Ha, I just found some "leftover" clear acrylic based lacquer for wood from a previous (non music) project :tu:
I have just about enough for a few coats... so I'll go with it 

Who said a "metal" amp should be black... it's gonna be bright and pretty

Thanks!  :tu:

As for the regulation: I first intended to use a 12V transformer which would give me about the right voltage after smoothing caps... but then I decided to just use the 15V, 1A transformer, which I already had. And since the TDA2003 datasheet said 18V is the max. operating voltage - I regulated it down to that 

I'm still deciding about the wood though... to stain or not to stain 

Power amp is TDA2003 running at 18V, so it has approx. 5W into 8 ohm, according to datasheet. It was born as as a practice/recording amp and it does it nicely. Plugged into my 1x12 cab it reaches "max. bedroom level" at around half volume. Into my 4x12 with V30s it is loud enough to tear my ears of from a meter or so, hehe.

Just this moment the wood arrived, two days early! 



I will probably glue it together tomorrow  :tu:

Hello!

I've been building a small amp for the past week... and now it is nearly finished (finaly) 
Here are some photos and comments


First I drilled the alu chasis (hammond 1444) according to my plan:



Then I designed the power supply and the jfet splitter (which I later ditched):



Assembled power supply:

(18V for the amp and 15V for the preamp, both regulated)


I then fiddled with the global layout and stuff:



Next was choosing a handle and wood type... and then drawing a plan in 3D (google sketchup):



This was the internal pcb layout...

...until I wired it and plugged it in 
There was just no way in hell my dr.Boogey would cooperate with my small dpdt switch. I used shielded&grounded wire, but the proximity of I/O wires at the switch caused it to oscilate. I then ditched the second preamp and wired the Boogey differently. It is now a "one trick pony" amp, but it sounds really good 
Also, I wired the volume from tonestack directly to amp input. I had some trouble with the splitter, I might try it again later.


This is from today's testing:


After three hours the heatsinks (scavenged from a dead PC PS) were just slightly warm. Transformer was a bit warmer, but still at lower than body temperature... yay  :tu:

Now I'll have to wait until monday for my wood to continue

Comments are as always most welcome!

Well, I certanly don't expect this feedback to perform miracles, but I am eager to hear the difference. I've played valvestates before, but had nothing else to compare it to. I recently recieved LM1875 pcb from chipamp.com for my hifi amp, so I will finally get to A/B both configurations using the same chip. I also have two tube power amps to compare and hopefully give (a personal of course) an opinion about comparison with those.

So, now my exams are finally over and I have time to continue with this  :tu:

I have a couple of new questions, if someone can help me:

1. It would probably be nice to have a line out. Should I keep the original line out, or is it better to have a buffered line out directly from preamp output? Any benefits to one or the other? Buffered line out could easily have it's own volume control.

2. The last stage of my preamp is a marshall tone stack, after that there will be a jFet buffer, followed by a cap and 10k volume pot. Is this 10k pot a problem, or can I run the line from it straight to the 100k input resistor of the amp?

3. How exactly is the gain of this amp determined? (if I find the need to change it)

4. Do I have to change anything if I decide to use a different transformer? (I suppose the original amp has +/-18VAC, I will use +/-15VAC)

Thanks for all your help! :tu:

I would personally put the tone stack after MXR, but otherwise it looks cool 

Quote from: kin0 on June 26, 2011, 12:26:20 PM
my question was is it important which pair goes forward and which pair backward or not?
And thanks for the other answers

If all diodes are of the same type, than no, it is not important.  :tu:

I think I can provide an answer:

1. the red section is "power supply" (led power, filtering, provides a reference voltage)
2. 9V (blue) should probably connect to the + side of that 100uF capacitor at the power supply
3. VB is just a name for a reference voltage; in this case I believe VB is at 4.5V (or half the supply voltage)

Hope this helps. Please someone correct me, if I'm wrong 

I do not have the exact schematic, but as far as I remember, the fetzer valve and mockman are switchable (input and output) and share the volume pot, which then goes into the ruby. Ruby is built without volume pot, since there is volume control after preamps, so the buffer is connented directly to the chip.

And yeah, the whole guitar sound is generated inside the amp. Mind that mockman is basically a distortion pedal circuit, without any gain control. Fetzer on the other side is a clean gain stage, but very capable of nicely overdriving the ruby.

Well, considering I had absolutely non electro-knowledge prior building my first ruby, I thought it was easy :tu:
I later learned It was VERY easy, compared to creating something from scratch, and make it not crap-sounding 

Hm, I believe Sonar was used to record this.

Well, thanx 
That recording was done with the second mini-amp I've done. It's the right one on the photo (the "Mk.II").



Setup was: guitar > amp > 4x12 cabinet > mic > pc soundcard (one left and one right track)


ps: your math is correct, you have to multiply caps by 10 and divide resistors by 10... and remove the second (500k) volume.

Depending on how much distortion you need, you might want to add a gain stage.
(tone stacks lower signal level)

If you play mostli clean-ish, the teemuk's advice should work nicely


I've built quite a few ruby amps (my first diy projects). I did add various tone stacks, but my best one, which I still use sometimes, is a "two channel" amp without any tone controls. First channel is a Fetzer Valve, second channel is a Mockman 2.0 (switchable). I still have a mockman channel sample.

Not bad for a battery powered amp smaller than a cigarette pack, I think

Hi, I need some help/advice.
I am building myself a practice amp. I already have the preamp, but I have yet to build the power amp. I wanted to make something based on LM1875, because I already have the chip and also a 2x15V 30VA toroid transformer (which according to datasheet should give me 15W).

While googling for help about the "mixed mode" feedback configuration I found out that the Marshall Valvestate 8020 features a power amp that seems to be exactly what I was looking for. I decided to borrow that design  8|

Here is the schematic: http://www.drtube.com/schematics/marshall/8020.pdf

What I need the help with is the removal of headphone and line out (D.I.) connections.

Here is my redrawn schematic:

I marked three things I believe I understand: the zobel network, the line out and the remaining headphone out resistors.

I then removed the line out and headphone stuff and got this:
(zobel is drawn very small, so that the main topology is more obvious)


So, I just want to be sure... will this work, or am I doing something wrong?
I've never built anything like it, this mixed mode stuff is all new for me :tu:

EDIT: also, what is the meaning of that 47k and 10uF? I don't see that on the ESP project 

This is the last post here 

Today I connected the whole thing together and did one last test before I dismantle the whole thing and redo it properly (in a nice enclosure). I will not post any photos, because at the moment it looks like a chaotic array of dozens of wires connected to random small pcbs and perfboards all around my table  :lmao:

BUT, I did record two samples that show the different drive behaviour of my two "modes" or channels, if you want.

1. sample: the "modern mode". Preamp is basically dr.Boogey with some minor changes of res/cap values. Majority of distortion is generated before the tonestack. All controls are set to neutral (12 o clock), except for volume, which is at 9 o clock.

2. sample: the "classic mode". Preamp is the same, but with different first gain stage, and bypassed "cold" stage (much lower overall gain). Most of distortion is generated AFTER the tonestack by the mu-amp. All controls are maxed out (to get about the same amount of gain/distortion as in the modern sample).

On both samples the "bass boost" switch was engaged. Speaker was CL80 in an open-back 1x12. Two similar recordings, panned left and right. Riffs are some random heavy stuff, similar to what I play most of the time  :loco

Comments are welcome, as always!

Cheers! :tu:

Another small update:
I feel I've got the sound I wanted, so I decided to focus on the power amp now.
Since this will be a bedroom practice/recording amp, I figure I won't be needing more than 5W. Therefore I'll go with LM1875 with 2x15V, 30VA transformer. Preamp will be powered from + rail, regulated to 15V with LM7815.

So, if all goes ok, the next "update" will be photos/samples of the finished amp and the final schematic  :tu:
(in a few weeks or so)

Hello again! ("spamming" my own thread )

I had a few free days which I used mostly to practice guitar and to play with two of my favourite preamps: Dr.Boogey and Thor. I was just playing around with different voltages, when I had an idea. The Dr.Boogey is basically the preamp section of the real preamp... but the Thor is emulating preamp (common source stages) and the amp itself (mu-amp stage), kind of. So, what I first tried is to connect Thor at the output of the Boogey, but this created just too much distortion. Then I took boogey output and plugged it at the input of the mu-amp stage... and this resulted in a big smile on my mouth 

Now what I have is Dr.Boogey's distortion and tone stack + Thor's mu-amp and output filtering.
This enables me to use less preamp distortion and use a bit of that "mu" juice after the tone stack, and it sounds really good. The tone controls behave much more like a real (hard-driven) amp now. Much less fizz and more agressive treble, plus the thor's "bass boost" does wonders for that deep metal sound. It's currently running at 15V. I'll do a sample next weekend, if anyone is interested  :tu:

This is the combined schematic, which I'm using at the moment: (from gaussmarkov schem.)