Members ZombieCat Posted January 26, 2009 Members Share Posted January 26, 2009 Steve, I am looking at the Type 2 master volume circuit and I was hoping to get some clarification. Lug 1 of the pots is shown connecting to a "dot". Normally (well from what little I remember and a quick search on the net showed) when a pot is wired as a volume control, lug 1 goes to ground. Is the "dot" indicating ground? Since lug 1 on both pots are connected to the same source, it also makes me think this is ground as that should be the only point in common both pots have. Link to comment Share on other sites More sharing options...
Members sssteeve Posted January 27, 2009 Members Share Posted January 27, 2009 Steve,I am looking at the Type 2 master volume circuit and I was hoping to get some clarification. Lug 1 of the pots is shown connecting to a "dot". Normally (well from what little I remember and a quick search on the net showed) when a pot is wired as a volume control, lug 1 goes to ground. Is the "dot" indicating ground? Since lug 1 on both pots are connected to the same source, it also makes me think this is ground as that should be the only point in common both pots have. I guess that drawing is easier to follow when you are looking at all 4 MV circuits. The caps and resistors shown are from a typical Fender blackface/silverface eyelet board. You would normally have two more resistors mounted from the top of the two caps to the "dot" in a V formation which would be the bias voltage. Only with the Crate V-18 and V-33, the amp is cathode biased so the dot would be ground. Also the drawing shows the wipers going to "pins -5 of output tubes"- that would be pins 2 for EL84's. I just put the Pentode/Triode switch in my V-18 Trainwreck Rocket and that works really great! It cuts the volume considerably and darkens the tone a bit but I believe that you still get power tube distortion (which you would not get when you tuern down a MV). Here is a drawing for adding the Pentode/Triode switch: http://www.blueguitar.org/new/schem/misc_mod/crate_v18_pentode-triode_switch.jpg I also reverted the output section to the stock 470k/10k values to bring up the overall volume, and also boosted the gain in the IC stage immediately before the PI by replacing the 12k R25 NFB resistor with a 20k resistor. I figure that the Rocket/AC30 preamp has only 2 gain stages (plus one cathode follower) so the overall gain is going to be considerably less than a stock V18 (or the Soldano-ized V18). Hence the boost in the IC1-B IC stage. It should be noted that you can only get so much overall gain from IC1-B; the +/- 14.7vdc supply is going to limit the signal to about 25 volts peak to peak. If you push it any harder than that it will start chopping off the peaks, thus compressing the sound. I tried bypassing IC1-B in my Soldano V18 and boosting the gain in the tube stages a little bit to compensate for the loss in gain from the IC. The net result was a raspier sound with a lot more noise. I went back to the previous circuit, but increased R25 from 12k to 18k and got a really nice boost in level: much better! So I think that we can use that IC stage to good advantage, in boosting the signal going into the PI as needed. (In the real Soldano SLO we have two DC-coupled pairs for the FX loop which are between the preamp and the PI, which adds gain and drive to the signal.) BTW that Rocket is sounding really nice- especially with the NOS 6BQ5's I just put in it after cutting the tube socket leg for Pin 1 of V4... Steve Ahola Link to comment Share on other sites More sharing options...
Members ZombieCat Posted January 28, 2009 Members Share Posted January 28, 2009 Steve, Thanks for the response. As soon as I get over this cold, I am going to tear into my amp and take a look at things before doing this mod. I am sure I will have some more questions after that. Link to comment Share on other sites More sharing options...
Members wagdog Posted January 28, 2009 Author Members Share Posted January 28, 2009 I gotta tell you guys, the v33 with the SLO mod is an incredible amp. I just got done jamming on it, it's so responsive and the overdrive sounds are amazing. I played it through my 4x12 for a while, then I played it through the stock 12" speaker in my HRD, just sounds great. I'm gonna cop the mid-boost from this amp and put it on my v18. I still need new speakers for the v18, those crate speakers are so awful (I know I keep saying that). Link to comment Share on other sites More sharing options...
Members SciHi Posted January 29, 2009 Members Share Posted January 29, 2009 I also reverted the output section to the stock 470k/10k values to bring up the overall volume...Steve Ahola SO did you revert back to stock arrange too, grid load then grid resistor? Or leave it in the corrected arrangement, grid resistor then grid load, and just go back to the stock values? I was just putting together an order for the 470K 1 watters so I could correct the arrangement, leaving the values stock... Link to comment Share on other sites More sharing options...
Members sssteeve Posted January 29, 2009 Members Share Posted January 29, 2009 ... I'm gonna cop the mid-boost from this amp and put it on my v18. I still need new speakers for the v18, those crate speakers are so awful (I know I keep saying that). Well, here 'tis: http://www.blueguitar.org/new/schem/misc_mod/crate_v18_mid-boost.jpg I decided that I wanted to add it to my Soldano-ized V18 myself! In case the drawing isn't clear you remove C16 and R22, and then mount the 4 components in a little triangle (or flattened pyramid shape). Make sure that the caps and resistors are in the correct order. You can connect a single wire to the two joints in the middle and then run that to the switch which goes to ground. (The switch is normally closed for the unboosted mode- open for the boosted mode.) For ground you can run it to the copper pad of C16 closest to the edge of the PCB. Only problem is adding switches to the V18! Regular mini-toggle switches will not survive long on the top panel. There isn't much room for full-sized toggle switches. Small pushbutton switches should hold up but the ones I have found do not indicate their state. Best solution I have seen so far for this dilemma is the new Egnator Rebel 20 which uses short bat mini toggle switches. These suckers will never break off! (Don't think of just cutting down the bat on a regular mini-toggle switch- there is a spring inside the handle!) I need to call around to see if anyone is stocking them... I'm also thinking of adding the V33H Presence Switch to my SLO V18- if I can figure out where to put the damned switch! It will cut the highs a bit, and unlike a bright switch it will be independent of the settings of the gain control. I figure it would be handy if I ever decide to plug in a guitar with a single coil pickup. Here is the drawing for the Presence Switch: http://www.blueguitar.org/new/schem/misc_mod/crate_v18_presence_switch.jpg BTW Radio Shack has some round SPDT toggle switches with a full-sized bat but a smaller body so that they might work for simple switching on the V18 top panel. Their stock number is 275-603 and I think I'll mount them half way between the controls, but up on the double line with the labels (gain, volume, etc.) 3 switches for the bright cap, presence and mid boost. The switches might eventually get broken but I do think that they would stand a fighting chance if you are careful. (The mini-toggles would soon be toast!) Steve Ahola P.S. I believe that you have mentioned using a low gain 12A_7 for V3 in your V18 and/or V33H. You are referring to the PI tube- right? The one the farthest from the input jack... I ask because it is my observation that it would lower the power output of an amp. I use low gain tubes in the preamp for less gain and distortion, but the only time I use a low gain tube in the PI is if I need to cut the output power a bit (like on my PV Delta Blues 115 which is LOUD!) Link to comment Share on other sites More sharing options...
Members sssteeve Posted January 29, 2009 Members Share Posted January 29, 2009 Steve, Thanks for the response. As soon as I get over this cold, I am going to tear into my amp and take a look at things before doing this mod. I am sure I will have some more questions after that. Here is the drawing for the Type 2 Master Volume... take 2 and call me in the morning! http://www.blueguitar.org/new/schem/misc_mod/crate_v18_type_2_mv.jpgSteve Ahola Link to comment Share on other sites More sharing options...
Members sssteeve Posted January 29, 2009 Members Share Posted January 29, 2009 SO did you revert back to stock arrange too, grid load then grid resistor? Or leave it in the corrected arrangement, grid resistor then grid load, and just go back to the stock values? I was just putting together an order for the 470K 1 watters so I could correct the arrangement, leaving the values stock...Well, on my SLO V18 and V33H I left the resistors completely stock, but when I reverted the values for my Trainwreck Rocket I still corrected the factory miswiring of the board. It seems to work fine the other way but it still bugs me... Steve Ahola Link to comment Share on other sites More sharing options...
Members wagdog Posted January 30, 2009 Author Members Share Posted January 30, 2009 P.S. I believe that you have mentioned using a low gain 12A_7 for V3 in your V18 and/or V33H. You are referring to the PI tube- right? The one the farthest from the input jack... I ask because it is my observation that it would lower the power output of an amp. I use low gain tubes in the preamp for less gain and distortion, but the only time I use a low gain tube in the PI is if I need to cut the output power a bit (like on my PV Delta Blues 115 which is LOUD!) Yeah, my v33 has a 12au7 in the PI tube. It definitely smoothed out the amp. I don't know what you're finding, but I've found that this amp has *plenty* of loud left in it. I most recently ended up going with 3x 12ax7's in the v18, but as I've said before, I need to replace the speakers before I can hear any significant difference in tube tone in that amp. It's on my list of things to do - I'll probably have the money for them next month sometime. Link to comment Share on other sites More sharing options...
Members ZombieCat Posted January 31, 2009 Members Share Posted January 31, 2009 Here is the drawing for the Type 2 Master Volume... take 2 and call me in the morning! http://www.blueguitar.org/new/schem/misc_mod/crate_v18_type_2_mv.jpgSteve Ahola LOL! Thanks for the diagram. It is so simple even someone like me can follow it. Now to see if my local Radio Shack has some 10k resistors.I am also going to check out that mid boost mod.So many mods, so little time. Link to comment Share on other sites More sharing options...
Members ZombieCat Posted January 31, 2009 Members Share Posted January 31, 2009 Okay more questions. After my second cup of coffee, I noticed that the diagram you provided is for the V18. I am wanting to do this mod to a V33. So I dug up the schematics for the two amps and found the matching resistors. This is what I got: V18 R46 = V33 R71V18 R45 = V33 R98V18 R44 = V33 R73V18 R43 = V33 R96 That part was simple enough but the one thing that is bugging me right now is that the V33 has another pair of power tubes. Does anything have to be done to those? Sorry if this is all very noobish but my electronics knowledge is extremely rusty and I was never that good at component level stuff. I primarily did board swaps in radios while in the Air Force. Link to comment Share on other sites More sharing options...
Members wagdog Posted January 31, 2009 Author Members Share Posted January 31, 2009 Zombie, you don't need mod the power amp section, it's not necessary. I'm pretty sure Steve mentioned that he rolled back those mods on the v18 (as did I). I never did them on the v33 either. Link to comment Share on other sites More sharing options...
Members ZombieCat Posted February 2, 2009 Members Share Posted February 2, 2009 Zombie, you don't need mod the power amp section, it's not necessary. I'm pretty sure Steve mentioned that he rolled back those mods on the v18 (as did I). I never did them on the v33 either.Yes he did roll back that mod but we are actually talking about replacing the grid load resistors with potentiometers to get more control of the volume. I would not say it is a necessary mod but I sure would find it handy. Link to comment Share on other sites More sharing options...
Members Edge11 Posted March 14, 2009 Members Share Posted March 14, 2009 What wattage are the resistors and what voltage are the caps? Link to comment Share on other sites More sharing options...
Members Strikerfox Posted March 20, 2009 Members Share Posted March 20, 2009 Hey guys, ive been reading up the work you have done on these amps and i just have to say im really impressed and inspired. I actually bought a V33H a few months ago from GC for $125... talk about a deal. Although i normally use pedals on the clean channel on the amp, for the price i paid i want to try the mod. my question here (incase i missed it) what tube type do you recommend for the preamp. 12ax7, au, at, on the V33 to get a smooth clean sound and growling crunch / distortion. Also, if you guys use od pedals, how do they match up with the amp, as i like to use my timmy and zendrive to get a lil more boost/ color to the sound. Thanks. Link to comment Share on other sites More sharing options...
Members Edge11 Posted March 26, 2009 Members Share Posted March 26, 2009 Can some one come up with a part # list on mouser for us please? Link to comment Share on other sites More sharing options...
Members wagdog Posted March 26, 2009 Author Members Share Posted March 26, 2009 Hey guys, ive been reading up the work you have done on these amps and i just have to say im really impressed and inspired. I actually bought a V33H a few months ago from GC for $125... talk about a deal. Although i normally use pedals on the clean channel on the amp, for the price i paid i want to try the mod. my question here (incase i missed it) what tube type do you recommend for the preamp. 12ax7, au, at, on the V33 to get a smooth clean sound and growling crunch / distortion. Also, if you guys use od pedals, how do they match up with the amp, as i like to use my timmy and zendrive to get a lil more boost/ color to the sound. Thanks. Tube wise, I think I have my slo modded v33 set up in this fashion now, starting at v1: 12ax7, 12ay7 and 12au7 for the PI. el84's are stock, except for an old fender el84 I had (gt actually I believe). I think it's in there 'cause I was experimenting with it and forgot to take it out. At some point I would like to get a full compliment of new JJ tubes. Anyway, with the SLO mod, the amp pretty much sings. The lower gain preamp tubes do give it more usable cleans. Remember that for my amp, the one that I started this thread with, I completely blew out the clean channel by removing and wiring around the relays, so for cleans, I just turn down the gain. It's still a very nice clean sound with this SLO preamp configuration. Steve says he did his and left the clean channel intact. It wasn't an issue for me. mblooper45: I don't want to sound like an ass, but, you should be prepared to source your own parts and figure out what voltage resistors and caps you need. If you can't do this, you probably shouldn't be modding your amp. Again, sorry, I really don't want to come off like mr.knowitallampmodder (I'm not), but I don't recommend doing this kind of work if you can't figure that kind of stuff out on your own. There is just too much of a chance for error that you will have to troubleshoot, or worse... Link to comment Share on other sites More sharing options...
Members Edge11 Posted March 26, 2009 Members Share Posted March 26, 2009 Tube wise, I think I have my slo modded v33 set up in this fashion now, starting at v1: 12ax7, 12ay7 and 12au7 for the PI. el84's are stock, except for an old fender el84 I had (gt actually I believe). I think it's in there 'cause I was experimenting with it and forgot to take it out. At some point I would like to get a full compliment of new JJ tubes. Anyway, with the SLO mod, the amp pretty much sings. The lower gain preamp tubes do give it more usable cleans. Remember that for my amp, the one that I started this thread with, I completely blew out the clean channel by removing and wiring around the relays, so for cleans, I just turn down the gain. It's still a very nice clean sound with this SLO preamp configuration. Steve says he did his and left the clean channel intact. It wasn't an issue for me. mblooper45: I don't want to sound like an ass, but, you should be prepared to source your own parts and figure out what voltage resistors and caps you need. If you can't do this, you probably shouldn't be modding your amp. Again, sorry, I really don't want to come off like mr.knowitallampmodder (I'm not), but I don't recommend doing this kind of work if you can't figure that kind of stuff out on your own. There is just too much of a chance for error that you will have to troubleshoot, or worse... ok mr.knowitallampmodder I'm just kinda nervous because this is my first big boy amp i've gotten to mod, (aka its something other than a valve junior) let me see if i got this right600-630VDC for the poly caps1kv for the ceramic caps25vdc for the electrolytics1/2 watt resistors?????thanks. Link to comment Share on other sites More sharing options...
Members wagdog Posted March 27, 2009 Author Members Share Posted March 27, 2009 ok mr.knowitallampmodder I'm just kinda nervous because this is my first big boy amp i've gotten to mod, (aka its something other than a valve junior) let me see if i got this right 600-630VDC for the poly caps 1kv for the ceramic caps 25vdc for the electrolytics 1/2 watt resistors????? thanks. Use parts that have the same (or greater) voltage and wattage as the ones you're replacing. Look at the resistors. The difference between 1/4w, 1/2w and 1w resistors is pretty obvious. The electrolytic caps are marked. For the ceramic and poly caps you should have an idea as to the voltages in that part of the circuit. It sounds like you're on the right track. Link to comment Share on other sites More sharing options...
Members Strikerfox Posted April 1, 2009 Members Share Posted April 1, 2009 I decided to use a Tungsol reissue 12ax7 on the V1, EHX gold pin 12ax on the V2 and NOS JAN Phillips 12at7 on the Phase Inverter with 4 Genalex Gold Lions el84. All i can say is WOW. the sound is off the scale. Rich harmonics, smooth clean channel, perfect crunch sound and excellent dirt channel. Basically all i can say is this: sounds as good as any boutique amp, and a great alternative to my 1965 original Vox. Thanks for the help and info guys. (Big ole smile due to awesomeness of the tone) Link to comment Share on other sites More sharing options...
Members Strikerfox Posted April 10, 2009 Members Share Posted April 10, 2009 Just as a follow up, I've been getting more used to the amp, the controls and the sound. Just amazing, but you have to crank it up to get the outmost tone, very much like the SLO. Quite responsive to the pick attack and guitar volume and the TMB. I had my friend, who is an amp technician, try out the amp and asked me about the mod. He immediately told and modified two people who he knew had the V33 as well. HIGHLY RECOMMEND THIS MOD. ITS NO LONGER A CRATE. Link to comment Share on other sites More sharing options...
Members ZombieCat Posted April 23, 2009 Members Share Posted April 23, 2009 So I have come back re-read this thread. With the addition of Steve's design that allows keeping the clean channel, I am going to do this mod. I am curious to those that have done it, how long did it take? Link to comment Share on other sites More sharing options...
Members wagdog Posted April 23, 2009 Author Members Share Posted April 23, 2009 Took me about 4 hours, if I remember correctly. Link to comment Share on other sites More sharing options...
Members ZombieCat Posted April 23, 2009 Members Share Posted April 23, 2009 4 hours is not bad at all. Thanks for the reply wagdog. I do have a couple of questions/clarifications. 1. The resistors R3,R78,R15,R28 are labeled with the values 1k8 or 1k2. I am pretty sure this mean 1.8 k and 1.2 k ohm resistors but want to be sure. 2. The cap added in parallel to R9 is listed as .001. I just want to be sure that is a .001 F cap since all the other caps listed are as uF. Link to comment Share on other sites More sharing options...
Members wagdog Posted April 24, 2009 Author Members Share Posted April 24, 2009 2. The cap added in parallel to R9 is listed as .001. I just want to be sure that is a .001 F cap since all the other caps listed are as uF. It's a .001uF - the original post on this thread shows that. Good luck! Link to comment Share on other sites More sharing options...
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