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Hi! I need some help: do anybody knows which are the formulas I need to fix resistors values for a phase inverter/splitter made by a twin triode for a AB1 PP amp?
I'll appreciate ir a lot!
Thanks!
I'll appreciate ir a lot!
Thanks!
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I reckon if I were to do this, I'd use the plate characteristic curves for the tube in question, and a load line. -
Why not just look at a schematic of a similar amp?Yeah,I know that is the lazy way,but after doing the math you will likely want to tweak it anyway,so to me starting with values that work in another amp seems to be easier.Comment
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Crowhurst library
Instead of just copying/cloning something -yawn- you really ought to read through every one of these papers, plus buy some of Kevin O'Connors books. You'll be thusly armed with LOTS of great info and will not just be shooting in the dark, less likely to destroy parts in the process, and hopefully create something toneful & unique!
http://www.audioxpress.com/resource/...lass/index.htm
The Crowhurst papers are free, the lessons ...priceless!
HTH,
Alexander
The Anti CloneComment
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Well there's also
http://www.aikenamps.com/LongTailPair.htm and
http://www.aikenamps.com/LongTailPairDesign.htmComment
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If you do the math,you will likely wind up with something somebody came up with in the past anyway,nothing really exciting there.I am not saying you shouldnt be reading and learning the theories behind it all.Was just offering a shortcut.The chances of destroying parts copying a schem are slim.And to call it shooting in the dark,well someone has already done the math and tweaked it,so it would be a good place to start.By all means read these links,they are an invaluable source of info,but if you are just concerned with building something you can play,starting with values known to work and tweaking from there will teach you a whole lot about how a circuit reacts to different changes. Coming up with something "unique" at this stage of tube technology is gonna take more than knowing the formulas.Tubes have been around a long time,and anything that can be done with them already has.Even someone as "unique" as Randal Smith of Mesa hasnt come up with anything earth shattering,he just got to the patent office before someone else.Again,I aint saying you shouldnt read all you can,but nothing beats the hands on experience you get from cloning and actually seeing what happens when you change values of components.Alexander,I see you tagged yourself the "Anti Clone",hope you get to the patent office before Mesa sees what you are doing and beats you there.Comment
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What Stokes says... start from a known working design, then read up and try some tweaks but be critical in listening tests, be sure the tweaks are doing what you want.Comment
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Oh yeah! Thanks a lot! Thanks to everybody too for your opinion. I'll take a look at these PDF's.Originally posted by Alexander View Post
All this because I want to use an ECC189 as phase splitter...Comment
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This is what exactly I was looking for! Or, In the worst case, almost 90%!!!!Originally posted by rathmann View Post
Thanks a lot!Comment
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I've been reading a little since I posted some replies... well, I have one doubt:
why are plate resistors the same value on an AC50 or Twin Reverb type amp if they have just one channel! Marshall Plexis' are different, and what I've read on Aikenamps justfies it.Comment
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AC50 uses a paraphase type inverter, these usually have similar value PI plate resistors.
Twin reverbs (& other Fender long tail PI) only got same value plate resistors at the PI with the late 60's SF mods, BF & earlier had 82K & 100K...like a Plexi.
Is this what you meant? Are we still talking PI's?
Not sure about your reference to number of "channels". All the amps you mention are 2 channel amps.Comment
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Ooops, my bad- what the heck was I thinking!!!
Even quicker would be just building a 5E3 or 18W and be done with it. Just find an amp that others have deemed an Icon of Tone, and clone it. After all, the pages of Vintage Guitar magazine are FULL of exact, slavish clones or clones with merely upgraded parts, and the builders of these act like they invented the things...heck, in their minds they probably did.
In a 'creative' field like music I urge you to do safe, pedestrian cloning. After all, why learn how to take a paper schematic and make it a 3-D working device? That's obviously a pointless waste of brain energy. There's even a sense of honor out there of stealing some old engineer's hours of layout, trial and error and then passing it off as your own. Don't forget there's the elusive MOJO to be found in copying EXACT dimensions- and colors!- of tagboards, chassis, you name it. Even the colors of certain capacitors can change the mojo in a bad way. Be sure to get the wire types that can be most effected by heat and humidity, just like originals. And if you get custom transformers be sure to insist on materials like paper and cardboard, because a transformer heats up and cools down, so you want an internal element to break down over time. Newer materials like nylon behave differently than paper to the eyes of a magnetic field, thus ruining the hard-won mojo. Don't fall for the lure of turrets or point to point- the myth of good mechanical connection is just a trick. Use ONLY fish paper and eyelets...all the real amps did. Try to seek out the old "Wander Value" resistor types too- we know they always wander in the 'good' direction, wildly enhancing the mojo.
And for God's sake make sure to use the approved tube types; if it isn't a 12AX7, 12AT7, 6L6, 6V6, EL34/84, and GZ34, 5Y3, then you don't need it. But you will be considered a genius if you sub in NOS ones called "Telefunken" or "Mullard" or "Amperex". To support current production tube factories is plain stupid because this isn't the old days. If they made money and improved production quality it will just harm the value of the NOS tubes, which is bad.
When you finish your chassis, which better be unpainted if it's aluminum, be sure to put it in a box that is also an exact copy of a previously manufactured design, because there is probably some 'mojo' in there too. Hey, Fender's stuffing exact vintage style boxes full of PCB's & ribbon cable- and they practically invented Mojo. But don't forget to go NUTS when putting your logo on it. That is the one semi-permitted spot of semi-originality. If you had a nagging ethical streak you really ought to put a Fender or Marshall logo on it, but you won't. After all, you built it! Anything else is splitting hairs.
And definitely avoid the Crowhurst chapter on phase inverters, because there really only is the ONE...the LTP Almighty. Rumors of 5 others are just that. Were you to experiment swapping in different types you might learn a little bit too much about distortion and would wander off the Approved Path. None of those other types are tweakable at ALL. And math could become involved, and we know how pointless that is.
Everything has been done already, so why bother? Striving for ANY originality- and admitting that cloning is stealing other's work- is SO old fashioned! But you should still criticize Boogie for going TOO far trying to patent his circuit variations. The nerve! If it's an amp, it's yours to clone! Period! Heck, anybody who spent a few hundred hours in R&D might have come up with Boogie's or Soldano's lead channels- how dare they think they own it! 12 monkey's with soldering irons would have stumbled across it anyway...while cloning....of course!
Why try different circuit and tube types when your ears will LIE to you about what sounds good? We all know it can't sound good if it's not a clone of XYZ! Ears are the most deceitful part of the body- never trust them.
Once you got your feet wet with a 5E3, do an 18W and then a JTM45. Then a high power tweed twin. If none of these kits catches fire, you should open an on-line amp-building business- like the 26 others- offering more or less the same product mix. And be sure not to mention that you are putting together kits. Nobody in the market for a vintage style amp has ever heard of kits, and will assume you build everything from scratch. But with better attention to detail than the originals! No one will suspect the Chinese transformers. We all know that buying American transformers is stupid and evil, and supports awful Corporations. Sure it gets confusing when you buy excellent USA-made speakers from the same guy who's importing Chinese stuff...but you DO have a choice! Hell, your girlfriend is more pro-choice than you.
Anyway, sorry for the heresy- I know I should just roll over and build 5E3's, 5F6A's for the rest of my life since what's the point? I used to think there was some rebellious types at Ampage-and there probably are a couple left- but looking around at the Gallery I see clones, dead links, commercial ads, and a few variations on clones... Lots of talk, few original ideas, and fewer builds- though good to see Tim Gagan back! I assume the great American pioneering spirit is dead as a doornail from all the proof to the contrary I see here anymore. Good to see AX84 still around. Don't see any builds by anybody called Stokes, not to single you out. Maybe up there by a different name? Matter of fact the busiest posters seem to build the fewest amps from all evidence on the Gallery. Is there a new secret gallery I haven't found? Feel free to point out how I'm wrong here with a blizzard of new links. You have no idea how wrong I want to be!
If you ARE trying new stuff, then this doesn't apply to you so no whiny replies. If this stings at all- then it should. I know we all gotta start somewhere- I started building my own after getting disgusted with Fender black & silver face designs from repairs, and never looked back nor ever bought another commercial amp. And if you build a clone for your own use 'cause the originals are too expensive etc., I'm not talking about that.
You CAN come up with evolutionary and revolutionary circuit ideas- but it might take some effort!! PLEASE make the effort! Originality and/or the striving for it will set you free!!
Most Sincerely,
Alexander
Retrodyne Amplification
http://www.myspace.com/retrodyne_amplificationComment
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The Vox AC50/2 uses a larger tail resistor (47K), which balances the phase inverter outputs much better than the standard Marshall 10K value, so equal value plate resistors work fine. The Vox AC50/4 uses local negative feedback to balance the second input (via a voltage divider from the outputs back to the second input), so it isn't a standard "long-tail pair" inverter.Originally posted by slideman82 View Post
Randall AikenComment
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Alexander, I probably agree with a lot of what you're saying...but not the way you are saying it...I don't know what's got you so riled.
Like anything in life, if you want to build/innovate something, you start with a datum, realise its limitations, then the work really starts...but you would be wise to start with a known good design, purely to eliminate factors that might throw you off course. Slidemaster's initial post was on the vague side so no real way of knowing depth of his knowledge.
Let's not forget that some folks have trouble building the amps you talk about (do ALL 5E3 sound the same - of course not)..which incidentally are good reference points for a sound, which after all is what amplifiers are for...producing sound. If the math helps you get there, cool! If the suck it an see approach helps you...equally cool! A bit of both, cool!- Any method has to be subject to critical listening tests at the end of the day.
All the best, Mark.Comment
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Overload! Overload!Comment
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