Crate V18: Mods and Conversions

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


  1. steeve_a

    steeve_a Member

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    That snowplow sounds really nice! Last night I replaced R15 with a 120k resistor which brought the overall volume down to a decent level. So the stock value of 100k should work just fine. I was thinking of adding a Cut control to the unused pads for C32. That would be a 250k pot wired as a variable resistor in series with a .005uF cap. (It's like a tone control for the output section that can cut the trebles a bit.)

    Glad to hear that the conversion worked for you- 3 cheers for Mike Soldano and his SLO design! I am amazed that it works so well in the Crate V18... :dude

    Steve Ahola
     
  2. scihibmxer@juno

    scihibmxer@juno Member

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    Thanks for the help Steve. We "were" going to go with a Rocket style conversion on the second v18, which left the v33 (or v50) as a candidate for a Soldano conversion. I'm just not exactly sure how to best utilize the switching channels...

    Thanks again, Steve! Wagdog's clip:drool reinforces that your SLO conversion is a winner for the v18!!! We may just do it on the v18.
     
  3. steeve_a

    steeve_a Member

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    Here's a little trick I've been doing to some of my V18 amps- it is sometimes called a "conjunctive filter" and Dr Z uses them on a lot of his amps. It is wired up between the two OT primaries and will smooth out the response of the transformer. With there being 1/4" male terminals on the PCB for the two OT primaries and centertap it is ridiculously easy to add a conjunctive filter. For a pair of EL84's a good starting point is a 10k 5 watt resistor wired in series with a 2200pF 1kv ceramic cap. If you don't like that you can always go down to 1500 or 1800pF or up to 2700 or 3300pF. Here's a picture of what it looks like installed on the board:

    http://www.blueguitar.org/new/schem/misc_mod/crate_v18_c-filter_trick.jpg

    I use 1/4" terminal multipliers right on the 1/4" male terminals and mount the insulated terminals going to the OT on the middle terminals of the multiplier. I use hi-temp 1/4" female terminals on the resistor and capacitor leads but the important thing is to solder the connections (I do not trust crimp connections- especially in a guitar amp!)

    For more information about conjunctive filters here is a thread I saved from the old AMPAGE forums going back to 2001:

    http://www.blueguitar.org/new/text/c_filter.pdf

    As my uncle Isaac used to say "try it- you'll like it!" ;)

    Steve Ahola

    P.S. I considered doing an AC30/Trainwreck Rocket design in my V33, with V1b wired up as the added gain stage from a Marshall master volume 2204 amp- but I don't recall seeing anybody do that particular mod to an AC30-ish amp. Probably better to stick with the tried'n'true Plexi/2204 channel switching design.
     
    Last edited: Dec 14, 2008
  4. scihibmxer@juno

    scihibmxer@juno Member

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    Thanks for the tip, we will give it a try. Looks easy enough to make a number of resistor-cap values and test them by ear as Dr Z states. Saying they are like "zobel networks" for speaker crossovers puts the value of the circuit, and impact into context.
     
  5. wagdog

    wagdog Member

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    My snowplow is awesome; runs great in the fall when I pull it out to get ready for winter, then without hesitation it fails miserably when the snow starts flying.

    Anyway, I ended up going with 150k for R15. I also put the bright cap on a switch, which is really nice. With my strats it's off, but w/my les paul I turn it on and it sounds great. Made a new clip w/my 74 strat. I tried to be more methodical, same lick, starting from the bridge working back, clean, dirty, full-gain. The "dirty" section actually is dirtier then I intended though:

    http://www.wagner-usa.net/74strat-crate-soldano_mixdown02.mp3
     
  6. steeve_a

    steeve_a Member

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    That's good to know- I only tested my amp with humbuckers and hadn't gotten around to testing it with my strats and teles yet.

    So what tubes and speaker are you using? I just doped up a Weber I'd had around for a few years because the high gain amps were causing cone cry... it now sounds a lot like the Eminence Red, White and Blue so that saved me about $75. I've been using GT 5751M's for the first two preamp tubes and just stuck in a GT 7025 (EI, I believe) for the phase inverter. And I popped in some Mullard reissue EL84's...

    I just got back from my Sunday night gig and the Soldano was absolutely killer. I set the gain to about 7.5 and just worked the volume and tone controls on my PRS SE Singlecut all night- it really covered a lot of territory sonically. I used the Trainwreck Rocket two weeks ago and it just didn't cover as much ground- if you turned the guitar controls down too much it would reach the point where it was unusable (at least for me). With the Soldano, I was able to work with *all* of the settings on my guitar- from barely audible to "holy sh*t!"... :eek: I brought my Boosta Grande along thinking I may need to push the signal a little bit but did not even switch it on.

    To sum it up in two words: This amp cooks! ;)

    Steve Ahola

    P.S. I think that this amp might be even better for blues than a real Soldano SLO because it doesn't have the two DC-coupled pairs w/ cathode follower for the FX loop. There is a sound and responsiveness that I never noticed on studio and live recordings of SLO's...

    Here are some clips that I recorded tonight:

    http://www.box.net/shared/static/1ae9nid10s.mp3

    http://www.box.net/shared/static/b1nojlfz7y.mp3

    Now to start on the Trainwreck Liverpool 18 Conversion since I just picked up another V18 on eBay... do they have a 12 step program for people like me??? :crazyguy
     
    Last edited: Dec 16, 2008
  7. wagdog

    wagdog Member

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    FWIW, I've got an ax w/p90's and it absolutely burns with this amp.

    Stock speakers, which are pretty damn crappy, imo.

    v1-v3: JJ 12AX7/12AT7/12AU7 - stock EL34's in the power amp.

    I ran the amp through my 4x12 cab which has eminence legends in it and sounds sooooo much better. But this SLO mod w/the stock speakers has made them usable. I will replace the stock speakers at some point when I can afford it.

    I noticed this as well - the amp is very responsive to the guitars volume and tone controls now. Stock, and with my original mods it wasn't nearly as usable. It has a nice shimmer running clean with the strat 2/4 positions as well. That wasn't most definitely wasn't there before.

    I used the amp at my gig 2 days ago running in stereo with a hot rod deluxe. It was awesome. It was LOUD, too loud in fact and took some fiddling to get the stage volume balanced.

    It really does man, I love it. I'm actually working on doing the same mod for my v33 head.
     
  8. steeve_a

    steeve_a Member

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    If anybody actually *likes* those speakers I have a bridge for sale- very reasonable terms! :crazyguy

    You might try the trick with acetone- I picked up a can and have been using an acid brush to drench the surround with the stuff and then I soak it up with paper towels. I've used it on the cone itself, too, but I think that is a hopeless cause. :(

    I figure that if we can loosen up the speaker a bit it would be more responsive... I've treated two speakers with the acetone so far but haven't tested them yet. (I plan to do that tomorrow and will post my results.)

    RESULTS: It sounds pretty good- maybe a little bit like a greenback. Brighter than the Eminence Red, White and Blues so I turned the Cut control down a little bit more. (The Cut control is great for matching these amps to different speakers since adjusting the tone controls can change the response in the preamp.)

    Steve Ahola

    P.S. You probably want to wear some kind of gloves when handling the acetone- if the doping you remove gets on your fingers its a real bear ( :BITCH ) to get off!

    P.P.S. So you are using the 12AU7 for the phase inverter- or the 12AX7? I use the schematic designations but looking at the chassis they go from the right to the left- perhaps because the amp was made in China? :rotflmao
     
    Last edited: Dec 16, 2008
  9. scihibmxer@juno

    scihibmxer@juno Member

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    Hats off to you Steve!

    Rock Mumbles PM'd to say in 3 hours today he pulled out all the old mods and went with Steve's SLO conversion to the preamp (had to order the resistors for the power amp). Here are a few comments, impressions:
    "played the Soldano in a Crate box for about 20 minutes, really impressed, it can do almost anything as far as sound goes. It has really big bass but is well defined, really nice clear high end without hurting your ears, and a nice smooth overdrive, and it's loud with the master on 3. I still have the ECC832 in V1 and I think it's perfect there, there is still a lot of overdrive but turn down the guitar just slightly and it cleans right up. This amp has some of the best overdrive tone I've heard. It doesn't sound "grainy" like a lot of amps, again not real "distortion" like a lot of modern music uses, just a real nice musical overdrive, clean to dark bluesy..."

    SO thanks Steve for the great "SLO conversion" christmas present!
     
  10. nomadh

    nomadh Member

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    Great info Steve. I have a V30 (31112) that is my main amp currently. I really like it alot but...... I also have a peavey classic C50 with an incredibly sparkly clean fendery tone that the crate just can't get. The crate clean is always a bit grimy. Lower gain tubes didn't make a diff. Do you have any ideas how I may be able to do this on my crate? I have been wondering if its the difference between them being SE or its class or cathode biased etc. Something I suspect is power tube voltage. The C50 is over 400 V something and the V30 is in the 300's. Any ideas on if I'm on the right track and or how to modify it?
     
  11. steeve_a

    steeve_a Member

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    Looking at the schematic for the VC3112, you are right about the voltages being much lower than the Classic 50, with 317vdc going to the EL84 plates. FWIW the Classic 30 has about 332vdc going to the plates (but it doesn't have the great clean sounds of the C50). And cathode bias makes a big difference in the sound and response. Then again the Vox AC-30 has similar voltages and is cathode biased, but can get great clean tones with a lot of chime.

    For starters I would try changing a few of the parts in the phase inverter. Maybe replace the 0.1uF PI input cap with 0.01uF (or even lower). And redo the "tail" with a 1k2 resistor for R26 (instead of 475R) and a 47k resistor for R25 (instead of 22.1k). Everything else in the signal path for the Clean channel looks "Fender-ish" to me...

    Be sure to try different sounding 12AX7's for V1 (which is for the Clean channel). Some brands are brighter than others. And your choice of speaker(s) would make a big difference, too.

    Good luck!

    Steve Ahola
     
  12. rock_mumbles

    rock_mumbles Member

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    Hi Steve, can you elaborate a bit on the wiring for the cut circuit... I'd like to try it and I think I understand what you are saying but...

    My partial Soldano Conversion is amazing! I'm missing the power section resistors, and need to get a few other parts to put everything together properly but even as it is (unfinished) the amp is so much better than most amps.

    I think I want to put the treble bypass on a switch, I wish I hadn't wired it in so nice. ;) The amp seems a bit bright with single coils, I should try some other speakers, I've got a Carvin (old 100w) BR12 in it but I have a Fender OEM Eminence speaker that I should try to see what that sounds like.

    I've now had three people play it, all three liked it a lot. A friend (who owns dozens of tube amps) played the amp with a low end HB equipped Ibanez and was really impressed. His question, "does it sound this smooth with a Strat or a Tele?" the answer is no, it sounds real nice but it's a bit bright and still a little bit buzzy with single coils. That's one of the finishing touches that I hope the conjunctive filter takes care of.
     
  13. steeve_a

    steeve_a Member

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    The schematic shows a 50pF capacitor installed for C32, but on the boards I have seen there is no capacitor there. So you can hook two leads up to the two copper pads and add a Cut control on the bottom of the chassis. You can use a 250k linear pot as a variable resistor and wire it up as you prefer (with 10 being maximum cut or minimum cut). You can put the .005uF cap right on the wiper of the pot and then hook up the other lead to either of the two outside terminals.

    At this point of the circuit the signal is very strong so you don't need to use shielded cable to keep noise out. But I use it anyway, just so that the unshielded leads don't cause any unwanted oscillations in the circuitry that it passes over.

    Not knowing exactly what you have done and not done makes it difficult to make any specific recommendations. Let me know how it works when you finish installing the rest of the parts.

    I think that the Cut control will help more with the single coil pickups- along with the switch on the bright cap (which I need to add to mine!) The conjunctive filter has more of a subtle effect, just smoothing things out a bit.

    Your choice of preamp tubes can make a big difference, too. In my initial tests I used 12AX7's for all positions, mainly to check to see if the circuit was going to oscillate. But I personally prefer the smoother and less gainy sound of lower gain varieties like 5751 for V1 and V2.

    I wish it was easier to swap tubes in the V18! When testing out various fine-tune tweaks as well as different tubes I don't bother to put the chassis back in the cabinet. I secure the back panel with 2 screws and set the chassis on top of the cabinet, offset a bit so that I can plug in the speaker and the reverb cables.

    Hope that helps!

    Steve Ahola
     
  14. steeve_a

    steeve_a Member

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    I'm drawing this one up right now and may decide to build it next instead of the Trainwreck Liverpool 18. It looks like I will be able to reconfigure the tone stack to ODS specs, although I will need to omit the Jazz/Rock and Deep Switches...

    This will need one more pot (OD channel "Ratio" i.e., output level) which I might install on the top panel between the Reverb Control and the power light. I was thinking of putting in a channel select switch between the Volume and Treble controls- and maybe eventually hook that up to a relay. A mini-toggle is easily broken (unless I can find the new type with the short shaft!) so I may go with a push switch. It will be easy enough to wire in the PAB boost and the Mid boost, but the question is where to locate the switches. They all could be wired up to relays, with small pushbuttons and indicator lights mounted on the top panel- and wired up to a footswitch as well.

    But I first need to see if I can get some good Dumblesque tones out of the design which is based on the Hybrid drawing. It sounds great in a Bassman head with 6L6's and I think I can get it to work in the Crate V18 chassis. And if it works in the V18 it would be a good candidate for my V33- assuming that I can figure out how to reconfigure the channel switching relays.

    Steve Ahola

    EDIT It looks like I will need to cut a few traces for this mod. And it looks like I will be mounting 3 pots and a channel switching DPDT toggle switch on the bottom of the chassis for the OD input trim, OD output level and MV going into the PI... Well, that is why the good Lord made drills and Dremels! :roll
     
    Last edited: Dec 19, 2008
  15. echale3

    echale3 Member

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    LOL, the first V18 I got wound up pretending it was an arc welder the first time I powered it up. Lots of light and sizzling noises, accompanied by a little smoke, KWIM?

    It was a scratch-n-dent I got from MF (the box had been opened, but the amp didn't seem to have been removed--it was still in the protective bag). They replaced it with a NIB one, which was cool of them....
     
  16. steeve_a

    steeve_a Member

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    When I got my V33H from MF I peeked in the back of unit (which was factory sealed) and could see that the output transformer bracket was broken and that it was hanging down very precariously. I called up MF and talked to customer service who strongly recommended that I just return it for a full refund since these Crate amps were "catching fire and exploding" among other problems... :crazyguyMF wanted Crate to take back all of the defective amps that were being returned to them but Crate said "no backs!" So MF put all of the current line of Crate V-series amps on clearance sale just to get rid of them...

    I decided to check with Crate first and after I told them that I worked on guitar amps they promptly shipped me a replacement transformer no charge, which I thought was really cool. (If I would have had to ship the amp to a repair station I would have just sent it back to MF for a full refund.)

    Zzounds is still taking preorders for V18-112's for $150- they were supposed to be in stock on December 8th but that is way overdue so I think it could have been a mix-up. (Everyone else says that the amp is discontinued although it is still listed on the Crate website.) So the best bet for picking up these amps is your eBay or your local craigslist.

    Someone at ebay was parting out his V18! The amp stopped working so he took the chassis out and used the cabinet as an ext speaker, which he eventually sold without a speaker. He sold off the reverb tank on a seperate auction and the chassis (which didn't work) on a third auction. And there was a fourth auction for the wrong replacement Accutronics reverb tank that he bought for the amp...

    And musicians wonder why people always think that they are stoned out of their mind on drugs! :roll

    Steve Ahola
     
  17. scihibmxer@juno

    scihibmxer@juno Member

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    Same with our v33h (new model with 4 screws), transformer arrived hanging by the wires. I called MF first, they said they would take it back but try Crate and gave me the number. Talked with Rebecca at Crate, nice enough, had helped us earlier with warranty on the v18-112. But she said they don't stock transformers, and to contact a warranty crate service center. We are lucky enough to have one close, but he wanted to bill me up front for all the costs, and have me deal with crate, not my idea of a good deal. I am going to call crate (Loud) back, now that I know they will negociate... Thanks.
     
  18. steeve_a

    steeve_a Member

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    I'm not sure when exactly I will actually try this mod out- I have one untouched V18 chassis and already have two other projects for it! [​IMG]

    But this mod should offer even more high gain goodness than the Soldano SLO conversion, although I have my doubts that it would clean up at lower gain settings (like the SLO conversion does). My guess is that it would be kinda crunchy at low gain settings- not necessarily a bad thing for candy bars!

    http://www.blueguitar.org/new/schem/misc_mod/crate_18_xtc_conversion-layout.jpg

    http://www.blueguitar.org/new/schem/misc_mod/crate_18_xtc_conversion-schem.jpg

    I did not draw in any mods for the PI or output section- or even suggest a value for the (Master) Volume pot. I'd start off with the mods shown in the drawing and then take it from there. There was some question elsewhere as to whether the Bogner value of 500k for R15 would be excessive so it may need to be set to a lower value if there is too much gain in the preamp. One way to find out.... Boooommmm! :rotflmao

    Steve Ahola

    Crate V18 to Bogner Ecstacy OD:

    R2 Replace 2k7 with 820R [V1a Rk]
    C6 Replace 2.2uF with 0.68uF [V1a Ck]
    C1 Replace 0.047uF with 0.0047uF [V1a coupling cap]
    R6 (470k) Remove
    C2 (.001uF) Remove and jumper
    C3 (470pF) Remove and jumper
    R10 (470k) Remove
    CW1 Replace 250kA pot with 500kA pot &
    CW1 ... add 0.001uF bright cap
    R4 (2M2) Remove
    R65 Replace 68k with 470k &
    R65 ... add 470pF cap in parallel
    Add 500k resistor from V1b grid (pin 7) to ground
    Add 100k resistor from V1b grid (pin 7) to SPST footswitch to ground
    ... [This is a Gain Boost switch normally closed for low gain position]
    R3 Replace 220k with 100k [V1b Rp]
    R5 Replace 2k7 with 4k7 & [V1b Rk]
    Add 4k7 & 2.2uF cap from V1b cathode (pin 8) to SPST switch to ground
    ... [This is "Structure" switch]
    C7 Replace 0.022uF with 0.0022uF [V1b coupling cap]
    Add 500k/500k voltage divider to ground between C7 and R61
    R61 Replace 220k with 500k &
    R61 ... add 470pF cap in parallel
    R12 (1M) Remove
    R11 (100k) Add 470pF cap in parallel [V2a Rp]
    R17 Replace 220k with 500k &
    R17 ... add 470pF cap in parallel
    R15 Replace 100k with 500k
    R16 Replace 2k7 with 1k [V2b Rk]
    C13 (2.2uF) Remove [V2b Ck]

    Note: The Bogner schematic lists several 500k resistors. 510k would be the closest standard value although 470k could also be used. You can find the Bogner schematic I used over at Schematic Heaven.
     
  19. wagdog

    wagdog Member

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    Steve,

    I'm really enjoying the SLO mod on the v18. So much so that I'm planning to do the same mod to my v33h.

    If possible, could you give me your thoughts on the following...

    The removal of R6 on the v18 would be the equivalent of removing R5 on the v33. However that would kill the clean channel of the v33. Is the removal of this resistor and the parts that follow it a critical part of the overall tone of the amp?

    In the v33, I'm a little confused about relay 2C. In order to match the v18, removing R8 and jumpering over the relay (from C7 to R11) would do that, but what would happen if the relay was toggled to the clean channel?

    I think I'm more inclined to remove the clean channel completely anyway, but I figured I'd get your thoughts on it.

    Thanks!

    Wag
     
  20. steeve_a

    steeve_a Member

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    My thoughts on putting the Soldano mod into the V33H would be to leave V1b in the circuit at all times, but take advantage of the channel switching capability to use the Clean channel volume control. I have not examined my V33 yet so I haven't looked into the details yet.

    For starters you could just wire up the OD with the Soldano mod (do not remove R5) and leave the channel select switch in OD mode. Once you figure out if that means it is energized or de-energized you can either put a jumper across the switch leads or disconnect one of the leads.

    One alternative would be to look into the latest V33 mods from dnator:

    http://dnator.50webs.com/index.html

    He has incorporated some of the stuff from the Soldano SLO as well as the Bogner Ecstacy, and his mods evidently work well with the channel switching functions of the V33.

    FWIW I'm still working on the plans for the D*mble ODS conversion for my 4th V18- I'll be adding a channel switching relay as well as the Rock/Jazz, PAB, Midboost and Bright switches so it should be pretty slick!

    Steve Ahola
     

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