A small update:
I haven't yet started on a BSIAB... but instead I tried to modify my Dr.Boogey (which I really like) for higher voltages. I'm a metalhead, doh 

For now I didn't change any resistors/caps, but instead played with different types of transistors and biasing. Although I do like it, I will rebuild it using sockets (for resistors/caps) at some points, where I think I could improve the sound (especially source resistors and bypass caps) and experiment further.

Here is another short sample: Dr.Boogey at 15V using a combination of j201, mpf102 and 2n5457 transistors. I did some slight post eq-ing, because I recorded on an open back 1x12 CL80... (this beast loves my vlosed back 4x12 V30)

Until next time..  :tu:

Hehe, I consider all my samples that start as an idea, and end as a mp3 less than half an hour later, quick 

Now this makes me wonder how would a BSIAB (with the full tone stack) work as a preamp at 18V..
I could easily make this a 2 channel amp if it is as good as thor (probably as a "lead" channel).

I think it is time for me to build a "browny"... and experiment further  :tu:

Thanx! 

The amp is coming together VERY slowly. I'm currently ordering LM3886 parts and I haven't even got time to think about enclosure yet. It will probably take me more than a month to finish this thing    But - while tinkering with the thor circuit for the purpuse of my (pre)amp, I *did* finish another one in the usual form: stompbox.

I recorded a quick sample.
Keep in mind, this is guitar > pedal (gain around 11'o clock) > TDA2003 (no tone control whatsoever) > openback 1x12 (CL80) > center mic (e606) > soundcard. There are two rhytm guitars (bridge humbucker) panned hard left/right. The only added "effect" is a slight echo on the solo guitar (neck humbucker) in the center. Please don't be offended by my sloppy playing 

And this is how it looks:

(Maršal is pronounced same as Marshall in our language :tu:)

I think it already sounds pretty balanced (without any tone control), but I still intend to make mine a bit more flexible with a B/M/T(/P) tonestack.

Hello again,

I've had some time today to tinker with this "preamp" powered by 18V. I used the original transistors and adjusted the two trimpots accordingly (first one to 2/3 and second one to 1/2 of 18V). The distortion has increased, as predicted. My previous sweet-spot was around 2 o'clock, now It's around 'noon' (log. gain pot). At this setting I did also notice a tiny bit less bass, which I suppose comes from the new position of gain pot (more treble or less bass, I can't realy tell). I like it!  :tu:

Now that I've tested it with my TDA2003, I will build an enclosure and a LM3886 amp to provide some more 'juice'

I might also add another input "low gain stage" using MPF102, and make the original and this lower gain switchable (A/B). I could even use double inputs (high/low) as an homage to JCM800

I'll report back! 

Thank you both very much!  :tu:

So the 100nF forms a filter with the 1M?
I will try some lower values and see if it changes for the better

Just one more question:
Can anyone help me understanding the "bass boost" circuit? I could not find any similar circuit with at least some explanation. I would really like to have the bass boost engaged at all times, but only if I could somehow lower the intensity. I like the boost, but I would like to reduce it to around half. Is there a simple solution for this?

So the only thing I have to change is to re-set the drain voltage of first two stages? That is great to hear! 

I'm away from home until friday, so I won't be able to try it out until then. I will report back on how it sounds  :tu:

By the way, how would one change (lower) the gain of the mu stage, if lower gain would be required? I found the "original" mu-amp here, but this does not help my understanding of this stage. I can see that ROG added 390R source resistors, somewhat changed the "bias" resistors (two 10k and a 1M instead of two 10M) and the input resistor is changed from 10M to 220k. Does someone have a simple explanation of this configuration?

Hi,

I'm building a small amp (head) powered by LM3886. I will be using "chipamp.com" PCBs for the power amp and power supply. However, for the preamp I want to use a "marshall flavoured" circuit from a stompbox which I really like: Thor (from runoffgroove.com). I've built a few of them, and they are great (at 9V that is). Between the preamp and power amp I would like to have a full (bass/middle/treble) tone stack.

I would really like to run the preamp at 18V to get more voltage gain out of it - so that the tone stack loss wouldn't be such a problem... and this would hopefully get me a bit further from the noise floor. The 18V would be regulated from about 25V (the amps power supply). The preamp schematic is here:



I do understand most of this circuit, but I still need a bit of help, if anyone would be so kind.

The first stage is a common source amplifier (looks like a fetzer valve). Second stage is again a common source amp. With double voltage, I would have to re-set both of their drain resistors/trimpots. If that much gain would result in too much distortion, I would use lower gain jFets and source/drain resistors would be replaced accordingly.

So far so good... but now comes the part I don't understand: the Mu amp 
I've searched the internet and couldn't find any understandable (for me) explanation on how is this thing biased and how are some values chosen (for example 390r on source). Is this thing supposed to work with higher voltages without modifications, or do i have to change anything? I suppose higher voltage would give me greater headroom?

After that you can see an opamp biased at half the supply. I doubt this part of the circuit needs any changes. Maybe I could use the other half of the opamp as an buffer, to help drive the tone stach that will follow?

Any help would be much appreciated! :tu:

Quote from: polo16mi on February 08, 2011, 09:09:51 PM
But one more question remains.... there are a lot of kind of magazine paper. To make an example, wich one to use? Say.... similar to newspaper? I mean... some magazines papers (inside pages, of course) looks similar to newspaper.

Yep, this thin ones work the best (= are very easily removed, soaking in water)

I found that the best of them is an advertising brochure, that I get in the mailbox every day
It is very thin, what makes it somewhat difficult to print on - but I tape it to a harder paper and print that way :tu:

Quote from: joecool85 on February 08, 2011, 02:18:21 PMNot the covers, but the thin inside sheets.  I haven't tried it myself, but evidently is transfers the toner very well.  You just soak it in water after the ironing to get the paper off and you're done.

Indeed it does. I used photo paper for a while, but returned back to magazine paper for it's simplicity.

While my photo paper needed no soaking afterwards, the timing and iron temperature was just too tricky to get right every time... with magazine paper I just set my iron to "middle" temperature and press for 2 mins. Then I drop it into cold water and gently rub the paper off with my fingers - and it's done.
(then I clean it with acetone and coat with flux) :tu:

Have you tried it with a battery?
By your description, this could be caused by a "bad" power supply (and/or a ground loop), as joecool already stated.

Try a battery or another power supply  :tu:

I think it will turn out pretty good...
I was shocked today when I first noticed that resistor "color code" actually changed with resistors value  :tu:

But there is one thing: pleeeeaaase, I beg you to offer some way of disabling the stickyness
Version 2.x had the "sticky points" as default, but offered a "disable" option.

This sticky points always make me crazy  xP


ps: also, I kind of miss the "draw rectangle" option. I used it a lot - mostly to draw the "ground planes".
pps: I just found out I could do the same with the "blank boards" colored in black 

For better understanding of what I was trying to do,
here is a snapshot (from 2.x version):

Thanx!

I've seen the ENGL thread, but somehow missed the V30 simulator :loco

Looks very interesting do you maybe have a sound sample?
I've been meaning to build a speaker-sim for some time now, I just might give this a try!

My vote also goes for Dr.Boogey.

I haven't tried Mensur's version, but even the standard Gaussmarkov version sounds great to me :tu:
Although it is more common to build it as a "distortion stompbox", I actually did it as a preamp for my practice solid-state amp (TDA2003). If you want to hear it: I made a short sound sample with all knobs at 12 o'clock = 50%. I used a 2n5457 for input transistor (Q1) and for buffer (Q5), the other three are J201.

You can clearly (pun intended) hear that even with gain at 50%, it is distorted as hell (a bit too much for my taste) 

I usually use it with lower gain and somewhat more scooped eq, and It sounds realy great (I use Ibanez with dimarzios, and Marshall 1960AV cab)

Hello again,
I have another question for those who know their stuff   8|

I'm in need of a "signal splitter" with separate volume controls - and what I found is THIS little circuit, which seems to do more or less what I need.

There goes my question: is there an "easy way" to use the schematic of the previous circuit (DC coupled amplifier+buffer) and add a couple more buffers (buffered outputs)? I know that a gain stage + jfet splitter should work, but would DC coupling also work here? I was thinking of using the exact same circuit as before, but using three (instead of one) identical buffers (schematic below). Is this doable?



I won't modify the previous "gain+buffer" build, this will be an all new project in a separate enclosure, so I can start from scratch

Thanx in advance  :tu: