This post it's a follow up of the August 8th 2019 one about the Ruby Amp.
As I already write in that post, the Ruby Amp it's a small instrument amplifier based on the LM386 IC. An in-depth analysis of this small amplifier in the electrosmash.com page here: https://www.electrosmash.com/ruby-amp-analysis. Basically this amplifier is composed by an N-Channel JFET input buffer that adjust the impedance of the instrument pickup. The speaker driving job it's done by the LM386.
Many mods can be found online for this amplifier.
Developing this mini PCB board, I've decide to collect for models/mods:
- Standard model: as found in http://www.runoffgroove.com/ruby.html page
- Bassman mod: makes the ruby sounds like an old Fender Bassman amp
- Hiwatt mod: gives this amplifier a nice British sound like an Hiwatt amp
- Distorsion mod: adds a distorsion switch
The board itself is really small 3.2x4.3cm.
The power plug, input jacks, switch, and potentiometers needs to be connected using extension wires.
That's because I want this board to be adaptive to any box, even small one. Like salvaged hardware PC speakers.
You can find below the EagleCAD (https://en.wikipedia.org/wiki/EAGLE_(program)) schematics and board, as long as exported image.
On the schematic you will find instruction for the main mods available.
D08 "Kenshiro" bass guitar amplifier is my latest amplifier. It's built on top of the reliable TDA2050 audio amplifier chip.
This project started, like many of mine, from a forgotten piece of consumer audio gear, this time, an old Trust PC subwoofer. A basic, cubic box made of MDF, plastic front panel, and a surprisingly decent speaker inside.
Once I pulled it apart and confirmed the speaker still worked, I gutted the electronics and got to work turning it into something special. The case was dull, so I gave it a complete makeover: decoupage artwork featuring Kenshiro himself. It felt only fitting to name the amp after him.
This amp runs on a single +30V power rail for the power stage and a separate +9V line for the preamp.
At the heart of the power stage is the tried-and-true TDA2050, delivering solid output for small gigs or home practice. It’s simple, tough, and very effective when paired with the speaker I'm using. The final stage it's based upon the Fender Rumble 15 schematic with some modifications.
The preamp section is based on the classic J. Tillman Discrete FET Guitar Preamp(http://www.till.com/articles/GuitarPreamp/), using a J201 JFET for that sweet, tube-like response. There's another J201 stage after the tone stack to recover some lost gain and push the signal forward with character.
Tone shaping is simple. I've included a Low and High control.
Then I've added a distortion switch that activates a pair of 1N914 diodes for symmetrical clipping. Combined with a gain-boosting cap, this adds a touch of grit and aggression to the sound. Not too much, just enough to growl without getting muddy.
The control panel is mounted on the back, I kept things simple: just a wooden panel with cutouts for the power input and a handle.
The sound is tight and responsive. The distortion is very usable, great for vintage vibes or even light fuzz. Volume is not very high, but this is a practice or studio amplifier, not a live one. It won’t fill a stadium, but for home practice or small rehearsals, Kenshiro delivers more than enough fury.
MIDI adapters are essential tools for musicians and audio enthusiasts. They act as bridges between MIDI devices, allowing seamless communication.
In this project, I’ll share the schematic of the adapter design along with a custom PCB I’ve developed. The goal is to create a compact, functional MIDI adapter suitable for studio and live environments.
It features:
MIDI In: For receiving signals from external devices.
MIDI Out: For sending processed MIDI signals.
MIDI Through: To pass MIDI signals directly to other devices, with an optional splitting mechanism for multiple outputs.
MIDI though can be cut away if you want.
It can be drawn at 3.3V or 5V and it will helps you connecting your microcontroller to a MIDI device.
I found a Record Player by Philips, model EL3514 in the dumpster.
Many parts are missing, but I decide to take this home.
I disassemble it, to my surprise both the tubes are untouched.
This player has a speaker, which is ok too. And three tubes (ECC83, EL95, DM71).
WARNING! - The project described in these pages utilizes POTENTIALLY FATAL HIGH VOLTAGES. Do not attempt to build circuits presented on this site if you do not have the required experience and skills to work with such voltages. I assume no responsibility whatsoever for any damage caused by the usage of my circuits.
The DM71 is an interesting tuning indicator tube that can be also use as power output indicator. I'll keep this valve for a future project.
The player also has one PNP germanium transistor, the AC107. I've tested it, seems ok. I'll keep it for some other project.
I don´t have a full tube guitar amplifier, so let's focus my attention on the main components of a small tube guitar amplifier, which are the main transformer, the output transformer, the preamplifier and the output tube.
First thing I've checked was the main transformer. It seems to work. It has high voltage output and low voltage output for tube heater. I just have to rewire it. I decide to keep the original voltage output selector. I will always use it with the 220V setting, but one can change the selector to make it works even at 100V.
Output transformer also seems to be working. At least it was now shorted.
Then I attached the tube heater and check. To my surprise the heating elements works.
I haven't got a tube tester. So I have to build a breadboard circuit to test tubes. Turns out that both tubes works.
The ECC83 it's branded Philips. This tube is also known as 12AX7 and it can be used as pre-amplifier. Indeed many guitar amplifier use this tube in the preamplifier stage.
As preamplifier reference I decide to use the Fender Champ 5F1 schematic.
The tone stack is indeed referenced from a Fender Blackface.
I can not found any guitar amplifier that use the EL95, which is a power output tube, also brand Philips, but there are a lot of old gear, as radios, that use this tube.
The EL95 can output up to 3W with 250V at plate.
For the output I take as reference the Philips EL3514 schematic.
Thanks to the https://www.radiomuseum.org website one can find a lot of schematic and information about old gears.
Let's put it all together in a case. I've use the original Philips case, cut some piece of new aluminum sheet from a PC case, makes some holes, painted black, and the tube amplifier main case is ready to use.
As guitar amplifier case I use a wine bottle wooden box. It all fits. I can even reuse the EL3514 handle and feet.
Wood is painted light walnut and finished with beeswax. There's a read hole to look at the tubes, the front panel is from the original R-Player.
The D06 is a Bass Guitar Amplifier built on top of the solid state TDA2030 IC.
The project starts from a salvaged JBL subwoofer. The enclose was in wood, front and back cover in plastic. the woofer cone was inside. I decide to check if it works... and it of course works. The speaker was a good 8ohm 8inch subwoofer.
I can't leave the speaker inside the case, so I decide to cut the case in the middle, where the wood that holds the speaker is glued. Now that the case is cut, the speaker can see the sun. The case was wrapped with plastic, that I have to remove cause it was ruined even before I cut the case.
Once removed I had to cut an hole on the front plate, just over the speaker. There I will install the amplifier controls.
Hole done, now it's time for the plastic holder for the controls, but that was simple. The back of the amplifier too it's as simple as a piece of wood with some hole for the supply plug and the handle.
One problem I have to figure out was the speaker hole, it was done in such a way that the speaker has to be mounted from the outside of the case, but I don't want to see screw, so I've 3D printed an adaptor, that will also be the holder for the mosquito net I'm using to protect the speaker.
Last but not least is the case finish, I've used a texture glued with vinyl glue.
Inside the speaker I've build a new electronic.
The amplifier main supply it's a 230V to +-14V AC. Rectified to +-18V and 9V. I'm using the dual rail supply for the amplifier IC and the single rail 9v supply for the preamplifier.
The three tone stack can equalize Low, Middle, High frequencies and it's based on a design found in Peavy amplifiers from 80's. After the tone stack a new preamplifier stage is needed in order to mitigate the loss of the previous stage.
I've added here a simple distortion stage, enabled with a switch. It's simply a capacitor that increase the gain of this second stage and a couple of diodes to clip the signal.
The power amplifier it's base on the TDA2030 IC in a simple dual rail configuration.
One interesting thing I've added it's an optical compressor. It's based on the VTL5C7 optoisolator driven by the output of the preamplifier stage. The optoisolator drive a voltage divider that is used to reduce the output signal of the amplifier.
Now here we came to the sound. It's pretty good, tone stack also sounds good. Volume is not so high of course, we are speaking of a 14W amplifier but it sounds good to my ear.
Hope you find this project interesting. You can find all the schematics and information below.
A friend give to me it's 5.1 speaker system subwoofer.
The brand it's Kevler. It has an integrated amplifier for a 5.1 speaker. The problem is that the amplifier does not work. I've checked a few things around but I did not find anything sensational. Also I don't have a subwoofer around to use.
So I decide to repurpose this as a single subwoofer system.
The speaker is rated 120watt, 6ohm.
I've buy a TPA3116D2 cheap board, it maybe does not even have a genuine chip, but for my purpose I will not investigate, I'm happy with that. I'm going to use a 24V supply. I've around one of 3A.
From figure 22 and 26 of TPA3116 datasheet I can only find Maximum Power Output in PBTL for Rl of 2ohm and 3ohm. My speaker is 6ohm.
So to estimate the consumption I've supposed a 50W max output, and a 85% efficiency. My estimation formula is Power/Efficiency/Vsupply, so 50/0.85/24 = 2.5A almost. My 3A supply should fit it.
D05 is a vintage hybrid guitar amplifier. The preamplifier stage is driven by a vacuum tube, the power stage by the a class AB solid state IC.
It's built on top of an old portable turntable found in the dumpster. This time I've found just a few parts of the turntable. In particular the low part of the wood case, and the electronics.
Unfortunately I've not taken pictures of the system when I've found this, you have to believe if I say it was in horrible conditions. The full turntable mechanism is missing. The amplifier tube is broken, but I've notice the preamp tube was not.
WARNING! - The project described in these pages utilizes POTENTIALLY FATAL HIGH VOLTAGES. Do not attempt to build circuits presented on this site if you do not have the required experience and skills to work with such voltages. I assume no responsibility whatsoever for any damage caused by the usage of my circuits.
I've search for the datasheet of this tube, the 6AT6 (https://www.radiomuseum.org/tubes/tube_6at6.html), it turn out it has enough gain to be used as a guitar pre amplifier. Indeed it is used in the Fender "Harvard" 5F10, that's a vacuum tube amplifier made by fender from 1955 to 1963, you can find more info about his amplifier here: https://en.wikipedia.org/wiki/Fender_Harvard.
The preamplifier tube I'm using is manufactured from the Italian company Europhon.
For this design I've decide to keep things clean, I do not want this amplifier to be equipped with an overdrive circuit, all the distorted sounds should came out from the tube saturation.
After the first preamplifier stage there's the single tone controller, which is derived indeed from the Big Muff tone stage. I like the way this tone stage boost high and bass sounds, also it drops the signal just a little.
Here it comes the heart of this amplifier, the 6AT6 valve preamp stage. Even it is used by the Fender 5G10, I've not just copy and paste this circuit here, I have to bias the valve for the voltage provided by the power stage I've built. This stage has to be clean enough even with full volume coming from the input.
The last stage is based on the TDA2003 solid state class AB amp. This is driven in single rail supply, +12V, in a pretty common configuration, bang on the datasheet application circuit.
Up to here the amplifier sound clean, but I would like to add a bit of saturation if needed. For this reason I've added a booster stage between the tone and the valve pre amplifier. The booster is based on the LBP-1 booster, with just a few values changes.
After the tube preamp there must be voltage divider that arrange the signal for the amplifier, if the signal is too high the poor TDA2003 will clip, and I just want the distorted sound comes from the preamplifier, not the amplifier.
I've finally add a 4ohm 6" speaker I've around, not that big cause the cause is pretty small, for this reason there's also a mono jack speaker output that disable the internal speaker output, this way one can use an external cabinet.
The power stage for this amplifier use a trick to drive the valve with the correct voltage. As you know tubes are driven with high voltage power, indeed other IC use low voltage. I've use a standard 230V to 12V with primary and secondary connected in reverse to pull the voltage up to +170V, used by the valve preamp. Keep in mind that using a transformed in this configuration induct some loos on signal, usually 20%, after all we are using a transformer in a way it was not built for.
Power stage also provide +6.3V for the valve filament, this is done by using a 7805 with the ground biased using two 1N4148 transistors. +12V is provided for the TDA2003 stage and finally +9V for the solid state preamp stage.
As you may notice, there's almost more of power stage than preamplifier and amplifier stage.
All the electronic have been mounted on the original iron holder of the turntable amplifier. I've just added a few new holes for the new board. It has been spray painted black.
Final stage was to build a decent case using the original one. I've cut from the original case the bottom part, the one that holds the turntable mechanism. On top of the case I've pierce the wood to make the space for the controls, Jack input, Volume, Tone control, Gain control, Saturation engage switch, On/Off button. I've pasted and prepared the wood. Then I've used vinyl glue to cover with fabric the top of the wood, like it's done on vintage amplifiers.
The front mask is the one from the original turntable. The hole which contains the voltage selector has been replaced with acrylic glass, behind the tube can be seen. The tube is secured using also a 3D printed holder.
A 230V light bulb it's used for the on/off detection.
At my ears: it sounds good, especially if used with an external case. I've used with a couple of pedals I've built, I must admit it makes the pedals sound really good.
At my eyes: it's a joy! Each time I see this amplifier I'm happy for having built it.
This time I've find a vintage Pioneer XL-L77 hi-fi in the dumpster.
Amplifier display is not working, and also the amplifier has a big bump on enclosure. So I decide to keep just the subwoofer and speaker.
The front speaker are not that good, they comes in a small plastic enclosure, and the speaker are 8W small speaker.
The Subwoofer looks pretty good, but it has speaker with damaged ring.
I decide to restore the Subwoofer and make it a 2.1 system our of it.
So, I've replaced both the rings with a couple a new foam based. To do this job I've clean the speaker and then glue the replacement with all purpose clear solvent based glue.
Another think I've done to the enclosure is to remove the adhesive grey paper. I prefer to have it painted like wood.
Then I've to do some woodwork to make the amplifier board fit on it, and to drill out holes and space for the amplifier interface.
The amplifier has line/in, bluetooth, mains voltage in, a volume, a bass level selector, and the output for the left and right speaker.
As amplifier board I've used a Creative Inspire T3030 board I've around. This board has a unusual connector. I don't have the board command interface for this, so I've to find the pinout and the way to add level and volume.
This amplifier it's a 90's stackable hifi vintage. It's a 50W+50W on 8ohm output. In class AB.
The problem with this amplifier is that it comes alone without the preamplifier and the other stack elements, and it comes with a custom plug.
So, in order to make this device work I've to find the schematic online and check which is the correct wiring to makes this amplifier goes out from stand-by.
After having found this trick I've tested it with an aux cable. It works good, not the best thing I've heard but clean.
So I decide to add a toggle switch on the input to select between an RCA stereo input plug that I've added and a bluetooth input.
To power the bluetooth board I've take the 15V voltage output from the board into a stepdown converter, to build 5V out of it. Then to decouple the signal I've added a small 1W DC to DC converter. This last one component is really important if you want to keep your bluetooth audio out clean.
I've also added a volume control by using a simple stereo potentiometer.
A tube amplifier output transformer is a crucial component in vacuum tube-based audio amplifiers. It's responsible for matching the high impedance of the vacuum tubes to the low impedance of the speaker, as well as transferring the audio signal from the tubes to the speaker while maintaining fidelity.
WARNING! - The project described in these pages utilizes POTENTIALLY FATAL HIGH VOLTAGES. Do not attempt to build circuits presented on this site if you do not have the required experience and skills to work with such voltages. I assume no responsibility whatsoever for any damage caused by the usage of my circuits.
Imagine you have salvaged one from an old amplifier but you don't know which is the primary side, which is the secondary, and what's the impedance of that transformer.
Finding the primary and secondary side is the first step. You just have to measure resistance between the two wires of each side. In this type of transformer primary side winding has a greater resistance then secondary side.
Once you know which is the primary side you have to measure the impedance of the transformer, this is quite important cause you have to match the impedance of the power tube.
I you take as example a 6V6 tube and take a look at the datasheet, for a push-pull class AB amplifier when the plate voltage is 285 the effective load resistance (plate to plate) has to be 8000ohm. So our aim will be matching that impedance.
We know that the ratio between primary and secondary impedance is equal to the square of the ratio between the turns on each side. So we have to find the turn ratio.
Zp/Zs = (Np/Ns)^2
To find the turn ratio the way I use it to load the primary side with an AC voltage, I use pretty high voltage cause the ratio will lower the voltage down on the secondary side, using an higher voltage makes reading with a standard multimeter more accurate.
So to find the turn ration you just have to measure voltage on the primary side and then voltage on the secondary side, this ratio is equal to the turns ratio.
I prefer to measure the secondary side voltage under load. For my approximation it's enough a resistor even if it's preferable something that is not a "pure" pure resistance load, so a speaker as example. Then I made the mean between the voltage on the secondary loaded and not loaded. So summarizing the procedure
Apply an AC voltage on the primary side. Use an high voltage source, like your main amplifier transformer output. Also to be sure not to break anything, put a fuse on the output of your main transformer. I use a 300V AC with 200mA fuse.
Measure the voltage on the primary side. Note that it will not be the same voltage of your main transformer output, cause this voltage will drop due to the resistance between the turns. Let's call this value Vp.
Measure the voltage on the secondary side without any load. Let's call this value Vs.
Measure the voltage on the secondary side with a load with impedance Zs. Let's call this value Vsl.
Compute the turns ratio. Let's call this value K. K=Vp/((Vs+Vsl)/2)
Now you can find your Zp impedance with the secondary side is on the load of Zs. Zp=Zs*K^2
This way you can match your output transformer with your tube specs.
This is the mono cubic speaker I've built mainly for mixing audio.
It's been a few month that I want to add a mono speaker to my mixing station. Switching to mono for the mixing process is something well know and used for years, in the last years the Avantone MixCubes became popular for this reason.
I want something similar, so I decide to built it. I've one Tannoy CMS401e speaker not used. That is a ceiling monitor system is suited to high-level music and speech reinforcement applications.
This speaker has a transformer taps, which is used for distribution system. In my case I disabled the transfomer, cause I've just connected the speker directly to the amplifier board.
I've used a TPA3118 amplifier board. Supplied by a 12V 3A swithing power. The stereo input jack simply connect the tip and the ring with a 1k resistor, this will mix the right and left signal to the mono input of the amplifier. Before the amplifier input there's just a simple 50k potentiometer used for the volume.
I've build the case using an old speaker case. I've cut it to a cube and glue. Then I paint using dark wood varnish.
The Tannoy speaker can also rotate a little bit, so that the direction can be adjusted. This is a plus for me, I can point it strait to my face.
The finish product looks pretty good. And the sound it's of course not as good as a stereo system, but that's exactly how I want it to perform.
San Pellegrino Terme is a thermal location, so I had a vacation there. I bought a tin of candies which I'm using as the case for this guitar/bass pedal.
This is why it's called the San Pellegrino Terme Distortion.
A few weeks later from this vacation I've found a 70's radio in the dumpster. That radio has a couple of germanium transistor on board.
I've desoldered them and I've decided to use as soon as possible, cause they are not branded and I do not want to keep htem in my germanium transistor drawer.
They are PNP germanium transistor measuring 180 hFE. Gain is a little low but that would not be a big issue. I take as reference a classic 2 transistor distortion configuration.
Indeed I've decoupled the output from the first transistor and input that output to the second transistor, forming a two stage gain.
I've try to push the gain to the limit.
No controls available, just the output volume.
True bypass, and a active led output.
This pedal is not going to start a revolution, it's just a simple distortion build from unknown components in a tin of candies, but I like it.
A friend of mine give me his non-functional tap tempo delay guitar pedal.
The problem with this pedal was that one can hear an annoying clicking sound while playing. Also after trying it for a while it stops working.
The pedal is called La Macchina del Tempo by Fattoria Mendoza, a custom pedal builder here in italy.
Advice: I've never have any pedal from this company. I think the pedal I have has been handled by someone outside the company, or they have build this as a demo pedal, indeed I can not find this pedal on theire actual website. I advice you this cause what I've found in this pedal is not that beauty.
First time I've opened the pedal I've seen a little bit of a mess, wires has not been secured on the case.
I've played this pedal for an hour or so with the back case open. And after a while the pedal stop working, the output led does not blink.
The pedal itself has a couple of boards, the main one is a 1 side PCB with a scratched number, I've searched for it and I've found it's a kit uk-electronic named Kit Digital Delay PT-80 with tap tempo (http://uk-electronic.de/onlineshop/product_info.php?products_id=2326&language=en). The other two are prototype boards that just has some capacitors and a output volume control.
First thing I've checked is the switching regulator, the LTC1044. And that's the guilty. No voltage output from this IC. So I try injecting voltage after it and the pedal start working again. So I've replaced it.
While waiting for the IC to be delivered I've clean up a little bit the PCB. I've soldered a couple of components that where just punched in used pin head. And resolder a couple of wires.
When the IC has been delivered I've checked the pedal, and here I can found the first problem my friend told me about, that it the annoying clicking noise.
I've notice this noise has exactly the same frequency of the tap tempo led. So I've remove the led and I've notice it was the led the root of the problem. Adding a capacitor on the supply line does not solve the issue. So I've added a RC low pass filter on the led line. This will slow down the led light up but has solved the issue.
Now the pedal has been cleaned up and can be used again.
Terratec Phase 88 Rack is mid 2000 8 channel in/out audio interface. It has 8 balanced/unbalanced input, 2 of them phantom powered, and 8 balanced/unbalanced output. It can reacord at 96 kHz.
Like the ST Audio, the Terratec also it's based on a Rack + PCI interface design. And you guess... the PCI is running the IC Ensemble Envy24 I/O controller chip too, nominally the ICE1712.
It happens to find a good deal for a couple of Terratec. To me it means to have 16 channels of recording power instead of 8. I don't really use that card to much, just to record drums, but that deal was so good I couldn't let it go.
Terratec Phase 88 Rack PCI Full specifications:
8 balanced analog inputs, 1/4" jack
8 balanced analog outputs, 1/4" jack
8 gain controllers on the front for setting levels for analog inputs (20dB range)
8 input signal and clipping LEDs on the front panel
2 XLR/jack microphone inputs on the front panel as alternatives to the Line inputs 7 and 8, inputs 7 and 8 switchable between microphone and line/instrument levels, switchable 48 V phantom power for microphone inputs
2 separate MIDI interfaces (5-pin DIN)
24-bit/96 kHz A/D converter with 100 dB (A) SNR*, 100 dB(A) typical @ 48 kHz
24-bit/96 kHz D/A converter with 110 dB (A) SNR*, 109 dB(A) typical @ 48 kHz
WordClock I/O
But the deal has a price... the supply is missing, and one of the card has channels 7 and 8 that does not work. Also, driver for Windows are a question mark, I can not find a sure answer if they work or not, but for me that was not a problem cause my first plane was to use linux as a recordind station.
The package has been delivered, I've opened it and connect both the PCI and the related rack to a Core 2 Quad 2 Q6600 with 8Gb of RAM, and 500Gb SSD I would like to use for this project. It's not the best PC for mixing but I will use it just for recording. It will suffice.
The rack needs a 12V AC 1.5A AC supply, I've one 3.5A the just fits both the rack.
To my surprise, the latest 5.51b driver from Terratec works on Windows 10 x64. I've configured one card as master, and the other as secondary, calibrate them throgh the driver mixer software, I've reboot... and they works. I can see cards input and output in Reaper using the ASIO driver from Terratec.
Now it's time to repair the channel 7 and 8 of one rack.
That channels emit just a white noise, no matter if I try the line input or the mic input.
I have to open the card and trace out the problem.
Of course there is not schematic for this card, so I have to trace the signal using the continuity functionality of my multimeter.
Signal goes straight from the inputs (line and mic) to a relay, that is driven by software, then to the LM833 op-amp. This is the first stage driver for the input.
I take my multimeter out, feed a 100mV 500Hz sine in the line input and find out that for both the channels out from the first stage of the LM833 there's a DC signal that has nothing in common with the expected sine.
So I've ordered a few LM833 and replaced the two of channels 7 and 8.
Channels now works!
For a few bucks now I've got a 16 channel recording station. As for my DSP 2000 ST-Audio station I will use it just for recording, this time I'm on Windows but even if the PC is not that powerfull it works fast if used just for this end.
I've also try the Terratec on Linux, but the Envy24 driver are not compatible with this specific hardware, I think one has to download the driver code, fix it and recompile the kernel, but to me just using Windows is enough.
