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Old 06-19-2012, 12:35 PM   #1
Jimi Sellars
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Crate VC 508

I saw one of these at a rummage sale about 5 years ago and was going to go back later in the day and see what I could get it for. When I went back it had been kicked to the curb in the take me for free section. I took it home and played it a little and in spite of the fact that it was tube and made in the USA it did not sound all that hot.

Now I am wondering if the Mods I have read about are worth the time and money. Not so much the money but how good can this thing end up sounding.
I like the small faces, faces type guitar tone and have a 52 Tele reissue and a Les Paul Custom. I am mainly an acoustic player but have had these electrics for years and love playing them.

Would somebody like to Mod it for me> Which mod is the best?

Thanks
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Old 06-19-2012, 02:21 PM   #2
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Which mods are you looking at?

I just skimmed the schematic and I would completely bypass the first two gain stages. They are solid state and would remove touch responsiveness. The drawback of this would be that you would have a much lower gain amp (think Fender Champ). You could make this sound almost like an orange (slightly less gain since there is no phase inverter).

Definitely worth the time to consider what you want out of your amp, but it is up to you whether you want to spend the money and time. Also, be extremely careful. The schematic I have shows that there aren't any bleeder resistors which means the high voltage is gonna stick around. If you decide to do anything inside, properly drain the caps (if you don't know how, ask).
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Old 06-19-2012, 03:30 PM   #3
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Thanks
I repaired appliances for 30 years and have seen people almost killed by microwaves. I like the "if you don't know ask" comment

I would not mind the low gain and like the orange comparison. Which mod would that be. I could either do it or have it done depending how buy I am.

Where can I get that Mod

When I plug the guitar in into the line out and pull the 1/4 inch input up to the first position it sounds better but I have to gain control.

Thanks again
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Old 06-19-2012, 03:55 PM   #4
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It's not a off the shelf mod (if there really is such a thing). It would involve bypassing certain parts of the amp and then changing some components as well as moving the gain control. As far as where you can get the mod, it's not a buy something and plug it in process.

I'm trying to find a clean schematic, but I am not having much luck. I've emailed Crate for a schem. That way I can give you more specific information on what it will take to get this working like a real tube amp.


I asked before, but you didn't answer. What specific mods have you been looking at?
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Old 06-19-2012, 08:59 PM   #5
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So far I have only seen the one on http://www.guitarnuts.com/amps/vc508/index.php The way that it is written however is hard to follow and is not step by step but a blog type.
I would love to be able to use the amp as it is a nice size and made in the USA.
The tone now is just to harsh.

Are there other popular mods that you would recommend?

Thanks
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Old 06-20-2012, 06:47 PM   #6
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Alrighty, Jimi. Thanks for the help in getting a proper schematic.

The mods detailed in your link are not how I would go about modifying this amp. I'd remove C6 to isolate the solid state side of the amp from the tube side. I would then put in a regular Cliff Jack (instead of a PC-mounted jack) and run the input at the junction of R7 and R8.

To make this more Orange-ish, replace R9 and R14 to 220k.

Change the "volume" control from 10k to 1M (audio taper) and remove R21. This is now your gain control.

Replace R16 with a 1M (audio taper) pot and cut the trace going to pin 2 of the EL84. The center lug of the pot will be going to pin 2. This is your volume control.

Remove C9 if you think the amp is too bright.


Before you do any of these, drain the capacitors. One way to do this is to put a jumper between pin 1 and pin 2 of the preamp tube. You'll want to wear insulating gloves when doing this as pin 1 will be at 172v.
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Old 12-28-2013, 02:18 PM   #7
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end citizen, I finally got around to it and while this is a very old post I wanted to thank you. I use it in the living room while I get an idea or let some of my guitar students use it.

It did not work at first but I found a bad solder connection I did.

It is very low output but sounds very satisfying. Thanks Again
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Old 02-02-2014, 12:54 AM   #8
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Hi All,

I just picked up one of these amps off kijiji. I finally got around to performing the mods above, thanks End Citizen.

There are a couple new quirks that I'm willing to live with (mainly arising when the combination of gain & volume is too high).

The main new issue is that I have some serious 60Hz buzz. It seems to be caused by the effects loop jack. If I place my finger(s) near the jack, the buzz decreases significantly.

I'm thinking this may be due to the removal of R21?

Is there any way to remedy this? I'm willing to completely remove the jack if necessary.

Thanks,

mngnt
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