Film Filter Caps?

[heatwalk]

Almost brand new guitar amp in for repair. Impressive 3D goo holding it all together unfortunately didn't prevent the OPT primary from opening up so no hearing this in all its glory but I've never seen film caps like this for filtering? Seems costly and heavy - any advantages? SS Rectifier

 

[soapfoot]

I've done it--not in a guitar amp, but in a tube microphone preamplifier (ten of them, in fact)

I used those same Solen metallized PP.

Works well, and should last longer than an aluminum electrolytic. Disadvantage is size and cost.

When I put them in, I swore they made the preamps "sound better" than the electrolytics I'd tried in a prototype, but in hindsight I was heavily biased toward believing that, and wouldn't dare make that sort of claim as I did no empirical testing whatsoever. I just liked the idea of it.

To be honest, I'd probably do it again, just because the elegance appeals to me--no fragile chemistry, just a roll of metallized plastic film.

 

[Ó Draighnáin]

I've done it in a guitar amp. For some reason I had this stupidly large Russian PIO film cap lying around that I must have purchased on a whim (20uF, maybe 6cm x 4cm x 4cm) and I decided to build an amp around it using that cap as a V1 cathode bypass. The amp is a 5 watt push pull amp (using tiny old 7 pin output valves) that has an AC30 type preamp with switchable coupling caps like a Matchless. I decided to also use metallized polypropylene for the power supply. Does it make it sound better? If you go looking for it on the internet you can probably find plenty of "wisdom" telling you how much better it is to use film caps in the power supply. You can also find "wisdom" to the contrary, and other "wisdom" that will tell you it doesn't matter and it is a waste of money.

I like the sound of the amp which is all that matters in the end (at least to me).

I'd do it again as well.

 

[john12ax7]

Film will last longer. And you can also get them in 630V.

 

[sahib]

..... impressive 3D goo holding it all together......

Rather ugly and somebody should have told the builder that a thing called cable tie exists.

 

[CJ]

Dang, looks like a Cinabun,

Saw those in a headphone amp, only thing I like is the no polarity thing,

 

[k brown]

I have those Solens in my Pultec MB-1 clone; sound great, but strikes me as a bit of overkill for a guitar amp.

 

[merlin]

but strikes me as a bit of overkill for a guitar amp.

Definitely. Looks like the builder has been reading too many audiophile magazines! (and then his pet African snail escaped)

So who built this amp?

 

[Rusan]

I've used the Solens as well as metallized polypropylene in oil motor run caps in tube gear. Motor run caps are designed to continuously tolerate several amps of current at high ambient temperatures, so I figured hey, they should last 10,000 years with bulletproof reliability if ya don't push 'em too close to their voltage rating. The ugly caveat is that they're huge, and must be mounted in a hole through the chassis.

 

[Newmarket]

Film caps are superior to wet electrolytics. And in some use cases you can use lower capacitance - large capacitance network is sometimes used simply to reduce the ripple current to acceptable levels for an electrolytic cap. But they do tend to be comparatively large and costly.

 

[kidb]

I've seen Carr amplifiers with Solen filter caps, I haven't tried it myself but like the longevity possibility with film caps.

 

[heatwalk]

Ding ding ding^^

I guess I question the point of bulletproof for the ages - lets not forget replacing old filter caps keeps a tech in business!!

 

[CJ]

Guitar Amps don't stay on very much, average might be an hour a day,

I got a Sony stereo that I never turn off, been running for 12 years like that,

So life span is probably not an issue.

A benefit I do see is you do not have to worry as much about the caps being idle for s long time, sometimes lytics need a little burn in time if they sit for ten years, or 50 years like the Fischer 500 on the bench.

 

[13engrsapper]

they may fail differently, see if that matters in your particular cicuit.

 

[soapfoot]

The “self-healing” nature of the metallized film might also be a benefit in a theoretical sense, but I’ve never personally tested the self-healing claims

 

[robovox]

FYI, R.G. Keen riffed on this some years back.

https://www.premierguitar.com/the-immortal-amp-mods-pt-4

 

[Newmarket]

Guitar Amps don't stay on very much, average might be an hour a day,

I got a Sony stereo that I never turn off, been running for 12 years like that,

So life span is probably not an issue.

A benefit I do see is you do not have to worry as much about the caps being idle for s long time, sometimes lytics need a little burn in time if they sit for ten years, or 50 years like the Fischer 500 on the bench.

The thing with electrolytics is that their actual capacitance reduces with usage. Lifetime is not defined by a catastrophic failure (although I have seen a handful in 30+ years). Typically failure/lifetime is defined at half of specified capacitance. It may, or may not, matter depending on the details of the design.

 

[soapfoot]

ESR can also go up with age, which means increased heat (and chance of failure)

I would expect the impact of the actual resistance (sag) to be negligible especially in a tube-rectified amp

Worth pointing out that there are half-century-old guitar amps still functioning with their original electrolytic caps, but failure rates are higher than film (if I run across power supply electrolytics older than a couple of decades, I tend to replace them preventively if the gear has to be relied-on)

 

[CJ]

Some of those old amps had dry lytics, whatever those are,

 

[Accelerator]

Com’ on guys, the Mundorf TubeCap Film Cap Series film & foil capacitors are nearly 2 decades in the business and I haven’t seen any other people at any other guitar amp. forums to weaning for their price, as you do here…

Yes, the Mundorf TubeCap Film Cap Series film & foil capacitors they are a little bit more expensive than the Mundorf MLytic HV Electrolytic capacitors, but for the other hand they have tighter tolerance than the electrolytic capacitors, they withstand in higher voltages than the electrolytic capacitors, they have much more lower ESR and lower residual inductivity than the electrolytic capacitors, they have excellent self-healing properties that the electrolytic capacitors doesn’t have and the most important for any DIY-er guitar amp. builder out there is that the Mundorf TubeCap Film Cap Series film & foil capacitors have extra loooooonger service life as they are not drying out…

After all, as I have seen all of these “crazy” & sky-rocking high prices of the 300+ € that all of these “Aficionados” paying for just to have a NOS Mullard UK ECC83 tube or the 151.27€ that all of these “Aficionados” paying for just to have a NOS Telefunken AG GmbH ECC83 tube as V1 tube for their 18-36 watter guitar amp. clone., or the 300+ € that all of these “Aficionados” paying for just to have a NOS GE 6072/12AY7 black plate, Triple Mica Gold pins for their C-12 / ELA-M 251E clone microphones, the only €37,13 that a Mundorf TubeCap 47uF 600V cost it is nothing but a joke…