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Crate schematic

Started by metalhead, March 19, 2008, 03:50:04 AM

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In need of Crate schematic. Any amp with Flexwave (preferably Flexwave 5) circuitry.GTX VTX or equivalent. GT 3500 schematic would be nice.
Has anybody got any information about how the Flexwave circuits have evolved through different versions.Timeline of changes would be usefull.
Any mod suggestions? Shoddy workmanship,low quality parts,not enough solder in printed circuit traces, what else could be improved? :loco


Teemuk! Do you have CRATE schematics? :loco


I've not seen any on the net. When I last looked for one, Crate wants you to buy it from them.


I have some Crate / Ampeg schematics from the "mid-era of SLM" (ca. 90's) but I don't have any schematics for these new LOUD technologies -era amps (such as GT3500), and I have only few very old ones from the dawn of SLM. The latter can still be found online. SLM stuff is not online anymore - it hasn't been for years - and SLM is now a division of LOUD Technologies that seems to handle things differently anyway.

Edit: Just checked out my database... To be more specific, the Crate schemas are for second revision of GX and GFX series of amps and few for stuff such as "Taxi" series. Ampeg schemas were mostly for the SS stuff from the same era (e.g. SVT Pro line up and few other bass amps).

Apparently LOUD has only about 60% of the old SLM-era schemas so their support for old stuff is quite poor.


Teemu, do ya have Crate GX-15 schematic? (15w SS amp)


Yes. I even have the amp! (or actually it is the GX-15R version with reverb). ;D


Do you have any of the tube/mosfet amp schems?


Any info which models use the zener diode configuration and which models use the "actively controlled "rubber diode" configuration. :-\


Do note that my schematics cover only a very small percent of Crate products. In those which I have the lower power GX/GFX models (50W or lower) tend to use only Zener diode-based clipping. They all have two clipping stages with back-to-back Zeners configured to provide asymmetric clipping. Both stages have the FlexWave circuit.

Higher power GX/GFX models (from GX/GFX-65 and up) that have two OD channels (rhythm and lead) use the VBE-multiplier ("rubber diode") based clipping for lower gain sounds of the rhythm channel and add a Zener diode based clipper/extra gain stage before it when the lead channel is activated. In this case, the Zener diode stage usually has symmetric clipping and doesn't utilize the Flexwave circuit.

In all cases all clipping is introduced within two gain stages.

Exceptions naturally exist - even in such large numbers that it's hard to make any universal description. For example, GX-120 uses only Zener-based clipping in two gain stages and has two individual gain controls for the first gain stage. Note that there are also various versions of the models that have slightly different circuitry. For example, I don't know anything about the first revision of GX and GFX amps. Bass (BX), keyboard (KX) and tube amplifiers do not use FlexWave at all - at least not the ones I have schematics to. Taxi series has it in some models, e.g. TX-30 has FlexWave while TX-50 doesn't.

All this, of course, covers only the clipping / gain stage structure of the OD channel. Personally I regard the voicing taking place pre/post clipping as an equally important issue (if not even more important). Again the amps with two OD channels tend to be quite different in this respect than the "simpler" amplifiers.


This thread's been dormant for a while, but I guess it can't hurt to ask...

I picked up my old Crate GX-20M from my folks' attic over the weekend, after not even thinking about it for about a decade, and now I'm thinking that I'd like to know more about its guts, and possibly look into some modifications.  Teemu, from your post it sounds like this might be a model that falls in the range of schematics you mentioned; if you've got it in convenient electronic form and wouldn't mind sharing (or if anyone else does) I'd certainly appreciate it.


(Thank you, Teemu!  Much appreciated.  Now to try to find the time to study it...)


Do I read correctly that someone has Crate schematics? I need one for a GX-15. What's the procedure here?

OT (not Crate), does anyone here have a Realistic MPS-5 amplified speaker? I have only the front half (no battery compartment or DC-in jack) and need to know what voltage it takes.


I emailed the Crate schematic for you.


Hi guys, my GX-15 is making a weird noise like brrrrr brrrr when turn the clean level up and use some LOW eq, I thought it was the crappy speaker, a friend toast the original one and replaced with a cheap 4ohm one no data on Watts printed btw, today I buy a 8ohm speaker used mostly on HiFi but 100w uhmm I can't find a 4ohm 30W or a 8ohm 15W as the specs says... the brrr brrr is gone, but now the poor GX-15 sounds very low and the channels are oversaturated when go far from 6 on any level knob... Teemuk can you be kind and pass me the schematics on GX-15 and GX-15R or if you know a way to upgrade to a better GX to deal with the brand new speaker.

Thanks in advance and greetings to all.



You might should read teemuk's book.
He discusses some of the issues with "Hi-Fi" speakers for instrument amplifies.

In short, you need to find a good instrument speaker.

The cheap speaker you had my have damaged the circuit too.