Oh, 1 more thing missing on the Rocket..(+ KF flyer & cl

[rooster]

The DC bleed resistors are missing in the Layout diagram.

Again, Ron, this is not a criticism, per se, you have done some work here and it shows. This is just a small oversight.

[On page 3 of this post are also added some copies of an original flyer that KF sent out in the '90s, as well as some sound bites of my Rocket]

[rawnster]

I could be wrong, but I don't think they are part of the components for original Rocket layout. At least its not in the information that I used to build mine, and thus I don't have them. Also, if you'll at Allyn's pics of his recent Rocket build he doesn't use them either. But you know, I'm such a newbie that I could be totally smoking crack!

http://ampgarage.com/forum/viewtopic.ph ... et&start=0

[rooster]

Hey Ron, glad you're here. As to the layout, I am just noting that it is different than the schematic - but upon closer examination it DOES say 'optional'. And I fired mine up anyway without them. Eh, I typically skip the standby for shutdown anyway, and that will release the stored voltages in the primary PS caps. So no worries I guess.

But speaking of the layout, I also see that the second cathode cap on V1 is listed as optional, too. WTF? Is this how you built yours, Ron? If you did, I have to say there is no way this amp will put out 30 watts driving a 1 khz signal - no way! Which is really wrong in my book because this is not anything KF would have wanted in the hands of his playing customers. I added this to mine and it is better. The build is very quiet, I see why you like it, but it will still be quiet if you add that cap. So add it, man.

Any, as a comparison to my AC30 here, the AC30 has got more output power, clearly. My AC30 has 350 plate volts this Rocket has 330, this is a factor. Especially since I was anticipating 350 plate and used a 75 ohm cathode resistor - the same value in my AC30, BTW. And I may have picked up a cold set from Eurotubes, I will check this out tomorrow.


But its a cool amp. The feel and the tone are there, better than in my AC30 I think. It is less noisy as well. I will burn it in and get back to you. Alrighty then, lets get together and compare apples when you can. Let me know. I am looking forward to being a Rocket Man like you, and - a BIG BTW - THANK YOU KEN FISCHER and this FORUM!!!

[rawnster]

Rooster, I did not add a second cathode cap on V1. I've just got a 1k5 resistor in that spot. In learning by the seat of my pants, I was simply following the advice of others who had built a rocket. No cap was mentioned for that spot at all. So, what cap value did you use? I've got bunch of stock lying around. For those of us who don't know any better, what are the pro's and con's of leaving it out as opposed to putting it in?

[RJ Guitars]

But speaking of the layout, I also see that the second cathode cap on V1 is listed as optional, too. WTF?

That label is probably my fault, at least in part. I was the one that added labels to the Matt Taylor schematic... Almost everyone who built these amps in the "Group Build" effort tried the 2nd stage bypass cap and chose not to put it in as a permanent fixture.

The Rocket amp really has a lot of gain for such a low voltage amp so it's not hard to push them into breakup. Adding that 2nd stage bypass cap just throws more juice at it and especially with the EL84's it can be a bit over the top. On the KT66 Rockster amp I have found that it makes a fantastic "Boost" switch. The KT66's seem to handle that extra boost a bit better than my EL84 Rockets.

As for the bleeder resistors - they have zero impact on the tone, cost less than 12 cents and might save somebody from a good shock... what are those "Darwin Awards" all about anyway.

rj

[dave g]

I don't like the 2nd stage bypass cap on my Rocket at all - way too much gain. If I'm going for a harder sound, I'd rather play my Liverpool.

[rooster]

OK, I understand RJ. I guess at this point I would only offer that the circuit only has two stages of gain, and, as you drive these two stages per the original circuit, you can actually get the power section to saturate in a very smooth way. I have to think that this is why KF thought the AC30TB channel was worth messing with in the first place. Certainly he wasn't about reducing gain in the circuit to lose something that he liked.

Eh, oh well, to each his own. I for one would put that cap in if it were my amp. There is a volume control afterall, and being a 500K pot, it is a very smooth and gradual adjustment.

So Ron, that's a 25UF/25VDC cap at pin 3 of V1, just bridge the 1.5 resistor. And get back here and tell me if this ruins what you had going on in your amp., please.

[Macshaft]

My 2 cents , I tried a 22uF/2nd stage in my Rocket and it broke up way too early for my taste . took it out

[angelodp]

As you say to each his own. I Tried the extra cap as well and opted for the version without, but it is quite easy to set this up as a switchable choice. Just out of curiosity ( still a newbie ) what value would cause even greater early breakup??

Ange

[Ron Worley]

I could be wrong, but I don't think they are part of the components for original Rocket layout. At least its not in the information that I used to build mine, and thus I don't have them. Also, if you'll at Allyn's pics of his recent Rocket build he doesn't use them either. But you know, I'm such a newbie that I could be totally smoking crack!

http://ampgarage.com/forum/viewtopic.ph ... et&start=0

The bleed resistors are not on a real Rocket. You can use them as an additional safety measure if you like, but again, they are not stock on the original.

And don't worry about noting errors- I am sure that there might be other mistakes on the documentation and it's a process of refinement getting it 100% correct. I don't take a bit of it personally- I don't own a real Wreck and sure as hell am no Ken Fischer, so I am bound to have a couple things wrong!

[rooster]

Ron, no worries.

To the rest of you that are not using the cathode cap on pin 3 of V1? Can you tell me what the plate voltage is on your EL84s (pin 7), what your screen voltage is (pin 9), and what the voltage reading is on your power tube bias cap (pin 3)?

Here's mine: 330VDC, 325VDC, and 11.67VDC.

This produces 36ma of current per tube using the current shunt method of biasing. For my voltages, this puts me in a very 'safe' range. My AC30 is drawing 39ma of current as another example - a higher voltage amp (350VDC @ plate) with a hotter range but still without failure after 100 hours on the power tubes. (All J/Js, BTW, both amps).

Anybody care to measure theirs and get back here with the info? I think this is important because it might turn out that your tubes are biased on the VERY hot side, causing your amps to behave differently than intended. Frankly, this is the only explanation I can think of as to why you are saying that your amps are breaking up WITHOUT this cap on pin3.

And, BTW, not to be a salesman, but you can buy an EL84 socket that will plug into your Fluke meter and give you the mv current reading at your power tube. (And this of course directly translates to ma: 30mv=30ma) eurotubes.com has them.

Also, if you need to translate what eurotubes is selling in the premeasured ranges from their maximatcher tube tester, I can quickly give you my take on it. I bought a quad that was rated from them on their machine at '30'. Above, you can see what that translated to in my Rocket: 36ma. So depending on your Rocket's plate voltage, this should be easy. For example, if your Rocket has a plate voltage of 300VDC, you would want to go a little higher than '30' from eurotubes, maybe '34' would be good. Going to the other extreme, say a plate voltage of 350VDC, you might try a '26' or '28' from them. OK? See how it works? If you have a plate voltage of 300VDC, and you buy a set from eurorubes that is '40' or '50' (and YES, they have them), you would be in deep doodoo as far as TYPICAL Rocket or AC30 saturation goes.

OK, where's those measurments?

[rawnster]

I'll bite.

P3: 8.7
P7: 300.5
P9: 299.2

[rooster]

Woah, Ron (rawnster), I will see you later today and we can measure your bias more accurately then - but - plainly you are on the cold side of things in the bias department. This coupled with the news that you are NOT running the cap on pin 3 of V1 tells me that, well, our amps are going to sound very different.

For all of you, and I have to assume that some of you do and some do not know much about the AC30 circuit, let's skip to the famous 'drawing by:RD' (aka: Dick Denny) AC30 schematic that can be found in the Groovetubes book and elsewhere. On the schematic is a handwritten note in the vicinity of where the power tube cathode cap/resistor is located. It says: '12.5v AT 30 watts', and then below that, '10v quiesence'. I won't go on about this but I should mention that this one hand written line has come up in many articles regarding Class A amps. Aikens uses this little blurb to support his thought that the AC30 is NOT a Class A amp, for example, completely destroying the meaning of the word 'quiesence' in regards to how the author intended it. But I digress....

'12.5v AT 30 watts' and then '10v quiesence' means that the amp will deliver 30 watts when the voltage reads 12.5 at the cathode cap, but the typical or (even prefered?) reading might be 10 volts. So here then is the spread, 12.5 - 10, in volts. BTW, my Rocket is at 11.67VDC, as I said earlier.

So rawnster, you see where I was coming from when I said you are on the 'cold side' of things? What brand tubes are these anyway, and in the off chance that they are J/J from eurotubes, what was the number rating on the box? I am thinking '26' if they are euroT rated.

Anybody else with those numbers??????

[rawnster]

Rooster, there is a spreadsheet in the Trainwreck files section that Gary compiled which outlines several rocket build voltages. Interesting here is that all of the rocket builds reveal an 8v-9v range for the power tube cathode voltage.

Anyway, take a look and you'll see what I'm referring to:

http://ampgarage.com/forum/viewtopic.php?t=8326

[rooster]

Rawnster - OK, I didn't see that one. Hm, this looks like a group of cold amps to me. (And, BTW, I will see you at 4:30, across from the HD shop, er, your turn with the drugs...) A one on one comparison is in order.

BTW, mine has come around after burn in, I would say its very comparable output-wise to the AC30TB now. I will add that it is quieter, more easily EQ adjustable (with better fine tuning options - can't explain this), and basically just a swell amp all around. Definitely worth the expense and build time, so thank you for prodding me on this, rawnster!

And wow, going back to the amps listed in that voltage chart, how do I get my stats on there? Wouldn't it be great, as well, to find an original TW Rocket with original tubes, running just like KF sent it out? Right now I am having a hard time accepting the fact that all these builds are running without the cap on pin 3 of V1 - AND - biased so coldly - AND - they sound great to their owners. Doesn't RJ have that contact who has an original Rocket? RJ, could you get at least the bias voltage from that guy's amp? That gtr player knows what a good sounding Rocket is all about fir sure.