trinityamps.com

Ceri@tone modifiactions are described on Ceri@tone's forum in a "New Lightning Layout - Special Announcement" thread.

Of all the mods mentioned, I'm interested in "change of resistor from 22K to 4.7K as filter decoupling to cathode follower V2 stage".

Why that resistor? Why not playing with paralleled V1? When paralleling an 12AX7, sometimes I see halving of anode resistor's, cathode resistor's and cathode cap's values (R4, R5, C2 on Trinity 15 schematics).

I'm asking because I'm interested in the possibility of reducing "harsh" distortion from Trinity 15.

Thanks in advance and also thanks for a great forum and great projects!

I suspect it's to give that stage more headroom by increasing the plate voltage.
Stew

I have no idea. I hope Nik know what he's doing here. The Lightning is a very well-proven design, and you don't usually hear complaints about it.

That's quite possibly true. But I wonder why would anyone feel the need to do that....

There isn't usually enough signal level present at the first preamp stage of an amp to overdrive it. So the component values at the first preamp stage are usually the least critical of any of the stages.

Not very often. If you halve the cathode and especially the anode values when paralleling triodes in a 12AX7, you keep the stage gain about the same, while reducing the output impedance. Sometimes that's useful fro driving a tone stack. However, if you keep the same resistor values as for a single triode, you get an increase in gain of around 1.3 times the gain of the single cathode stage. You see this with Marshall 18W type amps as well as Matchless style amps.

You're the first person I've heard say they were getting harsh distortion from their TC-15. To me it sounds likely that something isn't 100% OK in your amp. Have you gone through and checked all the voltages? Also what kind of an OT are you using. Is it from Trinity, or is it from a local source? Are you using good quality tubes?

The only thing some folks might possibly want to tweak, in common with many Vox and Matchless amps, is to reduce the 1.2k cathode resistor in the PI to 820 ohms, to help reduce the possibility of getting some fizziness at certain settings. Ken Fischer has also been known to use 750 ohms for that resistor in some of his Vox-like TW Rocket amps. But apart from that, as someone once said about the TC-15, it's hard to improve on perfection.

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Great tones come in small glass jars!

Thanks, a great post!



Voltages are fine, OT comes from a local source, the tubes... are therefore the main reason for harshness, it seems. Speakers are so-so as well.

OT, speakers and tubes. Those three have the biggest effect on an amp's tone by far, and any of them could make even a great amp sound harsh.

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Great tones come in small glass jars!

I just finished building a Lightning using Ceri@tone's 4.7K dropping resistor value for V2, and bright cap on the master volume. Needless to say I yanked those out quick and put the stock value of 22K in. I think the increased voltage on the CF made the amp sound hard, with raspy artifacts. And the Bright cap on the MV was, for lack of a better description, "very noticeable" and IMO just not needed.

I'm using standard 18watt trannies with an 8K primary and Nik's OT may be mismatched, so maybe that's why I had bad results.

Nevertheless, I would like to know why he felt those changes improved the amp.

In a regular Lightning from Matchless the load impedance would be 4k. You can achieve that by running an 8 ohm speaker on your OT's 16 ohm output tapping, or a 4 ohm speaker on the 8 ohm tapping.

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Great tones come in small glass jars!

Your so right phat head.
Nik is the coolest guy ever but that one has me guessing as well.

I also went back to the 22k dropper and only 50pf on the brite cap.
I'm using an 8k OT and CLC filtration before the B+ hits the rail.

With a little tamer PI and series or parallel triodes on the inputs,
a V2A cathode cap bypass switch and the PI trim control that I just added recently, I can get everything from sweet and smooth to a creamy crunch.
If I didn't like building amps so much I'd stop right there.
But alas my single ended KT66 project is calling, solder me, solder me....

The 4k7 resistor was used in an early Lightning schematic in a file called "matchless_lightning15.pdf" . IMO, I think it is a mistake because in that schematic it also shows the screens are fed from before the choke.

FYI here's some more information I gleaned a few years ago, and had saved in a text file on my hard drive. I'm sorry I don't have the original URL of wherever it came from....

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Great tones come in small glass jars!

Hey
that's just rerally incredible to know
thank you truly
I love reverse engineering ... well.... everything

Thanks for the info

I finally finished college and I'm wanting to start learning about amps. This looks like a good place to start. I got a Ceri@tone lightning ahwile ago, and it's pretty awesome, but it could be a bit better, and I want to play with it. i see the cap on the master volume, no problem, but what we're saying here is that 4.7 K resistor by the filter caps should be a 22K like the other two?

According to the experts I quoted from above, the power supply should be done the same way as with a Matchless Spitfire - see http://www.schematicheaven.com/newamps/ ... itfire.pdf

And congratulations on completing college!

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Great tones come in small glass jars!

zaphod - You probably didn't realise but there are 2 different schematics in the link you posted. The first redrawn schamatic is correct but the power supply arrangement is wrong in the second (hand drawn) one.

So I replaced that master volume cap with a 100 pF and that 4.7K resistor with a 22k, and my amp sounds much, much better. It was nearly there before...now it's there. Much more clarity and punch.

I decided to revisit my Lightning build and was looking on the net and found this gut shot. It clearly shows the 4.7K resistor feeding the CF stage. It also looks like 5 filter caps with the 250uf cathode cap buried in there somewhere. So it looks like Nik is replicating this version. One thing I did to mine that really brought the tone together was add a shared 1K 5W feeding the 100R screen resistors, this got the screen voltage under control a little better. So maybe I'll try the 4.7K value again and see how it sounds.

It's easy for me to know.

Territorial io

The specific modification you mentioned, changing the resistor from 22K to 4.7K as filter decoupling to the cathode follower V2 stage, is described as a way to reduce "harsh" distortion in the Trinity 15 amplifier.
In an amplifier circuit, the decoupling resistor plays a role in filtering out any unwanted noise or interference from the power supply. By changing the resistor value from 22K to 4.7K, you are essentially altering the filtering characteristics of the circuit.
Rainbow Friends: Chapter 2