Designing a new amp, Component choices.

[JamesHealey]

So I've pretty much drawn up the circuit for an amp I'm going to be making a fair few of.

Now I need to decide on the component choices.

I'm thinking the following:

Vishay BC 450v Electrolytics (Great stability and life span, sound good too)

CDE 1% Silvered Mica Caps (Great stability, great tollerance and temp co-eff)

LCR PC/HV/S/WF 1000v Film Foil Polypropylene Caps (Great stability, transparent tone and great temperature co-eff)

Welwyn PR5Y Metal Film resistors (0.1% Tolerance, 15% ppm, low noise)

Edcor Transformers


Now these are some pretty unusual choices I know a lot of guys aren't big fans of Polyprop or Metal film but i'm going for low noise and a circuit that will be voiced using these components.

Am I going to lose tone using these components am I better sticking to the time old proven Carbon film, Polyester etc??

Or do I take merit of the great stability, consistancy and noise level of modern materials and tweak the amp to suit their tone?

opinions?

[Structo]

The thing about polyester caps is that polyester or Mylar has probably the worst temperature coefficient of all the dielectrics.

Maybe that is part of the mojo about them, often you hear guys say, my amp sounds a lot better after it has been on for an hour.

Polyprop is a better capacitor, on paper anyway.

No real right or wrong in the tone department, you are the one that has to be satisfied with what you get.

If money was no object I would love to build two or three test bed amps where I could try different styles of caps and resistors to hear what the different tone shapings would sound like.

Somebody in the Dumble section used spring clips where the caps went and tried different things.

[surfsup]

I don't have an answer but would like to know more about this as well so if anyone has any opinions, thanks...

[Cliff Schecht]

You are fine in your decision to use the higher quality polyprop caps and metal film resistors. I can't say whether you will like or dislike them but in my experience they don't sound any worse than other popular technologies (I don't hear a difference at all TBH).

For the metal-film resistors, I think a lot of the negative connotation of these comes from people using the cheapo Xicon metal films and not liking them. I personally found them to be harsh sounding. But how many dozens of builders on these forums alone use RN65C Dale MF resistors and absolutely love them? I know I do (in the right situation), they're great quality, have sturdy leads, sound amazing and are dead quiet to boot!.

Go with your gut and ignore the convention that others blindly follow. The reason a lot of others use the "standard" components that are found in a guitar amp is because they don't know any better. Any reputable builder will use good quality components that they know work reliably and give them a consistently good sound. Having to deal with practices like sorting out caps and resistors for value is a waste of time, any engineer can tell you that EVERYTHING in the amp has a tolerance anyways so getting one amp to sound like another is as much of an art as it is a science.

[paulster]

James

If you want really musical sounding metal-films then take a look at the Vishay Beyschlag 1W BF0414 resistors from Conrad.

They sound fantastic, not metallic at all (they're non-inductive) and are so quiet that my uber-gain JCM800 (JCM800 plus a tube gain stage) when dimed won't get in the way of a conversation right next to it!

I really want to try these in a Wreck build sometime soon.

As you know I've loved the LCR PC/HV/S/WF 1000V caps when I've used them so I don't think you're going to be disappointed if you use these. The only thing I have against them is they are huge. Oh, and the yellow could be a little less dirty looking!

Not tempted to use F&T for the electrolytics? You don't need to order a huge amount before they'll do them to your own specs. Much like 'Ask Jan First' has done.

Paul

[billyz]

Your choices make sense if you know why you are making them.

I don't think many are aware that resistors can be magnetic as well as inductive. For the best tone choose a non magnetic type, ie Dale Rn65.
other good choices : Takman, PRP, Beyschlags, and others.
http://www.soniccraft.com/takman_resistors.htm

These caps have gotten very good reviews for the money. and they come in every value you might need.
http://www.soniccraft.com/sonicap_gen_2.htm

While your at it use some high quality wire too. Silver plated wire has a diode effect between the two dissimilar metals, I prefer to use something like Kimber copper wire. The dielectric can cause a wave propagation effect. Teflon is superior in this aspect.

I expect there to be poo poo ers, but these effects are real and can add up to make one build sound different than another identical circuit executed with careful component selection.

Some will argue a guitar amp does not merit the use of such "HiFi" grade components, different strokes for different folks, let them drink Bud.

[David Root]

I just decided to upgrade from 22 ga to 20 ga wire and ordered a total of 300 ft of 20ga stranded in 10 different colors incl. tracers. All silverplated teflon insulated.

I have just started using Kimber 19 ga for wiring from coupling caps to power tube grids. Have not heard it yet. It's not easy to tin that stuff.

Please explain the diode effect of Ag plated Cu wire?

[billyz]

The effect is dependant on the thickness of the plating, relating to the skin effect. It is also evident at all junctions ie contacts. You cannot avoid it entirely just try to reduce it as much as possible. Impurities are also present and contribute. The satellite industry is well aware of these problems. A guitar amp is not so critical. But I try to incorporate as much signal purity as I can in my builds. Others may opt for a different approach.

www.pimtesting.com/IndustryLinks_assets/seven.pdf

I find Kimber wire to be very easy to tin and solder.

I will probably get booted off for these heretical ideas.

[Reeltarded]

Yes. New crap sucks. Stop it with the ideas.

Thank you.

[Jackie Treehorn]

Billyz, I agree 100%. The hifi parts, to me, sound the opposite of sterile in a guitar amp. They intensify the great qualities of a tube amp! Of course, hifi guys wouldn't consider a sterile, harsh, or bright sounding part to be "hifi." Lots of misconceptions regurgitated on forums, so it's nice to read some open minded opinions on parts selection.

Those LCR caps look interesting. I've been looking for a film/foil (not metallized) polypropylene axial cap. Where can one get the PPT series?

One thing I'd like to add, of the "old" parts, I like carbon comp resistors a lot. Their puffy sound works really well with the tightness and extended top of polypropylene caps.

[David Root]

That has been my finding too I use PRP MFs, Takman CFs and Dale RN65 MFs, but I will also mix carbon comps in where I think the circuit calls for them.

I loved the Black Gate 500V electrolytic cans, all long gone now. The smaller coupling and bypass types are great and still available. I use F&T and computer grade HT PS caps. ARS cans are great in Marshalls, even though I believe they are Chinese and not hi-fi grade, and I have used them in a D-clone too.

OTOH, I would not hesitate to use cheapo PS caps in a tweed build, along with solid wire and the best carbon comps I could find. Not to mention undersized iron in M27 or M19.

James are those 450V VishayBC the little blue ones made in Austria? That Mouser has.

Billyz, I nosed thru that paper you posted. They are talking about RF and skin currents in, you are saying it also applies to AF? I'm willing to take a preventive view because IM distortion is such a universal evil in any audio device. Still stuck with my 300 ft of wire though!

[Zippy]

Your choices make sense if you know why you are making them.

I don't think many are aware that resistors can be magnetic as well as inductive.

I'm with you, Billy, in wanting to know "Why" - How does a magnetic effect affect tone in a resistor? Has it something to do with component layout and lead dress? Is this an effect that we can use for good (aka tweaking)?

While your at it use some high quality wire too. Silver plated wire has a diode effect between the two dissimilar metals...

If electron flow is along - rather than across - the interface, how does that make any difference? (P.S. - Yes, I read about PIM and learned that it is an issue for MHz range circuits.)

The dielectric can cause a wave propagation effect.

What wave? I believe there can be a minor capacitive effect between wire and the ground plane of a chassis but I don't understand this "wave propagation effect".

The effect is dependant on the thickness of the plating, relating to the skin effect.

"Skin effect" is usually associated with very high frequencies. Is that really an issue in the frequency range of guitar amplifiers?

Thanks for putting up with my questions.

[Colossal]

Billyz, I agree 100%. The hifi parts, to me, sound the opposite of sterile in a guitar amp. They intensify the great qualities of a tube amp! Of course, hifi guys wouldn't consider a sterile, harsh, or bright sounding part to be "hifi." Lots of misconceptions regurgitated on forums, so it's nice to read some open minded opinions on parts selection.

I couldn't agree with you guys more. The effects of using superior materials and precision crafted parts are cumulative and they add up to better sounding amps. I recently built a "hi-fi'd" Marshall 50W for a guy and next to his vintage '72 metalface plexi, he said it sounded better hands-down. He said it sounded more open, clear, and less congested while retaining the plexi characteristic. I used high quality 3W non-inductive metal films for plate loads and other places, 2W carbon films elsewhere and threw in two (measured) 82k and 100k AB carbon comps in the PI, just for the fun of it. Sozo hand wound caps throughout and a couple of Solens as well.

[billyz]

I confess to not fully understanding all these concepts. My son is the Nuclear scientist and when he explains them to me I understand , but not well enough to articulate the minutae to someone else.

The Wave propagation of the dielectric is like when a motor boat travels thru a lake and leaves a wake that follows. The wave arrives later than the boat and not all at the same time. It causes a smearing of the original signal. Air is the best dielectric , cotton is good too. probably why the Japanese prefer natural fibers for their high end audio systems. And many vintage guys like cloth covered wire in their amps. But these are not practical for other reasons as you can imagine. Teflon is probably the best dielectric with very low wave propagation , also has low capacitive properties, even though it is a bitch to strip.

Magnetics are used to alter the path of electrons in particle beam accelerators, magnetic resistors distort(bend) the flow of electrons in your audio amplifiers too. This is not the shot (johnson) noise you hear. The old CC resistors are non magnetic and probably one of the big reasons old timers prefer Allen Bradleys and can hear the difference from a cheap Metal film.
To me magnetic resistor sound a bit harsh and edgy.
Now everyone go get your magnets out and test your resistors, ha ha.

I am not saying everyone should be building their amps with these principals, but it is good to be aware of them. I was a lot happier when I thought Bud tasted like a good beer.

Thanks for not declaring me the village idiot.

[Jana]

"Thanks for not declaring me the village idiot."

I don't think they would do that--one is plenty although I do get bored with the job sometimes.