6L6 rocket

[tweedeluxe]

Yeah I know that threw me off too. Not used to seeing 220k.

Glad to hear that a series resistor is not necessary with the 25k pot. Thanks for your help, Zippy & Markus. Can't wait to fire up my KT66 Rocket.

[RJ Guitars]

Reading about this amp makes me feel like a proud parent... these are very cool amps.

One note of caution, if you ever try the KT-66's you might find that most other tubes start to seem kinda ordinary. However, I have found that hot running EL-34's are also a pretty sweet choice in my amp.

The best deal is if you can find some guy that has a couple KT-66's sitting around and has no time to build amps but is so curious how they sound that he "loans" them to you... oh sorry Zippy I'll be bringing those tubes back very soon ( not likely ).

Well of course I would like to know what transformers and voltages, what kind of biasing, how hot do you bias her, etc., and how this new rig sounds in comparison to the the "standard Rocket".

rj

[Markusv]

RJ

You da man!
You may remember that you and I corresponded via this forum a while ago. Well that got me going

Main reason for an Octal rocket is that I don't want yet another el84 amp
I have a Liverpool (which is tough to beat), a traynor clone, an 18 watt marshall clone and a P1 from ax84
All small bottles

I wil eventually get all voltage etc. but here ar the main things:
320-0-320 into a 5u4
No choke- 500R wirewound instead
Standard after that except half the dropping resistor value to the 1st stage

Cathode biased as per the schematic with a "ballpark" 200R resistor on the power tube cathodes

Tubes are 6L6GC made in china and old- probably somewhat tired

CHANGES:
Mid control added =25K (Glad I did)
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

I was pretty happy at clean levels but when I crank an amp I want it to punch me in the gut. It did not quite do thatt. Breakup was OK but uninspired and I kept on getting an "underpowered" sense
Slapped a 10UF electrolytic on the second stage cathode

HOLY Son of a whatsisname!

The amp opened up on all levels!. Everything is just "more"
Of course now the amp breaks up quicker, but the touch sensitivity is through the roof comparatively. I can get good sparkly cleans at decent volumes but oh man when I crank the amp, it absolutely shines.

In short, I attribute these improvements mainly to the brite cap and the bypass on stage 2

One reason for the previous lack of punch may be the output tubes- perhaps they are a bit dark and they may need more to push them into an ideal region of operation

I don't know whether this is still truly a rocket, and more tweaks will
follow but thus far a very satisfying amp to play..

One question
My PT's filament windings are rated at 5A- I assume the shuguang KT66's will not present a problem?
I believe they are thirsty suckers for current

Best regards and thanks for all your support, moral and intellectual
Markus V

[Markusv]

Double post

There are server problems it seems

[Markusv]

Double post sorry

[Zippy]

CHANGES:
Mid control added =25K (Glad I did)
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

I was pretty happy at clean levels but when I crank an amp I want it to punch me in the gut. It did not quite do thatt. Breakup was OK but uninspired and I kept on getting an "underpowered" sense
Slapped a 10UF electrolytic on the second stage cathode

HOLY Son of a whatsisname!

The amp opened up on all levels!. Everything is just "more"

We like more.

One question
My PT's filament windings are rated at 5A- I assume the shuguang KT66's will not present a problem?
I believe they are thirsty suckers for current

Check this review for comments regarding heater current:

http://thetubestore.com/kt66reviews.html

"Shuguang KT66 - The Shuguang is functional art. A great job has been done in nailing the look of the original KT66. This is a huge tube when compared to others used in guitar amps. You are advised to have a careful look at space availability before installing these guys. The specs on this tube are very similar to the 25-watt originals. They draw more heater current than a standard 6L6: 1400 ma. instead of the usual 900. You should be sure that your amp's power transformer has the capacity to handle the extra current draw. Bias these tubes hot for best results. While most tubes we tested were biased at around 60% of their rated plate dissipation, the Shuguangs sound very bright and crystalline in this range. Some may find it too bright. At 75% of rated dissipation, these tubes really provide that feeling of rolling thunder. If you want Country clean, bias them for 60-70%. If you need earlier breakup and a beefier sound then turn up the heat, but keep an eye on your power tranny."

[RJ Guitars]

...I wil eventually get all voltage etc. but here ar the main things:
320-0-320 into a 5u4
No choke- 500R wirewound instead
Standard after that except half the dropping resistor value to the 1st stage

With that 5U4 you are dropping a few volts but still hitting everything with more B+ than I am. I had some 280-0-280 trannies special wound for some future iterations and your work makes me believe I could increase the headroom a bit with the extra juice... and it will still sound good.

I was pretty happy at clean levels but when I crank an amp I want it to punch me in the gut. It did not quite do thatt. Breakup was OK but uninspired and I kept on getting an "underpowered" sense
Slapped a 10UF electrolytic on the second stage cathode

HOLY Son of a whatsisname!

The amp opened up on all levels!. Everything is just "more"
Of course now the amp breaks up quicker, but the touch sensitivity is through the roof comparatively. I can get good sparkly cleans at decent volumes but oh man when I crank the amp, it absolutely shines.

In short, I attribute these improvements mainly to the brite cap and the bypass on stage 2

I had the same experience with that 2nd stage bypass cap... things got very cool when I did that! This is a noteworthy deviation from my EL84 "Rocket" amp. I definitely did not like the 2nd stage bypass cap on that amp.

One reason for the previous lack of punch may be the output tubes- perhaps they are a bit dark and they may need more to push them into an ideal region of operation

I don't know whether this is still truly a rocket, and more tweaks will
follow but thus far a very satisfying amp to play..
Markus V

I may sound like a broken record but the KT-66's took me another level higher... they have all the good qualities of the EL84's but just more of everything good. Eventually I found that very hot running EL34's were also a good choice.



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!

Finally, I can't really say I invented anything really novel here. Normster and RF Gordon both built 6V6 Rockets before I did... as well as a lot of other guys I probably don't know about. I just tried to imagine what direction Ken Fischer might have experimented if he hadn't got sick.

There are a few more of these amps in the works by various guys across the forum and I think we'll see and hopefully hear some more cool results soon.

rj

[Zippy]

With that 5U4 you are dropping a few volts but still hitting everything with more B+ than I am. I had some 280-0-280 trannies special wound for some future iterations and your work makes me believe I could increase the headroom a bit with the extra juice... and it will still sound good.

How 'bout plugging in a solid state rectifier?

[RJ Guitars]

With that 5U4 you are dropping a few volts but still hitting everything with more B+ than I am. I had some 280-0-280 trannies special wound for some future iterations and your work makes me believe I could increase the headroom a bit with the extra juice... and it will still sound good.

How 'bout plugging in a solid state rectifier?

Matter of fact, tht's whats in there now....

rj

[Zippy]

Must be time to set aside the LP and 339 and plug in some P-90s!

I'll dig this out One More Time:

http://thetubestore.com/kt66reviews.html

"An Epiphone Casino was used for guitar since the P-90 pickups are right..."

[dr. who]

Any soundclips coming?

[Markusv]

Any soundclips coming?

I do not have recording equipment right now
I may go past a buddy's studio in future and record some- then I will post

M

[Markusv]

With that 5U4 you are dropping a few volts but still hitting everything with more B+ than I am. I had some 280-0-280 trannies special wound for some future iterations and your work makes me believe I could increase the headroom a bit with the extra juice... and it will still sound good.

How 'bout plugging in a solid state rectifier?

Matter of fact, tht's whats in there now....

rj

Well- I was considering solid state rectification, but I never built a tube rectified amp before, so I wanted to keep it that way. Plus I had the 320-0-320 secondaries, so no lack of B+ even with the rectumfrier.
I think I do feel the difference betweent the 2 modes of rectification.
My Liverpool for example is very "fast"? no other way to describe it and the Rocket seems to have a gentler, softer attack. Not sluggish in any way though, but I think besides the fact that it is lower gain, that is what lends it so well to rythm playing. You can noodle on this amp for longer than the liverpool, which seems to say: "shut up and play- preferably loudly"

I do still think you could go with the solid state jobby if you like but perhaps you may have to alter dropping resistor values along the way to the pre-amp

RJ...

did you notice that the testbed for the KT66's was in fact a '59 Bassman restored to vintage spec?
No wonder the Shuguangs sound good in your amp!
I was going to build a Bassman originally, but that will be the next project if someone can convince me that this beastie doesn't cover Bassman territory somewhere in its tonal spectrum.

Markus V

[Zippy]

did you notice that the testbed for the KT66's was in fact a '59 Bassman restored to vintage spec?
No wonder the Shuguangs sound good in your amp!
I was going to build a Bassman originally, but that will be the next project if someone can convince me that this beastie doesn't cover Bassman territory somewhere in its tonal spectrum.

Did ya see this earlier in this thread?

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. Most everything else is flavor tweaking. I love ol' tweed amps so I am especially warm to the Rocket derivatives. I'm leaning on RJ to spend some time with the single coil guitars next. I've got a G&L ASAT Junior that should be a real hoot (recall that Derek reports Ken having a preference for single coil pickups).

Keep up the great work. This, at least from my myopic perspective, is one of the most fun 'wreck projects yet!

P.S. Try running the KT66 Rocker through some 10's.

[Markusv]

So, yes, that's the vibe - I think the biggest change is tweaking the cathode follower for some gain/compression. Most everything else is flavor tweaking. I love ol' tweed amps so I am especially warm to the Rocket derivatives. I'm leaning on RJ to spend some time with the single coil guitars next. I've got a G&L ASAT Junior that should be a real hoot (recall that Derek reports Ken having a preference for single coil pickups).

Keep up the great work. This, at least from my myopic perspective, is one of the most fun 'wreck projects yet!

P.S. Try running the KT66 Rocker through some 10's.

Well- with single coils this is a totally different beast- Of course the eq is way different on the amp and it takes some getting used to. The harmonic content is astounding. It's almost like having a tiny amount of reverb added
The hot input (parallel) is great for single coil, but the lower input has its own charm. very voxy I would say.

Your perpsective may be myopic, but there is truth there.
This is an easy amp to build, but it has a lot to give and is not a one-trick pony. Also in terms of wreck realities, it is more forgiving so I think this is a tweakers amp. My Liverpool punishes me for the least interference with lead dress etc by becoming unstable, more noisy etc.

I am curious to the 10 inch speaker suggestion.
I have some organ pulls here that may serve- what were your observations?

Markus V