Higher voltage for Rocket?

[sliberty]

I have seen some talk here about using a hi/lo voltage switch in a Rocket. My most recent Rocket (a 4x10 combo with solid state rectifier and a VVR), uses a ToneSlut transformer that has both 300V and 260V taps. I am currently using the 260V taps, which is probably most common in this config for a Rocket. What should I expect sonically from using the 300V taps instead? Will it affect headroom and the character of the breakup? In what ways?

Also, since I have the entire amp scaled, would setting the amp up for hi voltage (300V tap), and then scaling it down a little bit with the VVR be any different from just switching to the lower voltage (260V)? Seems roughly equivalent to me, but maybe I am missing something.

Thanks,
Steve

[M Fowler]

Steve,

I don't hear a whole lot of difference between the voltage settings and I do not plan to incorporate that function in anymore amps. I had to at least try it. I actually build two different amps. One with voltage switching and 18w/36w switching. The other was the new Zwreck type amp with the voltage selection.

Most of my Rockets run the 300-0-300 Heyboer rather then the 260-0-260 mostly because the AC30 uses 290-0-290 and so do most Dr Z amps of this type with four EL84's. So I thought why not increase the plate voltage.

So after all my rambling on I can't say that the higher plate voltage makes for that much of a louder amp but perhaps there is higher head room.

Mark

[Bob S]

Hmm I've put a 260/300 switch in my unborn Rocket Reverb.
It has 2 x 6L6/el34/KT66 output tubes.
I'll see if it makes a subjective difference to me.
Thanks for the info Mark.
There's a lot of possible uses for an extra toggle switch in a Rocket.

[sliberty]

Thanks Mark. So I think maybe I'll try the 300V taps, but not do any switching arrangement, at least for now. If the differences are that subtle, I probably don't need the flexibility of both settings - I'll just pick the one I perceive as better (if I can even tell).

What are your thoughts on the VVR question - basically the same as switching anyway?

[M Fowler]

Steve,

I have never used a VVR but I hear nothing but good things about using the VVR.

One day I will order one from Dana and try it out.

Mark

[sliberty]

I highly recommend them for taking a loud amp down a peg. Like all other "volume reducers", don't expect bedroom level wailing feedback or huge bass thump, but for an amp that is a little too loud at its sweet spot, it works wonders.

Installation in a Rocket (or any other cathode biased amp) is pretty much child's play too. Fixed bias installations are a little more involved, but still quite straight forward.

The basic circuit is also useful for other needs. For example, if you have a transformer whose voltages are too high for an application, you can use a VVR (perhaps replacing the pot with a fixed resistor) to bring them down to where you want them safely.

Only downside is it is limited to 50 watt or smaller amps. But that is not a problem for me. When I want to use a 100 watter, I probably don't want to turn it down I am too old for 100 watters anyway.

[CapnCrunch]

Steve,

I don't hear a whole lot of difference between the voltage settings and I do not plan to incorporate that function in anymore amps. I had to at least try it. I actually build two different amps. One with voltage switching and 18w/36w switching. The other was the new Zwreck type amp with the voltage selection.

Most of my Rockets run the 300-0-300 Heyboer rather then the 260-0-260 mostly because the AC30 uses 290-0-290 and so do most Dr Z amps of this type with four EL84's. So I thought why not increase the plate voltage.

So after all my rambling on I can't say that the higher plate voltage makes for that much of a louder amp but perhaps there is higher head room.

Mark

Mark,

I read part of an interview with Ken, or it may have been something he wrote where he talked about the Rocket voltage, and why he chose to go with the lower voltage. If I recall it correctly, he said that the lower voltage gave the amp a bigger low end, although he admitted that it gets somewhat loose as you go up in volume. I was curious what your experience was on this. I have a friend who has an all original 61 AC 30. I can say from AB'ing it with my Rocket, that the Rocket definitely has more low end in a very good way vs. that particular AC 30. I would take the Rocket every day over this AC 30 for clean to semi dirty tones. Heavily overdriven, however, I would take the AC 30 as it is more focused and the Rocket gets pretty loose. Have you experienced this with the different voltages?

[M Fowler]

I never wanted the VVR because I have a space that I can crank loud and if I want lower volume I use a smaller amp.

In gigging I haven't had very many places that I overpowered the rest of the band or the room we played in.

Besides 30 watts of tube power for gigging is plenty. Playing lead, my amp cuts through within the treble range which takes less power to amplify.

I have been using the watt's control successfully to lower voltage to the PI as well so that can be used as bedroom control.

Mark

[2tone]

Rockets were designed for around 300V on plates w/ 5o ohm cathode resistor. To jump to hi V, depending on the PT you have, you need to increase the cathode resistor to around 68 ohm or so. On mine, the hi V sounded much more robust, punchy, tighter bottom, lost a wee bit of upper sparkle in exchange for the bolder mids and bottom. I like it that way, and left it at that. It runs 68 ohm and 348 or so plate volts...

[M Fowler]

I am using 62 ohm for 36w mode and 68 ohm on the 18w mode = 130 ohms total at 18w switched. 280-0-280 and 300-0-300 switched HT.

Mark

Corrected to read 36w/18w not 50w like I had.

Resistance is futile

[Zippy]

On mine, the hi V sounded much more robust, punchy, tighter bottom, lost a wee bit of upper sparkle in exchange for the bolder mids and bottom. I like it that way, and left it at that. It runs 68 ohm and 348 or so plate volts...

Did you adjust your dropping string to "correct" the preamp and PI voltages or did you let everything go higher?

One could use the higher voltage tap to gain a stiffer power amp response yet maintain lower voltages in the preamp for classic resposne.

[2tone]

I didn't adjust the pre amp volts as i still had 104V on P1 plate, and i wanted more punch attack from the first tube.it was 85 v before the switch..all resistors and caps were checked before the switch, and I jumped the volts to P1 from different filter caps to check voltages etc. i actually like the increased preamp muscle..

[Zippy]

Thanks.

And thanks for adding the detail regarding your measured V1 plate voltage.

We used to have a chart of Rocket voltages 'round here somewhere. I should pull them back up.

[M Fowler]

rj had this one for his Rockster.

And the original one from file section.

[Zippy]

Thanks, Mark. I thought 85V on V1a looked especially low...