J0K3RX wrote:Great stuff here!! Anybody have an eagle or diptrace schematic of any of this stuff and feels like sharing with me? Would save me a shit ton of time not having to re-drawing the schematics.. I want them so I can design some boards myself.. I will use Diptrace for that but eagle or diptrace schem is fine, I can convert the eagle using the eagle to diptrace ulp tool...
Well... Alrighty then.
Sorry, I have only partial diptrace schms.
Re: AMT - Legend Amp Series 2
Posted: 06 Sep 2015, 07:28
by J0K3RX
Anybody build one of these yet? If so, does it work, how does it sound..?
Re: AMT - Legend Amp Series 2
Posted: 06 Sep 2015, 09:17
by The G
The specific JFETs used by AMT (or JEFT with similar characteristics) are not easy to find and replacing them would require a serious analysis of the circuit to preserve the way it works and sounds.
So I think it will take a while until someone will diy it.
Later edit: Baja, maybe you could do a simulation of one JFET stage modified to use a more common JFET, like a J201?
Re: AMT - Legend Amp Series 2
Posted: 06 Sep 2015, 21:21
by bajaman
I was contemplating building one of these but after purchasing two of them online from the Russian Federation, I decided it was not worth the effort - they are so cheap to purchase and well worth supporting in my opinion. However if anyone did want to build any of these with through hole components the correct fet with identical characteristics to the 2SK208 is the 2SK30(R).
It is most important that you use the (R) idss designation - NOT the (GR) (Y) or (BL) etc. Only the 2SK30R will work correctly in these designs at 9 volts
The J201 is a very poor choice for these designs and MAJOR design changes and supply voltages would need to be made to accommodate it's use
I had no trouble finding a source for the 2SK30R on Ebay by the way
cheers
bajaman
I was lazy, I knew that Bajaman already tried a J201 in a high-gain stage. But his post didn't have nice graphs so my simple mind overlooked it.
Anyway, it's a good starting point for trying other JFETs and other supply voltages. @Bajaman, the datasheets show that the Forward Transfer Admittance parameter is at least 1.2mS for 2SK208 and at least 0.5mS for J201. My understanding is that this is the Beta parameter of the simulation, so it looks the other way around than your spice models. Also, has how does the Lambda JFET parameter (channel-length modulation parameter) variations affects the circuit?
Looking at the schematic, there is some serious engineering going on. I knew about the Shottky diodes from the Legend Amps 1 Series. I see now P-channel JFETs in some kind of feedback loop, also splitting and mixing the signal in various points. Does anyone have a clue about the P-channel JFETs role?
I agree with Bajaman that the Legend Amps 2 Series pedals well worth their money and deserve to be supported. Not to mention I always liked their modular build system. So, if one needs one of these pedals is much more morally correct and convenient to just buy it.
Re: AMT - Legend Amp Series 2
Posted: 09 Sep 2015, 04:31
by J0K3RX
I think Access777 already linked to them but here ya go again anyway...
Mouser and Digikey carry the elusive 2SK208-R now! :icon_wink:
If you don't like the tiny SMD package I found these on evilbay... A very reliable and knowledgeable member on another forum purchase 50 of the 2SK30A-R from this seller and said that they are genuin.
A while back I contacted some other ebay sellers who were selling the Y, GR etc... and they replied back to me saying that they had them or could get them also... so.. they are out there, just gotta dig for'em
Re: AMT - Legend Amp Series 2
Posted: 12 Sep 2015, 09:32
by Ice-9
J0K3RX wrote:If you don't like the tiny SMD package I found these on evilbay... A very reliable and knowledgeable member on another forum purchase 50 of the 2SK30A-R from this seller and said that they are genuin.
A while back I contacted some other ebay sellers who were selling the Y, GR etc... and they replied back to me saying that they had them or could get them also... so.. they are out there, just gotta dig for'em
Thanks , I'm happy with SMD anyway so that option is for me.
Re: AMT - Legend Amp Series 2
Posted: 15 Sep 2015, 19:28
by J0K3RX
Well, I got 500 of'em... now what?
Re: AMT - Legend Amp Series 2
Posted: 20 Sep 2015, 19:59
by Ice-9
J0K3RX wrote:Well, I got 500 of'em... now what?
Get building
Re: AMT - Legend Amp Series 2
Posted: 27 Sep 2015, 11:52
by phatt
bajaman wrote:I personally found the clean channel a bit harsh, so I added a 680pf capacitor in parallel with R19P and a 1.5nf capacitor in parallel with R39P to roll off the extreme top end just like a 12AX7 tube does. I also removed R29P to fatten the sound up at lower levels of the clean gain control - less ice pick effect
cheers
bajaman
I would like to thank Mick (Ice-9) for all his valuable observations and help in bringing these schematics to fsb.
I would also like to add that these AMT LA2 are very nice pedals and react very much like real tube amplifiers that they are modelled on - the designers are to be congratulated for their work
They clean up extremely well when the volume control is rolled back on my guitar and they have marvellous touch sensitivity - i am using my E2 in the effects loop of a Line 6 HD500 and it beats the Line 6 models both in the clean and high gain channels - i have tried for many years in vain to get a good touch response and sparkling clean sound from the HD500 and now at last i have something very close to perfect with the addition of the LA2 E2 pedal. I purchased mine from Russia for US$175 and I feel this is a very low price for such a great pedal!
Well I've been quietly watching this and tube demo's certainly sound good.
First to all who dissected this, Thankyou, Obviously many hours spent working it all out.
At *Bajaman* interesting comment regarding the clean up with guitar volume, Yes does a very good job and better than most. hard to nail that trick in a pedal.
Having just run through all the demos by Burgs at this link;
I have to agree the E2 would be my choice.
Now this might seem nit picking and likely few would notice but it does have a few glitches on all the clips which seems to be a common issue with hi gain drive pedals.
I can't think of a technical term to explain this quirk but it's a stutter mainly on sustained notes or chords.
At above link,,,Glitching at 2:12,,,again at 5:00 thru 5:05
These are only momentary cutouts but they do erk me.
This reminds me of the many postings regarding triode emulation and like ponderings I wonder if this is the limits of fets or ss devices in general?
No matter still a great pedal.
Phil.
Re: AMT - Legend Amp Series 2
Posted: 30 Sep 2015, 08:06
by The G
phatt wrote:[...]
Now this might seem nit picking and likely few would notice but it does have a few glitches on all the clips which seems to be a common issue with hi gain drive pedals.
I can't think of a technical term to explain this quirk but it's a stutter mainly on sustained notes or chords.
At above link,,,Glitching at 2:12,,,again at 5:00 thru 5:05
These are only momentary cutouts but they do erk me.
This reminds me of the many postings regarding triode emulation and like ponderings I wonder if this is the limits of fets or ss devices in general?
[...]
Phil.
Phil, maybe is my hearing - I just cannot hear the glitches you're talking about. I made two cuts from the clip audio track, around the times you mentioned: 2:06 - 2:18 4:50 - 5:15
phatt wrote:[...]
Now this might seem nit picking and likely few would notice but it does have a few glitches on all the clips which seems to be a common issue with hi gain drive pedals.
I can't think of a technical term to explain this quirk but it's a stutter mainly on sustained notes or chords.
At above link,,,Glitching at 2:12,,,again at 5:00 thru 5:05
These are only momentary cutouts but they do erk me.
This reminds me of the many postings regarding triode emulation and like ponderings I wonder if this is the limits of fets or ss devices in general?
[...]
Phil.
Phil, maybe is my hearing - I just cannot hear the glitches you're talking about. I made two cuts from the clip audio track, around the times you mentioned: 2:06 - 2:18 4:50 - 5:15
Thanks for taking the time,, Yes we all hear things differently.
Well it's there to my ears.
As I said, I'm not sure what to call it but the signal does change, maybe just modulation of the frequencies. Some of the lower frequencies are almost farting out. But it's still a very good circuit.
Heck I've heard some big name Valve rigs that do the same glitchy fart thing and I've never liked that sound.
I just want a circuit where the note/chords stay fixed with no modulation or farty artifacts while sustaining.
A lot of pedals actually rely heavily on the fact that they run through a Valve rig where the pedal is really just making the signal bigger and forcing distortion of the valves where as this one (judging by the Vid clips) can do it into a sound card which is very impressive.
Phil.
Re: AMT - Legend Amp Series 2
Posted: 30 Sep 2015, 18:34
by Ice-9
I see and hear what you are meaning, but when looking at the video it corresponds to when he is putting his arm over the guitar to adjust pedal controls, I think this fade in out has more to do with that than anything else. I have one of these pedals and in real life I can't identify any issues with the fade on sustained notes.
Re: AMT - Legend Amp Series 2
Posted: 30 Sep 2015, 20:45
by The G
You're not talking about the thing that Burgs does with his left hand index, are you?
Hope you don't mind me insisting on this , the sound artifacts are really difficult to explain or even point to.
, the sound artifacts are really difficult to explain or even point to.