Rocket / Build

[gktamps]

Ace: to clarify my previous statement, as I recall, Allyn indicated to me that Ken used a Dynaco A-470-S for at least one build, but later transformers made for the Rocket did not have the screen tap for ultralinear. In essence, the correct transformer is similar to the A-470-S in all other respects. That seems to be what is most expressed here on TAG. I agree that the Heyboer 8093-1 is going to provide the correct sound.

I had two original Dynaco OTs which I used for Rocket builds, but on Allyn's advice I pulled them and sold them to an audio builder for good money which bought three Pacific transformers down the line. All of my Rocket type builds with 4k3 OTs (both Pacific and Heyboer) have a characteristic sound. I've got a 5k2 OT build that sounds much different and more aggressive, and a 5k RJ Edcor that I didn't like at all, so swapped to a Pacific. The Pacific OTs as spec'd from Allyn sound cleaner with less output volume.

[aceofbones]

Ace: to clarify my previous statement, Allyn indicated to me that Ken used a Dynaco A-470-S for at least one build, but later transformers made for the Rocket did not have the screen tap for ultralinear. In essence, the correct transformer is similar to the A-470-S in all other respects. That seems to be what is most expressed here on TAG. I agree that the Heyboer 8093-1 is going to provide the correct sound.

I had two original Dynaco OTs which I used for Rocket builds, but on Allyn's advice I pulled them and sold them to an audio builder for good money which bought three Pacific transformers down the line. All of my Rocket type builds with 4k3 OTs (both Pacific and Heyboer) have a characteristic sound. I've got a 5k2 OT build that sounds much different and more aggressive, and a 5k RJ Edcor that I didn't like at all, so swapped to a Pacific. The Pacific OTs as spec'd from Allyn sound cleaner with less output volume.

Apologies, my post was inconveniently timed. When I was writing my post you hadn't yet posted yours. When I hit submit, I got the warning that a new post had appeared, which was yours. So it looked like I was agreeing with Dave over you, which wasn't intended.

[gktamps]

No worries, Ace! This is an often discussed and debated topic, and I think the best thing we can say is that there are different OTs that work well, and some that do not. It is disappointing that Pacific maintains their position in light of all that folks here were able to determine many years ago - both for the PT and OT.
Cheers,
Greg

[pfarrell]

So far the only OT I've been able to locate for a Rocket build is the Edcor offering...RJ has been emailed...

[gktamps]

Did you call Heyboer and ask for an HTS-8093-1?

[pfarrell]

Emailed, called. I'll keep trying...Triode has a offering... $$$ though (IMO)...

Edit: Just got em on the phone—6-8 weeks out. Good price though.

[Colossal]

Emailed, called. I'll keep trying...Triode has a offering... $$$ though (IMO)...

Edit: Just got em on the phone—6-8 weeks out. Good price though.

Watch out for Triode/use at your own risk. A good number of us have been burned by them in the past. I will never do business with them again. Caveat emptor.

FWIW, I've used the Mercury A-470-S to good success in the past. Heyboer picked up a lot of slack after Classictone imploded, so their lead time is long.

[pfarrell]

All good. Not ordering from Triode... I'm not opposed to Mercury—I found it! Usually with those guys you have to know what to search for—thanks—Am I assuming it's 4K3? They don't note impedance on their spec sheet.

I'm on the list for the Heyboer OTs. Worst case I get a bunch of different stuff to taste test.

[Colossal]

All good. Not ordering from Triode... I'm not opposed to Mercury—I found it! Usually with those guys you have to know what to search for—thanks—Am I assuming it's 4K3? They don't note impedance on their spec sheet.

I'm on the list for the Heyboer OTs. Worst case I get a bunch of different stuff to taste test.

Yes, the Merc is 4k3 on the primary and has the ultralinear taps. The Heyboer 8093-1 mod omits the U/L taps and, IIRC, the electrical steel is changed from M6 to M19 or M27 (I can't recall which). The Merc is built with M6

[pfarrell]

Use the UL taps?

[Colossal]

Use the UL taps?

The Rocket does not use them, but no reason not to check it out, just as an experiment.

[pfarrell]

So the B2+ to the screens wouldn't be used? in lieu of the UL taps to pin 9? (Right and left tube pairs respectively) Does that mean a change to the 100R screen resistors? ....Apologies if this is an obvious question—I've never done it—Not saying I'd do this out of the gate... just wondering how the hookup changes.

[martin manning]

Yes, like this. EL84 usually use a smaller distributed load fraction than the larger beam tubes, 20% per the Mullard data sheet.

[pfarrell]

This just never gets old. Can't get too too far w/o the OT and choke... But I've read someplace about an 80uf first cap as opposed to the 40s in series? Coulda been a mis-read. Can do either... any opinions? I like this layout...

PF-TWRocket-04.jpg

.

[dorrisant]

Two 40uF in series is 20uF. Two 40uF in parallel is 80uF. Just the opposite of resistance.

That said, a single 80uF is fine.

Your build looks good btw.