Sony vFET Illustrated build guide
Nelson Pass testing procedure and instructions for DIY Sony Vfet amp -
Print this out!! 🙂
http://www.firstwatt.com/pdf/art_diy_sony_vfet.pdf
Pass DIY Sony Vfet amplifier illustrated build guide.
The Pass DIY Sony Vfet is a power amplifier from the brilliant mind of our technical, spiritual, and menu advisor, Nelson Pass. Quite possibly the most generous design yet, as Nelson released his private stash of the out of production 1970's Vfet to the DIY community so we can build an amp that nobody else can build nor buy. 🙂
How the circuit works
The Front End
The overall schematic of the VFET amp is somewhat complicated in spite of the simple gain path – this is due to the special DC regulation circuits to cater to the fussy VFET transistors in the output stage.
Fortunately the front end voltage gain stage of the amplifier is pretty simple.
The Vfet DIY Front-end is basically a mini-F5. It serves to give us enough voltage and current gain to drive the Vfets so we can wire the Vfet as followers (known as “Common Drain operation, where no voltage gain is acquired, only current).
The input signal starts at R1 (2,2K), which acts as a “gate-stopper” resistor for the input Jfets, as well as a current limiter in case the attached preamp has a big turn-on or -off thump. R2, (47K) is from the input of the Jfet to ground, this gives the Jfet gates a reference to ground, and also sets the input impedance, which is about 50K.
The signal goes through the Jfets (Q1,2) and the gain currents at their Drain outputs go through the cascode transistors (Q3,4) and then to drive the Gates of the voltage amplification (Vas) Mosfets (Q5,6). The cascode transistors, Q3 and Q4, act as a voltage umbrellas, protecting the Jfets from the voltages appearing at T11 and T13 so that their Drains experience a fraction of the DC and AC voltage T11 and T13 as determined by R7, R9 and R8, R10 driving Q3 and Q4.
To quote Mr. Pass, “Cascoding is a very useful technique where the gain transistor (in this case each of the Jfets) is coupled to another transistor operated in Common-Gate or Common-Base mode. This cascode transistor contributes very little of its own characteristic to the amplification, but it acts like a voltage umbrella, shielding the gain transistor from the high DC voltage and noise of the power supply rails.”
The Drain pins of Q5 and Q6 deliver the output voltage (but not enough current) to drive loudspeakers. This point is found at test node T18.
Mosfet Q5 and Q6 need some voltage applied to their gates in order to turn on (bias) and amplify signal, and this is provided by the voltage appearing across R35 + P3 and R34 +P4. P3 and P4 are there to adjust this voltage so as to set the right amount of current through Q4 and Q6. This right amount of current is defined by 1.5 V DC appearing across resistors R5 and R6 AND the output of the front end (T18) near 0 volts DC. So P3 and P4 not only adjust the idle current through the voltage gain transistors Q5 and Q6, but they also set the DC output that appears on their Drain pins.
Adjusting the Front End bias
Bias is set by measuring the DC voltage across R5, (test nodes T6-T7), and R6 (test nodes T8-T9). Proper bias is when you have 1.5V across each of these resistors, at the same time also having 0 volts DC offset, which is the voltage at T18 to GND.
Adjusting P3 and P4 will make changes in all three of those readings, so in my opinion, you must have three DC voltmeters to make this an easy job. Even the very inexpensive Chinese DMM will work fine for this, just make sure they have good, fresh batteries in them.
A single voltmeter will do that job, but it is more tedious. In any case you want to adjust each pot in small steps, going between the pots and voltage measurements in rotation.
You start with both potentiometers at full counterclockwise, which is the lowest bias setting. At first you are simply looking to get the voltages across R5 and R6 up to 1.5 in small steps. You turn P3 just a little bit, measuring a small change across R5, and then you do the same for P4 and R6. And then you go back to P3/R6 and repeat this process, raising the DC voltages slowly and in equal amounts.
You also want to check the DC voltage from T18 to ground as you do this – you want to keep it near 0V if possible.
I suggest you pause at around 1 V on R5 and R6 – as the Mosfets heat up, the current will rise on its own. Eventually you will find yourself with “warm” settings which give about 1.5V DC bias and close to 0 V DC output at T18.
How good is good enough? 1.3 V to 1.7V is OK for bias. +/-200 mV is good enough for offset at this point. We will tweak these values after the completed amplifier has run for a bit.
REMEMBER – BABY STEPS ON ALL ADJUSTMENTS.
If for some reason you can’t achieve full bias with zero offset, please troubleshoot in the build guide thread, and do tell us how much bias you can get with zero offset.
Please refer to the above schematic for component names
The output stage -
The Vfets themselves are wired as a complementary pair in source-follower mode. These add current gain to the signal sent to their Gate pins (to be able to drive speakers with a low output impedance) but have no voltage gain.
That’s it - the voltage gain has happened in the Front-End, and the Vfets just add current capability. 🙂 But it’s not quite that simple… is it?
Well, it actually is, until you realize that the DC powering up the Vfets must be regulated for a stable DC voltage and low noise, the same with the bias voltage. Also, both the rail voltage and the bias voltage have to power-up and power-down in a specific order to keep the Vfets from trying to draw a ton of current when the circuit is powered up.
What’s the proof of Nelson’s genius in this circuit? In how simple (and quite effective) the regulator sections have been designed. Let’s talk about that now.
Regulators
Each rail of each channel has 2 regulators, for a total of 4. Each of the two rails has a bias regulator and an output stage regulator. For clarity’s sake, I’m now going to talk about the positive rail’s regs - the negative rails have the same thing, just in a mirror image.
Both regulators use a TL431, a nice little 3-pin shunt reg that can have it’s output voltage set by 2 resistors. Looking at the schematic around Q11, you can see the unregulated voltage coming from the rail through a simple RC filter (R29 and C7) then through R13 (2.21K) and then the set resistors R11 (10K) and P1 (5K pot).
Because one of the two set resistors is a potentiometer wired as a variable resistor, changing that pot value changes the set voltage which provides Vfet voltage bias. It is very important that the bias voltage is place when power is applied to the Drain of the VFET, so this regulator circuit (bias reg) is designed to charge up much faster than the regulated voltage powering the Drain. (The output stage regulator)
Remember how it was mentioned earlier that the Sony Vfets are “Depletion” mode? They are normally on, letting current flow, and require a negative voltage applied to the gate to turn them off (this for the N type – The P channel devices require a positive voltage), or to otherwise set the value of the current (bias) through the VFET.
Looking at the regulated voltage at T19, (+14V) you want to note that it crosses over and connects to the gate of the negative P-channel Vfet Q10. The positive N-channel Vfet Q9, is likewise biased from the opposite rail. This is the opposite of what you are normally going to see with complementary Mosfet followers.
Moving on to the output regulators, you can see the circuitry near Q13 looks similar to the other reg, the exception being the voltage setting resistors are both fixed resistors. (R15, R17) These resistors and the TL431 make a voltage of 24V, seen at T2. This fixed voltage is controls the gate of a power Mosfet, Q7. This Mosfet is slaved to the regulator and lets the tiny TO-92 package regulator control many amps of current. Wonderful! This is necessary because the regulator needs to regulate the power going to the output stage which drives your speakers.
However there is no free lunch, and the Mosfet eats up about 4.2V (the Mosfet’s Vgs) in payment for doing it’s job. This is why you see a regulated rail voltage presented to the drains of the*Vfets of 19.8V (or so). An important part of the rail regulators is C1 (220uF), there to delay the arrival of this 19.8V to give the bias regulator time to ramp up. More about this here;
Power-up and power-down sequencing.
Back to depletion mode devices - The Vfets are normally on, right? We need to apply a bias voltage to control them. If the bias voltage isn’t there controlling current flow when the rail regulators power up, the Vfets will conduct an excessive amount of current and the 40-year old, completely irreplaceable smoke made from vintage Japanese un-obtainium, ground unicorn horn and pixie dust will escape. A sad result which will also smell bad.
So we must have the bias regulator working before the rail voltage is turned on. How did Nelson do it? A simple application of the time constant to charge 2 differently sized capacitors in the regulator circuits. The regulator with the smaller capacitor will turn on before the one with the larger cap. These caps in the race are C3 (47uF) on the bias reg and C1 (220uF) on the output regulator. It’s a 4.7-to-1 ratio and C3 will be charged about 4.7 times sooner.
The TL431 are shunt regulators, so they do not conduct current until the voltage rises to the regulation value, and then they conduct so as to hold that value.
So what about power down? The rail voltage needs to be turned off before the bias voltage. (the opposite of power-up) BUT, the big cap/small cap ratio will NOT work in our favor when shutting down. It would work exactly how you’d expect, where the small cap will discharge before the big one.
So what? The VFETs will drain the supply quickly enough, but when the supply voltage drops down quickly we may find the Gate to Source voltage (Vgs) of the Mosfet at a high enough voltage to stress the transistor into failure. It's not that likely, but everyone knows that Pass wears both a belt and suspenders to hold up his pants, and this is reflected in his design.
The fix is a simple 2-cent diode. On power down, D1 will be a very attractive and very low-resistance discharge path for C1, discharging it rapidly and turning Q7 (and Q13) off, and therefore the rail voltage to the Vfets. Because there is no special path for C3 in the bias regulator to discharge, it will operate for a longer time, which is perfectly ok.
The stuff in the middle.
Ok, so far everything has been explained except for the wiggles in the center of the schematic near T16 and T17. Remember how the bias voltage regulator is set by the divider made from R11 and P1? This is a DC value but we also need to let the AC have it’s say in the circuit, as the AC is our music. 🙂 The Front-End output signal was all big and powerful the last time we left it at T18. Now this signal needs to get to the Gates of the Vfets to move our speakers, and that signal (even though it’s AC) can get pretty darn big. Big enough that it’s voltage could effect the current flowing through the regulator set resistors. The network of C5, C6 and R21 through R24 prevent the music signal from having much influence on the bias regulators. Stable bias makes for happy Vfets, so this is a good thing.
What’s left… Um… R25 R26 (221ohm) are gatestoppers for the Vfet, R33 (22.1K) adjusts the brightness of the LED (which must be blue, this is a Pass amp, after all…) and R32 (0.1ohm) gives a place to measure the output stage current. (Bias)
Global feedback is applied from the output stage from the Vfets to the Jfets through R3 (2.21K), and then R4 (332ohm) to ground.
Cool! That's the basic overview of how it works. Let's build!!
😀 😀 😀
.
Print this out!! 🙂
http://www.firstwatt.com/pdf/art_diy_sony_vfet.pdf
Pass DIY Sony Vfet amplifier illustrated build guide.
The Pass DIY Sony Vfet is a power amplifier from the brilliant mind of our technical, spiritual, and menu advisor, Nelson Pass. Quite possibly the most generous design yet, as Nelson released his private stash of the out of production 1970's Vfet to the DIY community so we can build an amp that nobody else can build nor buy. 🙂
How the circuit works
The Front End
The overall schematic of the VFET amp is somewhat complicated in spite of the simple gain path – this is due to the special DC regulation circuits to cater to the fussy VFET transistors in the output stage.
Fortunately the front end voltage gain stage of the amplifier is pretty simple.
The Vfet DIY Front-end is basically a mini-F5. It serves to give us enough voltage and current gain to drive the Vfets so we can wire the Vfet as followers (known as “Common Drain operation, where no voltage gain is acquired, only current).
The input signal starts at R1 (2,2K), which acts as a “gate-stopper” resistor for the input Jfets, as well as a current limiter in case the attached preamp has a big turn-on or -off thump. R2, (47K) is from the input of the Jfet to ground, this gives the Jfet gates a reference to ground, and also sets the input impedance, which is about 50K.
The signal goes through the Jfets (Q1,2) and the gain currents at their Drain outputs go through the cascode transistors (Q3,4) and then to drive the Gates of the voltage amplification (Vas) Mosfets (Q5,6). The cascode transistors, Q3 and Q4, act as a voltage umbrellas, protecting the Jfets from the voltages appearing at T11 and T13 so that their Drains experience a fraction of the DC and AC voltage T11 and T13 as determined by R7, R9 and R8, R10 driving Q3 and Q4.
To quote Mr. Pass, “Cascoding is a very useful technique where the gain transistor (in this case each of the Jfets) is coupled to another transistor operated in Common-Gate or Common-Base mode. This cascode transistor contributes very little of its own characteristic to the amplification, but it acts like a voltage umbrella, shielding the gain transistor from the high DC voltage and noise of the power supply rails.”
The Drain pins of Q5 and Q6 deliver the output voltage (but not enough current) to drive loudspeakers. This point is found at test node T18.
Mosfet Q5 and Q6 need some voltage applied to their gates in order to turn on (bias) and amplify signal, and this is provided by the voltage appearing across R35 + P3 and R34 +P4. P3 and P4 are there to adjust this voltage so as to set the right amount of current through Q4 and Q6. This right amount of current is defined by 1.5 V DC appearing across resistors R5 and R6 AND the output of the front end (T18) near 0 volts DC. So P3 and P4 not only adjust the idle current through the voltage gain transistors Q5 and Q6, but they also set the DC output that appears on their Drain pins.
Adjusting the Front End bias
Bias is set by measuring the DC voltage across R5, (test nodes T6-T7), and R6 (test nodes T8-T9). Proper bias is when you have 1.5V across each of these resistors, at the same time also having 0 volts DC offset, which is the voltage at T18 to GND.
Adjusting P3 and P4 will make changes in all three of those readings, so in my opinion, you must have three DC voltmeters to make this an easy job. Even the very inexpensive Chinese DMM will work fine for this, just make sure they have good, fresh batteries in them.
A single voltmeter will do that job, but it is more tedious. In any case you want to adjust each pot in small steps, going between the pots and voltage measurements in rotation.
You start with both potentiometers at full counterclockwise, which is the lowest bias setting. At first you are simply looking to get the voltages across R5 and R6 up to 1.5 in small steps. You turn P3 just a little bit, measuring a small change across R5, and then you do the same for P4 and R6. And then you go back to P3/R6 and repeat this process, raising the DC voltages slowly and in equal amounts.
You also want to check the DC voltage from T18 to ground as you do this – you want to keep it near 0V if possible.
I suggest you pause at around 1 V on R5 and R6 – as the Mosfets heat up, the current will rise on its own. Eventually you will find yourself with “warm” settings which give about 1.5V DC bias and close to 0 V DC output at T18.
How good is good enough? 1.3 V to 1.7V is OK for bias. +/-200 mV is good enough for offset at this point. We will tweak these values after the completed amplifier has run for a bit.
REMEMBER – BABY STEPS ON ALL ADJUSTMENTS.
If for some reason you can’t achieve full bias with zero offset, please troubleshoot in the build guide thread, and do tell us how much bias you can get with zero offset.
Please refer to the above schematic for component names
The output stage -
The Vfets themselves are wired as a complementary pair in source-follower mode. These add current gain to the signal sent to their Gate pins (to be able to drive speakers with a low output impedance) but have no voltage gain.
That’s it - the voltage gain has happened in the Front-End, and the Vfets just add current capability. 🙂 But it’s not quite that simple… is it?
Well, it actually is, until you realize that the DC powering up the Vfets must be regulated for a stable DC voltage and low noise, the same with the bias voltage. Also, both the rail voltage and the bias voltage have to power-up and power-down in a specific order to keep the Vfets from trying to draw a ton of current when the circuit is powered up.
What’s the proof of Nelson’s genius in this circuit? In how simple (and quite effective) the regulator sections have been designed. Let’s talk about that now.
Regulators
Each rail of each channel has 2 regulators, for a total of 4. Each of the two rails has a bias regulator and an output stage regulator. For clarity’s sake, I’m now going to talk about the positive rail’s regs - the negative rails have the same thing, just in a mirror image.
Both regulators use a TL431, a nice little 3-pin shunt reg that can have it’s output voltage set by 2 resistors. Looking at the schematic around Q11, you can see the unregulated voltage coming from the rail through a simple RC filter (R29 and C7) then through R13 (2.21K) and then the set resistors R11 (10K) and P1 (5K pot).
Because one of the two set resistors is a potentiometer wired as a variable resistor, changing that pot value changes the set voltage which provides Vfet voltage bias. It is very important that the bias voltage is place when power is applied to the Drain of the VFET, so this regulator circuit (bias reg) is designed to charge up much faster than the regulated voltage powering the Drain. (The output stage regulator)
Remember how it was mentioned earlier that the Sony Vfets are “Depletion” mode? They are normally on, letting current flow, and require a negative voltage applied to the gate to turn them off (this for the N type – The P channel devices require a positive voltage), or to otherwise set the value of the current (bias) through the VFET.
Looking at the regulated voltage at T19, (+14V) you want to note that it crosses over and connects to the gate of the negative P-channel Vfet Q10. The positive N-channel Vfet Q9, is likewise biased from the opposite rail. This is the opposite of what you are normally going to see with complementary Mosfet followers.
Moving on to the output regulators, you can see the circuitry near Q13 looks similar to the other reg, the exception being the voltage setting resistors are both fixed resistors. (R15, R17) These resistors and the TL431 make a voltage of 24V, seen at T2. This fixed voltage is controls the gate of a power Mosfet, Q7. This Mosfet is slaved to the regulator and lets the tiny TO-92 package regulator control many amps of current. Wonderful! This is necessary because the regulator needs to regulate the power going to the output stage which drives your speakers.
However there is no free lunch, and the Mosfet eats up about 4.2V (the Mosfet’s Vgs) in payment for doing it’s job. This is why you see a regulated rail voltage presented to the drains of the*Vfets of 19.8V (or so). An important part of the rail regulators is C1 (220uF), there to delay the arrival of this 19.8V to give the bias regulator time to ramp up. More about this here;
Power-up and power-down sequencing.
Back to depletion mode devices - The Vfets are normally on, right? We need to apply a bias voltage to control them. If the bias voltage isn’t there controlling current flow when the rail regulators power up, the Vfets will conduct an excessive amount of current and the 40-year old, completely irreplaceable smoke made from vintage Japanese un-obtainium, ground unicorn horn and pixie dust will escape. A sad result which will also smell bad.
So we must have the bias regulator working before the rail voltage is turned on. How did Nelson do it? A simple application of the time constant to charge 2 differently sized capacitors in the regulator circuits. The regulator with the smaller capacitor will turn on before the one with the larger cap. These caps in the race are C3 (47uF) on the bias reg and C1 (220uF) on the output regulator. It’s a 4.7-to-1 ratio and C3 will be charged about 4.7 times sooner.
The TL431 are shunt regulators, so they do not conduct current until the voltage rises to the regulation value, and then they conduct so as to hold that value.
So what about power down? The rail voltage needs to be turned off before the bias voltage. (the opposite of power-up) BUT, the big cap/small cap ratio will NOT work in our favor when shutting down. It would work exactly how you’d expect, where the small cap will discharge before the big one.
So what? The VFETs will drain the supply quickly enough, but when the supply voltage drops down quickly we may find the Gate to Source voltage (Vgs) of the Mosfet at a high enough voltage to stress the transistor into failure. It's not that likely, but everyone knows that Pass wears both a belt and suspenders to hold up his pants, and this is reflected in his design.
The fix is a simple 2-cent diode. On power down, D1 will be a very attractive and very low-resistance discharge path for C1, discharging it rapidly and turning Q7 (and Q13) off, and therefore the rail voltage to the Vfets. Because there is no special path for C3 in the bias regulator to discharge, it will operate for a longer time, which is perfectly ok.
The stuff in the middle.
Ok, so far everything has been explained except for the wiggles in the center of the schematic near T16 and T17. Remember how the bias voltage regulator is set by the divider made from R11 and P1? This is a DC value but we also need to let the AC have it’s say in the circuit, as the AC is our music. 🙂 The Front-End output signal was all big and powerful the last time we left it at T18. Now this signal needs to get to the Gates of the Vfets to move our speakers, and that signal (even though it’s AC) can get pretty darn big. Big enough that it’s voltage could effect the current flowing through the regulator set resistors. The network of C5, C6 and R21 through R24 prevent the music signal from having much influence on the bias regulators. Stable bias makes for happy Vfets, so this is a good thing.
What’s left… Um… R25 R26 (221ohm) are gatestoppers for the Vfet, R33 (22.1K) adjusts the brightness of the LED (which must be blue, this is a Pass amp, after all…) and R32 (0.1ohm) gives a place to measure the output stage current. (Bias)
Global feedback is applied from the output stage from the Vfets to the Jfets through R3 (2.21K), and then R4 (332ohm) to ground.
Cool! That's the basic overview of how it works. Let's build!!
😀 😀 😀
.
Discrete opamp with zero input bias current
- By lineup
- Solid State
- 3 Replies
It is possible to compensate so the input current becomes zero.
I don't really know what this should be good for.
At least there is one capacitor less 😀
This circuit simulates THD 0.000062% at 1Vrms into 1kOhm.
I don't really know what this should be good for.
At least there is one capacitor less 😀
This circuit simulates THD 0.000062% at 1Vrms into 1kOhm.
Sansui AU-D9 – Power transistors not amplifying after restoration
- By GESMAN
- Solid State
- 44 Replies
Attachments
ADSP21489 + 2in / 8out PCM1798 board
- By khoidang1107
- Introductions
- 1 Replies
Hello everyone, can anyone help me with the DP48X driver and FIR48 firmware? I also don't know if my board is version 1.0 or 2.0. I hope everyone can help me. Thanks for reading.
DIY stiffening cone techniques - How to
- By Freedom666
- Construction Tips
- 38 Replies
How to DIY making a paper cone (or others) more stiff.
Here first example:
fast drying hairspray liquid
Never apply too much at once so the paper fibers do not become wet and weak and throw wrinkles!
Better less but several times applying
then if possible fast dry in the sun
Here first example:
fast drying hairspray liquid
Never apply too much at once so the paper fibers do not become wet and weak and throw wrinkles!
Better less but several times applying
then if possible fast dry in the sun
Building stands for a pair of Monitor Audio r352 speakers
- By B O A B
- Construction Tips
- 3 Replies
Hello,
I recently picked up a pair of Monitor Audio r352 speakers of eBay, but they didn't come with any stands. I like the look of the stands that came with these back in the day (see the attached photo), but I can't find any information about them online. I reached out to a couple of eBay sellers who were selling the speakers with stands, but their either didn't reply, or couldn't help. I even reached out to Monitor Audio, who after a while got back to me to say they also had no information in the archive, nor did they have a pair in storage.
It's a long shot I know, but I don't suppose anyone on here has a pair of the stands and could supply me with the relevant measurements...?
If not, can anyone recommend some rules of thumb, around the size and thickness of both the base plate and column? The base of the speaker cabinets have captive nuts, so I guess the top plate size if pretty much self explanatory. The only other thing I really need is some for some guidance over the angle the speaker sits at.
Any construction tips for stands? Is it simply a case of screwing the column to both plates and calling it done? Or is there a better way of joining everything to help dissipate, or mitigate, vibrations coming up from the floor?
Any help would be much appreciated.
I recently picked up a pair of Monitor Audio r352 speakers of eBay, but they didn't come with any stands. I like the look of the stands that came with these back in the day (see the attached photo), but I can't find any information about them online. I reached out to a couple of eBay sellers who were selling the speakers with stands, but their either didn't reply, or couldn't help. I even reached out to Monitor Audio, who after a while got back to me to say they also had no information in the archive, nor did they have a pair in storage.
It's a long shot I know, but I don't suppose anyone on here has a pair of the stands and could supply me with the relevant measurements...?
If not, can anyone recommend some rules of thumb, around the size and thickness of both the base plate and column? The base of the speaker cabinets have captive nuts, so I guess the top plate size if pretty much self explanatory. The only other thing I really need is some for some guidance over the angle the speaker sits at.
Any construction tips for stands? Is it simply a case of screwing the column to both plates and calling it done? Or is there a better way of joining everything to help dissipate, or mitigate, vibrations coming up from the floor?
Any help would be much appreciated.
ICEpower 1000A help to identify parts missing
- By hunter audio
- Class D
- 13 Replies
Hi All
Please help to identify the parts marked in the Ice Power 1000a module picture they are adjacent to the input connector. I have 2 modules one the parts have unfortunately come off and got lost in transit and one module with the parts populated. Most of the components are marked and identifiable, somehow the parts that went missing are not marked.
Below is the module with the parts missing in blue
Below is a picture of the module that is with all the components.
Thanks.
Please help to identify the parts marked in the Ice Power 1000a module picture they are adjacent to the input connector. I have 2 modules one the parts have unfortunately come off and got lost in transit and one module with the parts populated. Most of the components are marked and identifiable, somehow the parts that went missing are not marked.
Below is the module with the parts missing in blue
Below is a picture of the module that is with all the components.
Thanks.
"Pangolins", a Dayton 10" 2.5way...
- By wolf_teeth
- Multi-Way
- 26 Replies
Attachments
-
PangolinsFinalC0deg.png -
PangolinsFinalC0degHD.png -
PangolinsFinalCOffAxes0-60.png -
PangolinBox.png -
PangolinsBoxDrawing.png -
PangolinXmax.png -
Dayton RST28F-4_1Mod.jpg -
Dayton RST28F-4_2Mod.jpg -
Mod1HD.jpg -
Mod2HD.jpg -
RSTcup.png -
2ndtuningdiscCab1withCoil.png -
2ndtuningdiscCab2withCoil.png -
Pangolin_2pt5-2pt0_8pt2-52ohm-0.7-notch_OnTweeterAxis_halfmeter.png -
PangolinCab1-RST28FMod-OnAxis.png -
PangolinCab1-SD270A88-OnTweeterAxis.png -
PangolinCab1-SD270A88-OnTweeterAxisHD.png -
PangolinCab2-SD270A88-OnTweeterAxisHD.png -
fgb0td6ca5sd.jpg -
Pangolins_D_AbsolutelyFinalXover.png
Current feedback Mosfet Circlotron
- By UltimateX86
- Solid State
- 267 Replies
Current feedback Mosfet Circlotron : it's alive !
Hi,
I present you the amp that I just realized.
This is a current feedback Mosfet Circlotron
Without Diyaudio forum and another French, this amp could never be created.
So thank you all the people who helped me and especially Joe Berry who gave me the Keystone of this amp, the current generator so particular that guarantee a thermal stability
A special thanks to gionag, my friend Rabbi Michele, who is the first to have made this amp and who made this great layout
YouTube : low cost phone record... but it's alive !
in real R15=500, R14=220, C3-C4= 47p
YouTube : low cost phone record... but it's alive !
Hi,
I present you the amp that I just realized.
This is a current feedback Mosfet Circlotron
Without Diyaudio forum and another French, this amp could never be created.
So thank you all the people who helped me and especially Joe Berry who gave me the Keystone of this amp, the current generator so particular that guarantee a thermal stability A special thanks to gionag, my friend Rabbi Michele, who is the first to have made this amp and who made this great layout YouTube : low cost phone record... but it's alive !
in real R15=500, R14=220, C3-C4= 47p
YouTube : low cost phone record... but it's alive !
For Sale GZLOZone preamp
For sale is a GZLOZone PRT-01A populated preamp board with tubes and power transformer for sale. Just add RCA jacks and volume pot. I don't have any technical info as this was given to me by a friend. I will ship to you for $30 including shipping, most likely USPS priority mail flat rate box, CONUS only.
modeling a loudspeaker using transfer matrices
- By parallelpen
- Software Tools
- 12 Replies
Hi everyone,
I am trying to make my own simulating tool using GNU Octave and transfer matrices methode. I am encountering difficulties in validating my simple model (infinite baffle) because it does not match hornresp results. i think i am not that far from a correct model but not here yet. as you can see phase and SPL are not the same as hornresp.
below is the code with some comments. Note that i do not think problem come from my radiatoin impedance since i used this function for analytical modeling and results mached hornresp with my analytical model.
I am trying to make my own simulating tool using GNU Octave and transfer matrices methode. I am encountering difficulties in validating my simple model (infinite baffle) because it does not match hornresp results. i think i am not that far from a correct model but not here yet. as you can see phase and SPL are not the same as hornresp.
below is the code with some comments. Note that i do not think problem come from my radiatoin impedance since i used this function for analytical modeling and results mached hornresp with my analytical model.
Code:
clear all; close all; clc;
[c, rho, P, P_ref, Air_Imp, f, w] = Generals(); % initialise constantes and frequenies
wc = w / c; % wave number
driver = 'RCF_MB15N405.csv'; % Selecting driver
r = 1; % Distance to from the source
eg = 2.83; % Input voltage
% Thiele/Small parameters
[Sd, fs, Vas, Qms, Bl, Re, Le, Xmax, Mms, Qts, Qes, Rms, n, dr] = TS_extract(driver, 1);
Cms = Vas / (rho * c^2 * Sd^2) % Calculating mechanical compliance
Pg=eg*Bl/(Sd*Re);
mas=rho*Sd;
% Radiation impedance uing bessel and struve functions choose
[zar,zmr]=RadImpC(Sd);
% Loop for each frequency
for k = 1:length(w)
% Transfer matrices for sub domains
tre(:, :, k) = [1, Re; 0, 1]; % voice coil resistance
tle(:, :, k) = [1, 1i*w(k)*Le; 0, 1]; % Inductance
tem(:, :, k) = [0, Bl; 1/Bl, 0]; % gyrator
tmm(:, :, k) = [1, 1i*w(k)*Mms; 0, 1]; % Mobil mass
tcm(:, :, k) = [1, 1/(1i*w(k)*Cms); 0, 1]; % Compliance
trm(:, :, k) = [1, Rms; 0, 1]; % mechanic losses
% Electromechanic chain
tdr(:, :, k) = tre(:, :, k) * tem(:, :, k) * tmm(:, :, k) * tcm(:, :, k) * trm(:, :, k);
% Calculating Iin [A] electrical current from the source from electro-mechanic
% matrix [A,B ; C,D]
t12 = tdr(1,2,k); % A
t22 = tdr(2,2,k); % B
zin = t12 / t22; % Impedance seen from source
ein = eg; % Input voltage
iin = ein / zin; % Input current
In = [ein; iin];
% Acoustic domain
tma(:, :, k) = [Sd, 0; 0, 1/Sd]; % Tranformer
tza(:, :, k) = [1, zar(k); 0, 1]; % Radiation Impedance
% Complete chain from eletrical domain to acoustical domain
Tt(:, :, k) = tre(:, :, k) * tem(:, :, k) * tmm(:, :, k) * tcm(:, :, k) * trm(:, :, k) * tma(:, :, k) * tza(:, :, k);
Ttinv = inv(Tt(:, :, k)); % Inverting matrix
Pu = Ttinv * In; % Calculating results
% Pression (pout) et vitesse acoustique (uout)
pout(k) = Pu(1); % Acoustic pressure at Sd
uout(k) = Pu(2); % Acoustic volume velocity
end
Pa = pout ./ (4 * pi * r); % Acoustic pressure at 1 [m] from the Sd
SPL = 20 * log10(abs(Pa)/ 20e-6); % Decibel SPL
G=1i.*w.*mas.*uout./Pg; % system gain
Phase_deg = unwrap(angle(G)) * 180/pi; % Phase
[fh,o,ph]=hornrespcsv("ibn4050.csv");
figure(1)
semilogx(f, SPL, 'LineWidth', 1.5, fh,o,'LineWidth',1.5);
xlabel('Frequencies (Hz)');
ylabel('SPL');
title(['SPL response']);
grid on;
figure(2)
semilogx(f, Phase_deg, 'LineWidth', 1.5,fh,ph,'LineWidth', 1.5);
xlabel('Frequencies (Hz)');
ylabel('Phase');
title(['Phase']);
grid on;
For Sale 2 pairs of line output transformers Lundahl LL1517
- By Groundloops
- Swap Meet
- 2 Replies
For sale 2 pairs of line output transformers Lundahl ll1517. Tested, fully working.
€75,00 per pair or €130,00 for both pairs.
€75,00 per pair or €130,00 for both pairs.
For Sale 1 pair of SB Acoustics Satori MW16P-4 mid-woofers (Europe)
- By Groundloops
- Swap Meet
- 3 Replies
1 pair of SB Acoustics Satori MW16P-4 mid-woofers. Used, working perfectly, never operated louder than 90 db/1m.
Make a fair offer ...
Make a fair offer ...
Ground control
- By davidbem
- Solid State
- 17 Replies
I have some ground control problems, but not Space Oddity of David Bowie. That can be a nice song in the background while reading this.
This is not my first amplifier build, so I have some knowledge and have had and solved some ground problems in the past, but this one is killing me.
First picture of amplifier layout:
Normally I build dual transformer/dual psu units. This time I decided to reduce cost and used one 600VA toroid. I have tried some different layouts of wiring, but same result.
1. With nothing connected to inputs the amplifier is absolutely silent.
2. With inputs connected together with cable - each to other, the amplifier is absolutelly silent
3. With inputs connected to source there is noise - bzzzzz. Source is Marantz amplifier with preouts - no issues with other amps.
I tried to change grounds from connector to just one point, a screw in the picture on top of capacitors, same problem.
Tried ground lift with greatz, same problem.
The solving of problem was removing the connection from common ground (the green yellow) to the eart point on top near the big resistor, where the chasis is grounded. You can see now the wire on top of the screw of common ground. If I connect this to chasis earthing point there is noise. On other amplifiers, without this wire I had noise, with this one the oposite.
What is the cause of this and can I just leave it like this. The chasis is grounded to the mains jack, but the amplifier 0V -ground is NOT.
This is not my first amplifier build, so I have some knowledge and have had and solved some ground problems in the past, but this one is killing me.
First picture of amplifier layout:
Normally I build dual transformer/dual psu units. This time I decided to reduce cost and used one 600VA toroid. I have tried some different layouts of wiring, but same result.
1. With nothing connected to inputs the amplifier is absolutely silent.
2. With inputs connected together with cable - each to other, the amplifier is absolutelly silent
3. With inputs connected to source there is noise - bzzzzz. Source is Marantz amplifier with preouts - no issues with other amps.
I tried to change grounds from connector to just one point, a screw in the picture on top of capacitors, same problem.
Tried ground lift with greatz, same problem.
The solving of problem was removing the connection from common ground (the green yellow) to the eart point on top near the big resistor, where the chasis is grounded. You can see now the wire on top of the screw of common ground. If I connect this to chasis earthing point there is noise. On other amplifiers, without this wire I had noise, with this one the oposite.
What is the cause of this and can I just leave it like this. The chasis is grounded to the mains jack, but the amplifier 0V -ground is NOT.
Attachments
For Sale Passive preamplifier. Relay attenuator.
Selling a preamplifier (passive). Control via encoder or remote control.
Four inputs and one output.
A logarithmic attenuator is used as a volume control.
Attenuation -96 dB, adjustment step 1.5 dB, option on Vishay 1% resistors, FUJITSU relay.
A 32 * 8 LED matrix is used for the display.
After switching off, all pre positions (channel, volume) are remembered.
The amplifier has an absolutely neutral sound.
Display brightness adjustment and the ability to completely turn off.
Remote control included. Price $300 plus shipping.
Four inputs and one output.
A logarithmic attenuator is used as a volume control.
Attenuation -96 dB, adjustment step 1.5 dB, option on Vishay 1% resistors, FUJITSU relay.
A 32 * 8 LED matrix is used for the display.
After switching off, all pre positions (channel, volume) are remembered.
The amplifier has an absolutely neutral sound.
Display brightness adjustment and the ability to completely turn off.
Remote control included. Price $300 plus shipping.
Volume Control Relay Attenuator passive preamp
- By serglobo
- Vendor's Bazaar
- 46 Replies
A stepwise volume control is implemented with a set of tiny relays and resistors. In a high-end audio system, a noticable sound improvement over potentiomeneters is obtained, also compared to 'audio grade' potentiometers. Its IR remote control provides convenience over solutions with stepped attenuator rotary switches. The sealed relays will maintain contact quality over a practically endless lifetime. The design represents a audio 'preamplifier' of top-class sonic quality, in a compact and affordable implementation.
The design uses high quality Fujitsu FTR-B4CB4.5Z bistable relays, as well as mil-grade audio grade resistors RN55D, RLR07, CMF55 from Vishay-Dale, which have an excellent reputation in the audio field. The circuit is designed for high-quality audio applications.
The input impedance is constant 10K, 22K, 50K, 100K.
The 1.5 dB adjustment step covers a sound attenuation range of 94.7 dB, 63 steps. By eliminating any active electronics, a very clear and open sound is maintained. There are no clicks when adjusting the volume in the speakers. Encoder for control from the panel.
The IR receiver allows remote control. When the power is turned off, the last volume position is remembered.
The circuit operates from a stabilized voltage source of 5 V.
The input impedance is constant 10K, 22K, 50K, 100K.
Payment is possible via Payoneer or to a bank card. It is also possible to buy on Ebay.
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/267166457170
https://sgaudioua.etsy.com/listing/1798144856
https://sgaudioua.etsy.com/listing/1871270901
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo channels
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/267166457170
https://www.ebay.com/itm/266863103276
https://www.ebay.com/itm/266932731942
https://www.ebay.com/itm/267151831175
Stereo controller kit XLR (2 channels XLR), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo XLR channels
https://www.ebay.com/itm/267197617946
https://sgaudioua.etsy.com/listing/1824028825
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/266918250389
https://www.ebay.com/itm/266936692441
Stereo controller kit (8 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/266863035366
Stereo controller kit (6 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
The design uses high quality Fujitsu FTR-B4CB4.5Z bistable relays, as well as mil-grade audio grade resistors RN55D, RLR07, CMF55 from Vishay-Dale, which have an excellent reputation in the audio field. The circuit is designed for high-quality audio applications.
The input impedance is constant 10K, 22K, 50K, 100K.
The 1.5 dB adjustment step covers a sound attenuation range of 94.7 dB, 63 steps. By eliminating any active electronics, a very clear and open sound is maintained. There are no clicks when adjusting the volume in the speakers. Encoder for control from the panel.
The IR receiver allows remote control. When the power is turned off, the last volume position is remembered.
The circuit operates from a stabilized voltage source of 5 V.
The input impedance is constant 10K, 22K, 50K, 100K.
Payment is possible via Payoneer or to a bank card. It is also possible to buy on Ebay.
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/267166457170
https://sgaudioua.etsy.com/listing/1798144856
https://sgaudioua.etsy.com/listing/1871270901
Stereo controller kit (2 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo channels
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/267166457170
https://www.ebay.com/itm/266863103276
https://www.ebay.com/itm/266932731942
https://www.ebay.com/itm/267151831175
Stereo controller kit XLR (2 channels XLR), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Input selector for 4 stereo XLR channels
https://www.ebay.com/itm/267197617946
https://sgaudioua.etsy.com/listing/1824028825
https://sgaudioua.etsy.com/listing/1825237975
https://www.ebay.com/itm/266918250389
https://www.ebay.com/itm/266936692441
Stereo controller kit (8 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
https://www.ebay.com/itm/266863035366
Stereo controller kit (6 channels), includes: the controller itself, IR remote control, encoder, indication on two segments with IR receiver
Attachments
Analog Line Level Photo Gallery
- By Mooly
- Analog Line Level
- 35 Replies
This thread is now a Sticky for you all to post pictures of your Analogue Line Level diy efforts and projects.
Please try and keep the thread on topic and take any technical discussions over to either a new discussion thread or the original thread if there is one.
Rega Elicit MK1 system - took unknown damage
- By edomobius
- Solid State
- 1 Replies
Hello to everyone. I'm having troubles with an old Rega Elicit MK1. It sounded so nice and it was a robust system, since it met my grandfather. Actually not himself, but his illness. He's not able to remember things, he probably made a misconnection... so, I thought, that's a bit of a complex repair... and I'm not sure if it's possible... but I'd like to make him listen to his collections again, and here I am.
Diagnosis: The amp was dead, no power. So I opened it, and found blown fuses, and quite some damage.
I took a photo of the incriminated section, which is on the power side of the left channel. Ouch!
Following the schematics I made some basic tests with a multimeter and a transistor tester. I've found and replaced a list of parts that were damaged, which include the finals (2SC2922 and 2SA1216), the BD139 and 140 which were totally blown (T14, T17, T18, T13, T21, T22) as the 100uF capacitor C30, the big resistors R11 and R12 (blown!) as well as R18, R36, and R49, and some zener diodes. T48 on the -39.5V was also tested bad, but with no visible damage.
I remade some tracks that were vapourized (ouch), I tested the other small transistors too (only in the amplification section of the board), and they were all good.
Feeling quite confident I powered on the amplifier, and there was life. Connecting a speaker (the right one) revealed sound! I did a rough impedance test, I swapped the channel, it sounded amazing. hooray! You might think... 🙂
Because after some time... a POP was heard! But the amp was still on, so no fuse was triggered. I power cycled it, giving some time to cool down, thinking it was the thermal protection.
Nevermind, the music played again.
Remember I did the test in mono, because I had only the right speaker at that time. Later inspecting the other speaker (left) I found one woofer's coil stuck upwards, cooked to perfection. Replacement of the woofer done, but the internal connection of the loudspeakers' crossover was not clear to me. The loudspeakers are the Rega XEL. I can provide more detailed information if needed.
Anyway, the first stereo test was made...
Sure enough, after less than 2 minutes, there was the POP disconnection sound, much louder at the left speaker (the one that I repaired), and the sound went mute. Power cycling the system "resetted" the protection (the DC one?? I've read that the thermal protection turns the "Elicit" front LED red, but I'm not sure about more localized protections, if that was a protection at all) but the issue persisted, so I opened it again and found R36 and R49 burned again, on the left channel. Was that for the impedance of the left speaker, the one that was blown and repaired, not being high enough? Was it the crossover's fault, or the amp still has some issues?
And that's where I'm now. I also found a cold solder at LED3. That is to see the +39.5V, and it's the only led that turns on slow and turns off fast. Maybe that was only that solder joint that triggered T25, which caused the pop?
There are some big capacitor which hold a lot of charge, and don't think they'll discharge after days, like I did: you need to discharge them, I learned the hard way 🙂 but when holding charge, the finals show short?? I don't know.
Your help is very much appreciated; I'm absolutely no audio technician or expert, forgive me for the technical mistakes I made, and thank you for your patience reading all of this.
Ciao!
Diagnosis: The amp was dead, no power. So I opened it, and found blown fuses, and quite some damage.
I took a photo of the incriminated section, which is on the power side of the left channel. Ouch!
Following the schematics I made some basic tests with a multimeter and a transistor tester. I've found and replaced a list of parts that were damaged, which include the finals (2SC2922 and 2SA1216), the BD139 and 140 which were totally blown (T14, T17, T18, T13, T21, T22) as the 100uF capacitor C30, the big resistors R11 and R12 (blown!) as well as R18, R36, and R49, and some zener diodes. T48 on the -39.5V was also tested bad, but with no visible damage.
I remade some tracks that were vapourized (ouch), I tested the other small transistors too (only in the amplification section of the board), and they were all good.
Feeling quite confident I powered on the amplifier, and there was life. Connecting a speaker (the right one) revealed sound! I did a rough impedance test, I swapped the channel, it sounded amazing. hooray! You might think... 🙂
Because after some time... a POP was heard! But the amp was still on, so no fuse was triggered. I power cycled it, giving some time to cool down, thinking it was the thermal protection.
Nevermind, the music played again.
Remember I did the test in mono, because I had only the right speaker at that time. Later inspecting the other speaker (left) I found one woofer's coil stuck upwards, cooked to perfection. Replacement of the woofer done, but the internal connection of the loudspeakers' crossover was not clear to me. The loudspeakers are the Rega XEL. I can provide more detailed information if needed.
Anyway, the first stereo test was made...
Sure enough, after less than 2 minutes, there was the POP disconnection sound, much louder at the left speaker (the one that I repaired), and the sound went mute. Power cycling the system "resetted" the protection (the DC one?? I've read that the thermal protection turns the "Elicit" front LED red, but I'm not sure about more localized protections, if that was a protection at all) but the issue persisted, so I opened it again and found R36 and R49 burned again, on the left channel. Was that for the impedance of the left speaker, the one that was blown and repaired, not being high enough? Was it the crossover's fault, or the amp still has some issues?
And that's where I'm now. I also found a cold solder at LED3. That is to see the +39.5V, and it's the only led that turns on slow and turns off fast. Maybe that was only that solder joint that triggered T25, which caused the pop?
There are some big capacitor which hold a lot of charge, and don't think they'll discharge after days, like I did: you need to discharge them, I learned the hard way 🙂 but when holding charge, the finals show short?? I don't know.
Your help is very much appreciated; I'm absolutely no audio technician or expert, forgive me for the technical mistakes I made, and thank you for your patience reading all of this.
Ciao!
Attachments
I built a pair of Linsley-Hood 1969 Class A amps and they sound so good
- By hild
- Solid State
- 17 Replies
Attachments
Caladan by Clayton Shaw DIY
Inspired by New Record Day video about the Caladan by Clayton Shaw, I decided to do it DYI since shipping costs to Japan are ridiculous (and no international deliveries at the moment provided). My MiniDSP serves as an active crossover for two ICEPower 125ASX2 amplifiers. They sound amazing, using a Linkwitz-Riley filter 48db at 1kHz and some gain in the low end, Never thought open baffle speaker can have such a lot of low end, while the speaker membrane is barely moving. The speaker disapear and you feel like in a live concert. This works also for my music with distorted guitars, not only for the high end demo music. Bass guitars sound so real. This is the first day listening to them after waiting 3months for the delivery of the 12inch speaker drivers....I guess no burn in needed. Clayton Shaw chose the perfect drivers.....
