Am Selling My Used OPPO UDP-205 4k Blu-Ray player
- By paullarry
- Vendor's Bazaar
- 3 Replies
Attachments
The Phrugal Phono Stage - a Tasty M65 Preamp for under $200
- By dubadub
- Tubes / Valves
- 2 Replies
Greetings, Friend. Are you a Frugal Fi guy?
This is a Phono Stage built around a kit from ZeroZone. It's a clone of the Shure M65 circuit, using a pair of 12AX7s in a Class A configuration. PSU is on the board. A kit with all parts can be found on eBay or Ali for under $30, transformers cost about the same, and the PCB can be found for around $12.
I've read the threads on the EAR834p builds, and I see what can be done with $600, but let's consider a listener with a smaller budget. I don't know about the rest of you, but given the current economy, and the number of record-listening folks stuck home, out of work and bored, I think a project like this is due. I've only been messing with tubes since the beginning of the pandemic, getting time on the bench when my 2-year-old naps and researching when time allows, so this may be a tired subject already. Please feel free to steer me to any other M65-based projects, or share any advice you have.
The lack of the v3 tube and the lower power requirements (30VA, 100v@20mA , 14v@800mA ) bring the cost of all components well below $200, depending on options. The small size of the PCB (4x5.25", 100x135mm) allows the use of very small enclosures such as Hammond 1455Q2201BK (8.6x5x2")when the transformer is placed atop the chassis, under a steel cap, with a small amount of fabrication necessary so the tops of the tubes can stick out. If you don't want the tubes to show, the larger Hammond 1458VE3 (8x10x3") can accomodate transformer and PCB with very little fab work. Both of these options are under $50, as I'm sure are many other chassis from many manufacturers. I've been impressed with Hammond's quality and range of options so far.
For this build I swapped the film caps included with the kit with Orange Drops. C1 and C2 are 0.47uF, and the others are 0.047uF. This is the low value spec'd on the PCB itself, 0.47uF-0.047uF) and the caps included with the kit are 0.33uF. The preamp has a wonderful clear sound, especially in the range of the acoustic guitar, but the bass is lacking, and I wonder if the smaller 0.047 caps are responsible. Any thoughts on appropriate values for those caps?
Since each channel gets its own tube, both tubes should be high-quality V1 tubes, HG+ or similar, but TBH it sounds great with a cheap pair of matched JJs.
I've learned that the original M65 did not have a true RIAA de-emphasis, and that different parts in the feedback loop can address this, swapping the 470pF for a 680 Silver Mica and swapping the 100K for a 110K resistor, and swapping the 1800pF for a 2200pF polystyrene while leaving the 4M7 + 3M resistors in place.
In terms of off-roading, the PCB traces lead to pins 4&5 to heat the tubes at 12v, so a similar 30VA transformer with a 7v@1,6A (?) output could power a pair of 6N2P-EV tubes, for substantial savings. Perhaps different components would be called for in the PSU section? This part I'm just spitballin'
I have a PDF of the circuit here:
SHURE-PHONO-RIAA-SCH.pdf - Google Drive
And Here's the original BOM:
M65舒尔唱放 - Google Sheets
I've been working on a BOM of upgraded components from Mouser, and I'd appreciate any feedback on my selections.
M65 WORKSHEET - Google Sheets
This is a Phono Stage built around a kit from ZeroZone. It's a clone of the Shure M65 circuit, using a pair of 12AX7s in a Class A configuration. PSU is on the board. A kit with all parts can be found on eBay or Ali for under $30, transformers cost about the same, and the PCB can be found for around $12.
I've read the threads on the EAR834p builds, and I see what can be done with $600, but let's consider a listener with a smaller budget. I don't know about the rest of you, but given the current economy, and the number of record-listening folks stuck home, out of work and bored, I think a project like this is due. I've only been messing with tubes since the beginning of the pandemic, getting time on the bench when my 2-year-old naps and researching when time allows, so this may be a tired subject already. Please feel free to steer me to any other M65-based projects, or share any advice you have.
The lack of the v3 tube and the lower power requirements (30VA, 100v@20mA , 14v@800mA ) bring the cost of all components well below $200, depending on options. The small size of the PCB (4x5.25", 100x135mm) allows the use of very small enclosures such as Hammond 1455Q2201BK (8.6x5x2")when the transformer is placed atop the chassis, under a steel cap, with a small amount of fabrication necessary so the tops of the tubes can stick out. If you don't want the tubes to show, the larger Hammond 1458VE3 (8x10x3") can accomodate transformer and PCB with very little fab work. Both of these options are under $50, as I'm sure are many other chassis from many manufacturers. I've been impressed with Hammond's quality and range of options so far.
For this build I swapped the film caps included with the kit with Orange Drops. C1 and C2 are 0.47uF, and the others are 0.047uF. This is the low value spec'd on the PCB itself, 0.47uF-0.047uF) and the caps included with the kit are 0.33uF. The preamp has a wonderful clear sound, especially in the range of the acoustic guitar, but the bass is lacking, and I wonder if the smaller 0.047 caps are responsible. Any thoughts on appropriate values for those caps?
Since each channel gets its own tube, both tubes should be high-quality V1 tubes, HG+ or similar, but TBH it sounds great with a cheap pair of matched JJs.
I've learned that the original M65 did not have a true RIAA de-emphasis, and that different parts in the feedback loop can address this, swapping the 470pF for a 680 Silver Mica and swapping the 100K for a 110K resistor, and swapping the 1800pF for a 2200pF polystyrene while leaving the 4M7 + 3M resistors in place.
In terms of off-roading, the PCB traces lead to pins 4&5 to heat the tubes at 12v, so a similar 30VA transformer with a 7v@1,6A (?) output could power a pair of 6N2P-EV tubes, for substantial savings. Perhaps different components would be called for in the PSU section? This part I'm just spitballin'
I have a PDF of the circuit here:
SHURE-PHONO-RIAA-SCH.pdf - Google Drive
And Here's the original BOM:
M65舒尔唱放 - Google Sheets
I've been working on a BOM of upgraded components from Mouser, and I'd appreciate any feedback on my selections.
M65 WORKSHEET - Google Sheets
Purifi 1ET400A Input buffer with Korg Nutube valve
- By jalejos
- Vendor's Bazaar
- 5 Replies
Purifi 1ET400A / Hypex NC500 Input buffer with Korg Nutube valve [Updated]
This buffer is based on the double Nutube triode from the Japanese manufacturer Korg. The circuit is valid for Class D power modules, model 1ET400 from manufacturer Purifi Audio and model NC500 from manufacturer Hypex (with some limitation). They both use the same expansion connector and are fully compatible.
First of all, we must bear in mind that, with this buffer, we want to achieve the maximum power, dynamics, damping factor and efficiency, typical of class D modules, and mix it with the warmth that valves provide. This is not a buffer with very low distortion, for this we already have other buffers in our store with very good results. This is a buffer that gives us a sound very similar to vacuum valves.
This buffer works fully in differential mode, so the input has to be balanced with an XLR connector (or TRS). With the balanced audio input, we provide an appropriate output signal to attack the balanced input of the power module. In the case of using an unbalanced audio signal (with RCA connection), we will have a loss of gain of 6dB, which is equivalent to four times less output power.
The circuit is prepared for use with the original Hypex power supply, model SMPS1200/A700, in the case of use with the NC500 module, or with the model SMPS1200/A400, in the case of use with the Purifi Audio module. In both cases, an important point must be taken into account: Jumpers J6 and J7 (Vaux marked in red) must be placed in position 2-3 (unregulated Vaux) as indicated in the green box. This way we will obtain the correct voltage to supply the circuit in J4 connector.
The circuit is made with the best medical grade and audiophile grade electronic components. The resistors are made of metallic film with a 0.1% tolerance. Electrolytic capacitors are Nichicon special for audio. Sparkoslabs very low noise voltage regulators have been used. The two variable resistors at the top of the pcb adjust the maximum distortion value and the two variable resistors located at the bottom adjust the output signal in differential mode. These resistors are factory adjusted to the optimum value so that the power module works in the best conditions. It is not advisable to touch these resistors to avoid a malfunction of the circuit. Only if laboratory instruments are available could they be minimally varied until the desired function is achieved.
The circuit is adjusted so that with, an input sensitivity of 500mV (balanced), an output power of 160W RMS at 4 ohms and 2,67% THD+N (with Purifi Audio).
Higher output powers can be achieved by increasing the input signal, but the distortion will rise exponentially.
The PCB measures 125 x 63mm and has several connectors.
Connections are made as follows:
The SMPS1200/Ax00 J4 connector has the following wiring:
The SMPS1200/Ax00 J1 connector has the following wiring:
The kit consists of the following material:
The rest of the connectors and cables are usually included in the power modules. They can be obtained individually on the Hypex or Purifi website
Details in Buffer Korg Nutube for Hypex NC500 and Purifi Audio 1ET400 | atm-audio.com
Buffer with op. amp. https://atm-audio.com/product/buffer-hypex-nc500/
[UPDATED Summer 2020]
We have recently made a new version of the Nutube buffer (V2). We have replaced JFET transistors and used very low noise instrumentation op amps as impedance adapters. In this way, we have managed to reduce the total harmonic distortion (THD) throughout the power range, especially in the 100-500W range, which is where the V1 buffer rises a lot, keeping it below 1%.
This curve was measured with the Nutube V2 buffer connected to the Hypex NC500 module.
We have achieved, for a +/-1 VRMS differential input signal, an output voltage of 141 VPP before clipping. The total harmonic distortion + noise (THD+N) is 2.34%. The distortion of the second harmonic (2H) is 0.27%. With this numbers, we have the equivalent of a 625 WRMS tube amplifier @ 4 Ω, with a total gain of almost 36,19 dB.
In the next graphs you can see some measurements of the THD+N at 1 kHz and its harmonics depending of the output voltage:
https://atm-audio.com/500-w-hybrid-power-amplifier-with-nutube-valve-for-hypex-nc500/
[UPDATED November 2020]
These are the buffer measurements with the Purifi Audio module.
For a differential input signal of +/- 500mV RMS, we have an output voltage of 98 VPP before clipping. The total harmonic distortion + noise (THD + N) at this point is 1.53%. The distortion of the second harmonic (2H) is 0.037%. With these numbers, we have the equivalent of a 300 WRMS tube amplifier at 4 Ω, with a total gain of 34 dB.
As can be seen from the graph, for 100 WRMS amplification the distortion is only 0.35%. Up to 50W the distortion is less than 0.2%
Power vs THD+noise
In the next graphs you can see some measurements of the THD+N at 1 kHz and its harmonics depending of the output voltage:
(5W @ 4 Ohms)
(100W @ 4 Ohms)
https://atm-audio.com/300-w-hybrid-power-amplifier-with-nutube-valve-v2/
This buffer is based on the double Nutube triode from the Japanese manufacturer Korg. The circuit is valid for Class D power modules, model 1ET400 from manufacturer Purifi Audio and model NC500 from manufacturer Hypex (with some limitation). They both use the same expansion connector and are fully compatible.
First of all, we must bear in mind that, with this buffer, we want to achieve the maximum power, dynamics, damping factor and efficiency, typical of class D modules, and mix it with the warmth that valves provide. This is not a buffer with very low distortion, for this we already have other buffers in our store with very good results. This is a buffer that gives us a sound very similar to vacuum valves.
This buffer works fully in differential mode, so the input has to be balanced with an XLR connector (or TRS). With the balanced audio input, we provide an appropriate output signal to attack the balanced input of the power module. In the case of using an unbalanced audio signal (with RCA connection), we will have a loss of gain of 6dB, which is equivalent to four times less output power.
The circuit is prepared for use with the original Hypex power supply, model SMPS1200/A700, in the case of use with the NC500 module, or with the model SMPS1200/A400, in the case of use with the Purifi Audio module. In both cases, an important point must be taken into account: Jumpers J6 and J7 (Vaux marked in red) must be placed in position 2-3 (unregulated Vaux) as indicated in the green box. This way we will obtain the correct voltage to supply the circuit in J4 connector.
The circuit is made with the best medical grade and audiophile grade electronic components. The resistors are made of metallic film with a 0.1% tolerance. Electrolytic capacitors are Nichicon special for audio. Sparkoslabs very low noise voltage regulators have been used. The two variable resistors at the top of the pcb adjust the maximum distortion value and the two variable resistors located at the bottom adjust the output signal in differential mode. These resistors are factory adjusted to the optimum value so that the power module works in the best conditions. It is not advisable to touch these resistors to avoid a malfunction of the circuit. Only if laboratory instruments are available could they be minimally varied until the desired function is achieved.
The circuit is adjusted so that with, an input sensitivity of 500mV (balanced), an output power of 160W RMS at 4 ohms and 2,67% THD+N (with Purifi Audio).
Higher output powers can be achieved by increasing the input signal, but the distortion will rise exponentially.
The PCB measures 125 x 63mm and has several connectors.
- J1 Balanced audio input connector.
- J3 IDC connector 2x5 flat cable.
- J4 Angled connector 2x18.
- J5 Speaker Fastom connector (+)
- J6 Speaker Fastom connector (-)
- J7 Power connector.
Connections are made as follows:
- J1 Buffer Nutube to balanced input connector (XLR o TRS).
- J3 Buffer Nutube to J4 SMPS1200/Ax00 with flat cable and IDC connectors.
- J4 Buffer Nutube to power module.
- J5 Buffer Nutube to Speaker (+)
- J6 Buffer Nutube to Speaker (-)
- J7 Buffer Nutube to J1 SMPS1200/Ax00.
The SMPS1200/Ax00 J4 connector has the following wiring:
- J4.1 + 21Vdc
- J4.2 - 21Vdc
- J4.3 GND
- J4.4 No Con.
- J4.5 No Con.
- J4.6 Amp. enable
- J4.7 No Con.
- J4.8 No Con.
- J4.9 GND
- J4.10 DC Error
The SMPS1200/Ax00 J1 connector has the following wiring:
- J1.1 VDR+
- J1.2 HV+
- J1.3 GND
- J1.4 VDR-
- J1.5 HV-
- J1.6 GND
The kit consists of the following material:
- Buffer Nutube PCB (2 units)
- Molex Connector J1 with pins (2 units) w/o cables
- Speakers female Fastom Connector (4 units) w/o cables
The rest of the connectors and cables are usually included in the power modules. They can be obtained individually on the Hypex or Purifi website
Details in Buffer Korg Nutube for Hypex NC500 and Purifi Audio 1ET400 | atm-audio.com
Buffer with op. amp. https://atm-audio.com/product/buffer-hypex-nc500/
[UPDATED Summer 2020]
We have recently made a new version of the Nutube buffer (V2). We have replaced JFET transistors and used very low noise instrumentation op amps as impedance adapters. In this way, we have managed to reduce the total harmonic distortion (THD) throughout the power range, especially in the 100-500W range, which is where the V1 buffer rises a lot, keeping it below 1%.
This curve was measured with the Nutube V2 buffer connected to the Hypex NC500 module.
We have achieved, for a +/-1 VRMS differential input signal, an output voltage of 141 VPP before clipping. The total harmonic distortion + noise (THD+N) is 2.34%. The distortion of the second harmonic (2H) is 0.27%. With this numbers, we have the equivalent of a 625 WRMS tube amplifier @ 4 Ω, with a total gain of almost 36,19 dB.
In the next graphs you can see some measurements of the THD+N at 1 kHz and its harmonics depending of the output voltage:
https://atm-audio.com/500-w-hybrid-power-amplifier-with-nutube-valve-for-hypex-nc500/
[UPDATED November 2020]
These are the buffer measurements with the Purifi Audio module.
For a differential input signal of +/- 500mV RMS, we have an output voltage of 98 VPP before clipping. The total harmonic distortion + noise (THD + N) at this point is 1.53%. The distortion of the second harmonic (2H) is 0.037%. With these numbers, we have the equivalent of a 300 WRMS tube amplifier at 4 Ω, with a total gain of 34 dB.
As can be seen from the graph, for 100 WRMS amplification the distortion is only 0.35%. Up to 50W the distortion is less than 0.2%
Power vs THD+noise
In the next graphs you can see some measurements of the THD+N at 1 kHz and its harmonics depending of the output voltage:
(5W @ 4 Ohms)
(100W @ 4 Ohms)
https://atm-audio.com/300-w-hybrid-power-amplifier-with-nutube-valve-v2/
Audio Physic SPARK - first version (not II/III) - Test reviews and Part List wanted
- Multi-Way
- 0 Replies
Attachments
Trying to: 2-way Linear Phase Crossover
- By Art Benjamin
- Multi-Way
- 5 Replies
Greetings,
I guess I'll start by explaining what I'm doing.
I had been using a wideband driver and it's phase was mostly centered around zero degrees from the treble down to a few hundred Hertz. The stereo image and 3-D depth was fantastic.
The thing was, the wideband needed baffle step compensation and a tweeter. Adding even a first order crossover introduced phase shift. Along with increases phase shift I noticed diminished imaging and depth.
Woofer:
BSC
2nd order low pass
2 notch filters
Tweeter:
1st order high pass
1st order allpass to to align the phase 5kHz-20kHz
voltage devider
There is also impedance correction to reduce impedance phase. None of these had any practical effect on the acoustic phase, other than the allpass aligning the phase where it was needed.
The point I'm getting to is that I noticed one design in XSim3D called the "Cosyne3 with AllPass practical" as shown in the next image below. It has a mostly linear phase down to 500Hz. How exactly is this linear-phase response achieved?
I guess I'll start by explaining what I'm doing.
I had been using a wideband driver and it's phase was mostly centered around zero degrees from the treble down to a few hundred Hertz. The stereo image and 3-D depth was fantastic.
The thing was, the wideband needed baffle step compensation and a tweeter. Adding even a first order crossover introduced phase shift. Along with increases phase shift I noticed diminished imaging and depth.
Woofer:
BSC
2nd order low pass
2 notch filters
Tweeter:
1st order high pass
1st order allpass to to align the phase 5kHz-20kHz
voltage devider
There is also impedance correction to reduce impedance phase. None of these had any practical effect on the acoustic phase, other than the allpass aligning the phase where it was needed.
The point I'm getting to is that I noticed one design in XSim3D called the "Cosyne3 with AllPass practical" as shown in the next image below. It has a mostly linear phase down to 500Hz. How exactly is this linear-phase response achieved?
Kenwood KA-3700
- By zenzaman
- Solid State
- 0 Replies
I'll start this thread with a very short prologue... (feel free to jump to the second paragraph)
I'm totally new to electronics and only have a vague understanding of the various components inside a circuit (I know what each does on it's own, but get quickly confused by circuits such as this one - can't follow the "logic of the current" yet), but I would really like to learn. So I thought that the best way to learn is to just dive in, make some black magic smoke
, ask stupid questions and experiment. I'll just call it 'applied electronics' so I can feel better.
So, I searched the ads for a defective amp and this little Kenwood looked like a good place to start (not that complex, good looking, fairly good reviews when working).
The previous owner said it had one totally dead channel and the other with low volume and heavy distortions. I didn't plug it in and started looking for bad parts. So far I found one burnt resistor and one burnt fuse. I checked all transistors in-circuit and removed those that read 'funny'. Out of them 4 proved to be dead (various shorts plus one open base-collector junction).
I marked all identified components in red on the schematic.
Next step is to make a parts list on mouser (including a full recap for the electrolytics) but I have a real hard time picking equivalents for the transistors and I'm also not sure whether I should only replace the faulty transistors, replace them in pairs (as per schematic - both in a darlington pair even if only one is bad), replace them in pairs across the two channels (ie. also replace the inverted darlington pair in the left channel even if both read ok). I tried to find replacements filtering by specifications but I would feel a lot safer to get suggestions from people who actually know what they're talking about 🙂
All suggestions will help a lot 🙂
Thank you!
I'm totally new to electronics and only have a vague understanding of the various components inside a circuit (I know what each does on it's own, but get quickly confused by circuits such as this one - can't follow the "logic of the current" yet), but I would really like to learn. So I thought that the best way to learn is to just dive in, make some black magic smoke
, ask stupid questions and experiment. I'll just call it 'applied electronics' so I can feel better.So, I searched the ads for a defective amp and this little Kenwood looked like a good place to start (not that complex, good looking, fairly good reviews when working).
The previous owner said it had one totally dead channel and the other with low volume and heavy distortions. I didn't plug it in and started looking for bad parts. So far I found one burnt resistor and one burnt fuse. I checked all transistors in-circuit and removed those that read 'funny'. Out of them 4 proved to be dead (various shorts plus one open base-collector junction).
I marked all identified components in red on the schematic.
Next step is to make a parts list on mouser (including a full recap for the electrolytics) but I have a real hard time picking equivalents for the transistors and I'm also not sure whether I should only replace the faulty transistors, replace them in pairs (as per schematic - both in a darlington pair even if only one is bad), replace them in pairs across the two channels (ie. also replace the inverted darlington pair in the left channel even if both read ok). I tried to find replacements filtering by specifications but I would feel a lot safer to get suggestions from people who actually know what they're talking about 🙂
All suggestions will help a lot 🙂
Thank you!
Attachments
Garrard Type A Mk II Makeover
- By knotscott
- Analogue Source
- 3 Replies
This started out as my uncle's Garrard Type A Mk II record changer. It got passed on to me last winter. The motor worked, but the other functions needed help. Once I looked under the hood, I realized it needed more expertise than I could provide to restore it's original functions. I made the decision to strip the automation, upgrade it with a Marantz tonearm, and build a custom cherry/curly maple plinth. I also brushed up the platter, painted the tray, added an acrylic mat, and mounted a decent LP Gear Vivid Line stylus to an AT-3600L cart. I removed the spring suspension in favor of vibration isolating rubber feet, but kept the original motor, controls tray, and rim drive system. Once dialed it in, it sounds pretty darn good to me. I've been having a blast playing oldies from his era on it, but it does just fine with modern recordings too. Very enjoyable and satisfying first TT project.
/Haps A New Basic Opamp App: The Floating Interactive Current Multiplier.
- By U130421
- Solid State
- 7 Replies
This two resistor opamp circuit multiplies the input current by ( Rin/Rout+1).
The source sees the load impedance multiplied by the same factor and the load sees the source with the inverse factor. Bellow are two example as ×2 and ×1000 factors.
Hayk
Attachments
Shunt Regulator
- By PoweRex
- Power Supplies
- 49 Replies
Hi guys,
Can anybody provide the original parts list for the Borbely "EB-906/255" All-Fet Shunt Regulator ?
Thanks.
Can anybody provide the original parts list for the Borbely "EB-906/255" All-Fet Shunt Regulator ?
Thanks.
