Hi there

Hum is one of the most frequent problems encountered by DIYers (and professionals!).
Here is a tool specifically designed to detect, identify, track and locate all types of hum: electrostatic and magnetic coupling, ripple, ground issues, etc.

In principle, the basic equipment of a normal lab or workshop is sufficient to do the job: a signal-tracer or lab-amplifier coupled to an improvised E-mode or H-mode probe for example.

However, a dedicated tool is very useful, especially for difficult cases.

The HumBoy can work as a basic signal-tracer, but it also has special features: one is the very high gain available (insane in fact, literally) and the other is the very high frequency selectivity: it includes three very narrow bandpass filters centered on 50Hz, 100Hz and 150Hz.

The reason for the 50Hz (or 60Hz) is obvious: it is the mains frequency, and basic hum problems are caused by this frequency leaking into circuits through electrostatic or magnetic coupling.

The 100Hz (or 120Hz) has a different origin: it is caused by the rectification process in a supply, and appears in the ripple voltage and the currents around the filter caps and the ground.

The 150Hz is the third harmonic, and is always present to some degree in the mains spectrum because of the waveform distortion, but when a transformer begins to saturate, some of the flux leaks out of the magnetic circuit, and these leaks consist mainly of odd harmonics, primarily third.

When hum appears in an audio chain, it can be a mix of different types, having different origins. You may be able to detect the fundamental by hear, but the ability to discriminate and track each frequency can help in locating quickly the origin(s) of the problem.

Finally, the HumBoy includes a detector coupled to a V-F converter, because the hum frequencies aren't within the optimum sensitivity range of the human ear, and its logarithmic response to the amplitude doesn't help either.
By contrast, the ear is extremely sensitive to small pitch changes, helping to direct the search and quickly locate the source, and hopefully the culprit.

Its input can cope with different types of probes: direct, magnetic or electrostatic.

In the direct mode, it can be connected to a supply voltage, to detect residues of ripple for example.

The magnetic probe (typically a small drum-core choke) sniffs magnetic leaks from magnetic components or AC currents in a wire.

The electrostatic probe (typically a small pigtail left bare at the end of a coaxial cable) identifies unwanted capacitive couplings.

This is the circuit: it is just plain old analogue technology, nothing especially smart or fancy.



This is the finished tester:



I have included all possible bells and whistles.


These are examples of probes:



The yellow one is the general-purpose magnetic sensor: a 10mH choke, electrostatically shielded.

The black one is the miniature magnetic sensor, capable of locating a single wire in a bundle.
This pic shows its construction: it is made by winding a large number of turns of 0.03mm enameled wire around the center conductor of a miniature coaxial cable.



The inner conductor is made of steel, thus magnetic, and acts as the core of the inductor.
The inductance is 600µH and the resistance 50 ohm.

The last one is the E-type probe, also capable of accurately pinpointing a source.

The sensitivity is absolutely insane: in simple, audio-tracer mode, it is capable of eaves-dropping the audio from a regular telephone pair, without contact just by magnetic induction.
In bandpass mode, it is capable of detecting the 50Hz magnetic field generated by a 110kV HV power line from a distance of ~1 mile.

So for starters: yes I know there are some great products out there like MiniDSP or HifiBerry and the like, but this is DIY and I want to make it to MY spec.

The idea was to use 4 ESS 9038PRO DACs (https://www.esstech.com/wp-content/uploads/2022/09/ES9038PRO-Datasheet-v3.7.pdf). Two for each channel (stereo) for full differential. ADCs as well, but I still haven't reached a verdict yet (Delta vs SAR). The main deciding factor there is if I want to meet the spec of the corresponding DACs, or if I just want to use audio ADCs simpley because that's what they were designed for. An additional two ADCs for return lines from the speakers themselves (signal attenuated to usable levels etc). Optimally, this would be all hooked up to a Sharc DSP. I like Sharc because I think Sigmastudio+ is a great solution for me because I am not the most amazing coder (admitedly I still need to learn more about CCES). That's the skinny of it. Analog Devcies has a good project board I was thinking of maybe using as a starting point (https://www.analog.com/en/design-ce...ards-kits/sharc-audio-module.html#eb-overview) but I am not sure if there is enough I/O for an expansion card to use the other ICs. I do intend to have the board made, although if I need to solder on some components, so be it. I do have hand solder experience.

At the heart of it, where would the design process for that start and is it possible to do as a DIYer?

Disclaimer: I am not an engineer. Just someone who really likes audio and knows a thing or two about electronics. I understand that, yes, this would be a massive undertaking. I am certainly open to criticisms because I do not know everything. But please do not post here if all you want to do is berate me and tell me I don't know what I'm doing. I am posting this because I know I cannot do this alone, and could really use some advice. I really like this forum. I've learned an immense amount in my short time here. But I also see the tendency for some to just brush something like this off, or use it as a stage for a soap box rant about what a moron I am. That's not why this is here. I am here to learn and grow and am willing to put in the effort.

So where to start?

Looking at 10+ year MC (or MM) cartridge that has been seating on a shelf, do I have to care about the suspension loosing its compliance (or other mechanical properties)? The internet says that this is the case, but that’s found mostly on audiophile forums with not enough rational to back it up. I can see it is possible, but would like to see some data or even more scientific speculations backing this up.

Has anyone read about or measured this?

Hey all,

OK, so Number One Son came home from college for Thanksgiving, and asked if I had an oscilloscope....I was initially surprised as to why he would enquire about one, aside from wanting to beat his younger brother over the head with it...

I showed him my two oscilloscopes (both have not been fired up in 10 years) and he asked a number of questions... I told him its for veiwing electronic wave forms...that was as simple as I could describe it - he is a Computer Science Major...

Anyway, he sent me to a YouTube vid on Oscilloscope Music...

Login to view embedded media
So question I had was is it possible to "harm" your system with uploaded internet waveform audio?

Hi, I have an amplifier designed by a French manufacturer around the 2000s, this amplifier looks a lot like the

Beard p35mkII,
the output transformers, the same models that integrate the JADIS amplifiers, because the manufacturer was in Toulouse.

I would like to improve this amplifier, if you can help me?

I started by replacing the capacitors that were out, but I think we can do better?
Regards
Gil

Hi,
I'm reading the Bob Cordel Designing Audio Power Amplifiers (2011) interesting book and I have a doubt:
on page 37 (see attachment) it is said that the output impedance of the current source in the figure is 290Kohm. I get a different result. It should be Ro=ro(1+gm*Re) which is equal to approximately 1900Kohm, considering VA approximately 100V. Can anyone explain to me?

Reminding the TMC.
Instead of feedbacking only the VAS by an integrating capacitor in Miller compensation, at low frequencies the output gets also included. This will decrease the distortion of the output.
With two pole compensation, only high frequencies are submitted into integration.
The problem occurs with TPC when the loop gain is too high, the upper audio band needs to be included in the integrator. The answer is LKA's 3 pole compensation or instead of integrating only the VAS, why not as with TMC include the upper audio band from the output to be integrated.
Bellow is a circuit designed by @lineup that I applied to.
https://www.diyaudio.com/community/...plifier-15-watt-with-tmc-and-laterals.406282/

The global loop gain is promising 74db NFB @20khz. The inner loopgain showing 24db. By this the output stage is corrected by 98db@20khz.

Hi Dave,

I've been running the Visaton. B200s you modded for me, in open baffles for a number of years now. The one area I'd like to augment if possible is the HF. I'm wondering if you have any thoughts about suitable AMTs to partner the B200s?

-Raja

For sale AD811 in DIP package. 4 chips available for 10US each plus the shipping.

Hello

I am working on a JL 1000/1 where I replaced all of the 2/3 way switches. It looked like the amp sat outside in the rain or something because all the switches had corrosion on them.

I tested the amp prior to replacing the switches and it powered up and played fine, although I didn't do a high power test.

Anyway, I replace all the switches and go to power it up to test. I usually monitor the amp with a thermal camera during power up and I notice one of the PS FETs getting hot. I power off and measure it, and it's shorted. I remove the bad FET and measure all the remaining PS FETs and they all measure OK. I try to power up again and now another PS FET is getting hot, ends up being shorted as well. I remove it and try again, it's like a chain reaction of failing PS FETs.

I decide to remove all the FETs and look at the gate drive. It looks unusual to what I'm used to seeing, square wave from 0V to 12V (or whatever my input voltage is). It is swinging from -13V to 14V. Is this normal? This is measuring directly across the FET from gate to source.

With all the original PS FETs removed, I put in two IRF7545, one on each bank of the PS and the amp powers up fine (idling around 2.4A). With the IRF7545s the gate drive still looks the same.

I'm not sure what happened to all the PS FETs when they were working before. The amp literally just sat in a box until the replacement switches came in. 😵

I've been mucking around with 12AX7s lately.
In the middle of building a phono stage, which is sidetracked with power supply issues at the moment. But, I was thinking of ways to more easily put together a couple of 12AX7 gain stages, and I came up with something really simple -- put an LND150 high voltage/low current MOSFET as a CCS in the 12AX7 plate. (Diagram attached.)

The advantage I see is that you can get a healthy 1mA of plate current through your 12AX7 with only a 250VDC B+, and still have a high enough voltage at the cathode to keep the 12AX7 out of grid current.

I whipped up the example with an LND150 as a simple, single-device CCS for the plate load, and a red LED for the cathode load. The B+ is 250VDC.

The results are encouraging.
Lots of gain - over 80X.
Low THD if the stage is loaded lightly.
THD is all 2HD.
No high wattage resistors needed, so it's cheap.

The LND150 dissipates 54mW in this configuration. I figure that's quite safe.

Does anyone use this? If so, does it work well, or are there hidden gotchas?
--

Not DIY but hopefully someone can help. Wife has just upgraded her phone which now doesn't have a headphone socket but she does have a half decent pair of headphones she likes to use to listen to music on either plugged into laptop. USB-C headphone adaptors seem to start at $4 but at what point are they worth getting for a casual user who just wants it to last beyond the warranty period?

i have too many projects and I’d rather this get built soon by someone who will listen to it.

Bought it in the lottery for $187 delivered to me, selling for $175+ship

Includes exactly what comes in the kit, all new and only peeked inside to check out the boards and transformers.

Only an observation when using an iPod G4 with a Wuzhi Audio ZK-601 mono amplifier using a TPA3118. Firstly the amp works fine with no bad behaviour on startup or shutdown and sounds OK. The odd thing is when the iPod is used as a source with it's volume at max all is well but when the volume on the iPod is adjusted below max there is high frequency noises and hiss. Return to max and all is well. I haven't come across this before with any other amp Class AB, D, T that I've used with the iPod. I've tried other sources such as a phone and a headphone output on another source which do not have this issue so it must be iPod related.

The amp's DC offset was 11mV when cold and close to 0mV when warmed up. The DC offset on the input using the iPod is 0mV at max volume but increases to 100mV+ when the iPod volume is decreased. This is measured at the input terminal block next to the used 3.5mm socket so may not be accurate. The only difference I can see compared to other modules I've used is that this appears to mix the stereo signal to mono.

It's not an issue as this is just a test amp for a mono test speaker that I use but is puzzling.

Most people use a leisure amp at low power averaging less than 5w but required to have 10 times headroom. This indicated a class AB amp. At low levels the crossover is the main trouble that results harsh high frequencies if the crossover is not right. Each pair follows a square law function, if a single EF is used as the case with CFP, the crossover can near perfection. With 2EF each pair should follow square law which results 4th order and 6th with 3EF which cannot get good crossover.
This Amp uses high current VAS that can pump 100ma in classA. To drive high gain high current a novelty is introduced in the IPS. The opamps are CFA amps with high bandwidth, by linking the negatives I transform it into symmetrical complementary differential, see the internal circuit, and by joining the outputs the supply current of each carries the error with over 100db gain. The output is biased 100ma and results 0.00014% 1w 20khz. It has 5v dropout which is too high.The AD8008 is ultra, ultra, ultra low noise, distortion, high frequency, that comes at cost.
It needs Zobel and Thiel ,the high impedance inputs can be Paduk way.

Greetings all, new but have learned a lot through reading. I have aquired a pair of sonics. Mine are the 600x or the 5b's guts. Next to nothing for info on the net, nada. I would like to use these in a monoblock set up, one per left and right fronts. The xlr LF output and the xlr crossover input have me pulling what little hair i have left out. Kinda new to this and totally new to xlr. These amps were gifted to me by a very close freind and would love to fire them up but am lost on how.
Any info from anbody woud be greatly appreciated.
Avr is a yamaha rx v 659
And the back of the amp

Just in case, Stereolith is this: https://www.stereolith.com/

I have some nice 165 mm AlNiCo woofers and various HF units (also some planars, not shown). I liked the SSS (single speaker stereo), so I should definitely put a box together and experiment a bit with this sort of loudspeaker.

New kit as received from the DIY Store. Package opened only. $150 postage included in CONUS. SOLD!

Michael

So I ended up with a pair of Sonics 800x amplifers (Bryston 7B NRB amps with a custom input stage) that are in perfect condition, and I enjoy the sound. Unfortunately, as they lived their life in an IMAX theater before I got them, they dont have soft start, or speaker protection circuits, or a power button. I am looking at adding those items, as well as re-capping it, since it is 30 years old this month.

I will admit total ignorance in the electronics area, but I was looking at the boards diyaudio offers (Soft Start & Speaker Turn-On Delay / DC Protector Combo – diyAudio Store). Am I incorrect in assuming these should work for my needs?

Does anyone know of someone who would be willing to take this on (or really mentor someone through this process)? I am in the central ohio area if it is of any difference.

Hi I have a couple of Celestion Pulse 10 bass speakers and looking to build a box for them. The specs on the speakers are Fs 66.3Hz, Qts 0.444 and Vas 1.06 cubic feet (thats for one).
Can anyone tell me if these speakers would be suited to a sealed or ported box. Have a idea of a ported box with a volume of 2.7 cubic feet and Fb of 40Hz and have managed to draw some responce grapths but any opinions would be gratefully received.

What wattage should R18 and R19 be?

Here are my open Baffle speakers. Based on Mark Audio 5.2 and Eminence Alpha 15A. Just waiting for parts for the crossover

I have a PC650 that has developed slight turn on thump and a more significant turn off thump on all channels that I need some help solving.

The current configuration on the test bench has one pair of speakers attached to the rear set of outputs and a single woofer attached to the subwoofer outputs in bridged mode. I have the input board removed, but it makes no difference in or out and gain controls do not make any differences.

The turn on thump is about equal timing on the three speakers. The turn off thump happens twice and isn't always equal on all three speakers. DC offset measurements on each channel can be observed at startup and shutdown. While the amp is operating the DC offset on each channel is at acceptable levels.

This amp does not use the ceramic driver boards and it also uses 7915/7815 as regulators. It does have the 4n25 optocoupler in it, but I don't measure anything wrong there.

Any tips are appreciated.

So after the real success of doing the 3020 and 3130 ive decided to do the 3140
You dont see these about much these days-i dont thnk as many were made like the other 2

Few different challenges on this one, particularly the sighting of the FETS-Ii might need a different heatsink, we will have to see

So part one is the dismantle and check it over- and this is what i do to all of my amps as a standard proceedure
someone kindly glued the knobs on-a little bit of gentle heat and they are all off
the spindles will get cleaned and buffed up before they go back on
all screws will be removed and resprayed
cover and base plate are cleaned with Mr muscle(i find this the best and least agressive) then they will be stored away

looks like someone kindly recapped this before i brought it, that was good of them wasnt it

Whats left is cleaned in 3 stages
first it is hoovered out, then blasted with compressed air to get rid of any dust
then i clean with 2 different cleaners-holts electrical contact cleaner, then AAB contact cleaner, this leaves a nice finish

Next step once all is dry will be to check the amp over to make sure there are no nasty suprises or faults before i start the conversion

Alright, the subject is pretty self explanatory, I'm at that stage of a design where I'm dotting the i's and crossing the t's. Below is the schematic which represents the status quo of the current prototype with an actual measurement of THD v.s. output power at 1kHz included. I've obviously tried just about every trick in the book, hence the fact this is the 30th revision of the prototype schematics, some revisions were small just a resistor value change, some larger, and I am hoping to get some suggestions on how to improve THD > 20W, as currently the THD rises significantly after that point. I have the prototype on the bench, and the simulation running on the PC and interested to try suggestions, as I'm sure there's still room for improvement! Looking forward to your replies!

Hello,

I had repaired an old Trace Elliot GP7 SM300 (300W bass amp from a friend). Some transistors defective and a break on a pcb trace, which will have been the cause of it's first death. During the test on a 15" (4 Ohm) i cranked up the volume and at a loud level all the transistors went into meltdown again. After some research, the design basically does not seem to be so super destruction-proof. I assume the repair attempt was actually successful, it was just too much somewhere during testing.

The question: can the circuit be made a little more damage-proof with a manageable amount of effort?


There was already a modification (by someone else). The red resistor was soldered on the bottom side of the PCB.

The service manual is available here, for example: https://elektrotanya.com/trace-elliot_gp7_150-300watt_sm.pdf/download.html if necessary.
The toroidal transformer is primarily fused with T3.15A and there is approx. +-70V after the rectifier.

In my test at the moment when I was turning louder, the following transistors broke: TR 11 and on the +V side: 13,14,16 and on the -V side:
5,6,7,15 and the transformer fuse.

I had previously checked the DC offset, and a 1kHz sine wave looked clean on scope (does this bring more stability to reduce the quiescent current,
and e.g. rather have 0.5% THD instead of 0.01%?)

hello

2 pcbs for sale makes k8010 and k8011 valve power amplifiers from velleman
new never used very rare hardly ever seen for sale
£110 the pair plus £10 postage royal mail tracked (payment via paypal)

best regards

Built with pride in Slovakia 🙂 by ZenMod.

Top of the line model with Finmet AVC, Toshiba JFETS. 2x RCA inputs, 3x Balanced inputs and a pair of both SE and balanced outputs.

24 step volume control. Remote control works spot on.

It has 0dB to +8dB gain which can be selected by internal jumpers.

Seriously great preamp, I’ve tested it against Don Sachs 6SN7 preamp (with the nice LINLAI Global Elite 6SN7) and also against Holo Audio Serene. It performs in the same league, and it’s the one I kept - but I now find myself going DAC direct. Iron Turtle neither adds or takes away, it’s just that I don’t need it anymore. It only has about 300hrs on it and is as new. I am the original owner.

Asking £1,600 + shipping or collection from Oxford, UK

I have designed a digital crossover and exported the impulse response. When looking at the hipass filter frequency response with REW it appears that the low frequency attenuation is quite poor, REW shows a positive slope. At 2Hz attenuation is only 20 to 30dB and continue to rise I guess up to 0dB at 0Hz.
Here is a plot of a simple LR36 at 8KHz:



I should have missed something but can't figure out what...

joël

Hi,
I'd like to share a recent experience. I've been looking at low cost power supply solutions for pre- and headphone amps, and after a bathroom refurbishment at home I noticed a very nice isolation transformer in the shaver socket. I quickly bought two second hand on ebay for £5, and was pleasantly surprised to find a 20VA transformer with a tapped secondary. Tried both full wave and bridge, with load currents in excess of 50mA DC. Full secondary DCR is 140 ohms. Add a small smps for heaters and there is a low cost solution. Not for everyone, but may be of interest for some.

Upgrading the drivers on my Model 3 left me with the OEM tweeters/mids/woofers (and an OEM sub that I thought I'd install but decided not to risk the warranty).

Since then, I've gotten into making bluetooth speakers for family/friends and have learned how to use DATS/Winisd/REW/VituixCAD2 to get better results.

I'd been unable to find the TS values for the Tesla speakers online, so I recently measured them myself using DATS v3 and added mass. I realize this is a niche use case, but does anyone have a recommendation on where I can post this info online to help the next person that might want to reuse these drivers? Perhaps the values could also help car audio people better understand Tesla's design decisions to aid in their projects.

Thanks for any ideas! Here's an example of what I captured for the mids:

This CL0800 project is a closed box satellite with directional frontal emission.

The driver is a Faital-Pro 3FE25 already used in previous MDD projects. The CL0800 satellite sounds good although limited in bass.

The case is oversized, I will need it as a compression chamber in the next MDD project.

Construction is simple and inexpensive. The unconventional stand has a subsonic resonant frequency at approximately 1 Hz, isolating the satellite from the floor in audio band. The wiring is original in that the negative pole wire passes behind the radius of the basket in ferromagnetic material, avoiding inserting material inside a coil that can generate hysteresis phenomena and consequent distortion.

I have placed various links to old documentation on MDD projects on the "before" and "after" pages.

Thanks for the attention

https://www.claudiogandolfi.it/cl0800.html
https://www.claudiogandolfi.it/prima.html
https://www.claudiogandolfi.it/dopo.html

Hello all

I am on the way of designing and coding the relay volume control. I will use this resistor arrangement with 7 or 8 relays allow me to get 128 or 256 steps of attenuation. I use online calculator to get the resistor value to get more the 100 db attenuation.

My question is, with this resistor and relay arrangement, I notice that even at the lowest step/position which should be no signal out but at the lowest step it does not bring the output to ground like normal attenuator. Does it be completely silent at the first volume step? or I do need one relay to short the output to ground to make it silent?

Thank you for every help
Tanwa

@PK1, your emails are bouncing.

Peter contacted me about this design that i did in 2006 (Scott’s alignment).



The original sletch from the late ’70s was for the B139, modern modeling showed it was almost right on for the Jordan JX150, and when Scott came up with the alignment i drew up some potential ideas. I don’t know if the TTL has been built, but i have been contacted a few times before. Other versions of the same alignment have been built and were reported to perform well.

I’d really like to see one of these done.

I have updated that drawing (cosmetics and comments only), and i did do a sketch for driver placement for another chap. I have enclosed the updated drawing.

I have given bracing much thot, still not quite sure how to best execute. Bracing the driver and baffle against at least the inner partition i would consider minimal. The angled partition braces all the other panels but the top.

https://www.t-linespeakers.org/download/TriangulatedTL-B139-050923.pdf

dave

I have n.3 Selectronic R-core transformer 230 primary 2x15 secondaries 30VA. 25€ each or 60€ for all.

Hi, I'm currently building a simple amp for a 10 inch 150w subwoofer for a friend.
I don't have LTSpice models for mj11015/mj11016 , I just simulated with BD and some 2SC/2SA might not be the way to go, but...

• Using darlingtons in the output stage might be harder to keep them not thermal run away? Should I place Q5 on the heatsink with the output trans or close to it?.
• is it ok to limit the bandwidth with C12 ? or I should not and build a op amp based low pass filter at the beginning.?

* use low pass filter and also limit the bbandwidth as well? since it won't play past 150hz.

- 100W output is what I aim here. 200W 30A output transistors I think are sufficent , Since you can get 60W from a pair of 2SC4468/2SA1695 100W/10A trans.

- Bruno.

https://interestingengineering.com/...-of-the-ear-simulates-every-aspect-of-hearing



dave

Leach's article in Audio mag of Feb 1976 is still online worth reading

Hi

Click to expand...

diy sony vfet pt2, suddenly channel mismatch, left channel dropped down i volum, it's stli sound but lower (have checked preamp and dac). any suggestion?

Andreas

Hey all, haven't been here for a while, nice to be back. I'm planning to build a pair of Marantz Model 9 amps this winter and I have a question. I'm awaiting the arrival of a pair of Sowter input transformers, 10k/10k. I bought them because the English economy is on the skids and the price was very good. I would start by fixing the low frequency filter. And also do away with the phase inverter and the first half of the 6DJ8. But my real question is about conversion to a differential amplifier with a transformer input. Would it compromise the quality of the amp? Or is it build it and see thing?

WBT-0210 Cu nextgen RCA socket - 4 piece​

light used in excellent condition.

WBT-0210 Cu/CuMS nextgen RCA socket | HIFICollective​

WBT-0210 Cu/CuMS nextgen RCA socket

Purchased from Hificollective for £108.

Selling at £60 including PayPal charges 5.5%.

ETI Research PhonoPod, TeCu Gold Plated Female RCA socket - 4 piece​

light used in good condition

ETI Research PhonoPod, TeCu Gold Plated Female RCA socket - DISCONTINUED | HIFICollective​

ETI Research PhonoPod, TeCu Gold Plated Female RCA socket - DISCONTINUED

Purchased from VH Audio for $116.

Selling at $60 including PayPal charges 5.5%.

HIFI TUNING SUPREME 3 COPPER SLOW 5 X 20MM (T) AUDIO GRADE FUSES​

Audiophile-Grade Fuses, Your system will play with increased power, dynamics, clarity, and coherence.

Available for sale is 200mA and 4A.
light used and in excellent condition.

Purchased from Analog seduction UK for £45 each.

Hifi Tuning Supreme 3 Copper Slow 5 x 20mm (T) Audio Grade Fuses​

Hifi Tuning Supreme 3 COPPER Audio Grade Fuses
www.analogueseduction.net

Selling at each £30 including PayPal charges 5.5%.

HI-FI TUNING GOLD PLATED SILVER CERAMIC SLOW 5 X 20MM (T) FUSES​

Audiophile Fuses: Hand made in Germany, pure silver wiring, gold over silver end caps, ceramic casing, cryogenically treated.

Available for sale is 7A and 8A.
light used and in good condition.

Purchased from Analog seduction UK for £35 each.

https://www.analogueseduction.net/fuses/hi-fi-tuning-gold-plated-silver-ceramic-fuse-10-amp.html​

Selling at each £20 including PayPal charges 5.5%.




Shipping to Worldwide at buyer's risk, but it will packed carefully.

Shipping to world will be through INDIA post Registered mail which will take 2-4 weeks.

Please contact me for shipping charges.

Thanks for looking.

Hi all,

I sometimes see people trying to put DC feedback loops around phono preamplifiers. When you put a DC servo loop around a phono preamplifier, the feedback shifts the poles, particularly the lowest one, and may mess up the RIAA correction accuracy. One way around that is to deliberately shift the correction network poles such that they end up where they should be with the DC servo loop closed. I did some calculations about that, see the attachment. I hope it will be of use to someone.

Best regards,
Marcel

at $69US and 10 inch it has no competition - a tapered line - ABC - partially filled reflex should work well. My 10FR300 is stuffed into a tiny 0.62 scale K15 Karlson and has one fake Scotch Brite pad over its vent - not sure how much good that does with its 28 liter rear chamber.

I'd imagine something useful could be done with 60 liter;s airspace.

Ever since I came across this (I was perhaps 12) I've always wanted to build one - a friend of the family had one with a marble baffle. One day I will - and I have the perfect old barn to convert to house them.

But... it set me thinking. Would it be possible/desirable to build a similar thing for a BIB? Using two solid walls (and I do mean solid with no cavities behind plasterboard) and a front baffle of good play would it work for a BIB? If one got the cross-sectional area and height correct as per the BIB calculator? Such a thing would blend well into a wall and be hardly noticeable.

(Furthermore the WAF measurement could be enhanced by wallpapering the entire room and the front baffle with woodchip painted with magnolia emulsion.)

Last comment aside it IS a serious question!

Dear all,

After many years of satisfaction and enjoyment, I found an opportunity to upgrade my system.

I started with the replacement of my 1505B driver, a 291-16A, with a Yamaha 6681B. Amazed by the result, I started to study a bit more about Yamaha loudspeakers and I found that the 15 inch 3882 could be an excellent bass loudspeaker for a front loaded horn like the VOT.

Finally, I discovered this bass cabinet, the S6215, with two 3882 and more a less the size of my A5. They were in LA and I found a way to get them shipped to Europe. So all loudspeakers are Yamaha, including the excellent tweeter 4281B. Only the 1505B is still Altec.

The result is just outstanding... I am using a passive crossover and Jriver for small EQ adjustments.

I started ordering parts 10 1/2 years and 2 houses ago. Now it's mostly mounted on a chunk of 3/16ths aluminum.

Jan 12AT7
Russian 7198 equivalents
Coke bottle 5U4
Hammond 272.....EX?
Hammond 20H choke
Trancendar OPTs. 5k:8Ohm

Next step is a plywood cradle for it to sit on during the build.

I'm going to do some sort of fancy wood frame upon completion.

I'm mounting the power cord and fuse on the base. I'll move the switch there if it seems to be a noise issue.

Ignore the plugs next to the power tubes. I realized I was probably going to burn myself using the volume knob and power switch. Makes for a sub-optimal listening experience. Live and learn. This is my first tube/valve chassis.

Hopefully people posting will guilt me into continuing progress!

Stay safe.

I could not find a quick-n-dirty place where this info was already compiled, so figured I would start a new thread here.

Quick back-story: I am "rebuilding" a couple dayton plate amps that have been repaired so many times that I am just tired of messing with the original design. So I have traced down the pinout of the original pre-amp section (with xover, phase, level, auto-sense, etc) and will interface that with a cheap IRS2092 module I got from China.

Here is a pic of the board I got:


Now for the (possible) issue...

I have read that there are a couple resistors that this board commonly ships with that need to be replaced?

Seems I recall EVMan asking me about this (but I cannot find the post where he asked me to save my life) and...

Furthermore, he made mention that R11 an R13 on his samples arrived with the "wrong" values.

The 2 samples I have arrived as follows:

R11 = 10K
R13 = 100

I am NOT SURE if the resistor number (R11 and R13) correspond 1:1 with the resistor numbers on the IR reference design sheet that I found online - which further has me a bit afraid to just start swapping out resistors.

From what I have gathered, R13 should be replaced with a 3K (currently 100R) to reduce the gain a bit (better SNR?). Seems this would be a very important "update" or "fix".

Additionally, some have mentioned replacing R11 with a 8.2K (currently 10k) - has something to do with the switching frequency I think? How important is this "update"?

If someone has any experience with the particular version I have shown above, any feedback would help a lot.

Some additional notes:

I would assume it is safe to replace the gain resistor (R13, 100R) with a normal through-hole resistor carefully soldered to the pads - cannot imagine much issue here.

The OTHER resistor - R11... That one is literally right next to the chip and in a spot that I may not easily be able to do this without having leads of a couple inches to/from a normal through-hole resistor. IF I have to replace THIS resistor - would the length of the leads cause any issue with inductance, etc? In other words - will this particular resistor NEED (more/less) to be replaced with another SMD?


I plan to use this board with a +/- 62VDC power supply pushing a 4 ohm load. Anything over 200 watts is more than I need for the given application.

The Universal Driver Board (UDB) was a concept that was underway in 2009 when the 6L6GC in AB2 thread appeared. The design concepts are discussed throughout that long thread. The circuit features two cascaded LTP's made from dual triode tubes. I have made several different versions of a similar design with 9 pin miniature, and octal tubes. The Octal version was used for Chrish's amp design, and for my test breadboard. Several different types of output tubes have been tested through my breadboard. The thread is here:

http://www.diyaudio.com/forums/tubes-valves/133034-6l6gc-ab2-amp.html?highlight=6L6GC+AB2

Shortly after Chrish's amp was done, it became evident that my engineering career was in jeopardy, and I had to devote most of my time to keeping it alive, so my amp never got finished. In 2014 my 41 year engineering career ended, so we packed up everything and left south Florida. The "6L6GC" thread fell into a 4 year sleep during that time.

It turned out to be a hasty exit and I had to sell, give away, or trash over half of my stuff. What was to be a long careful packing, labeling and moving job got compressed into 3 weeks, so things were essentially randomly packed. The breadboard built during that amp design effort has never been found, so I assumed that it was lost, and set out to build a new one.

I laid out a new board that used 9 pin tubes since there are far more different flavors to choose from. I had a batch of the boards made by a commercial PCB vendor, since they were to be the next Tubelab product. That was early in 2015. About this time my daughter returned home with 4 kids and a husband, which we are supporting, so Tubelab again got pushed back into the corner. That situation has still not been resolved, and often requires most of our time. In the exit from Motorola and south Florida, I also lost access to my web site. I am working on that as well, but that's also why there hasn't been any recent updates.

The batch of UDB's sat in their shrink wrap on the shelf, until we moved again into a bigger house. In late 2015 Chrish woke up the original thread, which prompted me to build a pair of my UDB's and a new breadboard. First seen in Post #630, the board, and new breadboard finally saw life in early 2016, post #651. There have been a few random tests since then, but nothing too serious, just 250 watts from some transmitting tubes.

I have ideas on building a few amps using these boards, and I have sold 4 of them, so it's time to put together some documentation. There will be more posts in this thread in the coming days with real data on test amps. The initial choices for output tubes is KT88's, and the amp has already been fired up on bench supplies.

Doesnt happen very often so those who did it deserve the credit .

The CAV A8M comes into the shop badly burned since the costumer plays in the rough side i think probably too loud with heavy loads while the amplifier has been repaired ( badly also ) previously

Inside the notorious SAP 15-P-N inside a circuit that proper balance is very important to achieve stability .Seems that the amplifier has been repaired in the past more than once , probably by the local distributor , and wears inside all shorts of available versions of SAP 15 ...Obviously this is not the way to achieve stability .


On factory though the quality of make , order , symmetry and arrangement on the boards is exceptional for this type of product .After a quick argument with the local distributor who claimed that he never had a schematic a quick phone to Jenny and Ken proved to be a walk in the park and before i hung up the schematic was in my inbox .

That is a service minded company and in the feature i will never question getting a CAV product Already have a pair of speakers that i am thrilled with .

Well done Ken , Jenny thanks to your service minded policy the A8M is up and running again !

In between enjoy some pictures of the repair ...
Kind regards
Sakis

Hi guys,

I am building a tube preamp using either 6n2p-ev or ECC85 (not decided yet) in SRPP, so B+ current is very small, let's say, 75-100mA should be enough for two tubes, and heater currents are either ~340mA (6n2p-ev) or 435mA (ECC85), so let's round up to 1A for both. Plus, I'd like to use a tube rectifier EZ81 (in half-wave mode), it adds 1A more to the heater windings.

Here is the list of the transformers I am choosing from (a compromise between the quality, price and availability in EU) https://sklep.toroidy.pl/public/assets/Mains_for_tubes_ENG.pdf

The model 80/001 with 275V (0,12A) and 3,15 - 0 - 3,15V (7A) or even 80/002 with two heater windings fits perfect, but my concern is a size of a transformer, as it should fit into a limited space of the integrated amp (I'm replacing its low-quality build-in preamp) i.e. it's diameter might be <= 90mm. If going down to their 60/002 model (which is 86mm in diameter), it'll give only 3,15 - 0 - 3,15V (2,5A) (let's ignore its lower B+ atm).

So, my question is if currents in this list are already given provided a 50% power overhead or not? Does anybody have an experience with regards? I mean, according to all recommendation across the internet I need something capable to give at least 2A x 2 for heaters, but maybe these transformers are already good enough providing the real specs?

Or one can say no, only 80VA models, then I'll try to fit it, maybe, cutting off for these 5mm here or there =)

Hi Folks! I am having a bit of trouble with Flamma FS06: the level knob does nothing, and the saved presets kinda "unset" themselves. Let me elaborate.

This pedal has five standard knobs: three-way equalizer, level and gain. And it can "remember" the specific setting, for each of the 14 emulated modes, when one presses and holds the "select" button.

I recently noticed that my level knob does nothing: I turn it all the way back and forth, and there is no change in the output whatsoever, in any mode.

Gain and frequency knobs work fine.

I also noticed that the saved presets sort of unset themselves in a couple of seconds now: when I save the preset, the light indicator for the selected amp model blinks a few times and then it is supposed to stay on unless I touch the controls and change the settings. If I do change the settings, the light starts blinking indicating that the setting is now different from the saved preset.

Well, now the indicator starts blinking again in a couple of seconds after I save a preset even if I touch nothing and change nothing.

I kinda think that these two mulfunctions are related: the level knob reports something to the device which makes it think that I am changing the preset.

I tried to find some kind of customer support on the Flamma web site but found only chat, which noone responded to so far. I tried Amazon, where I bought it, but it's been over 120 days, and they won't do anything.

Any suggestions? Anyone thinks it's reparable?

Here it is:

Hi all,

Very specific question, but does anyone by chance have the August 1992 issue of MJ Magazine lying around?

Firstly ...I didnt know which forum to post this question in, but its kinda (very) analog in nature🙂
And so moderators, please move as you see fit.

HI Folks
I am putting together a secondary system based primarily on vinyl but also including CD format.
This system will get used a lot as its in the den just off the kitchen so of course I am looking for decent sound.

Regarding the CD equipment… I have two typical mid 90’s CD players that have both digital RCA out and Toslink output ports.
I would like to put one of them back in to service in this secondary system.
They have both proven to be very reliable over the years and so I would like to stick with them.

But my understanding is that DAC’s and the analog sections that follow the DAC have come a long way since these old CD players were sold.
So I am thinking of using these CD players as transports and buying one of these new thoroughly modern but inexpensive DAC’s.

But will doing this actually improve the sound over what these (old tech?) garden variety players can provide?
And are these new DACs a good fit for this purpose or are they really intended for something else?

Thank you all and best regards.
Curt

I am building a tube preamp to go with my custom built Turntable and DAC .... I know nothing about tube amps - everything I know I learned from another forum user on DIY who told me I should build a "serious preamp" and helped me source parts. I'll let him identify if he wants to, but he was ok for me to share.

Will need more help and advice along the way as this is a tough project I think for me. I'm calling it "Serious Pre" in honour of the inspiration.

Overview

• Single input (SE or balanced), Single balanced output (could be SE if desired but who would want that!)
• Two volumes - one for each channel therefore balance not required.
• Simple design derived from Japanese magazine April 1993, one signal tube (5687) split for both channels, 3 resistors and one cap for each channel
• Power transformer re-purposed from vintage Kenwood W-24 amplifier, One rectifier (6x5 tube) Two new mouser transformers for heaters
• Tango output transformers (anyone know how to source them from Japan online?)
• Vintage caps, resistors, voltage and amp meters, tubes
• Tocos Cosmos pots
• zero extraneous components that aren't needed to improve the SQ (but the meters are cool and vintage)

Fusion360 Mockup (not actual parts but rather conceptual right now)


Based on this April 1993 circuit with substantial? modifications provided to me by the DIY inspiration user ....no Phono stage, single 5687 for both channels, etc.

Hi,

I am trying to interconnect two ADAU1701 DSP via TDM8 but I am not getting any sound, so any help or guidance is greatly appreciated.

First DSP (A) is configured as master (PLL pins) and second DSP (B) is configured as slave (PLL pins).

-. DSP A receives audio signal thru ADC and sends it via TDM8 thru signal thru SDATA_OUT0

"TDM" is enabled in "Serial Output" in "Register Control"
"Master Control is enabled in "Serial Output" in "Register Control"

In the "scheme" I have both channels mixed and sent to ALL channels DAC0 thru DAC3 and DIG0 thru DIG7.

-. DSP B receives TDM signal thru SDATA_IN0. "TDM" is selected in "Serial Input" in "Register Control.

In the "scheme" i am using standard "Input" (from IO --> Input) and selecting channels 2-3 which are usually used for I2S input (Digital input goes thru input 2 to 9 = 8 channels).

Output is configured thru all DAC in the DSP B, but I get no sound, nothing, not even noise.

For TDM interconnect I am using a standard cable with Dupont terminals. It's around 10cm long.

Cheers.

Hi all,
I'm looking for the value of the parts needed on the Accuphase frequency board being used in the F20/25 active crossovers.
Have a 180Hz card but need 250Hz (or 290Hz).
So far by looking at the pictures of the FB-250 card I found:

• C1-C12 120nF (124)
• R1-R8 19.6k 1%
• R9-R10 12k 5%
• R11-R12 960R 5%
• R13-R14 36k 5%
• R15-R16 68k 5%

This is of course by eye so not necessarily correct.
The PCB itself (115-0690-14) and R17-R18 look to be the same across different models.
Attached are a few pictures I of the FB250 I could find on the internet, on one I added the part number for the sake of convenience.

Hi Guys!
I'm excited to present the second episode of my podcast: Twisted Transistor! Vinyl lovers rejoice! This time, Darren Myers of Parasound explains how to design phono preamplifiers. Lots of knowledge, example files and almost 2 hours of content. Get your coffee and some snacks.

Big thank you to Darren for preparing an amazing reference design and explaining everything!
Login to view embedded media

Hello,

this Pioneer SA-9500 amplifier belongs to a friend of mine.
About a year ago he asked me to clean it up and recap if necessary.
OK, did it. - replaced lytics (Wima film caps into signal path, otherwise Panasonic FM/FR), cleaned all switches (disassembled the rocker type ones).
According to RMAA meausrements (from speaker terminals) improvement was noticeable.

In fact, it became too god since now the owner says he can hear hum in the speakers and earphones.
It has been on and off my desk intermittently for several months (no hurry with this) and I have sorted out the earthing wiriing, replaced plain signal wires with shielded ones, bypassed the input buffer, bypassed also on Tone off postition the first stages of control amplifier.
So the signal path from input sockets to power amplifier input is completely passive in Tone OFF mode.

Bought also a Tektronics analogue scope (to join the digital ones I have).

Now to the hum - it seems to be the mains ferquency (50Hz), on RMAA it shows like this:



Looking at the scope (on speaker terminals:

- when power amplifier input is grounded (Power amp input switch is set to "separated") everything looks ok and the owner does not hear hum:



- when power amplifier is connected to the input signal path wiring (and the RCA input socket is grounded) then with voume regulator at minimum position things start to show up:



- when volume knob is turned to max position then it besomes more clear:


Next step would be "walking the signal path" with the scope and grounding it at every following stage but can anybody suggest what could be causing this kind of noise?

Recently, I have obtained some damping diodes, such as 6CL3, 17BH3, etc. They are all half wave rectifier diodes. Although they are very cheap, it seems that I rarely see works that use them in audio circuits. Can I use two 6CL3 to make a full wave rectifier circuit? Alternatively, two 6CL3 can be used instead of the expensive GZ34, which is quite interesting

I’m looking for 24 (!) BMR drivers, ideally 2” / 2.5”. I might consider as an alternative the similarly sized Mark Audio full range drivers if the price was right. From the UK would be ideal but from Europe would also be OK.

I'm on to my next project after fixing an Onkyo receiver that had a bad display - https://www.diyaudio.com/community/threads/onkyo-tx900-display-not-working.405419/

I picked up this ADS Power Plate amp a few months ago and finally had time to put it on the bench and test it.

It powers up, the power light turns green, but doesn't have any output on any speaker output.

So I opened it up and the most obvious thing I see is this destroyed resistor.

I'm still working my way through Perry's tutorial, I have been reading a few pages every night trying to work my way through it finally.

But for now I am assuming that the burned resistor is the same spec as the good one to the right, so I ordered a few 1W 100 Ohm resistors. I will pull the board this weekend and start removing the resistor and also testing the other components nearby.

I'm thinking that the transistor near it has shorted causing too much current through the resistor. So I'm assuming I will need to replace that transistor. There is also a Zener Diode behind the resistor that I need to test and possibly replace. And I ordered some capacitors to replace the two that might have been damaged when the resistor burned.

I'm also guessing it makes sense to replace the components near it that look to be for the other channel? Since I'm in there.

I don't have a schematic for this amp and haven't found one online. There are a few ADS photos in Perry's tutorial but none that match it exactly.

If anyone has any other tips while I keep working through the tutorial and wait for parts I'm all ears! I'm still learning, happy for the help!

Thanks,
Ian

Hello everyone, I'm new to this forum. What inspired you to start building your own audio equipment, and what was your first project?

Trying to hook single ICT driver to a cheap 30w mono class d amp. Amp has 4 terminals - 2 bass and 2 treble. Shown in attached picture.
Could these safely be combined to connect to driver?
Grateful for any advice.

SOLD

This driver currently sells for $759 at USSpeakers: https://www.usspeaker.com/faital pro 18XL1800-1.htm

This well-designed 18" driver with a neo motor has low-distortion and relatively high Xmax and is intended for very low frequency applications (see info link below). It's in perfect condition and has only about 40 hours of listening on it only, as a home audio sub. I purchased it new about a year ago but it took me awhile to build up a box and get the driver mounted.

I unfortunately need to sell it because the cabinet is too large and heavy to move with me. The driver is not all that heavy due to the neo motor and will ship in the original MFG box. If you are in sourthern Michigan and also want the cabinet with local pickup please contact me. Otherwise I will only ship the driver.

Info:
https://audioxpress.com/news/New-18-FaitalPro-18XL1800-Neodymium-Super-Woofer

Specs:
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=201070150

I'm working on a Krell SACD Standard that never transitions from standby to "on" when the power button is pressed. Nothing seems completely out of whack with respect to the voltages coming from the SMPS, but I'll post them later in case I'm missing something. So at this point, I'm wondering if there are any owner (past or present) out there who've experienced this particular problem.

Disney CEO Bob Iger : "Creators lost sight of what their number one objective needed to be... We have to entertain first. It's not about [sending] messages"
I wonder if money will defeat wokism 🙂

I would like to discuss about the first article below and its comments :

Michael Kiwanuka, AudioXpress, June 2017
"Current Feedback and Voltage Feedback Fallacies"
https://www.audioxpress.com/files/attachment/2621

Currently, invalid links :
http://www.waltjung.org/waltsblog/catego...mplifiers/
Some Useful Background Reading on Current Feedback Amplifiers | Walt's Blog 2014

Walt Jung, Sergio Franco, Michael Kiwanuka, AudioXpress, July 2017
"Current Feedback and Voltage Feedback Dispute"
http://www.audioxpress.com/article/curre...ck-dispute

EDIT december 2018. I added links having correlations with the topic :

Christian Henn, Burr-Brown, May 1993
"New Ultra High-Speed Circuit Techniques with Analog ICs"
http://www.ti.com/lit/an/sboa047/sboa047.pdf

E.M.Cherry, IEE Proc/-Circuits Devices Syst; Vol 147, No 6, December 2000
"Feedback amplifier configurations"
https://drive.google.com/file/d/1n030f9Lh8aQe0Hlc45VLJQtzjYJWwLNU/view

Walt Jung and technical staff of Analog Devices, 2005
"Op-amp applications handbook / Current feedback basics"
https://studfiles.net/preview/429636/page:5/

Cyril Mechkov, Technical University of Sofia, Lutz von Wangenheim, discussion started in 2013
What is the truth about the exotic current feedback amplifier? Is it something new or just well known old? Is it really a current feedback device?

Sergio Franco EDN August 23, 2017
"In defense of the current-feedback amplifier"
https://www.edn.com/design/analog/4458753/In-defense-of-the-current-feedback-amplifier

Christopher Paul, AudioXpress, July 2018
"Current Feedback: Fake News or the Real Deal ?"
https://www.audioxpress.com/files/attachment/2660

Hi all,

Really appreciate if someone can explain why is this not working as I want it to.

I need to create a simple delay using RC time delay and MOSFET to switch things on after say 1 second.

I am using sim to see if it works properly, but it gives me very slow rise time. I want it to do instant switch to hi (>2.4V) after 1 second.

Thanks for help!

How do you test an amplifier for DC offset?

Hi Folks,
I'm hoping to build my first diy loudspeaker, and thought it a good plan to though out some ideas to you guys, if you kindly had any thoughts on them.

I've a lot of wood work diy experience, good workshop, a fair understanding of the physics in building a new a pair of audiophile speakers.

Also the wife is on board.

Brief plan -
1. 3 way, compact, say 40L to 70 L (depending. It the woofer) standmout.
2. Ported and flared (downwards) , stepped baffle, non-online driver arrangement.
3. 25-25mm ply, braced with a rear midrange chamber (may be ported), and the box no higher than 800mm.
4. Box width deeper than wide (probably should be the other way round).
5. Woofer SA Satori W024 P-08.
6. Mid - Scan Speak 15W8434 G00.
7. Tweeter - Scan Speak Discovery D2608/913000.
8. Simple 1 to 2 order crossover (depending on the test results).
9. Magnetic front grilles with a double baffle, all chamfered.

What do you think?
Many thanks in advanced
Fradbut

Hoping that I might get some help with my Luxman DZ-112 CD player which has trouble reading discs. When I first got it, I didn't think it sounded that special, but some op amp and capacitor upgrades in the audio section turned it into my favorite sounding CD player. Those PCM1701s DACs sound pretty nice, and I think that the Luxman's +/-12V analog rails contribute to a more open sound than my two Sonys, which both use 5V rails. Consequently, I'd like to get it working reliably.

I'm not sure if there is an electrical or mechanical problem, or if it just needs proper adjustment of the trimpots. The player was prone to skipping with a light tap when I got it. I've set the VCO and Focus Bias according to the service manual (so at least two of the trimpots should be set correctly), but have found no combination of trimpot settings that will make the player read discs reliably.

Chirpy DZ-112: https://youtu.be/h4uvFJ1E-cY

When playing a CD, it starts "chirping" away endlessly, without reading the TOC (as shown in the video). By sweeping the Tracking Error trimpot, I can usually "trick" it into reading the TOC and playing the disc. Once playing, it will usually keep going, even with CD-Rs. I can find a null "sweet spot" when adjusting Tracking Error which will usually allow the player to continue to read that particular CD, but the player will usually go back to endless "chirping" when a different disc is inserted. Perplexingly, there doesn't seem to be any combination of the three remaining trimpots (Tracking Error, Focus Gain, Tracking Gain) that will make it read and play a variety of CDs every time (without messing with the Tracking Error trimpot).

In the service manual, it says to adjust the Tracking Error trimpot so that there is 0V +/-10mV at TP5 (service manual says TP6, which is an error, corrected in the DZ-122 manual). However, I measure roughly 90mV at TP5, and am unable to get to 0V no matter how the other trimpots are adjusted. Not sure if this is a sign of a component failure or??? This player was made in 1989, so it is possible that some of the electrolytics might have failed, though I see no obvious signs. I replaced four of the 22µF caps in the servo section, but observed no change. Not sure where else to look.

Wondering if any of you have an idea what might be going on and what I might try next for a solution? Hoping that this "chirping" phenomenon might point to an obvious component or failure point.

Thanks!

Hello guys, I made a PCB for the signal tracer project made originally by Rod Elliott (ESP). He should be here in the forum, but for some reason I cannot tag him.
This is his originally project:
https://sound-au.com/project164.htm



I swapped the 9V battery with a DC connector to have the power supply outside the circuit.

Initially, I wanted to use 18650/C123A/AAA/AAAA batteries, but everything considered they would be too bulky.
As the OG project, you connect a BNC probe as input, and you can listen to the amplified signal (around 1W), to an external speaker, if you like, you could also use headphones, but it is a bit more dangerous for the high volume.

You also got a volume pot, a 20x switch gain, an attenuator 1x/10x/100x and a power switch.

The speaker is connected with a stereo 6.3 mm jack.
I used a stereo jack because on LCSC store a mono version wasn't available.
I want to use LCSC because I would like to have the PCB assembled .


This is my first time using SMD components, I tried to use them when possible to save a bit of space on the PCB.

I wanted to do the same also with the lm386 and j113, but if I read correctly the datasheet, the SMD versions are a bit less powerful than THO versions.

I tried to leave a bit more space on the C1/R1/R2/R3/R4 components because I read that if you use the probe on the HV sections those parts could conduct high voltage, I left around 0.8 mm per trace, I could do it everywhere but on the attenuator switch, I don't know if this could cause a problem.

This is the schema of the project, I think I did everything right, but could you take a last look just to be sure??

You can find all the documentation to build the project here:
https://oshwlab.com/gagliarducci.antonio/signal-tracer

I'm new to DIYaudio, so I hope I'm posting on the right place.

My omni-directional Modmic quit working and I was hoping to repair it by simply matching the mic capsule inside. However, opening it up revealed a mic capsule with absolutely no markings, and I have been unable to find any details on the Modmic to allow comparison for replacement.

I haven't checked the mute switch to see if it is the failure point yet since I will likely destroy the plastic in attempting to open it. I wanted to replace the capsule first subs it would be the easiest fix.

Any recommendations on what I should look for, or where I should look for a replacement capsule?

Thanks,

Tony

My 1st mosfet amplifier i built in ltspice.

I bought a budget soundbar because my LG smart tv has speakers pointing backwards and the sound is becoming increasingly bass heavy(to my ears). I thought an HDMI soundbar might have a brighter presentation.

I was wrong!. The soundbar has all inputs and the sound is bass heavy on all of them, and at times quite boomy. There is no tone control so I wonder if anybody has any experience of applying some kind of filter to reduce the bass.

when the TV is using the in-built speakers there is an eq control in the menu. This control disappears when using sound over hdmi.

Hey!
I've an issue with my LM1876, the gain is less or equal to one, I've been searching around for 2 days now and I just can't find the problem!

Mute and Standby pins are connected to ground and I'm only showing channel A in my schematic. Standby and Mute were left floating before and I had the same problem. I did change the values for feedback to set the gain higher but no matter what I do the output is low.

I did put in all the components shown in "Auxiliary Amplifier Application Circuit" in the datasheet except the 10R and 0.7 uf inductor and still had the same low gain. Am I missing something?

Supply is +-18 from a toroidal transformer (170VA) with CT and signal is coming from a phone if that matters.

I have for sale toroid transfomer (1x) 500VA, 1x230Vac primary and 4x35Vac secondary voltages. It is special audio version with lower flux in ferrite core (less mechanical noise). Dimensions are 140x70 mm. Weight is 4,9 kg.

Price is: SOLD

PM for details.

I have for sale very nice aluminium chassis, made for power amplifier. Heatsinks are Fischer SK56 90mm high. Back, bottom and top plates are made of 3mm aluminium. Front plate is also made from aluminium and it is 10 mm thick. Hole for push button was made on CNC. All plates are powder coated in half shine black colour, so chassis looks top notch. Dimension (external) are 330x310x110 mm (WxDxH), internal 250x297x83 mm. On bottom of chassis is special reinforced U profile plate, that could support heavy toroid transformer (plate is 130 mm width). U profile plate is screwed into front and back plate, so there is no sag of bottom plate, due weight of heavy transfomer. There are M3 CNC machined holes on heatsink for Holton R4.2 amplifier and regulated power supply. Weight of chassis is 5,6 kg. You will have hard way to get nicer looking chassis everywhere on web.

Price include chassis, 2 Neutrik XLR sockets, two speaker terminals, IEC inlet, 20A power switch and blue LED push button.

Price for all above is: SOLD