Rocket/ac30/dc30 like build. OT?

[jaysg]

I believe the OP has to know what he really wants. It's easy to say, 'I want an ac-30/dc-30/Rocket type amp,' but each one is really a bit unique. From what I've gleaned:

AC-30: MM or Heyboer HTS-5619-1/19/50 Woden clone OT, Heyboer AC-30 PT & choke
DC-30: TDS OT, Heyboer AC-30 PT & choke
Rocket: Heyboer HTS-8093-1 OT, Heyboer HTS-5199 PT, Hammond 158M/L choke

[RJ Guitars]

Oh by the way.
Anyone know what the specs on the choke used in a DC30 is?

I "think" the AC30 used a 10H, 100ma one, but I'm not entirely sure about the DC30. Only place I can find that seems to sell replacements are Mercury Magnetics, and they are usually both a little too expensive, and also quite tight about specs on their trafos.

arjepsen - Jaysg has provided what most folks believe is the right part numbers for the transformer lineup in a Rocket build. You could alternatively use the 250V tap on the Pacific 24575 Power transformer and remain inside the "clone standards" that I'm aware of. There are other options that are quite good and cheaper, depending on how far you are willing to wander from the established standards... Your mileage may vary.

The AC-30 choke is 15H @ 100mA. There are a couple different part numbers given for the Hammonds but I believe they are both 15H while one is 75Ma and the other is 100mA. I have used all three of them in Rocket builds as well as a very similar unit that I supply from EDCOR electronics. It's been my experience that there isn't a detectable sonic difference due to the choke on any of my builds. It is very likely that the original Rocket did not use any of these Brands, the closet thing I found to the pictures of the original looks like an Olson Brand to me.

Keep us posted on the build progress, I'll be willing to learn from your experience as well as everyone elses.

thanks,

rj

[wicker]

Hi guys, I'm new here so at the beginning i wanna say hello to all of you, now the question, I was just wondering, if the Magnetic Components makes good trannys ? I'm thinking about Fender style 50W 4.2k primary for my construction (not a wreck, but something wreck inspired)

cheers

[arjepsen]

Thanks for all the great info!!!!

I'll try to remember to keep you posted on the build, however it's going to be a while before I can do so, since money is an issue...
My first bigger purchase after christmas will be a Warmoth strat. After that I'll start scraping funds together for this build.

However, this means that I have a good time to plan out the build.

What I can post now, is the layout I'm working on.
I'd be very happy to hear any constructive criticism.
(also, if anyone could post the specific size of that heyboer dynaco clone, so I can make the measurements fit in the layout, I would be very thankful).

/Anders

[arjepsen]

Ok, here's the layout attached.

Mind you though, it's a work in progress.

Heaters are gonna be twisted, and run in the "bottom" of the chassis, running over the sockets.
I've put the fx send/return jacks on the front, to avoid having to run a shielded cable all the way to the back of the chassis, and back up to the PI.
I haven't drawn in the wires to the cut-control, 'cause I'm not entirely sure how to run them across all the other stuff. I'll have to work with that, once I get the amp up and running.
B+ is taken from the 5V center tap.
The wiring of the powertubes are gonna be done somewhat like in the Rocket, with the screen resistors going straight "up" from the sockets.
I have 3 grounds. One by each input jack-pair, and the last is by the PI.

Let me know what you guys think.

/Anders

[M Fowler]

Wicker

Yes Magnetic Components makes high quality transformers.

Mark

[arjepsen]

Anyone got comments on the layout?

Also, another thing.
In the datasheet for a GZ34, it suggests limiter resistors on the plate, if there's a cap right after the rectifier.
However, KF didn't use any limiters in his rocket.
Are they not really necessary, or ?

[FYL]

In the datasheet for a GZ34, it suggests limiter resistors on the plate, if there's a cap right after the rectifier.
However, KF didn't use any limiters in his rocket.
Are they not really necessary, or ?

Yes and no. It all depends on the PT input and output voltages, PT output impedance and capacitive load.

If the PT puts out 275 - 0 - 275V and C1 is 40µ, the minimum limiting resistance should be 50R or so according to the datasheets.

Measure Rp, the DC resistance of the primary winding (0 to 120V for a US model), then measure Rs, the DC resistance of half of the secondary (275V to CT). Calculate the turns ratio n by dividing secondary voltage by primary voltage.

The actual PT resistance Rt will be Rs + ((n^2)* Rp)

Let's suppose we measure 40R Rp and 30R Rs, we calculate n = (275 / 120) = 2.3.

Rt = 30 + ((2.3 ^2) * 40) = 241.6R.

241.5R > 50R, limiting resistors aren't needed.

Now let's suppose we use another transformer designed for 240V. The turns ratio will be smaller : n = (275 / 240) = 1.1.

If the winding R's are the same - just for the sake of this example - Rt = 30 + ((1.1 ^2) * 40) = 78.4R, much lower but still perfectly OK, 78.4 > 50R.

You should measure the iron you're planning to use; calculate the actual R's and then determine if limiting R's are needed - they aren't in bog standard Rocket builds using Pacific, Heyboer or Hammond PT's. So KF was right, again...

(Nota: results have been rounded)

[arjepsen]

Great info!!
Thanks a lot!

(anyone have comments on the layout I posted?)

[FYL]

(anyone have comments on the layout I posted?)

Looks good, but the proof of the pudding is in the (h)eating.

[arjepsen]

eeehm....
..there's..something....wrong........with.......the......way I eat??????

[FYL]

"The only real test of something is as what it is intended to be used for."

http://en.wiktionary.org/wiki/the_proof ... the_eating