CORNELL DUBILIER - TC74

[ckpop]

Looking for anyone interested in a group buy of CORNELL DUBILIER - TC74 capacitors. 16uf 450v for tweed style amps. Allied and newark are out and I want to see if I can get them to lower the minimum order.
I use them in tweed style builds and I know I could use sprague but I dont want to cut any corners.
PM me if anyone is interested.

[Trout]

Looking for anyone interested in a group buy of CORNELL DUBILIER - TC74 capacitors. 16uf 450v for tweed style amps. Allied and newark are out and I want to see if I can get them to lower the minimum order.
I use them in tweed style builds and I know I could use sprague but I dont want to cut any corners.
PM me if anyone is interested.

Are those actually an extra $10.00 better than the other brands?

[ckpop]

Yes they are more expensive but I have used them in all my tweed copy amps. Just like them better then sprague or other caps.

[Cliff Schecht]

Not interested. Why pay out the ass for marginally better caps?

I buy Nichicon when I can, Xicon when I have to and use my stock of Sprague Atoms only in personal builds and such. TBH Atoms are perfect for tweed stuff both in size and in "feel" (i.e. the ESR of the cap is appropriate for the circuit).

[diagrammatiks]

using them is of course your choice....but the specs on those caps aren't that much better then what's available.

I personally wouldn't touch an atom with a stick but the nichicon tvx series are half the price of the normal "guitar amp" capacitors and are rated 10 times better.

the rifa kemet peg124s are even better. the rifa branded ones are still available surplus and the kemet branded ones are slowly starting to become available again.

[David Root]

So what makes a cap "suitably tweedy"? The '50s originals had specs that I don't think you can get any more, modern caps all have "superior" specs.

I used a CE can cap (ie Mallory twistlock) in my EH-150 Type IV build, which is a '41 circuit. These were I believe '70s design can caps built on the original Mallory tooling. Sounds OK to me. I think the '50s preamp tubes & PI, and WW2 6L6GAs have more to do with the tone than the can cap does. Does tweediness have to do with the electrolytic paste formula and/or other chemical variables?

Just curious, not knocking the concept.

[diagrammatiks]

I don't actually know if it makes that much of a difference, although I definitely do notice a difference between film caps and electros in the power supply...

but, in the 50s and 60s you'd be talking about 10uf-47uf electrolytics with esr ratings in the high 4 digit mOhms and leakage currents above 8rootCV at the very least.

[ckpop]

yea it looks like I will have to use different filter caps instead of the TC74's. Right now the min order is 200 so I bet cornell dublier will discontinue making the 16uf sooner or later.
It is the fact of having to change my part formula in my amp builds that means good or bad it wont be the same exact end result.

Even if the TC caps cost more, finding replacement caps cost the same. My OCD will buy every brand to AB next to each other to find the new cap I want to use.

[Cliff Schecht]

So what makes a cap "suitably tweedy"? The '50s originals had specs that I don't think you can get any more, modern caps all have "superior" specs.

I used a CE can cap (ie Mallory twistlock) in my EH-150 Type IV build, which is a '41 circuit. These were I believe '70s design can caps built on the original Mallory tooling. Sounds OK to me. I think the '50s preamp tubes & PI, and WW2 6L6GAs have more to do with the tone than the can cap does. Does tweediness have to do with the electrolytic paste formula and/or other chemical variables?

Just curious, not knocking the concept.

Damnit, I thought I responded to this post but obviously I didn't ever post it..

Caps of similar size have a similar ESR typically. This is a function of the chemistry of the electrolyte gel, the materials/construction of the internals (type of aluminum, shape of the plates, packing density, etc..). The older caps do have a somewhat higher ESR but probably not magnitudes of order higher. Remember though that even in those days manufacturers were striving to minimize ESR and optimize the overall electrolytic design and so while these caps do go bad because of age (the electrolyte gel dries up), in their time they weren't that bad.

So with all of that said, I should point out that I am using 70's NOS orange Sprague Atoms, mostly 16uF @ 500V but I have other values as well. These are what I use in my tweed builds, at least for the first cap, because even after I reform them the ESR is higher than the newer Atoms. Unfortunately I can't compare the ESR of the orange Atoms to paper electrolytics because none of the paper caps are any good, but I can compare the ESR to can caps from the 50's and they are similar enough to be negligible. When the electrolyte gel dries out the caps are ruined but if the aluminum oxide on the aluminum has depleted, reforming can bring this oxide layer back and revive caps. I use a Sencore cap tester to reform because when you do leakage tests it puts full voltage on the cap through a large series resistance, exactly as one does when reforming caps on a bench supply, and you can watch the leakage go down as the cap reforms.

Also FWIW the most critical position for using an "appropriate" cap is the first B+ decoupling cap. This is what has to handle a majority of the ripple current as well as supplying the instantaneous current to the plates of the power tubes. Larger ESR (higher internal resistance) means that the cap cannot discharge current as quickly and with this you do get some lag. Whether this is truly measurable or not if completely up for debate mind you and until I actually take some measurements, much of this is voodoo electronics . When I build my 5F6A in a month or so I will start looking into this in more detail.

[diagrammatiks]

Cliff, my first response is to skeptical but I do know that what you're saying is right.

I just don't know how much of a difference it makes above a certain esr though...

what do the orange atoms run for a 22uf or a 47uf?

The FT type A that's sold by CE gets 4k and 2k respectively.

I do definitely hear a difference going between a film and an electro...but the Q factor difference there is orders of magnitude.

a 22uf film cap rated at 630vdc generally has an esr of around 9.

[selloutrr]

My 2 cents... Unless your client has deep pockets or it's a personal dislike toward other brands for a reason generic Electrolitics and nicholson for a couple bucks each work just as well. The $40 you save would be better splent on a NOS preamp tube in V1.

What you need to be most concerned with when Caping a Fender is that the capacitor still fits under the can cap. other then that it's all good.

[David Root]

Somewhere (maybe here) I saw an opinion that the German F&T caps are "very similar" to the orange Spragues and therefore particularly applicable for period Dumble clones. I don't recall in what way they are "very similar".

Anyone care to comment on that?

[selloutrr]

They are both round and rectangular!
with a positive and negative lead.. Ok I'll stop being an ass

it's not size all the F&t stuff is very compact
the orange sprague is pretty large by cap standards

it would have to be in the make up or materials?

[JamesHealey]

man i just use what ever is cheapest that week! Vishay, nichicon, f&t, Philips..

They all sound very similar! I find the circuit is more important than cap brands. Especially in new designs. I have no interest in being vintage correct. Waste of my time and money.

[hitchcaster]

maybe ask RJ to see if you can join forces since he sells them
http://www.rjguitars.net/
your talking about the mallory tc right?
killler caps.... don't understand the pricing though, its bizarre
next fav are the tech caps which are much better bang for the buck
new blue atoms suck