G'day all.
I am thinking of trying out  some of the high power "D" amp modules that are everywhere.
Silicon Chip magazine had a story on some modules they tried out, a 1000 watt amp and 1000 watt power supply that they called a 500 watt amp put together.
I might try this out with a Bass preamp I am making.

The problem is that the power supply has only got +- 70v rails, and a single +15v output also.
I guess the easy option would be to convert the +15v to -15v with a LT1054 or similar but it would be a bit less then -15v at the output.

Since I would be dropping from 70 volts to 15 volts at an unknown current I don't really want to use a dropping resistor, not even going into a 7815 regulator.

The 7815 and 7915 can go up to 35 volts max so they are out.

This would be a common problem with any design requiring more then +-35 volts going to the power amplifier PCB, most pre-amps will want a nice +-15 volt supply.

Does anyone have a good solution ?
Maybe a Zener diode with a low loss mosfet or transistor to do the dropping ?
I would love to hear what methods others have used in the past.
Thanks
Michael

G'day guys and gals
I have been wanting to make a Lab Series Pedal for a while, recently I was talking to a young dude who plays Bass in "June And The Desert Flames".
While I was talking to him I realized he does not have a lot of gear and I can easily build some Pre-Amp pedals and some effect pedals for him fairly easy.
I have some PCB's for Sunn Beta pedals, Chunk System Brown Dog/ Agent 00Funk, etc at home.
I also thought it might be a good time to get into a Lab Systems PCB, the L4 Bass is simpler then the L5-L11 pedals so its a good starting point for me.

I have tried to change the CA3094 and CA3080 IC's to one LM13700 IC, but I am not that good on theory, I gave up working as an electrician 15 years ago because of all the narcotic pain killers I have to take every day.

Could some of the really great people who post here check my changes please and see if it is feasible to replace the 2 IC's with one LM13700 please.

I have read through lots of posts on this type of modification on the net and did the best I can, my brain is too forgetful to try working it out or trying to simulate it.
If someone knows how much the +- 15V rails use would also be great, I would love to power it from a LT1054 or similar on 9V supply.

Thank,
Michael

I started to looking into building a 12 watt Marshall by mixing all the 12watt Preamp circuits I found, and also mixing the 12 watt and a 30 watt amp circuit in Marshall amps so I could make any one of the 12 watt amps with 12 to 30 watts output on the same PCB. You just had to pick the right components to make the version you wanted.
Some 12 watt amps had a Bias pot and some did not. Mk1 preamp has diode clipping and the later ones dont, etc.

I got derailed when my dad got sick, traveled from Tassie to northern NSW (Australia) and spent 4 weeks with him. Had to go back to Tassie for medical reasons and be with my family for a week, then back as dad passed away as soon as I left, stayed 5 weeks then back home for Doctor visit and now I am going back up to pack what I want to keep and sell the rest, sell houses, cars,  etc.
I am going to sort all my stuff nice and neat when I get a chance because its hell trying to go through your parents stuff when they are both gone and everything is all over the place.

Anyway, this is as far as I got on a 12 watt amp before the wheels fell off.
I was going to post the KiCad files  of the PCB when I finished and still might when or if I get back to it. I put a jumper on the board if reverb is not wanted, and a place for effects to be inserted which can be bridged if not wanted.
I made the PCB so TO3 transistors had to be wired in or TO247 can be used on PCB.

G'day all
So my father died a week ago,and my brother 3 years ago and mum 5 years ago.
Going through all the stuff in my fathers house I have found lots of Electrolytic caps,
Some are around 6800uF 65V, 2200uF 80V, etc. I know these used to be my brothers but he moved overseas about 20 years ago.
Will they still be ok to use in new amp builds or should I scrap them, they have never been used.
There are also bags full of 1uF, 10uf, 22uF etc, never used and heaps of WIMA box caps.
I have to ship them over 2000km back to my place so I only want to keep good *s!!t*.

I was given a pair of small practice amps last week, one was a Samick SM-10.
I searched the Net for a schematic and some information,-----Nothing----.

I wanted to know what I had before I started re-assembling it, it was pulled apart.
This was the hardest circuit I have ever traced, and strangest for a budget amp.
I have traced it as well as I can for now, but I think I will do it again in the future just to see if I can find any faults in my tracing.

It has a strange setup with the Volume pot and Overdrive Pot.
I have no clue yet what the Overdrive Socket does, when I get it working I will try shorting it out to see if it kills the Overdrive I think.
Serial Number is 94060140, 1994 model ?

Here is the schematic I have traced at this moment:


 

I came across this when I was doing something on the net, I think it is cool enough to post it here for everyone to check out.
I especially like how he generates the high voltage for his designs, could be useful for tube pedals.
I think the design can easily be adapted for a stomp-box pre-amp, 
The portable bluetooth tube amp uses a 12AX7 and a 12AU7 tube, the JCM800 uses 2 tubes in the pre-amp.
I wonder if a JCM 800 pre-amp into a LM386 would sound ok ?
Anyway, I found it interesting, and thought provoking. I just wish I was good at using Spice programs so I could play with the idea more.
I think it would be too hard for me to get into Spice, my Dr keeps pumping me full of opioids for pain, messes with the head too much.

https://www.instructables.com/High-Gain-Subminiature-Amplifier/
https://www.instructables.com/Battery-Powered-Tube-Amplifier/
https://www.instructables.com/How-to-Build-a-Portable-Bluetooth-Tube-Amplifier/

G'day
I love making up pedals, amps etc for my daughter and myself.
My problem is that I can barely play guitar, and no way would I like to hear what I play.
When I make up an Amp, like I am doing now, I would like some way of testing the sound,
I would love it if someone who can play an electric or bass (or both) could record some dry tones and leave a recording that anyone can use.
If I came up with the best pedal ever, and then plucked or strummed my cheap guitar it would sound like a dogs dinner and no-one would like the sound sample.
Lets call it:  Sample1-Chord set,   Sample 2- Plucking etc. Or Sample 1- Stairway intro....
If we could all send the same signal into our gear and then post samples we might get a better understanding of what someone else has made.
This makes sense to me, but I know bugger all about it really.
Soo... Could someone who has the recording gear please make some test tracks up for me with a clean dry signal please.

Also while I am asking about this, what would be the best way to inject the signal, I can use a computer signal out, DVD player signal out, Phone (Windows .
How much should I drop the signal from say a computer sound card to mimic a guitar out. 5 meg resistor with a 1 meg pot ? A small op-amp circuit for high Z ?
All comments good and bad will be greatly appreciated, thank you
Michael

G'day everyone
I think I just bought myself a Gorilla TC110 Amp on auction.
I don't know why I did it, it just happened.
I paid $35Au ($25 US) for it so I think I can't really loose anything.
I believe these amps sound crap from what little I could find out on the net.
Does anyone have any circuits or information on Gorilla Amps ?
I read that Pignose made them.
I will have to go and pick it up next week when I go to the city (Hobart Tas)
If I'm lucky at least I scored a reverb tank, 6 knobs. a decent transformer, etc.
I might stuff a 1 channel Sunn Beta pre-amp into the box, just to confuse people.
Or maybe a Marshall Lead 12W reverb, with a nice celestion 12" speaker.
A Schematic would be nice if someone has one.

I am wondering why Guitar Amps never have a 9V output on the back for  pedals ?
It would be really easy to include on a new build, and not very expensive.
How easy to run a few pedals with a 9V output already there.
Is there a reason I have never seen it done?
For $10 you could have 4 x 9V 1.5A outlets on the back of an Amp.
Most existing amps can probably have one added with the current transformer.
I would love to know what others think of this.
Is there a valid reason not to do it ?
Michael.

G'day
I found a circuit an a Russian web page and decided to make myself a PCB using KiCad so I can practice some SMD soldering.
I am calling the PCB "Micks Thick As A Brick", I have no clue if the circuit will work, but I had fun making it up.
I have ordered 5 PCB's from JLCPCB and will make one up some time in the future.If it works I will post that here.
The PCB can be cut in half and rejoined back to back so it might fit in a 1590A box (maybe).
Not all components are used, if the transistors are used then the R5,R10, R20 resistors are not used.
If the top half of the PCB is only used, then don't use the transistors or R43, R44, R45, R46, R47 and C36.
The SMD PT2399 should be the ones available from Tayda.
Just study the circuit and work it out.

G'day
I made up a PCB for the Marshall Mosfet 3310, 5213, 5215 amplifier, I used KiCad to make it but I have no idea if the transistors I substituted will work right.
The Mosfets in the circuit might not be available any more neither, but you can just run wires to whatever you want to use after they are mounted on a heatsink
The original Mosfets were TO-3 type connected with wires running back to the PCB.
I have no idea what the choke or inductor value should be, or the resistor it is wound around, I asked the Marshall tech support and they had no clue either.
The footprint for the choke and the resistor  it is wound around are on top of each other.
Will it work ?  I guess I will find out when I build one, I have 5 PCB's on the way from JLCPCB
I am a complete beginner when it comes to making up PCB's so anything can happen. I have built amps and stuff a long time ago,and then I became a sparky for 40 years.
Anyhow, here are some  pics and files.
Cheers....Mick

G'day
I made this PCB up for myself using KiCad so I can make up some Marshall SS amps, and the Marshall Artist SS pre and valve main amp.
This is not tested and but I have ordered 5 PCB's for myself and they are on the way.( Use at your own risk )
I used the footprints for the Tayda A-5079 PCB mount Jack Sockets and Alpha (Taiwan) pots.
The 2.2uF Electrolytic caps footprint will also fit MKS caps 7.2mm x 7.2mm 5mm Pitch, thats why they look strange on the pics.
IGNORE VALUES IN SCHEMATIC......use the ones in the component list, the schematic is mixed up with values from the various versions.
The 5213 Mosfet also has a clean channel and this is on the PCB as well, only first 3 pots and 2 inputs are on the PCB and the rest of the pots are wired up from plugs on the PCB.
I made up the spacing between pots and sockets etc. myself and it does not correspond to an actual Marshall amp (I think)
I made it to fit into a rack-mount case or whatever I can get cheap.
If I have any problems when I build one I will leave a message, anyone can use the files anyway they want.
I leave the Gerber files I sent to JLCPCB to order my PCB's.
Also the Kicad files if you can open them (might need my modified footprints ? I don't know how to save them yet.)
Cheers.....Mick

After thinking about it for a long while, I finally decided to create a Sun Beta PCB for myself and order some.
I was trying to work out the correct dimensions between the pots but it was really hard, until Fishheadjoe posted some pics for me of his head on the TalkBass forum.
The spacing is most likely not spot on but it is as close as I can get unless I have a original PCB to work from.
I made the PCB up in Kicad, and I added some of my own mods because I like them.
All the 2.2uF NP Electro capacitors ( originally 2uF ) can be used or there is space for WIMA MKS type at 5mm pitch and up to 7.2mm x 7.2mm body in the same place.
I made it for both Bass and Lead, just remove the pots you don't need, Lead - remove the Bass Level pots and Bass Master pot, Bass  - remove the reverb pots and Lead Level and Master.
I bet some who look at the pics will think it has some funny spider pot on there instead of either a Lead Reverb or Bass Level in the same place.
I also added a different power supply plug where the power goes through a 7815 and 7915 regulator in case it is needed to make +-15V
Just delete C1 D1 U1 C2 D2 U2 and the 18-35V supply plug if you already have a +-15V supply handy.
I also made a different footprint for the supply caps C156, C157, C1, C2,  originally C156 and C157 was 10uF 25V, the footprint will fit caps up to 10mm with 2.5mm or 5mm pitch so you can go for a higher value if you want.
The foot Switch circuit is one I got from DiscoVlad on the FSB forum, he used it and said it works fine. Original chips used by Sunn are too hard to find.
This PCB is not tested to see if it works so use at your own risk
I have ordered 5 PCB's from JLCPCB and am waiting for them to arrive, I will post if I have any trouble with them, Its my Xmas present for myself.
I am going to stick it in a 2U or 3U ( front send / return jacks ) rack mount case for myself and my daughter, Lead for me and Lead and Bass for my daughter.
I made all the connectors Molex KK396 type as Tayda carries them and I get most of my components from them when its for me or my daughter, I might just solder wires straight to the PCB though instead of using connectors.

G'day
I am drawing up the Sunn SL260 into KiCad so I can make the preamp PCB for myself.
I have hit a roadblock as I cant work out the orientation of the Pots in the tone section
can someone please check and advice me how they should be mounted, ie, pin 1 on pots.
That's the Bass, Mid, Mid frequency, Treble pots.
I have also made some mods to the original circuit, power supply and foot switch circuit for reverb, do they look ok ?
Thank you for any help.
Michael