Vox Amplifiers: China Versus England Built

admin · Post by **admin** » Sat Oct 29, 2005 6:10 am

Fingers>strings>fretboard>body>pickup>potentiometer>patchcord>amplifier circuit>tubes>speaker>ear is a complex chain. It is hard to determine which one of these factors, or combination thereof is most salient in producing the sought after sound.

triode · Post by **triode** » Sat Oct 29, 2005 10:21 am

I have been a professional musician for over 30 years. I know that a good musician can make good music with awful guitars and amps. It all matters, resistors do sound different, you just have not repaired thousands of amps like I have. I know the difference and it is quite noticeable.

I have been fixing amps since the 1960s and in general component quality has been going downhill.
Premium speakers, transformers, pickups, tubes, caps all make a difference, even the wire. For those who do not have my level of experience, you do not have the ear to hear the difference.

triode · Post by **triode** » Sat Oct 29, 2005 10:21 am

Yes

I have seen the insides of a VOX AC 30, but have not worked on one.

soundmasterg · Post by **soundmasterg** » Sat Oct 29, 2005 12:17 pm

I would agree with Charles that the components, including the small stuff like resistors and caps, do make a sound difference. In a recent Slivertone I rebuilt and modified, I used test leads and clipped in and out several different brands and values of caps and resistors to see which ones sounded better in that particular circuit. And there was a large difference between caps, especially between different composition types. There probably isn't as much of a difference between brands when using electrolytic caps in the power supply, but if you're talking coupling caps, then yes, there is a large difference that is noticeable to anyone with a decent ear.

wolfgang · Post by **wolfgang** » Sat Oct 29, 2005 1:18 pm

Greg,
by the way, I am not deaf at all.
But every modern component should have the quality
a decent guitar amp needs. This is right for resistors, capacitors and wires, too.
And, if someone changes a 10.000 µµF coupling capacitor of brand x to a 10.000 µµF capacitor of brand y, there will be very, very little change in sound.
But if you find an old Dynacord amp of the fifties or early sixties, please change all the yellowish capacitors, they all are leaking now, damaging the tubes!
And if your input tube is noisy and microphonic over the years, change it! It's just like a new amp.

soundmasterg · Post by **soundmasterg** » Sat Oct 29, 2005 9:18 pm

Wolfgang, I didn't say anywhere that you were deaf. I just said that anyone with a decent ear should be able to hear the differences if you change from one cap to another. I wasn't pointing fingers at you at all if you'll notice.

It isn't necessarily the idea of changing a .022uf Solen to a .022uf Xicon that is the deal, although there is a slight sound difference when doing so. (Both caps are metallized polypropylene)It is more about changing from one type of composition cap to another. An example would be the Mallory 150, which is metallized polyester, vs a Sprague Orange Drop 716P, which is a film/foil polypropylene. They are made differently, use different materials with different dialetric properties, and affect the sound differently partly due to the different size and consequently different time it takes the signal to go through the cap. The sound change isn't as obvious as changing tubes, or speakers and transformers for that matter, but it is there and can be heard if subbing caps in and out with test leads. I'm sure that Charlie agrees and he's had way more experience than I have with tube amps, though I'm no slouch myself there.

As far as resistors go, there is a large difference in hum/hiss level with carbon comp vs metal film, and carbon comp can sound smoother, probably due to distortions that the resistor creates itself, but only when used in certain places in the amp that have large voltage changes. It makes a sound difference too, although it isn't as obvious as cap changes in my opinion. Don't believe me on the resistor difference? Then do a search on an article by RG Keen and another by Steve Aloha with emperical testing evidence on that matter, with scope pics too. I'll see if I can find the link to those articles.

Most modern components do have good quality, but I've found that the better sounding parts in amps aren't necessarily the "best" quality ones. Polypropylene caps are generally considered to be better quality than polyester caps, but a lot of people like polyester caps in guitar amps better. If you're talking hi-fi, then most people would probably choose polypropylene. I have noticed some quality issues with Illinois brand electrolytic caps myself, and won't recommend them. I haven't tried that brand in coupling caps, but have heard they are fine. For wire...I think it all sounds the same, although working with the cotton covered stuff or soldering with teflon is easier than working with PVC wire. I don't think solder makes a difference either, although some people go on and on about silver solder and how it sounds better.

It all makes a difference in some way, despite what some people would have you believe. Its kind of like setting up a race car. They all have the same minimum weights and engine size limits, but the mechanics and engine builders who are best at their craft are able to tweak things to get the car to perform the best, and so they win races. Same with amps. Put it together right, with good parts, and it sounds good. Put it together right, and spend the time to pick and choose which parts you want where, and it sounds better.

But you'll notice more of a sound difference by changing tubes, transformers, or pseakers,or the circuit, than you will by changing caps or resistors.

soundmasterg · Post by **soundmasterg** » Sat Oct 29, 2005 9:31 pm

Here are those articles I mentioned. Hope they are interesting reading.

http://members.aol.com/sbench102/caps.html

http://www.geofex.com/Article_Folders/carbon_comp/carboncomp.htm

wolfgang · Post by **wolfgang** » Mon Oct 31, 2005 6:39 am

thank you for the links, Greg.
But I made my statements...

Wolfgang

admin · Post by **admin** » Mon Oct 31, 2005 7:38 am

Sound is a very subjective thing. I always want to hear the voice of experience but at the same time remind myself that there seems to be limited research that I have read that has conducted double-blind tests with various components. If I am in honest error here, I would welcome additional references.

On more than one occasion on this Forum, I have failed to identify the sounds of different models of Rickenbackers, in spite of owning some of those models myself. That is not to say that there isn't a difference, only that I have been unable to hear the difference between one instrument and another. I have also been fooled when trying to identify an amplifier from a sound test.

Whether my inability is based on my lack of experience or knowledge is an empirical question, however, I am also reminded that I am better able to identify some sounds on some occasions but not on others. For me, attention, fatigue, fluctuations in hearing, atmospheric pressure, heat, cold, loudness, stress and countless other factors limit and change my ability to discrinimate one sound from another.

Some days I tune my instrument flawlessly with great ease and later on that same day may dispute the information provided by my tuner. Have you ever waited to hear a favourite song, from 25 years ago, only to find out that your memory of it was much more optimist that the song deserved?

Sometime ago, I bought a guitar patchcord that I was convinced allowed for a better sound. But recently I flunked the test between it and another.

I will continue to listen to the experts, but in the end, I am left with my own limitations. If I can't hear the difference, then regardless of what the scope may say or the ear of the expert, the changes will be wasted on me.

I continue to find these discussions stimulating and when all is said and done, I learn something else about myself. That is sufficient motivation to keep me coming back for more. So thanks to everyone for their comments here, that is what Forums are all about.

soundmasterg · Post by **soundmasterg** » Mon Oct 31, 2005 12:40 pm

I'm not saying that in a double blind test that you could discern which amp is using Mallory caps and which is using Orange Drops. What I'm saying is that if you sub in various cap brands and types, or resistor types, you will hear a difference between them, and its very obvious, but not to the point to where you can tell brand A from brand B in a blind test, and also not as obvious as subbing in different tubes, transformers, or speakers. You can use this approach to tune your amps the way you want by using different caps and resistors in different spots. If they were all the same, then everyone would use the same brand and same type and be done with it...but they aren't. Lots of amp people are famous for doing this...people like Ken Fischer at Trainwreck come to mind, so its not like its voodoo and never heard of. There are also scientific reasons why a carbon comp resistor will sound different than a metal film, as one of those articles points out.

Everyone does hear differently, and thats also a scientific fact. Not knowing anyone's experience level, there is no way to know if someone else has experimented the same way I have or not. When I first got into amps, I was skeptical, but I kept an open mind until I had tried using different brands and composition types myself, and I can hear the difference, so of course I assume everyone else can too. I've found I really like the sound of NOS paper caps, but of course they will be leaky soon if they aren't already. Most modern caps are brighter and harsher sounding, but will last a loooong time, so it all depends on what you're looking for and what your experience level is.

admin · Post by **admin** » Mon Oct 31, 2005 12:51 pm

Good points Greg. Without a doubt, the differences between different tube amplifiers is apparent and thank goodness for it. It is hard to argue with the voice of experience and your comments are appreciated. The judgement calls are interesting too. Do you go for the sweet sound for a little while or the harsher sound for a long time?

soundmasterg · Post by **soundmasterg** » Mon Oct 31, 2005 4:32 pm

Peter, in the case of someone like myself, who can work on amps and replace parts, I may choose to use a NOS paper cap if it tests ok in one of my own amps, but if I was producing an amp for sale, I wouldn't because they would stand the chance of being more unreliable, since paper caps are like electrolytics and will fail eventually. Theres also lots of modern caps, like the Mallory 150 series or the Sozo caps, that emulate the older sound of paper caps pretty well, and most people wouldn't be able to tell the difference anyway, so something like those would work for them.

kevin · Post by **kevin** » Tue Nov 01, 2005 3:01 pm

Charlie,

Sorry to be sounding like I'm pinning you down, here, but I want to make sure of this. I honestly couldn't tell from your reply. So...

Have you seen, in person, the insides of a Chinese-made Vox AC30CC? Have you seen the insides of the 90's UK-made AC30-TB amps?

admin · Post by **admin** » Wed Nov 02, 2005 6:36 am

Kevin: I understood from Charlie's most recent post above that he has not worked on an AC-30.

triode · Post by **triode** » Wed Nov 02, 2005 8:28 am

I have seen the insides of 1960s VOX orignal AC-30s, but not the 1990s version. I have seen the new Chinese ones in a music shop a friend owns in Marysville, CA