The Amp Challenge Thread

[Hemisaurus]

I can't believe it was that easy, all anybody wants is the bright caps gone?

Maybe we need photo essays on how to find the bright caps on popular models.

[VOLVO)))]

Do a cap change for my Model T including links to all proper caps!

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[dunwichamps]

Do a cap change for my Model T including links to all proper caps!

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on the originals, according to the schematic there is only one bright cap for the Bright channel. However if you just jack into the Normal channel, there are no bright caps

To further decrease treble you would have to add some shunt caps in.

[Hemisaurus]

I think he's being funny. He needed to do a re-cap job. 'tis not in the spirit of the challenge dude, seeing as you already know all the values and where they go

[dunwichamps]

I think he's being funny. He needed to do a re-cap job. 'tis not in the spirit of the challenge dude, seeing as you already know all the values and where they go

Thats going to be a PITA, those 600V rated caps in that bitch are not exactly easy to come by

[justinhedrick]

Ok I clipped those caps. Sounds much better. Kind of a half Marshall/half Orange tone. And now that I have done it can you explain to me what the caps were I got rid of and what it was they did to make it so trebley?

brian, did you clip both of them? i should do that to my VTM . . .

Yes I clipped them both. A much warmer amp now.

now, sorry for being so dense, but you did NOT clip the bright cap on the volume knob, right?

[VOLVO)))]

Sourcing the caps is going to be difficult? Balls.

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[dunwichamps]

Sourcing the caps is going to be difficult? Balls.

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yea 600V caps are harder to find as most available ones are 450-500V which is below the working voltage in that amp. However, you could try stacked caps but this is going to alter the original schematic and the layout to accommodate 2 caps per node now. Stacked caps could easily get you 600+ Volt rated but you need to buy caps with 2 times the capacitance to get the right value. Node B and C are 450V rated 60-80uF caps, I can get you a decent deal through CE on those. However, the 2 initial caps are 20uF 600V so those are not as easy to find

http://sunn.ampage.org/site/schematics/modelt.gif

if you stack 2 40uF say 300-450V rated caps you would get 20uF effective with a rating of 600 to 900V. You will also need 220k 2W resistors to balance the voltage drops

EDIT

Well my bad you can get 20uF 600V caps from Sprague but boy they are fuckin expensive. Sprague has 20uF 600V caps for 15.40 a piece on CEDist. Big fuckers 2, 1.00" diameter x 3.90" length.

Also found them here, http://thetubestore.com/ca-at-20uf-600v.html. for cheaper 13.75.

Weber also has some 20uF 600V caps for those on a budget 2.00 a piece. I never used them b4 so I cannot comment on how good they are.
http://taweber.powweb.com/store/600Vcaps.jpg

[Hemisaurus]

I've got the regular Weber's (450 not 600) and they're fine. I did wonder about your comment, they're less common, but not unheard of. I'm trying to remember what we used in the 468's, they had cap cans, and some hideous cap values.

[dunwichamps]

I've got the regular Weber's (450 not 600) and they're fine. I did wonder about your comment, they're less common, but not unheard of. I'm trying to remember what we used in the 468's, they had cap cans, and some hideous cap values.

I have used weber 450/500V caps in amps b4, no problemo. In my own stuff I just use stacked caps rather than find a giant 600+V cap. Easier to do.

[Hemisaurus]

Precisely what Ernie Ball did in the HD-130 for the 725V plate voltage, stacked two 450V 100uF

[dunwichamps]

725 plate, thats nuts. Was it running 34s or 88s?

[BrianDamage]

Ok I clipped those caps. Sounds much better. Kind of a half Marshall/half Orange tone. And now that I have done it can you explain to me what the caps were I got rid of and what it was they did to make it so trebley?

brian, did you clip both of them? i should do that to my VTM . . .

Yes I clipped them both. A much warmer amp now.

now, sorry for being so dense, but you did NOT clip the bright cap on the volume knob, right?

No just the ones on the preamp board. Although I have read a lot of people clip the bright cap (c2) on the control board by the pre gain knob.

[dunwichamps]

Clipping the gain pot bright caps is good if your running the amp on lower gain settings but once the gain is nearly full, the bypass cap isnt doing much as nearly all of the signal is coming through already

[justinhedrick]

Clipping the gain pot bright caps is good if your running the amp on lower gain settings but once the gain is nearly full, the bypass cap isnt doing much as nearly all of the signal is coming through already

brian, how are you running yours?

nick, i'd be running mine clean, so would it be more adventagious (sp?) to clip the ones on the pre-amp board, or the one by the volume control?

[dunwichamps]

you can clip either one then, The ones on the preamp board are on fixed resistive dividers unlike the pot caps which are more and more effective as you turn the signal down

[BrianDamage]

I run my preamp pretty clean and turn up the post until the power amp starts to break up. I get most of my dirt from pedals.

[Hemisaurus]

725 plate, thats nuts. Was it running 34s or 88s?

Quad of 34's with a 5.5K primary, we did this discussion before, remember, step it up to 800V and you can get 200W out of it.

[Ayek]

I submit this conundrum on behalf of my drummer, who's a guitarist. He recently got himself a circa 1986 Hiwatt Lead 100, yeah we already know it's not a real Hiwatt. Anyway, although the clean channel sounds good on it's own, it sounds weak and fizzy with his Big Muff or Hot Cake running into it. He says it sounds a little better on the lead/overdrive channel with its OD knob turned down, but still not that great. He runs a stereo rig with a 70's Jansen Bass 50 on the other side and it's putting his Hiwatt to shame when he kicks in the distortion. Any ideas about changes or mods that can be done? Please and thank you.

[Hemisaurus]

How does the Jansen sound clean? My first thought would be blame the Muff, not the amp. My second thought is what's the real model # is it a DR an L100 or what, I don't recall one with two channels, HiWatts were always pretty bog simple.

You could degain the first stage, either by changing the plate resistors, or just putting in say a 12AU7, if that was where it's breaking up, but that would affect the clean sound too. I'm still baffled by this channel business, a two channel HiWatt, really?



I thought we were dealing with this guy. Is he saying it sounds better into the Brilliant input?

If you want to turn it back to a more traditional HiWatt sound, you just lose the extra tube stage. Disconnect the 220K resistor running to pin 6 of V2, connect the wire running to pin 7 to pin 2 instead, and remove that pot connection to pin 2. You've now disconnected the extra tube stage.

EDIT: If you just want to try it, you don't need to disconnect the 220K resistor, just disconnect the pot from pin 2 and move the connection from pin 7 to pin 2, disconnecting the 220K just removes the power from the extra tube stage, you can leave it running for a test.

[dunwichamps]

i would convert V2 into a DC coupled follower but thats hiwatt blasphemy.

[Hemisaurus]

4 moves or less, can you do it?

[dunwichamps]

i also like the bootstrapped DC followers 2. I like the tone stacks driven via a CF, but their TS is unique, closer to an FMV but more complicated.

[Hemisaurus]

4 moves or less, can you do it?

[dunwichamps]

4 moves or less, can you do it?

sure sure but not my amp to butcher up