curious why you do this mod to all your master volume amps, wouldn't you just end up with a bunch of amps that sound the same?

Remove C1 (.0022) and replace R11 (220k) with 100k at least half watt,
1 watt preferred.

Lastly....I'd recommend using an EQ pedal in the loop. Even with the
highs rolled full down and the mids about halfway, there's still some
brightness that some may not like. With an EQ in the loop you can cut
the extreme high end down to get rid of unwanted fizz while bumping up
some mids for a more meaty tone.

Based on the quote below from a thread at AX84.com (http://www.ax84.com/bbs/index.php?id=334866), wouldn't keeping C1 help with unwanted fizz?

Small value caps placed across the preamp tube plate resistors will tame the fuzz tone, just make sure the cap is rated for more than the plate voltage seen at the tube stage you are trying the mod out on.
This mod can be applyed to one or more stages.
Its best to get the fuzz out before the PI.

[walkman]

Ok, I know this thread is way old , however I followed these mods on my crate several years ago, along with 2x VHT Chromebacks (as I got it used for $150 without speakers).
Sounds pretty good to me. Also I disconnected the bright cap on the clean channel. IMHO theses speakers suit the amp quite well as it is now.They are not overly mid focused and have enough brightness without being harsh and I feel this is a good balance as the amp is not overly bright with these mods.

The amp had been used regularly in a touring band and had been previously modded with a bucking transformer to lower the input voltage perhaps to make it more reliable or put less wear on the el84s (see https://sound-au.com/articles/buck-xfmr.htm ). So this would make the amp as it is now quite different to stock sounding.