Crate XLP preamp schematic?

[Joseph Goodman]

I've recently acquired this preamp from the early 90's, and while I don't intend to do much to it beyond cleaning the contacts, I'm curious to see the schematic, if for no other reason than to confirm or debunk the claim that it's the preamp section of the GX-130c. I did request one from Loud, but they only sent me the manual. Thanks in advance!

[Jazz P Bass]

Crate GX130C Schematic

Well if Loud doesn't have it.....
Here is the GX-130C.
Let us know if it is the same.

[DrGonz78]

I read a lot about the GX130c and VH140c having many similarities but not exactly the same preamp. Maybe compare the XLP to the VH140c schematic to see what you get there too.

[teemuk]

I read a lot about the GX130c and VH140c having many similarities but not exactly the same preamp.

...And before that the usual claim was that their preamps were identical.

The "similarities" -thing applies to virtually all solid-state (and hybrid) medium to high-ish power Crate amps made since invention of the FlexWave distortion in early 1990's. (This applies especially to amps with clean+rhythm/lead channels). Before FlexWave distortion the preamps were also quite similar to another but the FlexWave circuit largely meant a total revision of the amp models and since then they pretty much followed the new concept of design.

With that in mind, almost all of the aforementioned Crate amps share a similar circuit architecture what comes to overall (gain or EQ) stage setup, distortion circuits, tonestacks, etc. but the overall voicing is likely somewhat different from one amp to another, otherwise there wouldn't be much sense to make more than a single amp. Anyways, most of them are reasonably "close enough" that one can extract comparable sounds from them after a bit of tweaking with the dials.

BUT there's nothing strikingly astounding in this. For example, basically almost all solid-state Fender amps have as well been very, very similar to another ever since mid 1980's. Conceptually large parts of preamp architecture in, say, Fender Metalhead are still quite similar to, say, few decades older Fender Pro 85...or something. Heck, even several Asian OEM vendors downright clone the generic SS Fender preamp design with minor modifications. (For example, I'm currently looking at schematic of RG200's preamp section - it's an amp made by Smarvo for U.S. Music / Randall - and the preamp architecture all the way down to circuits and most component values is basically similar to that one could expect to find from a SS Fender amp. That said, likewise many other preamp (and power amp) designs that come from same manufacturer (like Peavey, Vox, Marshall, and so on) are usually very similar to another - at least with every new design concept. e.g. Peavey preamps with "Saturation" circuit were very, very similar to another, Peavey preamps with "Super Saturation" were again very, very similar to another and now the TransTube preamps are once again very, very similar to another. The preamps of Vox VR-series are largely the same as they are in the solid-state AC series and the design concept is similar to that tiny "Brian May" amp made a few years earlier. Identical? Not often.

Most people drawing up the "they have identical preamps" -card are incorrect and just parrot what they have read instead of basing that statement on actual research and knowledge. e.g. the common claim of Ampeg VH-140C and Crate GX-130C having identical preamps is easy to verify to be untrue, and while doing that one can clearly also observe how much common the preamps (as well as power amps) actually do have. There's plenty. They come from same design tables and often there's just no need to reinvent the wheel or change things that work. The same kind similarity applies to about all solid-state Crates (and Ampegs of same nature) while totally identical designs are much rarer finds (although not impossible).

[Joseph Goodman]

Thanks for the input, guys; at least now some of these similar-but-in-no-way-identical amp schematics are here, all in one spot. Back to the subject of the XLP, I sent Loud another request for the schematic, and they sent me one, without even extracting a promise from me not to re-distribute it. From the looks of it, the XLP rackmount preamp is, in fact, the preamp section of the G130CXL/GX130C amplifier.

[Joseph Goodman]

Bumping this old thread to add the parts list and assembly sheets of the XLP