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 :duh
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. :tu:

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?  8|

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.

Hi Teemu,
Just pointing out that using the low input does subdue the hiss,
Use of the low input on older type Valve Amps also Stops the signal from going
to big to fast.
This forces the preamp to run clean/cleaner than it otherwise would and now you have
to turn the volume up higher than before,,, So the "power tubes" are now able to do their magic.
[I'm talking pre Master volume Tube Amps of course.]
The Bass was often pretty fat on old Amps and often turned into mud if you cranked them high,
so this was one way to gently pull back the preamp gain.

I think you will find the response curve [on valves at least] is the same shape just down by xxDb.
Of course I'm only using sims.

As your obviously after bright sound then with the addition of one cap right in front of the 68k/68k voltage division, Those old low input sockets can be turned into an Ultra bright Channel.
Yes this trick IS Also Passive. If your interested? And in case your wondering,,
No sadly it does not seem to work on SState Amps.

No I can't see how use of the low input will give you that mud woman tone you speak of,,
If that's what you mean?  Maybe you had a bad input socket?
As for your taste in tone,, well we are all different and we would all be a boring lot
if we all liked the same thing.   
If your after metal you still need to establish the fundermental part
of your sound which to my mind is rock tone with a scooped out mid section.
I have no doubt that there are other ways to get there that maybe better.

With modern tube rigs it's all about multi gain stages of triode fizz and IMO
it's not quite as real/dynamic as the old Amps which needed to be pushed into poweramp dist
to sound good but that's probably why some of those old tube amps are so famous.

There is a whole section on opamp noise in "Art of Electronics" but I have loaned that book out.
Generally I think the story was, spreading your gain over two or more stages will reap better results for noise issues.
Sadly my brain is getting to darn old to absorb and store a lot of complex info.
Cheers, Phil Nambour Australia.

Hi armstrom
Yes I just moved the buffer to the front,, 
It's a 50/50 thing,,,does not seem to make any difference.

Yes I hear what you say one wonders if the buffer needs to be there at all.
That can be deleted also but I figured that Messa know more than me and wouldn't
go to so much trouble unless they had good reason.
I did have the volume wired between buffers just like the Vtwin
but in the end the trim pot does just fine.
Folks like you may have ability and equipment to test which is best.

Also I'm running from battery power and you can chew up power real easy by adding to much.
What confounds me is that with or without an Active front end it seems to work the same.
Which raises the Q. What friggin impeadance does a guitar input actually need to be
able to work in a reasonable fashion?
I get the distinct impression that a lower impeadance may actually be of benifit.
[Especially with hard driven Amps]

I think it is now gaining more exceptence that lots of distortion at full bandwidth
sounds absolutely aweful and some modern tube amps can sound pretty harsh as well.

It was once said that the low input on a lot of the old fenders works better
if you want to run the Amp really loud as it keeps everything together, tighter OD.
68k is ten times smaller that the high 1meg input, Yet the Amp still pumps out close
to the same wattage. [just food for thought]
I personally use the low input on my tube amps more than the high.

I also have a OD circuit that I built from a reverse engineered Nobels Sound studio 1
[a little headphone crunch box from the late seventies.]
It has a non-inverting buffer input with just a 10k series and 68k in parallel.
[so the input imp is probably under 100k]
This buffer drives the main input [a 10k pot] which then goes into a selector
of 4 modes, clean 1/2,  OD and Dist.

While rebuilding I noticed that changing the 68k to the manditory 1meg just makes
the noise and bandwidth increase. This of course makes it a little crunchier
but at the expense of a lot more noise which adds all the harshness,, Yuk!
But my slightly modded rebuild is very pleasing,,lets say I've heard a lot worse.

Back to my tone box,
I know there is the Signal to Noise Ratio issue with my circuit
that being the incoming signal is reduced by 9 to 10 times THEN amplified.
It's open for debate as to which way is better.
If you wack all your gain up front the SNR is better BUT then you've probably
got a whole new set of problems to overcome.

My Vtwin build with a triode frontend was good but triode distortioin was not for me.
It was in fact the powertube stage compression effect that sounded so much better to me.
[it's much richer in harmonic content and I'm glad I went to the extra effort
to work that out].
It was of course while messing with the Vtwin circuit that
I stumbled upon this idea of connecting directly into the tone stack.

So I'm just waving a flag to say: Hey look it works this way also and it's 
a lot less hassle than building a dozen tone circuits like the one you mentioned
and works heaps better.
By FAR The most important lesson I learnt from reading really $expensive$ text books
is that no matter which circuit tophography you choose "there is always something lost
with something gained" and it finally dawns on you that most of the time your just picking
the best of a bad lot.
Once again Murphys law is spot on,,
For every problem you solve you just create another. [There is no Holy Grail].
Phil.

Thanks for that armstrom,
Will pay me to read first ay?  :duh
I now see what you meant.
Hopefully James will still get something useful from it all.  8| 
Phil.

Quote from "armstrom"   
"Having an inverting op-amp as the input stage means that your input impedance
is dictated by the inverting input resistor."

No I think you will find it is not that simple,,Heck Electronics would be easy if it was!
ROG seems to like hanging 1meg resistors off just about everything.
If you search it out the 1 Meg is Also in parallel with The internal impeadence of the opamp ,,,   [from what I've read, some are dismal]
the volume pot on the guitar the PU and probably the cable as well.
Now the maths does not look so easy ay?
Someone better qualified than myself may wish to add comment on that.

Yes you get bigger signal with 1Meg more bandwidth and then spend forever trying
to get rid of noise issues and working out how to get rid of high freq hash.
Oh yes I also used to subcribe to that thinking but I've learnt that
kind of design is plauged with noise issues.

Just using the 1k per volt rule of thumb tells me that an opamp with 10volts supply
only needs about 10k across it's input. I know it's far more complicated than that,,,
but Think about it?
a Thermionic valve is a high voltage, high impeadance, low current device
While a transistor is a low voltage, low impeadence, high current device. humm?
The amount of opamp circuits that just use valve values as a rule of thumb
is showing how limited some makers are, they obviously don't do much research.
Opamps are not Valves. That is why if you notice 10<100k on opamps and 100k<1meg on valve circuits.

As I said I did try my circuit in many ways and a buffer frontend IMHO sounded worse.
Putting the buffer "After" tone allows the next Gain section to run at a much lower imp.
Thereby reducing the colletive noise. [Check out Mesa Vtwin opamp section to find
a lower noise technique and BTW Yes I've built a Vtwin circuit]

My circuit develops a 30 to 35Db notch cut at 400HZ!!! [give or take a few db]
now try to get that from tonemender circuit and you will be waiting a long time.
I took the time to sim tonemender for you and you are lucky to get 10Db cut
at 200 HZ with midrange at zero.
BTW the 1meg after treble does nothing as U1b's positive terminal
is already getting DC Ref via the pot chain.

The 500k gain pot Alone would make the tonemender a noise prone circuit.
So If that is what my circuit has to compete with then I am not worried.

Heck it is simple,,,   if you want tone control build one,,
if you want a gain stage?    build one of those as well
but jezz don't try and do it all in one stage.
To much gain at the front will likely stuff up the tone control section anyway.

Gain alone sounds crap by itself is unlikely to produce good tone,
Just sim some famous tube circuits and you might get a fright when
you see how little distortion is in the preamp stages of those Marshall Amps,,,
as most of it is happening in the output stage. Sadly not easy to do with all SState circuit.
The voltage gain is built up over stages one being a LOSSY tone section.

The whole point of this was to add a Tone Stack THAT ACTUALLY WORKED
and did not raise the signal level much past what went in,,
ie 1 to 1, So only the tone is altered. The reason I built this was to get around
the often pathetic tone circuits used in SState Guitar Amps. [and ROG just copies them]

The famous [and much copied] TS9 circuit has a DC rolloff cap connected
to a pot for some basic and rather wonky tone control, Trying desperatly to put tone
and OD all around one opamp. The TS9 circuit has been done to death and no one has woken up to the simple fact that it's not enough by itself.
Try my circuit before your fuzz boxes, you might get a big suprise at how much more control over tone and your OD you will have.

You're obviously more into the teck maths stuff than I am, and good on you for picking
up on some of the details. Hey it's just a hobby for me and I'm not promoting anything.
I still can't believe this circuit and how well it works,,, Again It just does.
I have ten very happy musicians who are smiling knowing that you can't buy this tone at a music shop.
I only mentioned the noise issue because Most learners would likely just stick in a 500kpot  [To much ROG] thinking Gain, gain and more gain and then complain about the noise. THEN Blame my circuit.       OBVIOUSLY you have not built my circuit.
I'm not that good with maths and I do not propose to know ALL. It's taken me 2 years
to even build up the courage to post this and make comment.
I'm quite aware that some folks are way better with teck stuff and will laugh at my circuit and I have no doubt that like ALL electrical circuits there will be limits/flaws somewhere.
But everthing it gets plugged into is greatly improved.

Keep in mind with ANY of these passive tone circuits,
They do not produce gain it is only by creating large loss at different freq
that any real tonal advantage can be had. [And it is uniquely different if you get it right]
The steeper the mid notch the better it will sound as big shallow scoops don't work.

All is well,, Phil.

Experienced builder?   Na! I'm just a mad hobby geek

A Graphic EQ is usefull but prolly not at the frontend.
Depends A LOT on what type of music you are shooting for AND TONE in general is all rather subjective..  Your idea of great guitar tone and mine may well be worlds apart.

That said if you want the classic Rock tones and you only have a SState Amp then here is one way to do such things. [see schematic]
This gives almost Zero distortion but does indeed nail the the tone shape needed for rock. [I've found that distortin is better at the end anyway.]
Though it is not common practice the old valve type tone stacks don't actually need an active front end, [ie, meaning a valve or transistor] They may well work more true to tone without the loading of a previous active stage,,, that of course is open for debate and I'm not about to argue with those who don't agree....
It just works great and I have built about ten of these in the last 2 years and sold everyone I have made. [cept for my first one]

I have come to realise that the "Shape" and "Lossy nature" of those old tone stacks used in tube Amps is part of the magic ingrediant  and inserted in front of most SState guitar amps will improve the realisuim sometimes greatly so.  [Works on some valve amps also]

My Alesis Micro EQ [active parametric EQ] cannot pull this tone shape and believe me I've Tried hard to find fault with my circuit.

Pros, improves the big mid notch dip almost non existant with some SS Amp tone circuits.
Cons, oh bugga there is always a down side.
Because of the "passive high imp input" this will amplifiy resistor Noise if you overdo the gain. so Metal resistors and low noise opamps are needed.
I did try it with an Active front end but noise is still present at high gain ,,somehow it sounds better as shown,,, feel free to improve it if you have the knowledge that I do not.
Hey it's only a hobby for me.

I've opted to use the classic HiWatt tone stack as it is by far the best of them but you can use any of those old tone stacks if you wish.
Fiddle around with different values by all means to refine it to your particular needs.
For those that wish to use the original HiWatt Values be very aware that the Bass pot is 500k Log and will deliver a tiny bit more bass below 100HZ But it MUST be A TRUE LOG ,,not the modern wannabe fake log type.
I hardly see the point as the bottom string on guitar is 82HZ so you won't notice any loss.

If you want huge midrange honk like say british valve amps then it may not deliver what you are after but still this will cover a lot of tonal ground that most tone circuits can't.

Be very aware that the overall end result of any tone is the culmination of many tone shapes all slightly and sometimes dramatically changing as the signal passes through each stage of the amplification system.
At nearly every point in these circuits there is tone shaping happening [intentionally or not] It's not just the tone stack.
This schematic is basic and assumes you know how to develop a bias voltage and no bypass switching is shown.
Use the lowest noise spec opamp you can obtain for improvement but I use the TL072

So in answer to your subject,, EQ as a pre-amp,,, Well I think this would qualify
I use mine in front of a rather complex setup and Believe me I know when it is bypassed
out of the signal path.
Hope you find it useful. Phil Nambour Australia.