DIY "Gold" Carbon resistor
Pre-announcement: I am a China fan, and my English is not very good. All English is supported by the translator. I am deeply sorry if u can't understand and have any ambiguity.
Disclaimer:
1: This is a geek production, and the final test conclusion after our production is that it can hardly be used as a standard resistor and its performance is poor. Unless you use a special packaging method: airtight packaging.
2: Its production process maybe full of environmental bad factors. This amateur production is not for environmentalists. Please watch it according to your local cultural habits, legal provisions and administrative system.
A long time ago, I heard the myth of PIO capacitor and Allen Bradley (this is often simply called AB in China) carbon composition resistor. They are not the most perfect representatives of audio fidelity, but they have occupied a considerable market in historical audio manufacturing based on their cheapness and universality, so that it has become a fashion and habit. I have some PIO and CC on hand as samples, but they still can't satisfy me.
1: The CC produced later used the sintering process, just like clay pencil lead. After mixing graphite raw materials and clay, it was pressed and molded and sent to a high-temperature furnace for graphitization, forming a solid whole. This process typically has ideal resistance performance in CC-hard structure, low water absorption, low voltage coefficient (in CC family series), good durability and drift rate. But the question is, what is the purpose of this resistor? I want him to give me a special distortion. If you do it well, where will my distortion go?
2: Since the later CC is invariably a sintering process, I don't know enough about the most traditional organic bonding process. What I want to do is: Can I build a process different from the normal CC and form a resistor, which can not only help me realize the fun of "home DIY", but also be used in some unique and strange places? I don't want EE to criticize me here. "This resistor is too bad, it doesn't apply to audio." I know this clearly. I need it, I'll do it-that's my purpose. Fortunately, based on the knowledge given by various network platforms and enthusiastic netizens, I successfully manufactured a "junk" resistor-"gold" carbon resistor. The following is the production process.
Disclaimer:
1: This is a geek production, and the final test conclusion after our production is that it can hardly be used as a standard resistor and its performance is poor. Unless you use a special packaging method: airtight packaging.
2: Its production process maybe full of environmental bad factors. This amateur production is not for environmentalists. Please watch it according to your local cultural habits, legal provisions and administrative system.
A long time ago, I heard the myth of PIO capacitor and Allen Bradley (this is often simply called AB in China) carbon composition resistor. They are not the most perfect representatives of audio fidelity, but they have occupied a considerable market in historical audio manufacturing based on their cheapness and universality, so that it has become a fashion and habit. I have some PIO and CC on hand as samples, but they still can't satisfy me.
1: The CC produced later used the sintering process, just like clay pencil lead. After mixing graphite raw materials and clay, it was pressed and molded and sent to a high-temperature furnace for graphitization, forming a solid whole. This process typically has ideal resistance performance in CC-hard structure, low water absorption, low voltage coefficient (in CC family series), good durability and drift rate. But the question is, what is the purpose of this resistor? I want him to give me a special distortion. If you do it well, where will my distortion go?
2: Since the later CC is invariably a sintering process, I don't know enough about the most traditional organic bonding process. What I want to do is: Can I build a process different from the normal CC and form a resistor, which can not only help me realize the fun of "home DIY", but also be used in some unique and strange places? I don't want EE to criticize me here. "This resistor is too bad, it doesn't apply to audio." I know this clearly. I need it, I'll do it-that's my purpose. Fortunately, based on the knowledge given by various network platforms and enthusiastic netizens, I successfully manufactured a "junk" resistor-"gold" carbon resistor. The following is the production process.
Reverse IEC connectors/cords?
- By seventenths
- Parts
- 7 Replies
Why are these available? Years ago I mistakingly ordered a couple of sets and can see no purpose other than offering up a chance to make a big mistake? That said, faston connectors fit the otherwise dangerous male pins on the cord which is coming in handy at the moment as I troubleshoot a piece of gear but is there a valid argument for their existence that I'm not aware of?
Huaji Audio 6P14P (EL84) + 6N1P PP amp kit build #2
- Tubes / Valves
- 91 Replies
Somehow way back in 2011, I went down the "home theater" rabbit hole only to find out that it wasn't so great after all. I never should have given up my 2-channel tube amp in favor of a 5-channel solid state monster. About 10 years later I discovered that I had simply stopped listening to music - period. That's sad. Very sad. I tried listeing to stereo recordings with the solid state amp and preamp, and it just wasn't right. I hated it. Then I remembered why I dumped solid state in 1993 and went all tube.
This time last year, I was between jobs and fed up with trying to listen to the expensive - not cheap - solid state amplifier that I hated. With no job and not wanting to spend any money, I somehow found an inexpensive little Chinese tube amp kit built by XrayTonyB on YouTube:
Login to view embedded media
It looked like a nice little amplifier, and it seemed to perform ok in his tests, especially given the sub-$400 price tag. I found out that the kit had been updated to remove the automatic "loudness" compensation circuit that he spent time removing in the videos. So I bought the kit from China on AliExpress. I hadn't fiddled with electronics since the early 1990's, but with his video tutorials, I figured that I had a decent chance of success. I sold my solid state amp and preamp to pay for the project once it was complete. The build wasn't without trials and tribulations. I first had to learn to use PSUdesigner to determine that changing the resistor in the C-R-C filter could very easily and inexpensively reduce the overvoltage caused by putting 120V from the wall through a 110V power transformer, and without using a bucking transformer. The problems started when I broke a secondary lead from the power transformer and had to do a tiny, tiny repair of that fine wire. Then I broke one of the output transformers the same way without knowing it. A power tube then blew, and I was left very frustrated. With patience and help from a number of forum members here, we found the problem, I fixed the hair-like wires that I broke on the OPT, and I ended up with a very nice sounding little amplifier for only $400. I will never, ever use a solid state amplifier again.
The first build thread is at the link below, with a lot of boring newbie questions, and of course the problems that I caused by breaking those tiny transformer wires.
https://www.diyaudio.com/community/...s-before-i-build-maybe-during-if-i-do.394962/
I spent a great deal of time translating the 67 pages of directions from Chinese to English. My translated instruction manual was available on a Google drive link in the first build thread. I have them if anyone needs them. I don't know if those Google drive links still work.
Why am I doing this same amp kit again? Maybe curiosity killed the cat as the saying goes, but I want to see what happens if I change a few things, like using larger output transformers. I'm really happy with the way the amplifier sounds, and anyone who builds this kit shouldn't hesistate to build it just as it comes in the box. Just be sure to adjust the voltage as I described if you are using USA 120V instead of 110V. It can be done simply by changing the power supply resistor and using the included lower voltage Zener diode as described in my first built thread. Then curiosity sets in ... what would happen if I change this ... or this ... and so on.
Why this particular amplifier? 1) It's a kit so ... no fabrication that I hate, I don't have to spend a bunch of time and effort ordering individual parts, and I only have to replace/upgrade any parts I choose like the OPTs, 2) It's not expensive at $312.81 with shipping and tax included (it was on sale plus I used a promo code), 3) I know that I like the sound because I already built one, 4) The compact left-right footprint is perfect for me, 5) I already built one so there is little chance of me making mistakes this time. I had to raise my confidence by building the first one, breaking it twice, blowing a tube, repairing it, and finally ending up with a great amp. So those all are valid reasons for me, despite the circuit not being "ideal." I know there are other designs available for people who really want to build their own amps from scratch, but I don't want to do that, at least not anytime soon. Maybe someday but not now. In an ideal world I'd find a proven circuit and scratch build a custom pair of EL84 monoblocks. We don't live in a perfect world.
I am not against making simple modifications to this amp, and I would like to look at those before I proceed. Suggestions welcome. However, it is a PCB amp with a very crowded chassis, so modifications have to be limited. I also do not want to seriously alter the sound as I love it the way it is. It sounds "right" to me unlike so many amplifiers. I don't know what makes the amp sound so good, but it does. It gets the timing of the music right, and so many amps get that wrong. I'm not sure how else to put it. I do want to see what bigger better OPTs bring to the table. There also may be parts of the circuit that haven't been properly optimized, so suggestions welcome. I'd like to find a way to use 4 individual bias resistors, but it can't be done on the PCB. I'll have to see if they can be relocated to a terminal strip screwed to the side of the chassis I guess.
I will be using the excellent sounding long-life 6P14P-ER (Russian 6П14П-EP) power tubes and the equally excellent sounding 6N1P-EV (Russian 6Н1П-ЕВ) driver tubes. I already have these tubes. Spec sheets are attached.
The schematic is attached. Values in green are actual values measured in my current amplifier. When I say that modifications must be limited, I mean very seriously limited as there is precious little space inside:
The first step is to change the output transformers to see if bigger better ones will make a significant difference. Their larger size will require leaving off the metal box chassis cover to open up additional room on top. That would leave high voltage exposed, and I wanted a 120VAC power transformer instead of 110VAC anyway, so I had one custom made. It has end bells and wire leads, so there will be nothing dangerous left exposed. Since the output transformers also will be exposed, they also require covers. I prefer the look of end bells rather than boxy square covers, so I made traditional end bells a requirement. I like their "industrial" look. A thread looking at various output transformer options for this build is at the link below:
https://www.diyaudio.com/community/threads/el84-pp-output-transformer-recommendations.405967/
I ordered an inexpensive, small SMD-based stepped attenuator for the volume control that seems to be quite popular. SMD stepped attenuator
This time I'm going to spend a few dollars on known quality power supply caps. The coupling and bypass caps that say "WIMA" on them I would bet are fakes, so I'll spend a few dollars getting genuine ones.
I did the first build in all black because the silver "hurts" my eyes 👀 and this one will be all black too, so I have a lot of paint work to do first. I'll start whenever it quits raining. ⛈️🌩️
If I could relocate the adjustment pots for the two magic eye tubes outside the chassis, I'd be tempted to build the kit with them and just leave them out of the sockets when I don't want them flashing at me. They are purely for entertainment and it's just 2 more tubes to worry about. I don't think I can relocate the pots without a major hassle though. Having to disconnect the amp, remove the bottom, reconnect it upside down, adjust the magic eye pots inside, and then put the amp back in the system is ridiculous. Last time I just plugged the holes for the magic eye tube sockets and left them out. If I'm going to leave them off again, I'd like to find someplace that can fabricate a new top plate without those holes instead of just plugging them. Is there someplace online that does small fabrication jobs like making a new top plate for me? The holes have to be very precise as they have to align with the tube sockets and PCB.
And here we are almost 1 year later.
Useful links:
Resistor power calculator: https://www.amplifiedparts.com/tech-articles/resistor-power-rating
Tube bias calculator: https://robrobinette.com/Tube_Bias_Calculator.htm
One of many sellers on AliExpress selling this kit: https://www.aliexpress.us/item/3256802532801472.html
Whenever it quits raining and we get some pleasant weather, I can start the painting. I stripped the silkscreening off of the faceplate last night. It requires a 4 hour soak in acetone and then scrubbing hard with a Scotchbrite pad to get that cleaned off. No other solvent or stripper that I tried last time worked. A soak in acetone does the trick. I do custom decal work, so that's how the printing gets put on the new black paint. After drying, the decals are sealed with multiple layers of satin clear overcoat with multiple wet sandings to get a perfect painted-on look and permanent protection from discoloration.
This time last year, I was between jobs and fed up with trying to listen to the expensive - not cheap - solid state amplifier that I hated. With no job and not wanting to spend any money, I somehow found an inexpensive little Chinese tube amp kit built by XrayTonyB on YouTube:
Login to view embedded media
It looked like a nice little amplifier, and it seemed to perform ok in his tests, especially given the sub-$400 price tag. I found out that the kit had been updated to remove the automatic "loudness" compensation circuit that he spent time removing in the videos. So I bought the kit from China on AliExpress. I hadn't fiddled with electronics since the early 1990's, but with his video tutorials, I figured that I had a decent chance of success. I sold my solid state amp and preamp to pay for the project once it was complete. The build wasn't without trials and tribulations. I first had to learn to use PSUdesigner to determine that changing the resistor in the C-R-C filter could very easily and inexpensively reduce the overvoltage caused by putting 120V from the wall through a 110V power transformer, and without using a bucking transformer. The problems started when I broke a secondary lead from the power transformer and had to do a tiny, tiny repair of that fine wire. Then I broke one of the output transformers the same way without knowing it. A power tube then blew, and I was left very frustrated. With patience and help from a number of forum members here, we found the problem, I fixed the hair-like wires that I broke on the OPT, and I ended up with a very nice sounding little amplifier for only $400. I will never, ever use a solid state amplifier again.
The first build thread is at the link below, with a lot of boring newbie questions, and of course the problems that I caused by breaking those tiny transformer wires.
https://www.diyaudio.com/community/...s-before-i-build-maybe-during-if-i-do.394962/
I spent a great deal of time translating the 67 pages of directions from Chinese to English. My translated instruction manual was available on a Google drive link in the first build thread. I have them if anyone needs them. I don't know if those Google drive links still work.
Why am I doing this same amp kit again? Maybe curiosity killed the cat as the saying goes, but I want to see what happens if I change a few things, like using larger output transformers. I'm really happy with the way the amplifier sounds, and anyone who builds this kit shouldn't hesistate to build it just as it comes in the box. Just be sure to adjust the voltage as I described if you are using USA 120V instead of 110V. It can be done simply by changing the power supply resistor and using the included lower voltage Zener diode as described in my first built thread. Then curiosity sets in ... what would happen if I change this ... or this ... and so on.
Why this particular amplifier? 1) It's a kit so ... no fabrication that I hate, I don't have to spend a bunch of time and effort ordering individual parts, and I only have to replace/upgrade any parts I choose like the OPTs, 2) It's not expensive at $312.81 with shipping and tax included (it was on sale plus I used a promo code), 3) I know that I like the sound because I already built one, 4) The compact left-right footprint is perfect for me, 5) I already built one so there is little chance of me making mistakes this time. I had to raise my confidence by building the first one, breaking it twice, blowing a tube, repairing it, and finally ending up with a great amp. So those all are valid reasons for me, despite the circuit not being "ideal." I know there are other designs available for people who really want to build their own amps from scratch, but I don't want to do that, at least not anytime soon. Maybe someday but not now. In an ideal world I'd find a proven circuit and scratch build a custom pair of EL84 monoblocks. We don't live in a perfect world.
I am not against making simple modifications to this amp, and I would like to look at those before I proceed. Suggestions welcome. However, it is a PCB amp with a very crowded chassis, so modifications have to be limited. I also do not want to seriously alter the sound as I love it the way it is. It sounds "right" to me unlike so many amplifiers. I don't know what makes the amp sound so good, but it does. It gets the timing of the music right, and so many amps get that wrong. I'm not sure how else to put it. I do want to see what bigger better OPTs bring to the table. There also may be parts of the circuit that haven't been properly optimized, so suggestions welcome. I'd like to find a way to use 4 individual bias resistors, but it can't be done on the PCB. I'll have to see if they can be relocated to a terminal strip screwed to the side of the chassis I guess.
I will be using the excellent sounding long-life 6P14P-ER (Russian 6П14П-EP) power tubes and the equally excellent sounding 6N1P-EV (Russian 6Н1П-ЕВ) driver tubes. I already have these tubes. Spec sheets are attached.
The schematic is attached. Values in green are actual values measured in my current amplifier. When I say that modifications must be limited, I mean very seriously limited as there is precious little space inside:
The first step is to change the output transformers to see if bigger better ones will make a significant difference. Their larger size will require leaving off the metal box chassis cover to open up additional room on top. That would leave high voltage exposed, and I wanted a 120VAC power transformer instead of 110VAC anyway, so I had one custom made. It has end bells and wire leads, so there will be nothing dangerous left exposed. Since the output transformers also will be exposed, they also require covers. I prefer the look of end bells rather than boxy square covers, so I made traditional end bells a requirement. I like their "industrial" look. A thread looking at various output transformer options for this build is at the link below:
https://www.diyaudio.com/community/threads/el84-pp-output-transformer-recommendations.405967/
I ordered an inexpensive, small SMD-based stepped attenuator for the volume control that seems to be quite popular. SMD stepped attenuator
This time I'm going to spend a few dollars on known quality power supply caps. The coupling and bypass caps that say "WIMA" on them I would bet are fakes, so I'll spend a few dollars getting genuine ones.
I did the first build in all black because the silver "hurts" my eyes 👀 and this one will be all black too, so I have a lot of paint work to do first. I'll start whenever it quits raining. ⛈️🌩️
If I could relocate the adjustment pots for the two magic eye tubes outside the chassis, I'd be tempted to build the kit with them and just leave them out of the sockets when I don't want them flashing at me. They are purely for entertainment and it's just 2 more tubes to worry about. I don't think I can relocate the pots without a major hassle though. Having to disconnect the amp, remove the bottom, reconnect it upside down, adjust the magic eye pots inside, and then put the amp back in the system is ridiculous. Last time I just plugged the holes for the magic eye tube sockets and left them out. If I'm going to leave them off again, I'd like to find someplace that can fabricate a new top plate without those holes instead of just plugging them. Is there someplace online that does small fabrication jobs like making a new top plate for me? The holes have to be very precise as they have to align with the tube sockets and PCB.
And here we are almost 1 year later.
Useful links:
Resistor power calculator: https://www.amplifiedparts.com/tech-articles/resistor-power-rating
Tube bias calculator: https://robrobinette.com/Tube_Bias_Calculator.htm
One of many sellers on AliExpress selling this kit: https://www.aliexpress.us/item/3256802532801472.html
Whenever it quits raining and we get some pleasant weather, I can start the painting. I stripped the silkscreening off of the faceplate last night. It requires a 4 hour soak in acetone and then scrubbing hard with a Scotchbrite pad to get that cleaned off. No other solvent or stripper that I tried last time worked. A soak in acetone does the trick. I do custom decal work, so that's how the printing gets put on the new black paint. After drying, the decals are sealed with multiple layers of satin clear overcoat with multiple wet sandings to get a perfect painted-on look and permanent protection from discoloration.
Phase Inverter and Volume Control advice needed
- By allears
- Tubes / Valves
- 5 Replies
I'm working on an old Philips EL6425 and would like some advice. This is my first PP amp and I haven't come across phase inverters before , and this one seems out of the ordinary. It is an LTP (I think) , but there is a negative voltage on the cathode resistor R27 (marked as -3 voltage ), around -40v . Also the second grid on pin2 is grounded without an AC coupling capacitor , and there is a diode and resistor connected to the input which is explained in the manual by "GR3 in the grid circuit of B5 improves the RC time of coupling capacitor C18 and leak resistor R26 so that when Grid 7 of B5 becomes too far negative this charge can leak away faster through GR3"
The diode GR3 has a negative voltage (marked -2) on it , which is about -3 volts.
I want to put a Master Volume control before the Phase Inverter , so my questions are ...can I do so while still leaving the existing PI as it is without interfering with the function of G3 ? Should I replace the PI altogether ? I'm trying to keep the amp fairly original where I can , but maybe it doesn't make a great deal of difference here , and having the MV in this position is probably more important to me . Any help much appreciated.
I want to put a Master Volume control before the Phase Inverter , so my questions are ...can I do so while still leaving the existing PI as it is without interfering with the function of G3 ? Should I replace the PI altogether ? I'm trying to keep the amp fairly original where I can , but maybe it doesn't make a great deal of difference here , and having the MV in this position is probably more important to me . Any help much appreciated.
Abbado III NOS DAC with volume option
- By abraxalito
- Vendor's Bazaar
- 4 Replies
Orders are now open for Abbado III NOS DACs - DM me and be sure to mention your preferred payment method (Wise or Paypal) and location so I can quote you inclusive of fees and shipping. Abbado III is based on Abbado II architecturally but also includes an aspect of Celibidache's design hence is perhaps best seen as the merging of Celibidache and Abbado themes. Its DAC supply rails regulated by discrete transistors fed from IR LED voltage references but has a lower noise floor owing to the use of more paralleled TDA1545 DAC chips (24) and improved dynamics from a plug-in filter module which in stock form is 9th order (11th order by request). There is also the option to include an analog volume control to allow direct drive of a poweramp in systems with only digital sources. Use of an analog volume control beats a digital one in terms of SNR at lower listening levels. The physical footprint remains the same as Abbado II albeit slightly taller at 100mm * 70mm *24mm high - the fixing hole positions have moved though. We are using a 4 layer PCB and the DAC requires a single power rail of 9V at 270mA. Design wise, it's non-oversampling (i.e. there is no digital filter on-board) and the input format is I2S (three signal wire) at 44k1/16bits active within a 32bit frame. BCK is required to be 64fs (2.82MHz at 44k1 sample rate), MCK isn't required. Output is nominally 1.5VRMS with a 6dB gain reduction option on-board and a limited range of overall gain from a multi-turn trimmer. The gain reduction comes in handy when you want to use a pair of Abbados to create balanced outputs, the balanced output level can be kept the same as when unbalanced. In this configuration, the trimmer allows interchannel matching of output levels. Our I2S splitter board provides the functionality to run a pair of Abbados in balanced mode.
Preferred payment method is via Wise which typically adds a 2% fee. Our receiving currency is CNY, alternatively USD or Euro. PayPal may also be used, in USD but will attract higher fees, 5.5%.
Price for Abbado III built and tested, 9th order filter, with volume control : 1320RMB
11th order filter option : +120RMB
Omit volume control : -140RMB
Shipping is in addition and depends on your location and speed of service. Courier (FedEx, TNT, DHL) typically takes 8 - 10 days and e-packet four to eight weeks. Not all locations can be serviced by e-packet though.
FAQs
What else is needed to turn Abbado III into a fully operational DAC?
First, you'll need a well regulated low noise power supply of 9V rated at 270mA or higher. An LM317-based board set to the correct voltage will suffice if you already have an unregulated supply (like a typical wall-wart). The LM317 will need adequate heatsinking. I don't recommend switching supplies due to issues with common-mode noise, its very hard to filter out. That disrecommendation doesn't apply though when both the DAC and amp are within the same box as in our example below, in that case the CM noise isn't a worry. We have a suitable LM317-based board which takes in an AC feed from a mains transformer at 18V and down-regulates with a buck converter prior to the linear regulator. The use of the buck means it runs cool as the linear regulator is operated with just enough voltage drop to ensure good line rejection.
Second - you may need a digital interface card. I say 'may' because some digital sources produce I2S directly (like Raspberry Pi, dedicated SDcard players) but most sources will either output USB (like a PC or laptop) or S/PDIF coax (a CD or DVD player) or Toslink. We can supply a card for interfacing one (or more) of those sources to Abbado's I2S input. A CM6631A-based card for USB input is the premium choice as it operates under 'async USB' and offers up to 192k sample rates. However in stock form it isn't suitable because at 44.1kHz it outputs a 128fs BCK - when we supply such cards we upgrade the firmware for you to support a standard 64fs BCK. Async USB has the lowest jitter however given it operates under high-speed USB it needs a fairly expensive isolator to protect your DAC and amp from common-mode noise. A TE7022-based interface has the advantage of only needing a $5 full-speed USB isolator while still offering up to 96k sample rates and is normally cheaper than a CM6631A board. For S/PDIF inputs, the board we recommend handles both coax (two inputs) and Toslink. Further, it has a switched I2S input - this can accept I2S from the USB source. A single pole switch acts as source selector, cycling through the inputs. An OLED screen is an option to indicate the selected input. This board needs a 5-12V supply, so it is fine being run direct from the DAC's 9V rail.
Third you'll be wanting some output sockets, typically RCAs so you can connect your finished DAC to your amp or preamp. We can supply these and we also have a PCB to mount them to make outputting Abbado to your system easier. XLRs would be the recommended way to output in balanced mode.
Lastly, and this is obviously optional for a DIYer, is a case. We haven't supplied cases in the past because they're so heavy (i.e. expensive to ship).
USB CM6631A card examples : https://www.aliexpress.com/item/32874113831.html www.aliexpress.com/item/1005004083748180.html
TE7022 interface example : https://www.aliexpress.com/item/1005005388553366.html
USB isolator, full speed : https://www.aliexpress.com/item/1005001369085297.html
USB isolator, high speed : https://www.aliexpress.com/item/1005001379930133.html
Multi-input S/PDIF card : https://www.aliexpress.com/item/1005002923079600.html
Coax/Toslink S/PDIF card : https://www.aliexpress.com/item/1005002772984954.html
What's supplied with the DAC?
The inputs and outputs of Abbado use Molex type 2510 4pin connectors which mate with a shell containing crimp-terminated wires. We supply those wires pre-crimped with shells along with the DAC. If you buy an input board through us we'll also provide the I2S cable ready-made to suit that board. If you buy our PCB mounted RCAs we'll include the 4 wire cable to interface to that.
What, if anything, is unique about Abbado's design?
Commercial NOS DACs typically have minimal filtering after the DAC chip itself whereas Abbado has a steep (9th or 11th order) low-pass passive filter afterwards. By strongly attenuating the NOS image frequencies this LC filter improves dynamics and makes the aural picture more clearly delineated with acoustic instruments having a well defined position in space. Passive filters like this are extremely difficult to implement using off-the-shelf inductors as no commercially available ones have sufficiently close tolerance. So Abbado's inductors are custom, hand-wound using gapped ferrite P14 cores. Having a passive filter prior to any active analog stage means the downstream discrete buffer stage no longer 'sees' a step waveform out of the DAC chip, rather a continuous signal. The volume control option uses the lowest resistance ALPS pot available (5k) so as to add the least extra noise, its driven directly from the I/V resistor which is only possible because of the substantial output current from the array of TDA1545s. Abbado's DAC chips are 'multibit' but they're not strictly speaking 'R2R' as internally they use no resistors. Instead, capacitors are used as elements in the DAC which have their charge constantly refreshed (similar to the DRAM in your computer) to compensate for any drift. By paralleling 24 of these devices and running them at higher current levels than typically used, the noise floor is considerably lower than with a single chip - this translates in practice to a 'warmer' sound where the acoustic ambience captured on a recording is more easily perceived. In order to achieve retrieval of these low-level ambience cues, the DACs' power rails need to be extremely clean and this is achieved through use of a pair of discrete series regulators fed from an IR LED derived reference voltage.
The development of Abbado III has taken place over several years and it builds on and improves prior designs, most particularly it draws its heritage from Celibidache. While Celibidache used an array of 20 TDA1387s, Abbado swapped the DAC chips to TDA1545 because each chip has a 3dB improvement in SNR compared to TDA1387. Thus Celi's already black background has been darkened further. Celi used a pair of current sources to 'steer' the current into the I/V resistor whereas on Abbado I've been able to delete one of those CCSs with the aim of further lowering the noise. The last improvement over Celibidache has been made in the output stage - its now fully discrete whereas Celi used a very low noise opamp. The discrete nature of the output stage seems to contribute a more relaxed sound, particularly in the higher frequencies.
Abbado III is well-suited to the creation of a convenient 'all-in-one' box - aka a 'DAC-AMP' using its volume control option. Here's a picture of an Abbado (green PCB bottom right), minus filter to reveal the DAC array, in such a configuration. There are two power supplies - a 24V SMPSU top left for the amps (our own monoAMPs) and a hybrid linear-buck for the Abbado DAC. The input board (yellow colour bottom left) supports USB, Bluetooth and S/PDIF - switching of sources is done with a push-button on the front panel with LEDs for indication.
Preferred payment method is via Wise which typically adds a 2% fee. Our receiving currency is CNY, alternatively USD or Euro. PayPal may also be used, in USD but will attract higher fees, 5.5%.
Price for Abbado III built and tested, 9th order filter, with volume control : 1320RMB
11th order filter option : +120RMB
Omit volume control : -140RMB
Shipping is in addition and depends on your location and speed of service. Courier (FedEx, TNT, DHL) typically takes 8 - 10 days and e-packet four to eight weeks. Not all locations can be serviced by e-packet though.
FAQs
What else is needed to turn Abbado III into a fully operational DAC?
First, you'll need a well regulated low noise power supply of 9V rated at 270mA or higher. An LM317-based board set to the correct voltage will suffice if you already have an unregulated supply (like a typical wall-wart). The LM317 will need adequate heatsinking. I don't recommend switching supplies due to issues with common-mode noise, its very hard to filter out. That disrecommendation doesn't apply though when both the DAC and amp are within the same box as in our example below, in that case the CM noise isn't a worry. We have a suitable LM317-based board which takes in an AC feed from a mains transformer at 18V and down-regulates with a buck converter prior to the linear regulator. The use of the buck means it runs cool as the linear regulator is operated with just enough voltage drop to ensure good line rejection.
Second - you may need a digital interface card. I say 'may' because some digital sources produce I2S directly (like Raspberry Pi, dedicated SDcard players) but most sources will either output USB (like a PC or laptop) or S/PDIF coax (a CD or DVD player) or Toslink. We can supply a card for interfacing one (or more) of those sources to Abbado's I2S input. A CM6631A-based card for USB input is the premium choice as it operates under 'async USB' and offers up to 192k sample rates. However in stock form it isn't suitable because at 44.1kHz it outputs a 128fs BCK - when we supply such cards we upgrade the firmware for you to support a standard 64fs BCK. Async USB has the lowest jitter however given it operates under high-speed USB it needs a fairly expensive isolator to protect your DAC and amp from common-mode noise. A TE7022-based interface has the advantage of only needing a $5 full-speed USB isolator while still offering up to 96k sample rates and is normally cheaper than a CM6631A board. For S/PDIF inputs, the board we recommend handles both coax (two inputs) and Toslink. Further, it has a switched I2S input - this can accept I2S from the USB source. A single pole switch acts as source selector, cycling through the inputs. An OLED screen is an option to indicate the selected input. This board needs a 5-12V supply, so it is fine being run direct from the DAC's 9V rail.
Third you'll be wanting some output sockets, typically RCAs so you can connect your finished DAC to your amp or preamp. We can supply these and we also have a PCB to mount them to make outputting Abbado to your system easier. XLRs would be the recommended way to output in balanced mode.
Lastly, and this is obviously optional for a DIYer, is a case. We haven't supplied cases in the past because they're so heavy (i.e. expensive to ship).
USB CM6631A card examples : https://www.aliexpress.com/item/32874113831.html www.aliexpress.com/item/1005004083748180.html
TE7022 interface example : https://www.aliexpress.com/item/1005005388553366.html
USB isolator, full speed : https://www.aliexpress.com/item/1005001369085297.html
USB isolator, high speed : https://www.aliexpress.com/item/1005001379930133.html
Multi-input S/PDIF card : https://www.aliexpress.com/item/1005002923079600.html
Coax/Toslink S/PDIF card : https://www.aliexpress.com/item/1005002772984954.html
What's supplied with the DAC?
The inputs and outputs of Abbado use Molex type 2510 4pin connectors which mate with a shell containing crimp-terminated wires. We supply those wires pre-crimped with shells along with the DAC. If you buy an input board through us we'll also provide the I2S cable ready-made to suit that board. If you buy our PCB mounted RCAs we'll include the 4 wire cable to interface to that.
What, if anything, is unique about Abbado's design?
Commercial NOS DACs typically have minimal filtering after the DAC chip itself whereas Abbado has a steep (9th or 11th order) low-pass passive filter afterwards. By strongly attenuating the NOS image frequencies this LC filter improves dynamics and makes the aural picture more clearly delineated with acoustic instruments having a well defined position in space. Passive filters like this are extremely difficult to implement using off-the-shelf inductors as no commercially available ones have sufficiently close tolerance. So Abbado's inductors are custom, hand-wound using gapped ferrite P14 cores. Having a passive filter prior to any active analog stage means the downstream discrete buffer stage no longer 'sees' a step waveform out of the DAC chip, rather a continuous signal. The volume control option uses the lowest resistance ALPS pot available (5k) so as to add the least extra noise, its driven directly from the I/V resistor which is only possible because of the substantial output current from the array of TDA1545s. Abbado's DAC chips are 'multibit' but they're not strictly speaking 'R2R' as internally they use no resistors. Instead, capacitors are used as elements in the DAC which have their charge constantly refreshed (similar to the DRAM in your computer) to compensate for any drift. By paralleling 24 of these devices and running them at higher current levels than typically used, the noise floor is considerably lower than with a single chip - this translates in practice to a 'warmer' sound where the acoustic ambience captured on a recording is more easily perceived. In order to achieve retrieval of these low-level ambience cues, the DACs' power rails need to be extremely clean and this is achieved through use of a pair of discrete series regulators fed from an IR LED derived reference voltage.
The development of Abbado III has taken place over several years and it builds on and improves prior designs, most particularly it draws its heritage from Celibidache. While Celibidache used an array of 20 TDA1387s, Abbado swapped the DAC chips to TDA1545 because each chip has a 3dB improvement in SNR compared to TDA1387. Thus Celi's already black background has been darkened further. Celi used a pair of current sources to 'steer' the current into the I/V resistor whereas on Abbado I've been able to delete one of those CCSs with the aim of further lowering the noise. The last improvement over Celibidache has been made in the output stage - its now fully discrete whereas Celi used a very low noise opamp. The discrete nature of the output stage seems to contribute a more relaxed sound, particularly in the higher frequencies.
Abbado III is well-suited to the creation of a convenient 'all-in-one' box - aka a 'DAC-AMP' using its volume control option. Here's a picture of an Abbado (green PCB bottom right), minus filter to reveal the DAC array, in such a configuration. There are two power supplies - a 24V SMPSU top left for the amps (our own monoAMPs) and a hybrid linear-buck for the Abbado DAC. The input board (yellow colour bottom left) supports USB, Bluetooth and S/PDIF - switching of sources is done with a push-button on the front panel with LEDs for indication.
For Sale Abbas Audio tube DEM clock for TDA1540/TDA1541
- By Geluidloopt
- Swap Meet
- 2 Replies
Attachments
How to match the volume of two channels
- By Pirotex2005
- Electronic Design
- 7 Replies
There is a 2 way mono crossover diagram. In the lower part, the output stage is responsible for generating a bass boost when turning the volume knob (like tone compensation)
The problem is that both channels are not synchronous. The HF channel is quieter with the same potentiometer position.
How can this be compensated and both channels synchronized?
Attached file for microcap
The problem is that both channels are not synchronous. The HF channel is quieter with the same potentiometer position.
How can this be compensated and both channels synchronized?
Attached file for microcap
LM78xx voltage regulator noise reduction by 30 dB
- By MagicianT
- Electronic Design
- 12 Replies
Simple circuits to reduce noise of common LM78xx voltage regulators.
Updates:
1. Turns out that LM7805 doesn't start up reliable in this configuration, and thread name difficult to change. It happens if 5 * Iq rules is broken, so there is another version:
2. Basic concept, that helps to understand role of a regulator as "pass element"
Some test results with 3v3 and 5v6 zeners:
Scale is referenced to 3 nV-rms at -140 dB line.
So the best performance I've got so far using lm7805 & 5v6, about 7 nV-rms. It's interesting, as I know that 5.6V zener noisier than 3v3, but high dynamic resistance of 3v3 (70 Ohms vs 5 Ohms) limits the gain of bjt. Option may be to use 2 bjt or some OPA, if I decide to push noise down.
Updates:
1. Turns out that LM7805 doesn't start up reliable in this configuration, and thread name difficult to change. It happens if 5 * Iq rules is broken, so there is another version:
2. Basic concept, that helps to understand role of a regulator as "pass element"
Some test results with 3v3 and 5v6 zeners:
Scale is referenced to 3 nV-rms at -140 dB line.
So the best performance I've got so far using lm7805 & 5v6, about 7 nV-rms. It's interesting, as I know that 5.6V zener noisier than 3v3, but high dynamic resistance of 3v3 (70 Ohms vs 5 Ohms) limits the gain of bjt. Option may be to use 2 bjt or some OPA, if I decide to push noise down.
Tymphany DFM-2535-R00-08 in SB Audience H225 90x60 degree constant directivity horn
I thought I would share some measurements of this Tymphany/Peerless DFM-2535-R00-08 1.4" voice coil, 1" exit titanium compression driver with ferrite magnet
Here's the spec sheet, retrieved 01/08/2024 shows the response in a Plane Wave Tube @0.283V:
As well as in a horn:
N.B. The left vertical axis denotes 2.83V/1m ("with LTH102 test horn")... A web search shows... is this the FaitalPRO LTH102 horn ?
Since Tymphany don’t make their own horns (AFAIK), I mounted it onto a SB Audience H225 , a 225mm square 90x70 degree constant directivity horn.
It needs four M6 x 16mm bolts to mount directly only the horn- no modifications or adaptor required:
Now we measure at 0.5m (to reduce reflections in from floor/ceiling) but plot for 1m (-6dB) in the "standard" 25dB/decade aspect ratio, from 600Hz to 40KHz:
Here are the polar measurements, taken in 10 degree steps, in both the Horizontal and Vertical axis from 0-90 degrees.
This is with a gentle 1V RMS drive level so measurements could be taken down to 500Hz, but SPL plotted for 1m.
The gating is 4ms, so the frequency resolution is approximated below 1KHz.
Here's the polar response, with 1dB demarcations.
Next we use software DSP to flatten with on-axis frequency response and insert a filter for acoustic LR4 1KHz:
86dB@1m seems to be a walk in the park- all harmonics below noise floor of this room:
Here is 96dB , this time with crossover for 800Hz (see post 17)
STRETCH GOAL:
106dB/m
Edit:
01/08/2024 - tidied up. B&W for some, colors for others!
Here's the spec sheet, retrieved 01/08/2024 shows the response in a Plane Wave Tube @0.283V:
As well as in a horn:
N.B. The left vertical axis denotes 2.83V/1m ("with LTH102 test horn")... A web search shows... is this the FaitalPRO LTH102 horn ?
Since Tymphany don’t make their own horns (AFAIK), I mounted it onto a SB Audience H225 , a 225mm square 90x70 degree constant directivity horn.
It needs four M6 x 16mm bolts to mount directly only the horn- no modifications or adaptor required:
Now we measure at 0.5m (to reduce reflections in from floor/ceiling) but plot for 1m (-6dB) in the "standard" 25dB/decade aspect ratio, from 600Hz to 40KHz:
Here are the polar measurements, taken in 10 degree steps, in both the Horizontal and Vertical axis from 0-90 degrees.
This is with a gentle 1V RMS drive level so measurements could be taken down to 500Hz, but SPL plotted for 1m.
The gating is 4ms, so the frequency resolution is approximated below 1KHz.
Here's the polar response, with 1dB demarcations.
Next we use software DSP to flatten with on-axis frequency response and insert a filter for acoustic LR4 1KHz:
86dB@1m seems to be a walk in the park- all harmonics below noise floor of this room:
Here is 96dB , this time with crossover for 800Hz (see post 17)
STRETCH GOAL:
106dB/m
Edit:
01/08/2024 - tidied up. B&W for some, colors for others!
For Sale Bigbottle phonostage PCB and Valves. Brand New
Hi all,
I recently refunded a gentleman who purchased this kit. He's had a health diagnosis that means HiFi is no longer a priority and this became a project he was no longer going to pursue
Unused PCB and Unused NOS/Brand New Valves, £365 Inc shipping.
Valves: 2X Colmore PCC88s and 1x PS VANE gold pin ECC83.
I recently refunded a gentleman who purchased this kit. He's had a health diagnosis that means HiFi is no longer a priority and this became a project he was no longer going to pursue
Unused PCB and Unused NOS/Brand New Valves, £365 Inc shipping.
Valves: 2X Colmore PCC88s and 1x PS VANE gold pin ECC83.
DIY Schroeder Tonearm?
- By mgreene
- Analogue Source
- 1626 Replies
With all the recent talk about unipivots and such, has no one ever considered knocking off a magnet stabilized string pivot like the Schroeder? I have been considering a DIY arm just to add a mono cartridge to my TT. This implementation "looks" fairly simple 
Assuming you have a source of wood and carbon fibre, the only things slightly out of the ordinary are the neodium magnets, which are fairly ubiquitous on the web.
See pics and a review of the Schroeder's stuff at his website: http://www.schroeder-tonarme.de/
Mike
Assuming you have a source of wood and carbon fibre, the only things slightly out of the ordinary are the neodium magnets, which are fairly ubiquitous on the web.See pics and a review of the Schroeder's stuff at his website: http://www.schroeder-tonarme.de/
Mike
The greatest advantage of Full-Range speakers
- By nandappe
- Full Range
- 129 Replies
The greatest advantage of full-range speakers, in my opinion, is their ability to extend vocal fortissimo naturally.
General multiway speakers (with LCR networks) often fail to reproduce the same open and extended vocals as full-range speakers.
Even high-end multiway speakers can sometimes make fortissimo passages sound compressed.
I asked ChatGPT a question
[QUESTION]
Why do multiway speakers (with LCR network) have poor vocal fortissimo extension compared to full-range speakers?
[ANSWER]
Multiway speakers with an LCR network (inductor-capacitor-resistor) often have poorer vocal fortissimo extension compared to full-range speakers due to several factors related to crossover design, phase issues, and driver limitations. Here’s why:
### 1. Crossover-Induced Energy Loss & Damping
- Multiway speakers rely on crossovers to split frequencies among drivers. These passive LCR networks introduce energy losses due to component resistance and impedance mismatches, reducing transient response and dynamic range.
- Inductors in the midrange and woofer circuits can limit the rise time of transients, making fortissimo passages sound less explosive.
- Some crossovers over-damp the midrange, making vocals sound compressed compared to full-range speakers.
### 2. Phase Shift & Time Alignment Issues
- Crossovers introduce phase shifts, especially around crossover points, which can cause destructive interference and loss of coherence in loud vocal peaks.
- In a full-range speaker, the entire signal comes from a single driver, avoiding phase misalignment that can soften high-energy transients.
### 3. Driver Interaction & Compression
- In multiway speakers, multiple drivers (midrange & tweeter) attempt to reproduce vocal harmonics, but integration issues can cause cancellation effects or uneven dispersion at high SPLs.
- Multiway drivers often have different efficiency levels, leading to uneven power handling during loud peaks.
- Some midrange drivers have limited excursion, causing dynamic compression at high SPLs, whereas full-range drivers are designed to handle the entire vocal range without a handoff.
### 4. Cohesion & Direct Radiator Effect
- Full-range drivers radiate sound from a single point, ensuring phase coherence and direct radiating energy, leading to a more natural projection of vocal intensity.
- Multiway systems introduce lobing effects (interference between separated drivers), which can reduce perceived vocal presence at high volumes.
### 5. LCR Network Damping Effects
- The impedance of a crossover network interacts with the amplifier’s output impedance, sometimes reducing the damping factor and affecting transient sharpness.
- In contrast, full-range drivers typically run with minimal or no crossover components, allowing for direct amplifier-to-driver coupling and faster transient response.
### Why Full-Range Speakers Perform Better in Vocal Fortissimo
- No crossover-induced phase shifts or energy losses.
- A single diaphragm handling the entire frequency range ensures better coherence.
- Direct coupling to the amplifier maximizes transient response.
- No multi-driver interference or lobing effects.
This is why single-driver, full-range speakers are often preferred for vocal reproduction, especially in high-dynamic passages like operatic or live performances.
-----------------------------------------------------------
[ Air-Recording ]
"Danny Boy - Jacinta" listened to with 1.5” full-range (1.5 USD) and Bluetooth Amplifier (6.5 USD)
Login to view embedded media
General multiway speakers (with LCR networks) often fail to reproduce the same open and extended vocals as full-range speakers.
Even high-end multiway speakers can sometimes make fortissimo passages sound compressed.
I asked ChatGPT a question
[QUESTION]
Why do multiway speakers (with LCR network) have poor vocal fortissimo extension compared to full-range speakers?
[ANSWER]
Multiway speakers with an LCR network (inductor-capacitor-resistor) often have poorer vocal fortissimo extension compared to full-range speakers due to several factors related to crossover design, phase issues, and driver limitations. Here’s why:
### 1. Crossover-Induced Energy Loss & Damping
- Multiway speakers rely on crossovers to split frequencies among drivers. These passive LCR networks introduce energy losses due to component resistance and impedance mismatches, reducing transient response and dynamic range.
- Inductors in the midrange and woofer circuits can limit the rise time of transients, making fortissimo passages sound less explosive.
- Some crossovers over-damp the midrange, making vocals sound compressed compared to full-range speakers.
### 2. Phase Shift & Time Alignment Issues
- Crossovers introduce phase shifts, especially around crossover points, which can cause destructive interference and loss of coherence in loud vocal peaks.
- In a full-range speaker, the entire signal comes from a single driver, avoiding phase misalignment that can soften high-energy transients.
### 3. Driver Interaction & Compression
- In multiway speakers, multiple drivers (midrange & tweeter) attempt to reproduce vocal harmonics, but integration issues can cause cancellation effects or uneven dispersion at high SPLs.
- Multiway drivers often have different efficiency levels, leading to uneven power handling during loud peaks.
- Some midrange drivers have limited excursion, causing dynamic compression at high SPLs, whereas full-range drivers are designed to handle the entire vocal range without a handoff.
### 4. Cohesion & Direct Radiator Effect
- Full-range drivers radiate sound from a single point, ensuring phase coherence and direct radiating energy, leading to a more natural projection of vocal intensity.
- Multiway systems introduce lobing effects (interference between separated drivers), which can reduce perceived vocal presence at high volumes.
### 5. LCR Network Damping Effects
- The impedance of a crossover network interacts with the amplifier’s output impedance, sometimes reducing the damping factor and affecting transient sharpness.
- In contrast, full-range drivers typically run with minimal or no crossover components, allowing for direct amplifier-to-driver coupling and faster transient response.
### Why Full-Range Speakers Perform Better in Vocal Fortissimo
- No crossover-induced phase shifts or energy losses.
- A single diaphragm handling the entire frequency range ensures better coherence.
- Direct coupling to the amplifier maximizes transient response.
- No multi-driver interference or lobing effects.
This is why single-driver, full-range speakers are often preferred for vocal reproduction, especially in high-dynamic passages like operatic or live performances.
-----------------------------------------------------------
[ Air-Recording ]
"Danny Boy - Jacinta" listened to with 1.5” full-range (1.5 USD) and Bluetooth Amplifier (6.5 USD)
Login to view embedded media
Attachments
The Incredible Technics SP-10 Thread
- By 6L6
- Analogue Source
- 3105 Replies
EDIT: (many years later...)
Putting a couple amazing links here in the top so members can better find them;
Mike Barney's page, which in my opinion is the best single SP-10 page out there -
https://sites.google.com/site/mpbarneysources/sp-10-mk2-pro
A great rebuild thread on AK -
https://audiokarma.org/forums/index.php?threads/technics-sp-10mkii-restoring-an-icon.900468/
JP's storefront -
https://fidelisanalog.com
Amazing SP-10 content here -
https://www.theanalogdept.com/sp10-gal.html
(The funny widgets are the motor hub fixing plates)
No, you are not seeing double.
This is my newest and most ambitious project yet - Technics SP-10Mk2A. Neither have a PSU, but that's not a difficult thing. Happily, both are operational, I tested them today with a friend's PSU. One has a fiddly main switch. Both are in sorrier cosmetic shape than I thought. That may prove an issue, only time will tell.
So will I make one good one from the ashes of two? I have no idea yet. Of course, having two at the end of this is always more attractive of an option. I do, however, think I may make one black, that would look quite sharp.
On the to-do list -
Re-cap the main board.
Build PSU
Adjust main board and switches as needed.
Figure out if I have one good table or two.
Build plinth(s).
Address cosmetic issues.
Determine if I can get a long armwand for my Graham, or just get a 10.5" Jelco.
Etc...
So let's get started --
Like I mentioned, both tables are operative, the biggest concerns (other than the need to build PSUs for both) is purely cosmetic.
So let's look at the tables as I received them. These photos intentionally are showing all the warts as ugly as possible.
The prettier one. Not bad generally, but the marring and corrosion is all on the 'close' side of the table where it will be seen.
The text can be re-filled. the corrosion is fairly shallow.
A couple of nicks in the black paint. No big deal.
Marring on the paint, no corrosion.
Inside the brake section is very clean, and there is plenty of friction material (felt) on the band.
I have no idea if this is a lot of wear or not on the hub. I thought it worth a photo, to see if anybody can compare.
The platter of the prettier one.
A bit of corrosion, nothing severe at all.
The stock platter mat had something glued to it. I have no idea hot to get a hard adhesive residue removed from rubber...
Putting a couple amazing links here in the top so members can better find them;
Mike Barney's page, which in my opinion is the best single SP-10 page out there -
https://sites.google.com/site/mpbarneysources/sp-10-mk2-pro
A great rebuild thread on AK -
https://audiokarma.org/forums/index.php?threads/technics-sp-10mkii-restoring-an-icon.900468/
JP's storefront -
https://fidelisanalog.com
Amazing SP-10 content here -
https://www.theanalogdept.com/sp10-gal.html
(The funny widgets are the motor hub fixing plates)
No, you are not seeing double.
This is my newest and most ambitious project yet - Technics SP-10Mk2A. Neither have a PSU, but that's not a difficult thing. Happily, both are operational, I tested them today with a friend's PSU. One has a fiddly main switch. Both are in sorrier cosmetic shape than I thought. That may prove an issue, only time will tell.
So will I make one good one from the ashes of two? I have no idea yet. Of course, having two at the end of this is always more attractive of an option. I do, however, think I may make one black, that would look quite sharp.
On the to-do list -
Re-cap the main board.
Build PSU
Adjust main board and switches as needed.
Figure out if I have one good table or two.
Build plinth(s).
Address cosmetic issues.
Determine if I can get a long armwand for my Graham, or just get a 10.5" Jelco.
Etc...
So let's get started --
Like I mentioned, both tables are operative, the biggest concerns (other than the need to build PSUs for both) is purely cosmetic.
So let's look at the tables as I received them. These photos intentionally are showing all the warts as ugly as possible.
The prettier one. Not bad generally, but the marring and corrosion is all on the 'close' side of the table where it will be seen.
The text can be re-filled. the corrosion is fairly shallow.
A couple of nicks in the black paint. No big deal.
Marring on the paint, no corrosion.
Inside the brake section is very clean, and there is plenty of friction material (felt) on the band.
I have no idea if this is a lot of wear or not on the hub. I thought it worth a photo, to see if anybody can compare.
The platter of the prettier one.
A bit of corrosion, nothing severe at all.
The stock platter mat had something glued to it. I have no idea hot to get a hard adhesive residue removed from rubber...
Which horn model is this?
Does anyone recognise this horn model - it is roughly 12-12,5" opening for a 1.4 inch driver.
Oneminde
Oneminde
12 V trigger from a Raspberry Pi, using step-up converter
Hi. I got a small amp with 12 V trigger in (3.3 or 5V will not do) and a Raspberry Pi 4B with a dac hat and running camilladsp and a USB gadget mode, UAC. Works well enough so that I want to make use of the 12 V trigger. The problem is that I'm a newbie with low level electronics, although I have some basic understanding on how things work. I have also assembled diy duplos (Hypex NC400 kits) and they work well. I asked ChatGPT, but it gave conflicting answers. I need a human confirmation so that I won't fry my devices.
I now know that the 12 V and 3.3 V rails on the Pi have good current output so that they can easily handle trigger signal through a step-up converter (that I have) and some other small components. However those rails cannot be controlled with software, they are always on. The togglable GPIO pins supply 3.3 V, but very little current. Less than 20 mA I think. The AI gave two possible solutions.
1) A relay: 5V -> relay -> step-up -> amp, control relay by a GPIO pin. I don't have such relay, but there should be RPi/Arduino compatible relays available everywhere.
2) Using an NPN transistor or a MOSFET. I happen to have a small electronics kit that came with TO-92 (?) packaged NPN transistors that are labeled as "PN2222". AI says they're good. Print on the actual component says "2N 2222A -1726". The guide goes like this:
This result conflicts with what the AI was telling for legs. With the flat side of the transistor facing me (down in the pic), the legs should be from left to right: EBC, right? It's difficult to see in the pic, but that's how they go into the testers numbered slots. Anyway I see the letters NPN, so it's correct type?
Low power consumption is a requirement, because I'm on USB 2 power budget and I got other devices to connect too. At this point I feel like the relay would be a better idea, but I kind of hoped to make with stuff that I already have. What say you?
PS. I'm also developing UI with a small OLED screen and a rotary encoder, but this trigger is higher on my priority.
I now know that the 12 V and 3.3 V rails on the Pi have good current output so that they can easily handle trigger signal through a step-up converter (that I have) and some other small components. However those rails cannot be controlled with software, they are always on. The togglable GPIO pins supply 3.3 V, but very little current. Less than 20 mA I think. The AI gave two possible solutions.
1) A relay: 5V -> relay -> step-up -> amp, control relay by a GPIO pin. I don't have such relay, but there should be RPi/Arduino compatible relays available everywhere.
2) Using an NPN transistor or a MOSFET. I happen to have a small electronics kit that came with TO-92 (?) packaged NPN transistors that are labeled as "PN2222". AI says they're good. Print on the actual component says "2N 2222A -1726". The guide goes like this:
- transistor emitter to ground
- 5V supply pin to transistor collector
- 10 kOhm resistor between transistor base and ground
- selected GPIO pin to transistor base through 1 kOhm resistor, this is the programmatically controlled pin for toggling on/off
- ground to step-up converter in-
- transistor collector to step-up converter in+
- when GPIO pin is high (3.3 V), it should allow current flow to the step-up converter and produce me 12 V trigger (when voltage is adjusted correctly).
This result conflicts with what the AI was telling for legs. With the flat side of the transistor facing me (down in the pic), the legs should be from left to right: EBC, right? It's difficult to see in the pic, but that's how they go into the testers numbered slots. Anyway I see the letters NPN, so it's correct type?
Low power consumption is a requirement, because I'm on USB 2 power budget and I got other devices to connect too. At this point I feel like the relay would be a better idea, but I kind of hoped to make with stuff that I already have. What say you?
PS. I'm also developing UI with a small OLED screen and a rotary encoder, but this trigger is higher on my priority.
Basic Power Amplifier Retro
- By lineup
- Solid State
- 54 Replies
A basic power amplifier delivering more than 16 Watt.
An amplifier that could be before D.Self published his Blameless.
The THD distortion is moderate, but the harmonics are interesting. Mostly 2nd harmonic.
Enjoy this simple amp!
An amplifier that could be before D.Self published his Blameless.
The THD distortion is moderate, but the harmonics are interesting. Mostly 2nd harmonic.
Enjoy this simple amp!
Power amp design by Zbig with new compensation method
- By Zbig
- Solid State
- 69 Replies
I'd like to present my project of power amplifier with novelty (I hope) gain-frequency compensation, and some other tricks resulting with high amplifier gain and very low THD.
Everybody knows most common method of making amplifier stable – it is Miller compensation: capacitor put between output and inverting input of amplifier (across one or more of amplifier’s stages). This simply puts dominant pole at very low frequency producing well known phase-amplitude open loop response of the amplifier, when high gain is flat to frequencies at most hundreds of Hertz (first, dominant pole), and then fall monotonically in 6dB per octave till unity gain.
My solution allows for very high and almost flat gain till almost 1 kilohertz, and then steep but controlled slope and phase till unity gain, where phase margin is above 45 degrees, and Nyquist stability criteria is fully met, even with capacitive load.
Compensation is done by a low pass filter between amplifier's stages with one pole and one zero. This is enough to make amplifier stable, but to increase phase margin I've added small forward compensation and also small Miller compensation with pole beyond low pass filter and zero before unity gain.
All amplifier design is kept as simple as possible, without unnecessary items (like mosfet drivers). I've only left resistors in MOSFET's sources, but only for further shortcut/overcurrent protection.
Finally I’ve got these numbers:
100W 8 Ohm.
115dB maximum open loop gain (with feedback network, amplifier alone has 147dB gain), first pole at 800Hz
111dB gain at 1kHz
92dB gain at 10kHz
Closed loop gain 32dB (40V/V)
Slew rate 47V/us
10MHz unity gain, with phase margin 62 degree and amplitude margin 10dB
1W 1kHz THD=0,000007%
100W 1kHz THD=0.000035%
Thermal stability (-12% quiescent current at 150 degree Celsius)
NOTE: this is so far LTSpice simulation, but I’ve choosen pats which are cheap, still in production and available everywhere. I’m going to make this amplifier and test it.
Here are some pictures,
Phase-amplitude characteristics
And this same with capacitive load
THD numbers for 1W 1kHz
Fourier for 1kHz 1W
Intermodulation FFT (9kHz+10kHz 8Vpp out)
LTspice do not shows much, so I've put numbers to Excel and produce more legible graph (horizontally kilohertz, vertically dB)
Step response with overdrive. As you see it lasts less than microsecond to stabilize output level
This same step but with input low pass filter (no overdrive with full power 10kHz square wave)
Noise figure
Thermal stability
And finally schematics
This is not a final version, and some improvements should be done, e.g. increase clipping output voltage, and gate protection.
Everybody knows most common method of making amplifier stable – it is Miller compensation: capacitor put between output and inverting input of amplifier (across one or more of amplifier’s stages). This simply puts dominant pole at very low frequency producing well known phase-amplitude open loop response of the amplifier, when high gain is flat to frequencies at most hundreds of Hertz (first, dominant pole), and then fall monotonically in 6dB per octave till unity gain.
My solution allows for very high and almost flat gain till almost 1 kilohertz, and then steep but controlled slope and phase till unity gain, where phase margin is above 45 degrees, and Nyquist stability criteria is fully met, even with capacitive load.
Compensation is done by a low pass filter between amplifier's stages with one pole and one zero. This is enough to make amplifier stable, but to increase phase margin I've added small forward compensation and also small Miller compensation with pole beyond low pass filter and zero before unity gain.
All amplifier design is kept as simple as possible, without unnecessary items (like mosfet drivers). I've only left resistors in MOSFET's sources, but only for further shortcut/overcurrent protection.
Finally I’ve got these numbers:
100W 8 Ohm.
115dB maximum open loop gain (with feedback network, amplifier alone has 147dB gain), first pole at 800Hz
111dB gain at 1kHz
92dB gain at 10kHz
Closed loop gain 32dB (40V/V)
Slew rate 47V/us
10MHz unity gain, with phase margin 62 degree and amplitude margin 10dB
1W 1kHz THD=0,000007%
100W 1kHz THD=0.000035%
Thermal stability (-12% quiescent current at 150 degree Celsius)
NOTE: this is so far LTSpice simulation, but I’ve choosen pats which are cheap, still in production and available everywhere. I’m going to make this amplifier and test it.
Here are some pictures,
Phase-amplitude characteristics
And this same with capacitive load
THD numbers for 1W 1kHz
Fourier for 1kHz 1W
Intermodulation FFT (9kHz+10kHz 8Vpp out)
LTspice do not shows much, so I've put numbers to Excel and produce more legible graph (horizontally kilohertz, vertically dB)
Step response with overdrive. As you see it lasts less than microsecond to stabilize output level
This same step but with input low pass filter (no overdrive with full power 10kHz square wave)
Noise figure
Thermal stability
And finally schematics
This is not a final version, and some improvements should be done, e.g. increase clipping output voltage, and gate protection.
Attachments
Understand & clone Larsen 8
A few of you know that I have a strong interest in developing a modest cost speaker system that sounds good placed against the wall. Coming from successfully cloned Linkwitz LX521 & also original spec Linkwitz Orions, this might be a tall order, as full-bandwidth dipole imaging is difficult to replicate. I started a thread/project to combine quarter sphere (pi) bass with dipole mid/highs a while ago. That effort morphed after an acceptance of defeat, into an examination of the Linkwitz LXmini -- which I made a variant of using different drivers & construction. The resulting pentagon tower is actually a good sounding inexpensive speaker (not including the cost of 4-ch amp and 2x4 HD) but still needs the 3-4' distance from the front wall to achieve ideal performance.
I'm still trying to figure out how to get the consistent bass response of a near-wall floor stander with excellent imaging.
Yesterday, I came across the Larsen speakers.
This is a loudspeaker line that comes from the Ortho Acoustic concepts of Stig Carlsson & John Larsen. Larsen's about page provides a summary.
The Larsen 4, 6, 8 & 9 are all smallish floor-standing mirror-image pairs designed for close-wall placement. Each features a mid/treble panel atop the tower that's angled up and inward. It looks like 45 degree in both planes. The large 8 & 9 models feature an additional side firing woofer close to the intersection of floor and wall, like the NHT 2.9 I once owned & inspired me. This config is certain to increase the perceived bass output in most rooms.
A collection of reviews applauds their ability to reproduce music well, predictably, consistently. These are keywords for me!
I haven't gone through them all but these reviews stand out:
Joe N Tell on Larsen 4
Absolute Sound on model 8
Absolute Sound on model 9
Positive Feedback on model 8
The best detailed pics on fairaudio.de
At first glance, it seems eminently feasible to replicate the basic design of the Larsen speaker in a pentagon tower -- a shape I have come to quite appreciate having built LXmini-ish pentagon towers. But before I embark on another project, I must ask --
1. Does anyone here have hands on (ears on?) experience with any of the Larsen speakers? Surely some of the Scandinavians here. I doubt I will find any here in Western Canada. Can you please share your experience?
2. Has someone already tried to replicate any of the Larsen speakers? Again, please share.
Thanks for your attention!
I'm still trying to figure out how to get the consistent bass response of a near-wall floor stander with excellent imaging.
Yesterday, I came across the Larsen speakers.
This is a loudspeaker line that comes from the Ortho Acoustic concepts of Stig Carlsson & John Larsen. Larsen's about page provides a summary.
The Larsen 4, 6, 8 & 9 are all smallish floor-standing mirror-image pairs designed for close-wall placement. Each features a mid/treble panel atop the tower that's angled up and inward. It looks like 45 degree in both planes. The large 8 & 9 models feature an additional side firing woofer close to the intersection of floor and wall, like the NHT 2.9 I once owned & inspired me. This config is certain to increase the perceived bass output in most rooms.
A collection of reviews applauds their ability to reproduce music well, predictably, consistently. These are keywords for me!
I haven't gone through them all but these reviews stand out:
Joe N Tell on Larsen 4
Absolute Sound on model 8
Absolute Sound on model 9
Positive Feedback on model 8
The best detailed pics on fairaudio.de
At first glance, it seems eminently feasible to replicate the basic design of the Larsen speaker in a pentagon tower -- a shape I have come to quite appreciate having built LXmini-ish pentagon towers. But before I embark on another project, I must ask --
1. Does anyone here have hands on (ears on?) experience with any of the Larsen speakers? Surely some of the Scandinavians here. I doubt I will find any here in Western Canada. Can you please share your experience?
2. Has someone already tried to replicate any of the Larsen speakers? Again, please share.
Thanks for your attention!
Dynaco ST-35 Hum in One Channel
- By MarkC568
- Tubes / Valves
- 22 Replies
I picked up this ST-35 locally last July. Installed a matched set of NOS Reflector tubes shortly after purchase. Sounds amazing, with incredible atmosphere and texture, with a nearly silent background.
Over the last week or so it's started developing a hum in the right channel. I've swapped channels on all the tubes, but the hum remains on the right channel.
Any recommendations on what to start checking/testing?
Over the last week or so it's started developing a hum in the right channel. I've swapped channels on all the tubes, but the hum remains on the right channel.
Any recommendations on what to start checking/testing?