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Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 12 Jan 2019, 23:54
by Ricotjuh
Hey,

In a Dual Rectifier, 1uF capacitors are connected to the cathode. Via an LDR or resistor to GND.
But when I look at the PCB these are not ordinary electrolyte capacitors, but yellow capacitors that look very similar to the construction of a resistor. The + side seems to be a bit tapered. See image below. Picture is not from the DR, but from another Mesa. But it only concerns the type of capacitor.
Someone any idea what type of capacitor this is, and what the advantage is, compared to an electrolyte capacitor.

Image

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 13 Jan 2019, 00:05
by temol
Looks like tantalum axial capacitor.

T.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 13 Jan 2019, 00:36
by Ricotjuh
You mean something like this?:
https://goo.gl/images/YqVVNf

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 13 Jan 2019, 09:39
by temol
Exactly. Check this - 1u tantalum axial cap.

T.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 13 Jan 2019, 09:45
by Ricotjuh
Completely clear. Thanks for the quick response

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 14 Jan 2019, 02:28
by Optical
Yeah Kemet tantalums
They last for a long time vs electrolydics, dirt cheap, fail obviously and are generally more compact - reasons why Mesa uses them.
They also fail shorted (an obvious giveaway vs a slowly wearing out electro cap) but seem to work well and last for a long time in Mesa amps regardless

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 15 Jan 2019, 15:29
by Rocket Roll
Actually, they have a higher failure rate than electrolytics, all of the data suggests.

One of the possible reasons for using them is distortion. When placed on signal path, they tend to introduce non-linearities, the sonic signature of which is very much respected in both pro-audio (Rupert Neve) and guitar-based audio (Tube Screamer, Rat).

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 07 Jun 2019, 14:00
by Ricotjuh
Now I have the following question. In the power amp section of the amplifier there is a 100nF capacitor (C51) in the feedback loop. But I think this is an MLCC capacitor. Anyone have any idea why no Orange Drop type capacitor is used here like in the rest of the amplifier? This also happens with C52. This is also a 100nF capacitor.
Image
Image
These are the two capacitors at the very top. Just below the resistor of the middle tube.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 07 Jun 2019, 21:02
by plush
Ricotjuh wrote:Now I have the following question. In the power amp section of the amplifier there is a 100nF capacitor (C51) in the feedback loop. But I think this is an MLCC capacitor.


It can also be XY cap for safety reasons.
Or because the board lacks space.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 09 Jun 2019, 07:50
by alexradium
Ricotjuh wrote:Now I have the following question. In the power amp section of the amplifier there is a 100nF capacitor (C51) in the feedback loop. But I think this is an MLCC capacitor. Anyone have any idea why no Orange Drop type capacitor is used here like in the rest of the amplifier? This also happens with C52. This is also a 100nF capacitor.
[ Image ]
[ Image ]
These are the two capacitors at the very top. Just below the resistor of the middle tube.
you don't need a HV capacitor there,there is probabli 10/15Vdc on one side.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 09 Jun 2019, 09:07
by Ricotjuh
Okay, but what type of capacitor is normally applied at this position?
I assume that Mesa deliberately chose this type ?!

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 17 Jul 2019, 04:48
by GeneralTiger1
Ricotjuh wrote:Okay, but what type of capacitor is normally applied at this position?
I assume that Mesa deliberately chose this type ?!



1. Detect small capacitors below 10pF: Because the fixed capacitor capacity below 10pF is too small, use a multimeter to measure, only qualitatively check whether it has leakage, internal short circuit or breakdown. When measuring, you can use the multimeter R × 10k block, use two meter pens to connect the two pins of the capacitor, the resistance should be infinity. If the measured resistance value (the pointer swings to the right) is zero, the capacitor leakage is damaged or internal breakdown. https://www.allicdata.com/list.html?category_id=1431
2. Detect 10PF~001μF fixed capacitor: judge whether it is good or not by judging whether there is charging phenomenon. The multimeter uses R × 1k block. The beta values ​​of the two triodes are all above 100 and the penetration current is small. A composite tube of 3DG6 and other types of silicon triodes can be selected. The red and black test leads of the multimeter are respectively connected to the emitter e and the collector c of the composite tube. Due to the amplification effect of the composite triode, the charging and discharging process of the measured capacitor is amplified, so that the multimeter pointer swing amplitude is increased, thereby facilitating observation.
It should be noted that during the test operation, especially when measuring the capacitance of a small capacity, it is necessary to repeatedly exchange the two points of the measured capacitor pins to contact A and B to clearly see the swing of the multimeter pointer. For fixed capacitors above 001μF, the multimeter's R×10k block can be used to directly test the capacitor for charging process and whether there is internal short circuit or leakage, and the capacity of the capacitor can be estimated according to the amplitude of the pointer swinging to the right.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 17 Jul 2019, 05:54
by Optical
Ricotjuh wrote:Okay, but what type of capacitor is normally applied at this position?
I assume that Mesa deliberately chose this type ?!


Any type of cap can be used here.
Some caps introduce nonlinearities as previously mentioned. Caps of this type generally introduce a gritty texture to the sound.
Mesa will have chosen those particular caps by substituting cap types until they picked their favourite.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 17 Jul 2019, 09:43
by FiveseveN
Optical wrote:Caps of this type generally introduce a gritty texture to the sound.


Image

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 17 Jul 2019, 10:13
by plush
Optical wrote:gritty texture to the sound


OH YEAH, YE OLDE GRITTY CAPACITOROO.

They really don't.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 18 Jul 2019, 05:35
by Optical
I guess you've never built a high gain tube amp then
Lower classes of ceramic caps exhibit hysteresis and will change value with frequency - especially when run close to their voltage ratings, but you can’t control what they change to. In high gain amps it is pretty common for the builder to trial a few capacitor types and select whichever is their favourite for the given circuit.
It's most common to use low class ceramic type in treble peakers, bright caps, as treble filter caps and tube power amp feedback circuits to exploit certain tones as that's where the effect is most apparent.

Dont take my word for it, go swap caps to some low class ceramics vs foil and whatever else in those places in a high gain preamp and see for yourself.
And here's some evidence for you two, since you think this is some kinda witchcraft :p http://diyaudioprojects.com/mirror/memb ... /caps.html
Notice what the ceramics are doing?

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 22 Jul 2019, 06:54
by bmxguitarsbmx
+1 Optical. Skepticism is High with the Stompbox community about component type, circuitboard layout, ground planes, etc. In an effort to not buy into "Magic" they overcompensate by being well.... let's just say,"skeptical". Just remember: You can approach things as a Skeptic, or you can approach things as a Scientist. The two are not the same. A Skeptic actually gets a dopamine boost from posting things like "got evidence?". Which is essentially how you develop a bias that would pollute your scientific experiment.

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 22 Jul 2019, 19:34
by FiveseveN
Optical wrote:but you can’t control what they change to


And yet somehow you can generalize to "caps of this type sound like this" without taking into account what their purpose in the circuit is, how much voltage is across them and for how long, and maybe most critically, how much more the signal gets mangled downstream. Are you telling me you can detect the distortion from the input cap in a high-gain amp, that 0.01% before the following 300% THD is introduced? What about the other way around? Have you actually, properly tested this (double blind A/B) or just trusting someone's account/opinion?
And WTF does "gritty texture" even mean? Oh, it's distorting?! Fuck me, I thought Rectos were supposed to sound squeaky clean!
Yes, we know dielectrics are not perfect, and some are less perfect than others. Show me how you get from that to "caps of type X sound like Z". Show me your "scientific experiment".

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 22 Jul 2019, 22:34
by Optical
Gritty sound is a crap description I agree. I'm not saying caps of X type sound like whatever.
My only point is that nonlinearlities elicited from certain capacitor types have an audible and measurable effect on the harmonics generated in a high gain preamp; and that builder/designers will trial some of those cap types before making a decision on what to go with. If you dispute this despite the above evidence and observations shared by high gain amp builders, then i dont know what to say to you...

Re: Capacitors in Mesa Boogie Dual Rectifier

PostPosted: 23 Jul 2019, 09:27
by FiveseveN
Optical wrote:Caps of this type generally introduce a gritty texture to the sound.

Optical wrote:I'm not saying caps of X type sound like whatever.

There must be something wrong with my reading comprehension then. I'm not a native speaker after all.
Nine years since The Cap Thread started, the best evidence of this "audible and measurable effect" are these two tiny bumps, which were even less significant in my measurements (same source, different FFT). If you've missed it, you'll find plenty of opinions in that thread. Some of the posters have even built high-gain amps, including me. Just please don't pretend that there's something wrong with valuing evidence over opinion.