Quantcast
Channel: diyAudio
Viewing all 93447 articles
Browse latest View live
↧

Dirty power and no ground, only a waterpipe.

July 11, 2018, 7:42 pm
$
0
0
I live in a city with the dirtiest power. lines are a mess! switching adapters everywhere. When making a linear power supply for a dac or a 2w amp, should I filter before and after the trafo? I have a load of old (discharged all caps already) power spplies with chokes and many ac, picofarad, yellow plastic caps, etc...

Any of that worth reusing?



Is it important to filter before the trafo as well as after?


Can I possibly clean this power without a ground terminal or will I need to use a waterpipe for ground?


Any designs for a power supply which could clean this power of 5v-12v without a working ground terminal on the plug?
landlords in this city do not wire the ground terminal on the plugs!


Should I just use batteries? (18650s)





I need 5v and 12v right now.


Thanks


Philip


"I'm gonna filter this dirty power and get rid of the NOISE somehow"
↧
Search

who can make a flat pack for Alpair 10.3 ?

July 11, 2018, 8:16 pm
$
0
0
Hi, I'm looking to make this design for the Alpair 10.3

"Erich's Hartmann's bookshelf box"

which can be found here
Alpair 10 Gold | Markaudio

I don't have the tools / space / expertise to make it myself so I'd like to hopefully but a flact pack of it premade.

can anyone point me to where I could obtain one ?

Thanks
↧
↧

Cheap as Chips OPA1688 Low-THD Muscle Amp

July 11, 2018, 8:30 pm
$
0
0
I normally make discrete SE Class A amps, but I have found that the OPA1688 sounds quite nice. This project started out in this thread, where I explored using a single OPA1688 with an output cap coupler to reduce the complexities of active PSU rail shut-off to prevent DC imbalance on the headphone outputs. I hand-etched a simple single OPA1688 and gave it a non-polar output cap bank and it sounds very nice. Of course, there is global feedback and it is not Class A. But it there is something nice about the simplicity and low power consumption for 9v battery use. So it got me to thinking of how to boost the output power by paralleling the OPA1688. These are capable of 75mA current drive and can handle rails up to +/-18v. Here is the single OPA1688 amp that I built:
Click the image to open in full size.

Click the image to open in full size.

The OPA1688, is not your typical LTP input stage opamp as the measurements show that it has a dominant H2 (second harmonic character with monotonically decreasing higher orders). Here is 2vpp into 47ohms:
Click the image to open in full size.

Internally, the OAP1688's are a 3-stage amp design and capable of remarkable performance. The circuit uses the much-liked LME49720 as the voltage amp stage with the OPA1688 as a power buffer and the global feedback loop is from the output of the summed buffers back to the voltage amp. Load balancing 1R resistors are used at the output of the buffers and 220R summation resistors are used at the inputs to the buffers. With 6 buffers, this will require three dual OPA1688IDR IC's. With SOIC8 package and full use of SMT parts where possible, the total footprint can be quire small. A total of 6 x OPA1366's will be needed with a single dual channel LME49720 for the voltage amp stage. The cost of the 7 chips is about $10 and will produce an amp capable of about 1.3wrms into 50ohms and maybe 3.5wrms into 16ohms. All at exceedingly low THD levels. I modeled it LTSpice with the following schematic:
Click the image to open in full size.

Here is the predicted FFT for 2vpp into 50ohms:
Click the image to open in full size.

The Fourier components and THD are way down there in the noise.
Quote:
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 1.001e+00 1.000e+00 -0.03° 0.00°
2 2.000e+03 7.524e-09 7.513e-09 -24.92° -24.89°
3 3.000e+03 8.023e-08 8.012e-08 -89.87° -89.84°
4 4.000e+03 1.141e-09 1.139e-09 -40.43° -40.40°
5 5.000e+03 9.318e-10 9.305e-10 -8.94° -8.90°
6 6.000e+03 1.251e-09 1.249e-09 -18.57° -18.54°
7 7.000e+03 1.290e-09 1.289e-09 -0.13° -0.10°
8 8.000e+03 1.568e-09 1.566e-09 -10.49° -10.46°
9 9.000e+03 1.659e-09 1.656e-09 -0.22° -0.19°
Total Harmonic Distortion: 0.000008%(0.000000%)
Here is the predicted frequency response and phase for the above case:
Click the image to open in full size.

Here is the FFT for 8vpp into 50ohms:
Click the image to open in full size.

And the corresponding Fourier components and THD:
Quote:
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 4.006e+00 1.000e+00 -0.03° 0.00°
2 2.000e+03 9.238e-08 2.306e-08 -8.09° -8.06°
3 3.000e+03 4.755e-06 1.187e-06 -90.26° -90.22°
4 4.000e+03 7.334e-09 1.831e-09 -24.03° -24.00°
5 5.000e+03 1.277e-07 3.189e-08 -89.48° -89.45°
6 6.000e+03 3.201e-09 7.992e-10 -29.19° -29.16°
7 7.000e+03 4.595e-09 1.147e-09 -54.64° -54.61°
8 8.000e+03 3.582e-09 8.941e-10 -17.89° -17.86°
9 9.000e+03 3.472e-09 8.668e-10 -1.11° -1.08°
Total Harmonic Distortion: 0.000119%(0.000000%)
So now, just need to build a prototype and test it.

↧

lingDAC - cost effective RBCD multibit DAC design

July 11, 2018, 9:08 pm
$
0
0
I've been working on DAC designs using TDA1387 for several years now, both in helping modify existing designs and coming up with my own solutions.

'lingDAC' has satisfied me in listening to such an extent that I feel its worth sharing the whole design here as I feel I'm close to reaching the end of the road with what's possible when beginning with the TDA1387 (famous last words!).

A few bullet points to introduce this DAC :
  1. designed for Red Book CD source material hence 16bits and 44k1
  2. no-oversampling design means no digital filter is used
  3. a steep analog filter is used instead of the digital filter to kill images
  4. the design is aimed at reaching the best SQ, not best measurements
  5. lowest possible BOM cost commensurate with still sounding good
  6. designed as a board stack for maximum DIY flexibility, boards are 5*5cm

I need to tidy up the schematics before posting them, I'll add them to this post as they're rendered presentable.


Returning later I see I'm told I'm unable to add attachments to this post so guess new info will go into subsequent posts.
↧

Oscillating Marshall clone

July 11, 2018, 10:46 pm
$
0
0
Hiya all,

I am helping a friend to build a Marshall 2204 clone and while everything has gone relatively smoothly thus far, yesterday we ran into trouble.

The build is essentially finished and we already tried it out successfully couple of weks ago: everything worked fine and the sound was great.

Now my friend wanted to add some led lighting for the front panel, so we built a simple diode rectifer based on this article, drawing power from the tube heater. Unfortunately, there was a short circuit (legs of two capacitors touched) and a bit of smoke emanated from the rectifier. But we acted pretty swiftly, the amp was on only for few seconds and we turned it off immediately when we saw the smoke.

However, after the incident the amp has started to oscillate. Depending on the speaker (my friend has a couple of drivers at hand) the noise either a high-pitched squeal or a low rumble. Normal guitar signal is coming through and the oscillation is not affected by the master volume.

The oscillation stops, when we drop the bias to about 15mA (the correct value at 60% dissipation is about 35mA), but enything above that and it starts again.

There is one more piece of info: we have implemented a half-power switch (we have been using this Ceriatone layout for our project) and the oscillation only appears with full power mode. When the switch is set at half power, everything is working fine.

So all this leads me thinking that the probem lies with the screen grids of the power tubes. Could one or both tubes have been damaged during the rectifier debacle? Would new pair of tubes fix this issue or is there something else we should check out?
↧
↧

Fever 6J1 pre-amp max input voltage ?

July 12, 2018, 12:03 am
$
0
0
hey guys i need somebody more experienced than i am on these 6j1tube pre-amps.. my transformer is 15v ac but the pre-amps input is 12v.. no max listed..can i get away with 15v ac instead of 12v ac? this way i dont have to drop the voltage or add a reg, or converter etc. i appreciate anyone that has one and can answer this for me.. :eek:

much regards, Harris
↧

Hello to fellow audio fanatics!

July 12, 2018, 12:25 am
$
0
0
Hi guys and probably some gals.


I've been interested in audio stuff for as long as I can remember. Built my first speakers out of cardboard when I was 7 years old and finished my first proper tube amp in early 20's.


I'm mainly focused on stuff from 80's and 90's era. Both mobile and home audio.
I usually buy broken gear and then do my best to restore it to full glory.
I personally can't stand the stuff that comes out of factories these days. But to each it's own, I don't judge.


Location: Northern Europe
↧

Okto DAC8 - a high-performance, 8-channel D/A module with Sabre ES9028PRO

July 12, 2018, 12:42 am
$
0
0
Hello everyone,

It's our pleasure to present to you OKTO DAC8, an 8-channel D/A module. Based on numerous prototypes with different I/V stages and many, many hours of PCB design and testing with R&S UPV audio analyzer, DAC8 is made to excel as a part of multi-way or multi-channel reproduction chain.

All the features, measurements and documentation can be found on our website: Okto Research.

Key features:
  • Up to 384kHz I2S, DSD256, DSD128 over PCM or 96kHz SPDIF input
  • Measured -124dB (0.000063%) THD / -117dB (0.00013%) THD+N analog output performance
  • 8 analog stages with fully differential OPA1632 op amps, analog outputs accessible on onboard XLR connectors and 0.1" pin headers
  • Access to ES9028PRO's 32-bit internal volume control with a potentiometer thanks to onboard MCU, direct access to control registers via I2C
  • Headphone amplifier capable of delivering 100 mW into 32 ohm load with -116dB (0.00016%) THD
  • Highly optimized 4-layer PCB design with attention to RFI immunity (cannot stress out enough how small loop area and short traces are important for clean output spectrum without high-order spuriae!)
Typical applications:
  • As a part of hardware-based digital crossover together with MiniSHARC, FreeDSP or any other DSP module with digital (I2S or DSD) output
  • As a part of software-based digital crossover like 64-bit DSP engine in JRiver and any USB>I2S module like USBStreamer or DIYinhk Multichannel
  • As a standalone 8-channel DAC for multichannel playback paired with any of the aforementioned USB>I2S module
  • As a stereo preamplifier and/or headphone amplifier future-proofed by 6 extra channels
Price for July orders is 429 EUR, later it will be 489 EUR. OKTO DAC8 only comes fully assembled and tested due to high number of difficult-to-solder parts.

Thank you,
Okto Research

Attached Images
File Type: jpg Dac8_4.jpg (213.5 KB)
File Type: png OktoDAC8_bal_thd_1kHz_1.png (27.5 KB)
File Type: png OktoDAC8_bal_imd_18+19kHz.png (23.7 KB)
Attached Files
File Type: pdf OKTO DAC8 Measurement Protocol.pdf (422.9 KB)
File Type: pdf OKTO DAC8 Module User Manual.pdf (709.6 KB)
↧
Search

Preamp PSU burned caps! Suggestions?

July 12, 2018, 1:05 am
$
0
0
Hey guys,

It's been a long time since i've been reading the forum (YEARS!!!) and never posted, but I really need a specific help.

Last week my preamp (Audient ASP880) just started to behave very weird and I opened it to inspect... Just found that the TOP256YN was burned and together a few electrolytic caps (and maybe 2 resistors).

I've been in touch with Audient support since they don't have service available here in Brazil. So, I'm taking the adventure with my basic electronics knowledge... So far so good...

I have someone coming from the states that can bring parts to me, so I got to Mouser and after a lot of research I started choosing the parts to replace, paying attention to the caps size, dimensions, etc... all the specs...

Then I thought well, maybe I can do kind of an upgrade to it, since the PSU was built with very "not famous branded" components... And I know, it would be impossible for them to use 40U$ in caps for the PSU and keep the unit with the price it is (U$1400)...

So getting to the point:

1) I'd like to know if it's a good choice to replace all the electrolytics with Panasonic FM and FC series. If yes, than I'm done... It's everything added to the cart! haha

2) Suggestions about the resistors to change? Brand, rating... couldn't figure out the power rating... and for me it looks like 4.1K... very unusual, isn't it? (pics attached)



Thanks very much!!

Attached Images
File Type: jpg IMG_20180712_050157793.jpg (593.1 KB)
File Type: jpg IMG_20180711_131251847.jpg (826.1 KB)
↧
↧

Network to AES/EBU transport (aka Feeding The Ones)

July 12, 2018, 2:24 am
$
0
0
My current setup is: streaming Spotify (but switching to a high res streaming service soon) from a noisy DELL laptop USB port > Yellowtec PUC2 Lite AES/EBU converter > Genelec 8351a "The Ones" active speakers (these only have AES/EBU in). I am looking to get rid of the noisy laptop and optimise sound quality along the way, with best value for money.

My ideal is a tiny board/device with a decent ethernet port, some memory to run Volumio, and a AES/EBU digital output - because in my view, the fewer ports, cables, and potential interferences in the system, the better. After a week or so of ploughing through the internet, despite the deluge of options and DIY projects available, it appears that *no such thing exists*.

From my research, it seems that the second best option then is the pi2design 502DAC HAT on a RPi board via I2S. This HAT has an AES/EBU output, although still contains a (for me) superfluous DAC chip. Also, it's a niche device with only sporadically some units becoming available. They are currently out of stock.

Third best option: a USB network transport, e.g. Allo USBridge or Volumio Mini86, or a OrangePi (with ethernet & USB on separate bus), that feeds the Yellowtec Puc. I don't think this is ideal, unless someone can convince me that the USBridge or Mini86 do something useful to the signal e.g. with improved clocks and isolated components.

My questions are: am I missing any options? Is my current hierarchy of options correct?

Many thanks for sharing thoughts :)
↧

BPA300 Build

July 12, 2018, 3:23 am
$
0
0
Hi Folks,

I recently bought four of these fellas...

Assembled LM3886 X3 in Parallel 150W Pure DC Mono Power Amplifier Board HIFI | eBay


... and I am interested in building something very similar to the BPA300 by Alex.

I'll hold my hands up an admit here that I am a complete novice to the DIY audio stuff and don't really understand what I am doing. I have dabbling with electronics for the last few years and working with things like RPi and Moteino to build some home automation stuff, so whilst I have a decent basic understanding of electronics at this stage this is quite a radical departure and I will need a lot of hand holding if people are willing to help. I do learn quickly as long as small words and visual aids are used. lol.

Looking at the build information on shine7 the design and construction of this setup appears to be fairly straightforward and I assume the board I have bought from ebay is a close derivative of the PA150 design, it certainly appears to be.

What I am curious about is the power amp setup used in the BPA300 seems quite different from what is used in other gainclone builds, where exactly is the rectification taking place in his setup. I am probably missing something obvious but would like to understand it better.

Best regards, Peter.
↧

Which turntable to buy ?

July 12, 2018, 4:51 am
$
0
0
I am an entry level user who just happened to discover a box of 33 1/3 albums.
So, I am shopping for a turn table and have settled on a Rega.
However the price of the Planar 1 + the performance upgrade package ($670) is virtually the same as a Planar 2 ($675).
So what to do ?

Thanks
↧

Teensy Audio Bridge for I2C/I2S lines

July 12, 2018, 5:33 am
$
0
0
Hello,

I'm working on a digital audio mixer for pro live mixing. I've been researching this for years but recently stumbled on the Teensy 3.6. It has a very nice library for creating an audio flow using a GUI and Arduino code. Check out the Teensy Audio Library here.

My first test was using the Audio Shield and it succeeded at proving that it is capable of doing what I needed, but the quality was pretty bad. So I purchased some cheap modules off ebay. They are a PCM5102A and a PCM1808. I successfully connected them to the Teensy. They worked great and the sound was much better.

Next, I plan on integrating some even better IC's for my project but before I do I was thinking about creating some type of audio bridge for the Teensy. This would make it easier for me to modularize my project and focus on the individual components rather than a full blown board. The plan is to hopefully get some community support. I've outlined the concept on my post about my project on the teensy forum. Check it out and let me know your thoughts. I'm seeking just an overall concept confirmation and maybe some advice on what features should and shouldn't be included on it.

Here is the link to my project and some more information about this potential bridge.
Teensy with PCM5102a Module via I2S

Click the image to open in full size.
↧
↧

Clone a Soldano SLO100

July 12, 2018, 6:19 am
$
0
0
Hi
I am about to build a Soldano SLO100 replica. I have everything, but the layout. My main issue is about the ground. This is a high gain dual channel amplifier, and if I start to mess around with the ground.

Usually, this is what I do

- Ground star 1: very close to the power plug to connect the ground cable
- Ground star 2: close to the input jack. From there I connect a bare cable that goes all the way on top of the POT. Every single ground from the preamp is connected there
- Ground star 3: close to the Power Supply. I put another bare cable that goes from the power supply to the power amp. Here I connect the power amp ground, Power Supply ground and center taps
- I also use blinded cables for the signals coming from the Input Jack and Master Volume.

So far, this works properly in every amp that I made (from 5W to 50W mostly with clean tone and some effects like Reverb and Tremolo). I got a super low hum, and everyone is happy with the tone.

The thing is that after reading the article that I attached about Grounding, I realized that I might introduced some ground loops in my circuit.

So I would like to know if anyone has some pictures from the layout of a real Soldano. I think this would be the best reference to take

Thank everyone

Attached Files
File Type: pdf Grounding.pdf (610.7 KB)
File Type: pdf slo-100_0_7.pdf (152.3 KB)
File Type: pdf slo-100_psu_0_8.pdf (80.7 KB)
↧

Soundstream DA-1 Repair Info

July 12, 2018, 6:23 am
$
0
0
I've got a Soundstream DA-1 that arrived quite literally as a basket case. Everything seems to be here, including two sets of amplifier boards. One Rev A, the other Rev B.

The Rev B boards are heavily damaged and have a lot of component substitutions and additions. Components are different between the two boards. Since I have no schematic to determine what should be there, I've set them aside for now.

The Rev A boards are in good shape and look to have mostly original components. I replaced the failed components on one board and brought it up on a lab power supply. It seemed to work fine. Bias and DC offset were adjustable but high. Bias (as measured across one of the emitter resistors) couldn't be adjusted below about 20mv. DC offset would vary all over the map as I twisted the POT (a new one by the way). It won't adjust below about 40 mv. Feeling pretty good about things, I put it back in the chassis and powered it up. Things seemed OK. I did a load test and suddenly smoke began rising from one of the emitter resistors and a fuse blew. Two output transistors had shorted under load.

Questions:
1. I've looked high and low for a schematic and failed. Anybody got one?
2. Any idea what the bias and DC offset should be and how it should be measured?
3. Any theories as to why it died under load? I have two guesses - counterfeit transistors or perhaps bias was too high.

And an interesting note. This amp board seemed to be very prone to go into oscillation. When running it outside the chassis on the lab supply, it would easily oscillate until I added the Zobel filter at the output. The filter is on the binding posts in the chassis, so when running the board out of the chassis I had to add it to prevent problems.

Thanks.
↧
Search

QSC MX3000a power supply repair

July 12, 2018, 6:24 am
$
0
0
Servicing a QSC MX3000a with one side of the two dual power supplies out. My real question is procedure to remove the main board. It's not clear from looking to proceed with or without large heatsink. PS, Service manual not available from QSC factory. Link posted previously here to schematic on QSC site is dead.
↧

Hivi domes

July 12, 2018, 8:14 am
$
0
0
Hi all, just wanted to point out to nice dome midrange and dome tweeter combo from Hivi. I have seen pair for $59 on ebay, so I bought it. Mainly because I love domes. I got plenty projects done in the past with old Philips domes, lately with Dayton domes, all good sounding. Frankly I do not understand why dome mids are not used more often.
Here is the measurement I obtained, just slapped on its styrofoam transport box. 30uF and 3 uF caps used for measurements, no coils.
Now I just need to find nice 8-10" midbass to mate it with.
Cheers!

Attached Images
File Type: jpg hivi1.jpg (459.0 KB)
File Type: jpg hivi2.jpg (528.7 KB)
File Type: jpg hivi4.jpg (130.1 KB)
↧
↧

Best Build For a Novice

July 12, 2018, 9:44 am
$
0
0
Hi All,
I've never built an amp before, but I'm an avid DIYer and I'd like to give it a shot. The range of high-quality sound amplifiers I've listened to is exactly 0, so I don't imagine I'll find myself particularly picky when it comes to sound quality. Ideally I'd like to build something with <0.1% THD at 50W with at least 105 dB SNR, and I'd like to build something that beats the Dayton APA150 in price for parts, ignoring time engagement, since that's part of the fun, after all!

Hit me with your best suggestions, I'm all ears
↧

Voice Kraft 12" inch

July 12, 2018, 10:03 am
$
0
0
Hello,

I'm working on a box for Voice Kraft GDN 30/80 12" inch subwoofer. Parameters: Fs 25 Hz / Qms 2.47 / Qes 0.3 / Qts 0.26 / Vas 270 liters / Bl 13 Tm / Mms 50g / Cms 0.000819 m/N / RMS 80W.

Trying to make 6th order bandpass:

1) 75 liters @ 29hz with 90 sq.cm port 34 cm lenght and 30 liters @ 76 Hz 120 sq.cm port 13 cm lenght.
2) 90 liters @ 29hz with 90 sq.cm port 28 cm lenght and 35 liters @ 72 Hz 120 sq.cm port 11 cm lenght.

However i'm not sure how 6th order bandpass is going to sound. So as alternative Bass reflex box is also a good option:

1) 75 liters @ 37 Hz with 90 sq.port 19 cm lenght.
2) 100 liters @ 35 Hz with 90 sq.port 15 cm lenght.

I would like to get some help and knowledge which box should I use and what should I change to make them better.

Attached Images
File Type: jpg 7530_2970.jpg (130.4 KB)
File Type: jpg 9035_2972.jpg (129.6 KB)
File Type: jpg 75_100.jpg (134.1 KB)
↧

Altec 1612A limiter-amplifier

July 12, 2018, 10:32 am
$
0
0
Can anyone provide info on setting trim pots on an Altec 1612A limiter-amplifier, and or theory of operation?
↧
Viewing all 93447 articles
Browse latest View live
Search