Bright caps

CKsam

Having helped a friend snip a bright cap out of his amp this weekend (Crate Vintage Club VC30), it made me wonder: does anyone who know's they've got one in their amp like it that way? In my experience, they murder the tone at low volumes, and do very little at higher ones.

My Blues Junior is much better without its bright cap, which dominated when the gain is low.

Sam

ecc83

YCPAOTPAOTT! Such a capacitor might have been fitted as compensation? When you have several hundred kOhms of pot track in series the input capacitance of the next valve grid can chop a lot of top. When the pot is inserting only 50k say, not so much. The problem I guess is that like SO many valve amp circuits, mistakes were just copied slavishly so a cap value that worked with say 220kpots is too extreme with 470k and even worse with 1meg. 

A simple response measurement would tell the manufacturers if the value was right but do they all bother? Seems not. 

Then, swapping a speaker can make a dullish amp sparkly even ice pick! And of course, people's lugs vary tremendously. 

Dave.

stickyfiddle

I much prefer amps with them. I have my TM Deluxe Reverb set to include a digital bright cap, and I even added a real-life one to my Cornell Reverb. 

But I'm aware I do like my gear much brighter than most people seem to

ICBM

I much prefer them too, except when the value is too large (eg most non-MV Marshalls). Without one, the tone is usually too dull and lacks sparkle at low volume, and doesn’t work in a band mix.

In my opinion the Blues Junior is too muddy-sounding anyway, so I wouldn’t want to remove it. But everyone has different tastes… I dislike ‘smooth’ midrange, and my idea of sparkle may be your idea of shrill.

CKsam

Interesting! I guess it also depends on the guitar, pedals and amp settings. I'm 100% single coils in my guitars, and like sparkle. What I don't like is a thin tone, which is what I've found with bright caps at lower volumes.

On the Blues Junior, I hear more complaints about ice-picks than mud, though it certainly can get muddy when the gain is up, but at that point the bright cap's doing very little. Mine has a Greenback in, and sounds great to me without the cap.

Sam

Supportact

I'm sure there's one in my Vox AC15CC, I remember reading about people removing them when I was looking into changing the speaker.  Based on people's opinions on the Internet,  it's either an essential mod that will solve everything or totally pointless.  I like the way the amp is now with the new speaker so I've left it be. 

Stratavarious

Push pull knob with two values on my JMP.. let’s me dial in exactly enough bright at different practise/gig levels or if I use pedals through it. 

Alex2678

I’ve added one to my 68 custom deluxe, the deluxe reverb value is subtle but I do definitely prefer to have it 

maharg101

I don't have any in amps.

I have a Secret Preamp pedal last in the chain, and use the bright setting for low volume vs the mid setting for higher volume. 

Jonathangus

Stratavarious said:

Push pull knob with two values on my JMP.. let’s me dial in exactly enough bright at different practise/gig levels or if I use pedals through it. 

2204?  Do you find that the effect of the bright cap is changed at different master levels, or just pre-amp gain?  I usually run the pre-amp fairly high (7-8) so it should have less of an effect.

ICBM

Jonathangus said:

2204?  Do you find that the effect of the bright cap is changed at different master levels, or just pre-amp gain?  I usually run the pre-amp fairly high (7-8) so it should have less of an effect.

The bright caps (there are two, one on the pot and one on a fixed resistor) in the 2203/2204 are on the preamp volume (gain). There isn’t one on the master volume.

I especially like it on these amps because it makes cleaner sounds brighter, which is what you usually want. As you turn up the preamp volume the overdrive adds more high harmonics anyway.

Stratavarious

Jonathangus said:

Stratavarious said:

Push pull knob with two values on my JMP.. let’s me dial in exactly enough bright at different practise/gig levels or if I use pedals through it. 

2204?  Do you find that the effect of the bright cap is changed at different master levels, or just pre-amp gain?  I usually run the pre-amp fairly high (7-8) so it should have less of an effect.

Yep. 50w master lead II from 1979. 

It’s on the input gain.. at low volumes and lower gains JMPs can be a little too bright. As you up the input gain, the effect of the cap reduces.  Same with volume..get it loud and a JMP has a classic roar.  

Making it switchable, gives me max range of useful tones for single coils and humbuckers at different volumes and it’s particularly practical to reduce the edge if using my JMP with some pedals for cover band stuff.  Better than just clipping it is to have a couple of values you test using croc clips before soldering. 

CKsam

Switchable is ideal, I can see that. But as an easy mod for an amp which is being used mainly at low settings on the relevant dial and sounds thin, I'll be clipping it all day long. But I'm glad to find they're not universally unpopular!

ICBM

Switchable values is a good idea. The problem with just removing it is that it usually sounds worse - too muddy - and you can’t compensate for that by turning the guitar tone control down, like you can if it’s too bright.

Winny_Pooh

Hated it on a super lead, made low volume playing with OD pedals a pain. Clipped it and never thought twice. 

CKsam

ICBM said:

Switchable values is a good idea. The problem with just removing it is that it usually sounds worse - too muddy - and you can’t compensate for that by turning the guitar tone control down, like you can if it’s too bright.

Is there a difference between bright and thin, though? Does rolling off treble on the guitar compensate exactly for the treble-bleed of a bright cap? Maybe it does, but my ears would need some convincing!

ecc83

CKsam said:

ICBM said:

Switchable values is a good idea. The problem with just removing it is that it usually sounds worse - too muddy - and you can’t compensate for that by turning the guitar tone control down, like you can if it’s too bright.

Is there a difference between bright and thin, though? Does rolling off treble on the guitar compensate exactly for the treble-bleed of a bright cap? Maybe it does, but my ears would need some convincing!

Now you are delving into the murky world of psychoacoustics! Yes, boosting treble CAN appear to reduce bass content just a s boosting bass seems to dull the top end. 

The boost cap across a fixed resistor is a rather different situation. This is often done to boost HF from the earliest, cleanest stage where the signal is strongest because of losses further on in the pre amp chain. Not only can this make up for treble loss but also reduce noise bit (see " pre and de emphasis for FM radio"!) 

The cap on a pot is always a compromise since its effect depends on the actual setting of the pot and can only be "right" for one of them. 

Switched values? Good thinking Batman! Get a 12 way rotary, a rake of caps and go nuts!

Dave.

Modulus_Amps

I like them, I like them switched or adjustable and with high gain they can be a gain changer to how harmonics easily develop.

The truth is some people like there amps really dull and also some people can't hear above 10k Hz

Jonathangus

Stratavarious said:

Jonathangus said:

Stratavarious said:

Push pull knob with two values on my JMP.. let’s me dial in exactly enough bright at different practise/gig levels or if I use pedals through it. 

2204?  Do you find that the effect of the bright cap is changed at different master levels, or just pre-amp gain?  I usually run the pre-amp fairly high (7-8) so it should have less of an effect.

Yep. 50w master lead II from 1979. 

Snap!

I'm lucky if I can get it much above 1 on the master!  Still sounds incredible, though.  I tend to keep the presence and treble pretty low.

ICBM

CKsam said:

Is there a difference between bright and thin, though?

Very different - to me, bright is having more treble and thin is lacking bass, which is not the same thing. A bright cap increases treble, but doesn’t reduce bass.

The problem is when the bright cap is too large, like on Marshall 1987/1959s - it lets a lot of the mid through as well as the treble, so it does sound more like ‘less bass’.

CKsam said:

Does rolling off treble on the guitar compensate exactly for the treble-bleed of a bright cap? Maybe it does, but my ears would need some convincing!

Not exactly - the tone control on the guitar is the treble bleed, not the one in the amp which is a treble pass - but it will have a generally similar result. I prefer having both options.

ecc83 said:

Switched values? Good thinking Batman! Get a 12 way rotary, a rake of caps and go nuts!

Orange did use that idea, using a 6-way switch, but with a coupling cap value so it acts as a bass attenuator - the FAC knob on 70s ones. These amps are hugely bassy with it set to ‘off’, most guitarists wouldn’t normally want that much.

Stratavarious

I have also modded the resonance NFB on my JMP.. just adds that bit of depth and body that it can lack at low to mid volume.  Addresses the bright cap issue from the other end of the studio spectrum.  

I put a variable NFB in a champ build along with some cathode bypass gain boosts on switches.. sounds epic through a celestion cream Alnico.