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Tuning a V5?


jrcorp

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I recently bought a Crate V5 from GC, new on clearance for $56 before tax. The amp is not working as it's missing the main fuse and cap, but I spent the extra cash for an extended warranty in case something goes wrong. Now that I think of it, that probably means I shouldn't touch anything... darn.

 

I researched my options for low-watt cheap tube combos, and I realize this amp is far from the best, but for about $60 I couldn't pass up an opportunity for (hopefully) tube sound.

 

Reviews express that with new tubes and speaker, the sound improves greatly and becomes at least palatable (sp). In another thread, Verne Andru advised me on my purchase; I read through his [build] thread for a Palomino V8. I'm hoping tha I can achieve even a little of what he's done with that amp, adapting it to my V5.

 

Before it's even operating, as I'm at work, I'm considering my first steps. As I'm a noob in amp repair, I want to start simple and see where I end up. First off, I want to pick up new tubes and probably a new speaker. Being thrifty, I don't want to go crazy on either. I'm looking for an 8 ohm 10" speaker, and one EL84 and one 12AX7 (or better alternative).

 

Verne did his research and decided on a Weber Silver 10 with an Alnico magnet. After researching a bit myself, I think an Alnico would be ideal, but I'm open to ceramics. I want to be able to achieve a nice clean sound at relatively high volume, and I would love as smooth a distortion as possible. As for tubes, it seems that a 12AT7 is the best option, unless I could get more headroom out of something else?

 

I would love to get some ideas - certain models, brands, whatever. A secondhand speaker would be great too to save some cash, so please let me know if you have anything.

 

Thanks! I'll get some pictures and links up later on.

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So let me understand this.....they sold you an extended warranty for an amp that doesn't work?

 

I wish I could give you information how to fix it, but honestly I don't have a clue. As far as speakers go, AlNiCo will have a fuller, more pleasant sound; however the price raises substantially. I can't honestly say that I have really listened to 10" speakers, but there are a ton of great sounding 12" ceramics. I think if you stick with Weber you will get a great speaker (both on terms of sound and quality). Have you looked into the offerings from Eminence?

 

For tubes, I have had really good luck with the Ruby 12AX7 AC7 and the Preferred Series 7025 from thetubestore.com, also the Tung-Sol RI 12AX7 has been good for me too. For power tubes I have been looking at the TAD EL84, but keep in mind it has thicker glass than the typical EL84 so it might not fit in your amp. Right now I am using JJ EL84s, which were in the amp when I bought it, and they sound pretty good. I am not a fan of JJ tubes, I prefer other manufacturers, that is just my personal opinion though. The other EL84 I have been looking at is the Electro-Harmonix EL84, other than those nothing else has really caught my eye. The reason I am interested in the TAD is solely based off the experience I have had with their other power tubes, which I absolutely loved!

 

EDIT: If you are looking for a low gain tube for increased head room, I would look at the Jan-Philips 5751. It is a great tube, that is very musical! If you have your eyes set on a 12AT7, I have a NOS Jan-Philips 12AT7 that I would sell you. Just let me know if you want try the 12AT7 that I have.

 

Cole

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Thanks a lot, I appreciate the advice. Fixing the amp as far as I can tell is a matter of getting a fuse in with a cap to hold it, no big deal. I'll move on that after work, fire it up and see what I think. I'm already shopping around for the tubes and speaker. I would love an Alnico but I'll probably go with a ceramic unless I find something cheap. I have no problem picking up an affordable quality speaker as it's the first I've replaced and will be an improvement anyway.

 

For tubes, unless something changes my mind I want to try a 12AT7. I don't understand tubes well, but I have an idea of decent brands. I don't get power tubes at all - it seems like they can be replaced with other types? If one sounds different from another, that would help. I'm also confused because I've seen the JJ name thrown around a lot and assumed they were commonly used, quality products. But since I've been on the forum I wonder. I also get the idea that older stuff is usually better and more expensive?

 

If anyone knows of a sort of intro to tubes thread, I would be grateful. I'll search later on.

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Thanks a lot, I appreciate the advice. Fixing the amp as far as I can tell is a matter of getting a fuse in with a cap to hold it, no big deal. I'll move on that after work, fire it up and see what I think. I'm already shopping around for the tubes and speaker. I would love an Alnico but I'll probably go with a ceramic unless I find something cheap. I have no problem picking up an affordable quality speaker as it's the first I've replaced and will be an improvement anyway.


For tubes, unless something changes my mind I want to try a 12AT7. I don't understand tubes well, but I have an idea of decent brands. I don't get power tubes at all - it seems like they can be replaced with other types? If one sounds different from another, that would help. I'm also confused because I've seen the JJ name thrown around a lot and assumed they were commonly used, quality products. But since I've been on the forum I wonder. I also get the idea that older stuff is usually better and more expensive?


If anyone knows of a sort of intro to tubes thread, I would be grateful. I'll search later on.

 

 

Just to let you know it is the preamp tubes that you can mix and match, with some degree. The amp's design was designed for specific preamp tubes, and there are some that shouldn't be placed in the circuitry (depends solely on the schematics of the amp) As far as preamp tubes that are safe in a 12AX7 spot, would be 12AX7, 12AT7, 5751, 7025. The power amp tubes need to be biased, they are the trickier of the two. Fortunately for you, all you need is one power tube and one preamp tube. This will make things a lot easier for you. In amps that have more than one power tube, you would want matched tubes (which are done in multiples of 2). With your setup, you will have a lot more flexibility (and money) to try out different tubes.

 

This might explain biasing power tubes to you.

http://tubedepot.com/whisbipo.html

 

As far as the variance in 12AX7 to 12AT7 to 5751 is all about how much gain is provided by the tube. I want to say that the 12AT7 is roughly 60% the amount of a gain a 12AX7 would have, and a 5751 is around 70% of a 12AX7. I was trying to find the information on it, but was coming up short on what I was looking for.

 

Actually, just found it.... Just click on the 12AX7 tube, and it will show what tubes you could use in your preamp section and how much of a difference in gain you will get.

http://thetubestore.com/gainfactor.html

 

Hopefully this is helpful...

 

Cole

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Also, if your amp is an EL84 amp, that is the only tube you can use in the power section. There are amps that can take a multitude of power tubes, but the circuitry allows this as well as the transformers in the amp.

 

The most common thing I see in higher wattage amps is a switch that allows to switch from EL34 and 6L6 tubes, but there are amps like Mesa/BOOGIE Rectifier Road King that allows you to mix and match power tubes (granted it is a very in depth circuitry), also the THD Univalve and its bigger brothers can use a multitude of tubes like KT88, EL34, 6L6, KT66, 6550....but like I already stated, it was designed to work this way NOT every amp does this.

 

As far as brands of tubes, it is very subjective. I don't mind JJ power tubes, but I hate their preamp tubes. It really is a matter of opinion, and I urge you to try them, as you might like them. The JJ preamp tubes work really well in very bright and middy amps, because IMO they sound very dull which kind of cancels the two out. As far as brands I like, I really dig Ruby. Do keep in mind that Ruby, Groove Tubes, and TAD are just relabeled tubes that come from companies like Svetlana, New Sensor, JJ/Tesla and Chinese factories; but have been chosen to meet their quality controls. I am much more fond of Ruby & TAD than Groove Tubes because they are cheaper than Groove Tubes, and are pretty much the same tubes. You do have to discern where they are made when choosing Ruby, TAD or Groove Tubes to know what you are getting.

 

Places like www.thetubestore.com have some great reviews on the power tubes and preamp tubes that I would suggest you read.

 

Cole

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Aha. I do remember when I bought 12AX7's for my Vox that Groove Tubes made in Russia were the knew to look for, and had a certain model number or something. I'll have to look around a bit, including on that site. I might even buy a 12AT7 for my Vox to see if it makes a difference. Thanks again!

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Smooth distortion isnt really a dimed low watted amps forte, but an alnico might get you closer. Weber makes some signature series alnicos that are usually pretty cheap, as in around 40 bucks new. I havent tried any of the 10s but i love the 12S sig that i got, but not so much with the 8 smooth cone.

 

The speakers i tried in mine were the stock made-from-a-styrofoam-cup one which i beleieve ive told you repeatedly how bad it is, a celestion vintage 10 out of a prosonic and a jensen c10q. I love the Vintage 10 and kept it, the jensen sounded brighter and gave the amp a sort of fenderish clang which is not my style. Like i said before the jensen is just lying around so you can have it for $20 plus some shipping if you like.

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Thanks a lot, I appreciate it. I browsed a few websites this morning and read about different speakers - Weber, Celestion, and Jensen - to see what's available and come up with an idea of what I want. You're right about Weber, this is what I'd probably try. My only concern is the dimensions - 5 3/8" deep seems potentially too large to fit in the cabinet. I may do some measuring to double-check. I read about the C10Q - I had thought it wouldn't be right or as good an option, but it seems like it may work out well or suit my style.

 

Today my problem is tracking down a suitable fuse. I went to the local Radio Shack and looked through what they have, but there was no 1.6 amp 125 volt fuse, which is what the schematic calls for. I asked the representative if he had an idea of whether anything else would work, but he didn't have a clue. I called GC to ask the same (I bought it there after all), but couldn't quite lead up to it before the guy said he wouldn't know. I'm calling back in a bit to get someone more knowledgeable, but I can't stand when people aren't qualified for their jobs. How many electrical engineers are out of work right now? Anyhow, if anyone has suggestions on whether a similar fuse would work here, please let me know as I'm dying to get this fired up.

 

If I can't find a cap or rig something up for the fuse holder, I may just spend the extra few dollars and buy a new holder. I figure it should be easy as pie to put in.

 

I looked around and read through everything on the Tube Store, so I feel a little better there (thanks Cole!). I love the variety of stuff they carry, it makes me want to try one of each. I haven't quite decided what I want as far as tubes, but I think I'll probably go for an EH or JJ EL84. For preamp, I'm not sure if I'll stick with an AX7 or move to an AT7. Would it be bad to consider an AY7? My concern would be a much lower volume, but without knowing tube amps well I really want to make sure I have a decent amount of clean headroom. Let me know if my terminology is off, haha. Maybe I'll get brave and order some different stuff.

 

EDIT: Antihero - I tried sending you a PM regarding your speaker. I'd like to buy it and try it out. Thanks!

Cole - could you PM me or post here giving a price for the 12AT7? Could be a good option.

Verne - I'm curious about the Celestion from the V8. I'd be interested in buying it, but I'm skeptical as it came stock in an amp, especially one similar to what I have. Let me know anything you can about it? A PM would be awesome.

 

Also, I stumbled upon a post on CL today for a 2 x 12 cab with Celestions for $50. Sure it could have been a scam... called the number a few hours later, no answer, and the post is gone. DARN!

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Thanks a lot, I appreciate it. I browsed a few websites this morning and read about different speakers - Weber, Celestion, and Jensen - to see what's available and come up with an idea of what I want. You're right about Weber,
is what I'd probably try. My only concern is the dimensions - 5 3/8" deep seems potentially too large to fit in the cabinet. I may do some measuring to double-check. I read about the C10Q - I had thought it wouldn't be right or as good an option, but it seems like it may work out well or suit my style.


Today my problem is tracking down a suitable fuse. I went to the local Radio Shack and looked through what they have, but there was no 1.6 amp 125 volt fuse, which is what the schematic calls for. I asked the representative if he had an idea of whether anything else would work, but he didn't have a clue. I called GC to ask the same (I bought it there after all), but couldn't quite lead up to it before the guy said he wouldn't know. I'm calling back in a bit to get someone more knowledgeable, but I can't stand when people aren't qualified for their jobs. How many electrical engineers are out of work right now? Anyhow, if anyone has suggestions on whether a similar fuse would work here, please let me know as I'm dying to get this fired up.


If I can't find a cap or rig something up for the fuse holder, I may just spend the extra few dollars and buy a new holder. I figure it should be easy as pie to put in.


I looked around and read through everything on the Tube Store, so I feel a little better there (thanks Cole!). I love the variety of stuff they carry, it makes me want to try one of each. I haven't quite decided what I want as far as tubes, but I think I'll probably go for an EH or JJ EL84. For preamp, I'm not sure if I'll stick with an AX7 or move to an AT7. Would it be bad to consider an AY7? My concern would be a much lower volume, but without knowing tube amps well I really want to make sure I have a decent amount of clean headroom. Let me know if my terminology is off, haha. Maybe I'll get brave and order some different stuff.


EDIT:
Antihero
- I tried sending you a PM regarding your speaker. I'd like to buy it and try it out. Thanks!

Cole
- could you PM me or post here giving a price for the 12AT7? Could be a good option.

Verne
- I'm curious about the Celestion from the V8. I'd be interested in buying it, but I'm skeptical as it came stock in an amp, especially one similar to what I have. Let me know anything you can about it? A PM would be awesome.


Also, I stumbled upon a post on CL today for a 2 x 12 cab with Celestions for $50. Sure it could have been a scam... called the number a few hours later, no answer, and the post is gone. DARN!

 

 

I just took some measurements of mine and you have exactly 4 5/8 inches so the weber might fit if its a very accurate measurement. The celestion i told you about barely fits, the magnet is actually touching the chassis.

 

I didnt get a PM from you, try sending t again.

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I just took some measurements of mine and you have exactly 4 5/8 inches so the weber might fit if its a very accurate measurement. The celestion i told you about barely fits, the magnet is actually touching the chassis.


I didnt get a PM from you, try sending t again.

 

 

Thanks for measuring! The Jensen should fit without trouble - their website shows it as being about 3 5/8" deep. If I end up with something that doesn't work, I could try it in another amp I have.

 

PM sent!

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- replacing the fuse holder. Linking to see if anyone will see it and respond here, and as it's related.

 

 

So you are just missing the cap to hold the fuse in? Contact Crate and im sure they either have one to sell you or know where you can get one. It cant cost more than a couple bucks.

 

As for rigging up a new fuse holder, i generally recommend against working on an amp if you dont really know what you are doing, there is some lethal voltages still in the amp.

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Well not to be difficult, but I was able to replace the fuse holder and get the amp running. It was a pain to get the old one out, and I had to file the hole in order for the new holder to fit, but after a little work and soldering, she's in good order. I like the fuse holder I got from Radio Shack too - it's a little bigger than the old one as it holds larger fuses, but the way the cap opens and the fuse is replaced is neat and easy compared to even a screw-in cap. Looking at the old holder, I can't even tell what kind of cap would have been there as there's no visible threads, notches, etc.

 

It's still opened up right now... my only concern is that my soldering isn't top notch, but everything is connected well that I can see. I also haven't wrapped the exposed wire right, I'm not sure that I could shrink wrap the connections without redoing everything so it'll be taped for now. But I'm going to button it up and plug in, I'm pretty darn excited to see how it sounds. Even if it's a terrible tube amp, it's my first!

 

Can't wait to get some parts together to upgrade, too. I'm working with a few generous members here. Thanks all for your help, I'll keep this updated.

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Well not to be difficult, but I was able to replace the fuse holder and get the amp running. It was a pain to get the old one out, and I had to file the hole in order for the new holder to fit, but after a little work and soldering, she's in good order. I like the fuse holder I got from Radio Shack too - it's a little bigger than the old one as it holds larger fuses, but the way the cap opens and the fuse is replaced is neat and easy compared to even a screw-in cap. Looking at the old holder, I can't even tell what kind of cap would have been there as there's no visible threads, notches, etc.


It's still opened up right now... my only concern is that my soldering isn't top notch, but everything is connected well that I can see. I also haven't wrapped the exposed wire right, I'm not sure that I could shrink wrap the connections without redoing everything so it'll be taped for now. But I'm going to button it up and plug in, I'm pretty darn excited to see how it sounds. Even if it's a terrible tube amp, it's my first!


Can't wait to get some parts together to upgrade, too. I'm working with a few generous members here. Thanks all for your help, I'll keep this updated.

 

 

Well, cool then. Im sorry i cant help more with the electrical stuff, but hopefully my jensen speaker will get you the tone you want.

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As far as your soldering goes....the shinier the solder is after you make the joint the better. If the solder is dull, it means one of the components wasn't heated up enough. You also want to never blow on a solder joint to cool it.

 

Shiny solder joints are your friends :thu:

 

Cole

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Thanks for the encouragement guys. I remember shiny solder, so hopefully I got it right.

 

The amp sounds... okay. I'll be content practicng with it, and I had fun playing around, but I thought it would sound better by my low standards. The iffy, crunchy distortion kicks in so early - I want to say at least by 12 on the volume. Tone is funky, I forget how Verne explained it but he was right. Full-on treble is at 12, below is gradually no highs, and above is similar but without cutting as much tone, maybe saving mids? This is. By memory. I played with my Washburn WI 24, which has a Duncan JB in bridge, Jazz in neck, and coil split for each. I had fun cranking it with the neck single coil, bridge single coil, and bridge full pickup, mostly playing bluesy stuff, a little Hendrix, that Dick Dale surf song, etc.

 

I will say that I had fun playing as I got some kind of drive out of it. I got a real old school, classic kind of vibe that came with a driven tube sound. But I think that's mostly because this is my first tube experience. Unfortunately, I was not able to achieve a clean sound at a decent volume. I came close, but it would be a matter of my playing itself determining the clean/dirt - some dirt came through in chords etc.

 

As I said, I will use the amp for practice and fun as is. I have a hollowbody that might sound decent, as well as an acoustic soundhole pickup. I'm wondering if they'll come through any more clean; I think the pickups I played are relatively hot. I would like to take away some of the gain, add all the clean headroom I can, replace the speaker to see what that achieves, and maybe experiment a bit. A normal tone knob would be nice, and the clean headroom to throw effects in would be great.

 

I'll continue reading up on mod ideas and brainstorming, buy a few parts to replace, and see how I feel. If I get brave, maybe I'll try some clipping and soldering. Working on the amp was fun.

 

Thanks again, bless anyone with the patience to read this.

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...I'll continue reading up on mod ideas and brainstorming, buy a few parts to replace, and see how I feel. If I get brave, maybe I'll try some clipping and soldering. Working on the amp was fun.


Thanks again, bless anyone with the patience to read this.

 

Bypassing the opamp is a big mod to improve this amp, they messed up on the gain/volume. Then move the gain to after the first tube stage, mod the tone contorl (I used Marshall 18w normal channel), and fix the screen resistor location (I also added a master volume), and it worked much, much better. In addition to the fret.net site http://www.thefret.net/showthread.ph...mods...-anyone , there is a little discussion on sewatt regarding this amp http://sewatt.com/crate-mods

 

v5inputmod.jpgv5marshalltonemod.jpgv5el84modsmv.jpg

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Thanks for the encouragement guys. I remember shiny solder, so hopefully I got it right.


The amp sounds... okay. I'll be content practicng with it, and I had fun playing around, but I thought it would sound better by my low standards. The iffy, crunchy distortion kicks in so early - I want to say at least by 12 on the volume. Tone is funky, I forget how Verne explained it but he was right. Full-on treble is at 12, below is gradually no highs, and above is similar but without cutting as much tone, maybe saving mids? This is. By memory. I played with my Washburn WI 24, which has a Duncan JB in bridge, Jazz in neck, and coil split for each. I had fun cranking it with the neck single coil, bridge single coil, and bridge full pickup, mostly playing bluesy stuff, a little Hendrix, that Dick Dale surf song, etc.


I will say that I had fun playing as I got some kind of drive out of it. I got a real old school, classic kind of vibe that came with a driven tube sound. But I think that's mostly because this is my first tube experience. Unfortunately, I was not able to achieve a clean sound at a decent volume. I came close, but it would be a matter of my playing itself determining the clean/dirt - some dirt came through in chords etc.


As I said, I will use the amp for practice and fun as is. I have a hollowbody that might sound decent, as well as an acoustic soundhole pickup. I'm wondering if they'll come through any more clean; I think the pickups I played are relatively hot. I would like to take away some of the gain, add all the clean headroom I can, replace the speaker to see what that achieves, and maybe experiment a bit. A normal tone knob would be nice, and the clean headroom to throw effects in would be great.


I'll continue reading up on mod ideas and brainstorming, buy a few parts to replace, and see how I feel. If I get brave, maybe I'll try some clipping and soldering. Working on the amp was fun.


Thanks again, bless anyone with the patience to read this.

 

 

Low watt amps will never give you much in the way of clean headroom, they're designed to break up at lower volumes so you dont blow your eardrums out.

 

You can try a 12at7 or other low gain preamp tube and use low output pickups but remember these things are made to overdrive.

 

Tone knob is really funky, i usually run it at about 3 o'clock myself.

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Thanks for the tips! I'll have to do some more reading now; I started on the fret.net thread today at work. I appreciate the recommended mods from experience and the schematics, but unfortunately I think they may be just over my head for me to feel comfortable trying to do the work. I feel as though I should try to find some reading material or other resource for learning electrical circuits, as I barely have a basic understanding. I remember going over this stuff in Physics class but didn't do particularly well with the math of it at the time. The terminology is also a little foreign to me - the term "screen resistor" is beyond me.

 

What do you mean by tone control from a Marshall 18w normal channel? Unfortunately I don't know my classic tube amps either! I suppose I am many types of a noob. If it means anything, I'm more than willing to learn. Hope I'm not trying anyone's patience here.

 

Again, thanks for all the info.

 

Edit: Anti, you posted as I was typing. I guess that's kind of unfortunate, as I would love to get a cleaner sound. At the very least, hopefully I can improve the distortion, as it's about halfway between okay and unbearable as is. I have a 12AT7 along with a few other tubes on the way, so I'll look forward to trying them out. Based on reading other threads, it seems as though the circuit should be modded some to better accommodate different tubes? I hope I'll be able to play around without more modding right away.

 

As for pickups, I don't think the SD JB and Jazz I have installed are low enough output, but when compared to the DiMarzios I'm throwing in my project guitar they're probably much quieter. So I hope my hollowbody's pickups work out well, or I may be waiting for something new to get a cleaner sound. I have other amps, so it's not a big deal.

 

The tone knob is funky, but I played around and got a few okay tones for different pickups. This is something I'll probably try to change in the future though, hopefully to more of a conventional setup.

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Thanks for the tips! I'll have to do some more reading now; I started on the fret.net thread today at work. I appreciate the recommended mods from experience and the schematics, but unfortunately I think they may be just over my head for me to feel comfortable trying to do the work. I feel as though I should try to find some reading material or other resource for learning electrical circuits, as I barely have a basic understanding. I remember going over this stuff in Physics class but didn't do particularly well with the math of it at the time. The terminology is also a little foreign to me - the term "screen resistor" is beyond me.


What do you mean by tone control from a Marshall 18w normal channel? Unfortunately I don't know my classic tube amps either! I suppose I am many types of a noob. If it means anything, I'm more than willing to learn. Hope I'm not trying anyone's patience here.


Again, thanks for all the info.

 

 

Try a new speaker before getting to much into modding it.

 

Im serious that speaker is the worst thing ever, wait until you pull it out, the cone looks like those red plastic cups you buy only black.

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Haha well I can't wait to change anything and see what comes of it. Without understanding much of the electronics at all, the opamp in general seems to be a huge hindrance to the sound just going by what others have said about where it's placed, what it's used for, etc. Regardless, I'm not clipping or soldering anything until I've tried swapping out the speaker and tubes. I would really like to come up with some kind of cab to see if that would help out any, too. Maybe I could somehow run my Fender 2x12's speakers off of it, I'll have to check the resistance.

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Bypassing the opamp is a big mod to improve this amp, they messed up on the gain/volume. Then move the gain to after the first tube stage, mod the tone contorl (I used Marshall 18w normal channel), and fix the screen resistor location (I also added a master volume), and it worked much, much better. In addition to the fret.net site
http://www.thefret.net/showthread.ph...mods...-anyone
, there is a little discussion on sewatt regarding this amp
http://sewatt.com/crate-mods


v5inputmod.jpg

v5marshalltonemod.jpg

v5el84modsmv.jpg

 

I've not had a chance to muck with a V5, so take this with a grain of salt. I did A/B the V5 and V8 schematics and - on paper at least - the only change AFAIK is removing the FX send/receive and the Master Volume control. This means you're controlling the volume exclusively with what was designed to be the Gain pot.

 

On the V8 I do find leaving the volume wide open tends to lead to a raspier and nastier tone, so I usually keep it around 8 [if you consider it has a taper from 0 to 10]. Taking that pot out of the circuit does 2 things - it opens that connection to 10, plus it takes the pots resistance out of the equation which is really like having it on 12. If it's nasty on 10 I can only imagine how horrible it would sound on 12!

 

This leads into the clean headroom of the amp. The benefits of having that dual opamp first in the signal chain is [with a TLE2072ACP Excalibur] your first preamp stage will be pristine clean. The stock TL072 [or whatever it is] isn't bad, but still has a fairly high noise floor so the opamp will add some unwanted's to the tone. Removing the opamps entirely means you're relying on 1/2 of the 12A?7 preamp tube to perform your first stage preamping. Tubes, at that part of the signal chain, will always be noisier than opamps. The second 1/2 of the 12A?7 performs gain makeup after the tonestack [and effects loop if present].

 

The point of this is that I get really nice clean headroom on my V8 with the opamps/gain/volume combination. I think you can do the same on the V5 by upgrading the opamp, dropping the preamp tube down to a 12AT7 and putting a Master Volume control between the tone-stack and the second 1/2 of the 12AT7 just as it is on the V8 schematic. Might as well put the FX loop back in while you're there since I find it adds so much versatility to the amp.

 

My 2 cents FWIW.

 

On the speaker - mine is a 10" ceramic Celestion made with paper, not plastic. I read somewhere that someone emailed Celestion about it and it's one of their standard 10" speakers. You could email them for more info. It's an okay speaker, and certainly heads and shoulders better than what came in the V5, but I like the tone of an Alnico better for what I do.

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Thanks for the help, Verne. I was almost ready to ask someone to help me out, though I wanted to try and compare schematics myself and see what I think. So you'd suggest that beyond the simple stuff - tubes and speaker - I should try upgrading the opamp and adding a master volume control into the right part of the circuit. I don't know what difference it makes, but I would have no qualms about trying to add a concentric knob. I've done push-pulls, but I don't think those would help me much here. I'd like to try to squeeze what I can out of the small chassis and few knobs - if I go crazy and want to add more, I could drill or whatever.

 

Tubes and speaker should be on the way soon, and depending on how I feel I'll probably order an Alnico from Weber. Then it's on to the real mods. Thanks again.

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... Then it's on to the real mods. Thanks again.

 

 

Great thing about mods, you get to decide what you want out of the amp, and change it until it works for you. Some form of gain/volume within the tube section is manditory. And for max clean headroom and volume, get a EL84M or the russian eq. -EV tube, it is a 14w tube, bias at 100% at idle, and you will get the max possible clean headroom, volume, out of the amp. It is going to be the power tube that limits your clean volume (and speaker, get as efficient as possible)... The screen resistor should be moved to the correct position also, R18. You can play with dropping resistor values and run the preamp tubes at higher voltage but that will be so slight a change as not likely detected. I also think a tone control mod is a huge help! Fondue (Jim P) is an EE that did much of the work on the v5 mods, here is a comment he made on sewatt, http://sewatt.com/node/19649#comment-192267

"...On the op amp with the values of capacitors used on its input it limits the bass response and boosts the treble for the tone control. The tone control can only cut the treble so to have boost you need to do it before the tone control. Without the op amp the easiest way is to change the value of the cathode bypass cap of the first triode. Also if you plan on overdriving the amp with a pedal it will sound better with the treble boost on the first triode..."

 

I am also not sure if the v8 is the same as early v508 models, looking at that schematic, I see huge differences in the EL84 and power rail, http://www.sewatt.com/files/sewatt/482SCH_A.pdf . I think it was because the PT was way low on voltage, shows EL84 biased with 100R, WOW... And they didn't even use a screen resistor, but at least hooked the screens up in the correct power rail position, after the dropping resistor power rail node. I would really need to look at a true v8 schematic before I could make any comments specific to it. What is the EL84 plate voltage on the v8?

 

There was also a comment that the earlier models ran the opamp at +7/-7 volts, whereas the new v5 is =14.4/-14.4, that would double the opamp head room. Where does the opamp on the v8 run?

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