Sozo vs PVC Caps in Express - Clips Attached

[NickC]

EVH just signed a deal with Bugera to clone the Fender version of his Peavey hotrodded Marshall that Soldano sued Line6 over. The new Hiwatt amp will be called the 5150. Wth, it's like George Foreman Sr. names all Ed's amps or something.

This is the internet, and rumors have to be born somewhere. Please tell everyone you see.

[RJ Guitars]

I like sound clips that tell a story... it's cool that the difference is audible. You could make the argument that it's a good sounding amp either way, but it does give you an idea of what the characteristic sound each type of coupling cap will add to the complete package... now if we could just get someone to play that amp for 100 hours and record again, then change caps and do it again... it would be interesting but not an idea that I will press anyone to do. Thanks Rick for some great data!

[eazilyled]

now if we could just get someone to play that amp for 100 hours and record again, then change caps and do it again... it would be interesting but not an idea that I will press anyone to do. Thanks Rick for some great data!

I now declare this amp... done!

Thanks RJ!

[dorrisant]

Yes, I totally agree that for consistency it would have been better to have used the same reamped input signal for both clips, and to have used studio grade gear instead of a video camera.

It'd be great to have a standard guitar signal test track that we could use for demoing our builds or doing a/b tests. It would have to be a tasty player covering a range of sounds, something like a direct recording from GK's 59 Les Paul - that'd do it!

Sounds like a great idea! So Glenn... what do you say?

Tony

[renshen1957]

With that said, there is a dramatic difference in those plots that is hard to ignore. I don't buy into the boutique cap thing and TBH would be pretty pissed if I spent money on signal caps only to have to wait 100+ hours for the "magic" to happen. This to me is a part that changes specs dramatically over a short period of time and in any other engineering situation would be considered a crappy part!

Hi Cliff,

New vacuum tube amps have an infant tone stage of between 40 to 60 hours, sometimes longer. but Leo Fender never burned in a guitar amplifier any more that he matched power tubes.

I would include the infant tone period to include re-capping of the signal caps. Then, again some caps do not exhibit much change. Polypropylene sound harsh to my ears, and stays that way. Polystyrene caps do not. Both of these plastics caps are supposed to be "distortion' free. Polyester caps do add some distortion (harmonics).

One hundred hours is a typical Hi-Fi stereo burn in time for new pre-amp tubes which originally I dismissed as psycho-acoustic or power of suggestion until I re-tubed an amp, discovered the sound stage etc improve at after 100 hours, which I had to add up the time, which I hadn't paid attention to, but kept notes.

Do caps have an infant tone? How much, if any depends on the cap. I wouldn't expect any with ceramic discs, but these vary with frequency and temperature. The disc doesn't sound so hot except at a few values in the tone stack, to some. I use other types of caps in these position. I do use ceramic discs in the power supply in a few key places.

I copied this from another forum I haunt, Powerscaling.com, from a while back, which might be relevent to the Sozo polyester caps:

"Distortion tests have been made on ceramics, polys and electrolytics, but has anyone done proper tests with paper in oil? I consider that to be an obsolete type, generally replaced by polypropylene.

Polyester exhibits odd-order THD at increasing levels as signal voltage across the cap increases. THD rises faster than signal level.

Polystyrene and polypropylene are both distortion-free for pretty much any application. Their only down-side is size, cost and?or availability. I would use polypropylene coupling caps in the restoration of the amp above. (Leak Stereo)

Ceramics are good for low values of <47pF or <100pF depending on who's tests you believe."

And

"Doug Self conducted tests using basic circuits and an Audio Precision test system so the results are completely unbiased.

The results I reported were from tests Self did, confirming previous assessments by Cyril Bateman, and even further back by Marsh and Leech (or was it Marsh and Jung?). Each used the analytical tools and test equipment available in their era - not listening tests.

Years ago, Chris Russell of Bryston suggested the lower limit value for ceramics. His amps have performance THD levels that are buried within the noise of the AP-sys.2 - an output fuse or relay contact swamps the distortion of the entire amp. Note the claimed THD for his amps is at least an order of magnitude higher than exhibited THD."

"There are still polyester, ceramic and electrolytic bypass caps to impart their qualities. Note that my amps do not rely on the OT for tone (KOC uses full bandwidth toroid and ei OTs), so that veil of distortion is not present and has to be "made up" in another way."

Not to be a troll, however the Sozos or Jupiters, etc are attempting to recreate a cap from an earlier time, freckles, warts, and all. Like vacuum tubes, they represent older technology which was flawed and far from perfect. However, it is the some of the flaws that produce the tonal signatures that generations of guitarist have grown up on. Transistors and PP caps with all their improvements haven't been able to get close to the popularity of vacuum tube amps.

Best Regards,
Steve

[RevD]

To burn in an amp, could one just run a Ipod into the input and use a load on the back (or let it play if you live somewhere thats possible and it doesn't annoy the beejeebus out of you) for 100 hrs? I mean I've heard they break in speakers with small signals of electricity on the voice coils, so would that 'break in' the caps? Just curious.

Regards,

Don

[vibratoking]

I'll say it again. To make a valid comparision using FFTs requires a consistent sound file, IMO. What we have seen so far is not valid.

A proper comparision of cap burn-in is not that easy. You can't just run the amp with signal for x amount of hours and draw a conclusion about the caps. What about every other component in the amp?

Burning in caps will require them to be removed from the amp, burned-in in a separate circuit, and then reinstalled in the original amp and retested. The original amp cannot have been used, powered or changed in any way for the comparision to be valid. Any other method will not provide a clear result.

[rooster]

renshen1957 - That was a nice read. Not that I agree with all of it, but it is nice to see the opinions of others. The burn-in time for tubes is always something to think about. I still question whether some new tubes of current manufacture will have such a break-in experience - but that's just me. If it's possible, then I look forward to the day when people covet the Sovtek 12AX7 because I seem to have a few of them.

Moving back to some of the points you quoted, you forgot to mention the disclaimer that an amp used for listening to recorded music vs. one playing a musical instrument through are not the same thing and therefore have different component requirements. One man's polystyrene may be another man's oil and paper, in other words.

[eazilyled]

I'll say it again. To make a valid comparision using FFTs requires a consistent sound file, IMO. What we have seen so far is not valid.

A proper comparision of cap burn-in is not that easy. You can't just run the amp with signal for x amount of hours and draw a conclusion about the caps. What about every other component in the amp?

Burning in caps will require them to be removed from the amp, burned-in in a separate circuit, and then reinstalled in the original amp and retested. The original amp cannot have been used, powered or changed in any way for the comparision to be valid. Any other method will not provide a clear result.

That would certainly make for a fair comparison! Thanks for sharing that.

I must admit the FFTs were a bit of an afterthought. The clips were a quick and dirty way for me to evaluate the overall difference in sound between the caps. I do concede that they aren't strictly valid in a scientific sense. They are what they are I guess.

It would nice to knock up some sort of express amp test harness where pre-burned in caps could be easily substituted into the circuit using something like plug in connectors.

[ampgeek]

I use these little spring-clipy-deelybob affairs for quick substitutions. They work well in turret style fabrications.
They might find some utility in a test bed application.

Cheers,
Dave O.

[eazilyled]

I use these little spring-clipy-deelybob affairs for quick substitutions. They work well in turret style fabrications.
They might find some utility in a test bed application.

Cheers,
Dave O.

Those look ideal! Was that pic from some sort of cap experiment you did?

[ampgeek]

Yes. My brother in-law comissioned me to build him a custom practice amp. Ended up with a single input, singled end, parallel channel (triode and pentode) affair with some twists. The basic topology is much like the Weber Maggie.

I took the opportunity to try out the common cap options in a single circuit. I identified the foil/ground end of each type/size, loaded each type/size up in the clips on the board, pulled the power tube and ran an I-pod on shuffle through them for two days per type.

Then went back and played them for an hour or so with each type to see if there were any significant differences.

I am terrible at trying to describe the differences in tone/response (which there were in slightly varying degrees) but will say that I ended up with plain-Jane Mallory'ish types. The sounded just fine!

Truth be told, it is unlikely that this amp will get played much as he isn't really a guitarist and wouldn't be able to tell the difference. And...I wanted to hold on to the PIOs, Sozos, ODs for further "testing".

The clips worked great in this application. A little solder sucking on the turrets and you wouldn't have known anything had been previously installed in them.

Cheers,
Dave O.

P.S. Stay tuned for Taylor's masterful cabinet build for this project!

[eazilyled]

Thanks Dave I'll probably use those clips in the future. I don't blame you for keeping those caps in your stash

[renshen1957]

renshen1957 - That was a nice read. Not that I agree with all of it, but it is nice to see the opinions of others. The burn-in time for tubes is always something to think about. I still question whether some new tubes of current manufacture will have such a break-in experience - but that's just me. If it's possible, then I look forward to the day when people covet the Sovtek 12AX7 because I seem to have a few of them.

Moving back to some of the points you quoted, you forgot to mention the disclaimer that an amp used for listening to recorded music vs. one playing a musical instrument through are not the same thing and therefore have different component requirements. One man's polystyrene may be another man's oil and paper, in other words.

Hi,

Actually there are a few people that like the Sovtek LPS 12ax7, the ones made 1999-2001 or so. They fetch a price and have a few admirers both in the Guitar and Hi-Fi world. I possess one of those vintage LPS not by design but because I could get one cheap from a Hi Fi supply website. I purchased the tube to test new amps before using NOS tubes, figuring it anything did happen to the tube it was only a Sovtek. Turned out the tube was an exceptional tube tonally. I did the same with tsome surplus Russian equivalents to the 6L6, actually like the sound better than NOS Tung Sol 5881 in that particular amp. Your mileage may vary.

Sovtek is just a label silk-screen on a tube from what ever factory produces them. The too large for some tube shield sockets Sovtek 12ax7WA is the same tube as the Voskhod Sunrise Tube. Not every Sovtek tube is prized

As to Hi-Fi tubes, NOS and New Stock seem to go through 100 hrs bench mark. However whether TJ Full Music, Treasure series from Shuguang, Gold Lion Re-issues, EIs or NOS Telefunkin, etc people in Hi Fi spend money on new mfg tubes and then don't abuse them.

What's abuse, upside down (heat rises on the pins's seals) behind the back wave of a speaker, and then after the gig thrown around into a van without a proper cool down time.

Getting back to caps and Infant tone from amps, I don't have the resources to pay some High School student after school to play in an amp 2 hours after school for a month, but I do get about 60 hours through a variety of guitar music (from a CD) played through the amp at as close to stage volume as I can with a few mattressess to muffled the sound so as not anger the neighbors. My opinion, but having musical (and constantly varying) AC signals through the caps makes more sense than just a signal generator set to a specific frequency or very low frequency (outside the usual guitar sweet spot) used to break in speakers. Not tested in expensive physics labs, of course; I just figure that if a cap is going to form from electrical frequencies passing through it, then it should at least form with similar frequencies which the will be typical of its end use.

I've used Wax Paper and Foil, Paper in Oil, polyester, NOS Mustards (when they were cheap), etc Styrene, look forward to trying the polyester in oil, ect. where appropriate, even OD 716s for NFB loops (depending on the amp, sometimes a slower less clear cap helps with the tube amp distortion).

However, very few in general caps are made specifically for Audio now, most are for power supplies and computer monitors, but some are sold for audio as the manufacturer figures extra business and most consumer grade are from sub-standard or cheap components (including Bose).

Orange drops were originally used as caps for power supplies, not as signal caps. The changes from Polyester to Polypropylene over time were for this very reason, better high pulse current and high rms current capability, not because the cap sounded cleaner or was better for audio.

For Marshall or 1960's Fender qualities, I use polyester, but of different manufacturers. I figure the "distortion" is part of the harmonic signature, after the amp is broken in. I use Wax Paper and foil (sometimes PIO) caps for tweed amps. (Hi Fi's are a different matter).


However, every amp is different, even with the same Transformers, caps, resistors, speakers, and especially tubes. Marshall and others went from hand wired circuit boards to PCB to minimize unit to unit variance from wiring. However there is more than one individuals that claims that some model of Marshalls of any vintage from the first ones to date sound better than its brothers.


Best Regards,

Steve.

[Markusv]

Great to know about the wax paper and foil
I have a bunch of them!


Markus