(http://milas.spb.ru/~kmg/files/projects/slp/photo/front1S.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/photo/front1.jpg)
(http://milas.spb.ru/~kmg/files/projects/slp/photo/rear1S.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/photo/rear1.jpg)
(http://milas.spb.ru/~kmg/files/projects/slp/photo/frontS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/photo/front.jpg)
(http://milas.spb.ru/~kmg/files/projects/slp/photo/rearS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/photo/rear.jpg)
(http://milas.spb.ru/~kmg/files/projects/slp/photo/insideS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/photo/inside.jpg)
Preamp section:
(http://milas.spb.ru/~kmg/files/projects/slp/SlpfSchS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/SlpfSch.pdf)
(http://milas.spb.ru/~kmg/files/projects/slp/SlpfLutS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/SlpfLut.pdf) (http://milas.spb.ru/~kmg/files/projects/slp/SlpfCompS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/SlpfComp.pdf)
(http://milas.spb.ru/~kmg/files/projects/slp/SlpfSoldS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/SlpfSold.pdf) (http://milas.spb.ru/~kmg/files/projects/slp/SlpfSold1S.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/SlpfSold1.pdf)
Volume controls & tonestack has standard values like in original tube prototype MARSHALL 1959SLP (http://milas.spb.ru/~kmg/files/schematics/marshall/1959SLP/1959SLP1.gif).
For PA is used "Fet power amplifier with transformer output" (http://milas.spb.ru/~kmg/fetpa_en.html) 40W version.
Hi KMG, congratulations on your impressive work.
Indeed , you really are a "Fet man". Fantastic amp! I whish i could do something like this one day...
I can't tell by looking, but is this a master volume amp or straight forward plexi? If it isn't master volume, can it be easily modded to be? Also wondering if it has an effects loop? It's quite an impressive set up nontheless. I hope to have the skill to build one someday. That's a really neat looking rig, and if it sounds like a "real" plexi, you've built a masterpiece! Guys like you and Mr. Fahey are truly artists when it comes to this stuff. I am in awe of your talents. Major manufacturers would be wise to swoop in and hire you guys. Astonishing, to say the least!
QuoteI can't tell by looking, but is this a master volume amp or straight forward plexi? If it isn't master volume, can it be easily modded to be? Also wondering if it has an effects loop?
Yes it`s mod of standard Plexi, added master volume after tone stack & passive (because preamp has low output impedance due to source follower at output) loop.
(http://milas.spb.ru/~kmg/files/projects/slp/RegsS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/Regs.pdf)
(http://milas.spb.ru/~kmg/files/projects/slp/LoopS.jpg) (http://milas.spb.ru/~kmg/files/projects/slp/Loop.pdf)
Wow man!!! Awesome work!!!
It´s look very professional. :tu:
Perhaps can you post some sample sound of it?
Quote from: polo16mi on January 27, 2011, 01:03:03 PM
Perhaps can you post some sample sound of it?
I second that motion.
I'm not a good guitarist to record samples. Wait untill my friend will come to visit me.
Quote from: KMG on January 28, 2011, 07:01:48 AM
I'm not a good guitarist to record samples. Wait untill my friend will come to visit me.
Fair enough. Although I've put up clips of my less than stellar playing (and gotten razzed for it).
Quote from: KMG on January 28, 2011, 07:01:48 AM
I'm not a good guitarist to record samples. Wait untill my friend will come to visit me.
I´m no so far away of your playing skill, but i think that anybody that stand up front a Marshall can´t resist to play (and want to ear too) is a A5 chord at full power 8)
I'd like to hear a Am to G progression hammered out a la VH's Aint Talkin Bout Love (the greatest song ever!) Seriously, that's a lick I try any amp/guitar/pedal etc. with. If I can crank the gain but still get that twang of the Am going, I'm thrilled. Some triads and barre chords helps too. High gain scooped stuff is fairly easy to achieve as long as you stick to power chords-bigger more complex chords that retain clarity at high gain is or should be an amp builder's goal along with "flavor" or signature tone for lack of better words. Last but not least, I dig straight forward aesthetics that have a unique, trademark look. Mr. Fahey's amps have a very nice look that is very singular but under the hood the modular, retrofittable aspect to his designs are something no major players have thought of. The right promotion of that aspect alone would sell mountains of his product. Whirlpool saw that wisdom 20+ years ago when they designed their direct drive washing machines and it earned them some 80% or so of the market. That coupled with brute strength along with ease of servicability truly put them at the top of the game. If it aint broke, why fix it?
Just quitely, ar-hum.
That efx loop is about the fastest way to stuff up an other wise good system.
Never insert EFX loops at that point in the circuit as it will give Trouble down the track :trouble
I'd hate to see such good work go to waste. 8|
Phil.
Quote from: phatt on January 29, 2011, 02:25:19 AM
Just quitely, ar-hum.
That efx loop is about the fastest way to stuff up an other wise good system.
Never insert EFX loops at that point in the circuit as it will give Trouble down the track :trouble
I'd hate to see such good work go to waste. 8|
Phil.
I do not understand what is wrong with the effects loop?
Buffered output of a guitar-level (see the preamp section) is passed through a passive loop in the PA, which also has a guitar-level sensitivity.
Hi KMG,
Sorry if I misread your schematics but they are quite hard to follow.
From what I see your EFX loop is wired as per my rough drawing.
If this is not right then please correct me.
If it is right then you are walking into trouble as the signal can suffer massive loss and the tone controls under some conditions will hardly be working.
Phil.
The tone stack output (J5.3) signal is first fed to the buffer stage (Q11) & after scaling down goes to the preamp output (J6). This preamp output is connected to loop.
I never use signal from tone stack to drive high capacitance loads.
Thanks for the crarification, Tis all good then, :tu:.
Phil.
QuotePerhaps can you post some sample sound of it?
At this point still only reamping samples
Clean 9.9M
http://milas.spb.ru/~kmg/files/projects/slp/reamp/Clean.mp3
Clean wih DRE AL3201 (hardwood studio effect) 10.0M
http://milas.spb.ru/~kmg/files/projects/slp/reamp/CleanR.mp3
Drive 12.6M
http://milas.spb.ru/~kmg/files/projects/slp/reamp/Drive.mp3
Yes!!!! I like it!!! Very cool sound!!! :tu: :tu: :tu:
Maybe i´ll copy and paste!!!!
Excellent tones coming from that circuit. Who needs tubes anyway?
QuoteExcellent tones coming from that circuit. Who needs tubes anyway?
Amen.
Besides, that's the Forum's idea, isn't it? :tu: :tu:
Wow, I like the sound samples.
Quote from: J M Fahey on February 04, 2011, 09:46:27 AM
QuoteExcellent tones coming from that circuit. Who needs tubes anyway?
Amen.
Besides, that's the Forum's idea, isn't it? :tu: :tu:
It wasn't originally, but it is a wonderful outcome that has just started and hopefully continues to thrive. No point is using inefficient (lots of watts go to the heater and not the speaker) tubes that are getting harder and harder to come by since they aren't being manufactured by many places when you can have a much more efficient and great sounding FET device. I love it!
Two short samples with tube screamer in front (at first part of each file TS is bypassed for reference)
Neck
http://milas.spb.ru/~kmg/files/projects/slp/reamp/BoostNeck.mp3
Bridge
http://milas.spb.ru/~kmg/files/projects/slp/reamp/BoostBridge.mp3
Quote from: KMG on February 04, 2011, 11:30:55 AM
Two short samples with tube screamer in front (at first part of each file TS is bypassed for reference)
Neck
http://milas.spb.ru/~kmg/files/projects/slp/reamp/BoostNeck.mp3
Bridge
http://milas.spb.ru/~kmg/files/projects/slp/reamp/BoostBridge.mp3
I can't believe the metal tone coming out of it on the bridge pickup with the TS on! That seriously rocks!
Sounds amazing! The schemo OTOH looks like a mace...
Maze?
No pain no gain ;D
s#it! i always confuse those. which one is where you put mice in?
Maze: labyrinth
Mace: something to break walls, stone, or your head. Also "tear gas"
Quote from: J M Fahey on February 05, 2011, 02:55:02 PM
Maze: labyrinth
Mace: something to break walls, stone, or your head. Also "tear gas"
Well, that schemo broke my head...
I was used to the typical 2k7/680n, 820/680n, stuff like that. Now I don't see any of these values anywhere (same thing goes for the JCM800. What if I want to add an extra cap? Like a 680n in parallel with 820r before the tonestack? I'm lost.
Each stage of preamplifiers was designed with the help of this "test equipment".
(http://milas.spb.ru/~kmg/files/misc/StendS.jpg) (http://milas.spb.ru/~kmg/files/misc/Stend.jpg)
Right part is the tube version of the stage with input and output interstage circuits.
At the FET part, I first set up the gain below the cathode circuit cutoff frequency of the tube stage by adjusting the resistor at the FET source (adjusting biasing voltage at the same time to keep operating point).
After this I added a correcting RC circuit at the FET source to adjust gain above the cathode circuit cutoff frequency of the tube stage. R define gain, RC define cutoff frequency.
Frequency response i checked by "RightMark Audio Analyzer".
Thats why you don`t see original values of components in source networks.
The last thing I adjusted the parameters of the "scalable diode" part to provide adequate "grid" limitation.
That's the way to go !!! Congratulations.
I am not quite loved in some Forums because I always state that the ROG approach of taking a "Famous" circuit , replacing the tube with a FET (a *very* different thing), feeding it 9V instead of 250V (a *very* different thing), and loading it with "100K" is *not* the way to capture the "old sound"
Far from it.
To boot, that "100k" is not a resistor but a 10 turn potentiometer or variable resistor, which gets adjusted to any value between 1K and 47K (a *very* different thing) whichever is needed by that particular FET.
And they expect to reproduce the original, vintage amp sound.
No way!!!
QuoteI was used to the typical 2k7/680n, 820/680n, stuff like that. Now I don't see any of these values anywhere
And you won't except by chance.
And those values are not "magic" or "sacred".
Fact is, active elements (tubes, transistors, FETs, MOS) have what's called a "working point" which is established by Bias.
You need to set the bias needed *there*, not something used in an absolutely different place.
My Father was a Country Doctor; he was often approached by somebody who asked him to prescribe "the "red pill" which had been so good for a neighbour's ilness". Oh well.
Our friend KMG *does* use individual trimmers (unfortunately Fets and Mosfets still are very variable) but he uses them "the right way": in a mini regulated PSU which feeds the correct bias in a variety of conditions, which does *not* adversely affect tone.
A de-luxe approach. :tu:
Quote from: J M Fahey on February 08, 2011, 12:03:54 AMQuoteI was used to the typical 2k7/680n, 820/680n, stuff like that. Now I don't see any of these values anywhere
And you won't except by chance.
And those values are not "magic" or "sacred".
what i was trying to say is that, with those "sacred values", i knew where they went and what to change, add some caps and do some mod (caswell, levi, etc). But now i'm lost. I don't recognize anything. What i *DO* know is that KMG is doing a great job at emulating tube sound. I have his website on my bookmarks and I was mesmerized 'bout his results long before I posted my question about his SS poweramps at this forum (today a posted another question at freestompboxes forum).
I know those values aren't sacred, but that was what i was used to (and I don't like ch-ch-ch-ch-changes)
Quotewhat i was trying to say is that, with those "sacred values", i knew where they went and what to change, add some caps and do some mod (caswell, levi, etc). But now i'm lost. I don't recognize anything. What i *DO* know is that KMG is doing a great job at emulating tube sound. I have his website on my bookmarks and I was mesmerized 'bout his results long before I posted my question about his SS poweramps at this forum (today a posted another question at freestompboxes forum).
I know those values aren't sacred, but that was what i was used to (and I don't like ch-ch-ch-ch-changes)
These "sacred values" are suitable for given preamplifier when using the same tubes. For example if you replace tube on Russian 6Н2П-ЕВ these values will be different for prorer sound.
V/A curves of FETs differs significantly from the tube ones.
If you connect a bypass capacitor directly to the source of the FET, increase of gain will be too large.
You`ll get different frequency response of preamp stage.
Well, that's the issue. I guess some people have this holy grail of a "tube replacement" block that will drop straight into a classic circuit, with the same voltages and component values outside of it. But that is hard, and it's not very forward looking either. KMG's approach is the best I've seen.
I'm used to designing my own tube circuits from scratch (and I don't really care much if other people like the sound of them :) - see http://scopeboy.com/amps (http://scopeboy.com/amps) for details) so the approach suits me fine too. I would just take KMG's building block as a strange kind of tube with its own characteristics. I'm looking forward to trying them with my transformer driven power amp.
KMG: You used an emitter follower to buffer the bias voltage on the FET source. Is the temperature coefficient of Vbe a problem there? Or does it actually improve stability of the circuit? Likewise for the tempco of the germanium diode.
I understand what the Ge diode is for now! :) I thought it was part of the "scalable diode" circuit that emulates grid current. But you said it was to make the cutoff softer, and that makes perfect sense.
I'm sold on the topology, but I'm determined to use only current production parts in my designs, after all, that is the main reason why I'm uneasy about using tubes in the 21st century. So do you think a Schottky would do instead of a germanium diode?
KMG - any chance you can repost the schematic and/or pictures? I can't load the files in the original post. Cheers
QuoteYou used an emitter follower to buffer the bias voltage on the FET source. Is the temperature coefficient of Vbe a problem there? Or does it actually improve stability of the circuit? Likewise for the tempco of the germanium diode.
I did not notice any problem with temperature stability.
QuoteSo do you think a Schottky would do instead of a germanium diode?
No details of the curves for diodes at currents around 1 mA.
So it needs testing.
QuoteKMG - any chance you can repost the schematic and/or pictures? I can't load the files in the original post. Cheers
I Think that is a problem of internet service providers.
Do you see my web page?
http://milas.spb.ru/~kmg/index_en.html
Anyway, there you can download project archive:
http://www.megaupload.com/?d=U2E5TY54
Hey KMG !!
You seem to be involved in pretty complex industrial electronics of the highest level !!
Please tell us something about that.
I'm impressed !!! :tu:
I work for a leading engineer in the development department of Mega-Milas Ltd. We develop a fire alarm systems, information systems and surveillance systems mainly for railway transport.
For example, one of my designs - PCB (multilayer) for the fire alarm server for railway train.
(http://milas.spb.ru/~kmg/files/misc/wwS.jpg) (http://milas.spb.ru/~kmg/files/misc/ww.jpg)
Quote from: KMG on February 09, 2011, 10:22:21 AM
I work for a leading engineer in the development department of Mega-Milas Ltd. We develop a fire alarm systems, information systems and surveillance systems mainly for railway transport.
For example, one of my designs - PCB (multilayer) for the fire alarm server for railway train.
...
Neat! How'd you happen to come across this site anyway?
It's very simple, I was looking for links to my site, found at this site discuss one of my projects and decided to join the discussion.
Quote from: KMG on February 09, 2011, 03:04:06 PM
It's very simple, I was looking for links to my site, found at this site discuss one of my projects and decided to join the discussion.
That makes sense. It's good to have you aboard!
Quote from: KMG on February 09, 2011, 03:04:06 PM
It's very simple, I was looking for links to my site, found at this site discuss one of my projects and decided to join the discussion.
The one I posted at freestompboxes? Dude, I knew this will be the right place for your SS Amps.
On a side note, sometimes I imagine the awesomeness that could be if KMG form a team with Teemu... "The SS-Team" (too bad it sounds kinda nazi)
The story at freestompboxes begins from this topic:
http://freestompboxes.org/viewtopic.php?f=28&t=8037&p=90747
On ssguitar I come after this discussion:
http://www.ssguitar.com/index.php?topic=1981.0
Quote from: J M Fahey on February 08, 2011, 12:03:54 AM
I am not quite loved in some Forums because...
I hope you're not confusing disagreement with dislike. :) Of course, I can only speak for myself in saying I do not dislike you at all. I think you pretty much rock.
Quote
I always state that the ROG approach of taking a "Famous" circuit , ....
I've always agreed about your criticism of ROG and others FET biasing schemes. It just seems to come across as a bit smug when you do so rather than as giving constructive criticism. Of course, I could be totally misreading the attitude in your criticism. You're obviously an electronics bad ass. I think the guys at ROG definitely know a lot more than your average hobbiest, but they're certainly not in the same league as you or KMG or Teemuk, etc. So when you're hard on the ROG guys, it almost sounds like a professional athlete talking trash about how a high school football team sucks. Or maybe a physicist telling an elementary school kid that he sucks at math. Once again, I might be totally misreading the intent behind your criticism.
Be patient, guys. All ideas have a right to live.
IMHO, one important thought:
Tuning the stage for different FET parameters by changing the resistor at the drain will also affect stage gain and its output impedance (which affects the frequency response of schematic).
It impairs the schematic repeatability.
In my version, of course more complex, adjusting does not affect gain and frequency response of the stage.
"Nothing is perfect" (C) Saint-Exupéry. ;)
Absolutely agree. One of my favorite circuits, the Dr. Boogey, sounds pretty good, but I hate how it too uses a trim pot for the drain resistor to adjust the bias. This makes the problem with variation in FETs even worse. I've been toying with a variation using trimpots for the source resistor instead. Don't know if it will be much better, but doing so might give more consistent results. Obviously still not as cool as your biasing scheme, but with my time and resources, I've got to stick to simple. :) Simple might be ok for the Dr. Boogie concept anyway. I don't know that it is as critical in that circuit that the jfets clip just like tubes.
Some time in the future, though, I might try to build one of your designs. The sound samples sound bad ass!!!
Dear Rowdy.
I'd love to clarify my position.
Let me use your Sports analogy, which I find interesting.
I do not see myself as a Pro Football player laughing at a High School team; that would be a totally useless (and childish) attitude and would not help them at all.
Rather consider me an old, grumpy, seasoned Trainer, yelling "c'mon guys ... faster .... faster ... catch that ball ... run ... show your training ... don't be lazy !!" :trouble and so on.
The drain trimpot "solution" *is* being lazy, there's no other way to put it.
If you can find another word to say it, please do, I'm open to suggestions.
In fact, I *do* use Fets as gain blocks since the early 70's, have built "Twin Preamps" with them for clean sound, have used them after some Op Amp stages just to provide "tubey overdrive" ... but I select and bias them !
And I had to work a lot to be able to get some consistent results, because way back then, all we had in Argentina was the locally produced Texas 2A264 , the local labelling for Texas Instruments TIS58.
No fancy MPF102 for us.
The parameters were all over the place; Vp could be anywhere from 1.5V to over 6V.
Idss and Gm would vary as much.
I had to buy 100 of them , build some kind of socket out of a DIP8 one, (no Protoboards way back then), lay a row of labelled tuna cans and start testing and sorting.
Try this, 15 seconds per FET:
(http://img683.imageshack.us/img683/6202/fetmatcher.gif)
Just to see the results of the "lazy" approach and the "simple" one, please build these two versions of the classic "Marshall gain stage" side by side, plug your guitar, then into a clean guitar amp, and play a few chords through each of them.
Please comment . An MP3 wouldn't hurt either.
(http://img220.imageshack.us/img220/6449/fetpre101.gif)
Please see that this humble solution is the simplest way to do it, no fancy math, no elaborate Lab equipment.
It takes practically as much time and effort as the "magic numbers" version, and is *much* more consistent, not to mention that it has more gain and sounds closer to "the real thing".
Why I chose a 2.5Vp FET?.
Choosing among general purpose cheap FETs, that VP value is easily achieved by most; those few closer to 1.5Vp are higher quality ones (higher Gm) and reserved for higher gain stages, if needed; those 3.5Vp and above make bad preamps but excellent switchers.
Definitely you waste nothing, although you should order a few more than needed to make matching possible.
Quote from: J M Fahey on February 11, 2011, 07:32:12 AM
Dear Rowdy.
I'd love to clarify my position.
Let me use your Sports analogy, which I find interesting.
I do not see myself as a Pro Football player laughing at a High School team; that would be a totally useless (and childish) attitude and would not help them at all.
Rather consider me an old, grumpy, seasoned Trainer, yelling "c'mon guys ... faster .... faster ... catch that ball ... run ... show your training ... don't be lazy !!" :trouble and so on.
The drain trimpot "solution" *is* being lazy, there's no other way to put it.
Ok, that's fair. Sorry for taking it the wrong way. As for the rest of the post, it's preaching to the choir. :tu:
Ok, I take back the "preaching to the choir" thing. You're retelling why the drain biasing scheme is lazy is still interesting, and you've added a little extra insight. Good stuff.
Several additional reamp samples at full power (PA overdrive).
http://milas.spb.ru/~kmg/files/projects/slp/reamp/fp/
Congratulations. Very good sound.
Loved the raw ZZ sound and the chunk in Criminal.
Did you use a noise gate on Classic ? Or some equivalent software process?
The best, of course, is Almost.
Thanks for posting.
The only processing is volume normalization for all samples.
OK, thanks. Keep posting if possible, your friend does play well and has a good tone.
Quote from: J M Fahey on February 12, 2011, 08:58:31 AM
...your friend does play well and has a good tone.
I'd say so! I wish I could play like that. Maybe with time.
**edit**
Is "Classic" the beginning to "You Shook Me All Night Long" by AC/DC?
It's not yet my friend, reamp of DI samples downloaded from several Internet sites.
http://milas.spb.ru/~kmg/files/distr/DI%20Samles/
Additional 3 samples:
http://milas.spb.ru/~kmg/files/projects/slp/reamp/fp/Country%20Esque.mp3
http://milas.spb.ru/~kmg/files/projects/slp/reamp/fp/Kid%20Paul.mp3
http://milas.spb.ru/~kmg/files/projects/slp/reamp/fp/LP%20Delay.mp3
Sorry, joining this discussion late. Why the OT in the MOSFET PA? Gilding the lilly or does the bandpass like response and non-linear transfer function of the OT add to the "tube sound"?
I would love to see a FET (JFET that is) design for the preamp.
I have used this source for JFETs - very good process control, screening available and good product offering http://www.linearsystems.com/ (http://www.linearsystems.com/)
QuoteSorry, joining this discussion late. Why the OT in the MOSFET PA? Gilding the lilly or does the bandpass like response and non-linear transfer function of the OT add to the "tube sound"?
Some answers to your question you can find there.
http://www.ssguitar.com/index.php?topic=1981.msg12953#msg12953
Small test "Who is who". Reamp samples of the tube "Bogner Ecstasy" (plexi mode) and the FET Superlead.
http://milas.spb.ru/~kmg/files/projects/slp/reamp/Classic%20T.zip
Thanks for the links -
QuoteLow output PA impedance lead to hard speaker dumping, that doesn`t allow cabinet to "breathe".
Look at frequency response of transformer output fet PA loaded on active load and cabinet (voltage on PA output).
It seems like an OT is an expensive solution to solve the problem - damping factor of a tube vs SS design. What if the "soft clipping" of the signal occurs not in the PA but in the preamp stage?
BTW I have a very good friend who writes and speaks Russian language (he is from Moscow) if you have more papers/information.