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#1
So I have been commissioned to do a pretty interesting project here. The idea: take a craptastic practice amp, gut it, and turn it into a kick-ass all-tube 5 watter!

The donor specimen:




The venerable...err...I meant terrible Peavey Rage 158! This baby is packing 15 watts of uninspiring sterility and pumping it through a generic, Chinese sweat-shop built 8" speaker.

I know what you're thinking: how could you possibly improve upon this platform, Craig?? Well, I'm damn sure gonna try!

OK, in all seriousness, the owner had this amp laying around and wondered if I could do anything with it. He doesn't plan on gigging, but wanted a practice amp that would be inspiring to play and sound great. And he wanted it on the cheap (hence the donor amp). So I looked the amp over and did a bit of brainstorming. It's a really tight space, so I'm working with size limitations as well as the limitation of an 8" speaker. But lest we forget the majesty of the Fender Champ!

I wasn't interested in cloning a Champ though. So what I decided on is a circuit design I'm calling the Suckerpunch Lite. It's a variation of the Suckerpunch15 preamp mated to a SE 6V6 power amp. It can be done with physically small transformers as well as a relatively small amount of circuitry real estate. These were important points, as I'm going to have to shoehorn everything in this chassis:



So that's the gist of it. I'll be documenting the project here. Should be fun!

Oh, here's a quick hand sketch of the schematic for this build:
Suckerpunch Lite
#3
Looking good dude. Subscribed.
Marshall amplifiers are the truest purveyors of rock and roll known to man.

"And give a man an amplifier and a synthesizer, and he doesn't become whoever, you know. He doesn't become us."

Holy crap, check this out!
#4
Posting for subscription purposes. Keep us updated!
Feel free to call me Kyle.

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#5
Sounds interesting I wish i knew electronics so I could mod my lil marshall mg haha

There's

NEVER

enough

GAIN


#6
I think this is one of those things we've all thought about doing this at some point, but never been awesome enough to actually follow through on. Don't let us down.
#7
Quote by Roc8995
I think this is one of those things we've all thought about doing this at some point, but never been awesome enough to actually follow through on. Don't let us down.


+1

I wanted to gut an MG15 but couldn't figure out what I would do with it.
E-peen:
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#8
Quote by Roc8995
I think this is one of those things we've all thought about doing this at some point, but never been awesome enough to actually follow through on. Don't let us down.


Oh trust me, I won't let you down!
#10
I'm curious as to why you have such large grid stoppers, and so small of grid leaks. Isn't the 1M pot too large of a grid leak for a power tube? I'm intrigued by the overall preamp design to say the least, very interested in hearing clips when it's finished.
#11
Quote by blandguitar
I'm curious as to why you have such large grid stoppers, and so small of grid leaks.


The grid leak resistors help determine the gain of the preceding stage. The larger grid stoppers help roll off high frequencies.

Quote by blandguitar
Isn't the 1M pot too large of a grid leak for a power tube?


No, actually it's not at all.

Quote by blandguitar
I'm intrigued by the overall preamp design to say the least, very interested in hearing clips when it's finished.


Although the actual Suckerpunch15 has several different resistor values in the preamp than this amp (dividers are a bit different and the 3rd stage plate load resistor is different for example) and also has a 5751 in V1 instead of a 12AX7, the overall topology is very similar. Here is a vid of the Suckerpunch15 going through clean to gain.

http://www.youtube.com/watch?v=dxgVDcmhLWw
#12
Although I want to say I've seen something like it before, what is the purpose of the diode/resistor on the second half of V2?


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RBY CYOA
#13
Quote by MonkeyLink07
Although I want to say I've seen something like it before, what is the purpose of the diode/resistor on the second half of V2?


It prevents inter-electrode arc'ing within V2b upon initial power-up.
#14
Orrin, (I know I got it this time) It prevents arcing when powered up, extends tube life. I'll look at the video tonight, my laptop doesn't have sound.

Edit: What he said
#15
I'm watching this!
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#16
the cabinet is god awful looking for a sexy amplifier you're trying to put in. just saying...
Call me "Shot".

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#17
Stickied and a free bump for you!


Maaaan, I remember playing through one of these while taking guitar lessons. Jesus shit was it ever terrible.

Also, what Colin said. Now I'm sad I sold my Toneblaster for twenty bucks.
#19
I've always kinda wondered if i could do that to my peavey rage amp too, but mine has a blue marvel speaker in, which I though sounded kinda cool(title wise, the speaker itself is pretty torn up). Anyway, bump for awesomeness really.
#20
Quote by ECistheBest
the cabinet is god awful looking for a sexy amplifier you're trying to put in. just saying...


I hear ya, Shot. The owner has a very low, very tight budget for this build so having a cab built was out of the question.

@everyone else
Thanks!
#21
Can't wait to watch this progress! I have a Rage (my first amp of course) that only works some of the time. I have been scheming things to do to it, but will probably go with a transistor design.
I am impressed you are cramming so much into that little chassis.
#23
I'll be keeping an eye on this! I also have a peavey rage 158 and this has just inspired me .

Would have been good to have a before and after sound clips :/
Schecter C-1 Hellraiser Fr
Peavey 6505+ 112
#24
Quote by james4
this should be pretty cool


it looks like you might have enough room in there to open it up for a 10" speaker though..have you looked into that at all?


It may be possible, but the speaker magnet could quite possibly interfere with the transformers. It's a pretty tight space in there as it is.
#25
Free bump for awesome idea! Subscribed.
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FrustratedRocka you are a legend

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The man clearly knows his shit.

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one of the best, educated and logical posts I've ever seen on UG in the Pit. Well done good sir.
#26
Thanks, buddy!

Currently working on circuit layout design as well as the faceplates for this amp. The control panel will be different and there will be no more Peavey branding on the front when all is said and done.
#28
OK, so I'm finally able to dig into this build. First order of business is fitting the iron. One of the reasons I decided to go 5 watts with this amp is because of the low current demands inherent of the topology. This is a small chassis, so even medium sized iron is out of the question if we don't want to make a bunch of trouble for ourselves. But thankfully, because we're running 2 12AX7's and a 6V6, small current requirements equals small iron...and small iron fits the bill, helping to preserve precious real estate on this little chassis.

Below is the planned layout of the power transformer, output transformer, and filter choke. As I do with every build, I'll do a headphone test to ensure the PT doesn't interfere with the OT. I don't think there will be any issues.

Isn't that filter choke cute?




The easiest part of this build--the speaker replacement--is done. The stock speaker was tossed out and a Jensen MOD 8-20 was put in its place.




Here are the tubes: 2 JJ 12AX7's and a Tung-Sol 6V6GT.




After I test the transformer placement, I'll begin fabbing the circuit boards. The main circuit board is designed, but there is still a small board I need to lay out. Then the construction will commence. Most likely, my next post will have pictures of them.

Just getting started here, but it shouldn't be long at all before this amp is ready to fire up!
#29
Which one's the choke, which one's the output transformer, and which one's the power transformer?
Quote by dr_shred
FrustratedRocka you are a legend

Quote by littlephil

The man clearly knows his shit.

Quote by Banjocal


one of the best, educated and logical posts I've ever seen on UG in the Pit. Well done good sir.
#31
Why are you using a half wave rectifier? To lower the voltage? And wouldn't it suffice to have diodes on just one tap of the transformer?

Also, how do you do that headphone transformer test? That sounds really interesting. I have a build coming up where everything's gonna be really cramped, so it would be really useful to be able to accurately determine good transformer placement.

Your project is kinda similar to what I did to my old SS POS amp combo (put my modded VJ in it).
I think you helped me out on that build too.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

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Rackmount Tube Amp Project <<< Updates!
Last edited by Kanthras at Oct 20, 2010,
#32
Quote by Kanthras
Why are you using a half wave rectifier? To lower the voltage? And wouldn't it suffice to have diodes on just one tap of the transformer?


Where do you see a half wave rectifier? The AC off the PT secondary is full wave rectified. That is why there are diodes on both secondary leads. It would be half wave rectified if there were diodes on only one of the leads.

Quote by Kanthras
Also, how do you do that headphone transformer test? That sounds really interesting. I have a build coming up where everything's gonna be really cramped, so it would be really useful to be able to accurately determine good transformer placement.


You hook up headphones to the OT and energize the PT. Move the trafos around until you find a placement that works and doesn't present audible interference in the headphones.
#33
Quote by CECamps
Where do you see a half wave rectifier? The AC off the PT secondary is full wave rectified. That is why there are diodes on both secondary leads. It would be half wave rectified if there were diodes on only one of the leads.
I guess the way you have the rectifier written down kinda confuses me. You effectively have two diodes there (two pairs in series), one on each side. Two diodes isn't enough for full-wave rectification without a centre tap. And it doesn't seem to be connected to both sides of the reservoir cap. I must be missing something here.
You hook up headphones to the OT and energize the PT. Move the trafos around until you find a placement that works and doesn't present audible interference in the headphones.
Sweet, thanks!
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#34
Quote by Kanthras
I guess the way you have the rectifier written down kinda confuses me. You effectively have two diodes there (two pairs in series), one on each side. Two diodes isn't enough for full-wave rectification without a centre tap. And it doesn't seem to be connected to both sides of the reservoir cap. I must be missing something here.


Oh, I'm sorry. My illustration confused you. I drew the center tap on the primary side, which is technically wrong, but I knew what I was intending. I only really drew the schematic for myself, which is why it's extremely basic with no part numbering, tolerance values, etc. I draw the PT center tap on the primary side sometimes but like I said, I personally know what I'm intending.

The secondary of the PT is center tapped, and the center tap is grounded. Two diodes on each secondary lead. Only one diode on each lead is needed, but I put two in series for redundancy in case of a failure. The cathodes at the ends of the series are tied together and connected to the positive lead of an electro cap. That is a very standard solid state (full wave) rectifier on a PT secondary with cap input filter.
#35
Quote by CECamps
Oh, I'm sorry. My illustration confused you. I drew the center tap on the primary side, which is technically wrong, but I knew what I was intending. I only really drew the schematic for myself, which is why it's extremely basic with no part numbering, tolerance values, etc. I draw the PT center tap on the primary side sometimes but like I said, I personally know what I'm intending.

The secondary of the PT is center tapped, and the center tap is grounded. Two diodes on each secondary lead. Only one diode on each lead is needed, but I put two in series for redundancy in case of a failure. The cathodes at the ends of the series are tied together and connected to the positive lead of an electro cap. That is a very standard solid state (full wave) rectifier on a PT secondary with cap input filter.
Ah, makes much more sense now! I figured you'd know what you were doing, since this isn't exactly your first build.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
#36
Main board is done. Empty turrets are for components that mount directly from turret to some other part of the amp.

#38
subscribed!
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Quote by Anonden
You CAN play anything with anything....but some guitars sound right for some things, and not for others. Single coils sound retarded for metal, though those who are apeshit about harpsichord probably beg to differ.
#39
Quote by forsaknazrael
metal film mojo ftw!


Wait....what?

Feel free to call me Kyle.

Quote by ibz_bucket
Just so you know, I read everything you type in a Mike Rowe from Dirty Jobs voice.

Quote by tubetime86
I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...
#40
Quote by forsaknazrael
metal film mojo ftw!


Haha! Unfortunately, they don't have all the vintage noise and hissing of carbon comp resistors.

But I guess my customer will just have to deal with a lower noise floor!
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