Luxman PD277 (barn find)
- By redrabbit
- Analogue Source
- 11 Replies
Looking around my 90yo aunt's home, I came across a neglected PD277 DD automatic player. No lid...yet.
I found the service manual (pdf).
I am considering "at least" getting it working.
I will post progress pics.
I found the service manual (pdf).
I am considering "at least" getting it working.
I will post progress pics.
Symamp - simple complementary-symmetrical amplifier (sample built)
- By PMA
- Solid State
- 59 Replies
Symamp – simple complementary-symmetrical amplifier
I have decided to design and build a sample of complementary-symmetrical amplifier that should be:
THD is not a goal here, as nonlinear distortion below 0.1% is barely audible and if yes, than only with a sine tone at certain level. Not with music.
So, this is the circuit schematics.
T1-T4, Q1-Q4 make the complementary-differential pairs loaded by current mirrors. Q5, Q6 and T5,T6 make a folded cascode VAS. Folded cascode is important to keep VAS current stability vs. input offset voltage. It works very well. Q10, Q11 and T20, T30 make a conventional 2EF output stage.
Loop gain stability margin is 62° and the circuit is stable even with the capacitive load, without the need to use an output coil.
I have built and measured a functional sample. The PCB is too large for the reason it must fit to my pre-drilled prototype amplifier case. The PCB is carefully designed with respect to signal grounds, please note very low level of mains related components in the measurements below.
Measurements
I have decided to design and build a sample of complementary-symmetrical amplifier that should be:
- simple
- reliable
- stable
- easy to build
- with sufficient parameters
- 2x50W/4ohm at 1% THD
THD is not a goal here, as nonlinear distortion below 0.1% is barely audible and if yes, than only with a sine tone at certain level. Not with music.
So, this is the circuit schematics.
T1-T4, Q1-Q4 make the complementary-differential pairs loaded by current mirrors. Q5, Q6 and T5,T6 make a folded cascode VAS. Folded cascode is important to keep VAS current stability vs. input offset voltage. It works very well. Q10, Q11 and T20, T30 make a conventional 2EF output stage.
Loop gain stability margin is 62° and the circuit is stable even with the capacitive load, without the need to use an output coil.
I have built and measured a functional sample. The PCB is too large for the reason it must fit to my pre-drilled prototype amplifier case. The PCB is carefully designed with respect to signal grounds, please note very low level of mains related components in the measurements below.
Measurements
I²C Autoformer Attenuator
- By justilew
- Electronic Design
- 9 Replies
Hello,
I want to build an attenuator using a couple Intact Audio Autoformers and control the attenuation level from an Arduino device over I²C. I am really a software guy but I didn't see anything quite like this on these forums, this is my first crack at PCB design. Does this circuit look ok? Am I missing anything? Is something wrong? Is there a better way that reduces the number of relays required?
Thanks in advance!
I want to build an attenuator using a couple Intact Audio Autoformers and control the attenuation level from an Arduino device over I²C. I am really a software guy but I didn't see anything quite like this on these forums, this is my first crack at PCB design. Does this circuit look ok? Am I missing anything? Is something wrong? Is there a better way that reduces the number of relays required?
Thanks in advance!
SPDIF input WM8804 and using TDA1387x8 as output (ProtoDAC clone)
- By Dreadcelorio
- Electronic Design
- 4 Replies
So... This is my first real post on this forum and I have a question for all you tech savvy people.
If using WM8804 chip for SPDIF for input, could I be using ProtoDAC TDA1387x8 for output?
The reason for this conversion is that I would like to stream the sound from my computer by SPDIF to the ProtoDAC. But the "normal" ProtoDAC does not accept audio in because of the TDA1387x8 (TDA1541A) chip. I really like the simplicity of the ProtoDAC with minimal components and clean sound an would like to not use USB devices for the audio transport. The cleanest way I can think of transport would be directly to the ProtoDAC board. That way there would only be one board or accessory on the Raspberry.
I have made a schematic of how I think it could work but I really need help to figure this out and perhaps find even a better solution. I have only used other schematics to make my own edit so there should be errors in it and even some things that might not work.
So please help me make this one-stop-hat work 🙂
If using WM8804 chip for SPDIF for input, could I be using ProtoDAC TDA1387x8 for output?
The reason for this conversion is that I would like to stream the sound from my computer by SPDIF to the ProtoDAC. But the "normal" ProtoDAC does not accept audio in because of the TDA1387x8 (TDA1541A) chip. I really like the simplicity of the ProtoDAC with minimal components and clean sound an would like to not use USB devices for the audio transport. The cleanest way I can think of transport would be directly to the ProtoDAC board. That way there would only be one board or accessory on the Raspberry.
I have made a schematic of how I think it could work but I really need help to figure this out and perhaps find even a better solution. I have only used other schematics to make my own edit so there should be errors in it and even some things that might not work.
So please help me make this one-stop-hat work 🙂
Make TDA1540 Tube output DAC
- By wyqgyn
- Vendor's Bazaar
- 1 Replies
The love for TDA1540 belongs to everyone. Today we can still use the Philips LHH2000 and hear its warm sound. However, it is very difficult to obtain the output transformer of LHH2000. I think only through TUBE output can I find the feeling of LHH2000. I think I will share with him. You can also purchase him.He works great and can recall warm vintage sounds. You can purchase PCB boards and ship them from China. If you are a friend of the European Union. Please provide the IOSS number, which consists of IM and 10 digits. The mailing time is about 10 days. All PCBs consist of five parts: audio input board, format conversion board, DAC decoding board, HV power and power board. You can play app content through a Bluetooth chip (purchased in China, manufactured in Shenzhen), or use CS8412 coaxial to play CD content. COMBO384 can also be used to connect to a computer for playback, and there is also an external input IIS interface for connecting to Philips turntable playback. I will provide Taobao product connections. You can use Taobao's overseas warehouse to purchase. If you need assembly instructions and BOM list, please send an email application: 410746700@qq.com
Ferrite clamp on power supply wiring
- Solid State
- 6 Replies
Some Denon amplifiers have Ferrite clamps between transformers/power supply board and pre/power-amp circuitry.
I always thought that most well designed amplifiers have efficient rejection and don't need anything like this?
I always thought that most well designed amplifiers have efficient rejection and don't need anything like this?
why should a 0204 MELF resistor have a lower current noise than a 0207 MELF?
This is from the Vitrohm ZCM data sheet. The larger resistor has lower current noise as it should for 20 k and higher. Below, noise no longer decreases as resistance decreases. The smaller resistor has the same behavior below 2 k. This results in lower current noise in the smaller resistor from about 7.5 k.
I don't get why this should be the case. The larger resistor body needs a wider trace to achieve the same resistance as the shorter trace on the smaller body.
PS: Vishay Draloric SMM0207 has the exact same graph for current noise
The non-linearity graph of the Vitrohm is also exactly the same. Was there a standardization or is Vitrohm trying to be a second source, much as many second sources for classic Japanese transistors simply copy the data sheet?
I don't get why this should be the case. The larger resistor body needs a wider trace to achieve the same resistance as the shorter trace on the smaller body.
PS: Vishay Draloric SMM0207 has the exact same graph for current noise
The non-linearity graph of the Vitrohm is also exactly the same. Was there a standardization or is Vitrohm trying to be a second source, much as many second sources for classic Japanese transistors simply copy the data sheet?
Dead B&K CS-117 Preamp
- By yardiron
- Analog Line Level
- 25 Replies
I recently came across a B&K CS-117 Preamp, it was part of a larger lot of stuff I dragged home and I was told it 'just quit working one day' but its former owner. Its spot clean inside an out.
I did Google search and saw that the transformer is a likely issue on these. I also searched for a manual or schematic but didn't see any.
With this thing plugged in, I'm seeing two voltages out of the transformer, both 24v and 13.5v The transformer has nothing on it saying what it is or what voltage it should be. Following the wires to the main boards, I can trace the power to the boards and can see power is getting to the switch.
The switch does nothing there's no light, no click, no relay noise, nothing. The fuse I found is good, and the switch tests out as far as continuity.
There's a few opp amps on the board but I have no idea what they do or if they could even be at fault but this seems like a power issue not a failed component.
After hearing it just stopped playing, I was expecting to see something more drastic or a dead transformer but from past experience, most transformers usually fail by either just not making power or by short circuit across the primaries.
This is producing voltage and I can follow power from the power supply area of the main board to various points, including the selector/power switch on the left side.
It does use an LC7818 chip on the output board which I see has been a failure point on some receivers but without a diagram, its hard to tell how its being used on this.
There are no indicator lights working on any of the switches, it does not pass audio in bypass mode.
It acts as if there is no power but I have voltage on the main board which tells me the transformer is not 'dead'. I'd at least expect some sort of function.
The lights on the switched do show continuity so their not burned out but they're seeing no power.
I'm certainly just a novice at these things but what I'm thinking is that if it won't bypass sound, the issue has to be in the switching of the IC on the output board? I would think that with the bypass switch depressed, it should function solely as a volume control and nothing else?
Does anyone have any experience with these?
In the past I have run across a failed LC7118 that failed on a 90's receiver where it was being used in the tape monitor circuit, and thus blocking sound from the outputs, but without a diagram I'm guessing, and then, if it is bad, what likely killed it?
Although I figured my next step is likely to pull both boards out and look closer to how the pcb is laid out but figured I'd ask here before I over think this thing.
I did Google search and saw that the transformer is a likely issue on these. I also searched for a manual or schematic but didn't see any.
With this thing plugged in, I'm seeing two voltages out of the transformer, both 24v and 13.5v The transformer has nothing on it saying what it is or what voltage it should be. Following the wires to the main boards, I can trace the power to the boards and can see power is getting to the switch.
The switch does nothing there's no light, no click, no relay noise, nothing. The fuse I found is good, and the switch tests out as far as continuity.
There's a few opp amps on the board but I have no idea what they do or if they could even be at fault but this seems like a power issue not a failed component.
After hearing it just stopped playing, I was expecting to see something more drastic or a dead transformer but from past experience, most transformers usually fail by either just not making power or by short circuit across the primaries.
This is producing voltage and I can follow power from the power supply area of the main board to various points, including the selector/power switch on the left side.
It does use an LC7818 chip on the output board which I see has been a failure point on some receivers but without a diagram, its hard to tell how its being used on this.
There are no indicator lights working on any of the switches, it does not pass audio in bypass mode.
It acts as if there is no power but I have voltage on the main board which tells me the transformer is not 'dead'. I'd at least expect some sort of function.
The lights on the switched do show continuity so their not burned out but they're seeing no power.
I'm certainly just a novice at these things but what I'm thinking is that if it won't bypass sound, the issue has to be in the switching of the IC on the output board? I would think that with the bypass switch depressed, it should function solely as a volume control and nothing else?
Does anyone have any experience with these?
In the past I have run across a failed LC7118 that failed on a 90's receiver where it was being used in the tape monitor circuit, and thus blocking sound from the outputs, but without a diagram I'm guessing, and then, if it is bad, what likely killed it?
Although I figured my next step is likely to pull both boards out and look closer to how the pcb is laid out but figured I'd ask here before I over think this thing.
Hello from Copenhagen, Denmark
- Introductions
- 3 Replies
Hi all
My name is Matthæus, and I'm a new user at DIY Audio. I run my own creative marketing agency, where I provide brand consultancy to both new and established brands, and combine my work with speakers as a tool for research.
I'm still fairly new to speaker building, but very eager to learn more and continue experimenting with different designs and build.
Attached is my latest project using Monacor drivers and Fountek tweeter.
My name is Matthæus, and I'm a new user at DIY Audio. I run my own creative marketing agency, where I provide brand consultancy to both new and established brands, and combine my work with speakers as a tool for research.
I'm still fairly new to speaker building, but very eager to learn more and continue experimenting with different designs and build.
Attached is my latest project using Monacor drivers and Fountek tweeter.
The Walnut Dipoles
- Multi-Way
- 89 Replies
15” Open Baffle 2-way with Live Edge Wood, Constant Directivity, Passive Xover and Punchy Bass
What would happen if a Magnepan MG1.7 and a Klipsch Heresy had a baby?
Many builders here have seen my Bitches Brew Open Baffle Speakers, the Flanagangsters, and Live Edge Dipoles. I love using slabs of live edge wood to make Dipoles. For this system I had a beautiful piece of Walnut in the garage. I wanted to create a passive design that would come as close as possible to these larger, active DSP systems while using a passive crossover, thus maintaining the simplicity of a traditional stand-alone speaker.
At only 35 pounds (16kg), these register at 1/2 to 1/3 the weight of the other designs listed above. Dimensions 28”H x 19”W x 18”D (71cm x 48cm x 46cm).
Sensitivity 93dB
Impedance 4 ohms
Power rating 100w/ch
Frequency Response 40Hz-20KHz
I wanted the expansive, room-filling sound of Open Baffle; and wanted to achieve bass reflex punch without sounding “boxy.” I also wanted Constant Directivity, meaning that when you move off axis, the level changes but the tonal balance does not. This provides excellent imaging for every seat in the house and not just the one “sweet spot.”
Above: Frequency response in real room, 1/6th octave. No attempt to exclude room reflections. Average of 5 positions at a distance between 1 and 2 meters.
Above: 1/6th octave frequency response at 0, 15, 30, 45, 60, 75 and 90 degrees.
Above: Polar plot from -90 degrees to +90 degrees on front plane of the speaker. Largely maintains constant directivity across the entire band, with cardioid pattern between 150Hz and 400Hz. (This is inevitable because of the U-frame enclosure and is the tradeoff incurred by extending the bass an octave downward to 60Hz, as compared to a flat baffle.) There's slight widening of the pattern around 1700Hz, just above the crossover frequency. Radiation is very even across a +/-30 degree listening window.
I chose the Eminence Alpha 15A woofer with these parameters:
SPL 94dB
Fs 41
Qt 1.26
Xmax 3.8mm
it works very well in an Open Baffle. The high Q means it already has +2dB built in bass boost to counteract the rolloff of the baffle, which starts at around 65Hz. Further down I’ll explain the Bass EQ circuit I designed to extract an extra 5.5dB between 40-50Hz.
After much deliberation I chose the SB Acoustics Satori TW29R tweeter. I mounted it in a Visaton WG148R waveguide.
The Satori is one of the best tweeters I’ve used. It has very high resolution and great imaging, while still retaining the gentle edge of a soft dome. Transparent and revealing without being excessively analytical.
I chose this tweeter because I didn’t want the sound of a traditional compression driver. The kind of horn one would typically mate this with might easily sound nasal or “shouty” despite whatever EQ magic one might throw at it. I wanted a tweeter that, when mounted in a waveguide, could keep up with the 94dB sensitivity of the woofer and even give an extra +1 or +2dB at the high end.
With its standard faceplate, this tweeter has about 94dB SPL in the 10-20KHz range and a waveguide raises SPL further below 10KHz.
“Lambda” U-Frame Open Baffle
I like using triangular “wings” on the sides of OB speakers to extend bass response. Without wings, these woofers will start rolling off at 120Hz and you’ll get little deep bass. With wings, or U-Frame dipole that is lambda shaped in the side view, the cutoff begins around 65Hz and drops 6dB per octave. The triangle shape keeps the distance from woofer to edge spread across a wide range rather.
I discovered a way to add 4-7dB in the 40-60Hz range so the sound is a little “plump” in the deep bass range. I describe this in the next section.
Passive Bass Boost
This design adds a 5.5dB boost at 45Hz using an unusual passive high pass filter. I can’t be the first person in history to do this, but I’ve never seen this explained or modeled anywhere else. These components are in section “1” of the crossover schematic: a 500uF capacitor and 20mH inductor.
I explain the circuit in section 1 in detail in my post “Open Baffle Bass Boost: +4 to +7dB w/ Passive Xover. No DSP.” I call it the "Marshall Bass Boost." Here you’ll find guidelines and examples for designing your own. It replaces the 25-ohm impedance peak at 41Hz with a 3-ohm dip, drawing almost 4X more power from the amplifier around 45Hz.
This also serves as a subsonic filter, protecting the woofer from signals below 40Hz. Signal falls to -10dB at 30Hz and -17dB at 20Hz. It provides substantial protection from out-of-band signals. Not only do dipoles suffer from rear wave cancellation, they are easily overdriven to large excursions by frequencies you can’t hear. This filter boosts the signal where it matters and cuts it where it doesn’t. The components required for this cost about $40 per channel and are well worth the investment.
Above: Large 20mH inductor and 500uF capacitor boost response at 45Hz.
Drive Signals for Each Driver
In the red curve below you can see the +5.5dB boost at 45Hz as well as the sharp filter.
Above: The signal reaching the Eminence Alpha 15A woofer is in RED. The signal to the SB TW29R tweeter (front) is in GREEN. The signal to the PRV WG230Ti tweeter (rear) is in BLUE.
Woofer crossover (Section 2 in the schematic)
The 1mH inductor, 10-ohm resistor plus LCR notch network in Section 2 of the schematic form a shelf filter with a deep null at 1900Hz. This suppresses the +12dB breakup mode of the Eminence woofer. However, I don't roll off the woofer above that frequency. This is because that would add even more phase shift. I avoid steep crossovers except when absolutely necessary. The woofer is already set back 3-4 inches (7-10cm) behind the plane of the tweeter, so a steep crossover would only make that problem worse.
Above: nearfield measurements of woofer and tweeter and the 1250Hz crossover frequency. The woofer rolls off naturally at 12dB/octave above 3KHz. (See the drive signal to the woofer a few paragraphs above, it heads towards 0dB at high frequencies.) The lack of additional filtering reduces group delay. In my opinion the minimal filtering just sounds better.
Matching Woofer to Tweeter
I’m stretching both drivers to the limits of their range. The 15” woofer start to beam above 1KHz, and the WG148R waveguide stops being directional below 2KHz. So there is a little discontinuity in the radiation pattern between 1-2KHz.
Above: Frequency response at 0, 15, 30, 45, 60, 75 and 90 degrees. Very nearly constant directivity across the band. At about 1500Hz you can see some “bunching” of the radiation pattern, where 30-45 degrees off axis, the output is slightly stronger than on-axis. This would go away if the waveguide was 8” (20cm) diameter instead of 6” (15cm). I chose an off the shelf Visaton waveguide, but a larger 3D printed waveguide would solve this. The bunching at 300Hz is because at this frequency, the radiation pattern is more cardioid than dipole.
Tweeter Crossover
The crossover (Schematic Section 3) for the TW29R is a 24dB/octave filter at 1250Hz. There is no getting around using a steep filter for a 29mm dome tweeter being asked to go so low.
Section 4 of the schematic is an RLC notch filter. It suppresses a minor peak at 3KHz. Some builders might not feel it’s necessary, but this detail erased a last bit of objectionable coloration and leaves the upper midrange silky smooth and just slightly recessed.
The slightly rising response on axis compensates for falling response off axis. When you average the 0, 15, 30, 45 and 60 degree curves together, you get a slightly downward-tilting response, which is my goal for voicing the speakers:
Above: Average of 0, 15, 30, 45 and 60-degree response on the front side of the speakers. Plot also includes 2nd and 3rd harmonic distortion.
Mounting the Satori Tweeter to the Visaton Waveguide
The Satori TW29R tweeter has a not-quite-flat faceplate which doesn’t match the WG148R waveguide. I had to add a bead of modeling clay about 3mm thick in order to fill the gap. You can see the modeling clay in the picture:
Rear Tweeter
The rear tweeter is a PRV WG230Ti. I chose it because it has smooth response and 105db sensitivity so you can easily pad it down to match the front tweeter. I find dipoles sound best when the rear output at high frequencies is a few dB higher than the front output. This adds spaciousness without interfering with detail.
Section 5 of the schematic shows a 7-ohm resistor in series with the PRV tweeter. You can choose any value resistor you wish. This value sounds best to my ears. Below is the rear output:
Above: Rear measurements at 0, 15, 30, 45, 60, 75 and 90 degrees off axis. The system sounds best to my ears when the rear tweeter has a rising response. If you build this system you can play with that resistor and find the value that sounds best to you.
I’m normally a fan of simple crossovers, but due to the multiple conflicting priorities in getting a 2-way passive Dipole speaker to achieve: punchy bass, smooth response, Constant Directivity, high efficiency, high power handling and ultra-transparent high end simultaneously, a price had to be paid. The price was a rather complex crossover. Fortunately it’s the parts count and perfectionistic details that are complex, not the essential concept.
VituixCad files for this design are available here: https://tinyurl.com/walnutdipolesvituix
Areas for Possible Improvement?
A similar woofer with a curvilinear cone instead of straight-sided cone would likely not have the 1.9KHz breakup mode. It would also have wider dispersion above 1KHz and blend with the tweeter better. An 8” / 20cm waveguide would likewise blend better with the woofer. A more pricey version of this system could be executed with the SB Acoustics 15OB350 woofer and the SB Acoustics 29mm Beryllium Waveguide tweeter. (The crossover would have to be completely redesigned. It would still lend itself to the Marshall Bass Boost circuit.)
So… how do they sound?
These speakers throw a HUGE soundstage. They image very well everywhere in the room and have a very transparent and detailed yet silky and not-too-analytical high end. The soft dome tweeters are easy on the ears.
The bass is just slightly on the rich side, and lower midrange is warm and buttery. The overall tone is warm, spacious and detailed with a bit of extra sparkle on the top end. They are equally at home with jazz or rock. ZZ Top sounds terrific. “Burning Down the House” by the Talking Heads is an acid test for bass overload, because the bass drum and percussion parts have a lot of very low frequency energy that easily overloads many woofers, especially in OB and Reflex. The Marshall Bass Boost circuit protects these woofers from bottoming, and they can play quite loud. Bass drums and guitars are authoritative.
There is also a lot to be said for their high efficiency. They are easily 5-6dB more efficient than most audiophile speakers. They’re sensitive enough to use with “flea watt” Single Ended Tube amps.
Generally I like solid state amps better, but I do enjoy playing with tubes. Some speakers just sound better with tubes. These sound outstanding with my Yaqin MC-13L 40W amp, which has much more than enough power to drive these.
They excel with massed voices and percussion. Imaging is both spacious and precise with considerable depth. Instruments have a "bloom" and roundness that you almost never hear from standard box speakers.
My non-audiophile friends who walk in the room have an immediate positive reaction towards their appearance. The Walnut cabinets (made by Seth Cothron @studio38designs) look fantastic.
As Jerry McNutt, president of Eminence Speaker says, “The best way to not sound boxy is to not use a box.”
This is the drawing I gave my carpenter, which he used to build the speakers:
What would happen if a Magnepan MG1.7 and a Klipsch Heresy had a baby?
Many builders here have seen my Bitches Brew Open Baffle Speakers, the Flanagangsters, and Live Edge Dipoles. I love using slabs of live edge wood to make Dipoles. For this system I had a beautiful piece of Walnut in the garage. I wanted to create a passive design that would come as close as possible to these larger, active DSP systems while using a passive crossover, thus maintaining the simplicity of a traditional stand-alone speaker.
At only 35 pounds (16kg), these register at 1/2 to 1/3 the weight of the other designs listed above. Dimensions 28”H x 19”W x 18”D (71cm x 48cm x 46cm).
Sensitivity 93dB
Impedance 4 ohms
Power rating 100w/ch
Frequency Response 40Hz-20KHz
I wanted the expansive, room-filling sound of Open Baffle; and wanted to achieve bass reflex punch without sounding “boxy.” I also wanted Constant Directivity, meaning that when you move off axis, the level changes but the tonal balance does not. This provides excellent imaging for every seat in the house and not just the one “sweet spot.”
Above: Frequency response in real room, 1/6th octave. No attempt to exclude room reflections. Average of 5 positions at a distance between 1 and 2 meters.
Above: 1/6th octave frequency response at 0, 15, 30, 45, 60, 75 and 90 degrees.
Above: Polar plot from -90 degrees to +90 degrees on front plane of the speaker. Largely maintains constant directivity across the entire band, with cardioid pattern between 150Hz and 400Hz. (This is inevitable because of the U-frame enclosure and is the tradeoff incurred by extending the bass an octave downward to 60Hz, as compared to a flat baffle.) There's slight widening of the pattern around 1700Hz, just above the crossover frequency. Radiation is very even across a +/-30 degree listening window.
I chose the Eminence Alpha 15A woofer with these parameters:
SPL 94dB
Fs 41
Qt 1.26
Xmax 3.8mm
it works very well in an Open Baffle. The high Q means it already has +2dB built in bass boost to counteract the rolloff of the baffle, which starts at around 65Hz. Further down I’ll explain the Bass EQ circuit I designed to extract an extra 5.5dB between 40-50Hz.
After much deliberation I chose the SB Acoustics Satori TW29R tweeter. I mounted it in a Visaton WG148R waveguide.
The Satori is one of the best tweeters I’ve used. It has very high resolution and great imaging, while still retaining the gentle edge of a soft dome. Transparent and revealing without being excessively analytical.
I chose this tweeter because I didn’t want the sound of a traditional compression driver. The kind of horn one would typically mate this with might easily sound nasal or “shouty” despite whatever EQ magic one might throw at it. I wanted a tweeter that, when mounted in a waveguide, could keep up with the 94dB sensitivity of the woofer and even give an extra +1 or +2dB at the high end.
With its standard faceplate, this tweeter has about 94dB SPL in the 10-20KHz range and a waveguide raises SPL further below 10KHz.
“Lambda” U-Frame Open Baffle
I like using triangular “wings” on the sides of OB speakers to extend bass response. Without wings, these woofers will start rolling off at 120Hz and you’ll get little deep bass. With wings, or U-Frame dipole that is lambda shaped in the side view, the cutoff begins around 65Hz and drops 6dB per octave. The triangle shape keeps the distance from woofer to edge spread across a wide range rather.
I discovered a way to add 4-7dB in the 40-60Hz range so the sound is a little “plump” in the deep bass range. I describe this in the next section.
Passive Bass Boost
This design adds a 5.5dB boost at 45Hz using an unusual passive high pass filter. I can’t be the first person in history to do this, but I’ve never seen this explained or modeled anywhere else. These components are in section “1” of the crossover schematic: a 500uF capacitor and 20mH inductor.
I explain the circuit in section 1 in detail in my post “Open Baffle Bass Boost: +4 to +7dB w/ Passive Xover. No DSP.” I call it the "Marshall Bass Boost." Here you’ll find guidelines and examples for designing your own. It replaces the 25-ohm impedance peak at 41Hz with a 3-ohm dip, drawing almost 4X more power from the amplifier around 45Hz.
This also serves as a subsonic filter, protecting the woofer from signals below 40Hz. Signal falls to -10dB at 30Hz and -17dB at 20Hz. It provides substantial protection from out-of-band signals. Not only do dipoles suffer from rear wave cancellation, they are easily overdriven to large excursions by frequencies you can’t hear. This filter boosts the signal where it matters and cuts it where it doesn’t. The components required for this cost about $40 per channel and are well worth the investment.
Above: Large 20mH inductor and 500uF capacitor boost response at 45Hz.
Drive Signals for Each Driver
In the red curve below you can see the +5.5dB boost at 45Hz as well as the sharp filter.
Above: The signal reaching the Eminence Alpha 15A woofer is in RED. The signal to the SB TW29R tweeter (front) is in GREEN. The signal to the PRV WG230Ti tweeter (rear) is in BLUE.
Woofer crossover (Section 2 in the schematic)
The 1mH inductor, 10-ohm resistor plus LCR notch network in Section 2 of the schematic form a shelf filter with a deep null at 1900Hz. This suppresses the +12dB breakup mode of the Eminence woofer. However, I don't roll off the woofer above that frequency. This is because that would add even more phase shift. I avoid steep crossovers except when absolutely necessary. The woofer is already set back 3-4 inches (7-10cm) behind the plane of the tweeter, so a steep crossover would only make that problem worse.
Above: nearfield measurements of woofer and tweeter and the 1250Hz crossover frequency. The woofer rolls off naturally at 12dB/octave above 3KHz. (See the drive signal to the woofer a few paragraphs above, it heads towards 0dB at high frequencies.) The lack of additional filtering reduces group delay. In my opinion the minimal filtering just sounds better.
Matching Woofer to Tweeter
I’m stretching both drivers to the limits of their range. The 15” woofer start to beam above 1KHz, and the WG148R waveguide stops being directional below 2KHz. So there is a little discontinuity in the radiation pattern between 1-2KHz.
Above: Frequency response at 0, 15, 30, 45, 60, 75 and 90 degrees. Very nearly constant directivity across the band. At about 1500Hz you can see some “bunching” of the radiation pattern, where 30-45 degrees off axis, the output is slightly stronger than on-axis. This would go away if the waveguide was 8” (20cm) diameter instead of 6” (15cm). I chose an off the shelf Visaton waveguide, but a larger 3D printed waveguide would solve this. The bunching at 300Hz is because at this frequency, the radiation pattern is more cardioid than dipole.
Tweeter Crossover
The crossover (Schematic Section 3) for the TW29R is a 24dB/octave filter at 1250Hz. There is no getting around using a steep filter for a 29mm dome tweeter being asked to go so low.
Section 4 of the schematic is an RLC notch filter. It suppresses a minor peak at 3KHz. Some builders might not feel it’s necessary, but this detail erased a last bit of objectionable coloration and leaves the upper midrange silky smooth and just slightly recessed.
The slightly rising response on axis compensates for falling response off axis. When you average the 0, 15, 30, 45 and 60 degree curves together, you get a slightly downward-tilting response, which is my goal for voicing the speakers:
Above: Average of 0, 15, 30, 45 and 60-degree response on the front side of the speakers. Plot also includes 2nd and 3rd harmonic distortion.
Mounting the Satori Tweeter to the Visaton Waveguide
The Satori TW29R tweeter has a not-quite-flat faceplate which doesn’t match the WG148R waveguide. I had to add a bead of modeling clay about 3mm thick in order to fill the gap. You can see the modeling clay in the picture:
Rear Tweeter
The rear tweeter is a PRV WG230Ti. I chose it because it has smooth response and 105db sensitivity so you can easily pad it down to match the front tweeter. I find dipoles sound best when the rear output at high frequencies is a few dB higher than the front output. This adds spaciousness without interfering with detail.
Section 5 of the schematic shows a 7-ohm resistor in series with the PRV tweeter. You can choose any value resistor you wish. This value sounds best to my ears. Below is the rear output:
Above: Rear measurements at 0, 15, 30, 45, 60, 75 and 90 degrees off axis. The system sounds best to my ears when the rear tweeter has a rising response. If you build this system you can play with that resistor and find the value that sounds best to you.
I’m normally a fan of simple crossovers, but due to the multiple conflicting priorities in getting a 2-way passive Dipole speaker to achieve: punchy bass, smooth response, Constant Directivity, high efficiency, high power handling and ultra-transparent high end simultaneously, a price had to be paid. The price was a rather complex crossover. Fortunately it’s the parts count and perfectionistic details that are complex, not the essential concept.
VituixCad files for this design are available here: https://tinyurl.com/walnutdipolesvituix
Areas for Possible Improvement?
A similar woofer with a curvilinear cone instead of straight-sided cone would likely not have the 1.9KHz breakup mode. It would also have wider dispersion above 1KHz and blend with the tweeter better. An 8” / 20cm waveguide would likewise blend better with the woofer. A more pricey version of this system could be executed with the SB Acoustics 15OB350 woofer and the SB Acoustics 29mm Beryllium Waveguide tweeter. (The crossover would have to be completely redesigned. It would still lend itself to the Marshall Bass Boost circuit.)
So… how do they sound?
These speakers throw a HUGE soundstage. They image very well everywhere in the room and have a very transparent and detailed yet silky and not-too-analytical high end. The soft dome tweeters are easy on the ears.
The bass is just slightly on the rich side, and lower midrange is warm and buttery. The overall tone is warm, spacious and detailed with a bit of extra sparkle on the top end. They are equally at home with jazz or rock. ZZ Top sounds terrific. “Burning Down the House” by the Talking Heads is an acid test for bass overload, because the bass drum and percussion parts have a lot of very low frequency energy that easily overloads many woofers, especially in OB and Reflex. The Marshall Bass Boost circuit protects these woofers from bottoming, and they can play quite loud. Bass drums and guitars are authoritative.
There is also a lot to be said for their high efficiency. They are easily 5-6dB more efficient than most audiophile speakers. They’re sensitive enough to use with “flea watt” Single Ended Tube amps.
Generally I like solid state amps better, but I do enjoy playing with tubes. Some speakers just sound better with tubes. These sound outstanding with my Yaqin MC-13L 40W amp, which has much more than enough power to drive these.
They excel with massed voices and percussion. Imaging is both spacious and precise with considerable depth. Instruments have a "bloom" and roundness that you almost never hear from standard box speakers.
My non-audiophile friends who walk in the room have an immediate positive reaction towards their appearance. The Walnut cabinets (made by Seth Cothron @studio38designs) look fantastic.
As Jerry McNutt, president of Eminence Speaker says, “The best way to not sound boxy is to not use a box.”
This is the drawing I gave my carpenter, which he used to build the speakers:
Question regarding SONY 2SK60 and 2SJ18 transistors
Hello all!
Firstly, I would like to apologize if this has been asked numerous times, or if I am in the wrong part of the forums. I am new to the sound world in general.
With that out the way, I would like to ask you guys, how do you know these transistors are genuine, and what are the repercussions of using them if they are not? They are not for me, they are for my grandfather (pics of transistors attached) he has an old TA series SONY amplifier, and his transistors went out many, many years ago. He had a very hard time finding new ones, used ones, or any kind. He does live in Russia, so that may be the case, I am all the way in NYC. None the less, I promised him I'd go on this quest to find what he needs. My travels recently took me to Japan, but walking around Japan's most famous used tech stores and audio stores, I had no luck. Many of the sellers didn't even know what I was talking about, even when I showed them photos. Many just straight up told me these have never entered their shops. I was pretty upset with this, and when I got back to the states, I tried looking online one more time. I found these on eBay. I am pretty sure they are straight from China, the seller reassured me many times that they are in fact genuine and have been tested in the amplifier AND that they can be returned with money back if things don't go as planned. Can any of the members here, who are WAY smarter than me point me into the right direction on how to find out if these will work? Or am I just screwed? either way, thank you for reading!
Firstly, I would like to apologize if this has been asked numerous times, or if I am in the wrong part of the forums. I am new to the sound world in general.
With that out the way, I would like to ask you guys, how do you know these transistors are genuine, and what are the repercussions of using them if they are not? They are not for me, they are for my grandfather (pics of transistors attached) he has an old TA series SONY amplifier, and his transistors went out many, many years ago. He had a very hard time finding new ones, used ones, or any kind. He does live in Russia, so that may be the case, I am all the way in NYC. None the less, I promised him I'd go on this quest to find what he needs. My travels recently took me to Japan, but walking around Japan's most famous used tech stores and audio stores, I had no luck. Many of the sellers didn't even know what I was talking about, even when I showed them photos. Many just straight up told me these have never entered their shops. I was pretty upset with this, and when I got back to the states, I tried looking online one more time. I found these on eBay. I am pretty sure they are straight from China, the seller reassured me many times that they are in fact genuine and have been tested in the amplifier AND that they can be returned with money back if things don't go as planned. Can any of the members here, who are WAY smarter than me point me into the right direction on how to find out if these will work? Or am I just screwed? either way, thank you for reading!
Cerwin Vega 300 SE Crossover problem. What To Test?
- By Superprohero
- Full Range
- 2 Replies
Attachments
Downward Pointing Harmonic Peaks in LT Spice FFT. Is The Design Correct?
- Solid State
- 36 Replies
This is my first design in progress in LT-Spice and rather unconventional one. The key point is the amp does not use the op-amp in any gain stages and is completely BJT based. After improving the gains of input and output CFP stages using a variant of the bootstrapping technique, I am getting 0.000006% THD@1KHz, yes, that's right - 0.06 PPM. (at least in simulation - best case scenario and I am aware that it is almost impossible to achieve in real-life). I will be glad to publish the design here once the amp is built.
The observation is after the above-mentioned gain improvement, 2nd, 4th, 5th and 8th hormonic peaks in the FFT are pointing downwards. My concern at the moment is, does it indicate a flaw in the design? Should they not be pointing upwards? Or because of RMS this can be ignored? Am I using he best practice? Are there any known impact of such traits in the FFT on the sound quality or musicality.
Your Point-of-View is welcome experts and stalwarts. Your views will help me correct the design flaws, if any. Attached is the FFT diagram
The observation is after the above-mentioned gain improvement, 2nd, 4th, 5th and 8th hormonic peaks in the FFT are pointing downwards. My concern at the moment is, does it indicate a flaw in the design? Should they not be pointing upwards? Or because of RMS this can be ignored? Am I using he best practice? Are there any known impact of such traits in the FFT on the sound quality or musicality.
Your Point-of-View is welcome experts and stalwarts. Your views will help me correct the design flaws, if any. Attached is the FFT diagram
Wharfdale MODEL 3014 speakers, are they any good?
- Multi-Way
- 9 Replies
I'm able to get a pair of Wharfdale Model 3014 woofers for 60 dollars.
Is there any problem with putting them in a bass reflex cabinet? Is there any plots available for these?
Is there any problem with putting them in a bass reflex cabinet? Is there any plots available for these?
Attachments
Insight on basic two layer CAD designing please
- By Tone Arcana
- Construction Tips
- 0 Replies
Attachments
Pioneer SA-510 Issue and see photo
- By drocelot
- Solid State
- 2 Replies
Hi All,
Currently diagnosing an issue with SA-510 how do I remove this ribbon cable ?
Currently diagnosing an issue with SA-510 how do I remove this ribbon cable ?
Replacing N channel jFET in Sony Receiver, what is my best option and how close does it need to be?
- By saabracer23
- Solid State
- 8 Replies
I’m having trouble with a Sony STR-6055 MPX board in the tuner which I’ve read is very common with this model. My voltages are pretty far off. I barely touched Q401 and a leg snapped, super thin. It’s a 2SK23, no other info on it, no Idss ranking. I read that 2SK117 is a good fit, but then not because of high ciss/crss.
I saw someone say they replaced this exact Q401 with a 2N4393 with a vgsoff of 1.17v and it’s of 8.45 mA and that it worked well enough. I don’t know what they used to get their measurements.
The device that is in here has a small little nubbin of metal still sticking out of the case that used to be the leg, so I can still measure it with a Peak DCA75. It measures with a vgsoff of 1.71v and a idss of 4.92 mA. Seems a decent way off of what he used. Though this one may be defective and not measuring as it did when new.
Here it is in circuit. It has about 15v on it.
I’m curious if what I have would make a good replacement.
2SK170bl. I only have BL unfortunately, on this same tester they are measuring with an Idss of 6.5ish and up. So would be in line perfectly with what that other person used (2N4393). I have hundreds so would be cool to use.
2SK30A. Idss seems a bit lower in the 3-ish range. I have about 25 or so
2N5457. These have an Idss on the low side, about 2-1/2. Again not very many, maybe 20
2N5458. These seem to be fairly dead on, Idss of around 4-1/2 to 6. Only have 20 so if something else works better that would be nice. Not sure if this is a good fit anyways. Luckily it’s still available so I can buy more.
I also have several smd options I can put on adapter board. For example 2SK209 in Y, GR, and BL.
What are thoughts? Go with what the other person used and use one of the 2SK170s or should I use the 2N5458, or something else? Not sure how close it needs to be.
Thank you,
Dan
I saw someone say they replaced this exact Q401 with a 2N4393 with a vgsoff of 1.17v and it’s of 8.45 mA and that it worked well enough. I don’t know what they used to get their measurements.
The device that is in here has a small little nubbin of metal still sticking out of the case that used to be the leg, so I can still measure it with a Peak DCA75. It measures with a vgsoff of 1.71v and a idss of 4.92 mA. Seems a decent way off of what he used. Though this one may be defective and not measuring as it did when new.
Here it is in circuit. It has about 15v on it.
I’m curious if what I have would make a good replacement.
2SK170bl. I only have BL unfortunately, on this same tester they are measuring with an Idss of 6.5ish and up. So would be in line perfectly with what that other person used (2N4393). I have hundreds so would be cool to use.
2SK30A. Idss seems a bit lower in the 3-ish range. I have about 25 or so
2N5457. These have an Idss on the low side, about 2-1/2. Again not very many, maybe 20
2N5458. These seem to be fairly dead on, Idss of around 4-1/2 to 6. Only have 20 so if something else works better that would be nice. Not sure if this is a good fit anyways. Luckily it’s still available so I can buy more.
I also have several smd options I can put on adapter board. For example 2SK209 in Y, GR, and BL.
What are thoughts? Go with what the other person used and use one of the 2SK170s or should I use the 2N5458, or something else? Not sure how close it needs to be.
Thank you,
Dan