Rocket OT Suggestion/Advice

[Rafiote]

Hi all,

I know its probably been covered many times but I would like to have some opinions and questions answered. I am fairly new to amp building. I built 5 so far. I am planning to build a Rocket and Express and cant tell enough how this forum has been helpful. Lots of good info's.

The primary impedance for the Rocket from searching here is mainly 4.3K. Mercury has the dual primary 5.2K and 6.6k which I would believe is close enough for a Rocket but their prices are ridiculous and I'm located in Canada so you get the idea.... currency exchange... custom fees... shipping... which at the end the PT and OT just in shipping and custom fees will be at least another 100$ to 200. I don't want to go Hammond either so I was looking at all the trannies from Pacific and came across the Plexi 50W.
Primary is 4.5k and about the same size of the Trainwreck model. Pacific Model for the trainwreck they have is 7.5k which from my research is more for the Express...
Below is the spec sheet.

https://cdn.shopify.com/s/files/1/0519/ ... 1662731930

My main question is does it matter to have a higher Wattage rated OT for an amp when you're expecting only 30 to 35W output? Or as long its not underrated its ok?

BTW sorry for my English's still learning everyday so please don't be to harsh as my first language is French

Thanks

Raphael

[Colossal]

The Rocket ran a Dynaco A470S ultralinear output transformer with a 4k3 primary. The amp was not run in ultralinear mode, however.

[Reeltarded]

Your English is excellent. You never even said "ehhh?" once.

I did a search and found a couple of backordered in production EU options (one in Italy for €100) so if you don't mind waiting at least there might be slow shipping options.

[Rafiote]

Your English is excellent. You never even said "ehhh?" once.

I did a search and found a couple of backordered in production EU options (one in Italy for €100) so if you don't mind waiting at least there might be slow shipping options.

Thanks for the compliment

I found this one https://store.triodestore.com/noname.html but its 300$ may as well just go with Mercury at that price. Ill do more research.

I don't need the exact OT that the Rocket used. My question was more like is there alternative that would do close enough what an original Rocket OT would. See example in the first post.

[Reeltarded]

3.9k is close!

https://shop.amppartsdirect.com/product ... 8150&_ss=r

[didit]

Hello --

The Pacific Audio "replica" A470 is ~US$145. They also have them listed at their Reverb "store" if that helps. Baffled by specs they put on it with 5.5K primary and find it difficult to believe it's not a clone. Do suggest Hafler's unique Dynaco interleaving is at least as important to the Rocket design as the nominal impedance, ehhh!!

Best .. Ian

[didit]

And now again --

If memory serves and my email search is correct I have a spare Heyboer-wound "Rocket spec" HTS-8093-1. This would have been purchased in 2014 from Bob at R.J. Guitars back when he was regularly doing batch runs. I'll need to unpack some boxes to confirm so please PM if this is helpful. I'm in Canada so shipping etc should be straightforward.

Best .. Ian

[Rafiote]

And now again --

If memory serves and my email search is correct I have a spare Heyboer-wound "Rocket spec" HTS-8093-1. This would have been purchased in 2014 from Bob at R.J. Guitars back when he was regularly doing batch runs. I'll need to unpack some boxes to confirm so please PM if this is helpful. I'm in Canada so shipping etc should be straightforward.

Best .. Ian

Awesome. Ill contact you soon.

Thanks

Raphael

[RJ Guitars]

And now again --

If memory serves and my email search is correct I have a spare Heyboer-wound "Rocket spec" HTS-8093-1. This would have been purchased in 2014 from Bob at R.J. Guitars back when he was regularly doing batch runs. I'll need to unpack some boxes to confirm so please PM if this is helpful. I'm in Canada so shipping etc should be straightforward.

Best .. Ian

That's the right one... Any of the old Dynaco's work well if you clip the UL leads and you'll get similar results with the various clones. IIRC MM makes a Dynaco A-470. The Heyboer is said to be a direct clone of an old Wreck OT. Phil over at Heyboer was still winding those last I knew. He generally asks for an order of a dozen or so at a time but with enough interest you might be able to sell them all here at TAG?

[didit]

Hello Bob --

And now again --

If memory serves and my email search is correct I have a spare Heyboer-wound "Rocket spec" HTS-8093-1. This would have been purchased in 2014 from Bob at R.J. Guitars back when he was regularly doing batch runs. I'll need to unpack some boxes to confirm so please PM if this is helpful. I'm in Canada so shipping etc should be straightforward.

Best .. Ian

That's the right one... Any of the old Dynaco's work well if you clip the UL leads and you'll get similar results with the various clones. IIRC MM makes a Dynaco A-470. The Heyboer is said to be a direct clone of an old Wreck OT. Phil over at Heyboer was still winding those last I knew. He generally asks for an order of a dozen or so at a time but with enough interest you might be able to sell them all here at TAG?

Yes, I was able to help by finding and moving along that unused a470 you'd sold me some now few years back. Power transformer not so easy as my experience and general consensus here is 250VAC with about 200mA is the sweet spot, and neither the now available "TW" parts nor anything in the common Hammond catalog matches perfectly.

I had a chat today with one of the folk at Amp Parts Direct to encourage them to start stocking Rocket parts along with TW Express/Liverpool that's already in their line. To help them get started I shared the key Heyboer part ###s -- HTS-8093 "a470" OPT and HTS-11426 custom spec "PT-470" with ideal Rocket suitable voltages including a 5V filament winding. These are the core in my Rocket build. Should perhaps have also included mentioning a requisite choke, though Hammond is always good for that.

..

[Rafiote]

Hello Bob --

And now again --

If memory serves and my email search is correct I have a spare Heyboer-wound "Rocket spec" HTS-8093-1. This would have been purchased in 2014 from Bob at R.J. Guitars back when he was regularly doing batch runs. I'll need to unpack some boxes to confirm so please PM if this is helpful. I'm in Canada so shipping etc should be straightforward.

Best .. Ian

That's the right one... Any of the old Dynaco's work well if you clip the UL leads and you'll get similar results with the various clones. IIRC MM makes a Dynaco A-470. The Heyboer is said to be a direct clone of an old Wreck OT. Phil over at Heyboer was still winding those last I knew. He generally asks for an order of a dozen or so at a time but with enough interest you might be able to sell them all here at TAG?

Yes, I was able to help by finding and moving along that unused a470 you'd sold me some now few years back. Power transformer not so easy as my experience and general consensus here is 250VAC with about 200mA is the sweet spot, and neither the now available "TW" parts nor anything in the common Hammond catalog matches perfectly.

I had a chat today with one of the folk at Amp Parts Direct to encourage them to start stocking Rocket parts along with TW Express/Liverpool that's already in their line. To help them get started I shared the key Heyboer part ###s -- HTS-8093 "a470" OPT and HTS-11426 custom spec "PT-470" with ideal Rocket suitable voltages including a 5V filament winding. These are the core in my Rocket build. Should perhaps have also included mentioning a requisite choke, though Hammond is always good for that.

..

Hello all,

Thanks to Ian for selling me his spare OT 470 from heyboer. I also bought the TW PT at amp parts direct which has 260V and 300ma.

One thing I notice since I got interested building trainwreck is parts for the Rocket is more difficult to get vs the express/liverpool.

I got the Rocket cover in terms of iron next one will be the Express which I will probably end up buying the one at pacific for the transfo.

Regards

Raphael

[didit]

Hello --

Recently able to have Heyboer provide details on the specs of that power transformer, and also retrace steps on the source. TAG member Blackburn sold it to me. However I cannot recall if it was wound custom at his request or he'd sourced it from some other member's quantity purchase.

Nominal secondary voltages & current are: HT 235VAC/230mA ; 6.3V/7.5A ; 5V/3.5A. This lines up with what measured values in the finished amp.

Best .. Ian