|
Post by ccoleman on Sept 30, 2006 9:00:18 GMT -5
John that's awesome !!! Much appreciated... +1 for you. Looking forward to your posting (and receiving my parts so I can put it together!!).
|
|
|
Post by JohnH on Sept 30, 2006 23:49:59 GMT -5
ccoleman I've put the schematic info in the schematics page, where it will be easier for others to find: Are you OK reading the schematic? guitarnuts2.proboards45.com/index.cgi?action=display&board=schem&thread=1159677238Now in that posting, I have put down the prefered values that I believe are optimum. Many are not in your kit, but they are mostly not very critical at all. So to use values from the J201 kit that we discussed, I would recommend the following: R1 82k (slightly more current draw, but even more capable of being loaded) - or 120k, to save a bit more current - still very robust output R2 2.4k R3, R4 2.0M C1 use 2 x 5000pf ceramic disks in parallel, to make a 10,000pF = 10nF cap. Add a third if you want to go to town and keep every drop of bass response, but I could not hear a difference. C2 use a 10 uF electrolytic, with positive terminal facing R1 C3 - use another 10uF, but 22uF or 47uF would also be fine. good luck John
|
|
|
Post by ccoleman on Oct 1, 2006 9:26:47 GMT -5
Look great John! I cant wait to put it together when the kit arrives. Speaking of the kit... I notice it includes a 50K full size pot. To be honest, when I saw that part, it got me thinking about being able to dial in a boost to the signal, to overdrive the input to the amps and pedals, and have the ability to get a new kind of distortion from my rig, which to date has been exclusively reveiving standard small votage (1V max when you really whang on the strings !!) guitar pickup signals. So is it possible to modify your circuit to induce some gain knob to boost the output with the 50K pot in the kit ?? The idea I have is the same as how the guy, in the link below, uses the DOD FX-10 Bi-Fet Preamp (which is made for boosting acoustic guitars peizo pickups) to overdrive the inputs to the Tubescreamer and the Vox amps. guitargeek.com/rigview/49/
|
|
|
Post by JohnH on Oct 1, 2006 16:26:42 GMT -5
Nothing is impossible, but it needs a different design. The design that I did inherently cannot produce any gain. To do what you describe would best be done with another JFET stage before the buffer, configured for the production of gain, rather than low output impedance. Current consumption goes up, noise increases, although only very slightly. Theres risk of clipping within the circuit if you push it hard (although JFETs sound quite good doing this) 50k would not be my choice of pot for controlling it however - more like 250k, but it could be done.
It works, and I have built one, but here is where I got to:
The pure sound of the guitar was not quite as perfectly rendered via the multi-stage unit as through just the simple buffer. And the ability to engage gain puts more controls on the guitar, and more options that you might want, adding more knobs. Eg - the same circuit with gain, can be configured as a treble booster - for a sizzling overdrive.
So for myself (and each to his own), I concluded that I wanted to keep the circuitry inside the guitars as simple and pure as possible, and all the other things that these circuits can achieve is best done with stompboxes. The function of the internal buffer is just to get the pickup signal out and down the cord with as little adulteration as possible.
So a mixed answer. You have to decide what you want.
John
|
|
|
Post by JohnH on Oct 1, 2006 17:20:22 GMT -5
further to previous - if you are still interested in gain, you should check this out: www.runoffgroove.com/fetzervalve.html#8This is a circuit, aimed at modelling the characteristics of a tube front end, using a J201, with x7 gain max. It will clip, but in a good way. What impressed me was that they have really gone right into all the parameters of its design. There are other variations possible on this theme, between this Fetzer design, and the Tillman design, whch are both 'common source' configurations. John
|
|
|
Post by ccoleman on Oct 2, 2006 11:11:04 GMT -5
Hey John.. good point. You are right maybe it would be best to keep the circuit inside the guitar as simple as possible.. and just use a stompbox for boost.. I found this pedal, it is only $20 and does boost with tone for the sizzling overdrive you mentioned. But if I am getting booost it would be great that it be as clean as possible, and if overdriven internally, that it sound as sweet as possible.. I don't know if these pedals are particularly carefully engineered for that... ?! www.behringer.com/PB100/index.cfm?lang=ENG
|
|
|
Post by JohnH on Oct 2, 2006 17:34:22 GMT -5
It looks like it is intended as a clean booster. For $20, it might be worth a try. Does anyone know how durable Behringer boxes are? Jl
|
|
Channelman
Meter Reader 1st Class
Posts: 62
Likes: 0
|
Post by Channelman on Oct 2, 2006 18:17:49 GMT -5
Behringer also seem to have a 7 channel graphic equaliser as well at the some price of 15 UK Pounds. www.behringer.com/EQ700/index.cfm?lang=ENGGain is also adjustable +/- 15dB I couldn't buy the parts for that price. Channelman
|
|
|
Post by ccoleman on Oct 2, 2006 19:08:28 GMT -5
That's because they make the parts (and assemble them as well) with chinese prisoner and child slave labor ! What a world we live in.... sorry for the interruption, back to our normally scheduled guitar programming !
|
|
|
Post by ccoleman on Oct 2, 2006 19:09:38 GMT -5
John I understand that the behringer boxes are nearly direct copies of the ibanez and roland/boss stompboxes and thus should be quite reliable..
|
|
|
Post by JohnH on Oct 2, 2006 19:39:36 GMT -5
Yes, but if you 'stomp' on their 'stompboxes', do you get the bad kind of 'crunch' that we dont like? J
|
|
|
Post by UnklMickey on Oct 2, 2006 19:50:53 GMT -5
Yes, but if you 'stomp' on their 'stompboxes', do you get the bad kind of 'crunch' that we dont like?J good point John, in stompboxes (as well as tubers) 'crunchiness' is not always a good thing. if ya didn't get the parenthetic portion of that statement, don't worry about it -- inside joke. unk
|
|
|
Post by ccoleman on Oct 2, 2006 22:27:46 GMT -5
I believe that the behringer stomp box housings are made of the similar low-grade "pot metal" that the boss ones are made from (and it is definitely made from neither stainless steel nor even any grade of steel !!), so I'm going to bring my modified guitar containing your design J201 fet preamp to the music shop and try out that PB100 overdriving a tube amp channel..
|
|
Channelman
Meter Reader 1st Class
Posts: 62
Likes: 0
|
Post by Channelman on Oct 3, 2006 6:18:58 GMT -5
John I understand that the behringer boxes are nearly direct copies of the ibanez and roland/boss stompboxes and thus should be quite reliable.. Looks like Behringer 'saw you coming', the site has the following notice.... "Products mentioned herein are exclusively BEHRINGER products and are not in any way associated with and have not been approved, licensed, sponsored, endorsed, designed or manufactured (or anything else for that matter!) by anyone other than BEHRINGER."
|
|
|
Post by ccoleman on Oct 3, 2006 8:20:16 GMT -5
For real, Channelman.... there was actually a pretty huge scandal recently when Behringer showed up at the NAMM conference, with dozens of BOSS clone stompboxes, same color paint, same or nearly same circuitry, same font printed on the outside, and said these were homages to their BOSS counterparts !! They never even asked BOSS for permission or paid any kind of royalty or licensing, and I think Roland/BOSS sued them.. check it out !
|
|
Channelman
Meter Reader 1st Class
Posts: 62
Likes: 0
|
Post by Channelman on Oct 3, 2006 8:30:34 GMT -5
Post moved to 'Schematics'....posted in wrong thread by accident . Channelman
|
|