3rd order harmonic distortion. Just cant get rid of it, can you. If the thunder dont get ya (tubes and transistors) then the lightning will (transformers and speakers) Where to begin?

Hi everyone, thanks for reading. I have an anthem MRX 710 receiver that just recently shutdown itself every time I tried to power it up. I performed a visual inspection and nothing obvious like open caps or burned components were observed. I spent several hours looking for a service manual or schematic and that seems to be a highly closed guard secret since none was found. I contacted Anthem and unfortunatly they do not sell replacement parts. They required you to send them the receiver (shipping is really expensive due to the weight) instead. I feel comfortable doing basic electronics troubleshooting, so I will really, really, really appreciate if anyone can provide some hints/suggestions/ideas about what to check/test. Your help/ideas will be greatly appreciated.

I'm in day 3 of learning LTSpice, finally dragging myself into the 90's, and I am wondering if there is a repository of Spice models for active devices (SITs JFETS, old MOSFETS etc.) that are used in the FW/PASS/ZEN etc. designs? I have looked around here but only find smatterings of devices in the last 20 years. If there isn't maybe we could start one?

Thanks!

Paul

Recently witnessed a 1970s pioneer spec 1 preamp at my friend's home. The sound appeared to have more dynamics and live.
On looking at the schematics, noticed they used +/- 48 volts supply with transistor based circuits.
And all the earlier discrete preamps were complete class A operation from input to output.
Most of the modern era instrument preamps with IC use only +/- 15 or 18 volts max.
(The opamps cannot be really set to class A operation)
Not sure to say, if high voltage supply like +/- 48 volts play important role in the dynamics.
The later models from that era use lesser and lesser voltages, like +/- 40, 30 24 volts etc, still transistor preamps.
I am aware of discussions why just 9 volts is enough in the pedals for 150 mv outputs, or +/- 15 is enough for the preamps to output up to 10 volts rms.
Anyone made any discrete preamp at such high voltages with any success?
Regards.

What is the best way to create a uniform slope across a very wide band, for instance a -1 dB/octave slope spanning from 100 Hz to 10 kHz?

Based on a PM discussion recently, I thought this information might be useful to some people. For audio professionals this is probably simplistic and obvious, but some people might benefit from it.

I have found a second order shelf filter with a very low Q is the best way. The attached graphics show how this is done, and how it compares to an ideal slope. I am showing the specific case of 100 Hz to 10 kHz, which has a span of 100x. i.e. 10,000 Hz / 100 Hz = span of 100x.

This technique works well for up to a span of 200x, so it can be used from 100 to 20k, or from 50 to 10k. If a person need a span greater than 200x, they will probably need two shelf filters to get the job done.

I included some example calculations so anyone can work out a solution based on their own needs.

j.

Sorry to bother you with another simple question. I am planning on DC heating some driver tubes with the Pete Millett regulated DC boards. If I want to elevate the circuit, do I tie the virtual center tap I'd create to the voltage divider or is there another way of accomplishing the elevation? I am not sure how elevating the center tap would effect the DC boards.
Millett Boards

How much power is max. pr side for a standard FirstWatt chassis?
I have two of these (clones) made for mono block use (was intended for a J2 project).
90W pr side is too much, I guess?

The heatsinks have relative long fins.......but not long enough?

Hello,
My 3way Diy speaker is using
Tweeter 6ohm
Mid 6ohm
Bass parallel 2x6ohm @3 ohm
Passive crossover and running time is almost 3years .withen three years
I got problem
1: bass one driver damage
2: using bi amp and bass power amp blow
3: another bass driver damage
4 : last week one tube power amp also damage
I carefully thinking problem isall time from low past driver .
6ohm driver parallel 3ohm loading any effect for power amp or driver .
Can I need to change series instead of parallel?
Pls help me .

Greetings DIYA members

A while ago a friend gave me an empty Proton D1200 with all the internals removed. These are quite a good chassis with very nice looking VU meters so I've decided to refit it with DIY modules. A new chassis and meters would easily cost a few hundred $ (AUS) - reason enough!

This is a one off project and unlikely to be repeated, unless you have an empty D1200 as well, but I'll be sharing all my ideas, schematics and layouts that may be of use for other member projects.

Naturally there will be discussions along the way.

Cheers
Q

Is this good for speaker stuffing?

It's not dense, I can weigh it if that matters, just need to know if there is a standard volume/configuration that would simplify comparisons.

Can someone tell me what a better drop in replacement for the NE5532 might be? I got a DAC kit from China for really cheap and am putting it together. It uses the NE5532 opamp for output. It has the nice plug/receptacle on tue board that the NE5532 fits into so it could be easily pulled and switched. I am fairly new to DACs and opamps but have heard there are much better opamps than this one.
Thanks for your advice!
Jeff

Post here for your SlewMaster builds!

quan said:

Hi Jason. I would like 2+ Symasui please. Do all transistors need to be match?( also those 0.22R resistors).
Quan

Click to expand...

Hi Quan,

I think you may have misread the silk screen, there are no 0R22 resistors on the Symasui IPS, but I could see the confusion with R22 being a 22R value. When I put the value on the silk screen it will always be 'inside' the silk pattern for the device, the schematic designator will always be visible when the device is installed.

I would do a basic matching of the TO-92 devices, no need for obsessive pursuits.

any one has schematic for B&K st-140?

really appreciated

tks

Tube Anode choke, 2x.
150$ + shipping.

This...

Alright, can't seem to figure this one out, not helped by the fact my Google-Fu is not what it used to be due to excessive intake of sugary treats (it is Christmas afterall).

I have a schematic drafted where I want to label a number of nodes with their DC voltages in a transient analysis.

I do this by simply left clicking on the nodes in question, et voila, the DC voltage shows up. However, it shows up formatted with 5 decimal places, which is a little too much. I'd like to round that off to one or two decimal places.

If I however right click the node and add the expression 'round(V(a1))' to round off the voltage at node 'a1' it rounds off to no decimal numbers, which in my case means that 1.38798V is rounded to 1V, that's not what I'm after, I'd like to see either 1.4V or 1.39V.

Any of you fine gentlemen know how to accomplish this undoubtedly trivial feat? Thanks and Merry Christmas!

Finally starting construction of the SEAS A26 speakers.

A while back I started a thread in the Pass Labs area, but it makes sense to move it here until the load is ready for an amp.

I've built a few other MDF flat-pack kits, but this will be my first kit from a full sheet of real wood. I'm using it as a tune-up for my skills and to get familiar with techniques and tools. I have a new track saw and a router with the necessary bits (no table saw and no elaborate shop).

All the components came from Madisound. I opted for Mundorf SGO caps and will stick with the SEAS circuit values initially. Material is good quality Baltic Birch @ ~18mm thickness and 13-ply. Interior will be lined with GR Research No-Rez.

I'll follow the SEAS cabinet plans for exterior dimensions and openings. Edges will be joined with rebates and then flush trimmed with a router after glue-up.

One area I'm not yet committed on is the interior bracing. I know I want some, but I'm not sure of the best approach. I'm tentatively planning to use the "World Designs" method implemented here. This approach was also published in 2006 for the floor-stander WD25T variant by Peter Comeau. Supporting the magnet structure seems like a good idea and is endorsed by SEAS, but the vertical brace behind the woofer strikes me as odd. Any opinions on this?

Some pics of yesterday's progress below. Any hints/tips/recommendations along the way would be appreciated!

BK

I got this amp dirt cheap from the Reverb app because the seller said the reverb doesn't work. After trying it out it seems like the only thing wrong with it is the knob on the reverb pot is missing. Anyway I've gone online to try and find more information about this amp but to almost no avail. I wondered if anyone could help out?

Hi Folks,

Ive been playing with the Ideas of building a pair of 12" full-range speakers with Audio Nirvana drivers and plans. I have zero experience with full-range drivers.

I currently run a 25wpc DIY tube amp into a pair of Dalquist DQ18s . My system sounds pretty great at the moment, I just think it can sound even better with a different speaker setup. The full range 12-inch speakers look the way to go if they sound as good as they seem to suggest.

ANyone have any thoughts here or opinions? I'd love to hear.

Thanks

Tim

I inherited an Oracle Delphi MK ii from my father as a basket case upon his passing. After replacing and restoring the Micro Seki tonearm and replacing the broken needle Sumiko Talisman cart with an Alchemist, swapping power supplies and eventually the PS Audio moving coil preamp the TT was working great for a while.

Then it started slowing down… and down. Kept adjusting and would find it had some wild swings between 31 and 36 rpm. Different every time I turned it on. Replaced the belt, cleaned the platter etc and have not resolved it.

To point me in the right direction, the motor decided to start making a cyclic “scrubbing” noise all of a sudden. So, I pulled it all apart hoping to be able to clean and oil the motor. No luck. Sealed unit mounted to a board.

In playing with it, I unscrewed the bottom graphite slot head screw on the motor and it came to life, spinning smoothly and effortlessly.

Reassemble and it was able to be adjusted to perfection. Listened to a dozen records in the last three days and was very pleased with myself, but now it just stopped turning altogether and when coerced into moving it does so slowly and with lots of scrubbing noise.

I assume the motor has spun its last record.

Are there any sources for used Oracle Delphi parts, or a direct replacement motor? I’m handy, but not knowledgeable. Oracle wants $2300 for an upgraded motor which simply isn’t in the budget.

Thanks in advance.

This pair is in incredible original shape. 8 ohm. They were used lightly (if at all) sealed PA boxes. They are a musical instrument/guitar speaker. Extremely sensitive. I've heard they can be re-coned in to other things. $150/ea $250/pr. I'll consider offers and will ship at cost.

Paul

Hi all,

I've been and an amateur DIY enthusiast for some time now and have embarked on a very haphazard mission to mod some speakers.
It goes within my understanding the best way to upgrade a speaker is: Crossover components, wiring, tweeter.

What I have been advised is changing the tweeter is often a good way to improve sound, however swapping the woofer as well as this without testing is likely to fail. Crossovers were designed for the interaction between them and the woofer right? Then minimising distortion of the drivers within the cabinet.

So a straight swap won't work? In theory you'd be lucky. I just wanted to share a very genuine story about how it did.

I took the Roksan TR5 S2, the Fountek Neo 3.5H, Chord Odessy for internal wiring and and the HiVi mag/alu drivers,: https://www.ebay.co.uk/itm/274376866493

While the tweeters are rated at 96DB and are a little loud I think they have integrated beautifully. I've had to chisel into the cabinet to fit the drivers and the woofers are a tad small for the cabinet recession, what I have done very easily, and relatively cheaply, is created and absolution stunning hybrid speaker with very little work and technical knowhow. Im utterly stunned.

Im using Maranta KI pearl CD/AMP combo and Chord Sig speaker cable and jumpers.

Any comments on obvious dangerous mistakes or thoughts would be great, Im looking into an L-PAD to attenuate the tweeter but so far am not compelled, they sound crisp clean rhythmic and balanced.

Happy to post pictures in due course

Kind regards
Rob

I have zero knowledge but want to build a nice tube amp. Can i start from scratch as an old 50 YO alcoholic not taken this very seriouys?

Hello there,

When the Gain Card was announced and it is still around for about $3.5k at Sakura Systems. I made a 3876 with a 'better' power supply four 10k uf caps etc. I thought it was wonderful. But as you do I bought a 3116 class D for a fiver goodness gracious! I could scarcely believe it. Bit shrieky at the top end though.

Going back to the Gain Card I found Mick Feuerbacher's site and this.



R1 10k log pot
Rf 22k 0.25W carbon
Rg 680R 0.35W metalfilm
Rm 10k 0.35 W metalfilm
Cs 2200 uF and 100 nF in parallel
Connect pins 1 and 5

No need at all for a PCB point to point is much easier.

The power supply is a toroid and some diodes nothing else. I'd got a couple of 3886's and made the above. This of course is just my opinion the 3876 with the large caps is warm and pleasant in other words nice. On the other hand Mick's 3886 is fast, detailed and analytical.

I've listened to it for about five years now it's quite simply the best amp I've ever made. I understand now that if you like the detailed etc then Mr Kimura's Gain Card is an Ace amp. There are going to be lots of detractors following this post, may I humbly and with great respect say please make one for your self.

Cheers - J

Replacing outputs with IRF3710. Should I stay with the 47 ohm gate resistors?

So I was in local hardware store yesterday and saw some laminated hardwood. They are still real wood expect they've been "glued" together.

Saw various types like bubinga, acacia and others.

Can these be use for speaker cabinets? Thinking of using it for the top, front and sides.

Thanks

(I bought one last night to use as a shelf and it's around 4ft (L) x 1ft (W) x .75in (thickness)

Other bigger sizes are available. Thanks

Recommendations for a good dc motor for a DIY turn table( belt drive)

Hello everybody,

I have to state that I am not an expert: my first goal is to understand more.

For some years my Cabre AF-25 power amp has been humming through the speakers so annoyingly that listening at low volumes is really unsustainable. Lately I also noticed that the right side of chassis got very hot after a few minutes even without load, so I went to a professional for solving the problem: he repaired the right final stage (which now doesn't get hot) and replaced the electrolytic capacitors. He reported he didn't hear any humming after the job.

Back home, however, I noticed, with regret, that the buzz is always there. A few more indications:

• the noise is very loud when I disconnect the input signal from the final, and it decreases, even though well perceptible, with the preamplifier connected. If I connect the preamp to one channel only the noise is louder in the detached channel. The intensity of the noise also varies according to the position of the potentiometers of the output levels of the preamplifier (louder in the middle, quieter at the beginning and end of the stroke);
• the speakers have nothing to do with it because I hear the noise even with the Stax from the amplified output and from the headphone level output;
• the noise is heard from all three speaker ways (I don't have an oscilloscope but analyzing the spectrum of the recorded sound it seems to me there are harmonics, I would not say a stupid thing);
• the hum is latent, in the sense that it can occur immediately or at a distance of a few minutes / hours from switching on. I have also noticed that sometimes it can go away by restarting the power amp a few times, maybe disconnecting and reconnecting the preamp between one restart and another, too. I must say, however, that since I got it from service the noise seems more persistent than before, even if slightly quieter.

This last consideration makes me think of the capacitors, which have also been replaced. Actually there are a couple of large ones that always seem the same to me: I don't think they have been changed, if this consideration has any value.
I have never fully understood how impedance works, but the first point suggests that it has something to do with it and can help me pinpoint the cause of the problem in the input signal path. But I can't go further than that, also because I don't have any diagram.

Do you have any ideas? Any opinion will be sincerely appreciated.
Greetings from Italy

Hi Guys,
I came across an old thread where DBMandrake suggested making a little dent at the edge of the dust cap on Coral Flat 8 to mitigate Oil Drum effect.
Can someone confirm if dent at the edge is referring to edge of dust cap to speaker cone or ?????

Many thanks in advance

Hi,
I have found a Lenco 830 DD turntable and it seems to have an issue with the speed.
The 45 runs fine, but it is the 33 that is not stable. That is, when you switched from 45 back to 33, or
when you turn the power off.
If the speed is set at the correct pace, and you let it run, nothing seems to be wrong. But it is when you either turn off the power or
change the speed that the problems occur.
After an action like that, the 33 is either slower or faster than it was. It does rotate at a constant speed, not fluctuating during the rotation of the platter.
The motor control drive circuit isn't that big but it has the AN620 Matsushita chip on it.
It tried to clean the trim pot, but that did not solve it.
I swapped it out for a new one but that did not do the trick either.

With noting that I have a basic understanding of elec. I want to ask for help with this.
Could it be a faulty AN620 or maybe a resistor gone bad?

The servicemanual I managed to find on the net has a fault in it also, in the parts section it shows that the VR 1 an 2 are both 5K Ohm pots.
The diagram shows 20KOhm, but what's in there are 30K if I am correct. (303 code on both of them)

Had anybody experience with tweeter what can be filtered at 1 kHz?
I know one, Dayton AMTPRO-4, but is is too big.
I need to fit it to smaller space, good if it is some type of ribbon but also dome type options can be suggested.

Hi All,

I'm new to the DIY speaker building and hope I am posting in the right forum.

I'm in the process of constructing a 3-way floorstanding speakers with a tweeter, mid driver and two 6,5" woofers each (low to mid crossed at around 350-400Hz). I'm aiming to tune the box at 43Hz which using WinISD gives me about 20,5cm lenght of the port with 10cm width at 45L inner box volume. When taking away 18mm thickness of mdf panel which this port will be mounted in it gives me roughly 19cm of the port lenght inside the enclosure. Port is made of 2mm thick PVC pipe.
Therefore my question is, do you think at that lenght (and width) the port inside the enclosure might have some unwanted vibations at higher levels? Is the port too long to be just on it's own without any additional support i.e. some sort of bracing for the port itself to stop any potential vibrations? I'm guessing it wouldn't hurt it but is it necessary as it would obviously take extra work and additionally take away the enclosure's inner volume which I've not accounted for?

Or are the vibrations I am concerned about simply a "first port resonance" which WinISD is showing at above 700Hz (I don't remember exactly as I don't have my laptop with me atm)? If that's the case then I don't think I should worry as the woofers shouldn't be having much output above 500-600Hz given the ~350-400Hz Xover point...

Taking to account Xmax of the speakers I will be feeding it a maximum of 60W per channel.

I guess I still have a lot to learn regardless...😄

I would greatly appreciate any input on the matter😉

Thanks in advance!

How many different Main Boards versions did Yamaha use in the CA-1000?

Apparently there was a number of additions/changes, the boards are marked with different NA numbers from the schematic. They are also rubber stamped and not silk screened on the board.

Also seeking Technical Reports for the CA-1000

Looking to design and build ported isobaric subs with 18" Lavoce SAF184.03 drivers. I was planning on configuring the drivers cone to cone with the magnet facing out, having the drivers recessed into the enclosure front with a grille to hide all of it. The ports will either be exposed to the floor or front depending on what is better at controlling potential port resonances. This may become an issue having a smaller than usual ported enclosure together with a relatively low tuning frequency (need for longer ports).

The driver spec sheet is attached below. I'm trying to get the best / lowest distortion performance, so I'm open to suggestions regarding enclosure design. The main goal with the isobaric design was to reduce the enclosure size to a practical extent while not sacrificing low end extension (-3 dB cutoff closer to 30 Hz). I wanted to keep each sub under 30" height, 20" width and 24" depth. I have a choice of running the subs with a QSC GXD8 or 700 watt Speaker Power plate amps. The QSC does about 1200 watts @ 4 ohms/ch.

These subs will end up weighing a TON with 2 large ferrite magnet drivers in each. The design is mainly meant to augment sub 100 hz low end, focusing on musicality first and foremost. The port(s) will need to be large enough in cross section to avoid compression and noise, but small enough to practically fit length wise.

Man I really need help from people with better ears and more audio electronics experience than myself !!!

Do DAC topologies have a audible effect on the analog output, is an r2r DAC going to sound characteristically different to a delta sigma DAC ? , given a compatible line out.

Or do all DACs sound basically the same, with differences in sound attributable to varience in line out impementation, the great open loop vs closed loop debate ,and whatever processing occurs due to the inherent problems associated with da conversion, ie aliasing.

I thought I had a handle on the whole subject , but having recently bought a dx90, and done a shed load of comparison with a bunch of other audio sources, my confidence in my own abbilty to pull all the factors apart , is shaken.

Would it be fair to say all DAC issues come from the transition between one bit value and the next ? Be it from the electrical switching noise or from the fact there is a straight line there, and defiantly not in the analog trace ! In which case topology could make a difference.

This site is full of good engineers and lots of experience, hopefully someone can take the time to reply
Thanks

I've been looking at OBs and also a relative has a set of Bose 901s that I've not heard , but it got me thinking, wouldn't the direct/reflecting nature of Bose 901 been far simply achieved with an OB? Or is there something in the nature of the speaker design (delay/phasing) that meant a straight dipole speaker would not have been able to achieve the same effect?

Looking to buy Firstwatt B5,4 ,F2J, SIT-1, SIT-2, SIT-3 and any DIY alternatives

Looking for single ended jfet or sit 0 feedback amplifier
Single ended 0 feedback preamp

Active crossover boards

Long story . . . I obtained a JVC 6ohm front-loaded, ported subwoofer with a seemingly incurable rattle. As with many big-box products the unit cannot be disassembled. Rather than throw it out, I did a thing. I found some feet, cut a hole in the bottom of the cabinet, fixed the rattle, and installed another 6 ohm driver into the hole I'd made.
It all sounds great but it's 3 ohms and I don't know how much longer the amp can cope.
I could wire the drivers in series: 12 ohms. Or, I have a 5 ohm resistor that I can utilise. How can wire these to get close to 8 ohms?

I installed a S/PDIF (Toslink) cable from my PC to the PT696BT so I can use the 5.1 setup. When the amp is idle (no playback), I get an intermittent popping or clicking sound. When I use a standard 3.5mm audio cable, there is no popping sound. Can you help me?

I still have a pair of Seas H175 33F-ZBX/DD woofers brand new in the box, that were never
installed, and are in perfect condition.

I purchased four new 13" inch Seas Woofers for personal use at Just Speakers / A & S speakers in San Francisco, before they were discontinued, two I used in my car subwoofer cabinet with a Linear Power 300 watt amp, and are also still in perfect working condition as they have been in storage since 1995.

The other two I saved in the box, as I had planned on building my own sub woofer cabinet for home use and never got around to it.

If you have a customer looking for replacement woofers that have an interest in them, I can put them up on Ebay, that way they can use Paypal to guarantee the purchase, or if they live in the Bay Area, I can meet them in person with the woofers.

Regards,

Jose F. Medeiros
josemedeirosforsenate13(no-spam)@yahoo.com
Jose Medeiros (Jose F. Medeiros) on Myspace

What's the consensus, in the right hands, would a light sabre make an awesome bass synth?

Hi,

Am new to vinyl. I listened to only vinyl in my school and college days in the 70s and 80s, and then completely lost all connect with vinyl. Now I've just bought a used turntable and have collected some vinyl, and am encountering all sorts of info about vinyl album versions.

First question: about the ABBA Live at Wembley vinyl. Why is the 2014 issue so much more expensive than the 2020 reissue? Is a reissue LP stamped from the same metal master as the original, or do they start from mixing and mastering, etc? If they are both from the same metal master, and I am presuming that a good record label like this one, plus metal masters made with 21st century technology will be... well... long-lasting, does one expect to hear significant audible differences between the 2014 version and the 2020 one?

Second: I bought a sealed new LP from a shop in Singapore: it was Harry Belafonte's Carnegie Hall concert. The cover art was not the same as the familiar RCA album photos, and the record label was unfamiliar to me, but I paid it no need, since it was four years ago and I had not heard stories of the corner-cutting new-age vinyl makers. I've attached two photos of the album. I wanted to know: is this Vinyl Passion label similar to Wax Time Records, who pick up CDs or any other questionable masters, tinker with the sound, and then make vinyl to sell to buyers who don't know the difference?

As a novice getting into this field again, should I be careful about these things?

(I know that CDs too are released in various versions, often remixed and remastered, but I never encountered stories of CDs manufactured by questionable companies using material of unknown provenance. Maybe I just bought well-known labels.)

Hello,


I've got most of my Priboi in LTspice, at least the important part. Anyone of you have models or parameters for the GU-19, GU-29, 6R3S ?

I am also try to make the Priboi transformer in there, anyone has some good strart values ?

At the moment I am making my teeth with the 829, seems to work. I'll try to make me a spice curve tracer unless someone has one ready to suggest.

I'm servicing a US military surplus tube-regulated power supply and ran across this schematic symbol (47) which I have never seen before.



It looks like a big, fat glass cylinder (in between the tubes and the fuses) - can anyone identify it?


TYVM,

does a whizzer full range do better intelligibility than a non whizzer ?

I've always wondered about this.
Don't whizzers usually come in high, like 7khz ?


Norman

I fired this amp up for the first time in a long time after a friend replaced the 6CA4 rec tube. Here is a video of the problem.

Login to view embedded media

I need an LDO to reduce 36V-52V down to 30V. It is not really a critical application and current draw is very low, >5mA. Any ideas?

Hello all! I'm new to this site, and I've come here for one main reason: unlike a number of other forums I lurk around on, you all really do seem to know what you're talking about. So, I have some questions for you all about two different Yamaha power amps. (And from the discussions I've seen on this site, these will likely be insultingly simple questions, so I apologize in advance for my naivete). Here's the deal--I'm looking for an amp to power my Yamaha NS-10s in my little studio. After much research on amps, thoughtful reflection on my needs, and fretful consideration of my budget, I've pretty much decided to go with a Yamaha P2150. But here's the issue--there seem to have been at least two different versions of that amp made. One is the standard P2150, and the other is the P2150C. They have quite a lot in common, but they are different. The standard P2150 is pretty straightforward as far as the input/output connections go, but the P2150C is quite different and seems almost designed for a specific kind of use (even its attenuator knobs on the front are smaller and differently shaped). Anyway, I'm attaching pictures of the backs of both amps. If anyone can tell me anything about the C version (it's the one with the Transformer In/Out switch in the input section), I'd really appreciate it. What I'm interested in most is why the C has screw terminals, what the Transformer In/Out switch does, what the large, round inputs in the Input section are for, and how difficult repairs on this amp might be (for a pro to do, not me). I've scoured the web trying to answer these questions for myself, and I can't even find a manual for this thing. All I know is that the one I'm looking at came out of a church. So, any info would be much appreciated.

Clearing some odds and ends before the baby splashdown.

Mark Audio Alpair 7MS 4" driver. An exceptional speaker driver. Unfortunately I damaged the other one so have this one taking up space. Perfect for someone looking to complete a surround set up. You are welcome to the damaged driver if you want. With Original box and rubber gasket installed.

It has never been abused and only ever used crossed over at 100hz with a sub.

Cheapest in the UK is £120

£25 POSTED TO UK.

https://www.markaudio.com/online_shop/alpair/alpair-7-ms/

RE 7.2 Ohm
FS 74.724
SD 50.270 cm²
VAS 4.968 L
CMS 1.384m M/N
MMD 3.072 m KG
MMS 3.277 g
BL 3.859 TM
QMS 2.350
QES 0.744
QTS .565
LE 124.716 uH
SPL 86.324db
X MAX 4.5mm one way
POWER (NOMINAL) 15Watts

Empire 2000E/III with good stylus, very well balanced electrically $50
Sonic Sonus Silver needs stylus (aftermarket appears available from Japan.) $60
or both for $100 + shipping

I’m trying to install a single 12” woofer with an amp in a 08 Ford Focus .

He is using the factory radio right now and also bought a line out converter .

I tapped into the rear door speakers and hooked everything up and it’s the worst thing I’ve ever heard it’s not loud at all and sounds distorted .

I hooked up the same 12 and amp in my truck and it sounds amazing .


Here are pics of the wiring for an 08 focus . Did i do something wrong by splicing into the wires at the rear doors?

Or if I hook up the wires accordingly is there such a thing as 1 input being out of phase on the line out converter ?

Must have dark inner sleeves with white writing

must be in very good condition.

I know that's asking a lot. 🙂

It was the best thing since sliced bread. Go back and see how it started.

https://www.mentalfloss.com/article/642374/vcr-history

https://original.newsbreak.com/@jam...-how-did-top-gun-create-the-era-of-home-video

I have lots of tapes and a non working vcr. Time for me to move on and dump the vcr. But I still have good memories when vcr was king.

Hi, I had some of those tubes, is they good for Phono stage ? I only found one schematic from the old forums, do anybody had build Phono stage
with those tube? Any opinion are welcome.

This is one of those things I thought I knew then suddenly find myself unsure of. I'm trying to figure out my power requirements for a set of tower speakers I'm building. The main driver I need 30w in to a 6.93Ω load to drive to xMAx, it's single voice coil.
P(w) = v² / R
v²=P(w) * R
207v²=30 * 6.93Ω
sqrt 207v²=~14.4v

i = v / r
14.4V / 6.93Ω = 2.077922A

~14.4V @ ~2amp is the power requirement for the main driver to drive to xMax

That part I have down. Where I start getting lost in my own lack of math skills is when it come to the low fs drivers. There dual voice coil, each coil is 3.25ohm, the plan is to wire them in two parallel sets of three coils.

WinISD tells me I need 135w (29.6v) for each driver with 2 coils in series (6.49Ω) for one driver. What WinISD does not tell me is if that voltage requirement is RMS or P2P. Does anyone know?

I'll have three coils in series 9.73Ω across 1.5 drivers in two sets parallel 4.87Ω.

My bad at math brain tells me;

v²=P(w)*r
v²=135*9.74Ω
1315v²
36.25v

i = v / r
36.25v / 4.87Ω = 7.44A

So if I've done that right, I need ~36v @ 7.5A to drive all three drivers to xMax. So am amplifier with 300VA+ power supply @36v should provide the current. So something rated 330w @ 4Ω.

Again, I'm bad at math and prone to making simple mistakes. Have I done the math right?

Hello, I bought a pair of Peerless SDS-160F25PR01-08 and a pair of XT25BG60-04 and I know how to build speakers cabinets but very bad designing them, somebody can help me with the xo schematics and box design please?
I am looking something like this pic.

Hi everyone !

Thanks to this forum I have finally found thé scheme of my RGR MODEL FIVE power amplifier.

I am planning to simulate it and convert it in two mono block (just for fun)

In the plans there are 2 transistors called TN225. But i am unable to find it on the web. Not even a proof of existence ...

Do you have an idea of where i could find it or a replacement ?

Thanks in advance !!

Hi all, i need help with a project based on a mx50se, i need a pot volume, from what I understood i can't just put a pot between input and power amplifier because I would go to modify the impedance by raising or lowering the pot, i need a buffer o preamplifier, i tried a few of preamp based on ne5532 and i don't really like it, they sound really bad, i also found a clone of naim nac 42 by ljm on aliexpress, but it have high gain and with the high gain of the mx50se i would reach saturation with half pot, so i can reduce the gain of mx50se and use another pot, something like 20k but i don't know if this is a good idea, most important, I haven't tried this preamp yet , otherwise i can use a buffer, i think this is the best choice, but i don't really know where i can found a good project not too much expensive with a good quality, most important i need a digital potentiometer that can i managed by i2c with arduino or something like that.

Hi, my Rockford bass amp I had been using in my main system has spat it's dummy, so is now a paper weight. As I had a spare 3255 in my 2nd system I inserted that into my main rig. Boy what an improvement after it passed though my Electronic X-over set to 100hz.
So I went hunting for a replacement & found this thing on Ali-Express. (who having been giving great service over the last several months, some orders reaching me within 8 days, with full tracking support of the parcel, very impressive)
https://www.aliexpress.com/item/1005003335861622.html?spm=a2g0o.order_detail.0.0.4558f19cnlnwud
The cost was a remarkable $45 & I also orders from the same supplier a 35 VDC 5A SMPS for $18
https://www.aliexpress.com/item/33031309629.html?spm=a2g0o.order_detail.0.0.4558f19cnlnwud

So when they arrive it will be very interesting to see how good they sound as a bass amp & how the unit holds up

Cheers

This is a basic question, but I cannot find a good reference. Can someone point me to what is meant by and interactions between 'taps', FFT (Fast-Fourier Transform, I assume) length, resolution, and latency? The first two are configurable values used in constructing convolution filters in RePhase, and the latter two are from Equalizer APO's system analysis tab.

I'm aware that generally increasing the number of taps increases the 'accuracy' (trying to avoid incorrectly using resolution since I don't know the technical meaning) of a filter, but I don't know how what it actually is nor do I know how that interacts with the other three items above.

What I find particularly confusing is that Equalizer APO's analysis tab allows you to set different 'resolution values', and doing so seems to show that the relationship between resolution and CPU use is convex - it's highest at the lowest resolution settings and decreases for a bit before increasing again. I would have expected this to be closer to a linear relationship - CPU use decreases as resolution decreases, but again, not really know what is meant by resolution in a technical sense, I don't know how to make sense of this.

Finally, if Equalizer APO says channel A has latency of 700ms, does this roughly mean that the audio signal has a lag of 700ms? For example, if all other channels have a latency of 700ms, does this mean there's a delay of 700ms before audio starts but everything is processed and output 'in time' while if all other channels had a latency of 690ms, channel A would be 10ms behind the rest?

Thanks. I'm more than happy to read up on good references as this is something I'd like to understand anyway. I'm a mathematician but as an algebraic geometer, never had a need to learn things like Fourier Transform let alone study signal processing.

I find a 18bit Q module for my Cyrus dAD3 cd player and i can not get analog signal out.
Cd player put Q mark on display so that means Qmodule is recognized.
I put jumpers from STD to UGD,clean al connections with wd40,try to put many times Q module in and out,try to put jummpers back to STD,and then every thing again.
And no signal from analog out.
If i take Q module out and put jummpers back on STD,i have signal. But with Q module i cant get no signal. Can anybody help me?
Cd player reads cd always and on the screen everything looks ok,Q mark is there,cd running,but no analog signal.
Help!

Great day guys, could I get any info on the zener diode marking 1P or equivalent that I can use to replace it with.

As above. I checked the datasheet and there's another V+ pin.

Thanks

Hi folks,

Last month i designed/build a small preamp/buffer on a dutch forum. I like to share my experience also on this forum. I used the 6N16 miniature tube in a srpp/ cathode follewer setup. Further i designed a circuitboard and try to use cheap and simple parts for preamp and powersupply.

Some features :

Input voltage: from 10 to 1000mV
Amplification: 12x
Anode voltage rimple: <0.1mV
Output power on delay: 20 seconds.
Printed cicuit board: 100 x 160 mm (eurocard format)

Usable for Dac I/V conversion, CD player output buffer, Preamp, inputbuffer for Hypex class D amps.





Below see printdesign in the pdf file. Powersupply can be seperated from preamp.

http://www.monstercore.nl/6n16print.pdf

Have fun with this schematic.





Ronny

Triggered by this thread : https://www.diyaudio.com/community/threads/compact-diy-friendly-dual-tps7a3301-power-supply.290858/ .
And the high prices and availability of low noise regulators. And problems with handeling smd parts.
I designed a realy quiet power supply with first a capacitor multiplier and then a TPS7A3301 regulator in TO220-7 housing(Cheap and throuhole).
Totalcost with transfomer,PCB and all parts about 20 euro.
I use two of them for dual rail suppy +/- 15V.

Schematic

View attachment 1096604

R1,Q1,C11 are part of the capacitor multiplier. With 200mA load the ripple before the TPS7A33 is only 5mV. With only 3300uf capactor it was 265mV.
After the TPS7A33 noise/ripple is lower then -120db, this is the limit of my measure equipment.

Transfomer

View attachment 1096552

TPS7A3301 TO220-7 housing.
Got the part for free, from the TI sample program.

View attachment 1096557

PCB

View attachment 1102185

PCB size is 50 x 100 mm. Ordered at JLCPCB for 8 euro(5 pcs).
Gerber files for ordering see below.

Ronny

After completing a fullbridge and halfbridge converter and using them to power my amp projects, I continued to investigate other topologies to overcome the disadvantages of the above:
1.EMI
2.Large inductors on outputs
3.Difficulties caused light loading
4.Hard switching and others

I found this forum's help essential to the success of my projects and I am again seeking your inputs and comments.

A big thanks for all help in the past ,I have been bit by the promise of the LLC converter and I want to scale one to a kW.I have read many appnotes from Fairchild,Onsemi and others and one thing stands out,PFC frontend required.. therfore a 1kW PFC will be needed for reliable operation.Fairchild,onsemi and STmicro have controllers dedicated for this along with excellent appnotes and tools.(AND8257,AND8255,AN2450 and AND8311/D.I will start with the LLC design first and to open the project I would like to present a simulation of a dual output llc using LTspice(free spice simualtor).The attached file set includes all models and libraries for the simulation.Included is a single output sim(see appnote AND8255).

Hi, 1st time poster, I have a Pure evoke 3 radio, on mains power it works as it should, when on battery fully charged, pressing standby turns off the radio but it immediately comes back on, there is no way of turning it off permanently without plugging in the charger or removing the battery.

Any idea's please?

I'm using a MiniDSP 2x4HD as equalizer, electronic crossover, and volume control to an amplifier and speaker arrangement. The MiniDSP gets its signal via TOSLINK fiber out of a recent model Sony Bravia TV. The power amplifiers are class D with signal sensing and shutdown and I leave the amplifiers otherwise turned on all the time. It all works great, I get the sound from the good speakers and big amplifiers and the TV does the picture, with its internal speakers turned off.

BUT when the TV is turned off, and after some random number of hours go by, the system will start to make a horrifiicly loud hashy SCREECH sound! Either the Sony TV is emitting random garbage IR onto the TOSLINK cable (seems doubtful, but who knows?) or the 2x4HD's optical input's signal threshold is drifting down to where it is responding to noise and translating it into ghastly audio blasting (seems more likely).

I've been dealing with it for the past year by just remembering to mute the MiniDSP (via remote) after turning the TV off. But when I forget, like last night, I'm afraid the problem could burn out my speakers, possibly even be a fire hazard, if I'm not around?? And in my soon-to-be new living arrangement the TV will likely be operated by others including a child, so I need a simple solution for this.

Is there some sort of box that will switch AC power of external equipment, responding the HDMI CEC as if it were an HDMI sound bar for power on/off? I've tried googling for this and all I've come up with are "HDMI switches", which I don't need -- and I certainly don't need more remote controls!

Or some other way around this problem? Hard to believe no one else has had need to auto-switch power to the stereo when TV is turned off...

Thanks
Bill

I've been trying for months to connect an active subwoofer to a stereo pair of Echo dot 3 and 4 to reinforce the bass because I don't want to buy an Echo sub and above all, I have two or three subwoofers lying around and are useless.
I have almost tried all the configurations (with Jack 3.5, wifi, bluetooth, Echo flex) but nothing to do, I can't get everything to work at the same time, it's either the stereo pair that works, either the subwoofer but never the whole thing.
has anyone succeeded?

Unity gain line stage

This is the story of a project that mutated. It started out with some surprising measurements on a batch of ECC81s; despite their relegation to the lowest of castes by the tube fashionistas, I found that these are very low distortion tubes. Also cheap and readily available. So, thought I, let's make a new preamp. The old one is about to turn 25 and was built in the days when my sources were much different than they are now.

By the time I was done, the ECC81s were history (they're finding application in my next published circuit, a small power amp with LED biasing). And the circuit had mutated into various species, each of which had their own virtues and faults. One of them, at least, is actually pretty novel. They all perform well. And they're all suitable for pedagogical exposition and auditory enjoyment.

My format here will be a three stage proposition (with an intermission to consider power supplies), starting with the simplest, most conventional circuit, moving on to a somewhat unconventional approach, then mutating off into outer space. Each stage will anticipate the next so that this series can be followed as a set of construction/instruction projects.

I’ve gone into rather gory detail about choices of components and operating points; one great priority for me is using parts on hand whenever possible. If I specify those parts, no one else can duplicate it. But with knowledge of how the parts were chosen and how things can be juggled around to accommodate other parts, a relative novice can alter things readily with a good chance of success.

So, here we go....

First step: Define requirements

These days, a preamp is almost redundant. Signal sources in my living room include CD, DVD, satellite/cable, and MP3, not an untypical mix. All have roughly 2V output at a low source impedance. My phono will get its own dedicated step-up/equalizer designed to output a similar voltage. So, we need at least 5 inputs, all high level. My power amps are of normal sensitivity (as probably are yours), so we really only need unity gain. A10K input impedance is fine- there will be no weedy sources allowed in MY system!

There's another reason for the choice of 10K as the input impedance- I'm sold on the use of input transformers. Wait, wait, I see you starting to click to the next thread, but hear me out: given the multiplicity and uncontrollability of grounds in a multi-source system like mine, there is a decided advantage to galvanic isolation. There's also a decided advantage to common mode rejection in a noisy (electromagnetically speaking) environment. And at these signal levels and impedances, you can get good bandwidth and very low distortion. As a bonus, the transformer will do a nice job of limiting bandwidth; though some people have a religious belief that more bandwidth is better, there's precious little (ok, NO) evidence that extending bandwidth beyond 20-25kHz is audible. That's no surprise- we don't have sources that provide signal energy more than an octave above that, at best (and rarely). There is plenty of evidence that the consequences of transferring high frequency junk through the power amp ARE often audible, even with the limitations of program material. The transformer specified will take us to 90kHz or a little higher while not passing AM radio or our local CB operators. The canonical taxi drivers will not be considered. That bandwidth should give us margin to accommodate any currently available signal source and any contemplated sources for the next decade or two. See the white papers at www.jensentransformers.com for detailed and lucid discussion of transformers and grounding.

As far as output drive abilities, we can calculate what we might need. The maximum length of interconnect I am likely to use is 3 meters (say, 10 feet). That will also accommodate 99.9% of the rest of the world. With an interconnect capacitance of 150pF/m (the worst I could find), we need to drive 450pF. Call it 500pF. The power amp will have an input impedance of 10K at minimum, and might add another 500pF of input capacitance, if it's a particularly nasty design. So we have our worst case load: 10Kohm paralleled with 1000pF. The unit should also be perfectly stable into this or any other likely load- this is a restricted club and we do not take kindly to stray oscillations sneaking in the back door.

We want the unit to be quiet. Hum and hiss should be inaudible. Let the analog tape or mike preamps annoy you, not your preamp. Noise below -80 dB from full output is acceptable in real rooms, so let's go a factor of ten better and insist on -100dB.

OK, we know what we want to accomplish. How do we do it?

Second step: Basic design outline

Starting at the input, my choice of transformer is the Jensen JT11-P1. It's a 1:1 input transformer, optimized for a 10K load, with great balance and common-mode rejection, low distortion, and not terribly pricy in the US. In the UK, Sowter makes a similar-looking unit, the 3575; the specs aren't quite as nice-looking, but it appears pretty satisfactory. The CMLI-15/15C from Cinemaq is supposed to be equivalent to the Jensen, but at a lower price. If you really want to go on the cheap, I’ve heard good reports about the Edcor WSM 10K/10K, and they're under $10 a pop.

We don't want to load the transformer with capacitance, we need a low output impedance, we need unity gain- are you thinking what I'm thinking? Sure you are- we want a cathode follower. Ultra-high input impedance, ultra-low input capacitance, high power supply rejection, easy to stabilize, ultra-low distortion, and low parts count. Yes, I see you wriggling in your chair a bit- you read somewhere that cathode followers sound awful and have all kinds of performance problems. Or a "knowledgeable" buddy of yours told you that. Whatever. It's just a crock, and it's a crock that was fired in the kiln of incompetent design and filled with the ejecta of tragic ignorance. Ask your buddy if he'd turn down an immaculate pair of Marantz 9s.

We will not do an incompetent design.

Let's see what a proper design will entail. Worst case, we want to drive a 500pF load while retaining the bandwidth that the input transformer allowed us. The source impedance and the cable's shunt capacitance form a first-order low-pass filter with a 3dB down frequency of f₃ = 1/(6.28*Z_out*C). Rearranging terms to solve for Z_out, we see that for a 90kHz bandwidth, we need a source Z of about 1.8Kohm. That's pretty doable. But we also have to consider how much current will be needed to drive the load to the maximum voltage. If we assume a 2 volt input sensitivity (that's RMS; peak will be about 2.8V) for our power amp, the signal current needed to drive the 1000pF load capacitance to the full voltage while maintaining the 90kHz bandwidth is about i = 1.6mA. Using a rule of thumb, we arbitrarily dictate that the standing cathode follower current ought to be at least several times higher, just to have margin and to minimize distortion. So let's say we need 10-15mA running through the cathode follower at minimum.

We're now in a position to select a tube. There are a lot of candidates which are happy at the desired current, two very common ones being the 6SN7 and the 6DJ8/ECC88. These also have the considerable virtue of being cheap and easy to find. Recalling that the output impedance of a cathode follower is about 1/g_m, we can check the suitability. The 6SN7 has a transconductance of 2.5-3 mA/V, which translates to an output impedance of 300-400 ohm. Add a cathode stopper (more about that later) and we're up to roughly 1K, well within what we need. Similarly, a 6DJ8/ECC88 at 10mA will have a transconductance about three times higher, resulting in a base source impedance of roughly 100-150 ohm. So from this standpoint, either will work. The 6SN7 is a lower distortion tube, but with the inherent feedback of a cathode follower, both tubes are likely to have exceptionally low distortion at these signal levels.

The ECC88 is a winner in this application because of its plate voltage requirements: less than half what is needed for the 6SN7. So low, in fact, that the B+ supply can be made with a standard isolation transformer, and still have enough headroom for active regulation. As a bonus, the higher transconductance translates into a lower noise floor.

A constant current source as a cathode load will help make biasing easier. It will also ease some of the voltage requirements as we will see in the detailed design description. I have been leery of their use in the past, based mostly on unsatisfactory experiences with FET current sources that were fashionable back in the days of Jimmy Carter. Several writers convinced me to use discrete bipolar CCS and I've been delighted with the results. They're cheap, perform well, and are quite reliable, in all ways a vast improvement on those awful two-legged devils of my youth. A pentode also can make a fine current source, but it needs lots of voltage, more chassis room, more heater supply current, higher cost, higher parts count, lower reliability, separate heater supplies... but it's a perfectly valid choice. I just didn't choose it. Either way, it will be made adjustable: adjustability gives the tweaker loads and loads of fun opportunity and flexibility to play with operating points and alternative tube choices.

I think we're ready to float a preliminary design out there and start assigning component values. The basic topology looks like this:

Hello guys, i need any information about woofers in the old ''WHITE VAN" speakers Omni Audio SE 12. 3. Maybe someone make measurement??

Asking $80 for all of these sold together as one lot, which is <50% of retail:

TKD 2CP2511 100K monos (used once)

TKD 2CP601 100K (used once)

Two Alps blue stereo, one is 50K, one is 100K (used once)

Update:

• More comprehensive measurements available here: Post #30
• THD+N vs Frequency for inverting vs non-inverting configuration can be found here: Post #36
• THD+N vs Output Power for inverting vs non-inverting configuration can be found here: Post #38
• THD+N with star grounding is available here: Post #40

First off, let me say that I do not intend to cause a shouting match between the PCB lovers and the Point-to-Point (P2P) enthusiasts. I just noticed something interesting while prototyping so I decided to investigate and document it...

The story is this: I'm designing an amp based on the LM3886. My intent is to improve dramatically on the performance of the original LM3886. The final amp will reside on a PCB, but I figured I would build a prototype first. That way I could get the bugs ironed out before committing big bucks to a PCB fab run. I built the prototype using P2P wiring as that's the quickest and I expected it to provide as good performance as a PCB. Indeed the performance at 1 kHz was reasonably close to the data sheet figures.

However, I was rather surprised when I measured the THD versus frequency. At 20 kHz the THD was an order of magnitude worse than the data sheet would indicate. This was rather surprising to me as the P2P circuit is pretty tight. The feedback network is right on the IC pins. As is the decoupling caps. The distance from the 1000 uF supply caps to the IC is not more than 40~50 mm. The circuit was fed from a quality lab supply.

I decided to spin a quick prototype PCB. On the PCB is the exact same circuit as I used for the P2P setup. All the components came from the same batches of parts. Yet, on the PCB, I am able to reproduce the data sheet performance. The THD is much improved. The ground plane on the PCB is connected to the power ground. Signal ground runs as a separate trace and joins the power ground at the center between the two 1000 uF supply caps.

As seen from the transient responses, neither circuit exhibits tendencies towards instability. The transient response is nice and well controlled for both the PCB and the P2P circuit.

The schematic attached shows the main parts of the circuit. In addition, there are two 1000 uF electrolytic caps bypassed by two 47 nF ceramic caps where the power enters the board.

I suspect the return paths for the various electric fields in the circuit are better controlled in the PCB-based circuit. I am guessing that is the explanation for the difference.

The abrupt change in THD around 1.5 W is caused by range switching in the HP 8903A distortion analyzer. The uptick in THD above 6 W for the 20 Hz trace is caused by brownout of the power supply.

The supply voltage was +/-28 V.

Equipment: HP 8903A distortion analyzer. Tektronix 2465B 400 MHz oscilloscope (using 20 MHz bandwidth setting to avoid interference from a nearby FM transmitter). HP 6228B power supply.

Just thought I'd share...

~Tom

I received a request for a build thread with TDA7294 point to point.
Please feel free to add comments, questions and suggestions.
DMOS = Lateral Fet = Power MosFET, and are inside these chips.

Here it is step by step, with photos. . .

The above photo shows TDA7294/5/6 pinout.


The above photo shows the schematic. It is especially suited to under-volting applications.
Here is a new full power schematic that doesn't require a preamp <click link
Note that TDA7294S and TDA7293 have advanced features at pins 5, 11, and 12. We shouldn't ground those. I've no idea if my TDA7294 chip has those features, so I'm going to remove those pins by wiggling them; with the benefit of more room for soldering.


Now, the pins marked N.C. (5, 11, 12) are definitely not connected, and 12 pins is easier than 15. At this time, I'd like to mention that if you favor parts swapping for fine tuning and quality control, then you may rather use PCB boards for the first build. Here are some compatible kit boards. <--link


The above photo shows: Bending the V+ pins (8, 15) almost to the chip face, bending the V- pins (7, 13) up a bit and then bending the ground pins (1, 4) to midway. This is for rails horizontally across the chip. I've also bent the small signal, down away from the power pins, and spread them very slightly.


The above photo shows V+ and V- rails with ground at center. I used Gel Flux for assuring good connections done easier.
Those are low-ESR 220u caps. Optionally, you can use parallel pairs of ordinary 100u caps (makes low loss 200u).


The above photo shows nanofared caps added to V+ and V- for HF bypass duties.
Also shown is 2u polyester at rail to rail (one cap from V+ to V-) for quality control.


From boostrap pin (6), the 47u boostrap capacitor goes to output pin (14).
The above photo also shows 60k feedback resistor from output pin (14) to inverting input pin (2). That feedback resistor pictured is a parallel pair of 120k, for quality control, and fortunately doubly sturdy with minimized inductance.
Feel free to sleeve anything with heat shrink tubing if you want to (even in that case, please do have some air space in-between).
EASIER BUILD?: If you're going to do any fine tuning or want an easier build, then consider allowing the pins to hang down below the heatsink and put the feedback resistor on back so that you can change values easily and there is much more room to build small signal area. Tone changes by both operating voltage and gain setting, and you will want to fine tune that to your own preferences.
LACKING A PREAMP?: Click Here for alternate higher gain schematic.


The above photo shows:
Standby (9) to V+ via 22k
Standby (9) to ground via 10u.
Mute (10) to V+ via 10k


The above photo (bottom side) shows:
220u NFB cap at ground pin (1)
2.7k (carbon) feedback-shunt resistor from NFB cap to to inverting input pin (2)
10k (metal film) input load from ground rail to non-inverting input pin (3)
Notes:
The 220u NFB cap is for authentic chip, but if cull/fake use 100u or smaller NFB cap.
Cable for input and cable for speaker can be added before attaching chip to heatsink.
RF filtering of speaker output RC (6.8R and nanofareds cap) can be added at speaker jack.
RF filtering of input can be added with 1M||220p from + to - at the small signal input cable
Suggested input cap size is 1u (or smaller) and may be at the output of volume pot.
If volume pot is omitted, the input cap size of 1u (or smaller) can be at the RCA jack.


And there it is, TDA729X point to point.

Voltage and current note:
Authentic chips are capable of the specs listed in their datasheets; however, please check ST's Authorized Reseller list to see if you bought or can buy from a reliable source. If you have any reason to suspect that your chip may be either fake or cull or misbehave, please use 4400u (or more) worth of "output cap" (capacitance in series to speaker blocks DC accidents) as a speaker protector, and use 8 ohm speakers. A parallel pair of 2200u creates a low loss 4400u cap suitable for output cap (parallel pair of 3300u creates a low loss 6600u output cap for larger speakers); however, it may be less expensive to purchase authentic chips. Of course mains fuse and speaker jack fuses are good too. Authentic ST chips (from authorized reseller) can drive both 8 ohm and 4 ohm speakers at high power.

First startup:
Use "output cap" to protect your test speaker and use safety bulb test to protect amplifier.

Transformer for TDA729x chips:
TDA7293, 24+24vac toroid or 48vct (24,0,24vac) 5a
TDA7294, 22+22vac toroid or 44vct (22,0,22vac) 5a
TDA7295, 20+20vac toroid or 40vct (20,0,20vac) 4a
TDA7296, 18+18vac toroid or 36vct (18,0,18vac) 3a
Cull/Fake, 15+15vac toroid or 30vct (15,0,15vac) 2a

Power supply:

Miro's DAC is a brilliant implementation of the AD1862 non-oversampling R-2R DAC chip, which not only sounds great but lends itself to all sorts of experimentation.

You can read more about the DAC here.

The Auction

I'm auctioning two completed DAC boards to raise funds for DIYaudio's preferred charities: Donations to two great charities – diyAudio Store .

Both causes are great and you're free to choose, but perhaps consider the increase in suicide/suicide attempts during COVID.

Because you'll pay by showing me the receipt from your donation, 100.0% of funds will go to the charity.

I'll mail the DACs to the winners anywhere in the world* at my cost. Insurance and any import duties are on you.
* Where served by the US and your country's postal service.

The DACs



Both DACs were built and tested by me, using Kester SN63 solder and good components including brand 2 new AD1862N from Rochester Electronics. Panasonic FR, Nichicon, Wima MKP caps on the digital side and Wima MKS on the audio side. I/V resistors are 1.5k ohm General Resistance (Rhopoint) 8G16D and are socketed if you decide you want something even more esoteric.

They both sound good but each is packaged a little differently.

The Experimenter DAC has sockets for DIP op amps and the audio-side electrolytic caps, allowing you to test and tune. Panasonic FR caps and 4898, 4627 and 828 op amps are included to get you started.

The Listener DAC has LM6171 SOIC op amps and Elma Silmic II audio-side electrolytics soldered to the board and is ready to make your ears happy.

Remember that the auction is for the DAC boards only, before you can listen you'll need to provide an i2s converter for whatever data source you're using and good quality +/-5VDC and +/-12VDC power supplies.

The Rules:

You don't have to be a diyaudio member to bid, but maybe you should join, eh?

The Auction is what we here in Virginia farm country call "by the each." Bid a price per board, and the winning bidder can buy one or both at the winning bid price (x2 if taking both boards). If the winner only takes one board, I give the next-highest bidder a chance to buy the other board at their bid price, going down the list if that bidder declines.

Bidding is easy - reply to this thread with your bid, keep watching to see if you get outbid, then bid higher.

Bidding is open now and ends at 1600 UTC/GMT on Saturday 26 June 2021. The official countdown timer is here

The winning bidder must donate within 24 hours, else I'll go to the next bidder.

Good luck and please be generous!

I purchased this about two weeks ago from a member here. Three days later my car stalled out at work and I had to get repairs done to the tune of $470, which dipped in to my ‘fun’ money and thus, I am selling the soundcard interface to recoup some of my funds.

The seller had lined the case in copper foil and also used the current limit bulbs that are supposed to reduce noise.

I’m asking $225 shipped, CONUS (or $210+shipping internationally).

-- SOLD --

I’ll attach pictures later when I get back to my phone and can upload them.

My 115V Hafler p3000 has a transformer wired as shown on the left.
Before I blow everything up, would someone please confirm that the rewiring for 230V as shown on the right is OK?
Thnks.

A long shot, but somebody may have a spare singleton sitting around.
I have one I was playing around with and now I want to use that value in a project for stereo speakers.
Of course I could buy a single cored coil of the same value but then OCD might kick in and I might hear artifacts that are not there. Also willing to sell this one and buy a matched pair.
Negotiable around the old retail price plus postage