trinityamps.com

this is a bit off topic here in the trinity land, but i figure some of you would have a bit of experience with this and so would be able to answer a couple of dumbish questions for me

Anyway, My current project is to make a massive bass amp of doom and it's gonna be pushing 4 6550's, and hopefully be able to rattle the walls in the way a giggable bass amp is supposed to.

so yeah, I got a good deal on the transformers; and the power transformer is a hammond which is rated 400-0-400. and herein lies THE QUESTION.

This extremely high voltage will be great for pushing the 6550's right to their top, but it makes designing the power supply a bit of an issue, mainly because the capacitors. It seems that 500v is about the upper limit for readily available caps, and that's still at least 60v too low for normal caps.

So, I've been looking at running caps in series... I was thinking of just using two of these, http://www.tubedepot.com/cp-jj-800-385v.html -- 800uF 385v can caps and putting them in series to get 400uF (with 770v rating, over 120 volts higher than the b+ should ever go) of filtering for the plate supply ...

The preamp will be running off a voltage divider, after the two giant caps, and it will have some filtering of its own using much more reasonable sized and lower voltage capacitors... the fixed bias supply will also be running off a voltage divider and will probably have some more filtering too just for good measure.

So, would this work? Would having 400uF of capacitance torch the silcon rectifiers that I'll be using? Should I put some smaller caps in between the rectifier and the can caps to prevent having a huge inrush current sucked through the silicon?

Would this even work for giving a nice stable high voltage supply for the 6550 plates or would this just give me a whole lot of capacitance and bugger all for filtering?

would I be better off using caps with lower capacitance and instead making up the difference with a choke? I don't want to lose a lot of voltage through the choke though... and the top of my chassis is already going to be getting pretty crowded with 4 6550's, two giant transformers, a smaller filament transformer, probably ANOTHER transformer for a cooling fan, whatever giant can caps i need, and a preamp tube or two...

I'm open to any ideas and suggestions and whatnot.. and feedback from you guys would help me to no end!

I've been looking at other schematics and tryin to learn the PSUD and whatnot so I've got plenty of research going on here on my end, but still, I was hoping that some of you guys would have some real-world experience you could contribute too!

thanks a bunch, and stay cool everyone!

(and thanks for reading through such a long post... I'm REALLY bad at keeping things short)

later,
daniel

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- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

you could use a HIWATT power supply topology and be fine
go to Mark Huss's site http://mhuss.com/Hiwatt/tech.html
and take a look at the DR103 or any of the 200watters schematics
I used to use DR103 for bass....awesome rock sound..but they had those Partridges in there........
incidently, I'm rebuilding an old SC L100 power supply for a friend right now...

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

you could use a HIWATT power supply topology and be fine
go to Mark Huss's site http://mhuss.com/Hiwatt/tech.html
and take a look at the DR103 or any of the 200watters schematics
I used to use DR103 for bass....awesome rock sound..but they had those Partridges in there........
incidently, I'm rebuilding an old SC L100 power supply for a friend right now...

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

oops

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

What's wrong with Partridges? I can't imagine it's sound, and I was under the impression Hiwatts were in every way more robust than Marshalls.

Bear

that's what I meant......those Partridges had to be there...especially that OT
you should see the Burman amps....monsters.....but the sound of Thor..
but I hear the Hammonds work pretty well (other than heater voltage issues)
not to hijack the thread, but I was going to ask Henk of he'd be so kind as to map out a Burman power supply.....
anyway, for a quad of 6550s...either power supply topolgy would work
BTW, Daniel, you should check out Sowter transformers..they're in UK, but they make some bad**s H-frames PTs and OTs......look a LOT like Partridges

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

I've already got the hammonds, I got a great deal on them from a guy on ax84

i'll check out some of those hiwatt schematics...

does -32v sound like a reasonable bias voltage on a 6550 running a nearly 600v plate?

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- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

well, according to GE datasheet, for 600V plates, use -32.5V grid bias
but depending on YOUR tubes, that may need tweeking, but prob not by much.....
uh, yea.....

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

ok

i was mostly just making sure i wasn't completely misreading the sheets

this is all quite new to me....

oh and also, am i right in believing that teh bias voltage is an opposite voltage of what the b+ voltage is?

ie, b+ is positive (hence the name i suppose) and bias is negative?

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- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

when you get a chance to look at schematics, you'll notice a reverse bias diode tapped from 1 leg of HT secondaries.....and additional conditioning circuit...neg bias, yes
if this is all 'quite new' to you...have you ever built a circuit or an amp before from scratch? just wonderin'

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the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

haa yeah this is my third amp; the first was a p1 extreme (ax84 design) and the second was a lightning... the only thing with those is that they're cathode biased rather than fixed, and their power supplies are much lower voltage...

the "new" parts of this are mostly just the fixed bias and the hoops i have to go through to deal with the fairly extreme voltage

i've built some other little things too...

_________________
- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

Nothing to add but....

Holy Crap that's alot of tube!

well, it beats building an SVT! LOL
witeshade, just make sure your OT has a good lo-freq extension at the volumes you want to accomplish your scorched earth policies with

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

yeah an svt would be nuts.... 6x6550s? damn...

the transformers for my 4x6550 are already ridiculously big

still, I've seen bigger bass amps; ampeg makes a solid state 1100watt bass amp... that's just plain ol' excessive.

I'm also in the process of building one of those 1.5watt Firefly amps (2x12ax7 and 1x12au7), with the line-out, so i can use that as a preamp for the 200watt monster

tube amps are fun

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- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

Maybe Bruce Zinky has a Rumble Bass schematic he's be willing to send you. This was the Fender Custom Shop take on an SVT killer. A PCB version came out branded as the Sunn 300, I believe.

Bear

well, i already have about half of the schematic worked out now anyway....

the only tough part really is picking the resistors to get the right voltages for the various parts of the amp

_________________
- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

incidentally, i just noticed that my output transformer has ultra-linear taps, so I can make my poweramp run in UL mode, which makes my power supply easier, and also is perfect for bass

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- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

you going for BIG clean?
????????????????????????????????
can we see schem when you're done?

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/

of course!

I've been slowly piecing together pieces of the schematic for a couple days now...

I'll be adding two triode/UL switches to get different sounds out of the power amp...

the preamp will have a reasonable amount of drive in it if I want it, but I'm going to be tweaking it for maximum swing rather than anything else.

I'm also currently working on a Firefly as per doug hammond's design with a line-out on it, so if I want big BIG big BIGGGggg distortion then I can just hook that into this amp and shatter windows across the neighborhood

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- daniel garlans - http://ihku.org/~witeshade/ - ct hXc -

big swing.....you might try using diodes in place of screen geid resistors in triode mode.....old hifi tweek

http://www.webace.com.au/~electron/tubes/screens.htm

_________________
the bastard son of Jack Parsons
http://www.rotten.com/library/bio/mad-s ... k-parsons/