Saturday, 29 November 2014

Rezzonics version of the Shin-Ei Fuzz-Wah - Sound check (4/4)

The reference signal is just a sequence of chords recorded into the computer with the pedal in bypass mode. This is the bypassed clean signal: This is the same sequence of chords with Fuzz at maximum gain, tone cut off and Wah off: It's a rough tone with lots of high harmonics due to the octaver fuzz without tone filtering. Now the chord sequence with Fuzz maximum gain but this time the tone cut filter is on. Wah is off. High harmonics are somewhat reduced while mid tones are reinforced by the tone cut filter. Chord sequence with Fuzz at maximum gain, tone cut is off, Wah is on: This time a guitar riff is used instead of a sequence of chords, Fuzz is set at maximum gain, Wah is of, tone cut filter is set consecutively off and on: Guitar riff with fuzz at maximum gain, Wah is on, tone cut filter is set alternatively on and then off: This is the playlist with all the different sounds used in the sound check for comparison: I thought that the best way to check the sound of the Super Fuzz-Wah pedal was on a real song, so this is the cover of Jesus & Mary Chain's song Just Like Honey, from their album Psychocandy. The Fuzz-Wah pedal was connected as input to the TubeSim amp and Rezzonics 1x12 cabinet speaker:

Rezzonics version of the Shin-Ei Fuzz-Wah - Pedal assembly (3/4)

The Fuzz-Wah was mounted on a 1590B Hammond enclosure, with two NKK M2012SS1W01 SPDT ON-ON switches, two Alpha RV16AF-10-20R1-A100K 16 mm A100K potentiometers, one Alpha RV16AF-10-20R1-A50K 16 mm A50K potentiometer, one Neutrik NMJ6HCD2 1/4'' Stereo phone jack as input connector, one Neutrik NMJ4HCD2 1/4'' Mono phone jack as output connector, one Alpha SF17020F-0302-21R-L 3PDT foot pushbutton switch, one Switchcraft 722A 2 mm DC power jack, one 5 mm blue LED, one 5mm LED bezel chrome, one 9V battery snap, and three black flute knobs with line indicator.

I buy most of the electronics at Mouser website, but some of the accessories are difficult to find, so there is an excellent German website specialized in pedals kits, components and accessories called Musikding.

It's quite hard to pack PCB, pots, jacks, battery and switches on a 1590B enclosure, so in order to design, plan and place all the different components I create a three view drawing with all the components on Inkscape. Inkscape allows copying an image from a pdf datasheet  convert it into a vectorial drawing,with the powerful Trace Bitmap tool, edit and delete lines or points, scale it and group all the lines into a single component that then can be moved and properly placed. This allows getting a better idea on how everything is going to fit in and avoid having troubles and discovering too late that a component does not properly fit. See the picture below. This is extremely useful, specially in this case, where it's extremely challenging to place three knobs and pots, two toggle switches and one foot push button switch on the faceplate. We have to be sure that everything fits in a there is enough place to add the faceplate design:
Fig 1. Inkscape three view pedal mechanical drawing
I also use Inkscape to design the faceplate. I create numbered knob dials, symbols, shapes, texts and drills as a group of lines that I can later reuse. In this case I used Aeroplane Flies High font for the Rezzonics and Rezz Fuzz v2 labels:

I did a simple design in blue and printed it on a transparent sheet. I decided rather not paint the enclosure but sand and polish the aluminum to leave it's natural metallic color and glue the transparent sheet with the faceplate design in blue. In order to better protect the laser printer blue ink, I printed the design in reverse, Inkscape allows easily reversing or flipping the design.

Water sanding to finer grains and polishing is quite a tedious work but the final chrome-like result is quite nice. Afterwards, holes are made using a multi-drill bit, I recommend using this type of drill for better results.

I used a repositionable adhesive spray to glue the transparent sheet. Faceplate shape is cut and adjusted to the enclosure after water sanding and polishing. Adhesive is applied to the transparent sheet and leave for 2 minutes to let evaporate and reduce the number of bubbles, then is firmly applied using a clean cloth with outwards movements, avoiding formation of bubbles and taking care that the faceplace keeps aligned with the borders and does not slides out of the enclosure faceplate.
The little defects, shades, and bubbles, disappeared as the adhesive dried out.
The Fuzz-Wah pedal finished. Knobs are Main volume or Level, Fuzz Gain, Wah frequency, Wah off-on switch and tone cut off-on switch. Footswitch is a true bypass.

The pedal finished and powered-on.

Monday, 24 November 2014

Rezzonics version of the Shin-Ei Fuzz-Wah - debug and verification (2/4)

The Fuzz-Wah pedal must first be powered with an external +9V DC power supply (AC/DC adapter or 9V battery). If an external AC/DC adapter is used tip is connected to - and sleeve to +.
See this blog entry for additional information on debugging instruments used (multimeter, signal generator and oscilloscope)
The first stage is the verification of DC voltages with a multimeter, +9V DC input is doubled by U1 charge pump regulator ICL7660S. The voltage at the output of the dual diode D2 is actually closer to +16V due to the diodes drop.
We will compare the results of the real pedal with the LTSpice simulation.
Fuzz-Wah pedal schematics
LTSpice Schematics
The next step is to use a signal generator and check the signals on the different test points with an oscilloscope. I used a 2.5 kHz 0.3V peak-to-peak sinewave at the input. See figure 1.
Fig 1. 2.5 kHz 0.3 V peak-to-peak sinewave at the input (TP1)
Q1 and Q2 amplify the input signal and define the maximum gain of the signal. Gain potentiometer R9 allows reducing the level of the amplified signal.

The signal at TP2 after a two transistors (Q1, Q2) amplifier is amplified by 15.4 with a voltage amplitude of 4.63V peak-to-peak
Fig 2. 2.5 kHz 4.63 V peak-to-peak sinewave after Q1-Q2 amplifier (TP2)
Fig 2.1. LTSpice simulation at TP2
Q3 is a transistor amplifier. Signals at the collector and emitter are used as input  to the octave doubler Q4, Q5. Gain potentiometer R9 is set to maximum. The signal at TP3 at the base of Q5 and connected to the emitter of Q3 through a resistor in series with a capacitor has an amplitude of 4.19 Vpp and appears slightly clipped on the positive cycles.
Fig 3. 2.5 kHz 4.19 Vpp clipped sinewave after Q3 emitter at Q5 base (TP3)
Fig 3.1. LTSpice simulation at TP3
The signal at TP4 at the base of Q4 and connected to the collector of Q3 through a resistor in series with a capacitor has an amplitude of 5.66 Vpp and appears clipped on the positive cycle and sharped on the negative cycle.
Fig 4. 2.5 kHz 5.66 Vpp clipped and distorted sinewave after Q3 collector and Q4 base (TP4)
Fig 4.1. LTSpice simulation at TP4
Q4 and Q5 implement the octave doubler, the signal at TP5 at Q4-Q5 collectors has a frequency of 5 kHz, double of the input signal, with an amplitude of 0.77 Vpp. Both cycles are strongly clipped.
Fig 5. 5kHz 0.77 Vpp frequency doubled and clipped signal at Q4-Q5 collector (TP5)
Fig 5.1. LTSPice simulation at TP5
Dual Schottky diode D1 in series with R22 (100 ohms) clips the signal in a similar fashion to a germanium diode (see this blog entry for additional information on the use of Schottky diodes to replace germanium diodes). Signal on TP9 is very similar to the signal at TP5, since between them there is only a 10uF AC coupling capacitor to remove DC biasing.
Fig 6. 5kHz 0.78 Vpp frequency doubled and clipped signal at R22 + D1 clipping diode (TP9)
Fig 6.1. LTSpice simulation at TP9
R25, R26, C12, C13 implement the tone cut filter, R23, R24 implement a voltage divider so that the signal level at TP10 is similar when cut tone is used or bypassed by S2 switch.
Signal at TP6 is TP9 clipped and frequency doubled signal after the tone cut filter. It has an amplitude of 0.61 Vpp.
Fig 7. Signal after Tone cut filter 0.61Vpp (TP6)
Fig 7.1. LTSpice simulation at TP6
Signal at TP8 is TP9 clipped and frequency doubled signal after voltage divider and has an amplitude of 124 mVpp. R27 is the main volume potentiometer and is set to maximum.
Fig 8. Signal after voltage divider 0.124 Vpp (TP8)
Fig 8.1 LTSPice simulation at TP8
Q6 is another transistor amplifier which is the output of the fuzz effect without wah. Fuzz signal at TP12 when tone cut filter is bypassed has an amplitude of 0.53 Vpp
Fig 9. Signal at the output of Fuzz effect with Tone Cut filter bypassed (TP12)
Fig 9.1. LTSpice simulation at TP12
Signal at the output of the fuzz effect (TP12 ) when tone cut filter is on has an amplitude of 1.28 Vpp.
Fig 10. Signal at the output of Fuzz effect with Tone Cut filter on (TP12)
Fig 10.1 LTSpice simulation at TP12
Q7, Q8, Q9 transistors implement the Wah effect. R43 is the Wah potentiometer that tunes the Wah band-pass filter frequency.
Signal at Q7 collector (TP13) with Tone cut filter off and wah at potentiometer at 0 has an amplitude of 2 Vpp.
Fig 11. Signal at Q7 collector with Tone cut filter off and Wah pot at 0 (TP13)
Fig 11.1. LTSpice simulation at TP13
Signal at Q7 collector (TP13) with Tone cut filter off and wah at potentiometer at 10 has an amplitude of 99 mVpp. 
Fig 12. Signal at Q7 collector with Tone cut filter off and Wah pot at 10 (TP13)
Fig 12.1. LTSpice simulation at TP13
Signal at the output of Wah effect (TP15) with Tone cut filter on and wah pot at 0 has an amplitude of 2.9 Vpp.
Fig 13. Signal at Wah output with Tone cut filter on and Wah pot at 0 (TP15)
Fig 13.1 LTSpice simulation at TP15

Thursday, 20 November 2014

Rezzonics version of the Shin-Ei Fuzz-Wah (not a clone!) - Schematics, PCB layout, simulations (1/4)

I am a big fan of shoegaze / noise rock bands and one of my favourites bands is Jesus & Mary Chain and their album Psychocandy. That album is well known for its unique and characteristic dense wall of sound with that white noise (switch-on vacuum cleaner, washing machine and all appliances and let them couple to the guitar amp) that served as inspiration for a coming shoegaze generation of bands: Ride, My Bloody Valentine, Cocteau Twins, Lush, Spacemen 3, Loop... and even today shoegaze bands like A Place To Bury Strangers, Skywave, Ceremony, Screen Vinyl Image or 93MillionMilesFromTheSun, The KVB, The Lost Rivers, The Soft Moon...
It seems that one of the keys of that sound is the use of a Shin Ei Fuzz-Wah (8 transistors) pedal. This is a two/three effects into one pedal, a 6 transistor fuzz with octaver (high octave) plus a 2 transistor Wah effect at the end. JAMC did not make lots of use of the Wah pedal as it is normally used, but they used it to reinforce the gain of a band in the mid tones to couple the sound, so they set the pedal at one position and didn't move it.
These are the schematics of the original Shin Ei Fuzz-Wah pedal:

The fuzz with octaver is also used on the Univox/Unicord Super Fuzz (6 transistors) pedal. See schematics here:
Find here a demo video of the Shin Ei Fuzz-Wah pedal:
With all that in mind I made a first version of the Super Fuzz with Octaver pedal with scrapped through-hole conventional components on a Vero board using 2N2219A transistors 
 The first version on the Super Fuzz pedal can be seen here on the left of the picture:
The result was quite deceiving, the circuit has lots of gain and it was too noisy, too much, even for playing a PsychoCandy cover, specially when powered at 9V. A higher DC power of 15V reduced a bit the noise but it was still an undesirable result.

Schematics

I decided to restart the work using surface mount devices (SMD), a professional PCB and include the Wah sections as well as several improvements and modifications to the original circuit.
These are the schematics of the Super Fuzz-Wah design:

I used BC847C high gain (hfe = 520typ) SMD SOT-23 NPN transistors.
The improvements on the circuit are the following:
  1. Replacing the two clipping germanium diodes by one dual BAT54S Schottky diode SOT-23 in series with 100 ohms (D1, R22).
  2. Replacing the Wah bulky and expensive inductor by a gyrator circuit based on a transistor (Q9) plus capacitor and biasing resistors.
  3. Doubling the 9V DC power supply, with a charge pump circuit based on Intersil ICL7660SCBA
Check my post on replacing germanium diodes with Schottky diodes plus series resistor.

The charge pump regulator ICL7660SCBA allows doubling the power supply from 9V to 18V, however this charge pump regulator uses an internal oscillator with a quite low and audible switching frequency of 10 kHz. If it is used in its default oscillation mode this frequency is seen as a ripple frequency on the power supply, since this pedal has lots of gain in its transistor circuits, this ripple noise can be amplified and heard as a very nasty and unpleasant high pitch noise. For that reason, it is absolutely required to short pin 1 (boost frequency pin) with pin 8 (V+) in order to get a higher switching frequency of 35 kHz, out of the audible spectrum.

Wah circuit simulation with LTSpice

The following schematics shows both Wah circuits: to the right the original wah circuit based on an inductor, and to the left the circuit based on a gyrator circuit, where the inductor has been replaced by a transistor plus capacitor and biasing resistors. Basically the circuit framed by the square on the right side is replaced by the circuit framed by the square on the left.
This is the frequency response of the original circuit when varying the wah potentiometer:
It is a tuned band-pass filter with its peak moving from 240 Hz to 1.28 kHz, increasing the gain from 12.5 to 23.5 dB.
And this is the frequency response of the gyrator circuit when varying the potentiometer:
Again it is a tuned band-pass filter with its peak moving from 260Hz to 1.28 kHz, slightly increasing the gain from 16.5 dB to 19.2dB.
So we obtain a quite similar result with even a more stable gain peak.

PCB Layout

The PCB was made on two layers with dimensions of 80 mm x 50 mm:

Schematics and PCB layout was designed using Eagle CAD. The PCB layout can be uploaded into Eurocircuits website, and a quote can be obtained immediately, I paid 70 € for 2 boards prototypes in a 7 day turnaround, the quality is really good.
I purchased the components at Mouser website. You can find here the BoM, total cost of components for one prototype was 26 €.
To solder the components I used a low temperature (138°C ) CR11 solder paste Sn42Bi58 and a hot air soldering station, the results are very professional and clean. This is the finished PCB with all components (except external switches, jacks and potentiometers) mounted.
All the cables, jacks, connectors, switches and potentiometers soldered and ready for debug and verification

Sunday, 16 November 2014

Tube Simulator - Sound check and AC30 emulators comparative

I wanted to do a sound check of the TubeSim v1.0 VOX AC30 valve amplifier emulator and a comparative with other VOX AC30 amp emulators. This is it.

First I found on the web a sound file with a clean guitar riff: Then I fed this sound file from the computer Line output into the TubeSim Line input. The TubeSim 25W 8 Ω output was connected into the Rezzonics v12 DIY Cabinet speaker with a Celestion Vintage 30 12''. The output sound was recorded with Audacity in the computer using an AKG D40S dynamic condenser microphone (it's a vocal microphone but that's the best I could get for the sound check)

This is the TubeSim v1.0 guitar riff sound with gain at maximum, no bass, no treble, tone cut off:

I think the sound has a nice crispy distortion, with lots of mids and lots of sustain.

The best would have been to compare it with a real VOX AC30 valve amplifier, but unfortunately I don't own one.
I decided to compare with several amp emulators.
First the open source amp emulator Poulin HyBrit Head v1.1 in the same conditions, maximum gain, no equalization:

The Poulin HyBrit Head v1.1 has a lot of gain too, it's more saturated quite brittle with more treble than the TubeSim v1.0

Now the GuitarRig 2 ACBox GuitarRig 2 ACBox resembles more the TubeSim, less saturated than the Poulin with maybe more bass than the TubeSim v1.0

Amplitube 3 offers two different AC30-like amp emulators: Amplitube 3 Hot AC30: The Amplitube 3 Hot AC30 is less crispy, lots of bass, not much saturation, it's a bit muddy and more somber, less sustain. In my opinion is the worst sounding of all the amp emulators.

Amplitube 3 Hot AC30 Copper:
Amplitube 2 Hot AC30 Copper is a bit more saturated than the previous one, not much sustain, less muddy, more mids, similar to the Guitar Rig 2 ACBox but with less treble, less crispy than the Guitar Rig 2 and the TubeSim.

Then I coneccted the Line Output of the Tube Sim directly into the Line-In of the computer, first with the Speaker Simulator bypassed: And now with the Speaker Simulator active:
The Speaker Simulator reinforces the middle tones as a guitar speaker would do.

Find here the playlist to listen to all the different sounds used in the comparison: Which one is your favourite? Why?

Friday, 14 November 2014

DIY 1x12'' Cabinet Speaker - Vintage 30 8Ω 2'' speaker

DIY 1x12'' Cabinet Speaker - Vintage 30 8Ω 12'' speaker

In order to test the TubeSim 25W 8Ω output I decided to make a DIY 1x12'' cabinet speaker with a classic Celestion Vintage30 8Ω speaker installed.
I was inspired by the series of 4 magnificent and instructive videos made by thefirstbab. The first one of the series can be seen here:

I changed the dimensions of this cabinet based on a 1912 Marshall to provide nicer proportions to the cabinet. To do so, I used (approximately) the golden ratio 0.618 and came up with the following external dimensions: 600 x 400 x 300 mm (W x H x D) for a total internal volume of approximately 50 liters.
I used 18 mm (3/4'' approx.) thick plywood (from exotic okoumé wood) already precut acquired in a DIY store. The wood cleats were cut from two 22 mm x 2400 mm beech squares
The panels are fixed with wood glue and 3.5 x 30 mm wood screws. Wood filler paste was used to fill holes and imperfections. Find here below the cabinet mechanical drawings (AutoCAD was used but open source LibreCAD can also be used)

The first step is to glue and screw the bottom panel to both sides. To ease screwing, 2 mm holes are drilled. In order to hide the head screws, shorter 6 mm holes are drilled too, once the panels have been glued and screwed together, wood filler paste is applied to completely hide holes and head screws. Then the top panel is glued and screwed to both sides.

Four 22 mm x 564 mm thick wood cleats are placed on the internal top, bottom, front and back sides. Note that front cleats are fixed aligned to the front borders, while rear cleats are fixed leaving 20 mm space to the rear borders to allow adding external rear cover panels. Picture below shows the bottom wood cleats glued.

Two 22 mm x 320 mm wood cleats are glued and screwed to the front left and right sides. Shorter and beveled wood cleats 22 x 270/242.5 are fixed on the rear left and right sides. This shape allows introducing the front panel that will hold the speaker. The picture below shows the wood cleats glued, ready to be screwed. The 2 short beveled cleats resulting from cutting must be reserved to finish the rear frame once the front panel is installed.
Two beveled cleats 22 mm x 210/189 mm are fixed on the bottom sides, while shorter beveled cleats 22 mm x 107/85 mm are fixed on the top sides. This allows sliding the front cover from the rear top of the case, place the bottom side of the front cover panel onto the internal bottom front side and then pivot the front cover panel to place the top side on the internal top front side of the case as shown by the red traces of the mechanical drawing, see the two pictures below. To allow this pivotal movement, top side reinforcement beveled cleats must be shorter.
Three circles of Ø283 mm, Ø297 mm, Ø309 mm respectively are drawn in the center of the front cover as recommended by the speaker manufacturer Celestion for the Vintage 30 model. The position of the four speaker fixing screws are also drawn, they are 210 mm apart from closest screw, horizontally and vertically.
The external circle of Ø309 mm represents the maximum dimensions of the speaker.
The middle circle of Ø297 mm represents the placement of the four screws. Logically the relationship between the diameter of the circle and the sides of the square is respected: sqrt(2*210*210) = 297 mm.
The internal circle of Ø283 mm diameter represents the hole that must be left for the speaker sound to come out of the box. An electrical jigsaw has been used to make this hole and then the borders slightly softened with a wood file and sandpaper.
All external sides and corners must be rounded. I don't have a router, so I had to use a wood file. The radius of this rounding must correspond to the internal diameter of the corners used. Note that Marshall corners used in the first video have a larger non standard radius 1'' (25 mm) and rear sides are not rounded. Check this article Choosing amp corners for further info.
I purchased all cabinet and amp accessories in this great website: Tube-Town. I bought a set of 8 standard black corners 1/2'' (12.5 mm internal radius). In this case, all corners are identical and all the sides of the cabinet must be rounded, rear sides too.
I traced lines parallel to the sides at 6.3 mm and 12.5 mm (they can be seen in the first picture), with the wood file I made 45 degrees between the lines at 6.3 mm and then I finished the rounding up to the 12.5 mm lines, I cut a 12.5 mm semicircle in a thin plywood piece to be able to properly control the radius while filing, I used one of the corners to be sure that it adjusted properly to the corners of the cabinet.
I then filled in any irregularities with wood paste and sanded all the surfaces, see pictures below:


Next step is spray painting in matte black all the internal sides of the cabinet. Several layers will be needed for a good result:

Front cover is painted on both sides. Before painting it file the borders leaving at least 2 mm margin on each side and make sure that once the grill cloth is fixed on it there is enough place inside the cabinet to put the front panel in place. Speaker hole screws were previously drilled and hole borders were lowered in order to hide countersink screw heads. Head screws will have to be painted in black too, so they cannot be seen through the grill cloth. Screws will have to be put in place before fixing the grill cloth.

It's time to check the accessories fitting. I purchased a black strap with nickel ends and four rubber feet at Tube-Town.

I wanted a vintage look for the Vox AC30 TubeSim cabinet with Celestion Vintage 30, so I opted for a golden vintage grill cloth, two meters of Red basket VOX type tolex and two meters of white medium piping to enhance and frame the grill cloth.
Before fixing the grill cloth, place the front panel in place and make the holes corresponding to the fixing screws. To fix the grill cloth to the front cover I used a cheap upholstery stapler. Place the four speaker screws, before fixing the grill cloth. Use a hairdryer to heat the grill cloth before stapling it so that when cold is as stiffened as a drum batter head. It's important to select the proper staples, if they are too short or too thick they may not be pushed to the end. This actually happened to me when I fixed the white piping to the beech cleats frame, since solid beech it's a very hard material and I had to finish with some hammer taps.
Use a soldering iron to melt the grill cloth over the holes that will be used to fix the front panel with screws to the cabinet, otherwise grill cloth can be damaged when screwing the front panel to the cabinet.

Gluing tolex is probably the most tricky part of this project, at least for me, since it was the first time. I recommend watching thefirstbab video series I mentioned at the beginning of this post and also the videos from Uncle Doug:

A neoprene glue spray is recommended for gluing the tolex to the cabinet. I drew the shape of the cabinet in the back of the tolex (see picture below), marking the place where the cabinet borders had to coincide and leaving 1 cm margins. The tolex is only one piece 2m long and the joint should be placed at the center bottom of the cabinet. Corners are not yet cut, this will be made afterwards to compensate for tolerance or fabric deformation. The tolex piece is rolled inside out to ease manipulation while gluing, exposing the first 300 mm section. Glue is sprayed on the central square of the tolex section and half of the bottom cabinet side and let dry for some seconds, then applied from the center of the bottom side. With a clean cloth, press the tolex fabric from inside to outside to expel any bubbles. Glue is sprayed on one side of the cabinet and the center square of the second section, special care must be taken on the border, press the tolex on the border carefully to avoid forming bubbles. Process follows on the top side. Careful must be taken to be sure that the tolex is properly aligned to the cabinet while unrolling the tolex piece over the cabinet and the drawn lines follow the border of the cabinet.
When both tolex extremes meet on the bottom side of the cabinet, they must overlap and with the help of a ruler and a cutter they are both cut in the middle of the overlapping section, remove the top strip just cut, detach the top fabric extreme and remove the strip left on the bottom fabric, so that a perfect joint is left between the two fabric sections.
Now it is time to glue the tolex on the front and rear sides of the cabinet, this is even trickier. Follow the videos I posted before. Fold symmetrically the fabric at the corners and make a cut in the middle, overlap both sides of the fabric and make a 45 degree cut from the outer corner to the inner corner, but no longer!!, otherwise you will leave the internal borders without material, see on the drawing above how the 45 degree angles only apply to the first section of the border exposed to the front or the rear, but it does not apply to the internal sides. Any excess of glue on the tolex can be cleaned with white spirit.
Leave to dry the neoprene glue for at least 24 hours.
Cut and staple or nail down the piping to the rear side of the front frame. Put in place the front panel with the grill cloth and speaker screws and fix it with screws to the cabinet from inside.
Rubber feet and handle can be fixed now doing some small cuts on the tolex at the place corresponding to screw holes. Corners can be fixed with two screws per corner, make sure that they are properly placed with screw ears on the cabinet inside.
See below the front view of the finished speaker cabinet.
I decided to do a rear open cabinet. Given the volume of air inside the cabinet, a closed cabinet could damp the bass sound pressure waves.
From the rear panel, 2 pieces of 115 mm wide are cut for the top and bottom covers, middle cover is unused. A Ø24 mm hole is made with a wood drill at the center of the top cover to place the speaker jack. Tolex is applied to both pieces and 2 mm holes are equally spaced all around to fix both covers with screws and countersunk flange finishing washers to avoid damaging the tolex with the screws and obtain a better finishing. Radial cuts are practiced with a cutter over the tolex at the connector hole on the top cover and connector is fixed with two screws.
The speaker connector is an hybrid SpeakON/ 1/4'' jack Neutrik connector. Speaker is fixed into the front panel using washers and bolts.
speaker cable 2 x 1.5 mm2 is soldered between the speaker connector and the connector taking care of + and - connections.
Top and bottom rear panels are fixed with abundant screws and countersunk flange type washers.
See below the rear view of the finished speaker cabinet.
The 1x12'' cabinet speaker with the 25W TubeSim amplifier.
I decided to personalize the cabinet speaker adding a Rezzonics logo at the top front of the cabinet. I named the cabinet speaker Rezzonics v12 for the 1x12'' speaker installed.
I used Inkscape for the logo design, I tried several fonts: Magneto, Aeroplane Flies High, Mottel, Norton and Puma Oblique. The Magneto font is the one I most liked.
Several layers of extruded extended text are overlapped to provide a 3D volume effect, with a silver grey in the front layer, darker grey in the middle layer and black on the top layer:
I used some recycled materials to make the logo and I changed the colors: Bottom layer aluminum grey, middle layer in black and top layer in silver. A piece of 2.5 mm plywood coated with aluminium was used as the base or bottom layer. Another piece of 2 mm plywood painted in black was used for the middle layer, and a 1 mm soft plastic lined with aluminum paper for the top layer.
Printed paper was glued to the plywood pieces and then the text form sawed with a scroll saw. For the thin plastic layer I used scissors. The three layers are centered and glued and then the whole logo is lacquered.
This is the final result.
Rear view of the cabinet speaker with Celestion Vintage 30 speaker installed:
Front view of the finished cabinet with logo and 25W TubeSim amplifier.
Now it's time for the sound check and comparative with AC30 emulators!!