Hello Zappacat,
                     Hey alot of Q's there!
I think you need to get some ideas nailed down first and kinda stick to one thing at a time,, kool?
Re the LM 4780 chip Q.
You can simply look up the specs for that and it will be obvious if it is stereo or not.
----
Two of those proj 101 Amps will make your ears bleed my friend and you will need at least two quad boxes to make use of all that power. Anyway the cost of the PSU at 100VAC-CTap tranny will scare you!   oh and YOU have to carry it also.
I only mentioned it because even at 40/0/40 VDC it will still have ample power.
----
If you want balanced outputs to send to a desk then I don't get it.
You wish to DI a 400watt Amp to a PA desk,,, like what For
----
If you don't know *most* SState PwrAmps can handle 4 OHMS minimum load.
Less than that and you are pushing your luck.
Read project 101 more slowly and absorb it,,,the Answer for that is on that page anyway.
----
Personally I never got the stereo trip as a good guitar sound with a little time effect and good EQ will sound far more convincing than any stereo pod.
I can do more tricks with my simple gear than most of those cab sims.
Sadly these days the player is judged more by how up-to-date his pedal board is than his ability to play good music. 
just my thoughts.

If I'm getting this right you really need two things,,,
1/ a stereo preamp (with bal outs).
2/ a Stereo poweramp.

BTW there is some bal circuit ideas on ESP site
Cheers, Phil.

Hello Jack,
              Yes you will need a preamp for peizo.
Media player has line level output and you can't just join that with a PU
(of any type really).  The Ruby has a 1m5 gate R but that ain't enough for hiZ PU.
you need more like 2meg or even 10meg.   Better to make the peizo *Active*then you can plug into just about any line level which makes it versitile.

I get "Forbidden" on that link for peizo, (I have no clue with computers?) but not to worry there are quite a few and they are likely to be similar. The Fet based ones that have bootstraping will likely be the go for pz PU's as they multiply the input imp.
Anyway here is one I whipped up for a chap on the cheap.

My peizo buffer is low output but don't let that fool you as it has very high input imp and any good guitar amp will deliver the rest.
This was made to replace a painful onboard unit that suffered from way too much hi freq content which makes Acoustic guitars sound stupidly harsh and very unnatural (though some may want that)
and of course the manditory feedback issues that tend to go with acoustic Electronics.
R1 can be as low as 500k but the bootstraping of C2 will make it much larger.
Use metal film for R1 if you want to keep noise low as possible.
You need a very high imp input when using peizo's otherwise you will loose a lot of the low freq content. Again a balancing act, to much and they tend to suffer feedback.
make C1 smaller if you wish to wipe off more bass.
The optional cap across the peizo element may work on some units, depends on the peizo used.
Don't ask me to explain just try it and see what you think.
Play with C4 if you want, to cut the top higher use a smaller cap.
Try from 10nF up to 47nF and see what you prefer, If you want ALL the high freq just delete C4.
Oh yes The 9volt battery will last a long time.
A chap by the name of "Don Tillman" (I Think??) has a whole page dedicated to simple fet preamps, his ideas may give much more info.

The mixer pattonBa refers to is passive and there will be overall level loss.
If your ruby has enough grunt it may not be a problem but it will be of limited use on other equipment so may I suggest a *dual input* on the ruby Amp and be done with it.
there should be enough schematics around with 2 inputs mixed into one to give you
an idea of how to achieve that. I don't use fet circuits much but I'm sure someone here will chime in here and offer something useful in the way of mixer circuit ideas using Fets.
Have fun with it.
Cheers Phil.

Hi Jack,
          A Q before I go on.
Is the peizo PU passive? (ie, no onboard preamp)
If so then even a mix buffer won't help you much.
Cheers Phil.

Hi Zappacat,
         Try this one instead http://sound.westhost.com/project101.htm

Probably eaiser to build,, a Ton more grunt (depending on PSu Voltage used)

The hidden bonus for this one is it will run on just about any voltage all the way up to 70/0/70 VDC rails where it will output over 200watts into 8ohms.
I have not built one but it certainly looks like it would deliver the super clean flat response,, if that's what you want?

Also as you want stereo the price may climb quickly so have you considered some old HiFi poweramp sections they might be worth a look you may even be able to use some of the line inputs and save yourself a lot of work.
You can pick up old 70's hifi amps cheap where I live.
Cheers, Phil.

Quote from: Jack.Straw on April 29, 2009, 09:31:08 AM
Hello everyone.  I've just finished building my second Ruby circuit (http://runoffgroove.com/ruby.html).  On my first amp i used a little 8ohm 5" speaker out of an old stereo.  It works fine, but for my second project i need to balance function with  size.  I know almost nothing about speakers, so i was hoping someone here could make a recommendation.  When selecting a speaker what sort of things should I look out for? (other than a total impedance of 8ohms)  Is the size of the magnet something to look at?  Do certain speakers respond better to guitar frequencies?  What would you say the smallest diameter speaker i could use and still produce a strong sound & good tone?

Thanks for your time,
-Scott

Hi,
   If you are trying to get your head around speakers then I find the easiest way to explain it is thus;
There are only really two types worth understanding, those being "Low Complience" (musical instrumet/voice/guitar)
and "High Compliance", (Hifi, woofers for reproduced music).
Bass drones for cars and disco stuff.

For guitar you want LC.
What's the diff?   Easy HC wobble easy and  LC are stiff as a board.

How to tell?  HC, Woffers have a loose rolled edge (called the spider) and a rather long loose travel (easy to move with light force). These need to be in a box that is tuned to match the driver paramiters otherwise they sound crap.
This is not what you want for guitar.

LC on the other hand are very rigid with very little movement. They can be used without great need to *Comply* with box design.
In the really old days this is all that was used and I've seen early PA's with a 12" driver mounted on a 1 metre flat square board (no side or back), For voice reproduction this is all that is needed anyway.

Magnetic guitar PU's have masses of bass output and you really don't need much low freq help. Try plugin' a modern guitar and Amp through a wooffer and I doubt you will like what you hear.

The early celestion company was commissioned by the mines to make a speaker for a siren and the design called for high output at 1kHz too 3kHz.
Greenbacks as they are now called where not designed for guitar at all.

Just so happens, that these are the frequencies where the magnetic PU guitar needed a boost and so the rest is kinda obvious history and many folk probably don't realise that all the treble for Guitar is from 1kHz to 3KHz.
For hard driven OD rock anymore bandwidth just destroys the sound and it is no longer sweet.  (listern to Carlos Santana and I doubt there is much above 3kHZ)

These days speaker makers are going crazy making all sorts of claims about extended freq response but I have heard enough of these to say I have my doubts as to the benifits of such claims.
Unless you are wanting pristine clean then more bandwidth will just get in the way of good tone.

Good speaker effeciency (High SPL) is a bonus and worth some merit but as long as you realise the drawbacks that can come from that. I doubt that many Amp designs adjust their circuits to suit the drivers that are used.
Brand name Amps use high SPL (sound pressure level) Drivers simply because it makes there product Louder than the competion of the same wattage.
An old wise man once said to me that it would be better to design an amplifier from the speaker first and work your way back from there.    interesting thought?

I just recently pulled the very harsh Speaker from a Trademark 60 (Teck21 stuff)
and replaced it with a less efficient driver and the owner was amazed
at the difference. Yes slightly less percieved power but now a joy to play.

I don't think you need a degree in sound enginering to get an idea of what works as
It really just comes down to balance,, Just think of a hifi speaker where you have bass, midrange and tweeter.
If you have one super high SPL output driver and the others only average then
it will likely sound off. It is better to have all the drivers balanced even
if they are not top of the range drivers you still get a balanced good quality tone.

You mentioned magnets.
This is another of those things that tends to just end up as a dog chase tail affiar
as the bigger the magnet the more energy required to move the darn voice coil and cone.
So pick a magnet and keep in mind that some small older types sound better than those big mag one's.
Anyway You would be better to look at the Voice coil as it's more important and
can make a big difference to the tone.

Understand that regardless of magnet size any given cone diameter can only handle about 3 octaves efficiantly and smaller VC's for same dia cone will sound more peaky at some ugly freq.
Some small speakers sound quite good if they have a decent sized VC.
(sadly a lot don't)
A larger VC for given size cone will keep the cone more stable over a broarder freq range, hence a flatter better perfomance.

Some 12 guitar speakers can sound very honky because they have a VC that is to small for the cone dia. That said some may like the peaky nature of lesser drivers found in really old Amps.  Pick a flavor?

For guitar The rule of thumb seems to be 12" cone with a 1-1/2" VC.
(Celestions had 1-7/8" VC).  So anything around that is going to be good.

Even if you only want 6 inch speaker at least now you have some idea of what to look out for
Well this turned into a marathon so I hope it helps you in your pursuit of great tone.
Phil.
   

To awdman,
Your idea of Valve pre Amp SState powerAmp has been done to death
Try it the other way round and you will achieve a lot better results.
Although you get some benifits from valve preamps it's nowhere near as good as a Valve power amp stage,,,,
---------THAT is where the magic happens NOT the preamp.-------
I am speaking because I've done this stuff both ways,,,,
Just my 2 cents worth.
Phil.

Short answer,, Unlikely.
The possibility exists but there are a million and one possibilities.
You'll go crazy trying to list them all
If you have not used the Amp for a while then even the wheather can change they way your ears hear things.

Try setting up a 1000 Watt sound system in an empty venue test it,,,
then (without adjusting anything) come back when the venue is full and the whole thing will sound very different.
Phil.

Quote from: svstee on April 02, 2009, 11:28:11 PM
Well, I need an amp for my college jazz band. I always wanted a Roland JC, even before I played much jazz I thought they had the best clean tone ever. I have an idea vaguely sort of similar to the JC, two totally separate amps each running into a separate speaker, each voiced a little differently for a nice stereo effect. I came across this
http://eu.st.com/stonline/products/literature/ds/1459/tda2030a.pdf
and my tentative plan is to build two poweramp sections with these, using something like this
http://www.runoffgroove.com/tonemender.html
for each of the two preamps.

Thanks, this looks like a great forum!

Hi svstee,
              Unless I'm mistaken,,,
the Roland Jazz Chorus Amplifier circuit is ONLY stereo when the Chorus is engaged,,no chorus engaged = no stereo,, straight mono or but both poweramps delivering the same sound through two speakers.

The first true stereo chorus in an amp was the selling point of those amps.
A mate I knew had JC120 and it made his all white tripple humbucker LesPaul sound like a tin can.
IMHO the most overrated SState Amp of all time,,,but hey that's kool if you like em.

I know this is slightly of topic but
The HCR30 Laney mentioned here by Fahey is quite a good little Amp just needs a better tone control,, but as you are after a jazz tone then a different preamp/tone section is probably needed.
If you are even remotely thinking of tinkering with different circuits get yourself a breadboard and experiment until you find what you are after.
Otherwise you will waste a lot of time building stuff that ends up in the bottom draw as spare parts.. Just ask me I have lots of those,,,
"Seemed like a good idea at the time trashed boards"
Have fun with it,,it's very addictive.
Phil.

Quote from: J M Fahey on March 07, 2009, 12:18:50 PM
Dear Phatt, that´s exactly the relatively no pain but precise way to go.
To summarize it, and compare it what´s available "out there":
the signal chain should be:
1)Active mics/active electronics in guitar/inline clean preamp
Al three amount about to the same end result: powerful, clean guitar signal; sent into:
2)Some GOOD distortion/overdrive that you like; sent into:
3)Good clean preamp, Fenderish or Marshalish or Voxish (your choice) which can be Tube (the classic solution) OR SS which sounds the same *when clean*;  driving:
4) Some *Power* tube, which can be overdriven and Transformer coupled to a real-world speaker , with all its quirks, resonance, impedance and phase shifts, nonlinearity, etc.
Here's where the real Witches Brew cooks, in that complex interaction between those three actors.
I agree with you that a PP amp is best, but even a humble Champ can prove its worth there (I´ve already tested that).
That signal should be suitably padded and re-amplified by
5) A good SS amp driving guitar speakers.
5)Your inclusion of a Graphic between 4) and 5) allows for fine tweaking of the sound, but must be used subtly and carefully to avoid destroying the sound you already have.
I agree that that´s the way to get World Class sound in a very practical way.
Congratulations!!
Please post some MP3s
Bye.
J M Fahey

Fahey,
          Thanks for your words of encouragement, Sounds like your more into the teck side of this stuff than myself   I still cringe at the thought of all the maths you need to know to work it out but this is all good as the more options put forward allows people to make well informed decisions.

I look at it this way; I'm 90% there with cheap mostly secondhand or DIY equipment.
Then I look at how much $money$ I have to spend to get the last 10%  yuk
Keep in mind I do this on a strict budget so if budget is no issue then sure try all the options.

All this back EMF / RCL spk equivilants/ Damping stuff is obviously quite real. Fine, No argument from me BUT I would question how much of it you can actually hear?

If I understand you correctly I think you're coming at it from a different view, ie, your trying to capture the tone/dynamics of a said tube amp but that concept is a lot harder to impliment.
It demands the mojo tone already exists inside the tube amp whereas I'm trying to negate all of those complexities.
I'm only using the tube pwramp as a building block, a giant distorion unit if you like.

I have heard enough amps in one lifetime to know that I'm still ahead of the well trodden path where everyone keeps changing Amps/Tubes/PU's/Speakers hoping for some magical mojo to materialise.
Consider EVH, in the early days he likly used resistive loads and some kind of reamping. (probably SState)
The idea may well be flawed but still good enough to make him famous.

Also Randy Bachman used a reamp setup on the famous hit song "American Woman" again technically not ideal but Wow,, what an amazing guitar track that turned out to be. (google Hertzog and Randy B)

BTW, the Guytron GT 100 "IS" based on much the same basic idea, a pair of EL84 driving a resistor then into a big power amp.
The moment I heard that Amp,, I knew it was different and I wanted that sound.

I would simply say this; OK mine is not as refined as the Guytron but in my humble experience,
Any Loss with my setup is far outweighed by the amount of Control I get in return.
Sorry but loading MP3's is out of my ability with computers, I'm still learning how to get around this web thing. OK laugh if you want but some of us older folks struggle and are still trying to catch up.
Cheers, Phil,,, Nambour Australia.

 Damn! Could not get both pics to load , so here is the Speaker load to Lineout drawing.
Phil

Quote from: pelanj on March 07, 2009, 05:53:33 PM
Phatt, transconductance as I understand says, what plate current corresponds to grid voltage, kind of "amplification factor". That is nice setup you have, I am also very slowly heading towards something very similar. I have a 15W higain tube amp to play with, but I have to finish the reamping stuff.

J M Fahey, do you think that speaker load is essential? Could it be something like Weber mass - coneless speaker. Or a speaker completely enclosed in a box not to produce any noise.

My first idea was to get a ss amp with a good distortion tone (Randall, maybe) and use its preamp as tone generator, then "reamping" in the FX loop and use it's poweramp to drive speakers. I think this is a valid approach using the same principles as you both described. Anyway, thanks for helping me with sorting my thoughts:)

Hi,
Yes Palanj your spot on, it is just a fancy hi-teck way of saying how much signal swing is needed on the input
to attain full output. I do wish those technical book writers would stop all the mumbo jumbo and just write
in plain english, as it took me some years to understand what the hell they where talking about.
Just be aware that "Amplification Factor" is in fact another tube term which is not the TC.

I only metioned the TC because it never gets much mention except in a fleeting commentin mag reviews where they
often say that a particular tube amp being tested has a distinct "British or American" flavour/quality/tone.
When I started out messing with valves I scratched my head and wondered what they meant but
It's all about the TC "Transconductance" or kind of like Gain if you don't want to do hard maths.
6L6 is a Tetrode and EL34 is a Pentode. 6L6 pumps 19 Watts and EL34 is 23 Watts. Ok at a glance they might seem
somewhat similar but what about the TC? To the best of my searching a comparison would look something like this.
Transconductance of some common guitar power valves
TC of Tetrodes
   6V6  = 3,800   umhos
   6L6  = 8,000   "
  5881  = 5,500   "     (I think)

TC of Pentodes
   EL84 = 11,200  umhos
   EL34 = 11,200  "
   ECL86= 10,000  "     (ECL86 also called 6GW8)
Once I understood this It became VERY Clear to me why Fender and Marshall Amps sounded so different.
Even though a 6L6 and a EL34 have similar Power Wattage rating they respond in a very different manner due
to the way they transfer that power, the TC.

An EL84 only needs about 30VAC signal swing on it's input grid to achieve full output wattage, whereas a 6V6 needs
more like 60/70VAC swing. they are very different tubes. Which is why you often see Tetrodes using an 12AT7
Phase Splitter as they have nearly 10 times the current ability over an 12AX7. In simple terms assuming identical
Tube amp circuits, an EL84 powered amp is going to distort LONG before a 6V6 even though the 6V6 has more power.

Now the stuff you are probably wanting to know,
I should add the Amptone link focuses more on Power Attenuators but I have just taken that one step further and
found that ReAmping resolves most of the loss found in resistive load attenuators.
It is still not as liquid as the Guytron amp but I have not spent much on this project.

Fahey has given you other options you may wish to try and you never know you may find something
that I have missed but this will give good results and will get you started, It's simple and works.
I'm posting a basic circuit concept that might help get your head around it if your wondering how to go about it.

As to the soak box,
Make R load about 2 to 3 times bigger than the wattage your tube Amp produces as this will keep it warm but
not overly hot. Aussuming 8 ohms output then 3x27R WW x10Watt resistors will be about 9 ohms and that
is close enough for an 8 ohm system. Exact R is not important if anything a little more may be of some benifit,
try not to go less though. This will handle a pair of EL84 tubes delivering say 17 watts max.
Please make sure Any tube amp you use can actually run full bore without issue as some of the modern tube gear
uses underrated transformers and tend to use excessivly high voltages and things can get very hot.
I have read of horror stories so thought I should add a warning.
The level shift is optional but I find it very useful. If the signal coming from the soak is to big and clips
badly at the EQ or second Amp then reduce the parralel 39k R down to 22k and make level shift pot 10k instead.
The level shift is a recent addition and I'm finding very useful but you may find other ideas more useful.
As shown it will deliver a line level out which should interface to any equipment that has line input.

You could plug into the Effects return of another guitar amp if you wish but it will probably be to strong
for the front input of another guitar Amp.
Have fun with it, Phil.

Hi pelanj,  (sorry, i been busy)
          That's great,,then you have some idea of what is possible.
I very much doubt if there is going to be a stand alone SState setup
that will match what you are already using but some here may wish to advise of there setups
as they may have had more luck with tube emulation than myself.

I quote from your 1st post:
I have always found a tube power amp in the signal chain as madatory.
Either being a pure 50/50 style rack power amp (properly biased 6L6's slightly preferred
in the same amp to EL34's) or a "reamping" system, where a low power all tube head
(even any preamp into its FX loop) was run into a load and later amplfied by a 2x12 guitar combo's poweramp 
       
Re the difference between 6L6 and EL34. Do you know what Transconductance (TC) means?
If you wish I can give you a general overview of TC and Why it's so important,
might help you define your sound/tone.

Yes even a small tube power amp can be used for "ReAmping". Valve preamps WON'T get you the sound
as you need a push pull power stage to do it. The unbalanced PI along with transformer action is part of the magic,
Teemu's book mentions some of the transformer quirks also.
My personal opinion is that the Transformer can't transfer the high frequency hash that rides on the heavy overdriven square wave.
It's Only present on the primary side but magically disappears on the speaker side.
So unless SState can do that It may not sound convincing.
 
I personally use a 10 Watt tube power stage in my ReAmp setup
which is loosly based on the Guytron GT100 concept.

My Signal path goes like this;
Tone box > OD circuit > 10watt PP TubeAmp > Soak/Spk-to-Line > Graphic Eq >
120Watt SState PwrAmp > 15inch speaker (sealed back)
(the first 4 are all home brew gear.)

The result is, Any Tone/Crunch/OD I need At ANY SPL I choose.

Quite obviously there are many ways to do this but as I only have very limited funds
to play with I use whatever I can scrounge from old electronic stuff.

To qualify all this my setup has to compete with a Carvin Legacy,,a Cyber Twin and a couple of F De'villes.
My gear can dial in Exact tones while the others struggle with some of the in between tones. (like Dire Straits)
The Legacy is awesome loud but only with those exotic speakers mine are just no names cheap ones.
But remember I can get the same sound /tone/dynamics at home in my shed,,,, They Can't.
That might appeal to you? 

All my stuff is cheap to build,ie, my graphic is an old hifi type cost me $10 at a sale.

Anyway this might give you some food for thought.
Phil.

Hi pelanj,

Before you get too far into it all, have a read of this page as I believe it simplifiys what is often made Overly complex.
Yes I agree Power tube stage is hard to copy with Sstate.

http://www.amptone.com/truesecretofamptone.htm

Does sound like you already have most of the gear needed to do the tricks your searching for.
Cheers Phil.

Your rather LARGE Schematic got me thinking about the pains I went through when messing with Fet ideas some years ago ,,,So this Schem might help you out.
You can run into trouble with noise and this will reduce that issue somewhat.

Also in regard to balanced circuits why not just jump on "Jensen Transformer Site".
Heaps of balanced circuit ideas with explanations on their pages, all free to download and try.
Phil.

Hi,
    In Answer to your Q ,,No it's not balanced output.
Sounds like you need to do some research if you want hi spec bal output.
I believe Rod Elliot at ESP may still have some Bal output ideas on his pages I think.
Might help also if you give us some idea of what you are trying to achieve
as not everone may know what  a Waves GTR3 Preamp is used for,,well I have no idea?
Cheers, Phil.