Crate V5 mods... anyone?

[Christopher Whitlow]

Another way to modify the amp would be to use the tone pot for a volume pot and the volume pot for a gain pot. This involves no cuts just jumpers and removing components with one being replaced (C24)
1) Remove PCB from chassis
2) Remove R13 C26 C24( to replace with 47nf for more bass or keep as is if you wish) C6 C5 C4 and R27
3) Replace C24 with a 47nf
4) Jumper junction of C6 C5 and CW2 (tone pot) to junction of R27 and R15
That’s it now the volume pot will control the gain of 2nd stage op amp for overdrive and the tone pot will control the volume.

I introduced myself a moment ago in the newbie section.
Got this amp free on a trade with an Emminence Legend and JJ tubes. Really want to do this simple mod first, has anyone completed it yet? This is my first tube amp and it was free so what the heck right?
I only have one question, would a 12aT7 work for me to lower gain a tad? I just want a tad more headroom with a bit less gain. The loss of tone control doesnt really bother me, thats why I put nice CTS pots and treble bleeds in my guitars and my pedals all have tone knobs!
Jim and the others... wow! great info thanks so much for posting all the replies!

[tunghaichuan***]

I only have one question, would a 12aT7 work for me to lower gain a tad? I just want a tad more headroom with a bit less gain.

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.

[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]

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]

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]

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 :

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