[Leadman]

Hello to everyone,

I have a 40 watt 2 x12ax7 + 4xel48 building based on a Marshall 2061x (solid stage rectifier and a DC coupled long tail phase inverter). I put in that desing a fixed bias circuit to run the amp cooler.
The amp sounds amazing and you can get a good decent level of headroom in the Bass channel (putting the tone an volume controls of the lead channel at three oclock without jumpering), it´s perform like a excellent clean pedal plataform. You can get a awesome crunch sound jumpering channels and turn the volume up, but you get a lot of volume for   normal stage gigging. I have used this amp about two year without problems.
Now, I am going into no drive pedals and control the overdrive with the guitar volume and tone pots. Watching a lot of web info I have discovered that Komet k19 (or k29) goes in that way. Studing the inside pics on the net from the komet k19 k29 looks like the power amp topology is very similar to marshall 2061x but put a two stage cascade preamp into the Phase Inverter but the component values are not shown in the pics.
Do Anybody have any idea of how to MOD the 2061x schematic into a Komet 19/29 style amp or the correct values or schematic for that amp?
There is a mod running in the net called "swank Motee" that cascade one channel into the other, but I don´t like the way is implemented with two tone controls.
Another suitable desing could Be a Budda TwinMaster, but it don´t have a master volume and I´m afraid that push that amp into overdrive could be too loud with a 40watt watts power amp, and the plate voltage will be lower than my clone because I don´t use tube rectifier. Otherwise I am not sure about the correct schematic and values.

Thanks in advanced for your help.

Best Regard from Spain.

[mike45]

Hi Leadman,

some years ago i build a Komet19 Clone for a friend. I have drawn a schematic from a gutsshot of this amp. Hope you can use it.

Mike

[Leadman]

Thank you so much!

Best Regards.

[Leadman]

Hello again, how do you get the correct components values? I´m looking the picture and all the resistor are covered.

Best Regards!

[Leadman]

I have built the amp. The dual bright switch was omited, not bright cap was used. The amp is very trebbly and gainy. I have put a higher value snubber cap and now it's a bit better.

Some more ideas?

Best regards.

[Mr. Lime]

Danke für den Schaltplan!

Exciting, seems to be some kind of hot rodded 5e3 with replaced PI.
How about a James tone stack to have better control over bass frequencies?
Also a Vox High Cut control could be useful if there's place left on the front panel!
Should work just fine as no global feedback is used.
I would even consider adding an EF86 channel to the second input of the PI as both channels could be used parallel.

[Mr. Lime]

Den K19 fand ich schon vor Jahren recht spannend. Ich hätte da aber eine Frage bezüglich hinzufügen eines Mid Cut Reglers.
Wo würdet ihr ihn platzieren?
Der K19 (wie auch ein 5e3) lebt ja von dem geringen Verlust des Tone Stacks und ich überlege, ob man den Mid Cut vor dem Volume/Tone Regler oder besser danach einfügt?
Eine weitere Überlegung wäre, das RC Glied nach dem Saturation Regler umzubauen, somit wäre der Mid Cut erst nach der 2. Stufe und würde wohl weniger Höhenverlust verursachen?

Hatte mal einen Mid Cut nach der 3. Stufe eines DIY Komet Concorde probiert, was für mich überhaupt nicht funktioniert hatte. Wie seht ihr das beim K19?

[Leadman]

I have rebuilt the "komet 19" into a Super Pro Junior style amp with tone stack and some mods.
I have tested that design (k19) and it is not for me, maybe some values are not 100% accurate. The amp don´t sound like a komet 19 for me.

Best Regards.

[Mr. Lime]

Interesting,

what do you feel was missing or didn't work out as hoped?

The 2n coupling cap after the second gain stage might be too small?
Also I think I see a resistor going to ground right after the whiper of the saturation control instead after the 470k/500p, see the gut shot.

[Leadman]

Yes, I rebuild the amp with the second coupling cap a 0.022uf coupling cap, the amp sounded better but not as a Komet 19 for my ears.
The amp don´t clean up with guitar volume as it would be desired.
You are correct, something is wrong in the voltage divider, it would be that missing resistor to ground...

Best Regards.

[Mr. Lime]

Now I'm working on that circuit as well and got some problems with blocking distortion.
Already added 33k grid stoppers on 2nd stage and PI without success.
The mid control I suggested is put on a switch but doesn't contribute much to the tone.

I agree that it's quite bright with poor bass response.

[darkbluemurder]

The issue with all the Trainwreck inspired amps is that the compression of all stages going into overdrive is a part of the design - that way you can set the amp so that your guitar sounds overdriven cranked and by digging in and then can be cleaned up by lightening your touch and/or backing off the volume control, and due to the compression having the clean tone not lose volume. The downside is that setting the amp this way is freaking loud -even with only two small tubes like 6V6s or EL84s. If you cannot crank the amp to that point it is not working as intended. A master volume does not help much as you will lose the power amp and power supply compression.

This is my experience from having built a Liverpool Light (only two EL84s in the power amp) and later converting the preamp to the Komet specs.  With the search function you can find both threads. The preamp by itself is bright and has a lot of hiss, even at low volumes. It is a very specialised design for sure.

Probably the best way to solve the loudness issue is to include a VVR. Maybe the guys who built one with a VVR can chime in?

Cheers Stephan

[darkbluemurder]

I have also heard that using the right cab is critical.  A 4x12" would be good as the signal is spread to four speakers, thus bringing the volume down a bit. A 4x10" would achieve the same thing but as the amp is bright you may want the additional low end the 4x12" can provide. And I would recommend inefficient speakers to further bring down the volume.

[Mr. Lime]

I had some frustrating hours with my amp but finally found the error causing nasty distortion.
The schematic is missing a PI input cap.
Now that I added one I got the sound I was expecting.
It is a very bright amp and I understand what Leadman wrote about.
I have added a conjunction filter like a VOX Hi Cut which helps but the amp still needs some tweaking.
VVR is also included.

Like Stephan wrote the speaker is critical as well. Probably because of the PA that has no negative feedback.
I didn't like it with my Jensen Blackbird but had good results with a Mesa VS-12.

[Leadman]

Any final schematic about that design?

Best Regards.