Crate V5 mods... anyone?

[Christopher Whitlow]

Welcome to the forum.

If you want a lower gain 12AX7, try a 5751 or a 12AY7/6072.

The 12AT7 isn't a lower gain 12AX7, it has different specs and operation points. Other than sharing the same pinout and dual triode configuration, the two are more dissimilar than similar.

Having said that, there is nothing wrong with trying a 12AT7. It won't hurt anything, and who knows, you might even like the tone.

Hey there! Thank you for giving me options to look into and thank you for the welcome.

 

[Chris Paul]

Volume/Gain Mod

Just did this mod today and it was well worth the time and effort! Thanks a ton JimP :)

 

[Christopher Whitlow]

Sorry for the the post earlier, I was on a different account. The tone/volume mod is super easy and just what I needed. I am just learning the finer points of soldering and was a bit leery of the PCB board due to the small parts and all that. Well it went real easy with exception of clearing out solder on a couple spots. All my soldering experience has pretty much been guitar pots, switches, and repairing cables. Oh, and I can "sweat" a pipe too ;) I have a handful of very nice pedals and really dont need the amp to have tone control...for now. I am very pleased with how this amp sounds! I played every small valve amp I could get my hands on in the last couple years and this one was on the bottom of the list as far as sound quality goes. Now it sounds IMHO better than my friends stock Vox with tube upgrades by a long shot and I liked his amp a lot.

Now I have a follow up question of sorts. I feel as though the highs are too sharp even through my "darkest" guitar. I am wondering if there is a resistor or cap that can be swapped out to tame the "ice pick" a bit. I already have a home made treble blocker installed behind the grill, which does help, but I would like to run the amp with just a tuner and a wah and not feel like I need my EQ. Thanks again all who made this thread what it is!

 

[Christopher Whitlow]

Quick question about the sweep of the volume pot. I have done the above mod and now would like to know if there is a to slow down the sweep of the volume pot. This little dude is loud! Friend of mine uses my Cube 30x when he comes over and the 5watt tube is every bit as loud as the Roland. The amount of volume isnt really a problem, Its how fast it get loud that is hard to deal with. At 1 1/2 to 2 it starts coming on real loud and seems to top out at 7-9 on the dial. Can I use a different value pot like I have done in guitars or is this a more complicated fix? I really need to be able to play at actual bedroom volumes and I cant afford a hot plate so I am hoping I can slow down the sweep so that 0 thru 3 or 4 are usable in the house when others are watching the tube. Thanks all!

 

[tunghaichuan]

Quick question about the sweep of the volume pot. I have done the above mod and now would like to know if there is a to slow down the sweep of the volume pot. This little dude is loud! Friend of mine uses my Cube 30x when he comes over and the 5watt tube is every bit as loud as the Roland. The amount of volume isnt really a problem, Its how fast it get loud that is hard to deal with. At 1 1/2 to 2 it starts coming on real loud and seems to top out at 7-9 on the dial. Can I use a different value pot like I have done in guitars or is this a more complicated fix? I really need to be able to play at actual bedroom volumes and I cant afford a hot plate so I am hoping I can slow down the sweep so that 0 thru 3 or 4 are usable in the house when others are watching the tube. Thanks all!

The problem with the pot isn't the value, it's the taper. If your volume is coming up to fast, then it is most likely a linear taper pot. What you want is a log or audio taper. It may or may not be hard to find in the right value. What is the value?

 

[jim p]

volume pot sensitivity

I wish the schematic mark ups were still on line, oh well. I should remember the mod, but it has been awhile. I don’t recall if the tone pot is a linear or audio (log) taper but there is way more signal across it then required you could parallel it with 25k to 50k ohms. The mod was to just use what you have with no new parts required. As far as ice pick tone I think just having an op amp as the input stage causes a brighter and colder tone from the amp. You could try adding some feedback capacitance on the first tube stage say 33pf to 100pf from the plate pin 6 to the control grid pin 7.

 

[Christopher Whitlow]

Thanks guys! I'm not afraid to add a resistor or change the entire pot. I did this after practicing on junk toys and have since installed a Keeley type mod in my DS-1 and "true" bypassed my CryBaby. Turns out a friend of mine is really good at soldering and gave me some great pointers so now my parts come out clean and get good connections MOST the time :) At this point my biggest biggest problem is lack of knowledge, I was all proud because I remembered that resistors in series add up in value lol!
Jim, when you say to parallel the pot with 25-50k is that a resistor across the pot lugs? If so thats way easy to check out while I look into the taper. I have CTS and Alpha pots lying around but mostly all of them will be 250 500k A&Bs for my guitars so if the amps pot is labeled with a low value can I just replace with a higher value audio pot?

I know these are way newb questions and I appreciate you guys still checking in on this thread. Any suggested reading/study material for an intelligent mechanically inclined older gentleman to learn from? I found resistor charts and schematic keys and studied PCBs to see the power flow and I sorta get it but think an "electronics for dummies" sorta thing might be in order.

 

[tunghaichuan]

I know these are way newb questions and I appreciate you guys still checking in on this thread. Any suggested reading/study material for an intelligent mechanically inclined older gentleman to learn from? I found resistor charts and schematic keys and studied PCBs to see the power flow and I sorta get it but think an "electronics for dummies" sorta thing might be in order.

Here is the motherload of tube amp related books:

Peter Millett's Tech Books Online

There is enough there to keep you busy for a long time.

Here is another good book to start with:

Jack Darr's Guitar Amplifier Handbook

This is a good, basic intro to tube amps. It was written in the 60s and later expanded in the early 70s so there is no discussion of FX loops, channel switching, or distortion circuits, but it covers the basics of how tubes and amps work, and how to fix them. It is also available in print, and it is well worth it to have a hard copy as the above .pdf files only are about half of the book. The other half is a bunch of 60s and 70s era tube amp schematics, which make the book well worth the price.

 

[jim p]

Yes just put the resistor across the two outside lugs of the pot to parallel it. I looked at the schematic and originally the signal to the second tube was across a 10k resistor so with adding the resistor in parallel with the 250k pot the resistance will be 22k or 42k so still more signal but closer to the original level before the mod. If you don’t have a schematic for the amp just call Crate (Loud Technologies) and they will e-mail you a PDF.

 

[Christopher Whitlow]

Here is the motherload of tube amp related books:

Peter Millett's Tech Books Online

There is enough there to keep you busy for a long time.

Here is another good book to start with:

Jack Darr's Guitar Amplifier Handbook

This is a good, basic intro to tube amps. It was written in the 60s and later expanded in the early 70s so there is no discussion of FX loops, channel switching, or distortion circuits, but it covers the basics of how tubes and amps work, and how to fix them. It is also available in print, and it is well worth it to have a hard copy as the above .pdf files only are about half of the book. The other half is a bunch of 60s and 70s era tube amp schematics, which make the book well worth the price.

Huge thanks!

 

[Christopher Whitlow]

Yes just put the resistor across the two outside lugs of the pot to parallel it. I looked at the schematic and originally the signal to the second tube was across a 10k resistor so with adding the resistor in parallel with the 250k pot the resistance will be 22k or 42k so still more signal but closer to the original level before the mod. If you don’t have a schematic for the amp just call Crate (Loud Technologies) and they will e-mail you a PDF.

Going to remove op amp per your instructions around post #160 or so. Wish I would have been doing this when the topic was fresh but here goes another question... will the op amp removal adversely affect the volume/gain mod. I'm looking at the board and my untrained eye says no but wouls hate to do it and wind up at full volume because I read the traces wrong! I really think the answer is no but want to make sure because this thing makes me nervous now that I know how careful I have to be with it. I never should have started reading, these things hold a lot of voltage!!!!!
EDIT: My bad, meant to say thank you for your help!

 

[jim p]

If you do the mod at post #160 the stock volume pot will be a volume pot again and the tone pot will be a tone pot again with C6 installed. So you won’t have the volume pot acting as a gain control while you have the tone pot acting as a volume control as you do now.

 

[Christopher Whitlow]

If you do the mod at post #160 the stock volume pot will be a volume pot again and the tone pot will be a tone pot again with C6 installed. So you won’t have the volume pot acting as a gain control while you have the tone pot acting as a volume control as you do now.

Very nice! I was seriously considering trying to install a gain pot now in addition to the volume and tone. Im looking over the old posts and studying the layout of the amp and sounds/looks fairly simple to put one in. This is an awesome learning platform! I will keep reporting my progress in case others are still interested in the mod :) I have some new soldering tips coming and I think I will wait on those. The shovel head of a tip that came with mine is hard to get into those small spaces.

 

[Christopher Whitlow]

Figures! I have no output but do have a very slight hum that is barely audible. I looked over all my joints and all looks OK. Could it have anything to do with my previous volume/tone control mod?

 

[jim p]

things to check

Here is a list of things to check and ohmmeter to see if the connections are correct.


With the op amp out you should have C24 C25 and C26 removed with a jumper from pin 3 of the op amp to the junction of R1 and R2 with R2 removed. That is the signal from the guitar to the first triode. Pin 7 of the op amp should be grounded C27 removed R27 should be removed with a jumper from the junction of R27, R7 and R15 jumpered to pin 6 of the op amp. C6 should be installed R15 should be installed. If you ohmmeter from the tip of the ¼ inch jack to pin 7 of the 12AX7 you should read the value of R1 47k also check to ground should be 1 Meg. Ohmmeter pin 2 of the 12AX7 to ground you should have zero with volume pot turned down to 250k at volume at full clockwise. From pin 2 of the 12AX7 to R9 should read approx 500k to 600k.

Another source for amp modifications and help is over at sewatt.com

 

[Christopher Whitlow]

Here is a list of things to check and ohmmeter to see if the connections are correct.


With the op amp out you should have C24 C25 and C26 removed with a jumper from pin 3 of the op amp to the junction of R1 and R2 with R2 removed. That is the signal from the guitar to the first triode. Pin 7 of the op amp should be grounded C27 removed R27 should be removed with a jumper from the junction of R27, R7 and R15 jumpered to pin 6 of the op amp. C6 should be installed R15 should be installed. If you ohmmeter from the tip of the ¼ inch jack to pin 7 of the 12AX7 you should read the value of R1 47k also check to ground should be 1 Meg. Ohmmeter pin 2 of the 12AX7 to ground you should have zero with volume pot turned down to 250k at volume at full clockwise. From pin 2 of the 12AX7 to R9 should read approx 500k to 600k.

Another source for amp modifications and help is over at sewatt.com

You are awesome! I know already that one problem will be me not realizing I interrupted the flow when I did the second mod by NOT replacing c6 or c15. Amazing what you miss when you dont know what to look for. I have a multi meter and will check values at those critical points a Bnd replace my missing parts in the signal path then report back. I have the book mentioned above on it's way and Im learning a bunch from the pdf that explains amps in the 70's and before. When I recieved this amp free I decided this was my chance to learn how they work and boy howdy am I a learnin! Thnx again folks!

 

[vinyl_key]

Hey all, proud owner of a V5 that I modded per post #168 ~2 years ago with a few questions after re-reading all 23 pages of this thread :poke:

My current set up for my Crate is: op-amp removed and stock 12AX7 replaced with a 12AT7.

• What are some ways to make the tone control act like like a normal tone control. I've seen mentions of changes to the tone stack in this thread, but they're a bit hard to follow what's going on with more than half of the images gone.
• Will a Weber Signature AlNiCo 10 fit in? The depth is longer than the 4" that will fit, but it looks like the magnet (with the cover removed) is skinny enough to just stick past the amp enclosure. If the AlNiCo doesn't fit, a Sig ceramic will make do.

Thanks for the wealth of information in this thread

 

[jim p]

The Weber AlNiCo will fit without the shielding around the magnet. You could consider the Eminence Legend 10516 as a speaker choice also. The output transformer impedance is really 16 ohms so you may want to get a 16 ohm speaker. On the tone control if you remove C5 and C4 and change C1 to 470nF then the tone control will be set to bass at CCW and treble at full CW. The op amp used to boost the treble so to make up for that changing the first triode bypass cap to 470nF will make up for not having the op amp boost.

 

[SciHi]

• What are some ways to make the tone control act like like a normal tone control. I've seen mentions of changes to the tone stack in this thread, but they're a bit hard to follow what's going on with more than half of the images gone.

Since the stock tone pot has the wiper to ground, I converted it to a Marshall normal channel tone control. I can post a partial schematic for this mod when I return home after the 4th... http://mhuss.com/18watt/schematics/18wattLite.gif

OK, maybe this will help.

 

[SciHi]

I was talking with Rock Mumbles this evening and he reminded me of the power tube fixes for this amp. First, the screen resistor needs moved to the correct position, then the EL84 bias needs corrected, depending on the size of the cathode bypass cap, 240-270R cathode resistor. I also added a master volume but it is not necessary...

 

[rock_mumbles]

I was talking with Rock Mumbles this evening and he reminded me of the power tube fixes for this amp. First, the screen resistor needs moved to the correct position, then the EL84 bias needs corrected, depending on the size of the cathode bypass cap, 240-270R cathode resistor. I also added a master volume but it is not necessary...

I used a 240 ohm cathode resistor and wish it was still a bit smaller, although I do have a 100 ohm (not-a) sag resistor that drops a few volts. My plate voltage is now 297V and the screen is 289V, prior to reworking the dropping resistor and screen resistor the screen was about 310V and the plate about 300V ... not good ...

I love this amp with the circuit I now have in it, I pulled the minimum number of parts to be able to rework the circuit.
First I pulled both pots, the stock op-amp gain control for the volume control ??? what were they thinking, and the tone pot mess, although if you want to leave the tone pot in circuit it can be rebuilt to the Marshall 18 Watt "normal" tone control, which works really nice for a Marshally V5.

I pulled R1, R9, R10, R15 and R27. I cut R7 as it's mounted on top of the socket (it might not be a bad idea to cut D9 and D10, so theres no power to the op amp even though it's not connected to anything anymore)

The easiest way to redo the input to bypass the op amp and associated circuitry is to jumper R10 and run a 68k (or less) resistor from the right R10 via (pcb hole) to the top R1 via, closest to C1. You should be able to place the input resistor lead into the right R10 via and bend the lead over and up into the left via to form the jumper. I put insulation tubing on the exposed input resistor leads.

For V1a, R3 gets switched to a 2.7k and C1 to a 0.68uf (film)

V1b is fine stock

R17 the EL84 cathode resistor is way too large at a 330 ohm it should be about 240 ohms.

Instead of just moving the screen supply like SciHi showed above, I replaced R25 with two resistors in series, put two 2.2k 2 watt resistors in series one leg goes into the R25 via (pcb hole) closest to C16, I put the other leg into the left via labeled R23 (unused) then I connected the left leg of R18 (screen resistor) to the junction of the two 2,2k resistors.

Then for the tone control/volume pot, I used the Framus mid control with a 500k Audio volume pot. The left via of R9 (closest to C2) is used for the tone control input and the volume control output connects to the left via of R27
here's a schematic of the tone/volume control ...

 

[bcdon]

That is some serious hacking, very interesting!

 

[rock_mumbles]

It's completed, to tame the highs a bit I ended up putting a 680pf cap across R6, that did the trick.

I pulled the Weber Ceramic Sig 10 (smooth cone) and replaced it with a new Jensen C10Q I picked up for $20 ... I decided I wanted to keep the Weber Sig 10, it sounded a lot better in the Crate combo cab, fortunately the Framus mid control deals with the boxy heavy midrange tone of the Jensen pretty well.

The Weber Sig 10 is a nice affordable speaker for the Crate V5, it sounds really good in the small Crate combo cabinet. With my Strat the Jensen C10Q (which has a larger magnet and just barely fits) has a bit too much of a midrange dominant tone (for me) ...

I agree with jim p that the Eminence 1058/10516 series speakers are really nice sounding, it was the best sounding speaker we tried in my brother's Vox AC4TV ...

 

[Will Muhovich]

So, I love the ideas presented here, and I know it's been a while since you posted this, but is there any chance you have a better schematic with illustrations or notes added, and/or gut shots of the mods as described? I may try the easy mods you suggest first and replace the speaker, but this sounds like it might be easier than getting or making a tweed princeton clone out of the little bugger. Not that there's anything *wrong* with that, just typing it makes me think 't was a good plan, don't give up on it now...

Anyway, any hints or tips you'd care to share would be greatly appreciated.

Thanks!

Edit: Noob mistake. Epic fail?! I only just noticed that there's like 24 pages to this thread going right up to the present day and I may need extensive review of the other 23 pages before I start cutting traces. But I might anyway. We'll see...

 

[rock_mumbles]

...

Anyway, any hints or tips you'd care to share would be greatly appreciated.

Thanks!

...

Here is a schematic of the modification I discussed above, it's similar to Deafelectromark's mod except I wanted to re-voice the preamp, replace the tone control with a mid-cut tone control and instead of cutting the traces to the volume pot I pulled it from the pcb (be careful if you aren't familiar with pulling components or you'll end up with a damaged pcb)

http://rh-tech.org/public/Crate_v5_Framing-Leah.jpeg

If you want to keep the stock tone control only remove R15, R27 and R7 (I just cut R7 out) from between the two stages. The volume control input (clockwise lug) connects to R15 where it connects to R29, the volume control wiper connects to R15/R27 junction, the volume control ground connects to the ground via on R27.

 

[vinyl_key]

Thanks for the info!

Got my Weber AlNiCo Sig10s in the mail today, sounds much better! Can't wait till the speaker gets fully broken in. Now all that's left is to get the tone circuit to my liking.

 

[Maarten Aerts]

Found this thread again today.
signed in to share my results with the V5.
(Intro: played bass for 35 + years and home guitar, but recently tried to play guitar in a band because i got this amazing Epiphone dot studio es335. And it's fun to rock.)

Also bought the crate v5 about six months ago, and found the modding fora....

The mods described here were way to scary :)
I instead did the following, combined from other fora:
Changed the speaker with a Celestion tube 10.
Changed the tubes:
1 x JJ EL84 / 6BQ5 Matched (TF-0987)
1 x JJ 12AX7 / ECC83S (TF-3645) (also tried others, not nice)
Replaced R17 with a 150watt 5 ohm resistor because the bass distorted ugly .

Loved the sound, wished it could get louder to play on stage.Use it every day at home.

The amazing thing is, my marshall jcm900 4501, was always failing when played on higher volume.
The store were i bought it couldn't find the problem, so i kept in as a home practice amp. (to shy to make a big noise about warranty those days)
On low volume it was exellent, but totally unreliable for stage.

And now i finaly had dared to solder on an actual tube amp (R17)- i had the courage to open up the marshall and found out that the pins of the things the tubes go into weren't soldered right.
If really hot, they would lose contact....
Now a have my big amp again and a really nice little V5, thanks to these fora.
love it with its cleanish blues tone and distortion with a carl martin pedal.

And after re-reading all these pages i think i will do the no-op amp mod.
I understand a lot more now :)

Hope i won't spoil it :)

 

[Maarten Aerts]

Since the Crate was to have more output with 16 ohm, i put some input-jacks together to make plug 2 x 8 ohm speakers out, and 16 ohm in.

Tried the celestion of the marshal with the internal tube 10 (crate), it is amazing, so loud! With the 335studio it made the tonepot usefull, jazz, blues.Pedals worked great.
Way to loud for home-use. but full sound.
With my 10" swr-basscab it was also really loud, and a nice sound, but not as much big warm open in the lows.
So i need a 12" cab with 75/100 watt celestion G12 and the jacks wired for 16 ohm, no need for soldering. (A Jensen would be to much mid-high i think)
Thanks again for the valuable info :)

Back to playing now

 

[cebreez]

Hello All!! My name is Terry Smith.... I am a new member to this forum but I've been pouring over it for weeks. Have had my Crate V5 for at least as long as this thread has been up and it has actually seen very little use since I regularly play through a Peavey Classic 30 1x12 even when I practice. Though lately I've wanted to have a more portable setup when away from home so I got the old Crate back out in hopes of modding it a bit. This is a great thread and jim p you are my hero.... BUT!! Here is my quandary.... I want to keep the op-amp.... Round out the tone.... and increase the headroom. I've liked some of the mods that move the volume pot and deal with the tone knob... I know Im behind but (why?) would we have the tone controlled by the op-amp to start with...? Would it not serve better after the op-amp......? If this all sounds confusing it is because I am very confused!... (and going blind :) ) I actually found an old 10" speaker from an Alesis Wildfire I had laying around... It fit after some coaxing but made a huge difference in tone and headroom. Now I am ready for new tubes and whatever mods you fellas deem absolutely necessary to capture of little more of that Fender magic. Any help would be GREATLY appreciated.

P.S. Im not scared to mod anything. Just want to make sure its worth it in the end.

Thanks
Terry

 

[cebreez]

Is this thread dead? HELLOOOO!!!