Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on August 29, 2021, 04:38:35 pm

Title: Best Filter Capacitors on the market for long life
Post by: bnwitt on August 29, 2021, 04:38:35 pm: Hello Hoffmanites! Long time no chat. I finally have some spare time and I'm going to get back on troubleshooting my two Hoffman BFDR builds which had some tremolo issues that had me scratching my head last year when my day job ran me over. Also once that is done, I need to finish troubleshooting my Sluckey AC15 build and complete a Hoffman BFPR which I half done. I'm sure I'll need some extra eyes once I'm dug in.

Here's a question for everyone. Lately I've been seeing some people finding leaking IC filter caps in Fender reissue amps. I've used those caps on occasion though I normally use F&T or Sprague. What are the opinions of the best Filter caps for amps with the longest working life? Are Sprague Atom caps still a good value given their huge prices now? I see there are two F&T lines out there now that seem to have the same ratings. An average priced line and a really cheap line. Does anyone know anything about that?

I hope you guys are all doing well and feeling great.

Barry
Title: Re: Best Filter Capacitors on the market for long life
Post by: mresistor on August 29, 2021, 05:09:26 pm: Barry for me it's F&T filter caps. I think there is another German company that makes a similar product, but I can't remember who that was. I think I found it looking into the filter caps that George Allasandro is using with his name on them, but again it's been a while. I am not averse to using Illinois lytics, but if it's for something to sell I don't use them, I have seen quite a few leaky ones in Fender reissues..
Title: Re: Best Filter Capacitors on the market for long life
Post by: sluckey on August 29, 2021, 05:18:40 pm: Quote from: bnwitt on August 29, 2021, 04:38:35 pm
What are the opinions of the best Filter caps for amps with the longest working life?
Some folks over at TAG have begun using film caps rather than electrolytics. Last forever! Mouser has plenty to choose from. Something like this...

https://www.mouser.com/ProductDetail/KEMET/C4AULBW5350M3JK?qs=TuK3vfAjtkXliPo7aEdv9A%3D%3D
Title: Re: Best Filter Capacitors on the market for long life
Post by: Willabe on August 29, 2021, 05:35:06 pm: I read recently, don't remember where, that F&T sold to another company. I love their caps!

Sprague caps, while very good, have gone through the roof in price and their larger in size the F&T caps. I stopped using Sprague's because of this and have had no problems with F&T caps. I cut a 'newer' Sprague open some years ago and the cap inside was/is much smaller than the shell. Story goes that the reason we still have these Sprague caps is because the US military placed orders for these caps because of the size to replace aged lytic caps in tube gear they still have. The size made it easy to just pop them in with out messing around. So it was for the size of the can, with a modern construction lytic cap inside.

Film caps do last forever, but they say, over at KOC's web site, guys who have used them in builds, that they will change the sound and feel of the amp some. They respond faster than lytics and they don't distort on the hi/low ends of the frequency spectrum like lytics do. The larger the value cap the more it distorts. KOC said he uses 5 @ 20uf to replace a 100uF in his builds to lessen this distortion some. And goes as far as taking the B+ out for the chain from the last of the 5 || caps, claiming it's cleaner their than at the input/1st cap. :dontknow:

What they say you'll hear is 'there's something missing.' This would line up with a link that Silvergun posted on an experiment someone did with a regulated PSU in a tweed Bassman.

They also said, if you go with film caps, you can often use a smaller value than the lytic for the same spot in the PSU filter chain. Which would be good, cause their very big compared to lytic caps. :w2:

Carr amps has a model or 2 that uses them, guys seem to love them, so...... :dontknow: Carr said in an interview in Tone Quest Repot mag, something about how fast they respond, and that's why he used in in certain builds/models. I'd have to sort through a huge stack to find the issue. Maybe look up his web site and look at the different models to find what he has to say about it?
Title: Re: Best Filter Capacitors on the market for long life
Post by: echuta13 on August 30, 2021, 12:11:55 am: R.G. Wrote a series of articles for PremiereGuitar on "The Immortal Amp". Part of it was on filter caps: https://www.premierguitar.com/the-immortal-amp-mods-pt-4
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on August 30, 2021, 03:31:20 am: I always use F&T caps .
Title: Re: Best Filter Capacitors on the market for long life
Post by: mresistor on August 30, 2021, 03:11:52 pm: Quote from: echuta13 on August 30, 2021, 12:11:55 am
R.G. Wrote a series of articles for PremiereGuitar on "The Immortal Amp". Part of it was on filter caps: https://www.premierguitar.com/the-immortal-amp-mods-pt-4 (https://www.premierguitar.com/the-immortal-amp-mods-pt-4)

Great article thanks for posting.. :icon_biggrin:
Title: Re: Best Filter Capacitors on the market for long life
Post by: AmberB on August 31, 2021, 12:24:51 am: I wonder, do the film caps make the power supply any "stiffer" than the lytics that we normally use?
Title: Re: Best Filter Capacitors on the market for long life
Post by: Willabe on August 31, 2021, 09:34:06 am: They say it's faster in picking response. So maybe yes, because less delay on the front end of the note.

Probably subtle though.
Title: Re: Best Filter Capacitors on the market for long life
Post by: mresistor on August 31, 2021, 11:25:35 am: F&T Cap is now Mersen https://www.ftcap.de/en/ (https://www.ftcap.de/en/)

https://ep-us.mersen.com/products/engineering/ftcap-capacitors?level1
Title: Re: Best Filter Capacitors on the market for long life
Post by: pdf64 on August 31, 2021, 11:54:05 am: Mouser etc list the cap range’s operational life, it’s a searchable / filterable parameter.
Allows you to focus on stuff will a 10k or 20k hour life, eliminate the 1000 hour ‘consumer grade’ product lines.
Title: Re: Best Filter Capacitors on the market for long life
Post by: Willabe on August 31, 2021, 12:00:55 pm: From Aiken amps web site;

"I also tend to put the preamp filter caps in the circuit where they are used ("local" bypassing). For example, the first preamp tube's filter cap will be physically placed in the area of the first preamp tube, with the ground and B+ connections made right to the bottom of the cathode resistor/cap and to the top of the preamp tube resistor. If I decide to instead group all the filter caps together, I'll be sure to also locally decouple each filter cap node with a smaller capacitor, typically a 0.1uF/400V) directly from the top B+ node of that stage to the ground node at the bottom of the cathode resistor. You'd be surprised how many brand new filter caps have very high reactances at frequencies within the range of a distorted guitar. Sometimes you can take a "bad" filter cap and bypass it with a 0.1uF cap and it will sound fine. It never hurts to have good high-frequency decoupling at all nodes."
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on August 31, 2021, 12:05:36 pm: Quote from: mresistor on August 31, 2021, 11:25:35 am
F&T Cap is now Mersen https://www.ftcap.de/en/ (https://www.ftcap.de/en/)

https://ep-us.mersen.com/products/engineering/ftcap-capacitors?level1

I hope is not like when Fender became CBS
Title: Re: Best Filter Capacitors on the market for long life
Post by: acheld on September 01, 2021, 10:24:05 am: I had not noticed any change in the quality of F&T caps over the past 3 years -- though in fairness I've only been building amps for 6 years now, and I don't build enough to have a good sampling.

I recently built a Bassman with film caps in the filter section. The amp sounds great when allowed to breathe (but it is really, really loud, more than I bargained for). Don't have a lot of experience with Bassmans, so I can't say if it gains or loses from the film caps. But it is certainly glorious when turned up!

My experience with this particular build is that I am going to aim smaller and more compact in the future. Not micro, but not physically big and heavy.

Film caps are undeniably larger than the electrolytics they replace. I do like their rectangular shape -- efficient use of space. In addition, there are very high voltage specs available on many. For example, the 44uF initial filter cap I used in the Bassman is rated to 1.1 kV (certainly unnecessary, but not much larger in volume than the 700V rated part).

So, for me, I'll be weighing the need for space against the (not needed but nice to have) voltage specs in the future.

My ears will not be able to tell the difference in the response times, and the effect on tone, that is for sure.
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 01, 2021, 12:48:35 pm: Quote from: acheld on September 01, 2021, 10:24:05 am
ilm caps are undeniably larger than the electrolytics they replace. I do like their rectangular shape -- efficient use of space. In addition, there are very high voltage specs available on many. For example, the 44uF initial filter cap I used in the Bassman is rated to 1.1 kV (certainly unnecessary, but not much larger in volume than the 700V rated part).

What brand did you use, any link ?
Title: Re: Best Filter Capacitors on the market for long life
Post by: acheld on September 01, 2021, 02:35:25 pm: Latole, Mouser is my "go to" for this stuff, though no doubt Digi-Key is just as good. I don't know the distributors where you are located . . .

https://www.mouser.com/ProductDetail/80-C4AQQEW5450M3AJ
https://www.mouser.com/ProductDetail/581-FE37L6A0226KA

I just searched for "film capacitors" and used their filtering function to narrow down the choices before going over the data sheets.

The idea came from a TAG member posting on this forum. Got my curiosity . . .
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 01, 2021, 03:23:12 pm: Thanks for the link.
Yes, Mouser is a well known site for me even if I do more business with Digitech.

I didn't know at all this type of capacitor to use as filter caps.
I must be old style because their square shape puts me off. I much prefer the tubular shape.

As for whether the performance (musicality) gains in an amplifier using them, I don't know.
Title: Re: Best Filter Capacitors on the market for long life
Post by: sluckey on September 01, 2021, 03:35:17 pm: You can see some film filter caps in this recent thread...

https://el34world.com/Forum/index.php?topic=26681.msg298621#msg298621
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 01, 2021, 03:46:29 pm: Quote from: sluckey on September 01, 2021, 03:35:17 pm
You can see some film filter caps in this recent thread...

https://el34world.com/Forum/index.php?topic=26681.msg298621#msg298621

Great ! I always learn something here.

reply # 4
What is the advantage of those metal film filter caps over our traditional electrolytics? They are so big! Especially when compared to radial electrolytic caps.

Reply 5
They last forever.

Reply 6
up exactly. Unlike electrolytics that can dry out and fail over time, these don't have a 'wet' electrolyte, and therefore last forever (unless they fail, which ANY component can do) therefore in theory the amp should never need any touches inside once done. There were 0 electrolytic capacitors used here
Title: Re: Best Filter Capacitors on the market for long life
Post by: shooter on September 01, 2021, 05:37:21 pm: Quote
I must be old style because their square shape puts me off.
:laugh:
the 1st caps i played with around '69 were rectangles, "chicklets", looked kinda like a domino with the little dots colored in for cap value
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 02, 2021, 03:21:58 am: Quote from: shooter on September 01, 2021, 05:37:21 pm
Quote
I must be old style because their square shape puts me off.
:laugh:
the 1st caps i played with around '69 were rectangles, "chicklets", looked kinda like a domino with the little dots colored in for cap value

They where not filter caps. I have some of these "signal" caps in stock, and the are square with round edges, not sharp edge.
They have a "vintage" look.
Title: Re: Best Filter Capacitors on the market for long life
Post by: sluckey on September 02, 2021, 08:22:40 am: This is what shooter was talking about...

(http://www.tpub.com/neets/book2/32VS0004.GIF)

And you can see one in use between the volume and tone pots on my 1957 Harvard amp...

(http://sluckeyamps.com/harvard/h03.jpg)
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 02, 2021, 08:32:47 am: Quote from: sluckey on September 02, 2021, 08:22:40 am
This is what shooter was talking about...

(http://www.tpub.com/neets/book2/32VS0004.GIF)

And you can see one in use between the volume and tone pots on my 1957 Harvard amp...

I have some of them too. European ( UK ? ) capacitor.
They are not filter caps.
Title: Re: Best Filter Capacitors on the market for long life
Post by: sluckey on September 02, 2021, 08:49:30 am: Shooter was just joking with you about your square shape comment. We knows they are not filter caps. Those domino caps were only available in picofarad values. Very common in the '50s.
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 02, 2021, 08:52:15 am: Quote from: sluckey on September 02, 2021, 08:49:30 am
Shooter was just joking with you about your square shape comment. We knows they are not filter caps. Those domino caps were only available in picofarad values. Very common in the '50s.

Thank you Sluckey, it is not easy to "see" or understand a joke on a forum.
Title: Re: Best Filter Capacitors on the market for long life
Post by: sluckey on September 02, 2021, 09:05:21 am: The laughing "smiley" should have been a clue. :laugh:
Title: Re: Best Filter Capacitors on the market for long life
Post by: shooter on September 02, 2021, 01:17:38 pm: more non-circled E-caps similar to what we used in the radar system
you needed 2 men and a small boy to move 'em :laugh:
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 02, 2021, 01:30:48 pm: Quote from: sluckey on September 02, 2021, 09:05:21 am
The laughing "smiley" should have been a clue. :laugh:

You're right but I have a hard time "reading" Smileys.
Title: Re: Best Filter Capacitors on the market for long life
Post by: PRR on September 02, 2021, 02:56:36 pm: The earliest electrolytic filter caps (as big as 4uFd!!) were packaged in square waxed cardboard boxes. I don't know what shape was inside the box.
Title: Re: Best Filter Capacitors on the market for long life
Post by: bnwitt on September 03, 2021, 09:49:39 am: Wow! Thank you everyone for the responses. Steve, nice looking Harvard. Hasn't that yellow Aston coupler started leaking yet?
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 03, 2021, 10:02:43 am: Quote from: PRR on September 02, 2021, 02:56:36 pm
The earliest electrolytic filter caps (as big as 4uFd!!) were packaged in square waxed cardboard boxes. I don't know what shape was inside the box.

In my taste for vintage, this box capacitor has much more of a "warm" look than modern film capacitors.
I don't deny that square film capacitors can be superior.
Title: Re: Best Filter Capacitors on the market for long life
Post by: acheld on September 03, 2021, 10:06:00 am: Wha?? Leaking Astrons? Who woulda thought . . . :laugh:
Title: Re: Best Filter Capacitors on the market for long life
Post by: sluckey on September 03, 2021, 10:07:48 am: Quote from: bnwitt on September 03, 2021, 09:49:39 am
Wow! Thank you everyone for the responses. Steve, nice looking Harvard. Hasn't that yellow Aston coupler started leaking yet?
No way. It's sitting in a box in the bottom of the amp along with the PT and other caps. :icon_biggrin:

Before...
(http://sluckeyamps.com/harvard/harvard_01.jpg)

After...
(http://sluckeyamps.com/harvard/harvard_02.jpg)
Title: Re: Best Filter Capacitors on the market for long life
Post by: dude on September 04, 2021, 12:39:31 pm: I noticed in a few pic's posted from Mouser film caps, the radial film caps had four leads, why? Forgive my ignorance, if I should have known the answer.
Title: Re: Best Filter Capacitors on the market for long life
Post by: sluckey on September 04, 2021, 12:50:57 pm: The caps are big and the leads are tiny and they are designed for pcb mounting. Four leads give a much more stable mount.
Title: Re: Best Filter Capacitors on the market for long life
Post by: Willabe on September 04, 2021, 01:04:14 pm: I think if I were to try those big film caps in a PSU, I'd also strap'em down with zip tie cable through the eyelet/turret board. 1 cable tie would go a long ways in securing them from shock.
Title: Re: Best Filter Capacitors on the market for long life
Post by: dude on September 04, 2021, 02:17:45 pm: Thanks, I guess two eyelets or turrets could be used, wired together as each side has two pos. and neg. legs. I never knew film caps could replace E-caps, but they seem to cost three times as much. Of course anything for tone... :dontknow:
Title: Re: Best Filter Capacitors on the market for long life
Post by: acheld on September 04, 2021, 09:51:22 pm: Quote
Of course anything for tone...

:worthy1: Amen to that sentiment!

However, only a twenty year old who has been brought up in a monastery of the non-verbal would be able to hear a difference in tone if there is one . . certainly not me! There are some theoretical advantages at the margins in transient response, but I personally feel these are irrelevant in guitar amps.

I have used these in one build, and used some Permatex Blue to secure them very nicely. (Permatex works well because of its heat resistance and strength, yet you can remove the part if needed).
Title: Re: Best Filter Capacitors on the market for long life
Post by: pdf64 on September 06, 2021, 10:54:54 am: As I see it, for valve guitar amps, the main benefit of film caps in the HT are that they shouldn’t age and need replacement, and they eliminate the possibility of them liberally splurging conductive gubbins and goop around the amp chassis.
Title: Re: Best Filter Capacitors on the market for long life
Post by: mresistor on September 06, 2021, 02:55:15 pm: Quote from: pdf64 on September 06, 2021, 10:54:54 am
As I see it, for valve guitar amps, the main benefit of film caps in the HT are that they shouldn’t age and need replacement, and they eliminate the possibility of them liberally splurging conductive gubbins and goop around the amp chassis.

But is that really necessary? I've gotten in 45 year old amps that are still working on the old dried up lytics. If people would just be more conscientious about their equipment everything will be fine.
Do we really want the manufacturers to stop making axial lytic filter caps because many move to film filters?

Think about it.
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 06, 2021, 03:27:04 pm: Yes many of these old amplifiers work with these old electrolytics as they will also work with used lamps.

Having replaced many of these old parts, I have 9 amps from the 60's (not counting my many customers) I can tell you that in most cases the performance has been audible.

Like old guitar strings that you replace with new ones, you can hear it.

Don't forget that a certain type of filter cap breakage can damage the amp and may require expensive repairs.
Title: Re: Best Filter Capacitors on the market for long life
Post by: mresistor on September 06, 2021, 05:52:56 pm: Quote from: Latole on September 06, 2021, 03:27:04 pm
Yes many of these old amplifiers work with these old electrolytics as they will also work with used lamps.

Having replaced many of these old parts, I have 9 amps from the 60's (not counting my many customers) I can tell you that in most cases the performance has been audible.

Like old guitar strings that you replace with new ones, you can hear it.

Don't forget that a certain type of filter cap breakage can damage the amp and may require expensive repairs.

was talking film caps in comparison to tried and true lytics (https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%3Fid%3DOIP.gXkOp7j1-0KUr234hSb8LwHaEK%26pid%3DApi&f=1)
Title: Re: Best Filter Capacitors on the market for long life
Post by: Latole on September 06, 2021, 06:32:41 pm: Quote from: mresistor on September 06, 2021, 05:52:56 pm

was talking film caps in comparison to tried and true lytics (https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%3Fid%3DOIP.gXkOp7j1-0KUr234hSb8LwHaEK%26pid%3DApi&f=1)

" I've gotten in 45 year old amps that are still working on the old dried up lytics."

-mresitor
Title: Re: Best Filter Capacitors on the market for long life
Post by: mresistor on September 06, 2021, 09:19:31 pm: Yes Latole still context electrolytic caps last a long time is there really a need for film caps as filters..
Title: Re: Best Filter Capacitors on the market for long life
Post by: drew on September 10, 2021, 12:40:21 am: Quote from: Latole on September 01, 2021, 03:23:12 pm
Thanks for the link.
Yes, Mouser is a well known site for me even if I do more business with Digitech.

I didn't know at all this type of capacitor to use as filter caps.
I must be old style because their square shape puts me off. I much prefer the tubular shape.

Just got some junk mail from Mouser about these:
https://www.mouser.com/Search/Refine?Ntk=P_MarCom&Ntt=121082196 (https://www.mouser.com/Search/Refine?Ntk=P_MarCom&Ntt=121082196)
Some of the values seem like they’d be usable in guitar amps.
Title: Re: Best Filter Capacitors on the market for long life
Post by: acheld on September 10, 2021, 10:04:12 am: Quote
Just got some junk mail from Mouser about these:
https://www.mouser.com/Search/Refine?Ntk=P_MarCom&Ntt=121082196
Some of the values seem like they’d be usable in guitar amps.

I saw these caps while browsing Mouser last week, intrigued by their cylindrical shape. Don't be fooled by the multiple pins on the top, though. The four outer pins are all connected in parallel, with the center pin as the "ground."

Wow, these caps are built for physically tough environments. The smaller outer pins are rated @ 20 Newtons in tension, the inner "ground" @ 40N. Looking at their manufacturing soldering specs, they should withstand any hamfisted amp builder's soldering iron.

These look like great caps, but are probably not for me given their size, shape and lead configuration.

Since I have had two electrolytic caps fail in my heat pumps this summer, I wish the HVAC manufacturers would spec large film caps for their fan and compressor motors . . .