6L6 rocket

[Markusv]

Zippy and RJ

BTW

What would be a great 10 inch speaker in you opinion?
I can quite consider a 2x10 conbo if it keeps the bass content and full midrange

Markus V

[Zippy]

Hmmmm, RJ, what is in my tweed Super? We'll get you the specifics, Markus. It's funny you ask because, as RJ can tell you, the 2-10 is one of my favorite setups - whether in a tweed Super or a custom blackface Bassman 2-10 combo. I like mixing alnico and ceramic speakers and have been doing that for better than 20 years now. My Super has a set of Webers in it but I don't recall which ones offhand.

Someday, I'll reclaim those KT66s and put them in that Super.

[Markusv]

The silver ten's at Weber look great

Description:
"Replacement for Vox and Marshall AlNiCo 10's
10", 11oz AlNiCo plug magnet, 20 or 30 watts, 1-1/4" voice coil, ribbed cone.
Warm, smooth, great compressed overdrive tone with smooth distortion edges. Later/smooth breakup, compressed at high volume."

One each of the Alnico and ceramic could be great
This is already such a bright amp that I think the Blue pups may be overkill however these may extend the amps usefulness for overdriven tones

Markus V

[Markusv]

Is it still a Rocket? In schematic land it actually looks more like a 59' Bassman with a cathode biased output stage... yet that is amazingly similar to a Rocket. I think mine still has a Rocket vibe to it... just has a little more muscle to it. Very cool amps!So, yes, that's the vibe - I think the biggest change is tweaking the cathode follower for some gain/compression.

Zippy and RJ (and anyone else)
My question would be around the cathode follower values for more/ less compression etc. And also about the slope resistor ,R8

I do not really understand cathode followers and how their values impact performance. I see the cathode resistor is the main difference and that is followed by the similar tone stack but with different values, namely the slope resistor and some cap values seem smaller.

Please educate before I start playing around in the dark

Best ragards,

Markus V

[Zippy]

Zippy and RJ (and anyone else)
My question would be around the cathode follower values for more/ less compression etc.

Markus,

I don't recall if I've shared this with anyone beyond RJ but here ya go. Put a 50k trimmer in series with the 56k cathode resistor and dial to find your sweet spot. Values of 100k give unity gain, values toward 56k increase gain and compression. I'm thinking of putting this control on the front panel either as a switch or knob.

Changing the slope resistor basically shifts the peak frequency. Check Duncan Amps for his tone stack simulator to see for yourself. Values in the range of 33k to 100k are the norm.

[RJ Guitars]

Hmmmm, RJ, what is in my tweed Super? We'll get you the specifics, Markus. ...My Super has a set of Webers in it but I don't recall which ones offhand.

Zippy the Tweed Super has a 10A100-T Alnico in tandem with a 10F150 Ceramic.

My own cabinet has a 10" Blue Alnico that I think is a Fender and an Eminence "Redcoat Ramrod" ceramic speaker in it.

I like the combination of the two speakers better than I like either of them in pairs.

rj

[RJ Guitars]

...My question would be around the cathode follower values for more/ less compression etc. And also about the slope resistor ,R8

I do not really understand cathode followers and how their values impact performance. I see the cathode resistor is the main difference and that is followed by the similar tone stack but with different values, namely the slope resistor and some cap values seem smaller.

Please educate before I start playing around in the dark

Best ragards,

Markus V

Markus, Fishy Pete supplied me with a link that is quite a good read on this topic... http://www.freewebs.com/valvewizard1/dccf.htm

Now I can't argue with the guys logic and his scope traces are quite convincing... I think I'll consider him the expert and myself the student.

Zippy is right about that slope resistor. You can change that value using the Duncan Tonestack calculator and see the center frequency shift accordingly.

I am currently looking into options to allow me to run cleaner at high volumes on my Rocket(s). All three of my Rocket amps break up at about 9:00 O'clock and then just get louder as you turn them up. It's pretty cool because they never mush out... but no doubt it's got a sweet crunch at 9:00 and limited headroom. My component selection is nearly identical in all of them although each of them have unique transformer sets.

My friend Derek Ferwerda says that his Favorite setting on Trainwreck Rocket #1 is between 1 & 2 O'clock. He can dial the guitar up to get crunch or back the guitar volume down to get clean for his country style licks... He only plays single coil pickups so I know that has a little impact on the results as well.

If I find the mechanism to preserve the fullness of the tone and get more headroom, I think I'll want it as a switchable option because the amp is very cool for almost everything I play... just curious how to expand the possibilities.

rj

[Markusv]

RJ and Zippy

OK, I want to post an update regarding all tweaks that I have implemented following your advice and inputs .
Some of these were mentioned in an earlier post but I will include them for completeness' sake.. Before I do that I want to thank you for all the input thus far
It has helped me a great deal
I will also look more carefully at the speakers you mentioned.

Some general observations:
I did play around with the slope resistor and did not really care for the changes that it provided. In other words, I feel the current value is optimal for the tone stack and tube compliment.

More specifically, here are al the changes I have done so far:

-Mid control added =25K
-Increased the mica cap on volume pot from 100pf to 250pf
-Single/parallel inputs and the 2 cathodes on V1 are now running to 2 parallel 1.5K resistors. Plate is shared 220R as standard
- Added a 10uf bypass cap on the second stage cathode resistor (huge difference!)
-Also added a "Drive" pot. It s a 50K pot in the faceplate in series with the cathode resistor. The result is more subtle than I expected. Dimed, the control provides a standard 56K resistor value. At zero, the cathode resistor is upped to 100K+_
If I say the result is subtle, it is perhaps beacause at moderate volumes the impact is simply a bit more grit with the lower cath resistor value. The amp breaks up a bit sooner and seems more touch sensitive.
It also depends which input is used
The lower gain input has the effect that I can get a greater amount of cleans until relatively high volume with the cathode resistor set to a total of 100K.

With the higher gain input I can adjust the amount of cleans too, everything just happens sooner on the gain dial.
I think I will live with this control for a while and decide if I want to keep it. As I say the changes are relatively subtle, but I think they are useful and meaningful enough to warrant the extra control

I used 2 humbucker equipped guitars to test with. - A Yamaha SBG200- sort of a LesPaul clone and
Yamaha SA500- in this case a semi-hollow ES335 clone with faily hot humbuckers
I will use a strat next for extensive testing, - I have played around a bit with one, but currently I favor the Humbuckers because they respond so well to the brightess of the amp

Thanks for the Valve Wizard link- he really seems to be well respected- I think he goes as Merlin on AX 84? I will read and try to educate myself

The speakers are so important. I see the differencebetween semi-open Private Jack cab and a closed back Governor cab and I can only guess at the tonal variety that 2x 10 will give me.
At the same time I want to finish ths amp up, build the combo cab and just play it!. So I will play around with some of the 10's I have here, and if you could post soundclips with 10's I would really appreciate it. Perhaps the soundclips posted earlier were with the 10's??


Thanks again fo all the help

I will keep you updated with progress.
Oh BTW- Zippy, do youy have any more KT66 valves you want to test?
I would be willing

Markus V

[Zippy]

Nice work, Markus. Thanks for the rapid feedback.

Yes, the tone stack is already a good one (with the addition of the mid control) regarding the slope resistor.

Whether or not the 'wreck police toss us on our heads, it's all worth it. I know we've too many knobs for a True 'wreck, but hey...

I'm interested to learn how these variations treat your Strat. You may go back to the smaller value on the volume bypass or a larger value on the treble cap. It really is personal preference from here.

Oh BTW- Zippy, do youy have any more KT66 valves you want to test?

You are a good friend.

[Markusv]

Whether or not the 'wreck police toss us on our heads, it's all worth it. I know we've too many knobs for a True 'wreck, but hey...

I'm interested to learn how these variations treat your Strat. You may go back to the smaller value on the volume bypass or a larger value on the treble cap. It really is personal preference from here

Yup- too many knobs, but it is really a matter of bringing components that were already there, out to the control panel. Nothing added that was not already the essence of the Rocket



So far, I found the strat a bit thin- sounding on overdriven tones. But I don't want to lose the Mica cap on the volume, so a switchable treble cap may be the deal- will add a bit of a boost in its own way- I think
I love fat mids in bright amps (think Liverpool) and some other amps I have built have this switchable mod for strats and it works very well

Regards,
Markus V

[Normster]

Try paralleling another 500pF coupling cap on the first gain stage (along with the exisiting 500pF). Instant fatness and just one more switch...

[Markusv]

Norm

That's normally how I go about it.
But I use a 330pf. Have you done this on the rocket?

M

[Normster]

I switch between a 500pF and a .0012uF. The only time I use the "fat" setting is on my Tele in the bridge position. (There's a 4.7M resistor to ground to keep popping to a minimum.)

This amp also uses .1uF coupling caps in the PI. Again, just trying to keep it fat for the Tele. (Only guitar I play with it.)

[RJ Guitars]

I switch between a 500pF and a .0012uF. The only time I use the "fat" setting is on my Tele in the bridge position. (There's a 4.7M resistor to ground to keep popping to a minimum.)

This amp also uses .1uF coupling caps in the PI. Again, just trying to keep it fat for the Tele. (Only guitar I play with it.)

Thanks Normster for info and the visual. I might try the 0.1uF in the phase inverter as well, I would also like to hear the extra bottom end in my amp. I am curious if that would bring a little more out of the 6V6's for me. I didn't feel like I was getting a really "full" sound out of them in comparison to the KT-66's or EL-34's.

thanks again,

rj

[Markusv]

This amp also uses .1uF coupling caps in the PI. Again, just trying to keep it fat for the Tele. (Only guitar I play with it.)

Thanks Normster for info and the visual.

+1 thanks Normster

I believe I will keep the PI coupling caps as is because of my love for humbuckers, and also I do not intend 6V6's for this build. Maybe another one later on.
Oh hell- who am I kidding- there will be others for sure!

Will try the switching treble cap if I can find space on the front panel, otherwise I may use a pull-pot for that boost setting

RJ-
Do you have any idea as to the ideal cab dimesions for 2X10?
I want to build a combo, but I would lke to size the cab such as not to lose any lows and mids

Markus V