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Bad Shiva 
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Henry Kissinger
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Post Bad Shiva
Hello Maptilians,

I am building a 30W cathode biased class A EL34 map which borrows rather heavily from the Hot Cat 30, coupled together with a Shiva preamp. I feel this will make for a rather scrumptious combination for playing raunchy rock fiddle :huzzah:

Plate and screens are at 380VDC using a 3k25 OT primary. I'm not going to bias quite as brutally hot as the HC30 as it eats tubes. It may end up on the hotter end of AB1 rather than true class A but I don't envisage there being much in it tonally.

Pics!

Image
Image
Image
Image

Later this week I'll get the PI and preamp boards populated and installed :isay:


Tue Jul 15, 2014 6:58 am
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Magnitogorsk
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Post Re: Bad Shiva
Gnar. So more or less, shiva up to the PI, then hotcat for the PI and output?

Once built, clips shall be required! :huzzah:

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Tue Jul 15, 2014 8:07 am
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Henry Kissinger
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Post Re: Bad Shiva
chris_d wrote:
Gnar. So more or less, shiva up to the PI, then hotcat for the PI and output?

Once built, clips shall be required! :huzzah:


Yup. That is the brief :isay: I've grown to like amps with no NFB for my less metal playing. I like the rawness.
There are a few minor differences in the poweramp/supply but its more or less a hotcat so hot biased poweramp overdrive will be mine. I'm using a lightly lower primary and more sensible biasing but it's much the same otherwise.
I hope the Shiva is the right choice of pre. It sounds like it would do well in such a circuit. If not I have 4 triodes to play with if tinkering doesn't get me to where I want to be. I'm getting into strats and teles of late so I think natural darkness of bogner circuits should tame some of the excess twang. I may try an EA MV120 pre too for shits n giggles :huzzah:

There will clips. Oh there will me clips.
I do need to think about building a sleeve for it to live in. Unfortunately my go to guy has moved to the other end of the county under less than favourable conditions so I may have to hack at it myself and I don't really have the tools :poop:


Tue Jul 15, 2014 9:07 am
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Winston Wolf
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Post Re: Bad Shiva
This interests me of course. :eyebrows:

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Tue Jul 15, 2014 9:57 am
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Post Re: Bad Shiva
Oooooh, this sounds like it's gonna be sick. :huzzah:

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Tue Jul 15, 2014 6:16 pm
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The guy from the place with the thing. The one with the stuff.
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Post Re: Bad Shiva
Epic, can't wait to hear it!!! :panic:


Tue Jul 15, 2014 7:29 pm
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Henry Kissinger
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Post Re: Bad Shiva
I hope to get this beast sewn up this week :eyebrows:
Tonight - Populate and install the PI and do the layout for the preamp.


Wed Jul 16, 2014 6:26 am
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Henry Kissinger
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Post Re: Bad Shiva
PI populated, minus a 47k resistor :mad:

Image

Layout for the pre looks good too :eyebrows:


Fri Jul 18, 2014 7:03 am
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Henry Kissinger
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Post Re: Bad Shiva
Image

:eyebrows:


Mon Jul 21, 2014 7:48 pm
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Post Re: Bad Shiva
It's good when thingies are built like that, :isay: :dastardly: :eekass:

It looks durable, :eekass: :eekass: :eekass: :eekass:

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Wed Jul 23, 2014 12:15 am
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Henry Kissinger
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Post Re: Bad Shiva
Image

I have a workshop again :panic: :panic:


Wed Jan 06, 2016 8:15 am
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Pendulous
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Post Re: Bad Shiva
This is a long running project for shore.

Keep it coming baws.

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Thu Jan 07, 2016 12:20 am
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Magnitogorsk
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Post Re: Bad Shiva
HELLYES. :huzzah:

I like how you have done the radials in the PS. I was recently shopping parts for my own new mapbuild and radials are way easier/cheaper to get right now than the axials, so the next thing i do will have to have some flavor of that sort of somewhat non-trad layout biz going on as well.

Also, what is with the crazy pot shafts? Is that just what is available easily where you are at? Are the shafts plastic? Have i already asked this question? It seems vaguely familiar to me but i dinna really recall. :red:

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Thu Jan 07, 2016 8:02 am
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Henry Kissinger
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Post Re: Bad Shiva
Indeed radial caps are waaaaay cheaper and better spec'd than axials these days, especially at high capacitance. I got the idea for laying them like that from some guys take on a D60 over on the slocloneforum. Radial snap in caps are super cheap in high values too and they're much easier to work with than cap cans as they can be mounted directly to the PSU board by placing two eyelets on the board with flying leads. I have a bunch of 22mm cap clamps too so they can be mounted like cap cans if needed.

The long shafts are plastic. They're easy to get hold of at a good price here (80p - that's like a $1.20) and they're made by Alpha so they're still reasonable quality. I picked up a big bag of common values on my last order. Never has a man had so many 1 meg log pots :lol:

I hope to have this all wired up by the end of the week and with a bit of luck it'll work right out of the gate. As there is always a next project I am considering something medium/high gain with a self split 12au7 power amp next as I can score a 4W 22k5 OTfor very cheap and I already have a suitable miniature PT :huzzah:


Thu Jan 07, 2016 10:31 am
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Henry Kissinger
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Post Re: Bad Shiva
Image

It works :huzzah:

The plate and screen voltages are too high :poop:

This calls for Zener dropping in the tail of the bridge rectifier and maybe a sag resistor for tonal fun. I'm going to add a PPIMV too.


Wed Jan 13, 2016 7:23 am
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Magnitogorsk
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Post Re: Bad Shiva
How high is too high?

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Wed Jan 13, 2016 8:22 am
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Henry Kissinger
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Post Re: Bad Shiva
Its around 400-410VDC and really I want to be seeing 370-380VDC if I want the tubes to live more than 30 minutes :lol:

Even at full boar it's not going to pull ridiculous current so I should be safe to drop 30V using 3 10V, 5W zeners. The PT is spec'd for 370mA it somehow I manage to pull all that current (which it wont) that is 0.37 x 30 = 11.1W so there is still an adequate margin. If both tubes were pulling their full 25W and the supply didn't sag the current draw would only be 50/400 = 125mA so the Zeners would only have to dissipate 0.125 x 30 = 3.7W


Wed Jan 13, 2016 9:48 am
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