Practical tips for adding LED rate indication to trem circuit?

[Lowerleftcoast]

The Hot Rod Deluxe uses a bi color red/grn. When both are lit it is yellow. If this replaced the lamp it could be wired to have green always lit. When the red would strobe, it would alternate green - yellow - green - yellow.

 

[King Fan]

The Hot Rod Deluxe uses a bi color red/grn. When both are lit it is yellow. If this replaced the lamp it could be wired to have green always lit. When the red would strobe, it would alternate green - yellow - green - yellow.

Interesting. Is that a single 'bulb' with two LEDs in it? I'd have to wire in constant power *and* the trem cathode? True, I see you can get colored LED bulbs that fit 6V bayonet lamps. But they still look big enough it’d be hard to fit a little LED alongside.

In any case, I’m not eager to go multicolor. I’m old enough to remember vari-colored, lit-up disco floor tiles pulsing in time with the music. Bad memories…

 

[Lowerleftcoast]

Is that a single 'bulb' with two LEDs in it? I'd have to wire in constant power *and* the trem cathode? True, I see you can get colored LED bulbs that fit 6V bayonet lamps. But they still look big enough it’d be hard to fit a little LED alongside.

Yep, A single looking LED with three legs. One leg for constant power and a leg for the cathode. A traditional sized bulb would not be used... just stuff the LED up in the lamp holder.

Goodbye Sister Disco
With your flashing trash lamps
Goodbye Sister Disco
And to your clubs and your tramps
Goodbye Sister Disco
My dancing's left you behind
Goodbye, now you're solo
Black plastic; deaf, dumb and blind

Pete Townshend

 

[King Fan]

.

Goodbye Sister Disco
With your flashing trash lamps
Goodbye Sister Disco
And to your clubs and your tramps
Goodbye Sister Disco
My dancing's left you behind
Goodbye, now you're solo
Black plastic; deaf, dumb and blind

Pete Townshend

‘70s memories? The (1973) song says,

“What's too painful to remember
We simply to choose to forget…”

I wish I could choose; sometimes they’re “too painful to forget.”

The 10 Worst Songs of the 1970s

You chose to include ‘Billy Don’t Be A Hero,’ ‘Disco Duck,’ ‘You Light Up My Life’ and more

www.rollingstone.com

 

[Lowerleftcoast]

‘70s memories?

One of my jobs in college.... wedding band drummer. Paid reasonably well. Most weekends were, Friday evening, Saturday noon, and Saturday night weddings. That is a lot of "Color My World", "Three Times A Lady", and "Do The Hustle", but it kept me from doing other jobs. I call that a win.

 

[King Fan]

LEDs are incoming, USPS. Any day now.

To be continued…

 

[Bill Moore]

Funny Lowerleftcoast, when my wife's sister got married, her friend hired a band from El Paso, but showed up with no drummer, I got elected, and that was the first time I played "Color My World"!

 

[King Fan]

Slight update. While I'm waiting for my commercial orders, a super-nice member here sent me some cool little 3mm LEDs to test. They're cute, they're pretty (and pretty darn bright) -- and I was able to measure the voltage of each in my VibroChamp which had volunteered to be a test bed...

Red​	Yellow​	Blue​	White​	Green​
1.7V​	1.8V​	2.6V​	2.6V​	2.7V​

Would these minor voltage differences make any difference in the trem circuit? No idea. Tho I'm willing to be instructed.

These are the little LEDs that all look white until you power 'em on. Apparently they're super-brights -- seen head on they're actually more intense than the conventional 5mm LEDs I had.

Oh, and the conventional 5mm reds also measure 1.7V. What about the VC itself, with its standard resistor and capacitor? *Also* 1.7V. That's OK with me... red seems the least disco.

 

[King Fan]

Well, that wasn't too hard. I decided to go with the less-blinding 5mm red, especially given the black faceplate on my 'reverse-tux' 6G2 -- I found some black plastic 5mm bezels, which blend in better than the 3mm chrome ones.

Drilling the hole in the faceplate wasn't hard. The 6G2 is easier, cuz I built it in an aluminum chassis. I concocted a goofy little tape trap (sticky electrical tape, stickum facing in) all around the drill site inside, which actually worked well.



The LED isn't blinding or painful to look at amp-on, and amp-off, it's not obtrusive.

The wiring wasn't complex, either (see layout in the first post).

So not bad. But all that said, I'm now gonna try this out in actual practice. Is the game worth the candle? Because I couldn't figure out how to add an LED to the pilot light in the vintage VibroChamp, it was spared any LED surgery. And I'm thinking this isn't likely worth it in the 5G9, where the tweed control panel is less visible and the chassis (ow ow ow) is stainless. But it was a fun project, and the 6G2 is an amp where I use tremolo more than most, so I'll be interested to see if the visual indication is a big deal or a meh before I consider whether to do the (clone) PR.

But let me say this would be *super* easy if you added it to an amp in the building process. Big thanks to all of you for your help and interest.

 

[King Fan]

Played a bunch with trem last night. Besides looking kinda cool, the LED was surprisingly helpful. Not only in setting slower tempos to match what you want to play, but also for staying 'in synch' once you're playing.

Final thoughts? Appearance, though cool, isn’t period correct on a clone. A 1962 amp with an LED? But that's about it on the 'con' side. OK, in an existing amp, you also want to be comfortable unsoldering (no big) and drilling (urgh).

Though the 'pros' aren’t massive, they’re real. Plus I like the fact, still slightly surprising to me, that an LED can do the work of a resistor-capacitor pair here. Would I do this if I were building a tremolo amp in the future? Yes.

 

[Willie Johnson]

Maybe it would be cool to put a big blue one in the back of the amp cabinet somewhere and have an ambient flashing from the guts of the amp. My uncle had a 6g2 whose power tubes were very blue plasma/gassy, and in a darkened room there was a pulsing glow in time with the tremolo.

 

[King Fan]

Thanks, USPS. Those nice Dialcos mentioned by @corliss1 finally arrived. Wow. They get *multiple* wins in the LED Grammys; best lead length (14”), only lead length (!), no soldering to whiskers (yay), LED protrudes beyond bezel for visibility from the side (like the 5mm ones), and, it turns out, by far the smallest hole to drill.

 

[corliss1]

I wouldn't steer you wrong

 

[King Fan]

Oh, and it isn’t clear from the pic, but the center rig is the 3mm bezel I showed on page 1. The threads increase the hole size some, tho I’m sure the nut adds some security.

 

[chas.wahl]

Mouser sells that Dialite LED for half what TubeDepot charges, and they have the datasheet too, with other types:

 

[Bill Moore]

I happened to think that an LED could be mounted out of sight, and move the light to a viewable position with fiber optic! (Maybe the small gap between the chassis and the baffle.)
Back in the 70's-80's GM pickups lit their ash trays with a fiber optic from a dash light in the instrument cluster.

 

[King Fan]

I happened to think that an LED could be mounted out of sight, and move the light to a viewable position with fiber optic! (Maybe the small gap between the chassis and the baffle.)
Back in the 70's-80's GM pickups lit their ash trays with a fiber optic from a dash light in the instrument cluster.

Bill, that sounds brilliant. (Sorry, pun totally an accident, I swear.) Do you (does anybody) know of a product designed to “port” light from an LED to a nearby location?

In any case, thanks once again, my friend.

 

[King Fan]

Mouser sells that Dialite LED for half what TubeDepot charges, and they have the datasheet too, with other types:

Thanks, yeah, I actually got the datasheet on page 2 from them or Digi-Key or somewhere.

 

[chas.wahl]

If it's a combo, or a head with grille cloth, maybe an LED mounted in the baffle right behind the grille cloth (having decent openness) would be sufficiently visible, without being a permanent fixture. In that case, a somewhat larger-diameter LED might work better than a tiny one.

 

[G Stone496]

I like my trem amps (5G9, 6G2, PR, VC) but it'd be handy to have a visual rate indicator. Merlin shows us how -- *on the schematic*. He says: "By replacing the cathode resistor with an LED we eliminate the need for the large bypass capacitor, and obtain maximum gain and minimum output impedance at all frequencies in one fell swoop. A red LED will be suitable in most cases... the LED will flash in time with the trem' signal... the circuit (drawn) shows this, using an ECC81 this time."

Here's the base drawing:

View attachment 1077266

and here's the LED version:

View attachment 1077267

I'm guessing the ECC81 isn't a necessary part of this mod. But I'm left wondering how to do this in an actual amp, in layout space.

Take the 6G2 for example.

View attachment 1077278

1. Lemme confirm: the LED goes on V2 pin 3, yes?
2. Would I have to drill a hole in the faceplate for the LED? *Or* I've heard you can position the LED to shine in next to the pilot bulb so the pilot light will pulsate with the LED. But that seems like a long wiring route -- and like it'd be darn tricky to orient the light(s).

Any practical experience or advice would be welcome.

Yeah a visual cue like a flashing light would be cool as an aid for the count in. The tricky part with using trem in a song is that hopefully the drummer hears the pulse of the amp trem well enough to keep time to it throughout the whole song. A flashing light might also benefit the drummer. I’ve always had better luck staying in time to the trem when recording. It’s a little harder to hear and use as a pulse for keeping time during a live show.