Hello Alexius,
Welcome to the forum  :tu:
First of all you don't need so much components in your preamp.
I suggests to build DC coupled preamp,but here's the answers to your questions:
1.Yes, it would work,
2.By building DC coupled preamp, which also has voltage+current(buffer) gain.
3.Yes you do, capacitors have infinite resistance on DC voltage, hence they stop DC voltage to your pot(input buffer cap),and output(out buffer cap),also they shape frequencies.
4.In that kind of biasing, which is called voltage divider bias(or AC coupled follower), you polarize the gate to half of supply, which means that if you have +/- 10VAC signal, it will pass unaffected(unclipped),without it, if you have +/-2VAC signal it will clip the buffer.
5.Generally, more current, better the buffer, so none of them are good as buffers, but you can try 2SK170.

Here's what you need, as for the poweramp you can put any tube(which would be cool), or solid state amp(chip amps are cheaper and easy to construct)
http://www.ssguitar.com/index.php?topic=1307.msg11388#msg11388

Here's new version of the preamp, with some new mods , MC34063 DC converter, to get 24V from 9V battery, plus it has voicing control, exact the same as Century C170II/2000,plus it has added gain stage to compensate volume drop caused by diode clippers.

The schematic is correct, overdrive channel is direct copy of Egnater TOL series amps/preamps.What OPamp, if you mean second half of DC servo, it must be, or it will oscillate.

Quote from: mgcasella on June 14, 2010, 06:24:48 PM
I found someone locally (a guy named Tom) who will build a ss guitar amp for me and I am psyched

Last week I met with Tom and we ironed out all the details of the amp.  Upon meeting, he realized that my design was a little more complicated than he thought (I wasn't able to communicate all that I wanted clearly via email because I'm not an electronics engineer).  In a few days, Tom should be getting back to me and, hopefully, we'll be ordering the parts pretty soon.

Tom said this whole project should take about one month so I'll keep everyone updated on the progress  :tu:

What kind of amp, how much power, channels...?

Does your amp has 2xTDA7294 chips in poweramp section, or is it discrete one?Take the pics of the poweramp section, we can determine +/- volts by the poweramp, and by the number of winding loops as your uncle said.

Disconnect mains, and secondary wires from the motherboard, and measure DC resistance between black, yellow and red, and second between mains (white and black), and tell us resistances. 

300W  :lmao:, they can write 10KW too, but it doesn't mean that is correct. Rough power can be calculated with this method;
your transformer is EI76x41, so 76/3(we get core dimension)=25.3mm x 41mm = 107W, then 107W x sqrt2 = 75.66W, but this is only a rough calculation, actually real power is much less in real life.

Quote from: f_b_ilies on June 07, 2010, 07:25:27 AM
According to the repair shop the amp is fine, only the transformer burned. Not sure how they figured that out, maybe they are just trying to have me buy the transformer only to realize that the whole thing is broken. It would be great if you could help us, cause we got puzzled by a few facts when opening up the amp:

1. The AC input wires (black&white) don't go straight into the transformer, but onto the motherboard first, where something happens to the current most probably, cause then we have 3 wires (red, yellow, black) going out of the motherboard and into the transformer. First question: what does the motherboard do to the current and why 3 wires instead of 2?

2. The AC connector going out of the motherboard and into the transformer has 2 positions, depending on the AC input (110V or 220V). Which raises another question: what if the 2 transformer types have different specs and the 110V one cannot be used to clone a 220V transformer?

3. The transformer has 5 output wires (2 blue, 2 brown, 1 black), so there are several outputs there. Is it possible to figure them out at all?

My uncle says there are several standards for measuring E&I, I wasn't sure which one, so I'm sending a pic with all the measurements there are.

Thanks

1.Motherboard has a switch probably for two kinds of fuses(one for 110V, other for 220V which is smaller).
3. 3 wires are  positive voltage, negative, and ground, other two are AC mains. That way most if not all modern poweramps are designed.
Your transformer is standard EI76 x 46 which is about 70W of continous power.

Quote from: mgcasella on June 06, 2010, 07:05:56 PM
Thanks but that's not the issue 

I'm having an amp built for me and the guy wants a schematic of the T2 (probably so he cn look at how the tone stack is done).   :tu:

T2 is 4 gain stage preamp,with marshall tone stack taken from the cathode follower, through 1uF/250V cap, and added mid sweep control (25K pot wired in series with slope resistor/33K).

Can you tell me what happens to be a problem, I can help you, I have the schematics but I can't post them.

I agree with Fahey that diodes are not there to clip, they are to prevent noise to come out.
When there is no signal present at the first triode, ordinary noise is from the mains-50Hz.On the first triode is very small 0.000001 volts or so(this is an example), multiplication on the third stage is already enormous(couple thousands of times), so our noise is multiplied too, and it jumped from 0.000001 to 0.15V.The fourth gain stage has mu of 50 times, and PA has the mu of around 30, so 0.15V*1500= 225V of noise(IN REAL LIFE THIS IS IMPOSSIBLE THIS IS JUST AN EXAMPLE!!!).The diodes are preventing that voltage on the third stage, cause their threshold voltage is around 0.6V, until the guitar signal passes (cause he is a lot larger).The 1M pot is letting the signal and the hum (if there is any) to pass unaffected, something like the mix pot.The same goes for the hiss,which comes from parasitic capacitive, high freq. oscillations which comes from uncontrollable gain...
470K resistor after cc cap is there to reduce the gain, and 1nF is forming low pass filter with 1M pot or resistor (JSX/XXX) of 159Hz, so that basically means that freq under 159Hz are unaffected, only the freq's above are(-3dB's). I think this works like this, on the crunch ch. 1nF  cap is not shunting, cause that ch. has a lot less gain than the ultra.When the ultra is engaged cap is shunting.

Here is the new clip:
Hybrid Ultra.mp3

Quote from: pyromaniac_ on May 21, 2010, 01:54:58 PM
Hi, I've tried to find out using google, but I didn't got any convincing answers there. The thing is that I've just found some old vacuum tubes, EC83 and EC82 (didn't remember the fabricate but it doesn't matter anyway). And if I'm right the EC83 is the same tube as the 12ax7 and the EC82 is the same as 12au7. Or not?

Don't know much about how tubes are named and so but I can't understand the point with having two part names for the same tube. So is there anything thing else that differs, or is EC83 just the same tube as 12ax7?

You must be wrong, cause there is no tube with that name, there are ECC83(same as 12AX7, but just Europian name for it), ECL83 which is triode/pentode (almost the same as 12AX7 in triode section, and weaker EL84 on the pentode section). Maybe one of the letters fell off?

Hi guys,
Recently I worked on the amp, and there is no more sizzle,hum,brum or anything...so I made a new clip:
Memmara Hi Gain Ultra.mp3
It's stereo, on the left is modern hi gain tone, on the right it's hi gain marshall mid tone.

Tell me what you guys think?

Can somebody tell me what would be the values for the blackstar amps tonestack with ISF?