USSA-5 build and review:

Amplifier Design/layout: Fab (The Great and Powerful Ape)

Amplifer PCB Layout: Alex

PSU Design/Layout: Project16

PSU PCB Production: Prasi


I couldn't stop thinking about this amplifier. The obsession began with a few fleeting traces of it's existence. The few members that have actually completed it were mostly silenced by its greatness. When I had enquired about it, people simply said "Oh, the USSA-5? It's the best amp I've ever heard."

I had to build it. But, the great mind that designed the amp wasn't going to just give me the boards. I offered to build a children's wing at his nearest hospital in his name. He said no. I said I would make huge donations to wildlife preserves around the world. He still said no. He was like talking to Willy Wonka and I was Charlie Bucket. I needed a golden ticket....

In the end, what worked was honesty and a promise to do two things: to build the amplifier and write a review.

So, here it is.

Last of my DIY parts

Bundle of Soekris two R2R DAC boards with many kits and accessories
this bundle includes:
1 - Soekris DAM 1021-02
This is new and tested confirmed working 100%. comes in original box from soekris with molex connectors, the USB cable to pragram the firmware and Neutrik XLR connectors are new and perfect. these are the pictures: Login to view embedded media
2 - Soekris DAM 1021-01
this is the one that is installed in the box. i have used this for coax and usb input a lot and sounded glorious. pictures below

3 - AMANERO USB ITS INSTALLED IN THE BOX,. pictures below

4 - AZ OLED lite Green color
this is perfect and tested. it is installed in the box. picrues below.

5 - Normundss kit for soekris 1021
here are the pictures:


6- the aluminum box with vu meters. this is an awesome box and i prefer to keeep it. it is complete and i have all parts and will be included

Things that i still have for sale: Login to view embedded media
1 - the linear power supply has really good and expensive and like new capacitors. the transformer is antek As 0509. this is free if you buy everything.

2 - Dayton audio 6.5 inch designer series woofer. quantity = 3. two are tested and like new and have solder residue. one is new. https://www.parts-express.com/Dayton-Audio-DS175-8-6-1-2-Designer-Series-Woofer-295-428?quantity=1

3 - Dayton measurement mic with calibration gragh. new https://www.parts-express.com/Dayto...1Qb6g07lZP4sLsTooJmKa1ABDgWreSYcaAtHpEALw_wcB

4 - pair of peerless tweeters NEW
https://www.parts-express.com/Peerl...50U221j7tfuh5fhWG-HswPDSEVg4XRFAaAo4GEALw_wcB

all together $155 paypal friends and family
weight is almost 20 pounds for the whole thing

If anybody has a surplus pcb for pcm63 dac, please let me know.
From Miro for example, the ordinary one, or some other.

It can be empty, half finished or finished and with or without dac chips.

Tnx. 🙂

Roederstein draloric 0.60w resistor

I heard these speakers by someone who tried to build Dunlavy SC V1 clone type speakers. They used two Focal Audiom 15 inch woofers. The model number for the woofers were 15VX. These were top of the line Focal Audio 15 inch woofers, 2 Focal Polyglass midbases. The model number for the midbase was 7K6411 and a Raven R2 ribbon tweeter.
The speakers were about 6 feet tall and weighed 335 pounds.

They speakers had a nice soundstage and the bass was tight with good extension. These woofers were very impressive.
Now, he couldn't do a crossover like Dunlavy. Dunlavy could make speakers that used ok drivers, but make the speakers sound great.

I remember i heard the Dunlavy SC-IV speakers that used all Vifa drivers. These speakers had an amazing soundstage and sounded very layered and the bass was fast and tight. I always though what could Dunlavy have designed using top of the line drivers like Focal at the time or Scanspeak.

Here's a pic of the speakers he designed.

Fourteen days ago, on October 1st, Wayne Colburn presented his Pearl 3 phonostage design at the 2023 Burning Amp Festival. Today I'd like to unveil "UDP3", a PCB which makes it relatively straightforward to build an external power supply for Pearl 3, in a separate chassis, connected by an umbilical cord. A few reasons why builders might wish to put Pearl 3's DC supply in its own box, include:

• This lets you move the mains transformer far away from the sensitive Pearl 3 PCBs. Greater separation gives greater isolation.
• The external PSU chassis provides an electrostatic and electromagnetic shielding box, surrounding the mains transformer. This dramatically reduces noise radiated from the mains transformer and wiring.
• If desired, you can build an additional box-within-a-box, thereby double shielding the mains transformer. You don't have to worry whether the extra size and volume of the second box will intrude upon the Pearl 3 phonostage PCBs.

The UDP3 board (Umbilical Cable Driver for Pearl 3) is shown below. It requires a dual secondary power transformer (2 x 22VAC RMS) which is not mounted on the UDP3 board. Many builders will probably choose a blue encapsulated Toroid from Tamura or Amgis, 15 VA, mounted on a blank piece of experimenter's perfboard.

The UDP3 circuit is a cascade of several lowpass filters connected in series; it is NOT a voltage regulator and there are no negative feedback loops. This is intentional and deliberate; NFB loop gain generally falls as frequency rises, often at a slope of -20dB per decade of frequency. But we want lots of attenuation (a/k/a "PSRR") at high frequencies, exactly where NFB regulators poop out.

Instead, UDP3 uses ferrite beads and several cascaded filters (one of which is a two-pole LRC filter), to achieve excellent noise reduction even at radio frequencies. The big idea is: provide Pearl 3 with a pair of low-ripple, low-noise, RF-free raw DC voltages, and let Pearl 3's onboard voltage regulators do their job, when given pristine inputs.

The UDP3 outputs plus and minus nineteen volts (approximately! remember, UDP3 is not a regulator), which the 7815 and 7915 voltage regulator IC on the Pearl 3 boards, then reduce to smooth and regulated plus and minus 15 volts.

CIRCUIT DESCRIPTION

(You may want to open the schematic image in another window, or print it on paper, to follow the discussion in this section and quickly see which component is "C5", etc.)

C1, C3, R1, BR1, and C5 form an unremarkable, ordinary AC-to-DC rectifier and filter, plus Quasimodo snubbing. You'll notice I have used C3 = 1000 nanofarads, and 1000 != 150. I spoke to the Quasimodo inventor about this, explained my reasoning, and got his approval. So use 1000 nF in your build (see Detailed Parts List) and be happy.

Then ferrite bead FB1 converts high frequency noise on C5, into heat. The ripple waveform (now on C7) has far less high frequency noise.

NPN Darlington Q1 and its supporting components, forms a capacitance multiplier that is protected against overvoltage (ZD1) and turn on/off shocks (D1). Resistor R3 ensures that the collector-base voltage of Q1 never goes negative ... which could allow input ripple voltage to shoot straight through to the output.

Then L1 + C13 + (the DC resistance of L1) form a two pole LCR lowpass filter, attenuating high frequency noise quite effectively. The relatively pure, low noise DC signal on C13 is presented to Q3 and its supporting components.

The Q3 circuit can be considered a "clamped capacitance multiplier" because its output voltage is clamped and cannot exceed (approx!!) 19 volts, even as the input voltages rises far above 19V, thanks to U1 and ZD3. The relatively weird and unknown (but extremely CHEAP) adjustable shunt reference part called AZ431AZ is used, because it offers plus minus 0.4 percent accuracy for less than USD 0.50. Much better bang for the buck than the T.I. "TL431" which is pin compatible but less accurate.

Finally, there is an output rail fuse F1 and a ferrite bead FB3 to remove the last vestiges of high frequency noise. The fuse, a small thru-hole packaged device, blows if/when you mistakenly short UDP3's output. It is available on DigiKey and Mouser for about 40 cents per fuse. Because they cost so little, I recommend you buy at least six fuses of each of three different fusing currents. Or more. Now when you get a surprise fuse-blow event during testing, you will have plenty of spares, and they don't cost an arm and a leg.

To test the first UDP3 prototype, I connected a pair of 100 ohm, 30 watt resistors to the UDP3 outputs (see photo below). These are cheap to buy and build, I suggest you get some too and test your UDP3 carefully before hooking it up to your precious Pearl 3. At plus and minus 19 volts output, these load resistors consume 190 milliamperes per supply, comfortably more than Pearl 3 draws. During testing with 190 mA load current, fuses rated 250 mA never blew.

HOWEVER, it's all but inevitable that some "hot rodder" types of builders, will add high current discrete opamps to Pearl 3. And increase the bias current in the BJT output stage. And possibly other stunts or gymnastic shenanigans which are unimaginable at the moment. Therefore UDP3 is deliberately over-designed, to provide 350 mA from +19V and 350 mA from -19V (with higher current fuses fitted of course!!) Heatsinking the pass transistors lets them operate comfortably even at these high current levels.

Schottky diodes D5 and D6 are panic protection components, whose only job is to set the rails to not-stupid voltages after a fuse blows.

WHO SHOULD COMPLETELY IGNORE UDP3?

A quick glance at the UDP3 schematic reveals that there are a LOT of components. Including four Euroblox connectors, four extruded aluminum heatsinks, eight super-low-ESR electrolytic capacitors, oh and by the way, a second chassis (!!). If you're hoping to build a cheap, cheap PSU for your Pearl 3 phonostage, this isn't it. Too many parts.

Similarly, if you're hoping to build a teeny tiny PSU that occupies very little chassis volume, UDP3 isn't for you. PCB size is 112mm X 132mm (mounting holes 100 x 120) and the heatsinks are an inch tall (25.4 mm). That doesn't even include the power transformer. See the photo of UDP3 atop a 170x230 Modushop "Galaxy" below.

Finally, if you're hoping for a "paint by numbers" audio project that doesn't require you to reason about electronics, not even once: UDP3 may not be a good project for you. There's no wiring diagram, there's no suggested part numbers for the AC mains IEC inlet or fuse holder or on/off switch, there's no transformer mounting recommendation, the list goes on and on. Avoid misery; don't attempt UDP3 if it is beyond your current builder-training-and-skill level.

ATTACHMENTS

The schematic, detailed Parts List, and PCB manufacturing Gerbers (.zip archive) are attached to this post, below. It is "Rev.A" -- the first official release of UDP3.

I've also got a few extra PCBs of the experimental prototype (rev.0) which are built on extra sturdy 2.0mm thick fiberglass, and are 50% stiffer than standard PCBs. {remember, stiffness is proportional to thickness squared}. Send me a selfie photo of yourself holding up your two chassis for Pearl 3 and UDP3, also holding the two bare Pearl 3 boards, and I'll send you a rev.0 UDP3 circuit board for $5.00. That's the cost of a mailer envelope and shipping via USPS.

his has been discussed on and off in the forums... I finally got around to designing and building an interface for using a sound card for making masurements.





Details are here: Soundcard Interface

Pete

Today (just after only 19years of usage) discovered that PMD100 suports 88.2khz rate in real world conditions(cs8414 receiver and kernel) 96khz sound can be heard but very discorted. two units tested in both 16 bits RJ and 24 bits LJ modes.


tried NPC SM5842APT in same DAC - works up to 48khz 88.2khz and 96khz very discorted and very loud(full scale output to DAC)

Datasheet says PMD suports up to55khz. And yes I am sure source exact 88.2KHZ saple rate.

What a surpsise

Very nice condition reading close on DCR .$150

March 2025 marks the 20th anniversary of Mauro Penasa's "modest contribution to this forum" (his own words) - the "MyRef" composite LM3886 amplifier. I thought the anniversary is a good excuse to design a new board for the MyRef. It turned out pretty nice, so I'm sharing the results.

The MyRef remains one of the few published composite chipamp designs. I built my first MyRef back in 2011 - on Mauro's original board, with my own relay-based 96-step volume control - but I always wanted to build a better version.

Here it comes, mounted on a 2U (80mm) heatsink:


The board for one channel is 90x50mm, all through hole, with two layers. The schematic (see post #3 below) closely follows Mauro's original Rev.C. However, I took the liberty of adding regulators to the LM318's power supply; the two TO-220 regulators are visible in the photo above. The board includes neither raw power supply nor speaker DC protection, both of which I implemented separately.

The linearity is pretty nice for such a simple amplifier:

More spectra are attached to the post #14 below.

Also, while developing the above board, I designed another, for a simple non-inverting LM3886 based amplifier according to the datasheet schematic:

Mechanically, this board is identical to the other one. My objective was to test some ideas for board layout and routing, but this board also turned out quite nice in its own right. The schematic is attached to the post #15 below, measurements - to #16.

If a crossover design calls for an 8mH / 0.790 Ohms and the two closest options are 8.2@0.800 ohms (Solen) or 8.0 @ 1.75 ohms (Janzen), which would be better or does it even matter? Actually I've already purchased the 8.0/1.75 Janzen which I suppose I could return. Any issues with either of these? If it matters, this is for a first order XO on the woofer with only a single inductor. Thanks

Let me start to say that this is only simulation with SPICE.
But I have no doubt this amplifier should do very well for real.
I challenge you to do something like it or even better 🙂

Design goals:
1. Fully discrete
2. Max 3 transistors
3. Voltage gain 4-5
4. Load 1Vrms into 4.7kOhm
5. Regulated 12V supply

Result in SPICE:
1. Voltage gain 4.6
2. THD 0.00011%
3. Frequency response 5Hz-300kHz -3dB

Hello,

I am no expert in tubes at all and have an amplifier built from the kit purchased on Aliexpress:
https://nl.aliexpress.com/item/1005...3Lcnrian&utparam-url=scene:search|query_from:



I have a pair of 300B EH tubes which I would like to use so I am thinking to repurpose the chassis and power supply for new build.
The goal is decent amplifier, not crazy hi-end stuff, let's be realistic here. So my main question is what would be the way to go: can I reuse the output transformers? What to choose as the first stage?

I've been told that I cant go by the factory FRD information and that I'll need to some software to gather the correct info to start designing my crossovers. My question is, how are you running the speakers with no crossovers? Are you running individual drivers? Wiring everything in a series or parallel to an amp terminal? Last, what app or program does everyone rely on to get accurate information?

I have made 5" version of TWTD.
















---- Alpair10.3 + TWTD at YouTube ----

Tapered Wave Tube with Damp Duct(TWTD) + Alpair10.3 - YouTube

I made this grasshopper script a while back that would dynamically make a multi entry horn from the output of ATH.

This is the sort of output you get



There is a lot of options down the side to adjust the ports and other things



The input it takes is the slices output from ath, you can select it using the Ath Slices File input (Right click and select one existing file)



I didn't end up adding the cone plug which I had planned to do, you can easily change all the dimensions currently then export it to some other software to slice up and 3d print.

I have uploaded the grasshopper project file if anyone wants to have a go with it.

This thread is about all ways to use OpAmp as input stage in power amplifiers.
Let us see your way to do this.
There are many ways to make an opamp control a power amplifier.
There are good ways, I am sure - and less good ways.

I have one way up my sleeve now, but I also have Choctaw in another thread.

I have been looking around for a 15" driver for a new OB/dipole project. A driver that is not really a subwoofer with high Xmax but rather a pro audio driver with decent specs and good HF extension that could be used down to 70-80Hz. I found the SB Audience 15MWN700D, which was just released in mid-to-late 2024:
https://www.sbaudience.com/index.php/products/woofers/nero-15mwn700d/
This is a bit of a head scratcher for a pro audio driver. Qts is not low and Xmax is not all that high. I suppose it could be used in certain applications but it doesn't quite fit the mold in my mind. But it does have very low Le and uses a copper sleeve in the motor. It seems this driver has been designed more for clean performance than outright SPL, etc. and its passband extends up to almost 4kHz with only mild breakup. With its open basket it seems like a good prospect for OB use even if it is not designed or intended for that purpose.

I did some modeling about what I could expect if the driver were used in a small baffle as part of an OB system. As part of the modeling I included series impedance of 6.8mH + 4 Ohms to both flatten out the dipole response and reduce the distortion produced by the motor. With 200W input power and a modest baffle the system can produce over 110dB SPL from around 80Hz to 300Hz, which is perfect for my use. At this power level, the 15MWN700D will exceed Xmax below 55Hz without a HP crossover, however, I would use a subwoofer below 70-80Hz so the size of the main speakers remains modest. I typically cross over to a nude midrange driver around 300Hz and I am thinking of using the Satori MW19TX plus a large AMT tweeter to complete the system (I already own these drivers).

I have not seen any testing or measurements of this driver, but given the MFG description of the design I am optimistic.

I thought I would toss this thread into the wind in case others have been eyeing this new offering from SB Audience.

Hello diyers,
I've been playing sub-less for few months but with time I realised I was really missing a clean first octave.
My boxes are not able to go very low, it's 2x 15OB350 per side in around 200 L.
They can go low with EQ of course, but they just sound better crossed around 35/30hz, lower is just noise.
Don't know if it's the drivers high fs/qts, the "still" too small boxes or maybe not strong enough, or the room placement, probably all combined.
I see them more as big mid-bass in fact.

I had in mind to upgrade the drivers at one point, for the nero-15sw800 that should better fit the needs, but even if they're not that expensive it's still four of them that I'd need. And more important I'm not 100% convinced it will be a big improvement due to the mains placement.

So before going there I have to try spread bass again, within following constrains:
1 - nice look and integration with furnitures
2 - high sensitivity
3 - critical damping if possible

#2 means big drivers, I still have my four 18sw450 from my previous dipole, why not using them?
#2 and 3 kind of go together, but against #1 for the size implied.
#3 is a way to finally decide for myself if an L/T box can really sound the same as a big natural one (and I believe not, but lets' test).

I started with what I had around and within the new room layout constrains, with a sealed um12-22 in maybe 100-120 liters (much bigger in real but with sand walls) right behind me.
Not bad at all but not enough juice, plus it's not easy to nicely integrate with the furnitures.
I couldn't try my old concrete ported one as I got rid of it few months ago (and for that I had to destroy it in place, too heavy to get out 😛). I don't regret, it stayed for years unused in the same spot, it was fun to build, but also just too bulky, and too hard to move around to test different spots.

So, I had to find a way for 2-3 subs, placed behind me, light enough to move around a bit, but big enough to not require an L/T, easy?
Thought about it few months ans was about to buy woods when… again my favorite/hated shop just launched a new serie: the rådmansö.
Beautiful pieces in my mind, I would have loved to start with these when I've built my mains, a lot of cool stuff could be built around them.
Went to see them in real, and realised even the big one could do it, this one, 159x64x46cm, 468L. :




Got one, some mdf, some valchromat and let's go.
Like previous stuff I've just built a box within a box, 18mm glued all around inside, 24mm for the back, half the baffle doubled in valchromat, bracing with scraps, kind of light. The good surprise is that the radmanso is full particle boards, no honeycomb core on this like on many others, so nearly 4cm thick particles + mdf at the end.
The baffle is removable so I could add more bracing later if needed (I already found a spot that may need it).
And I could try 1 or 2 drivers, even clamshell isobaric if the box is still not big enough 😛
It's around 330-350 L. I'm guessing. Yes I did some sims but, they're just sims…

I of course did few mistakes again, my very first move was one! While sanding the inside of each panels for better glueing, I messed up and sanded the wrong spot of the panels, the edge that would have been visible outside. So I couldn't get the recessed baffle like I initially wanted.
Damn' what an idiot. So the baffle is now flushed, I'm sure it would have looked much better with the recess (like the mains).
Maybe I'll add a fabric grill, I'll see, it's fun to see the big driver too.
Then the valchromat was finished with tung oil, for a nice dark contrast.
Some details are left for later like the right cable, neutrik connector, better driver screws, replace temp wheels once in place to decouple a bit etc.
Not sure I’ll use the original steel stand that comes with it, it’s sturdy but will add 20cm in height.




I quickly plugged one little fosi on it yesterday and it seems promising, efficient for sure.
I hope I can move it in the right place soon to measure it.
Meaning right below the diffusors behind me, where I now have a bunch of besta used for storage.

In all this I kind of try to find the same effect I had in my car years ago. I might repeat myself but it was so fun with 2x15'' at few cm right behind the head. Breathtaking was the right word, literally, and I'm not talking SPL, just air movement in your lungs even at low levels, like someone with a pump trying to empty your lungs at every beat!

Of course home environment is a total animal but if I can get 10% of this I'd be happy 😛
Will come back with measurements soon, if a success I will build another one, and maybe even 3 in total.
Cheers!

I am new to the world of personal audio. I come from a background of music appreciation/collecting/archiving and a bit of hobby digital DJing (yes, I am not a "real" DJ lol). I decided to introduce my wife to DJing and my first step was to purchase two V-Moda M100 Master headphones (for shared listening) and Pioneer DJ VM-80 speakers. In order to connect these to my laptop, I bought a Zen DAC 3 and an iFi Audio 4.4mm to XLR cable one month and a Zen CAN 3 the next month. I use an iFi Audio 4.4mm Pentaconn analog cable to connect them. After I did that, I bought two iFi iPower X power adapters. Each step in this process brought even better audio to the setup.

I joined a message board and began to look for ways to improve this setup even more and came across information about what is the best USB cable to purchase. I was informed that isolators/regenerators/reclockers were good to have as part of the chain between laptop and DAC, and I was recommended to purchase an Altor T1 from Alex Torres.

The small .070 gram USBISO arrived after a month and both Alex and I were challenged to figure out exactly what was wrong with it. In the end, I realized that nothing was wrong with it! This is how we figured out together what I had to do to get it running.

When I first plugged the USBISO to the DAC, there was no connection, but its red LED light was lit (even before connecting it to the first iPower adapter that came with the Zen CAN 3). I used a Gothic Audio Semper Fi The Outsider .3m cable for both before and after the isolator. So, that was strange. Later, Alex suggested that I should connect either a removable storage or mouse to the isolator, which I did, and there was "energy" but no "data" running between these.

Alex didn't know why and suggested that I should return the device, but I decided to run a diagnostic because I didn't want to give it up so easily to return it for a refund or exchange. I chose to run this particular diagnostic by connecting the isolator to my wife's laptop and I noticed that immediately the cursor worked. So, that was interesting.

Here's the key part of this story:

My laptop is relatively new, purchased in January of this year. When I got it, I did something kind of geeky and tried to remove everything that I thought was nonessential, however, in the process I most certainly removed something that communicates data between laptop and devices. I am not sure, then, why the DAC worked, but I decided to save all my data and reinstall_Windows. That allowed my isolator to work. Problem solved! I am not sure how the Isolator sounds without the Gothic Audio cables but the entire setup sounds great. I am very glad for this tiny device, but most of all for Alex's patience and guidance because I tend to overreact and send multiple panicky messages before he gets a chance to write back.

There is so much more that I can do with the setup, but given a limited budget, I am going slowly and step by step to try to have the ideal setup for our little jam parties at home.

For sale is a Gainclone amp I built some years ago and hardly used. It's a little dusty but fully functional except it needs RCA jacks and binding posts. It could also use a better enclosure than the one you see in the picture. Uses the LM3875 chip. Asking $75 OBO including shipping to CONUS only.

I would like to have something that can increase (I already know how to decrease) the damping factor without adjusting the amplifier feedback, such as filtering, preamp, DSP algorithm, or similar... I have seen a DSP algorithm that can increase DP but don't have access to it. I would be grateful if someone could provide even a little information

Want to buy HYPEX NILAI.

Hey all! I've been a lurker on these forums for some time now but decided to register. I recently built a vacuum tube amp from a kit and thought I would dust off my long-unused EE skills and try to build a solid state amp next. I am currently working on an F5M build to start with but after that I plan on building some kind of Aleph (I like the First Watt designs). Anyway, this seems like a nice community and I'm looking forward to posting my progress. Cheers!

Well done. Just like my name.
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Please I need music fidelity k550 service manual

Great album, has anyone else done the cryptic crossword which came with the original album cover, or rather, the newspaper?

I completed about 80% of it but some clues didn't make sense - which was probably intentional.

Geoff

When I decided last year to explore some Stax electrostatic headphones, I discovered that even their older-model headphone amps are jaw-droppingly expensive. So I got an SRD-7 Adaptor and converted it to power high- and normal-bias Stax 'phones. Unfortunately, the sound quality left much to be desired.

The good news is, it's most glaring problems are fairly easily addressed. I just completed these detailed mods for the SRD-7 adaptor:

Transforming the Stax SRD-7

Comments/questions welcome. (This is my first crack at creating web content of this ilk outside of a forum, so be gentle... 🙂 )

This amazing little amp has been discussed as part of the DB thread but I think it deserves its own thread given how it has quite different objectives from the Pocket Diamond Buffer (PDB) HPA.

This desktop variant uses TO-126 output BJTs with dedicated heatsinks and does not have the separate MOSFET rail switching needed for the pocket one. The setpoints have been optimized for a moderate 40mA nominal bias current that will let you run in full Class A operation for most headphone uses. It will leave Class A around 250mW into 32 ohms. Of course, you can adjust the emitter resistors to run higher bias currents. I have used it with +/-9v, +/-12v, +/-15v and +/-18v supplies and they all work great. It was designed for 15v rails but I don’t think performance suffers much from using lower voltage. For your particular use case you may want more voltage. High impedance 300ohm cans like more voltage, for example. There is lots of room for input cap rolling and I have used huge 4.7uF 400v MKPs and also smaller 0.47uF film to bypass 10uF Elna Silmic electrolytic caps.

Here’s a photo of a built up amp board in operation:

With larger MKP caps only:


I initially struggled with an oscillation but chased it down to a feedback compensation cap that was too large. That’s all fixed now rock solid. A stability analysis on LtSpice pointed me in the right direction. So the schematic shows a 470pF cap needing to be replaced with 47pF. It’s an easy swap and I’ll do this on the SMT pre populated boards that I will be offering in my shop. I will also have bare PCBs for those wanting to assemble it themselves.

Here is schematic for the overall amp, very simple. Power supply in, audio in, audio out and volume pot with MicroMatch IDC cable to an RK09 pot helper PCB (included).


Here is schematic of the Diamond output stage:


Here is a SMT prepopulated PCB so all you need to do is to install all the through hole parts:

Both sides:

Here is the board assembled with big 4.7uF MKP caps:


Standard BOM calls for ECB pinout TO-126 BJTs (Toshiba TTA004 and TTC004) but if you have some classic Toshiba 2SA1837 and 2SC4795 (BCE pinout) you can mount them in the bottom like I did here - leaves a cleaner look on top giving you lots of access to the parts:


Testing on the bench:

Nice low distortion but second harmonic dominant distortion profile for 1Vrms into 33ohms:

You will find that this headphone amp sounds very natural and clean, but has an incredible power reserve to deliver bass slam while maintaining great control authority of the driver transducer cone. It’s a wonderful headphone amp to listen to for hours. For normal headphone use (under 500mW power) basic AC/DC modules designed for delivering circa 350mA into 15v can be used with a 7812/7913 voltage regulator and it will work fine. You can also make really fancy PSU with linear trafos, cap multipliers, CLC, and low noise LDO’s etc. with a proper PSU capable of 750mA and +/-15v you can drive up to 1.5W into 32 ohms (for those fans of the HiFiMan HE-6).

I’ll be offering the SMT preassembled PCBs for $59. Bare PCBs for $22. Boards are all 1oz copper and ENIG finish.

https://xrkaudio.etsy.com/listing/1659118057

BOM is here. Note that BOM calls for OPA1642 but the pre-populated PCB has NE5532 installed. This was due to availability issues but I can assure you that the NE5532 sounds fantastic and measures well too. If you want to swap it out later, you are welcome to do so.

If you want to boost the output BJT bias current (80mA) for operation to a higher power under Class A, use this 2.2ohm metal thin film emitter resistor (R213/213/312/313):
https://www.mouser.com/ProductDetail/Vishay-Dale/TNPW12062R20DEEA?qs=vHuUswq2%2BswIE18TmZVkaQ==

Note that the heatsinks will get significantly hotter and the PSU also needs to provide more quiescent power.

For the 8pin Wurth IDC cable with matching connector for the potentiometer, get this cable (or its equivalent).

If you have trouble understanding this test, or you have questions, please read:
TEST FAQ
Update July 3rd 2012:
Although the title of the thread contains the word "test" this is better thought of a s a survey or poll. The word "test" has caused a good bit of confusion and misunderstanding.
The test tone provided is not used to set you system levels, it is used to measure your system levels. You will set the levels by ear, or by pink noise if you wish.
What you will be doing is measuring your actual listening voltages and reporting them here. The test tone allows you to do that with very good accuracy using only digital playback and a voltmeter.

---

100Also have a look at Archimago's blog for a very clear explanation of this test, along with good photos and link to more info.

---

100
Here is a simple test to determine what voltage your speakers need to play their loudest. From that you can determine how much power you need.
Knowledge is good and this test will tell you just how much voltage (or power) you really need. Efficient speakers in a small room may need only a volt or two. Less efficient speakers in a big room may need a dozen volts or more.
I've included a poll so that we can see what's typical. If you want to also post your speaker details and room details, that would be nice.

For the moment, I'll leave this as a voltage test, we will talk about power later. Those of you who know Ohm's law can figure it out for yourselves. Amp power tends to be an emotional issue, so we'll post the results in volts for now. Since most amps are voltage devices anyway, it's not a bad way to measure. And a voltage measurement removes the speaker impedance from the equation.

All you need for this test is some sort of digital playback (CD, iPod, Squeezebox, computer, etc) and a volt meter with a low AC scale. Any scale 20V or lower should be OK. Meters with only 200V AC scale won't be accurate enough for this test.

Next post has the test tones and instructions.

There are SMD parts, electronic relays, for audio signal. What kind of relays are these ?

Hi

Long story, but I’ll make it short.

Picked up a pair of used Lowther EX4’s in really good condition.

While testing them, in Martin Kings MLTL enclosure, and swapping out amps, they were both turned into smoke machines. Not my best moment…

They are in their way to Lowther for repair, and I will have the option of having either silver or aluminium voice coils installed.

As I didn’t get to finish getting the filter networks installed, parts had not arrived by the time I ruined them, I didn’t get to hear them “properly” with their original aluminium coils

Any thoughts/experiences with the differences between the coils would be greatly appreciated!

Thanks

P

I'm searching for the JBL URIE 813B studio monitor model 840 crossover circuit diagram. I checked overload bulbs and fuses good, so must look deeper. Any info would be appreciated.

Built some single ended planers recently and noticed in distortion measurements the 3rd harmonic was higher than the 2nd harmonic. Is this typical for single ended magnet planers?? None of the free swinging ribbons I've made do this. Has anyone done a compare of distortion measurements between single sided magnet and push pull arraignments? Note the purple line above all the rest in the attached pic

I have been restoring this old amp for awhile now, I was so close to finish it but then I saw smoke coming from R30 in zobel network, it happened twice, at first I thought some short caused this because it was momentary and amp worked fine after reseting the power, but now R30 is constantly heating, what could cause this? That resistor used to be always cold.
Transistors are new, I measured all of them no sign of short, caps are also new. Resistors are old but they are all in range of +/- %5.

My multimeter just stopped working properly—it can't measure voltage correctly, although the other functions still works fine. How can I identify the issue? ChatGPT suggested that if the resistor is still heating up even with no speaker connected, it could mean either C13 is faulty or there's a 100kHz oscillation present.

Any suggestions? Meanwhile I'll look for new cap and replace the old resistor with 10r 5W one, too bad can't measure speaker's output DC voltage right now.

I've been given a bunch of Caps that the giver was using for experimenting crossovers.
Unfortunately they appear to have been liberally coated with some sort of bitumen type compound and a strange sticky grey blu-tak like goo. (possibly to damp vibration ?)
Alcohol based solvents dissolve the goo but so far only Turpentine will remove the "bitumen"

Is it ok to soak the caps in Turps followed by Meths to clean ? or have you any other suggestions ?

So I upgraded the Nord Rev D buffer board in my Hypex NC 500 based amp with Sparkos opamps and 15v Sparkos voltage regulators. I decided to measure the DC offset at the binding posts with no load and nothing connected to the inputs. My meter started at 20 mV and over the next 10-15 minutes settled out around 350-400 mV. The range would fluctuate by some 30 mV consistency after 15 minutes and never stabilize. Obviously this seems like a very high number and it concerns me. I never checked the amp’s DC offset before the upgrade.

Should the amp be under load for this measurement? I can pick up an appropriate resistor if needed. Also, should I have the amp’s inputs connected? Thanks for any help guys. I don’t want to hook up my speakers until I know the amp is safe. The voltages check out fine and the regulators are holding a steady 15vdc +/- on the buffer board.

Have been gifted a pair of Toa Horns. I've no PA experience and looking at current Toa product I assumed these were 70v line drivers...but was told they were used on std home hifi as additional drivers.
Plugged them in to a basic 20watt/ch 3-in-1 home mini system and they seem to play fine. (other than the constrained range of course)
Can anyone explain what may be happening ?

Thank you for accepting me here in this forum

So the question is a new hivi dmb-a or used dynaudio D52 assuming they are in good condition? Always loved the D52/D28 combo.

Hello everyone, I'm new to the audio world. This is my first practical assignment for my courses so i want to improve it more. Since English is not my mother language and this is my first question so maybe there are some mistakes.
The requirement of the circuit:

• The bandwidth: 15-50Khz
• Output power on load should > 30W
• The efficiency η > 45%
• Distortion < 1% at 1Khz
• Input signal is in range 50mV - 100mV.
• The input resistance: Rin > 20k

This circuit i adapted from Audio power amplifier design handbook of Douglas. However, when i tried to simulate this, i met some problem:

• The quiescence current is too high, about 130mA through Q15 when a load is attached (if no load, floating, the ide current is much lower). I changed the bias voltage with Vbe Multiplier (Q10) but it didn't help.
• The gain to fulfill input 100mV and output 30W which make it become tremendous ~ R8/R9. So i think i need a preamplifier before feed the signal into power amplifier.

Could you suggest me some improvement to the circuit?






thank you verry muchh.

This thread is a place for links to other threads that are related to the freeDSP project. Feel free to post with these links and a brief comment on what the thread discusses. Occasionally the moderators will consolidate them into fewer posts.

Please create individual threads (and link them from here) to connect with other people working with the freeDSP for discussion and to support each other. Please keep in mind that freeDSP is a spare-time project and not a commercial product. If you want to get a freeDSP you need to build it yourself (manufacture board, order parts, …) or organize centralized buying with other DIYers.

The freeDSP is a low-budget open-source digital signal processor family, which is published under a creative commons license. It allows the unrestricted use and modification of the modules. The applications range from active loudspeaker concepts and room equalization over advanced musical effect processors to car audio signal processing. We would be happy if you join us and improve or extend the project.

GitHub is used for file exchange. If you want to join the development team, just send us a private message with your ideas and your GitHub user name. Most freeDSP PCBs will be designed using KiCad. Some guidelines were defined to make future freeDSP development and extensions as compatible as possible. These layout guidelines can be found in the freeDSP-Wiki.

In the following you’ll find a summary of the current freeDSP plans:

green = sources tested and available,
black = work in progress,
gray = on the wish list

freeDSP motherboards:
freeDSP CLASSIC (ADAU1701 / 2 x In & 4 x Out Analog via RCA) freeDSP thread, SigmaStudio AutoEQ
freeDSP CLASSIC SMD (ADAU1701 / 2 x In & 4 x Out Analog via RCA)
freeDSP INSANITY (ADAU1452 / 4 x In & 4 Out Bal. Analog via Jack, alt. 8 In x 8 Out Unbal. / 1 x In & 1 x Out SPDIF via RCA & Toslink)

freeDSP compatible motherboards:
PiDSP (ADAU1450 / RasPi In + Out / 3 x I2S In + Out ) PiDSP thread

freeDSP programmer:
freeUSBi + EZ-USB

freeDSP IO expansions:
freeDSPx AES/SPDIF IN (1 x In AES/EBU via XLR / 1 x In SPDIF via RCA)
freeDSPx SPDIF IO (1 x In & 1 x Out SPDIF via RCA & Toslink)
freeDSPx BAL OUT x16 (16 x Bal. Out Analog via SUB-D)
freeDSPx ADAT IO x3 (3 x In & 3 x Out ADAT via Toslink - maybe even 4 IOs)
freeDSPx BAL IO x4 (4 x In & 4 x Out Balanced Analog via Jack, alt. 8 In x 8 Out Unbal.)
freeDSPx UNBAL IO x2 (2 x In & 2 x Out Analog via RCA)
freeDSPx PHONES AMP
freeDSPx AMP
freeDSPx HDMI IO
freeDSPx DOLBY/DTS/AC3 IO

freeUSBi kits and freeDSP classic kits are almost always available - please use the contact fomular on our website 🙂

Which wood to use? Which fill? What does bracing do? Is CLD best? I'm starting this project to start quantifying some answers to these questions. A lot of work has been done before in fits in starts by others (BBC, Kef, etc.) but they were often narrow investigations and you couldn't compare results because measurement conditions were different among the different studies. Some have cited manufacturer's damping specs, but I have no idea how that translates to the real world. Ditto on accelerometer data. So here I will be doing SPL measurements, that is after all, what we actually hear. The cabinet is ordinary, large enough for the panels to have some radiating area and magnify differences between changes.



I will be using a Peerless 830970 firing into the cabinet using MLS signals. I have to test mic placement, but it will probably end up near-ish field, probably at a side panel. When I do the fill/lining I will mount the SB15 as a dummy woofer and measure what radiates through it. I intend to measure SPL, CSD, and THD. Any other recommendations appreciated.

For the material test I currently have: high and low quality plywood in 1/2" and 3/4", and MDF in 1/2" and 3/4".

For the fill and lining I have: SDS CLD tiles, AcoustX coating, denim insulation, polyfill, 1" thick dacron blanket (what the TL guys use) and Sonic Barrier.

For bracing I will do: simple oak crossbrace versus oak crossbrace using CLD construction with Sikaflex 292i adhesive. I also have some microspherules to combine with the adhesive to see how that changes things.

I would appreciate all suggestions on any other additions to the above. A priority will be that the materials must be widely available and reasonably priced, and the methods must be accessible to an ordinary DIYer.

Hi,

Alex Torres suggested that I should tell my story so I might be able to help others. I had a certain conflict between my laptop and his USB isolator. I will be sharing on digital line level how it was resolved.

I hope this will be useful to others!

Hello, I have 8x DAC PCBs for sale. DAC chip AK4490EQ is soldered on the board. 768kHz/32Bit and I2S/DSD input. All are unused/new bought originally from DIYINHK. Intended for a DSP crossover project but never got to work on it.

I am thinking of 15 EURO per piece plus shipping from Germany. All 8 PCBs together 100 EUROs.

Please let me know if you have any questions.

Best regards,
Klaus

A very simple question! Does anyone know/remember if the mains transformers on these amps can be reconnected to take 230-240vAC mains electricity? If so I shall be delighted to hear - either way - as I have an opportunity to acquire one which appears to be in good condition!

I would also very much welcome a copy of the circuit schematic....please.

[Are you out there Zen MOD????🙂]

Many thanks.

Hi everybody! So I have a Revox B 226-s

I was recommended by a user to change these opamps. It was supposed to be 2 different Opamps NE5532 and LM833.
and the replacement was OPA1642 and OPA1656. But when I opened the machine.. (Wich I should done inte first place I know) there different Opamps. 4 RC5532N
I have tried to contact this user although he doesn’t answer. Is there someone here with Experience in this? Or do I miss understand him? I’m attacking a picture on the Inside of the Revox.

Thanks.

Hi all,

I have a set of LEM Tour Master 12.2 (along with subwoofers), where the one full range speaker acts a bit weird. The system is from 1993, I believe, but they should be of decent quality (Crown amplifiers and RCF woofers).

The speaker plays just fine with no hum until a certain volume. After crossing this volume, the woofer starts distorting a lot. I suspected a blown woofer to begin with, but I am thinking the amplifier is at fault now.
After reaching this volume, when I turn down the volume again, the speaker hums loudly, and it pops loudly as well, when it is turned off. It does this for some minutes even after turned off and on again.
Then it works normally again after a bit of time.

Could this be bad capacitors or something? Has anybody tried something similar or have any ideas? 🙂

Thank you in advance!

Orders now are open for Quad PCM58 Iout boards, ready built and tested or as a bare-board kit of parts. This board is not a complete DAC, it requires an external I/V stage. PM me while not forgetting to include your chosen payment method and location so I can quote you inclusive of fees and shipping.

When developing the 'Dark LED' I/V stage I prototyped a number of DAC chips to feed it and it was the PCM58 that won out in our listening. According to its datasheet, the PCM58 is the lowest noise multibit DAC chip available - later generations (including PCM63, PCM1702 and PCM1704) haven't been able to improve on its idle channel noise.

The quad PCM58 current out design has discrete regulators fed from IR LEDs for the DAC chip power rails and accepts I2S input. To create a complete DAC you'll need an interface board on the input (S/PDIF, Toslink or USB) and for generating the output, an I/V converter. The intended use case is with the 'Dark LED' module - the power rails are the same for the two PCBs, +/-18V. Using 0R resistor options the PCM58s may be configured in single-ended mode or alternatively, balanced with an on-board phase splitter. Multiturn pots are included so you can trim the 4 most-significant bit weights of the DACs assuming you have suitable measurement kit. If you don't have that kit, I'll leave those trimmers off the board by default so as not to disturb the factory trimming of the DACs.

Physical dimensions: 100mm * 100mm, max height 20mm. Fixing centres : 95mm * 95mm, M3 holes.




Price for a quad PCM58 built and tested unit is : 780RMB (~USD108) to include 4 recycled PCM58 DAC chips which are fitted in turned-pin IC sockets.
for a bare-board kit, including 4 DAC chips the price is 640rmb. We'll be putting up the stuffing guide shortly.

If you already have your own PCM58s the price for the board without DAC chips is 500RMB and I'll supply the sockets unsoldered unless requested otherwise. This is because many recycled PCM58s have disfigured legs which are rather tricky to fit into sockets when they're soldered down due to the nearby components.

Our 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%.

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.



What else is needed to turn the Quad PCM58 into a fully operational DAC?

You'll need an input interface board to feed an I2S input to the Quad PCM58 over 3 wires (no MCLK is required). The popular gold-standard USB interface chip CM6631A though is typically not compatible with this board as in stock form it outputs a BCLK of 128fs at 44k1 sample rate whereas we require a 64fs BCLK. If you buy the CM6631A card through us we can perform the firmware upgrade needed to make it compatible. Your output stage (I/V stage) could be as simple as a couple of opamps, configured in transimpedance mode. A low-noise, high speed one is preferred. The ideal I/V from the SQ perspective would be a discrete one like 'Dark LED' customized slightly to run from a unipolar input current. Seeing as the PCM58's DAC internals are unipolar, it generates a bipolar output current through the provision of a secondary fixed current source which adds half the full-scale peak-to-peak output current (1mA). This is the function of the BPO pin on the DAC (pin5). Seeing as this additional current source adds noise it is best to avoid using it if the I/V stage can handle a unipolar input current, which the Dark LED can, given a change to two resistors (R1 & R2). When the BPO pin isn't being used the 0R resistors R7,R30,31 & 32 are not fitted, nor are C7,C14,C20 & C27 which decouple the BPO current source.

You'll also need a well regulated low noise power supply of dual rail +/-18V rated at at least 150mA An LM317 and LM337-based board will be sufficient as the PCM58s have their own regulators. If you already have a single winding AC supply (an AC wall-wart) then 18VAC at 10-20VA would be in the right ballpark. Use a half-wave rectifier so you get both rails from a single winding or alternatively, a centre-tapped trafo. I don't recommend using switching supplies due to issues with common-mode noise, its very hard to filter out unless you're using balanced connections to your amp or pre.

Speaking of balanced mode, the board may be configured into being a 4 channel (L+,L-,R+ & R-) system at 1mA peak per channel or a 2 channel, 2mA peak per channel solution with the four DACs configured in two paralleled pairs. In balanced mode you'll need 4 channels of I/V. The configuration is handled by 0R resistor on the jumper 0R resistor locations U16-U18 and R33,R34.

Hello everyone! I'm new to this, so apologies if my questions are a bit basic.

I'm working on a small project to "re-factor" an old Samsung HW-D570 soundbar into a compact 2.1 audio system. My plan is to move the amplifier section into a standalone box, connect two wired speakers to it, and keep the wireless subwoofer as it is.

According to the specs, the original soundbar uses two speakers described as "2-way, 80 Watt, 4 Ohm, wired". Each speaker actually contains two small woofers and one tweeter. The woofers are labeled "HUSNF-00900, 8 ohms." When I measure the impedance from the wires going to each speaker (which includes both woofers and the tweeter) with a multimeter, I get about 4.5 ohms.



I have a couple of questions:

• Is this a 2-way or 2.5-way speaker system? And are the two woofers in each speaker likely wired in series or parallel? I can't see the internal wiring clearly.
• Main question: Can I replace the current speakers with some spare Monitor Audio Radius 45 speakers I have? These are 8-ohm, compact satellite speakers rated for 15–50W, with a 3" woofer and a rear-firing tweeter. (Or should I rather use 4-ohm speakers? Or only keep the original speakers?)

My main goal isn't necessarily to improve the sound quality, but to change the format and case of the system to better suit my needs.

Thanks in advance for any advice or insights!

I'm thinking about upgrading my surround system to Atmos so have a need for in-ceiling speakers. In my search I came across these:

https://www.crutchfield.com/S-bYgFC...c2IpAbYCHpZzlSha3oc8dEza696tvhZYaAhdoEALw_wcB

This got me to thinking... these use a single full range driver shoved in a can which seems doable with a 3d printer and a few hours in Fusion 360. Can anyone think why this wouldn't be a good idea? If this isn't a completely dumb idea what drivers should make my short list? I think my starting qualifier would be that they have to get loud enough to be used at reference volume without notable distortion.

Hi
the base of this amp is the huge thread about :

100W Ultimate Fidelity Amplifier​

these is the thread for all fans of the Vertical brother of APEX FX8 done by XRK and prasi:
the amp was modified by XRK and others and use no Lateral MOSFET --> therefore well known IRFP240 and IRF9240 are used.

here are some examples and comments:
here
here:

I have for sale 2 sets of components for building the Miro AD1862 DAC. Each set consists of 1 x AD1862 SMD DAC board, 1 x Miro PSU1 board, and 1 pair of AD1862 IC's. AD1862 IC are genuine (from Paddy & zoom777) Each set is priced at 40 usd plus shipping. Please see the attached pic.

Regards,
MM

It has been a Long time after the DDDAC1543 saw the light and the world moved on, especially if we look at available sound track material. So much great soundtracks with high Resolution. Red book is not dead of course, but if I spend money on sound tracks, I look for 96/24 or even better 192/24, or the SACD equivalents 88.2 and 176.4...

In the past year I have been working on my new project: designing a DAC which will play up to 192kHz / 24bit material from a PC (or Mac...) There are many DACs who can do this, but I wanted to design a NOS version, as so far, every listening test I did, this led to a more open, natural and detailed sound.

I found this to be possible by using the well-known PCM1794 and avoiding the digital filtering built into the chip. This proved to be quite tricky, but I managed to find the key to do it. It has been a great adventure with much to learn and a fantastic result at the end....

To feed the DAC, I kind of integrated the WaveIO USB Receiver from Lucian. Great design and better sounding than all others I tried (see my website for this as well); I give a very detailed report on www.dddac.com

You can download the circuits here: dddac1794_nos_ver30.pdf



The Images below show:
The Mainboard with I/O and I2S to right justified conversion
The actual dual mono DAC Module (can be stacked parallel)
Built up with 4 modules and two power supplies (5 and 12 Volt)
Wired up in Chassis (Mundorf Gold silver oil output and optional Sowter 1:2
The DAC in my Audio rack
Another view inside
Block diagram


I opened this thread to share my design and experience and give a platform for questions, feedback, remarks and/or discussion...

Hi all,

Talk me out of this? I'm just enamored with the idea of a small foot print "tower" that is taller with lots of 8" drivers in it. Instead of a big box, a tall skinny tower. The small foot print is just easier to place in various rooms. Visually it's fun to see. It allows the use of lots of inexpensive drivers. And generally doesn't need much power to get loud. But would it need to be a sealed enclosure? Or ported? All the subs sharing one volume? Or make groups of 2 in their own cubbies in the enclosure? 4 to 8 drivers so that wiring loads is easier?

I tried modeling some options in WinISD but I'm not sure if it handles real world what happens with multiple drivers in one volume or not? Any other options that are more realistic?

Overall bad idea? Better to just build two 10's and stack them instead?

Purpose would be music mostly.

Very best,

I originally made a similar post in the Room Acoustics forum; however, there appears to be a lot more discussion of CLD in this forum. (Pretend the room is a big speaker enclosure – just kidding.)

I am remodeling my family room and want to make it a better “listening” environment for stereo and future multichannel. About ten years ago I read Earl Geddes excellent book “Premium Home Theater” and one of my big takeaways was his recommendation to use CLD in a listening room to absorb bass while preserving midrange and treble liveliness. Although Geddes also recommends CLD for sound isolation - that is not my objective, since one corner of the room has an open ½ flight of stairs up to the middle level of our home with no good way to enclose it.

Tentative plan is to incorporate CLD into the ceiling, the front wall and one sidewall of the 8 x 14 x 24ft room. Sound isolation clips would be attached to studs/ joists with 7/8” steel hat channel attached a maximum 4’oc and spaced a maximum 2’ apart. Two layers of lightweight ½” drywall separated by a suitable damping compound (Green Glue?) would be attached to the hat channel.

Is this a worthwhile endeavor to hopefully preclude the need for standalone bass absorbers, multiple subwoofers, room correction software, trial & error measurements, etc?
Is this a good design? Am I on the right track with the following design assumptions?

Increase the flexing of the constraining layers (and thus energy absorption via CLD) by decreasing the stiffness and mass of the constraining layers.

Reduce the strength of reflections into the “listening” room by decreasing the stiffness and mass of the constraining layers.

The damping compound that is used between the constraining layers should have very good adhesion and be more viscous than elastic so that energy is absorbed rather than returned to layers.

Minimize the Resonance Frequency of constraining layers by increasing mass and decreasing stiffness.

I'm really looking forward to this -

Designing Audio Power Amplifiers: Amazon.co.uk: Bob Cordell: Books

Hello, I'm a new member from the USA. I'm currently building a 2 way speaker. I have interest in building a power amp.

Hey Guys, I have found this forum invaluable in helping me evaluate which sub I want to build to start my mini rig. In particular the Xoc1 TH18 thread has me sold thats the way i want to go. Thanks for having me!

Hi guys, new to the "business" and trying to build a wifi speaker 😀 will be fun

I've been trying to find a reliable formula to calculate the total group sensitivity of a relatively odd configuration and number of LF drivers. They would be arranged as close as possible to each other.

In my own personal scenario ->

- 3 identical 12" LF drivers, wired in parallel, individual base sensitivity of 87 dB/2.8V/1M per driver, arranged in a triangle.

- what would the total sensitivity be of all 3 drivers playing together at frequencies lower than the equivalent of 1/2 WL?

With an even number of 4 drivers connected 2 in series, then the 2 groups paralleled, we'd theoretically observe a 3dB gain from doubling the driver count and another 3dB from doubling the cone area, but lose 3dB from cutting the drive voltage to each woofer of the series connections. That leaves us with a total net gain of only 3 dB if we only count the frequency range that falls in the 1/2 WL CTC driver spacing.

With an abnormal quantity of drivers, CTC spacing and adding in series.resistance from a thinner awg, it becomes a bit more complicated to figure all this out. Short of putting it in a software sim, which isn't always accurate, there has to be a better way to get a closer answer.

The TDA7293 series are underrated gems in the DIY world. This chipamp, with its modular structure, clip detector, mute-stby functions, low noise and low distortion, produced with DMOS technology, actually has the potential to compete perfectly with National/TI's LM3886. On the other hand, it is common practice to use chipamps with a buffer due to low source impedance demands and relatively high input bias currents. Likewise, with composite feedback applications, both the noise and distortion efficiency of chipamps can increase significantly. In our implementation, two matched N-channel JFETs, together with the PNP transistor, operate as a complementary feedback pair as a high-impedance, high-CMRR differential input buffer for the TDA7293. The JFE2140 / LSK389 LSK489 dual JFET combination used provides significant improvement in THD and noise compared to the use of the chipamp alone, thanks to its extremely low noise. The composite feedback rate is 26dB (20x). In this way, ~1.25v RMS input signal is sufficient for full power. On the other hand, thanks to the DC servo circuit established with TI's low-noise, low-offset opamp OPA277, the DC offset remains below 1mv.

Our inspiration for our design was Bob Cordell's LSK489 application notes and JFE2145 datasheet.
https://www.cordellaudio.com/JFETs/LSK489appnote.pdf
https://www.ti.com/lit/ds/symlink/jfe2140.pdf?ts=1717672324923&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FJFE2140
https://www.st.com/resource/en/datasheet/tda7293.pdf
https://www.ti.com/lit/ds/symlink/tps7a49.pdf?ts=1717660447218&ref_url=https%3A%2F%2Fwww.google.com%2F
https://www.ti.com/lit/ds/symlink/tps7a3001-ep.pdf?ts=1717738722969&ref_url=https%3A%2F%2Fwww.google.com%2F


The ancient 78xx 79xx series regulators, which are well known in the electronics community, have been used in audio circuits for years thanks to their stable structure, high PSRR rates and relatively low noise(?).
Measurements of 78xx-79xx ICs (even though noise values such as "0.003% Vo" are given in their datasheets) have been found to reach noise values of 500uV - 1mV in the audio band, which may disturb sensitive ears, regardless of the input noise. Of course, such a supply noise is meaningless for modern audio opamps whose PSRR is around 120dB.
However, especially in discrete applications (since PSRR efficiencies are quite low), this level of noise will be disturbing.
Although complex, discrete, parallel-hybrid low-noise solutions have been produced to solve this problem, these applications remain a troublesome alternative due to application difficulties, additional noise due to the area covered by the regulator, and the necessity of matching components in some applications.
Our application provides a good and affordable alternative to all these difficulties. TI's low-noise regulators TPS7A4901 for + rail and TPS7A3001 for – rail form the heart of our application. The effective noise amounts of these regulators in the audio band are below 15uV (RMS) level. In addition, while PSRR rates are 60dB in the 78/79 series for 100-120Hz, they are around 70dB in the TPS7As. On the other hand, load and line regulation rates and transition responses are significantly higher than the 78/79 series.
Although the input voltage of these regulators is limited to a maximum of +/-36v, input up to +/-60v can be applied thanks to the input voltage limiter used in our application.
Since the pinout of the 78/79 series is used directly, they can be used as a one-to-one replacement in applications where these regulators are used.

EPIC S

EPIC S


Positive Regulator Schematic


Negative Regulator Schematic


Final prototype measurement of EPIC S.
1K-1NF input filter
47K-4.7K NFB Resistors
4.7mA Input bias
Power: 78W 8ohm (2x42V)
Input sensivity: 1.25V
Slew Rate: 8V/uS 8ohm/1nf (JFE2140)
Slew Rate: 9V/uS 8ohm/1nf (LSK489)
Bandwidth: 5-75khz -3db
DC Offset: <500uV



EPIC S Output Noise

Hello,
I'm building a P3A amp that will be paired with the ESP tone control preamp. The pre already has an output cap so I'm wondering if there is any reason to keep the input cap on the P3A, and if not, could I also eliminate R1, R2, & C2?

Earlier in the Le Monstre Preamp thread, we posted schematics and spice files for 3 different line level buffers.
www.diyaudio.com/community/threads/preamp-for-hiraga-le-monstr-2024.421562/

They all have JFET inputs and use 4 complementary transistors in total.
We have now built and measured them all, as shown in the pdf attached.


Patrick

.

Hi

The big thread of "100W Ultimate Fidelity Amplifier" is a chaos.
i need time to search through all the page and mark all i can find.
pcb is done in yellow by jlcpcb.

Gerber and all other documents are in post 13908: here
input BJT i use the recommended KSC1845, driver are 1381 and 3503, power mosfets are the renesas 1058/J162
as C4 it is written 220µF, and XRK use a polymer elco with 330µF. I use a orange 1000/16VµF by epcos
for C9,C16, C12, C15 i use Panasonic 680µF/50V
input cap is a red polymer panasonic 2,2µF/400V instead of 10µF
i use the lower gain setting R11, R12--> 550R and 20k
i did my first output coil...its not nice done but it has about 0,9µH the resistor is under the pcb

bias setting:
post 6686 bias at 100ma-170mA, wrote about goldmund amps--> bias 200-300mA
my bias is set according to the hint of post 7753 by bimo to 400mA. the amp is working fine.
post 6971 test by XRK as an Class A amp with 1,3A works fine...big heat sink is needed!

i used for the first test a 0,65K heat sink.
i plan to use a 4U/300 case by modushop with a 300VA 2x24V sec. transformer

i will just check the other channel.
psu voltage is 31 per rail and bias is after 2 hours 420mA stable. no heat problems, no smoke..

Gain is about 31dB, at 8ohm load about 29WATT.

if you have any hints , let me know.

edit:
Apex directory - done by XRK ..thx:
here:

edit: 26.8.2024: set bias current back to 400mA #post 104
edit: 25.03.2025: post 123 latest PCB Gerber by Peter(Kleinhorn) - thank you!
post 123

kr
chris

I have a distortion in one of my tweeters on my 3-way. The distortion occurs only at certain frequencies and above a certain volume. The distortion is pretty deterministic, I can reproduce it. They are old 3 ways energy speakers from the 2000. I managed to isolate the distortion problem : it is only one side, and because I can bi-wire it, I can confirm that the distortion is coming from the tweeter and not from the mid or bass (because mid and bass share the connector).

I also swapped sides of the amplifier, so I know it is the tweeter on the speaker and not the amplifier that is problematic.

The screw to remove the drivers are not accessible (see: https://rvb-img.reverb.com/image/up...,t_large/v1639605839/olidljagmyhg8zmbkcx4.jpg), so I would like do the debugging and part sourcing before taking them apart.

Is there something I can do to pinpoint where the problems, i.e. crossover, dome, magnet, voice coil? And the potential solution?

Thanks

Few years ago I build Seas based speakers. (T25-001 and W17E-002). Speakers was my own design, even filter.

I was quite satisfied speakers sound to the moment when I get chance to listen original Jamo Concert 8 speakers. After that I was not satisfied anymore


So my question is that, does anybody have Jamo Concert 8 (Jamo D830) crossover schematic?

I have seen some pictures taken from that crossover board, but component values are not clear to me.

Picture shows how components are placed to board.
Red are capacitors, white are resistor and black circles are coils.

I got the proto of the s.e. trafo with multi tap
5 kohm, 43% and 20% UL
5 ohm single secondary
around 20H
primary wire 0,28 mm diam - Rdc 140 ohm
max Ia around 200mA
Pmax around 10 watt, column 40x45,
M3 - 0,3 mm. o.g.
4,4 kg




This is not available.

To play in the real world not in virtual
Testing some circuit.
Unfortunately I have to service now my Sofia ( some hard problem) then I can test the tube that will play in the circuit
proposed


Walter

Good morning

I am building a clone of the SUGDEN A21 amp (class A) and want to associate a very good preamp with RIAA, tone control.
That of ELEKTOR 2012 caught my attention. To validate the quality of the PCBs manufactured by JLCPCB, I ordered the tone corrector part from them. Superb quality.

Now that I am sure I can have PCBs, I would like to have feedback from those built or use/used the Elekto Preamp 2012 or want to go in the same adventure than me!
So any feedback from this preampli would be appreciated, going to build it alone with no support is a bit hard.

Please let me/us know

Georges

Morning all. I joined in hopes of finding drivers to refresh a Fischer & Fischer SL 1000 speaker built in 2000. I purchased the speakers used. I'm looking for Seas W17EX002 bass woofer preferably in black. Unfortunately, this particular Seas woofer is long out of production. The original speakers are in white, but I'm trying to redo the speakers in all black. If you happen to know the crossover points for these speakers, please let me know. Thanks.

Hi Everyone,
I`m an EE student, loved music since i was born. I`ve been on this forum for a while to gather info and ideas since there`s plenty. Have a great time.
Marco

Another, more powerful Woofer. Also - could I use a compression driver? I have these small speakers. For homework.

Hi all, I signed up here years ago, so I suppose that at some point it's time to say hello.

Hello.

This might be a silly question, but I've been wondering if there are any tips for listening to parts of a multi-way speaker individually?

I've been working on some multi-entry horn ideas, but want to test out various parts individually to get a feel for how they sound before commiting to a complete build around certain drivers.

It got me thinking of using an existing speaker and just EQing out the range of interest and then using it to "accompany" the driver in question.

Please let me know if anyone has ideas about this.

Hi
in attach the first proto of 300B OT with nano
It is 3k primary
5 ohm secondary (single)
Around 40H -100Hz but some adj with gap will be possible.
At the end it will be potted.
The first test are almost fine.






The Freq. answer; there is a little step at 50kHz, but it will be fixed
Zs are 700 ohm (blu) and 1 kohm (red)
At thr moment out of the power stage that will be ready soon



The phase

cancelled due an error

I saw a simple amplifier but thought maybe I can do it better without to many components.
Here is the result. Its not very temperature stable but in class A it gets less hot the louder you play.
So it is just to measure the current in the output transistors = voltage over R8 or R9 and adjust it with P1 to
a little more than Feed voltage / 4 * R speaker. But take half an Hour for the heat to be stable after the last adjustment.
It is easily adapted to other voltages and speaker impedances. Distortion is about 0,1% which maybe some people don't hear.
Noise is extremely low under 5 uv 20 - 20k. Common mode rejection is determined by C2. Frequency response is good 25 Hz to 95kHz -3dB.
View attachment 1418335


But looking at the results it is possible to do it much better. Faster and much lower distortion but a little more noise.
The problem now is that the P1 is very sensitive in adjusting the current.
Now the anti thump + radio interference filter on the input is included. But still pretty simple.
I changed the R12 to 0,82 ohm because I believe the IRF 540 has about 5S at about 1A.

I want to buy 2 prasis crc pcb with lt4320.

Glad to finally be a part of this community, appreciate the wealth of knowledge on this site!

Hey I'm having trouble understanding exactly how I can control volume from my TV remote. I really wish TV's still had a volume controlled RCA analog output but here we are. I only have an optical out and HDMI ARC port. Is it possible to use one of those HDMI arc to analog audio converters so I can use the RCA output to my amplifier and control the volume with the TV's remote?