Hi everyone,

My Outline LF 800 stereo power amplifier is currently in a professional repair shop here in Hungary with a blown output stage on one channel.

The tech is brilliant (builds amps from scratch), but we desperately need the official electronic schematics / service manual to verify the exact factory bias values and check the proprietary SOA CTRL (protection) circuitry.

The document is available on HiFi Engine (uploaded by user Frank57), but registrations are closed and we don't have an active account to download it.

Could anyone with a HiFi Engine account please download the Outline LF 800 schematics and share it via a DM or temporary link? It would mean the world to me and help save this legendary Italian beast.

Thank you so much in advance!

I’m running a somewhat unconventional home-theater setup: Onkyo txnr6050 - 130a smart charge - kicker46CXA1200.1T - skar dual 12”

Everything is connected and functioning, but I’m experiencing a constant humming/crackling noise that I haven’t been able to eliminate. Which I’m assuming is a ground loop.

I’m hoping someone experienced with audio electronics, RCA grounding, or car amplifiers used in home systems can help me narrow down the cause.

Equipment
Receiver: Onkyo TX-NR6050
Power supply: Taramps Smart Charger 100A/130A, operating at 14.4V DC without a battery
Amplifier: Kicker 46CXA1200.1T (1,200W RMS, 1Ω capable)
Subwoofers: Skar Audio SDR dual 12” D4 loaded enclosure, factory wired to 1Ω
Additional powered subwoofer: Klipsch SPL-120
DC wiring: 4-AWG OFC, 150A DC breaker, 100A ANL fuse
Remote turn-on: Fused 18-AWG wire from the positive DC supply to Kicker REM

The problem
With the Kicker powered on and the RCA cables disconnected, the Skar subs are completely silent.
As soon as I connect an RCA cable from the Onkyo’s subwoofer pre-out to the Kicker, I get a constant low-frequency hum accompanied by irregular crackling/pulsating sounds.

Interestingly, when I press Play on the Onkyo’s audio source, the noise becomes noticeably louder, even during the silent portion at the beginning of a track.

Another unusual observation: physically touching the Onkyo receiver makes the humming noticeably quieter. I’m wondering if this suggests a grounding, shielding, or floating-reference issue.

Troubleshooting I’ve performed
Tested three different RCA cables. All produce the noise when connected to the Kicker, although some cause more crackling than others.

Tested those same RCA cables with my Klipsch SPL-120. They work normally without the same humming/crackling issue.

Completely disconnected the RCA inputs from the Kicker. The amplifier remains powered, and the Skar subs become silent.

Connected only one RCA cable from the Onkyo to the Kicker. The humming was still present and loud.

Inspected the Onkyo’s subwoofer RCA output jacks and discovered what appeared to be a small broken metal sleeve lodged inside one of them. It made inserting an RCA plug unusually difficult.

Removed the loose metal fragment. The jack now appears similar to the others, but the humming/crackling remains unchanged, including when using the other apparently undamaged output.

Noticed that touching the Onkyo’s chassis significantly reduces the noise.

I’ve attached pictures of the RCA sockets and the metal fragment I removed.

What I’m trying to determine
Could this be an RCA ground loop between the Onkyo and the externally powered Kicker?
Could the damaged RCA socket have affected the receiver’s signal-ground connection?
Did I damage the RCA ports by extracting that sleeve?

What I’m thinking is, it’s most likely a problem with the onkyo internal circuit but it works perfectly fine with the SPL120.

Alternatively, could the Taramps switching power supply introduce interference that becomes audible whenever an RCA shield connects the two systems?
I’m also wondering whether there could be a fault in the Kicker’s RCA input grounding circuitry but that seems unlikely, it’s a brand new amp.

What would be the best diagnostic procedure to distinguish between an Onkyo output issue, an amplifier input fault, and a ground loop?

Any suggestions would be appreciated.

What’s up gang! I am a lover of audio gear, a design engineer by trade and a tinkerer at heart. I’ve re-capped and biased guitar amplifier’s, built guitar pedals and done very basic troubleshooting/cleaning and re-capping on some of my audio gear. I’m wanting to dive deeper into this hobby, and I was wondering if some of you could provide your insight on where to invest my time learning. Any good books, YouTube channels/videos, tools, information etc etc. I have a Sony STR-7045 that I was planning on re-capping (having some issues with the left channel being weak with less low end), but I’m curious about fully rebuilding it since it is my pride and joy. Would love to hear what you all think!

Like a lot of people here, my left P40i earbud became noticeably quieter than the right one after a couple of drops (even after cleaning the mesh).

The usual workaround is shifting the L/R audio balance in Android/iOS accessibility settings, but that has two annoying downsides:

1. As soon as you connect the earbuds to a laptop, TV, or another device, the imbalance is back.

2. When you connect your phone to a car stereo or another pair of headphones, the phone's balance is still skewed.

While looking into how the Soundcore protocol works (thanks to the OpenSCQ30 project), I realized that Soundcore earbuds with **HearID** (`P40i`, `Liberty 4 / 4 NC / 4 Pro / 5`, `Space A40`, `Life P3`, `Liberty 3 Pro`, `P30i`, etc.) actually have **two independent 8-band EQ + DRC registers (Left and Right)** stored in the earbuds' onboard non-volatile flash memory (`Command 0x03 0x87` over Bluetooth RFCOMM).

Neither the official Soundcore app nor third-party apps expose a simple "Hardware L/R Balance" slider that keeps your custom EQ curve intact while offsetting Left vs. Right gain, so I wrote a zero-dependency Python CLI/TUI tool to do it.

### What it does:

- Automatically detects your connected Soundcore earbuds and backs up your current factory/custom EQ state to a JSON file.

- Lets you use the Left/Right arrow keys in the terminal while music is playing to shift the L/R balance in `0.5 dB` steps in real time until the vocals/center image sound centered again.

- Calculates the stereo DRC biquad coefficients and flashes the separate Left and Right curves directly to the earbuds' chip.

- Once flashed, you can disconnect and use the earbuds on any phone, PC, TV, or console and they stay balanced.

**GitHub Repo:** https://github.com/Baran-sys/Anker-HearID-L-R-Calibrator

*(Note: This only works on Soundcore models that support HearID, since non-HearID entry-level models like the P20i only have a single mono EQ register in firmware.)*

Hello. I’ve had the luck to find IMF Super Compact II’s for an absolute bargain. Short question: I had to remove one mid and had to cut away the sealant, which was some form of very sticky rubber-like caulk. What can I replace this with (which is also affordable?) I’d rather not use foam here because it will be visible and stuck out from under the driver. Preferably also not something super sticky.

Full context:

I had to refoam the mids (as is the case for all of these models) which went… not perfect. The first was fine, with the second the cone came off the voice coil. Or rather, the cone somehow tore (or was already torn), because a small part of the cone was still on the voice coil. I glued that with two-part epoxy, which I now learned was a poor choice because the cone is made of polypropylene which doesn’t bond to glue according to the entire Internet. Nevertheless it looks like a strong bond and scraping away the glue doesn’t seem to work, so I’d rather leave this as it is, but keep the driver accessible if it needs further repair.

Any suggestions are welcome.

Ho ereditato un giradischi micro MR711, speaker Yamaha NS 690 Made in Japan e un amplificatore Proton 520. Il problema è che essendo un impianto di metà anni 70 credo, (custodito pare in maniera decente ma mai più utilizzato) non poteva mai funzionare alla prima accensione.
Premetto che ho testato gli speaker e fortunatamente funzionano entrambi bene.

Usando come sorgente DAD pc l’ampli ha un problema ad entrambi gli ingressi L sia di speaker A che di speaker B. Cioè quando collego le casse in uno dei due canali sento quella sinistra suonare molto meno dell’altra.

Le manopole volume e balance sembrano fare il proprio dovere. Se metto a zero il volume dell’ampli, la cassa L (cioè quella che suona di meno) suona lo stesso abbassandosi ulteriormente di poco.

Ho utilizzato spray contatti elettrici smontando la scocca dell’ampli ma non ho risolto.

Il giradischi
Da quello che ho visto su Internet è un bel pezzo di storia pesa un quintale. Ha un braccio stupendo e mi sembra non avere problemi, ho spruzzato spray ai contatti dietro la testina e su uscita RCA (il cavo dedicato del produttore era un po’ ossidato ma ho risolto con spray).

Non riesco ancora a valutare il suo corretto funzionamento, perché gli ingressi PHONO hanno lo stesso problema di volume che hanno in DAD. Inoltre gli ingressi PHONO hanno un volume ancora più basso del DAD.

A casa di mia madre ho un adattatore RCA con Jack per testare separatamente il giradischi con il mio pc e un mio vecchio ampli piccolino(che non sfrutterebbe mai queste casse stupende ma vabbè meglio di niente).

Sono una persona che ha un po’ di esperienza a smontare e rimontare pc fissi e smartphone di queste generazioni, ma non ho mai avuto a che fare con saldature amplificatori o impianti di audio in genere, ma potrebbe interessarmi la sfida. Secondo voi dovrei provare a cimentarmi io o dovrei rivolgermi a qualcuno che se ne intende? c’è qualcosa che potrei ancora provare prima di chiedere aiuto a qualcuno da pagare?

Aiutino grazie :)

please help💀 it makes a wirring sound and spits out the cd when I try to play it. I opened it but didn’t wanna mess it up even more so I closed it back. Worse case scenario I take it to this repair shop by my house, they said the base line fee is 125. which isn’t so bad but before I pay I would like to see if someone could help🤞🏽

I broke the speaker terminal block on my Yamaha AX-497.

Does anyone know where I could find an original or compatible replacement?

Also, how difficult is it to replace?

Thanks!

I have this Sony WM-F20 model and it looks dead. I've resoldered the battery compartments, plugged headphones in but no life still. Does anyone know what might be the issue? Thanks.

This repair is going to be a longgg embark. Will be fun tho, excited.

I given laptop for general service after service one of my speaker getting crackling sound. I told technician it was good before service but he opened and telling me that no its damaged he told if i damage it it should be like sharp cut but its like uneven cut

Iam in confusion still whether its his damage or not

Has anybody expierence with repairing this device? Where to buy spare parts?

Hi all, I’m working on a JVC R-1X stereo receiver (service manual No. 2557, 1981) and could use some advice.

Symptoms

• Left channel sounds normal.
• Right channel makes noise (not music). It stays the same with the volume at minimum and on every input, so it seems to come from after the volume control, in the power amp or its supply.
• Both speaker outputs (A and B) behave the same, so it’s not the speaker selector.
• When I opened it, the left fuse (T1A slot) was missing. I put in a 2 A fuse as a temporary measure, and I know it should be a 1 A slow-blow, as marked.

What I found inside

• Of the four output transistors, the one at X720 has a charred, brown insulator and a blackened, partly melted body. The label is unreadable. The other three (X719 = D895, X721 and X722 = B775) look normal with clean white paste.
• Per the service manual, X719/X720 are 2SD895UA (NPN) and X721/X722 are 2SB775UA (PNP). From the board layout, I believe X720 and X722 are the right channel (idle-current trimmer R728), but I haven’t confirmed it.
• There is also some charring on the board near D903 and a nearby resistor.
• The ELNA 6800 µF filter caps look fine from the outside (no bulging or leakage).

What I haven’t done

• I don’t have a multimeter yet, so I haven’t tested the transistors, measured DC offset, or checked any resistor values. The unit is not powered on.

Questions

1. Is a burnt X720 likely to be the cause of right-channel noise, or is that more likely a coincidence or old damage?
2. Where do people source 2SD895 and 2SB775 today? Any trusted sellers, or a modern equivalent that works in this circuit?
3. If X720 is bad, should I also replace X722 and check the drivers (2SC2235/2SA965) and the 0.22 Ω emitter resistors?
4. Anything else I should check before powering it on again? I plan to use a dim-bulb limiter and adjust R728 to 5 mV per the manual.

Thanks!

Does anyone know the measurement of Sharp GF-6000 Tape Recorder idler tire? I don't have the service manual or a Vernier Caliper to find out.

Hello. I have a Bose Solo TV Sound System Model 410376. My question is, when I press the button to increase or decrease the volume it just keeps going up or down. It doesn't stop when I stop pressing the volume button. Is there a way to reset the system sort of speak or any other way to troubleshoot the device before needing to take it in for service? Thanks!

It tries to spin the CD but it only moves a tiny bit and then it bounces back. How can i fix this?

Hi everyone!

I'm looking for clear photos or the original schematic of the amplifier board used in the PROEL WAVE12A active speaker, specifically PCB 33000054 WAVE AMP VER.

I'm repairing one and need to verify which components were originally installed, particularly around R12, D5 and R31.

Does anyone own this exact speaker or have access to the same PCB revision?

Even a few close-up photos of the original board would be extremely helpful!

Thanks in advance!

Hey guys, I have an issue with my speaker system where it turns on but all I’m getting are popping sounds with no audio. Has anyone had this issue with any of their systems before? What could be the cause of this? Any help would be very appreciated. Thank you.

I bought this along other caps at a local store. In the bag were Samhwa, Panasonic, Philips, and... This 1uf 63v cap. I cannot find anything about it online for the life of me. (the website of Sunelec / Suncon is down so couldn't go look there)

Anyone came across these and have any info on their reliability​?

Never messed with a broken board like this before, So not sure best way to approach it. Just take everything off and glue? Or should I source a similar board ... or?

This was just something to fix, thought it was prolly the caps cuz the lady said it didn't work, no sound.... welp, what's the best approach?

so, taking a break from working on my own setup, my Dad's stereo that he has had for my entire life finally has experienced its 1st issues.

1 being the cd changer finally gave out, that is likely not to be repaired and I am searching for a similar vintage discount changer to replace it.

And the other is what I am hoping to figure out here..

The NAD 7125 receiver is blowing fuses. The time delay fuses. And due to the sentimental value, as well as just the great quality of my dad's system, with surround throughout the house, I just want to save it.

I have it. Just opened it up, and gathered up the documentation I have on it here.

So I'll post along my repair journey and hopefully can get some help along the way. I need to order a pack of time delay fuses as I only have 1 of the sizes..

I have a pair of Audioengine A2+ that have worked great for me for the last 4+ years. Recently I have been getting occasional hissing or feedback noise from the left speaker. If I touch the metal on the red output the sound will dissipate. The sound doesn’t occur all the time. The left speaker will occasionally make a popping sound and sometimes will sound like the volume is muted or not outputting to its full volume. Speakers play fine if connected to Bluetooth on my phone and wires disconnected, ended up buying new speaker wires thinking that was the original issue but still am running into issue just less often. Wondering if my left speaker is on its way out or if it could be a different issue. I do have a router near the left speaker as well as Ethernet cables running similarly wired near the speaker cables on the underside of my desk. Have had this setup for 3+ years and just recently have ran into the issue. Any help appreciated! (Video of issue posted below)

speaker hissing

've had this TT for 8 years and its worked fine. The only issue it's had is excessive grounding hum. Last year I moved and had to put it in storage. I recently got it out and set it up. I had to get a new preamp when i set it up. At first it worked fine just with the excessive hum. One night, my cat knocked the preamp off my bookshelf. I tried playing something afterwards and it wouldnt play from both channels. It only plays out of the left speaker. If I swap the left and right inputs on the preamp the channel switches. I've read that means its an issue with the TT. I replaced the original rca cables and attached the ground wire to the negative. Now the ground seems to be fixed. The channel issue has stayed. I can get the right speaker to play when I barely insert the rca cable into the preamp and it was that way before and after replacing the rca cables. It cuts out when the rca is fully inserted.

I've looked at a few more things that could be an issue. I checked the contacts on the back of the cartridge (ortofon red) and they all appear clean. The blue wire doesnt fit tightly but thats an issue for the left channel which works fine. The contacts from the headshell to the tonearm are inside a cylinder on the end of the tonearm so I cant see what shape theyre in (the end of my headsheel has female ends going into the tonearm).

Does anyone have an idea of what it could be? Could the rca cable playing out of both speakers when it is barely inside the preamp but cutting out when fully inserted be a sign of damage on the preamp from where it fell?

Hey! What could be the reason for hissing sound on one of my monitors? Happens with or without XLR cable plugged in. Have tried resoldering components and different wall sockets for grounding without success. Hissing stops if I mute high from the monitor's control switch.

Constant hissing and some crackling sounds. Would like some ideas on how to fix these, I cannot find a used replacement monitor right now.