Electrolytic VS Film Power Supply Filter Capacitors!!!

[finom1]

Electrolytic VS Film Power Supply Filter Capacitors!!!

Hello again. I am looking to lean from all the very creative minds here in this amazing community!!!

I have a Ceriatone Expression tube guitar amplifier, and I want to upgrade all the components in it, starting with the Power Supply Filter Capacitors!

I recently read about Film capacitors for power supply filtering instead of Electrolytic's.

I have great respect for the tube amp builders here. I have a question for you, concerning the power supply filter capacitors being Polarized, the Film filter capacitors above are not Polarized can they be used as power supply filter capacitors in a tube guitar amp?

If a Film capacitor can be used, will a Film capacitor provide higher storage capacity with better response along with better specifications than an Electrolytic in a guitar tube amplifier?

Here are the Film capacitors that Nick from https://www.hificollective.co.uk sent me:
1. 47uF/500v Obbligato Power Supply Series Capacitor - https://diyhifisupply.com/product/47uf- ... min-10pcs/
2. Mundorf TubeCap Capacitors - https://www.hificollective.co.uk/compon ... becap.html
3. ClarityCap TC, 2 Terminal PSU Capacitors - https://www.hificollective.co.uk/compon ... ap_tc.html

Nick, will be sending me information on his recommendations for high quality high storage capacity Electrolytic!!!

Here is a link to the schematic of the tube guitar amplifier that I have and want to upgrade - https://ceriatone.com/wp-content/uploads/2023/06/TW-Expression-Layout-21June2023.pdf

Big thanks to all the wonderful people here that have been so kind to me:)


Thank you for sharing any thought concerning this topic!

[TimFox]

The main advantage of a film capacitor over an aluminum electrolytic capacitor in a practical vacuum-tube amplifier is longevity, since electrolytics have a finite lifetime.
I have repaired ancient tube test equipment that used oil-filled paper, hermetically sealed in metal cases, for filter caps, and they were still good.
Unfortunately, a given capacitance/voltage rating for a PE or PP film capacitor will be in a much larger case size than for an electrolytic.

[finom1]

Thank you for this information. Room for upgrading is not an ussue for me.

My next question is, the power supply filter capacitors in the amplifier I have are polarized. Because of the circuit design of the Ceriatone Expression, do the power supply filter capacitors have to be Polarized in that particular circuit? https://ceriatone.com/wp-content/uploads/2023/06/TW-Expression-Layout-21June2023.pdf

Thank you for sharing your thoughts!!!

[Zero999]

I'm not sure what you're asking. Any circuit designed for polarised capacitors, will work with non-polarised.

[james_s]

Capacitors that are polarized are that way as a consequence of the chemistry used in their construction, to make them non-polarized would result in them being considerably larger. There is no advantage of polarization, it is simply a limitation that comes along with the high capacitance in a small package. You can always use a capacitor without that limitation in a circuit that originally had a polarized cap.

[finom1]

Thank you, that was one of my questions, and you answered it. 

The other question would be, if changing the power supply filter capacitors greatly improve performance and sound of a tube guitar amplifier?

Thank you for sharing!!!

[TimFox]

Guitar amplifiers are not designed to be linear, high-fidelity amplifiers.
From the beginning of their use, they exploit the non-linear (distorting) properties of vacuum tubes (without feedback) to generate a desired sound from the electrical pickups on the guitar body.
(The direct acoustic sound from a solid-body guitar is not very loud--the useful sound is electronically generated.)

[finom1]

Tim, thank you for bring clarity.

Leaning about the size difference and cost of an electrolytic, compared to the lager more expensive film capacitors, is there a specific type, like a Clip In and manufacture of an electrolytic can capacitor, that would noticeably improve the sound of a guitar amplifier?

Thank you for sharing!!!

[Wallace Gasiewicz]

The power supply capacitors are there just to give a good DC output with very little 60 Hz Hum.
That is all they do.
Other caps in the amp can give preference to one audio frequency than another and they are usually chosen for this.Guitar amp tecks change these audio caps to change the output tones, sometimes with particularity goofy non linear results.
If you wish the best caps, buy the brand names and I think especially the ones made in Japan are almost always good and more expensive.Nichicon is one example

[james_s]

In order to determine if something will improve the sound you first have to define what a "good" sound is. Guitar amplifiers are not hi-fi, their distortion is part of the sound of the instrument, and a lot of that is subjective.

At any rate if you're talking about power supply filtering capacitors, once they are adequate in providing filtered DC there is nothing to improve.

[finom1]

   Wallace Gasiewicz, thank you. This adds more clarity for me.

Thanks for sharing your wisdom with me. Sharing what one has learned from life is a Blessing to everyone who it is shared with.

Thanks again for sharing:)

[finom1]

 james_s, valid points. Is a scope the best way to see how well the power supply is being filtered?

This is all valuable information and is now part of the historical value of this amazing site:)

Thanks for sharing your wisdom with me, and everyone here on this amazing site!!!

[Wallace Gasiewicz]

The BIG caps that are 450 volt are meant to filter the B+  (high volts) to the final amp tubes and the B+ for the preamp tubes. These are somewhat different voltages and are controlled by the various resistors you see. The smaller 150 volt caps filter BIAS voltage to the tubes.B+ is the voltage to the PLATE of the tubes and BIAS is to the GRID. There is little power thru the BIAS. Lots of power thru the Plate B+There is a cap resistor cap arrangement for some voltages that means there is a Pi like filter for the high volts. You may wish to look up power supplies for tubesThe old power supplies would use a huge inductor choke that looks like a transformer between the two filter caps instead of a resistor. Much more expensive.There are also equations for these filters. One cap is charging thru resistor while other is discharging, makes the best use of the big expensive caps.. Keeping the cap values the same as the intended ones is highly recommended.
Yes a scope will show you the filtered voltage. But if you do not hear any HUM on the speakers,you are OK.

[TimFox]

Detail about hum, more relevant if you are designing your own amplifier:
The input stage (driven by the guitar pickup) is obviously the most sensitive to hum (120 Hz power-supply ripple and 60 Hz heater-supply AC), since the remaining tubes amplify its output.
That stage usually pulls much less plate current than the following tubes:  therefore, it is common to have a network of C-R-C-R-C feeding the plate load, where the first "C" is the main filter capacitor., and the last C is in the feed to the first tube's plate, and the last R is larger than the others.
The output stage is usually a push-pull pentode (or beam-power tube) pair:  the hum in the output of the transformer is roughly balanced out by the push-pull connection (see amplifier textbooks).
A good treatment of power-supply rejection in low-power tube amplifier stages can be found in Merlin Blencowe Designing High-Fidelity Valve Preamps (self-published 2016). 
His treatment of PSRR for different two-triode voltage amplifiers is thorough and interesting.

[finom1]

 Wallace Gasiewicz, all the details that you are sharing are very valuable to all here. Thanks for bringing clarity and definition to this topic.

Thanks again for all the sharing!!!

[finom1]

TimFox, thank you for the additional details and the clarity to this topic. Everything that are sharing with me and others on this site is very valuable and gives a better understanding on what is happening in the circuit.

Thanks again for taking the time to share your wisdom with all of us!!!

[finom1]

I will be reaching out to FTCAP Fischer & Tausche - https://www.ftcap.de/en/products/electrolytic-capacitors/. I will inquire about their, Screw Terminal, Snap In and Solder large capacity can capacitors!

I will also be asking about high Ripple Current values, low ESR, Useful Life ratings, Temperature ratings, Nominal case size.

Does anyone know of other specifications I should be asking about, please share your ideas and I will follow up on them!

Thanks everyone for share what they have learned with us!!!

[David Aurora]

Thank you, that was one of my questions, and you answered it. 

The other question would be, if changing the power supply filter capacitors greatly improve performance and sound of a tube guitar amplifier?

Thank you for sharing!!!

You're looking at this ass backwards. Which to be fair is par for the course with guitar amp internet lore.

Rearrange the problem:

Question 1- What is the actual problem with the performance/sound in the first place?

Question 2- Could it make sense for the filter caps to be causing this issue? If so, what is wrong with the capacitors you have and what is different about the replacements you're looking at?


9 times out of 10, unless a capacitor is actually faulty you're going to get absolutely fuck all improvement by changing it. In almost every guitar amp I see (and fixing them is a huge part of what puts food on my table) the things that would "greatly improve performance" are better grounding schemes, better lead dress, better tubes and correct bias*




* By better tubes I don't mean $400 NOS 12AX7s off eBay, I mean tubes that have actually been properly tested for noise, transconductance, grid leakage, etc.

[gbaddeley]

Greatly Improve?

That will be very unlikely and is very subjective. The sound character may change at high volume, but it is hard to predict and may in fact be less desirable than the original power supply caps. It’s very dependent on the design and components in the rest of the amplifier. We can’t give proper answers to your questions.

I would replace polarised with polarised, as unpolarised are going to be a lot more expensive and will be many times larger.

Try nichicon or nippon chemicon brand polarised electrolytic caps. Try bypassing them with smaller unpolarised caps, eg 1 uF - 10 uF and listen for any difference.

[finom1]

Nick Lucas, from https://www.hificollective.co.uk, got back to me about a electrolytic can capacitor with the specifications we were looking for. Here is what Nick sent me:
"Hi
See
CAP-100-R-22U-500V: 22uF 500Vdc Audio Note Kaisei POLAR Electrolytic Capacitor
and
CAP-100-R-50U-500V: 50uF 500Vdc Audio Note Kaisei POLAR Electrolytic Capacitor

Regards, Nick"

https://www.hificollective.co.uk/components/audio-note-kaisei-electrolytic-capacitors.html

https://www.hificollective.co.uk/catalog/-c-61_68_462.html

Any thoughts on the capacitors that Nick sent?

Thanks to everyone who is sharing their knowledge!!!

[finom1]

David Aurora, all great point that you brought up. Focusing on what you suggested will do more for performance and voicing then the topic I started with. It's all much more clear to me now. Thank you for turning the light on for me.

Thanks again for sharing your wisdom with us!!!

[finom1]

 gbaddeley, thank you for your thoughts. This has been an eye-opening experience for me.

Thank you for sharing your wisdom with us:)

[finom1]

What are the benefits of putting a resistor in parallel on each filter capacitor?

How do you calculate the proper resistor value to be put in parallel for each filter capacitor?

Thanks everyone!!!

[finom1]

Is there a specification for the Dissipation Factor for an electrolytic capacitor?

[Wallace Gasiewicz]

Parallel resistors on big filter caps are "Bleeder Resistors" meant to discharge the cap slowly when the unit is turned off.
They essentially discharge the cap to Ground.
Otherwise the capacitor remains charged and can shock you 
The bleeder resistors are usually very high value, megohms, and do not have to be high watt. Because they are such high value, they do not consume much power.   
The higher the ohms the slower the cap discharges.