OK I get it now with the floating power supply. Thanks

Thanks for that. I will check the voltages. What voltage should I be seeing at pin 4 and 8 going through the resistors and capacitors with a 12 volt supply? I hooked up a guitar jack to the input and plugged in my LP but Im guessing the input signal is too small to reproduce thru a speaker without going thru the power amp as well.

Hi Folks,
Ive finally got round to completing the Eliiot pre-amp and want to be able to test it so I know its working correctly before concentrating on the power amp section which Ive started on.
Ive got a 12 volt regulated power supply that i hooked up to the + and - 15 volt rails. Nothing went bang or got hot so I guess "so far so good"
I looped all the connections that go to the control pots together so there is a circuit through.
What voltage readings/ tests can I take to know everything will work as designed.
Can i hook up a speaker or headphones to hear an input signal?
http://www.ssguitar.com/index.php?action=dlattach;topic=1083.0;attach=620;image

Thanks guys,
This information has been really helpful and has made it clear in my mind how the schematic works now.
Cheers

Hey JM,
Thanks very much for the markings for E caps.
I noticed in the notes (2) that they say opamp supply pins should be grounded.
What would that look like on the schematic? Is this for the +/-15 pins 4 & 8?
Thanks Derek
Notes:
1 - IC pinouts are industry standard for dual opamps - pin 4 is -ve supply, and pin 8 is +ve supply.
2 - Opamp supply pins must be bypassed to earth with 100nF caps (preferably ceramic) as close as possible to the opamp itself.
3 - Diodes are 1N4148, 1N914 or similar.
4 - Pots should be linear for tone controls, and log for volume and master.

Thanks for the feedback JM.
I found once I drew out the pre-amp circuit it looks totally different to the schematic layout. The trick I guess, is in doing it in the most economical way to avoid a birds nest of jumper wires and wasting board space. I laid it out on template paper so the three main tracks +15, GND, and -15 are evenly spaced 6 holes apart and are running full length. I used that spacing so it suits the 220uF polarised caps as they are the largest components to mount.
I then set up the opamp chip so supply pin 8 sits on the +15 line.
I am going to use a socket for the opamp mounting.
Can you please confirm the polarity if I used polarised caps for position C3, C8, C14, C15.
I have plenty of the correct values that Ive pulled from the amp project I bought.

Would 50 volt Bi-polar electrolytic caps be suitable for those extra C3,C8,C14,C15 positions? I looked in my catalogue and they have all those values listed.

Hi there JM,
Thanks for clarifying a few things.
I am not ordering the PCB's as I want to build it on Perfboard which I have plenty of.
I will learn a lot more by working thru in a logical sequence and fitting the components and wire jumpers etc.  I see what you mean, between both opamps all 8 pins are conected to the circuit.
I guess I should draw out the circuit on perf template paper which I found by doing a web search so that things make more sense.
When I first started wiring guitars I redrew the circuit so I could follow it and colour coded the appropriate wires.

Hi there folks,
This is a post I put on the ESP site but havent had much feedback yet. I thought some of you techo toilers may be able to help me.
Im fairly new to full electronics schematic work but have done heaps of stuff with building and wiring guitars, cabs and the like.
I have built the chassis for the amp project out of aluminium and have it drilled for all controls and plugs, switches etc. I bought an unfinished amp project cheaply on my local auction which has given me most of the parts I need for this project.
I hav been studying the schematic for a few weeks now and there is few things that Im not quite sure of. http://sound.westhost.com/project27.htm
-On the pre-amp circuit it shows the 15volt power supply in bottom left corner. Does it connect to the right hand end at transistor BC549? I see there is a 15 volt +/- supply to both op amp 1 and from transistor BC549. I assume these are all connected by supply rails?
-With the +/- 35volt end of the above supply, does this connect to the +/- wires that come from the rectifier to the power amp board?
-On the pre-amp TL072 opamps does it only need connection 1,2,3,4,8 on OP amp1 and 5,6,7 on OP amp 2? Are the other terminals left unconnected?
-On the pic of the pre-amp board it shows 6 electrolytic caps but not on the schematic. What the story here?
Sorry to I am asking so many probably stupid questions but Im learning lots as I go.
Thanks in advance,
Derek

Yes thanks for that.
Now it makes sense that the rectifier and Caps boost the voltage. Im learning new stuff about circuits every day.

Thanks for that info JM.
I dont know why the Toroid manufacturers dont give the actual secondary voltage. I guess it fairly typical of Chinese manufactured stuff that the specs are absolutely basic and aren't listed anywhere. I recently bought a cheap tube output transformer at auction for an all tube amp project at some stage that is rated at 10 watts but the technical specs are unknown.
I will look into those schematics you suggest.

I have access to a well equipped high school workshop so the chassis is not a problem. I even have some aluminium sheet earmarked for one. I am nearly finished building a passive volume pedal which I folded out of Ali plate. Just need a couple of jacks and I can wire it and test.
What I need to know to kick start this amp project is two things.
I want to know what the actual voltage the Toroid secondary puts out as what Ive read that the 25 + 25 actually puts out 35 Volts. I assume this varies with the amperage loading?
From the bunch of schematics Ive looked at lots run at 15 volts, some 25, 35 and other higher. I want a basic probably 2 channel schematic that will use the suit the max output of the Toroid. The Elliot 100 watt design uses the same model Toroid design as I have but I see in another thread folks think the pre amp design is very basic and can be improved on.
I would like to build a 1oo watter if possible using something like a solid state Marshall schematic without any effects. Can anyone actually point me to a schematic that would suit the Toroid and end up with an amp that rocks.
Thanks in advance.

The plan is to reuse the components. I want to find a suitable schematic and re-fit the needed components using new Vero board so I can follow the schematic bit by bit. That way I can learn as I can go and gain an understanding of how all the bits fit together.
I can easily fold up a chassis being an Engineer by trade and plan to make it into a head unit as I have a 1x12" cab I built recently.
Some questions:
Is the power supply capable of 50 volts being 25+25 volts?
What wattage capability has the power supply and how do you match it with opamps etc.
Sorry Im not yet knowledgeable when it comes to the components and what they actually do but I am determined to learn.
 

Thanks for the reply. I have shifted the post with pic to the amp section.
Cheers.

Hi Folks,
I finally had time to take some pics of my US 5.00 amp parts.
I would like someone to tell me what exactly I have. I know it is two channel, (clean and dirty) and has a headphone socket and what looks like a line out. I cant get in touch with the guy who built it so haven't a schematic to work off. I does go but is very quiet as several wires have broken off from being transported etc.
What I would like is for someone to point me to a schematic I could use to build a basic 2 channel amp like a Marshall or similar using these parts.
The power supply is a 160VA MT2114 25 + 25 volt 3.2 amp  6.4 amp.
What wattage would this be capable of?
I can supply more detail of individual parts if needed but it has a BB OPA2134PA AND OPA37GP opamps.
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