Question About Capacitor Upgrade in Tube Amp

Upgrading capacitors is a no-brainer. Ditto resistors, wire, tubes, sockets, transformers, connectors, layout, etc. 

Expecting 'warmer mids' or 'silky highs' when installing Caps-4-Bux or any other component change in myriad divers applications is hubris.

The lack of rigor in accommodating environmental and CBLF changes negate generalized comments.

Capacitors of different construction types will have different sonic properties due to a number of factors (see below).

So as I understand it the properties of a silvergold in oil foil cap will be different than a copper foil in bees wax as they are impacted by voltage, current, and temperature.

As most with basic electrical circuit understanding would confirm, you can change the bass and treble response of a circuit by altering the capacitor value of coupling caps and cathode caps etc. Change from 0.1uF to 0.047uF coupling cap for example will reduce bass response.

So for just one specific example if the TC (temperature coefficient) of SGO Supreme cap of 0.22uF is different than Bees Wax cap of 0.22uF, then under operating temperatures in a hot tube amplifier their actual capacitance may be different and hence their bass and treble response will be different. How much of an impact that actually has or all the factors combined has is up to your ears to say. 

Some key properties of capacitors:

1. Nominal Capacitance (C). Capacitance refers to the amount of electrical energy a capacitor can store within its electromagnetic field. This value is represented in the unit Farad, including pico-Farads (pF), nano-Farads (nF), and micro-Farads (µF or sometimes uF for simplicity). Fixed capacitors have a specific capacitance that cannot be adjusted. Variable capacitors can be modified to achieve a desired capacitance within the available range of that capacitor.
2. Working Voltage (WV). The working voltage is the maximum amount of voltage a capacitor can receive continuously without damage or failure. Voltage can be DC (direct current) or AC (alternating current). The WV printed on the capacitor itself will typically refer to the DC rather than AC. The WV is affected by temperature, as the value listed only applies within a specific temperature range. Extreme heat or cold may affect the working voltage a capacitor can withstand.
3. Tolerance (±%). The capacitance value listed for a capacitor can sometimes vary more or less. The value can only vary by a certain range to be accepted, which is its tolerance. Tolerance can vary anywhere from real low tolerance like 1% all the way up to part with a -20% to +80% tolerance. Common tolerance values are 5%, 10% and 20%, this of course varies based on the type of capacitor it is. Capacitors are ranked in quality based on their tolerance. The lower the tolerance, the closer the actual capacitance is to the value listed by the manufacturer, thus the higher the quality of the capacitor (and oftentimes more expensive as well).
4. Leakage Current. A capacitor contains a non-conductive material known as a dielectric. The dielectric will typically allow a small amount of electricity through, referred to as leaking. Leaking happens because of the strong electromagnetic field that exists between the plates when voltage is applied. Extremely low leakage in a capacitor, such as in a film or foil type, is said to have a high “insulation resistance” (Rp). High leakage, which is more typical in electrolytic capacitors, is referred to as “leakage current.”
5. Working Temperature (T). Temperature affects a capacitor’s ability to store electrical energy. For example, extremely high temperatures can cause a liquid electrolyte in an electrolytic converter to evaporate and change the capacitance. In contrast, extremely cold temperatures could cause liquid or gel electrolyte to freeze and impact its capacitance.
6. Temperature Coefficient (TC). The temperature coefficient measures the change in capacitance that could occur within a particular temperature range. As temperatures rise, some capacitors increase their capacitance values and are considered Class 2 capacitors, such as this one GRM155R71C104KA88D, and others decrease their capacitance value. Capacitors that are able to maintain their capacitance within a temperature range are considered to be Class 1, like this one CC0402JRNPO9BN101. The importance of temperature when it comes to capacitance depends on the job at hand. If you know that temperature may be an issue, the TC is an important characteristic to be aware of.
7. Polarization. This refers to the charge of the plates within a capacitor. In most capacitors there is a positive end and a negative end, similar to a battery. When applying voltage it is necessary to match positive voltage with a positive terminal, and negative voltage with a negative terminal. Incorrect polarization can lead to severe damage within the capacitor and throughout the circuit and device.
8. Equivalent Series Resistance (ESR). This is a term for the total resistance of every part of a capacitor that resists, rather than conducts, electric current. It includes the resistance of the plates, the dielectric, the terminal leads, and the connections to the dielectric. ESR is the sum of all of these, measured within a specific frequency and temperature. This determines energy loss for a capacitor.

You ask, "Does anyone know how the power supply bypass capacitor effects high end frequency response?"

Maybe. The component may sound smoother, with a less etched treble if the power is cleaned up with such a capacitor. This etched treble is distortion which has been removed. Some who are used to digital may not like the effect.

I would also suggest that Dielectric Absorption (DA) is the most important measure for modding, because the other measures should have been considered in the design phase. The properties you list are critical when using electrolytics, which are not (should not) be under consideration here.

@terry9 

Thanks for the additional info.

I was just making the point that there are physical properties to capacitors that can alter the sonic characteristics - but the cut and paste text was more related to electrolytic yes.

Some people believe that a capacitor with a certain capacitance value must sound the same as another with the same capacitance value regardless of the type of construction. That goes against common sense for anyone with a basic understanding of science or materials.