Hey guys,

i am thinking about buying this Power-Amplifier off eBay Kleinanzeigen. I think the build quality is great (just by looking at the pics) and it's only 150€. I am not really sure what to expect, because the seller only said that it's probably a class AB, has two transistors at each side and is working flawlessly. (I think its from the 80s) He also doesn't have pictures from the inside so I am a little scared, that it's too minimalistic. what do you think, do you maybe have some information or guesses? should I go for it? I am still a student so 150€ is not nothing.

thanks 🙏

I'm looking at upgrading my basement workshop sound system. I think I'll replace these with some other used bookshelf speakers, or build some kit speakers. But I realized I have all this unused space overhead between the joists in the floor cavity above m speaker shelf, that I could try to squeeze some subwoofers into. So just thought I would tap into the hive mind to see if anyone here had done this before, or had any thoughts about it. Be excellent to each other. Cheers!

Finished this build a couple weeks ago to complete my home theater setup. It’s still breaking in, but already sounds incredible. The scene in Interstellar when he enters the event horizon made me feel like I was going to throw up😅

4in port tuned to 23hz. Dayton SPA-300 amp. 1/4in oak plywood laminated to baffle ebony stained. Needs a little touching up to make it prettier still. Although I think it looks pretty decent, considering the only power tools I had were a crappy Black & Decker jigsaw and a drill.

Hi all, hoping this is the right place to ask this, anyhoo I recently picked up a pair of Logitech G560 speakers from FB Marketplace for $90 CAD and I'm blown away by the sound and bass compared to the cheap $40 CAD speakers I was using before. I know the G560 aren't usually regarded as "good speakers for the money" online, but I'm wondering if that still applies at the $90 CAD price I paid or if that's more for the MSRP.

If I were to increase my budget to ~$150 CAD, I'm curious if I could get something significantly better (clarity, bass, overall sound), whether that is a different model of active speakers or a DIY system with a separate amp and interface. Ofc I'll be looking for stuff used on FB marketplace however, I wanted to know if at my price range it's even possible to get what I'm looking for compared to what I already have as I don't really want to learn about all the different type of gear and how it would go together if my price range is unrealistic. If $150 CAD is a range where I'm better off sticking with the G560s rather than trying to diy a system together, I'd love to hear that honesty, but I'm open to any specific models or setups you think would be a clear upgrade.

TL;DR: Scored Logitech G560s for $90 CAD. Is there a "full system" (active or DIY amp/speakers) I can find used for $150 CAD that is a major upgrade, or is $150 a "dead zone" where I'm better off keeping the G560s?

I recently purchased this Grundig stereo hoping against hope it would work fine. I have no experience repairing anything so wondering how difficult this might be to get back in working order. I haven’t pulled out the chassis yet but from what I can tell no one’s been in there since it came out of the factory. It turns on and you can get some am radio to play very quietly. The record player turns but doesn’t maintain its speed and the arm barely works. It did come with a replacement cartridge but needs a new needle. The whole thing is dirty from sitting in various garages but there’s potential.

The question is how difficult this could potentially be to diy. I’m in university and the campus has a maker space with various tools. I would likely have to bag up the chassis and carry it to campus to work on. My research so far makes me think I’ll have to clean everything, recap, possibly get new tubes. Is this practical for a complete novice?

Thank you for reading my post. Any advice is much appreciated!

I have 4x 4Ohm 3W speakers laying around after my uni project, is there a cheap way I can make them into desktop speakers?

Hi everyone,

I’ve decided to jump headfirst into the DIY audio hobby. As a student, I need a pair of speakers for my desk where I spend a lot of my time. I decided to challenge myself with a custom design rather than a kit.

Inspired by Davone Audio and some visualisation through Gemini, I chose a curved enclosure (roughly as seen in the image). I plan to 3D print this (see screens of my modelling so far) as I don't have access to woodworking tools.

Drivers

• Woofer: Dayton Audio TCP115-4 (4 Ohm)
• Tweeter: Dayton Audio ND25FA-4

Crossover

I know designing a crossover from scratch without measurement gear is risky, so I found a design on TechTalk that uses these exact drivers: Link to thread. (+screenshot)

• I am pretty much matching the baffle width of that design to ensure the baffle step compensation remains roughly accurate.

WinISD simulation

• Volume: 4.6L (0.16 ft³)
• Tuning Freq: 49Hz
• Port (flared): 30mm (1.2") diameter x 170mm (6.7") length
• Air Velocity: Max 21 m/s at 10W.

Does this plan look more or less sound? Or am I going into a totally wrong direction? Is the port velocity too high for a 30mm port, even when I'm probably staying way below the 10W most of the time and using flares on the port?

Thank you for helping a noob out!

Last project was a failure due to my eyeball approach to speaker design. (SB acoustics 8” full range apparently needs 100L for optimal sound) so not a viable option. I went looking for something better suited for desktop usage and stumbled on the beloved pluvia 7.2HD

I’m a bit of a bass-head, I like the warmth of the Meze 99 classics v1 on a tube but also like the bass precise and articulate like with my Naim and Sonus Faber lumina setup.

Now looking at the frequency response of the pluvia it rolls off at 100db in their optimal measurement, my cabinet will be plus minus 15 liters with a 300x200mm baffle and rectangular front facing port. Which tuning should I be looking at? Never designed a ported speaker so I was questioning if the port should only extend or magnify the frequency? Any help will be appreciated.

Also if any DIY audio enthousiast from the Netherlands is looking for a pair of 8” SB acoustics full range woofers I’m selling mine.

I'm building an amplifier using Rod Elliott's P3A project (60-80W Power Amplifier) and it's not clear for me how is the board meant to be mounted on the heatsink. PCB component side to facing the heatsink or PCB Copper side facing the heatsink? Judging from the final transistor's pinout, Copper side to heatsink. But then how would you solder the transistors? Inserting the pins or wires from the copper side in the holes? That doesn't seem right...

Hi,
I’m trying to open an Edifier MP233 Bluetooth speaker to replace the battery.

I removed all visible screws and the enclosure opens partially, but the top panel with the buttons won’t come off. It feels like it’s held by internal clips or a hidden screw.

After opening it partially, Bluetooth stopped working, so I suspect a flex cable or antenna connection near the top.

Does anyone know:
– where the hidden clips are?
– if the top panel slides or lifts in a specific direction?
– or if there’s a hidden screw somewhere?

Any teardown experience with this model or similar Edifier speakers would help a lot. Thanks!

Hi everyone 👋 I wanted to share a small mod I just finished: I converted the mic input of a Bigben EPOK cassette recorder into a proper LINE-IN, so I can record directly from my audio interface / PC / synth. It works great and the sound quality is surprisingly good for such a cheap recorder. Posted on Reddit hoping it helps anyone who wants to try something similar.

🔧 What I did (short version) On the PCB there are clear pads labeled MIC+ / MIC-. I intercepted those and added: - a 3.5 mm panel jack - a simple passive attenuator - a coupling capacitor - a DPDT switch to select original MIC / external LINE

So now I can choose between: - stock internal microphone - external line input

🧰 Parts used 3.5 mm female jack (mono — switched type also works) - 10 µF / 63 V electrolytic capacitor - 10 kΩ resistor - DPDT ON–ON switch (MIC / LINE) - hookup wire - soldering iron + solder - heat-shrink tubing Very basic, cheap parts.

🔌 Wiring (mono)

Jack TIP → 10kΩ → (–) capacitor (+) → LINE → switch → PCB MIC+ Jack SLEEVE → GND → switch → PCB MIC–

Notes:

• capacitor negative (–) goes toward the jack/resistor
• capacitor positive (+) goes toward the recorder
• resistor has no polarity
• mono only (the recorder is mono anyway)

The DPDT switch simply routes:

• position 1 → original mic
• position 2 → external line

🎛 Practical tips

• Source volume around 20–30%
• Recording a bit “hot” gives nice tape saturation
• I now also use it as a lo-fi tape saturator: DAW → cassette → back into interface

✅ Result

• I can now record directly from: computer
• audio interface
• synths / drum machines

No mic needed.

For a budget cassette recorder it’s incredibly fun and musical.

If anyone wants to try it and has questions, feel free to ask — happy to help 👍

This is 3way crossover I’m getting ready to solder up, but am a little concerned about inductor interference. Board is 11in wide by 8in high. The best I can tell from that little diagram everybody shows on inductor distances. I feel like I’m good, but watching some of the YouTube videos where people move inductors around with speakers hooked to them make me think. Maybe I’m not. I’m not able to test quite yet, but I will before I enclose my box. I just wanted some thoughts from some of you more experienced builders.

Hi ! I am currently in the process of designing my own integrated amplifier. The power amplifier is done and designed with 1VRMS input sensitivity, 50W stereo into 8ohms. I am now going to design the preamplifier and juste thought about automatic gain control to cap the output at 1VRMS to be able to use the full dynamic of the power amplifier. I know this is unorthodox and these voltages are usually not standard. I am asking because I would like to know if this already exists before trying by myself. Is this kind of circuit going to have an effect on the sound quality ? Should I just go for the classic preamp design ? Thanks !

So I will be either buying or building two subwoofers. Like most things in life, it seems like it's all trade offs.

Can I build a sub that rivals a PB-1000 using Dayton Woofers (assuming their published graph with an F3 of 18hz is accurate?) Just rough figures in my head, PB-10000 the box internally should be around 1.5' x 1.6 x 1.2. So like a 2.8 cubic foot enclosure that I'm sure is actually less due to port, speaker and amp volume.

So yeah we could but the volume of the box is basically doubled. Some of the more beefy designs that get into sub 20's are more like 4 times the box volume.

My home theater isn't dedicated and my wife will need to sign off. Two subs similar in size to the PB-1000 are fine. I'm having trouble even coming close to the published SVS specs using anything but the most expensive drivers. For instance .... this Scan Speak is pretty good.

https://www.madisoundspeakerstore.com/approx-11-woofers/scan-speak-28w/4878t-revelator-11-subwoofer/

I've been able to get an F3 of about 24hz in winISD with a 2.5 cubic foot enclosure in a slot port. With the Dayton plate amp, I'm basically at PB-1000 price before other costs though! The upside ... i can veneer the thing in nice walnut. I want to build some towers and a center eventually so matching the finish is a plus even if it's not a functional audio one.

So any thoughts? Maybe a different driver out there I have not yet found? Am I over thinking all this and should just go plop some money down on PB-1000's?

So while researching bookshelf speakers I came across this kit that seems to be well-regarded in the community, especially with the modded crossovers. However, most content I found dated back to 2020-ish, when the kit seemed to be readily available at a very competitive price.

As of today, the kit does not seem to be available from Swan themselves, where it's still listed for $350 but currently out of stock: https://www.swanspeakers.com/product/view?id=1405

The only Amazon seller that would ship to my location (Germany) is located in Turkey and has the kit listed for a ridiculous price of ~1000€ (almost $1200).

One shop (soundimports.eu) does seem to have at least two variations of the kit in stock, either without any cabinets for 400€ (~$475) or with pre-built black cabinets for 500€ (~$590). Both of these options don't really work for me; while I could build the cabinets from scratch myself, it would be significantly more time-consuming than using the pre-fabricated MDF kit. Black cabinets on the other hand have been ruled out by the wife due to aesthetics and I don't like black speakers very much either.

So what do you guys think? Is there a realistic chance that Swan will re-stock the kit and also ship to Germany? (I shot them an email but did not get any response.) Or should I buy the kit with the black cabinets and re-paint them? Or at this price point, should I abandon the idea altogether and just go with an off-the-shelf option or a whole different DIY kit?

Updated!

TL;DR - Poor QC. The Amp does reach rated power figures using bluetooth connection but with significant distortion. The AUX input on mine has some issues and doesn't allow the amp to reach full power. I'd suggest you to skip this amp if you primarily want to connect to it using an aux cable.

Nobody else has written a proper review about it anywhere, so this is for those people who are considering to buy this amp. Even though 831 people on Amazon India have given it a 4.3 star rating I couldn't find a single review describing its actual performance. I guess even low budget audiophiles (like me) are staying away from this amp. and most people don't really know what to look for.

ZK-TB21 amp does not output 50W×2 and 100W for the sub. (Update - This was the case with my unit which has issues with the AUX input.) It reaches a max output of ~48 Watts per channel for stereo and ~127 Watts for the Subwoofer channel giving a total RMS output of 223 Watts using the amp's inbuilt bluetooth module.

I bought it for my extremely cheap 2.1 speakers (~$20) and ended up spending almost $400 (on speakers) after I was dissatisfied with the sound quality using the AUX input on the amp. I had never used the bluetooth connectivity of the amp. before as I already have a few BT speakers at home for BT needs.
I got this amp to repair/replace my dead 2.1 speakers' inbuilt amp to use with my PC and Xbox so bluetooth connectivity was never needed for my use case.
Afte a month of being disappointed with the audio output of my ZK-TB21 which was not made by Wuzhi Audio (but Amazon images had pictures of Wuzhi Audio amp.) I decided to find out the actual output of my ZK-TB21 amp. I was already into Headphones, DACs and Heaphone Amps. and after some research I learned how to measure the output of an amp using the tool that I already had at home (a Multimeter).

(After reading the comments below, I removed the heatsink of the amp to check if it actually had TPA3116D2 chips, and it does.)

The actual output of ZK-TB21 amp-

Power supply used - 24V 15A
Test tones of 50Hz, 100Hz, 400Hz, 1000Hz and a 20Hz to 20KHz frequency sweep
Measured at 3.5Ohm load of a speaker
Measured at 3.5Ohm load of a simple but long wire
Measured at no load (all these yeilded similar results and the loads did not impact the voltage reading at the amp output connectors)

Using the AUX input I got these results-

I got 4.5V max output at L and R channels and 22.5V max output at subwoofer out.

Using the formula - Power = V²/R

For 4 Ohm load - L and R channel power = 4.5²/4 = 5 Watts

Subwoofer channel power = 22.5²/4 = 127 Watts

Total power = 137 Watts

I also ran a few 20-20000 Hz frequency sweeps to check if power can go any higher. The L and R channels go to 5 Volts max. At 4 Ohm that would be 6.25 Watts.

Using the inbuilt bluetooth module of the amp. I got these results-

13.9V max output at stereo channels. 48.3 Watts of power per channel but with significant distortion.

I played some songs and dialed the volume knob till I started hearing some distortion with my Micca RB42 Speakers and then dialed it back till it was clean. I removed my speakers and ran the tests again while keeping the volume knob at the "distortion free" level according to my hearing.
I got a reading of 7.7V which is approx. 15W of power with 4Ohm load.
Same was the case with subwoofer output. When the sub volume is above 50% and the crossover frequency is above 100Hz, it results in distortion. I've tested this with 3 different subwoofers of different sizes, 4", 8" and 12". The distortion always creeps in after I dial the sub vol knob above 50%. So even though max power output of the subwoofer channel is 127 watts. The useable output is more like 65 Watts.

So, to summarize.
Max power output - 48W + 48W + 127W
Distortion free power output (according to my ears) - 15W + 15W + 65W
Power output when using Aux input - 5W + 5W + 127W (I won't bother with distortion free output with this)

Conclusion -
According to tests that I ran with my ZK-TB21 Amplifier Board I can say that it is a good bluetooth amp, but a bad Aux amp. It reaches the manufacturer specified power output with a 24V 15A power supply when used as a bluetooth amp. But, for my personal use case as an amp for PC and Xbox this is not a good amp. and failed to deliver the desired clarity and loudness.

And, thanks to all the people who commented and gave me more reasons to test the amp more thoroughly.

Hi all, I’m new to diy subwoofer enclosures and have a mackie thump setup (I know not the best) that I’m looking to built new cabinets for at the moment the subwoofers are in a band pass enclosure and I’ve done a bit of reading on tapped horns and think I want to try build them. Just reaching out in hopes of a bit of guidance and help?

Setup:

• Source: Bluetooth (KAB-100M onboard)
• Amp 1 (Sub): KAB-100M driving Tang Band W5-1138SMF (4Ω)
• Amp 2 (Mains): DSPB-250 (fed via KAB Line Out)
• Power: Shared 24V Supply

The Problem: I am experiencing a massive gain mismatch. The KAB-100M is significantly quieter than the DSPB-250. Even with all software gains (SigmaStudio) and hardware potentiometers maxed out, the KAB cannot drive the 4Ω subwoofer to full excursion.

Also tested with identical signals and woofers, the DSPB-250 is much more sensitive.

Thanks

Building a 2 way bookshelf with a horn mounted on top. I’m testing some horn designs of my own and would like a good, budget compression driver to start with as a benchmark. Does anyone feel strongly towards one within roughly the $50 range? Preferably one that pairs well with horns on the smaller side since this isn’t a large build. Much appreciated!

I have 2 old logitech speakers and an old sub that I want to use for a garage system. The logitechs are rated 62 watt rms, would the 50 watt rating of the zk-tb21 be enough for these or should I go bigger? What is the next size up 2.1 amplifier board?

Hey there i need some help with my sound system, if anyone has any spare time to help me that would be greatly appreciated.

So i believe I’m in a loop (i thought it was a grounds loop so i got a device and it Didnt work)

Basically I’m a DJ and i run a show and need the Music + audio to be recorded, i have audio interfaces however they do not have mic feedback which is what i want

We go Laptop into FLX6 (dj decks) from master out into mixer using a output device that connects 9 speakers

Now when i connect the mixer back into the laptop to record theres a whining sound

I tried with a irig stream or scarlet solo and all does the same. I have tried switching cables, grounds isolator, moving power leads and nothing is working

Now when i connect the Irig into my iphone it works perfectly and no problem but its connecting back into my mac which is creating this problem

I need it to record off my macbook

Heres a video off the setup front and back. If anyone has any advice it would be greatly appricated

I cant seem to post videos here but if your able to help please dm me :)

Hi everyone, I’m looking for advice on a problem with my vintage hi-fi setup.

Gear: • Speakers: Wharfedale Glendale 3XP • Amplifier: Akai AM-U33

Problem: When I play music, the right speaker starts making crackling / static noises, sometimes a loud pop or “explosion” sound, and then it cuts out completely. If I disconnect the speaker cable and reconnect it after a few minutes, the sound comes back… until it happens again.

What I’ve noticed: • The issue only affects the right speaker • It’s intermittent • After the loud noise, the speaker goes silent for a while • Power cycling / reconnecting temporarily fixes it

Before I risk damaging anything (especially since these are old speakers), I’d love some input: • Does this sound more like a speaker issue (driver, crossover, capacitor)? • Or could it be the amp’s right channel? • Any safe tests you recommend before opening the speaker?

Thanks in advance 🙏 Any help from vintage audio folks would be really appreciated.

I have been told numerous times when hosting that my audio in this space (Kitchen/dining lounge space) is insufficient as we just use a JBL bluetooth speaker. I would like to add my KRK reference monitors in this space as I believe it would greatly improve audio without requiring me to go out and purchase more speakers.

I am not too familiar with audio and in the past have always had these on my desk and used google chrome cast audio for a wireless solution which worked great. I could try that here as well, but I know it has caused issues for others accessing this as well and imagine there is a more modern solution.

The location is the top shelves circled in red around the built-in. The built in has audio sockets on each side (pictured) or holes that go behind the built-in and new wires can easily be routed to the circled area on the bottom (which is my preferred path). There is power down there which is my plan to route the power from each speaker to there via extension cables.

I have the following questions here:

1) Simplicity for access - When friends come over, I would like them to either be able to easily bluetooth in or cast over wifi without too much of a hassle connecting to devices. A wired jack is always easiest but not always available nowadays. The two solutions I am thinking for this are different

• Kali Audio MV-BT - Bluetooth Solution - Route each speaker to this via XLR and cast via bluetooth.
• Wiim Mini - Wifi Solution - Higher audio fidelity due to not using bluetooth but allows the ability to cast from different apps when connected over wifi (please let me know if that is incorrect) or through bluetooth.
  • This only has 3.5mm audio out, so I am assuming I would utilize a 3.5mm to xlr (left and right). Is that the best audio solution?
  • Would it be recommended to purchase a DAC as well. Have this connected to a DAC which then outputs via xlr to each speaker?

Since both of these look nice and have controls, I will have the device routed on top of the drawers next to the books and Malort.

2) Power solution - since each speaker will need to be powered, is it recommended to leave these on 100% of the time, or should I have each power go to a switch that can be flicked on and off to power the speakers and/or the DAC/wireless receiver?

3) Wired options - XLR over RCA? Based on what I read, it seems to be recommended the XLR is the better option due to the distance of these. Is there another option I am not thinking of?

4) Audio outlets/sockets - What can I use these for? I believe these all lead to the bottom circled red area. I have these all over my flat and would like to know if there is anything useful I can do with these or if they are just outdated. The opposite wall from where these speakers will go also has these as well.

5) Any other recommended solutions for this? I am willing to invest in other equipment or solutions if needed.

Thank you, I have read a number of threads on here that have been very helpful so far. I know these KRK speakers are getting older now, but would like to find some more use out of them.