I also included trimmers for Q1 to Q4 to allow you to bias each individually to around 4.5-5V. I just selected a trimmer that easily covered the drain resistor shown and so allow you to tweak significantly above and below the suggested resistor value. And again I included an axial cap because there was room for one that I have in stock, but a radial will do the job perfectly well if you don't have the axial.
I couldn't find any videos on this but a demo can be heard here.
And a layout based on the original scheme by GT Labs which John K thinks has a preferable drive control, and also including the original passive values with just a couple of tweaks:
and for those who would also prefer fixed resistors rather than trimmers this version uses the original drain resistor values, but I would suggest socketing as shown so you can fine tune the bias.
Enough with these amp sims already, I`m trying to watch the world cup and you keep posting shit I`ve got to build ;-)
ReplyDeleteHAHA! +1
DeleteLOL yea same here
Vince
Found a video that must be similar to this circuit if not the same http://youtu.be/UHV-DXT4hrk
ReplyDeleteIs this the same as the runoffgroove slow century?
Thanks Mark for the great layout today. Nice very nice. Your site rocks!
ReplyDeleteVince
Hi Mark.
ReplyDeleteWhat software do you use to create your tagboard pix?
jeff
DIY Layout Creator V2 beta. I've got the newer V3 installed too but I prefer the older version.
DeleteThanks.
DeleteYou're keeping me sooooo bizzy!!!
peace.
You can verify this one, however, the Presence control is backwards. Pres 3 should be Pres 1, and Presence 2&3 should connect to Volume 3.
ReplyDeleteand by the way, it doesn't have as much gain/dirt as the demo. it sounds pretty good, but it would be alot better with quite a bit more.
That's great thanks for verifying John, I'll correct the presence pot and tag it. Brymus did mention in his mod notes that it wasn't as gainy as the Krankenstein (which is a very similar scheme) so I'll have a look over the schematic and see what would be the best mod to get a bit more gain out of it.
DeleteJohn, a question came up on the JCM800 thread about the Superlead mode of the DLS, which swaps the 680n cap at Q1 source to 22u. Maybe it's worth trying a larger value for that 1u cap and seeing if it gives you a gain boost
DeleteI tried a 10u in place of the 1u and it doesn't help much, other than making the preamp unable to get as clean as with the 1u.
Deletethe krankenstien schematic doesn't show a drive/gain pot. at least I couldn't find it.
The drive pot is after the first stage with the Krankenstein, and after the second stage in this.
Deletei re-installed the 1u back on Q1 and then replaced the 47n on Q2's source with a 220n and it has plenty of gain now.
DeleteCool, I'll add a note to the layout. Cheers John
DeleteI also noticed that Q3 has smoother gain with the drain at around 7 volts.
Delete......and since trimmers often add noise (hiss) in these type of circuits, I ended up using sockets for the drain resistors instead of trimmers. for my J201s, a 9k1 for Q1, a 33K for Q3, and 56K for the last two.
I noticed that mine sounded horrible (heavily gated) at 18V so I found that a charge pump would be completely unnecessary.
Deletesince this one didn't really clean up well, even with the drive set at it's lowest point, I wanted to see if it would help to put the drive control after Q1 (as in the original schematic). so I completely re-jigged that part of the circuit. the new drive pot is only a 100K log (as opposed to 1meg), and IMO, it's 1000X better that way. it has a TON of gain and can also be run completely clean now.
ReplyDeleteI'll do a layout based on the original schematic
DeleteNow added, along with a version with the original drain resistors rather than trimmers.
DeleteDoes the presence control is responding well on John´s build? If not what to do to omit that?
ReplyDeleteHi.
ReplyDeleteI could assume but you know what they say about that. And I no one has mentioned it yet. Soo.
Is it a misprint, or is 56kk a secret electronic designation of which I am unaware, or should it read simply 56k.
jeff
Yes 56K. My eyboard is on th way ou
Delete^^ joke :o)
Hee Hee Hee!!
DeleteI bilt this thang and added uh 18v bord.....It KICKS ASS!!!
Top uh thu fuud chane.
This comment has been removed by the author.
ReplyDeleteDo you know if the wampler SLOstortion is based on the same schematic?
ReplyDeletehttps://www.youtube.com/watch?v=GP_Cha9YNuU
ReplyDeleteI don´t understand how the trimpot are regulated. Between what pins there are 20K, 50K or 100K? Cheers and thanks!
ReplyDeletehi, i would like to make this pedal, but i don't understand the 100uF long capacitor. I see that it is not electrolyte, I see but do not understand what kind it is. Thank you
ReplyDeletethe 100uf is definitely an electroyltic. the - side goes to ground.
Deletethank you for the answer, it is strangely drawn, I asked myself the question.
Delete