Researching an Amp build (Update: Made my decision)

Volitions Advocate

Senior member
Messages
1,239
Hi all.  It's been awhile (I say that every time I post)

You know it's amazing what a music degree will do to your activity in music.  I have barely played my guitar at all the last 5 years, and it's about time I stop being depressed, because we all know not playing guitar is a depressing state of affairs.

So.. now that I'm older and wiser (lol) and know a few more things than I used to, it's time to revisit my rig from back in the day. 

Once upon a time I was a foolish young man (haha.. once upon a time) and I went and bought myself the kind of amps to match the volume of the other young foolish man I was jamming with.  So I paired 2 half stacks together in stereo, one 100W tube amp and one 350W SS amp.  Even gigged with them a couple times.  I don't want to do that ever again.

I had been running a Crate GT3500H on the solid state side and a Rivera Knucklehead Reverb 100 for tubes.  I sold the Crate a few years ago to make some payments, and I have this irrational urge to buy another one because they're discontinued and cheap used, I also still have the 4x12 for it.  But I wont be doing that.

I still have the KR100, and I love that amp.  I can also flip a few switches and pull it all the way down to 25 watts if I want, but why should I haul around that monster if I'm not going to use it all?  I've been considering selling it on and off for years...

So here's my plan.  I still have my old Crate combo amp (GX212, 120 Watts SS) and it has been a workhorse for years for me.  I really like the pairing of a SS and Tube amp. So I'm going to continue the model, just without the 4x12 cabs.  The crate needs a new cabinet. it got busted up when I mailed it from Toronto to Calgary a few years back and with the way Crate built them, the speakers are staggered. It helps with lessening the width by 3 or 4 inches, but I think I'd like to set it up a little more spaced out like a Roland JC120, with a straight cab instead of slightly slanted, because I plan to use it vertically.  I will probably also look into getting some new speakers for it.  As much as I like Crate's solid state stuff, much to the derision of most players, I do think their speakers aren't super great.  Maybe I"ll do the predictable thing and pop in a couple of Vintage 30s, unless I have the opportunity to research some different loudspeakers.

With all that in mind. I want to make a 2x12 combo tube amp to go with it.  Something that is similar to my Rivera.  Wattage is something I'm not really sure about, maybe 35 watts?  I want this thing to break up nicely without all the hearing damage.
I'd like to be able to switch it down to as low as 5 or 7 watts, and I plan to make it midi switchable, or at the very least accept a footswitch with a TRS cable.  3 channels.  Clean, Dirty, and Just Awful. And reverb.

I have the schematics for the original Knucklehead with Paul Rivera's stamp on them, but they're dated from 1992 and I know he's made modifications since then. My model was probably built in 2004 or 2005 I think.

The big criticism I have with the Knucklehead is that the 2nd and 3rd channels are the same channel, with the 3rd having a bit more gain stages.  My perfect amp would be the Knuckleheads' clean and dirty channels, with the 3rd channel the same as the Knucklehead-Tre's distortion channel (if you guys are at all familiar with the Rivera lineup, the K-Tre is is an unbelieveable beast, but a one trick pony, which is the only reason I didn't buy it over the full Knucklehead)

Now.. I could go to a guy who could probably help me build this thing straight from Paul Rivera's schematics, but would probably be easier (and lets face it, more practical with a better result) would be to find a kit that closely resembles what I'm looking for, and modify it as needed.

A buddy of mine just bought a Carvin V3M and I must say it is one of the best sounding little amps I have ever heard.  I would probably buy one if I wasn't trying to do more of my own thing and in a combo amp.

Trevor, you still around?  I remember you being the guy-in-the-know about this stuff.

Some links for the crap I've been blabbing about:

Knucklehead top: http://www.rivera.com/product/heads/kr7-mick-thomson-signature/
(this is a signature model, I can't find the original model on their site anymore)

K-Tre: http://www.rivera.com/product/heads/knucklehead-tre-reverb/

Crate GX212: http://www.manualslib.com/manual/33038/Crate-Gx212.html

Carvin V3M: http://www.carvinaudio.com/products/v3m
 

Timmsie95

Senior member
Messages
890
I don't know much about building amps, but I like amps and reading, so I read this post  :laughing7:

For refference, I have an Orange Dark Terror (Absolutely love the little thing) which goes from 15 to 7 watts, and it still cleans up nicely. It is a loud thing too... Don't let low wattage fool you into thinking it'll be quieter, because I run it through a single 10" cab (from my Marshall MG Micro Stack) when I'm practising, and it pumps..
I know SS is different, but just thought I'd share.

Also, The Knucklehead is a beautiful amp!
 

ironeddie

Senior member
Messages
108
Hey Man,
It's fun to find you on here!  Look at you at Hero level!  :eek:ccasion14:
Now, I've heard you play before, and you like a fairly thunderous tone.  Have you thought of which tubes you are going to use?  Personally, I like the EL84s - that's what I have in the V3M.  They seem to offer lots of tonal options.  If you're going to be designing your own, it shouldn't be hard to make it so you can use what you like!
 

Volitions Advocate

Senior member
Messages
1,239
Is that you Jake? I didn't know you had a guitar blog, looks about as up to date as my website.

Yeah. I suppose I should have mentioned that.  I'm strongly entrenched in the noisy EL34 camp.

Timmsie, I haven't heard an Orange amp that sucked, that's for sure.  I think what I'm looking to build might fit that Mesa Lone Star type spot.  I've heard metal heads and country/western guys use that amp, both to great effect.  I need something like that, but just a little bit more.... me.

And the knucklehead IS beautiful, thus not having actually sold it yet.  Maybe I coudl sell it state side, let somebody else take advantage of the TP we use for money up here at the moment to get a good deal.  Put that money back into my build.
 

mayfly

Senior member
Messages
8,309
Hey Advoc,

I can't do a long reply at the moment (I'm at work), but there are a few things I can mention:

1 - use EL84s.  They are the most musical tube for guitar amps, mostly because they have some gain of their own.  I believe this helps with the responsiveness of the amp they are put into.  EL34s are just too stiff.  Lack of a feedback loop is good as well.

2 - After that, it's speakers that will really drive your tone.  Pick the speaker that will get you 90% of the way there.  I've always been partial to Eminence, but it's a personal choice.  Do you really want a 2x12 though?  I've always had great results with just a single 12 as a single driver removes all the beaming and other issues inherent with multiple drivers.

3 - Multiple preamp channels are the road to hell.  Complexity, noise, heat, expense, and figuring out your switching will drive you crazy.  That and you'll tweak the circuit so that one channel sounds great, and it will mess up the other ones.  IMHO the better path is a single channel amp that will deliver your 80% tone (the tone you use 80% of the time) then use pedals for the other 20%.

4 - you say there are amps out there that are really close to the sound you like.  Why not get one of those and modify it?

Yours in amps,
Trevor

P.S.  These days I'm using an AxeFX straight into the PA.  Best tone I've ever had.
 

Timmsie95

Senior member
Messages
890
Mayfly said:
P.S.  These days I'm using an AxeFX straight into the PA.  Best tone I've ever had.

Everyone needs to stop talking about their Axe FX and Kemper and all these amazing rack systems... I'm getting serious GAS and I'm reeally tempted to sell my tube heads and 412's...
 

Volitions Advocate

Senior member
Messages
1,239
Mayfly said:
Sage advice & awesomeness.

Man I miss this place.

I remember when you got the AxeFX.  It must be a stellar unit if you haven't switched yet and it's still your forum signature.  I have so many different ways to go about this I have to kind of explore every possibility before I commit to a decision, so thanks for the advice.  And if you ARE going write a bunch more stuff. I'll be reading :)

Was thinking about the 1x12 vs. the 2x12, I'm going to look up what beaming is and have a good think.
Good to know about the tubes too.

I have nothing against digital effects either, in fact my stompbox collection has diminished in recent years in favor of a digital multi effects unit, and I've been working on incorporating my computer directly into the signal chain ala Johnny Greenwood for some more weirdness in the mix.  One of the reasons I was thinking of keeping my base tones really analog. Thus the channels.

Lots to think about.
 

Logrinn

Senior member
Messages
3,597
I have been thinking about new speakers for a while and here are my thoughts.
If I could find a 1x12" that sounded perfect, then all the better. It would be cheaper, smaller, lighter and so on.
But a quick search on the interweb, Youtube and so on and trying out different cabinets for myself, it's pretty obvious that they all sound so different.
And as Mayfly says, such an important and big part of the sound.
Which might be the reason why you see 4x12" cabs with two brands of speakers in them. One pair on the left and the other on the right. Or in a X configuration. Same thing with certain 2x12" cabs.

So, why not have a couple of 1x12" cabs with different models and/or brands of speakers in them - and maybe some open backed and some closed back - and place them to taste? In some venue you might get an excellent sound with cab A on top of cab B, while cab C is on top of cab D to the right. But in another venue you find that you need to change this to get a better sound. Perhaps because of the size of the stage or the way the speakers need to be placed compared to where you stand and plays - and therefore perceives the sound.

And if money were no object you could get more 1x12" cabs. Have 2 cab A's, 2 cab B's, 1 cab C, 1 cab D ... well, you get the general idea.

 

Cagey

Senior member
Messages
24,425
Logrinn said:
So, why not have a couple of 1x12" cabs with different models and/or brands of speakers in them - and maybe some open backed and some closed back - and place them to taste? In some venue you might get an excellent sound with cab A on top of cab B, while cab C is on top of cab D to the right. But in another venue you find that you need to change this to get a better sound. Perhaps because of the size of the stage or the way the speakers need to be placed compared to where you stand and plays - and therefore perceives the sound.

And if money were no object you could get more 1x12" cabs. Have 2 cab A's, 2 cab B's, 1 cab C, 1 cab D ... well, you get the general idea.

I used that philosophy some years back and started building to suit. I got two closed-backs done and decided that wasn't the way to go, but it was partly my design's fault. They ended up too heavy. With the front covers on they weighed ~55lbs ea., If I'd finished with four as originally planned, I'd have 220 lbs of cabinet to move, each taking one trip in/out of wherever. Wrong direction. But, the sound was nice. I put an Emminence Delta Pro 12 (EVM 12L doppleganger) in one, and a Celestion V30 in the other. As you suggested, stacking order and placement changed things, so you had a bit of experimentation to do depending on where you set them up.

This isn't a good picture, but the only one I could find at the moment...
 

Attachments

  • IMG_2611.JPG
    IMG_2611.JPG
    1.7 MB · Views: 469

Logrinn

Senior member
Messages
3,597
Those are some heavy-duty speaker cabinets. I can imagine they weighed quite a lot.
I was thinking more in the lines of already made - and smaller - cabinets like those offered by ENGL, Orange and so on. Using their speakers (often Celestion anyway) in them and changing some, like Eminence or some such, but using the cabinets.

But of course, if you are the woodworking type of guy (that I guess a lot of people here are) then building cabinets could be a good idea. Cheaper too, perhaps?

Except the weight issue, of course ...  :)
 

mayfly

Senior member
Messages
8,309
Some more off the cuff stuff:

1 - Books.  The best books that I could find on tube amp design are the "Ultimate Tone" series by Kevin O'Connor:

http://www.londonpower.com/audio-design-books

Another book that I got a lot from was the original 'pamphlet' version of The Tube Amp book by Aspen Pitman (now out of print).  I've got every edition of this book from the pamphlet all the way up to the monster coffee table book; the pamphlet is the best because it includes articles by Kevin Fisher (Trainwreck) that were removed in subsequent editions.  I learned a lot from those little articles.

Don't bother with the Gerald Weber books.

2 - The London Power site has a bunch of kits as well - they are pretty good for experimenting.  I built and modified several, including Kevin's "standard preamp" and several power amps.

3 - Tube amps over 5 watts need a master volume.  I tried them all and the best one is the post phase splitter dual pot version invented my Kevin Fisher (cribbed from the original Tube Amp Book  :headbang:).  It just happens to work very well in cathode bias amps because you don't need the second set of caps (the pot itself becomes the required 220K bias resistor to ground).  This was one of the secret ingredients in Mayfly amps.

4 - When it comes time for transformers, the best that I could find were good old Hammond Mfg.  I used full bandwidth hi fi output trans and didn't connect the ultra-linear taps.  This gave a lot of very nice lower mids.  Another secret ingredient in Mayflys.  Made in Canada as well (in beautiful Guelph Ontario!  :) ).

5 - you'll end up building more than one, and they will all suck at the beginning.  Because of this don't sweat how things look at the beginning.  When it comes time to make it look nice (inside and out) I recommend going to a local trophy shop and have something engraved there for your front and rear panels.  Cheap and will look great.

6 - The first thing you need to build is a current limiting mains power supply.  You'll find details in this book:
http://www.londonpower.com/audio-design-books/Tonnes-of-Tone.  Kevin calls it "The Mandatory Project".  He's right.

7 - Get your tubes from the tube store in Hamilton.  I've always had good luck with JJs

8 - do you have a set of tools?  good meter?  good oscilloscope?  signal generator? Dummy Load? Nice Iron?  You'll need all of these.

9 - er, probe with one hand  :glasses9:
 

Cagey

Senior member
Messages
24,425
Speaking of signal generators, I've got a nice unit from B&K that goes from 20hz to 200Khz, sine and square wave output, 0, -10, -20 output attenuator. Also, a 100 watt  8 ohm dummy load. I don't anticipate ever using them again. Like new, I'll take $75 for both.
 

ironeddie

Senior member
Messages
108
I wonder when working with signal generators...  Could a guy use a computer with some sound programming software like CSound PD or Max, and just use the output on an interface or just your headphone out?  You can generate squares, triangles, sines, and mess around with amplitude, phase, duty cycle etc. 
 

Cagey

Senior member
Messages
24,425
I think there is; I don't remember why I didn't go that route when I bought the standalone unit.
 

mayfly

Senior member
Messages
8,309
doesn't matter where you get the signal from - just as long as you have signal.
 

Volitions Advocate

Senior member
Messages
1,239
For a signal generator my plan was to use Max, I just need to macguyver a 1/8" cable from my laptop.  Headphones don't work so well because the wires are so thin.

At the moment I have access to pretty crazy oscilloscope, but I plan to build one for myself.  And a bench supply.  I'm building preamps and ADC's right now for my Masters thesis, and I am woefully unprepared.  I would prefer to become an expert (whatever that means) but right now I'm stuck with "just-in-time learning" as one of my advisors puts it.

I think building an amp will help me along in that regard as well.

I've also found this AX84 site.  Anybody checked it out?  Seems full of useful information as well.. since I don't have $500 to spend on the London Power books.
 

Volitions Advocate

Senior member
Messages
1,239
Well I've finally decided what to do after a bit more research.

I know that amp building is an iterative process. I've learned that much from the comments here and reading on the other forums.  I don't have the kind of money I would need to experiment, and I'm too busy with my Masters thesis to really dive into a whole new area of study right now.  PLUS. I love the Knucklehead, I dont' really want to play any other amp, and I'm sure whatever satisfaction I get out of building my own, without the time able to spend on tweaking it and becoming an expert amp builder, I would lose with dissatisfaction in my sound.

Rivera makes the Knucklehead in combos, a 1x12 closed back ported, and a 2x12 open back.  The 2x12 comes in 100 or 55 watt versions.  I don't have the money to spend on that, and Rivera doesn't take trade ins.  Long & McQuade MIGHT, but it wouldn't be worth it most likely.  FWIW the Knuckle heads have 2 power switches in the back. a Low/High which will switch it from 100 to 50 watts, and A vintage/Modern which changes the way the amp works.  I don't know if its like a Class A / B thing or a Pentode/Triode thing ( I don't know much about this) but the vintage/modern switch really colours the tone in a way that the high/low switch doesn't.  But 50 watts is the highest I want to go, not the lowest.  The 55 watt version can switch all the way down to 12 watts I think, with both switches pushed.

So...  The best way I can think of do this while maintaining my sound, and still satisfy my DIY urges, is to transplant my amp into a new combo cab I'm going to build myself and make it a 2x12, and get one of these to permanently install within the case somewhere. 

Rivera RockCrusher Power Attenuator

Originally I was thinking inside the case with the amp, but this rockcrusher is HUGE by the looks of it. so I was thinking maybe rear facing on the floor of the speaker cabinet.  Which will be open back.

It's the best I can do at the moment, but I think it will go well and despite being a bit heavy for a 2x12. It will suit my purposes, and I'll get a nice new piece of gear for less than I would have paid for a decent amp kit and speakers anyway.  I'll probably take 2 of the V30s out of my 4x12 for the speakers, assuming I can wire them up for 8 ohms.

I already started dismantling the amp to make sure I could do it easily, and as ruggedly it is built, a handy screwdriver is all it took to take it apart safely.  I plan to do this so that it's all reversible when I'm done, should I ever decide to sell the half stack.

I also contacted Rivera directly about it, they wish me luck, answered some questions, and gave me some pointers, and urged me to call them if I have any other questions.

[youtube]VfJDlA2vCS8[/youtube]

Came out without much issue.  The chassis was held onto the cabinet with 8 big bolts.  The bottom of the cab was covered in foil tape to complete the faraday cage.
0QXca2x.jpg


Not a spec of dust inside the chassis.  After 10 years that's impressive, especially with how dusty the top of the chassis was inside the cabinet.  I will not be screwing around in here.
icvi6ox.jpg
 

Volitions Advocate

Senior member
Messages
1,239
Oh.. almost forgot.

Anybody have an opinion on these?  Are they safe to use?  It's another option to lower my power output a bit, and take the EL84 test drive.  (the Knucklehead uses EL34s)

https://www.yellowjacketstc.com/
 
Top