simple? question

[audiog]

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[kheper]

Short answer. Yes.

The diy tube board can accommodate a diverse lot of output transformers, not just the A-470.

Search these forums for different variations on the the ST-70 design-theme.

The weak link in an ST-70 is the power supply. If you are building from scratch, I suggest a power transformer with better specs, than the PA-60. The toroid power transformers can easily fill that bill, at an acceptable cost.

You could run either EL-34s or KT88s in your amp with a beefier power supply and get a better power output, if that is what is desired.

[rockable]

Why does the diy board not work with A-470's?

Thanks.

[Ty_Bower]

It works perfectly with the A470.

He said it "works with a lot of transformers, not just the A470."

You read "works with a lot of transformers, just not the A470."

Very subtle difference. :)

[rockable]

Yellow_Light_Colorz_PDT_09

Ha! LOL on me! Thanks for straightening me out.

[EWBrown]

The A-430 (and A431) is physically a lot larger and heavier than the A-470, (around 14 pounds / 6.4 KG, as opposed to the A470 which is 7 pounds / 3.2 KG) so it will not fit onto a "stock" ST-70 chassis. It has similar impedance on the primary, and twice the power handling capability, it should be a good match for KT-88s and good for 60 to 120 watts per channel, given a strong enough power supply.

http://www.the-planet.org/pdf/transformer.pdf

It will handle the 35-40 watts of a normal ST-70 quite nicely, and should have as good, if not better, frequency response.

/ed B

[Ty_Bower]

I always enjoyed staring for long hours at John Atwood's transformer test results. It might give you an idea of the capabilities of the A430/A431 vs. the A470.

http://www.one-electron.com/Trans_Tests.html

[EWBrown]

The TZ-442s I bought from Uncle Ned a while ago are basically A-431 clones. These, like the TZ-490s, were "two-of-a-kind samples" and not regular production lots. I am kinda serving as Neds test "guinea pig" but then, I should actually get around to actually using these trannies in some nice working amplifiers.

After the move...

/ed B

[TerrySmith]

I was hoping the TZ-490 would be in production! Ed, have you tried the '490's yet?

[EWBrown]

Not yet, I was going to put 'em on an ST35, but decided later that they might be a good match for 6L6GCs, as I have seen one rather old (non-UL) 6L6GC amp that used a 9K CT OPT, good for around 22-24 WPC.
I had also considered them for the "next gen" 13EM7 PP amp, bu tthen they wouldn't reach their full potential there...

I've not seen TZ490s or TZ442s mentioned on Tube Zone so I doubt that they are currently production items.

/ed B