The 6550 Experience

His guitar slung across his back, his dusty boots is his cadillac.

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daveweyer
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Re: The 6550 Experience

Post by daveweyer » Mon Apr 09, 2018 11:39 pm

Rather than a dynamic wave compressor, the circuit is an instantaneous inter-dynamic wave compressor, there is NO time constant, therefore there is harmonic addition as the amplitude of the wave is compressed on the integration rise per time of the line.
You could perform this function in totality and instantly with a diode--the (infinite) compression would make the wave a flat line over the time duration of the wave-- but that would be just what they do for death metal.
The tube wave compressor just tries to mimic a push pull power amp in saturation.

I'd have to think about how to provide a module; there is quite a hairy circuit that goes along with it because you have to switch the signal down in steps as you allow for less compression---the output from the 6KZ8 is over 300VAC and has to be divided by a hundred when the wave compressor is barely acting on the wave, and needs successive lesser division as the compressor eats up more of the signal. That's why I used a 6 position dual layer switch with those ladder networks.

niknik
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Re: The 6550 Experience

Post by niknik » Tue Apr 10, 2018 7:01 pm

daveweyer wrote:
Mon Apr 09, 2018 11:39 pm
The tube wave compressor just tries to mimic a push pull power amp in saturation.
Dave, I think this is the dream of all guitar players, at least my dream, an amp with controllable power amp saturation tone at any volume.
You've developed an amazing device, and please place it on the market if you can, I would be happy to buy it, and I think so many people too
:D
Sammy who?!

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Re: The 6550 Experience

Post by niknik » Sun Apr 15, 2018 8:50 pm

Hello guys,
I did some other mods in my major, folliwing the Dave's schematic, in more steps:
I swapped the dynaco ot for a Marstran jtm100 style 1202-132 with 2k2 primary, I installed 2 kt120s with 3ohm resistors tied each cathode, corrected bias circuit, and changed the main filter caps with 2x500uf in series
The power section now is pretty the same like in Dave's amp,
B+ is 550v (different transformer for now)
Screen supply is 407v
Bias is -60v
About 18ma each power tube cathode with 3ohm resistor.
At this point, the second gain stage is the same as stock amp, so I connected it directly to the tone stack.
I tested the amp, and I can say it is very powerful, clean tone is even better than before this mod, my strato never played so big and percussive and focused in all frequencies, I'm very happy.
At high volume setting, the amp crunches a lot, and although this is a big improvement than before in stock configuration, distorted tones are not so good like clean tones.
I know the run is not complete, so after this playing test, I tried a cathode follower arrangiament, with the v2 triode of the 12ax7 left free, and the tone is even better, even if only barely.
At this point the amp is very similar to a powerful Super Lead, with many upgrade.
But I like to go all the way, so after this, I took out the cathode follower, and I installed the bridged 12at7 with the sheen control, to drive the tone stack. So from the plate of the second gain stage, through a coupling cap, I connected a 50k volume pot (maybe I could stay with a 1m pot for now), and from there into the grid of the 12at7.
Here in Italy is late night, so I l'll test tomorrow.
I can say this is a very very silent amp, no hum from filament or bias, I am happy.
Except the 6kz8 and the wave compressor, I performed all the mods in the schematic. I also installed a separate filament transformer for extra tubes.
So after the tomorrow test, this exciting journey ends here, hoping in wave compressor news.
Like promised, as soon as I will do some clips of the amp in action.
Sammy who?!

niknik
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Re: The 6550 Experience

Post by niknik » Fri May 11, 2018 7:23 pm

I still am dealing with my major, now there is an extra gain stage after the tone stack to mimic the pi saturation, and after this stage I've put a master volume to the pi. I paralled the triodes of this 12ax7 extra stage, and the thing seems really interesting..
Plus I ordered a pt with correct specs for a Major, with 620 b+, I can't wait to install this!
Dave, for now I'm running a 2k2 100w ot with two kt120s, biased at about 18ma, can I go with four kt120s, or it is too much for a 100w ot? If I stay with two tubes, is better to mismatch the secondary impedence, like 8ohm into 16ohm cabinet?
Thanx :D
Sammy who?!

daveweyer
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Re: The 6550 Experience

Post by daveweyer » Mon May 14, 2018 4:17 pm

No, it's not too much. The extra tubes will add little to the output until their plate voltage is raised. (They pull around half the current each, a little more, so the output power stays fairly constant) To get more power from them you have to increase the cathode current--one way is to use the 16 ohm tap into an 8 ohm load. A 100 watt transformer can take a lot of power before getting in trouble; what you get is distortion, a special kind of magnetic saturation as the core cannot take any more "magnetism".

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Re: The 6550 Experience

Post by niknik » Mon May 14, 2018 6:53 pm

Thanx Dave!
When the new pt with 620 b+ will arrive, I will go with four kt120s, and finally I'll post some test clips :thumbsup:
Sammy who?!

daveweyer
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Re: The 6550 Experience

Post by daveweyer » Wed Jun 20, 2018 12:04 pm

Must be the summer doldrums, but Xplorer found a cool sounding pedal:

https://www.youtube.com/watch?v=rpUdHSr-m8w

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Xplorer
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Re: The 6550 Experience

Post by Xplorer » Wed Jul 11, 2018 7:53 pm

Ha ha , glad that you guys didn't move on too fast ! i was affraid to miss dozains of pages to read since the last time i could have some time to look.
Any clips from Shakti about the fuzz maybe ? will perhaps endly build mine in the weeks to come. Who will be first ? ;)

yeah, this keely monterey fuzz is quite a cool pedal, smart approach and nice sound.

shakti
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Re: The 6550 Experience

Post by shakti » Sun Jul 15, 2018 10:10 am

Too much to do at this time of year, but I am currently putting the finishing touches on a pedalboard with all the "Hendrix" stuff so once that is done, then... I do want to make a few tweaks to the fuzz to make it more pedalboard friendly. Would be cool to have it in a red fuzzface style enclosure, but not sure I want to sacrifice my Dunlop BOG fuzz for the cause.
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Xplorer
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Re: The 6550 Experience

Post by Xplorer » Sun Jul 15, 2018 7:56 pm

oh, a Dunlop bog fuzz into a west coast amp, and then Dave's original fuzz, clips about all of it that could be seriously interesting !
good luck with your pedal board.

revolver1
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Re: The 6550 Experience

Post by revolver1 » Mon Sep 10, 2018 6:54 am

Hi all, I need a bit of advice please.

I've got together all the bits I will need for a West Coast 50W 1987 but in my haste over looked an important aspect of the PT.

I got a Classic Tone 40-18054 because of the reports of its high plate voltage of 456v SS rectified. I neglected to check but it only has 220v or 240v primarys and my wall voltage is 230v.

From what I can suss out from other posts if I go with the 240v tap I should see approximately 440v on the plates and approx 6.2v on the heaters but I am more curious to try higher plate voltage.

If I go with the 220v tap for higher plate voltage I would see around 7v on the heaters so I would need to reduce the heater voltage back to around 6.3v.

I have ordered a selection of .1R, .12R, .15R and 2R wire wound 10 Watt resistors and as previously discussed will attempt a mixture of these in parallel between one of the heater wires and the first tube socket to attain as close to 6.3v across the tube heaters as possible.

A couple of questions though....

Is the wire wound resistor a good choice for this application?

Secondly, power rating. I probably have this completely wrong but is it;

W=V x I so, 7volts x 5amps = a potential 35watts?

Roe I think mentioned 3watt would do so is my 10watt completely over the top or will 2x 10watt in parallel be Insufficient for the job?
:shrug:

Thanks

revolver1
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Re: The 6550 Experience

Post by revolver1 » Mon Sep 10, 2018 8:04 am

Sorry,

Thinking about it, it's got to be 7v x current draw of the tube heaters?

I still don't know what that is?

Tek465b
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Re: The 6550 Experience

Post by Tek465b » Mon Sep 10, 2018 12:03 pm

P(in watt) = V²/R
With the resistor in parallel to the heater supply(that is WRONG)
7V² / 2R = 24.5Watt..
7² / 0.15R = 326 watt :!! (unless you want a smoke show .. :) )

With the resistor in serie with the heater supply.
Now if the heater chain draw about 3 amp...
V = A*R
3A * 0.15R = 450mV drop accross the resistor.
for the wattage of the resistor.
0.450² / 0.15 = 1.35 watt, so a 2 or 3 watt will do it.
Id probably use a metal film resistor over carbon film(drifting with temperature).
Wirewound is good too. :thumbsup:

revolver1
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Re: The 6550 Experience

Post by revolver1 » Tue Sep 11, 2018 2:26 am

Hi Tek, thanks for the response. That could have ended badly :oops: I really need to get into the maths a bit more, it would do me some good.

I will definitely put some pics up when it's done for some double checking.

I spent the day yesterday trying to figure out how to wire that P.T for 220v and still run the 120v lamp. I was pretty happy with myself when I figured it out.... Then I realised if I'm going to wire it to 220v and run it on 230v the 120v tap will be running too hot any way....

Better get a heater driven lamp.

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Re: The 6550 Experience

Post by Roe » Tue Sep 11, 2018 5:31 am

revolver1 wrote:
Mon Sep 10, 2018 6:54 am
Hi all, I need a bit of advice please.

I've got together all the bits I will need for a West Coast 50W 1987 but in my haste over looked an important aspect of the PT.

I got a Classic Tone 40-18054 because of the reports of its high plate voltage of 456v SS rectified. I neglected to check but it only has 220v or 240v primarys and my wall voltage is 230v.

From what I can suss out from other posts if I go with the 240v tap I should see approximately 440v on the plates and approx 6.2v on the heaters but I am more curious to try higher plate voltage.

If I go with the 220v tap for higher plate voltage I would see around 7v on the heaters so I would need to reduce the heater voltage back to around 6.3v.

I have ordered a selection of .1R, .12R, .15R and 2R wire wound 10 Watt resistors and as previously discussed will attempt a mixture of these in parallel between one of the heater wires and the first tube socket to attain as close to 6.3v across the tube heaters as possible.

A couple of questions though....

Is the wire wound resistor a good choice for this application?

Secondly, power rating. I probably have this completely wrong but is it;

W=V x I so, 7volts x 5amps = a potential 35watts?

Roe I think mentioned 3watt would do so is my 10watt completely over the top or will 2x 10watt in parallel be Insufficient for the job?
:shrug:

Thanks
7v sounds too high. 6.6v is more likely. Use some small dropper resistors. You get .1R and .22R metal oxide resistors on ebay
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