Crate V18: Mods and Conversions

Discussion in 'Amps and Cabs' started by steeve_a, Nov 15, 2008.


  1. Feral Tone

    Feral Tone Member

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    We were talking a few days ago about bypassing the reverb and using the + and - 14.7 volt taps to power an onboard FX pedal or a 9 VDC line out. As Steve mentioned, you'd need a voltage regulator to stabilize and lower the voltage, and I came across this handy little site when I was looking at maybe lowering the 14.7 taps to 9v:
    http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/zenereg.html

    If you don't want to do that, Ted Weber sells an onboard FX power supply kit that looks really sweet https://taweber.powweb.com/store/modkits.htm#eps
    (it's the Pedal Pump Effects Power Supply kit). This actually includes a separate transformer that will give you a bunch of 11 and 9 volt AC taps plus 4 identical small circuits that will rectify and regulate down to 9 volts at 300ma each. 500 ma would be more ideal to run some major power suckers (like delays, etc), but 300ma should work for most anything nonetheless.

    You can probably even just modify Weber's little Pedal Pump circuit board to remove the rectifier and beef up the regulator to use with your 14.7 volt taps.

    Lots of options here.
     
  2. steeve_a

    steeve_a Member

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    I am totally ignorant about switching power supplies but I assume that you did look at the schematic on my site:

    http://www.blueguitar.org/new/schem/misc_amp/crate_v18_power_supply.pdf

    I wish I could be more help with the projects you have in mind but that is really above my head.

    I try to pick battles that I have some chance of winning! ;) You could add a single preamp tube for a tube buffered effects loop and then run a tube driven reverb/tremelo unit in the loop. I suspect that the V18 board already contains the necessary circuits for a solid state buffered loop if you wanted to go that route.

    The double-sided printed circuit board of the V18 is not well-suited for the mods you suggest. With the back of the board being mainly one large ground plane it is not an easy matter to add any connections not in the original architecture.

    But keep us posted on what you come up with.

    Good luck!

    Steve Ahola
     
    Last edited: Nov 24, 2008
  3. steeve_a

    steeve_a Member

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    Last edited: Nov 23, 2008
  4. Feral Tone

    Feral Tone Member

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    Sorry to be a pest, but does anyone have the all the plate voltage readings? I recorded them before I started modding, and now I can't find the piece of paper where I wrote it. I just want to make sure I'm not dropping voltage after my mods. Thanks.
     
  5. steeve_a

    steeve_a Member

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    Here were the plate and cathode voltages I measured after doing the Clean Channel mod:

    V1a 183 / 1.54
    V1b not used (I bypassed stage for Clean Channel mod)
    V2a 242 / 3.75
    V2b 192 / 1.60


    V3 plates 208 / 195 [LTP]
    V3 cathodes 45.2 / 45.2
    V3 grids 26.5 / 29.6

    V4 & 5 plates 324
    V4 & 5 screens 321
    V4 G3 10.6

    I think I have the voltages of the stock amp written down somewhere....

    Steve Ahola
     
  6. Feral Tone

    Feral Tone Member

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    Thank you!
     
  7. steeve_a

    steeve_a Member

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    Here is what the Rocket Conversion sounds like:

    http://www.box.net/shared/static/5khsx8zoyv.mp3

    I used a few settings on the front panel but mainly dialed in different sounds using the volume and tone control on my guitar (a PRS SE Singlecut II).

    There were a few items left to do when I recorded that:
    -replace 330pF treble cap with 50pF cap [EDIT final value 100pF mica cap]
    -replace 0.01uF PI coupling caps with 0.047uF caps
    -replace 250kA treble and bass pots with 1MA [EDIT added 510k resistor across 1M bass pot@]
    -replace 1MA gain pot with 500kA
    -power supply resistors: replace R52 w/ 15k and R53 w/ 2k2

    I just did all of that and the amp has a lot more chime at low volume settings, and seems to be even more responsive to the settings of volume and tone controls on the guitar. I will post some sound samples of the completed conversion later today.

    Alas, the MJ Conversion is no more, having laid down its life so that the Rocket Conversion might be born. (I thought that it was just too muddy for my tastes.) R.I.P.

    Steve Ahola

    @ That was a mistake! I had planned to tack a 1M resistor across the outer terminals of the pot (on the back side of the board) but got mixed up and used a 510k resistor instead. Which would bring the effective resistance of the pot down to ~340k (and not 500k as originally planned). But I *really* like the way the amp sounds now so I will probably leave it in there.

    I also just changed out the OT with a New Sensor Deluxe OT that Hogy at Komet had recommended over at AMPAGE back in 1999 (yes, I save tips!) I had tried this out in the first V18 I modded (the Clean Channel mod) and thought that the stock OT sounded better. But for this application I really like the smaller Deluxe OT. And I also added a conjunctive filter to the 1/4" terminals- this with a 10k 5 watt resistor and a 2200pf 1kv ceramic cap. Very sweet sounds at lower volumes but it gets nice and nasty when you crank it up! I'm going to draw up the mods right now... 11/29/08
     
    Last edited: Nov 29, 2008
  8. JPenn

    JPenn Member

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    That sounds pretty killer! I've got one of the 112's comin to use on a new low volume gig I've got. I think I'll have to grab another one and have it modded like this.
     
  9. steeve_a

    steeve_a Member

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    Color-coded and annotated layout drawing for Paint By Numbers modders...

    http://www.blueguitar.org/new/schem/misc_mod/crate_v18_trainwreck_rocket_conversion.jpg


    Rough draft of preamp schematic...

    http://www.blueguitar.org/new/schem/misc_mod/crate_v18_trainwreck_rocket_conversion-schem_preamp.jpg

    Rough draft of power amp schematic...

    http://www.blueguitar.org/new/schem...inwreck_rocket_conversion-schem_power_amp.jpg


    This amp is sounding really good to me- I hope to add some fresh sound samples tomorrow.

    Steve Ahola

    P.S. For the tone stack I kinda split the difference between the Rocket, the Express and the Liverpool to come up with something that would work with the printed circuit board and get some good sounds. There is a trace that you can cut under the mid pot which connects the mid cap to the wiper (as mentioned in the Trainwreck Notz file). I'm not sure what difference it makes but when you have a Dremel tool you are always looking for something to cut... ;)

    P.P.S. If you check on-line there are a few dealers who expect to get in the V18-112's on December 7th or 8th; I certainly hope that they will be blowing them out for $149. (I just got emails from some of the other dealers- you can preorder them but they are $329... Thanks but no thanks!!! I *know* that there are going to be plenty of them being dumped by people not willing to do mods... we just need to wait them out!)

    P.P.P.S. For the pots highlighted in red, sometimes you can swap them around to get what is needed, but most of the time I need to replace some of the pots. I've been buying the Philmore 16mm PC mount pots at Fry's Electronics for $1.99 each and then adapting the shaft for the Crates: continue the flat all of the way up the shaft with a file and then cut the shaft to length. The number for the 1M audio pot is PC88; the 500k audio pot is PC87. Once the shaft has been converted they are drop in replacements. Alternately, you could contact Crate parts department; I suspect that the 1M V33 Clean channel volume pot has a better taper than the generic pots that I have been buying.
     
    Last edited: Nov 30, 2008
  10. steeve_a

    steeve_a Member

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    Here are some lower gain and medium gain sound samples of the final version of my V18 Trainwreck Rocket conversion...

    Low gain:

    http://www.box.net/shared/static/jayhfbejk5.mp3


    Low gain (more):

    http://www.box.net/shared/static/n9ypuzrqda.mp3


    Medium gain:

    http://www.box.net/shared/static/28s7kieih4.mp3

    The neighbors came home and I didn't feel like blasting them out with any higher gain sounds right now... this amp can get loud! But I'll upload some higher gain samples later.

    Here are the settings:

    Gain 4.5
    Volume 12 (of course- this is a Wreck!)
    Treble 5
    Mid 6
    Bass 4
    Reverb 3

    I started out with the Gain at 4 and was using the volume control on the guitar a lot (I just left the guitar tone at 10).

    I'll be taking this amp out for a spin Sunday and Tuesday nights so I might post some live band recordings using it (that is the real test of these amp mods- how well it works live with a band).

    Steve Ahola

    P.S. Here was my solo from "It's A Man's World" Sunday night- kinda winging it because I usually don't get to play a solo on this number but I sure like the way the amp sounded and responded to nuances! Settings as listed above with the Gain around 5.5. I would have liked to crank it up a little bit more but this is a small bar and they don't want it much louder than this. :(

    http://www.box.net/shared/static/kda7hjarde.mp3

    .
     
    Last edited: Dec 1, 2008
  11. steeve_a

    steeve_a Member

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    Someone had mentioned getting good results undoping the stock Crate speaker with acetone. Has anyone here had any success with that? I was wondering if you just undope the surround, or do you do the entire cone?

    I guess you use paper towels to soak up the doping compound that is loosened up by the acetone...

    Steve Ahola

    EDIT I have done this to two Crate speakers so far but haven't tried them out yet. I mainly worked on the doping on the surround, going over it with an acid brush dipped in acetone and then soaking it up with paper towels. I've done some undoping of the cone itself but there is no way you can all of that crap off. I figure if I can loosen up the cone a bit the speaker would be more responsive...
     
    Last edited: Dec 14, 2008
  12. scihibmxer@juno

    scihibmxer@juno Member

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    I just brought home an excessively doped v18 12 removed by my brother to try the variac exercise. I am a chemist, so when you asked if acetone would remove the dope, I gave it a try. If I knew what they used for a dope, I could probably tell you the best solvent (maybe methylene chloride would be better and it is not flammable). But acetone did remove some of the excess. The cone and surround are now dull in color. However, the paper cone in likely porous enough that it retains a fair amount of dope. This could help the speaker some, with added exercising. But the cone will never be the same as a totally untreated cone. My V18 has been pretty well modded since this speaker was in it, and it has a Carvin Brit 100 in it now, so it might be hard to judge the before and after effects. I have a couple other crates on there way, so I will try to compare a brand new speaker to this one with excess dope removed and serious exercising. I won't have results until around Christmas. Just remember acetone is extremely volatile, and the vapors are explosive, only use in well ventilated area free from ignition source.
     
  13. steeve_a

    steeve_a Member

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    "Volatile"...? Let me look up that word in the dictionary. Can you turn on the light? That's okay, I can just light the candle right here on the table... KABOOOOM-M-M!:crazyguy

    Thanks for your post! For these speakers I don't think that they would ever be the same as an undoped speaker, but if we could loosen them up a bit with solvents and a variac it might make them half-way decent. BTW instead of a variac a low voltage AC transformer could be used but it is important to refer to Ohm's law to determine what voltage to use and whether you need to add a dropping resistor.@@@ HVAC transformers are typically 24 volts and door bell transformers are typically 16 volts- both of them are available at many hardware stores. If the 24 volt HVAC transformer has multiple input taps you can get 6v, 12v and 24v on the secondary with 120vac on the primary.

    Speaking of speakers, I believe that the V50-112 comes with the same speaker that is in the V18-112, and with the heavy doping I don't think that it can handle the 50 watts that the voice coil is rated for. Some people have suspected that speaker problems have contributed to the V50 breaking down when played at full volume. Crate uses TWO of these speakers in the V33-212 but only ONE in the V50-112. Go figure! :barf

    I would definitely put a heftier speaker in a V50-112

    Steve Ahola

    P.S. So what was Crate thinking when they had the entire cones doped??? Are there any other companies that are doing that? When you order speakers from WeberVST you can have them heavily doped, but that is just the surround, not the entire cone...

    @@@ Power in watts equals the voltage squared divided by the resistance. Perhaps we can get someone here to doublecheck my math but I think that means that 12 volts going into an 8 ohm load will run about 18 watts (and 24 volts into an 8 ohm load will run about 72 watts). For a 16 volt doorbell transformer going into an 8 ohm load that would run about 32 watts. (Since we are dealing with an impedance and not a fixed resistance the actual wattage would vary from those figures but it should put you in the right ballpark.)
     
    Last edited: Dec 2, 2008
  14. sak

    sak Member

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    Nov 20, 2008
    Hey Steve, awesome work you've been doing. Quick question - do you have a mod-by-colors chart of the clean channel conversion? And have you got any sound samples of that conversion?
     
  15. scihibmxer@juno

    scihibmxer@juno Member

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    a quote from a 30+ year bar musician, rockmumbles

    "it's "beer proof" doesn't every aspiring musician need "beer proof" speakers..."

    I picked up a v50-112 and assumed the catastrophic failure reported in some of the reviews was caused by the weak speaker. For this amp we will likely put in an "american" voiced speaker, like the Eminence r,w,b you have used.
     
  16. steeve_a

    steeve_a Member

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    Thanks for the kind words! All of the Conversion drawings can be found in this folder:

    http://www.blueguitar.org/new/schem/misc_mod/

    Yikes! I guess I never got around to drawing up the Color-by-Number layout for the Clean Channel Conversion... I will get that drawn up maybe tomorrow.

    Here's a live sample of the amp- my solo from "Five Long Years" a few weeks ago:

    http://www.box.net/shared/static/qjypum3i6m.mp3

    And here's a sample from an earlier incarnation of the amp at home:

    http://www.box.net/shared/static/0u4foiuk09.mp3

    I'm not done fine-tuning this amp. I would like it to grind a bit more when I turn up the gain all of the way. I think I might try putting the stock values back for R10 and C3- but with a 500pF mica cap. There is not a lot of signal passing through R10/C3 with the Clean Channel values of 2M2 and 50pF...

    I may try replacing the V1A plate resistor with 220k to emulate the Soldano front end- and maybe even try 0.002uF for C3 from that design. I really like how the Soldano Conversion cleans up as you turn back the controls on your guitar- a lot of designs do that but not quite like the SLO...

    EDIT I just played this amp for the first time in a few weeks and I'd scratch the two preceeding paragraphs. I would just like to cut the bass a little bit more and maybe try adding a conjunctive filter to the primary of the OT (as I did with the Rocket Conversion). For fine-tuning tone stacks I highly recommend Duncan's Tone Stack Calculator:

    http://www.duncanamps.com/tsc/

    Plug in different values and settings, and you can see how it changes the frequency response curve. It sure beats repeated the soldering and desoldering of different components just to see how it sounds!


    Steve Ahola
     
    Last edited: Dec 2, 2008
  17. rock_mumbles

    rock_mumbles Member

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    Steve, just wanted to thank you for all the work that you share with us!!!

    Previously I had done some tube swapping on my brother's V18-112, I pulled out all three Sovtek 12AX7's (V1 tested bad) so I put a JJ ECC832 (their 12dw7) in for V1, a balanced old used US made 12AX7 for V2, and I don't remember what I put in for V3 either an old used 12AX7 or 12AT7. The tube swapping helped reduce the gain and get some clean headroom, but it was still muddy as all get out. I put in an old Carvin BR12 100W speaker instead of the plastic coated speaker hoping to change the sound but it had little affect on the tone.

    Yesterday I took the soldering iron to my brother's v18, I was lazy and didn't want to remove the circuit board so I cut out R6 and C10 to simplify the signal path around V1. I followed Steve's advice and left R10 alone and paralleled R4 (2.2M) with a 470K to get about 390K for R4 (similar to a Valve Junior mod I did). There was a noticeable loss in gain and a slightly cleaner sound, but still not enough. I paralleled R5 (2.7K) with a 3.9K to get a 1.6K cathode resistor (again similar to a Valve Junior mod I did) .

    Then I unscrewed the circuit board (leaving most of the wires attached) and replaced R18 the tone slope resistor with a 100K and did the quick and dirty 33K resistor across the white reverb jack. I played it and it "worked" like it should, it is now a better amp than my modded Valve Juniors.

    I went to the club we played at Sat. night to pick up gear and I had our guitar player test it out, <big smile> "it's like a brand new amp, I can't believe it, now all 5 positions on my strat sound different just like they should."
    I'm thinking about the looking into your tw Rocket conversion and calling it a "Crocket"

    Thanks again Steve!
     
  18. steeve_a

    steeve_a Member

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    I think that Walt Disney may have the rights to the name Crocket tied up tighter than a drum... :crazy

    There are a lot of things that you can do to the board without pulling it out (actually not that hard once you've done it a few times). Like clipping out resistors, or solder-tacking resistors or capacitors to the leads of an existing resistor.

    However I would recommend that you not try to replace a component from the top without removing the board first simply because the solder on the bottom of the board might end up somewhere that it is not supposed to be- and there is no way to visually inspect that from the top. (That is a moot point for most of the capacitors since you can only desolder them from the back side of the board anyway.)

    I'm sure that everyone here has already figured this out but to test out different tubes, etc., the easiest way to do it is to put the back on the chassis with two screws and set it on top of the cabinet upside down. Now you can swap out tubes without having to remove the chassis from the cabinet...

    Steve Ahola
     
  19. wagdog

    wagdog Member

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    Greetings Steve,

    First post here, I usually hang out over at HC.

    I'm intrigued by your Soldano mods. Clips sound very nice. I modded a v33h quite a bit with good results, and just yesterday got a v18 2x12, which I modded a bit (r4/r10 swap, 100k slope resistor and a 4.7uF bypass cap on r5, and some tube swapping).

    I'm pretty happy with the results, but I pretty much got this amp to fiddle with, so...

    Did you do the mods just as specified in your first post on this thread? Where there any gotchas or things that required tweaking along the way?

    Thanks!

    Wag
     
  20. steeve_a

    steeve_a Member

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    Funny thing is that this conversion required no tweaking or fine-tuning: it worked perfectly right out of the gate! So much so that I wonder if Crate kinda borrowed the architecture from the basic SLO OD channel, but without the tube driven FX loop and with slightly different resistor values... Nah! They certainly would not have done that without licensing the technology from Mike Soldano. :cool:

    In any case, at this time I still haven't replaced the Gain and Volume pots, and I forgot to bypass the RC network on the "tail" of the tone stack- my bad! I hope to be doing that tomorrow, to see if it helps or hurts the sound and response I am getting right now, which is pretty amazing!

    Steve Ahola

    P.S. The idea of tweaking the Crate design by changing one or two parts here and there (and then like a shampoo, rinse and repeat) does not appeal to me: there are so many possibilities I wouldn't really know where to start! So I'd rather just steal a design which is known to work well and then try to tweak and fine-tune *that*... much more rewarding! ;)

    I'm still deciding what to do with my V33 head! A Marshall Plexi/JCM800 design should fit in fine with the channel switching architecture...
     

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