Rocket Transformers

[sliberty]

I am preparing for a Rocket build, and was wondering what people are using for transformers. I have seen some postings indicating that the Toneslut Heybour 5199 PT is close enough at 260V, and others feel that the 6144 (?) is better at 250V. Also, it seems that the Rocket wants a 4300 ohm OT which the Toneslut is not. So what are people using? Dynaclone from Triode?

Thanks for all opinions and comparisons.
Steve

[RJ Guitars]

Steve,

I have been informed that Rob Hinson is "The Transformer Expert" here at AmpGarage... hopefully he will weigh in because I believe it for myself that he knows the bottom line.

... possibly you followed this thread a while back... https://tubeamparchive.com/viewtopic.php?t=5130

We really shook the trees on this project to get the answer as to what was used in a "Real Rocket". We got the right answers and a few wrong ones too and it was really hard to tell the difference initially. Finally, after we made some commitments to buy and build and started posting some pictures the Rocket experts seemed to give up the goods. Most of these communications took place behind the scenes but that is another story...

Now I think the AmpGarage forum knows for sure the innards of a real Rocket and all will benefit.

You are pretty close on your homework in researching the Rocket... There was a post recently where the builder had an original to compare to. He and others have told me that the correct answer is a Pacific 250-0-250 PT and a special wound Heyboer (based upon Dynaco 470) Output tranny. Phil at Heyboer spoke pretty open about it to me and even sold me one of them... he has the original line card that he claimed his father worked out with Ken Fisher and can build them to exactly those specs. I will eventually build another Rocket with that OPT...

We used a Heybeor 5199 Power tranny and a Heyboer 5200 Output. The result was spectacular and I could not ask anything more of either of them... more than a dozen other guys did the same and consensus is it worked out extremely well. This was based upon the best info we had at the time although in reality I think it was a happy accident. The Output impedance isn't spot on but oh man does it sound good. Also, some guys used a VOX AC-30 OPT and others used a Radio Spares... No bad reports have showed up at this point in time... we'll see.

I have proposed a Rocket-Fest... compare and enjoy all iterations of the Rocket in one grand Amp Fest event!

cheers...

rj

[dave g]

I used the Dynaclone A470 from Triode on my Rocket, and I have to say I really like it. I'd like to do another with a Heyboer just for comparison's sake.

[sliberty]

Just a small question.

Are the mounting holes for the three main OT choices (Moose's Express/Liverpool OT, Heybour's Rocket OT, Triodes DynacloneOT) all the same? [somehow I doubt it, but its worth asking]. Perhaps at least the Heybour and the Dynaclone are the same mounting centers???

[67plexi]

Tone slut transformers have diffrent mounting centers than the dynoclone 4300 fender washers will cover the extra holes.
At first I grounded the mallory power caps to the gz34 mounting bolt after 15 min. it was arcing so I moved the ground over one inch and replaced the two 40uf caps with 50 uf caps it is brighter sounding now but it filters better now no hum or static. I need to put more time on the rocket but have not had the time Im building a few sola sound tone bender MKII professionals and have been testing them on a vox ac30 and a Marshall plexi superlead 100 have not tried on a wreck clone so far the only booster that sounds good on my express amps is a ts-808
mods to tone it down.

[RJ Guitars]

Sliberty,

As I understand it, Rhinson is the transformer man with vast quantities of intellectual property... so from some of his old posts, discussions with Phil at Heyboer, and everything else I could put together, I gathered a lot of information. It does not all reconcile and their seems to be some question whether the Rocket used M6 or M29 steel in the core laminations.

From Phil - After I identified the Rocket output transformer as the Heyboer HTS8093-1, he told me the following: This is a variant of the Dynaco 470 transformer and uses the M6 steel laminations and has some special reverse windings in it. He said this costs a bit more because of the special winding required. According to Phil, everything about this tranny is made to produce pristine sound and minimize distortion... he called it an "extreme HiFi" type of output transformer. Rhinson's notes confirm the alternative winding but indicate that this should be an m29 lamination material... does anybody know for sure?

The complimentary Power transformer for the Rocket is the 9144 which has two high voltage taps. One at 250 volts and a 2nd at 280 volts. He said this transformer is otherwise extremely similar to the 5199 that is considered the "Trainwreck Standard". According to Phil, both of these transformers use M6 steel laminations.

Phil also mentioned that the 5200 output transformer was available with either M6 steel laminations or the m29 steel (M29 is cheaper). I believe it was the M6 that was used in the 5200's we used for the group build Rockets, although Phil said he would have to look that up to confirm it.

Can anybody confirm or identify the facts otherwise?

thanks,

rj

[dave g]

RJ, were the 5200s you guys used the toneslut trannies? If so I believe those are M27. Last time I was at Heyboer, Phil and I had a discussion about laminations - steel grade isn't so much a matter of being cheaper or more expensive as it is about sound. M6 has a very consistent grain orientation which results in the ability to sustain a large magnetic field inside the transformer. Cheaper steels like M27 and M29 do not have a nicely aligned grain by comparison and therefore cannot create as strong of a B field. When you reach magnetic saturation in the output transformer, it's essentially another form of clipping the signal and creating distortion. Therefore, choosing a lamination type boils down to deciding how much headroom you want to have in the OT. FWIW, the old tweed/blackface OTs all were made with M6, while the old plexis were M27. I would think that the 8093-1 used M6, but I could very well be wrong.

[rhinson]

the a470 variants i had made at heyboer have m19/26ga steel, but have a slightly more intricate wind than the normal a470. i'm not sure there's a great tonal diff between these and a regular a470 so experimentation is encouraged! the m19/26ga is the same as the stancor variants that k.f. ended up using in most of the express and pool amps and is the same as you see in other clones (two rock ruby, etc.). ken obviously liked this grade/gauge of steel. my thinking is he was trying for the tone of older m6 steel (which was supposedly a slightly different composition), or maybe he just had samples made and ended up liking this one the best---who knows.

rh

[rhinson]

RJ, were the 5200s you guys used the toneslut trannies? If so I believe those are M27. Last time I was at Heyboer, Phil and I had a discussion about laminations - steel grade isn't so much a matter of being cheaper or more expensive as it is about sound. M6 has a very consistent grain orientation which results in the ability to sustain a large magnetic field inside the transformer. Cheaper steels like M27 and M29 do not have a nicely aligned grain by comparison and therefore cannot create as strong of a B field. When you reach magnetic saturation in the output transformer, it's essentially another form of clipping the signal and creating distortion. Therefore, choosing a lamination type boils down to deciding how much headroom you want to have in the OT. FWIW, the old tweed/blackface OTs all were made with M6, while the old plexis were M27. I would think that the 8093-1 used M6, but I could very well be wrong.

i don't think that's correct. i believe the drake outputs (139, 128, and 103) used m50-----i believe both greg germino and brian wallace would confirm this, at least that's my understanding, with the early radiospares jtm stuff being m6 perhaps. the 100watt dagnall's used the m6 of the day-----some have said it's not quite the same as the m6 steel made today and had different properties that gave a different sound. and the fender stuff, most of the smaller stuff was m27 i believe and i'm not sure of the bigger stuff. i was under the assumption that m6 has always been 29 ga, but having examined a few old fender bassman heads, twin reverbs, etc. it sure doesn't look like 29 ga to me----but my eyes aren't what they used to be !! rh

[Zippy]

RJ, were the 5200s you guys used the toneslut trannies? If so I believe those are M27.

From http://toneslut.com/transformers/index.html:

"Our transformers are wound in the USA by Heyboer. The power transformer is the old standard we all know and love, but the output transformer is wound to previously proven specs on M27 steel, with dual primaries!

We all know there's no one holy grail of tone when it comes to the work of Ken Fischer. Each amp is individual, right down to the primary impedance of the output transformer. The primaries on these trannies are chosen because the values have been used in real trainwrecks and because each sounds different (and good, depending on the taste of the listener) in 1+2 topology amps. Now you don't have to wrestle with the problem of whether to go with 5200ohms or 6600ohms in your express style amp. You can try them both and let your ears decide which you like best.

The lower gauss M27 steel is chosen to provide richer overtones and slightly fuller bass than the more common M6 laminations. "

[RJ Guitars]

RJ, were the 5200s you guys used the toneslut trannies? If so I believe those are M27.....

Actually the first dozen transformers were directly from Heyboer and they were 5200's (no 6.6K tap). I purchased a second batch from Toneslut and they are dual primary. I have not personally built with the dual primary and have yet to compare the tones of the two transformers and/or the two taps.

Phil wasn't sure which steel was in my original order although from the pricing it indicated they were probably M6... he said if it gets important he can look it up.

I do think I read a thread somewhere indicating some evidence that KF occasionally used the 6.6K tap for either a Pool or a Rocket, but I don't recall the whole story right off the top of my head... anyway that kinda goes along with what Zippy was saying about them.

rj