Mylar Caps

[Jake Kershaw]

Hey all,

Longtime lurker/first time poster! I've been really getting into messing around with dumble designs lately, especially the Ultraphonix models. I've dissected a 1973 Bassman 100 and completely rebuilt the amp using the original iron and pots. Through lots of tweaking, and great information from great people like Jelle and Hale through some lengthy phone conversations, I've gotten closer to the sound I hear in my head. But I'd like to hear some opinions on "molded" mylar/polyester caps.

I've become fond of the 6PS type in the preamp/tonestack, so I'll mainly focus on the PI of the UltraPhonix & Gain modification. For reference, I've used KOA CF for the signal path, all the PI except the plates, and KOA MF for plates and cathodes throughout. I also used teflon 20 gauge solid silver coated wire, F&T Electrolytics, as well as Sprague TE series cathode bypass caps (I found the generic black-green caps to be too low-mid heavy for my ears).

So far, I've tried:

6ps: very round and chewy sound, but can lose some clarity in the grid couplers while getting a bit bright

715p: too grainy and "brash" for me, almost harsh to listen to, no matter where in the PI or Pre-Amp I've put them.

Xicon MPP: strident and punchy. Rolls off the highs a bit and tightens the bass, but can become a bit "clangy" sounding when turned up. Might need a break-in period to smooth out?

CDE-DME Mylar: very strong low-mids bass response, but the highs can get a bit sharp

Nichicon Mylar: "softer" with a more creamy breakup. Doesn't necessarily have a ton of articulation, but a usable cap for another place in the amp (maybe the tonestack?).

NTE Mylar: my favorite so far in this spot. Very articulate and cuts back on some of the highs without sounding muffled. Bass was also tighter, BUT NTE is out of business, and it's impossible to find these caps anymore

I'd love to find a substitute for the NTE mylar caps that have similar characteristics!

Thank you all in advance for your replies! This forum has helped me more than I probably know.

Jake Kershaw

[Colossal]

Welcome, Jake,

It sounds like you are in the thick of it! Glad to have you around. There are some very talented people around here and there is always something new and exciting to learn.


Now, I need to don a hat for a moment...

[MODERATOR]

To those who will argue that parts do not have a sound, that is fine, but DO NOT post in this man's thread with negative or contrarian comments. You are entitled to your beliefs and we know where you stand. Other forum members may be interested in this topic and wish to discuss it without being the target of off-topic debate and naysaying.

This forum is about the free and civil exchange of ideas and experiences in ampbuilding. Yes, I understand that archaeology is about the pursuit of fact and truth can be found in Dr. Tyree's philosophy class down the hall.

Thank you for your consideration

[/MODERATOR]

Carry on...

[dorrisant]

Welcome Jake!

Your assessment of these different types of caps is all wrong. They all sound the same and we all know it... Just kidding (had to do it!)

Seriously, thank you for your breakdown of those differences. You're adding a couple in there that I have not sampled yet and it is good to know their relative place among the choices. Glad you dig the forum here and hope to see you build many more!

Now I have to go search for NTE Mylars before they are all gone.

[Jake Kershaw]

Glad I could help! Also to keep in mind are the tubes I used for this build: JJ803s in the Preamp and JJ 6L6GC's in the power amp. I wanted new glass to mod around for the sake of easy replacement. (I've been down the rabbit hole of NOS tubes before!)

I have some Panasonic ECQs on order from Mouser to try, and I've also just come across some Cornell Dublier DMT mylar caps I'll probably end up trying too.

ALSO, I've ordered NTE Mylar/Polyester caps from a few electronic stores, and while the 0.022uf and 0.047uf caps look to be correct, the NTE 0.1uf caps I've gotten from multiple stores are a completely different red color and say MPP (Metalized Polypropylene). I'm not sure if NTE sent out the wrong caps, but these do not look or sound like an NTE mylar cap! See attached pic for a comparison.

[didit]

Now I have to go search for NTE Mylars before they are all gone.

Uncertain whether this applies across the full NTE line, but all of the resistors and semiconductors I've bought over the years were just repackaged components from other manufacturers. They primarily served the service technician market. Similar to Radio Shack in regularly doing private-label or just bubble-pack of clearly OEM marked parts for small volume consumption.

All to say, good luck with that.

Best ..

[Abe5150]

I like the Panasonic ECQ's. Have you tried those?

[WhopperPlate]

NTE is a third party distributor; with some sleuthing you might be able to figure out an alternative source

I like those type caps for certain positions , like the presence pot, I notice they respond as you describe. Look forward to hearing any further notes from your hunt.

Fwiw all of your descriptions track with my experience. Try 716p instead of 715, not as grainy , but still very articulate

On a different note, I always recommend swapping out F&T caps , especially on the main reservoir and screens; Exaggerate grainy high end and deficient in singing midrange . Obviously the whole recipe might temper their flavor , but it’s something I find to globally color the whole amp obviously

I like ARS, but they are hard to recommend unless you test them thoroughly and form them up; I have found more than a few duds, as have bigger amp builders .

I have been enjoying BC Vishay , same with Jupiter, but they don’t have the bigger 220uf . So far consistently reliable.

[WhopperPlate]

I like the Panasonic ECQ's. Have you tried those?

Curious what do you like about em?

[Jake Kershaw]

Thanks guys! Whopper, I will have to give the 716p a try! I know for a fact dumble used them in the Tweedle Dee modifications, so I'm sure it'll add a different flavor. I'll also take a lot and see if I can find some better electrolytics. There's barely any brands than make 220uf with high enough voltage ratings, so I'll have to do some sleuthing.

I definitely agree electrolytics make a big difference in the overall sound! Just a change between the black and green Sprague bypass caps to the Sprague TE series let the amp breathe and got rid of a nasty low mid hump!

The amp is the sum of it's parts, 100%! EVERYTHING makes a difference from what I've found. I'm by NO means an expert, but you can learn so much from just swapping in and out parts for hours!

Also, from some further testing I did today, the NTE 0.1uf cap sounds very close to two of the verified NTE 0.047uf caps in parallel. It doesn't sound as brash as a real MPP, so NTE probably mislabeled the cap being it's a 3rd party distributer.

[Abe5150]

I like the Panasonic ECQ's. Have you tried those?

Curious what do you like about em?

To me they make the amp sound as if there is a light reverb on and more acoustic feel while playing clean.

[GAStan]

Just thinking out loud... a question as well as suggestion: has anyone tried putting two (or more) caps of different brands in parallel to see how they sound? I.e. a 6PS .022 and Xicon .022 to replace a .047? I realize the .047 to .044 change will change the frequency response a bit, but what would the parallel caps do to the overall sound?

I've been curious about this and thought about trying it but my untrained ear barely noticed changing ALL 715p to 6ps in my first ODS build. I have little faith that I will hear a difference but may give it a try when I get some time. Any suggestions on which would be the best cap in an ODS 124 to try?

I hope this is on topic enough to be here, if not I can start a new thread.

[Jake Kershaw]

I say go ahead and try it! As long as the voltage ratings on the caps are correct for the implementation. Don't forget about the foil ends either! I used two 0.047uf's NTE caps in parallel in my UP building for the AC shunt cap since I had no 0.1uf NTEs, and I think it works great! The small differences in the calculated high and low pass filters will be hard to hear between say a 0.044uf and 0.047uf cap.

To my ears, 6PS has a VERY different sound than the 715p, and you'll feel the difference sometimes more than hear it. I'd recommend going through the threads about the 124 build and it's specs, as I haven't personally built an ODS yet.

This is a good place to start!https://ampgarage.com/forum/viewtopic.php?f=5&t=5719

[dbharris]

Does anyone know who made the polyester caps for NTE? Perhaps the JFB series from JB caps that two rock also has used?

-Dan

[Jake Kershaw]

I'm not sure who supplied them with caps, but if you know of where to get those JB capacitors, please let me know! Especially the 0.1uf @630v caps.