Jump to content

DIY audio: what are you building?


Recommended Posts

50 minutes ago, betocool said:

I stepped back for a sec, took a breather, and decided to connect the signal input GND at the RCA terminals directly to the chassis (ie, earth). And that did it. All noise and buzzes went away, to the point where the noise levels are similar to the amp's internal phono stage. And that's how I decided to leave it.

 

Well that's how it should be done anyway.

 

Well done in getting it working - great project !!!

Link to post
Share on other sites
  • Replies 6.4k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Stereo Subs & Two Way Monitor Build   It’s been slow going on my two way monitor with stereo sub build but I’ve finally finished finished one of the two subs!!!   The subs are 10inch CSS drive

Thanks Pete Sure! Pretty much just used common spray acrylics (cans) for the whole job. Not shy of using 2k but just trying to save on costs.  After the cabs where routed i gave th

Finally got around to my two way active build which is been on back burner for 18 months now.  Construction is 1 inch MDF with lead lining and butyl. Front baffle nearly 2 inches thick. The speak

Posted Images

24 minutes ago, aussievintage said:

 

Well that's how it should be done anyway.

 

Well done in getting it working - great project !!!

I've read in multiple places that you should have one , and only one, connection from GND to chassis in a system, to avoid ground loops. Other time's I've had great results with a fully floating ground (no connection) or weakly coupled (caps and resistors). But then again, I'm pretty sure PC's and other equipment do have a GND to chassis connection.

 

As long as it's safe (it is) and works (it does), I'm pretty happy. It was a fun project, and makes for good listening!

 

Cheers,

 

Alberto

Link to post
Share on other sites
58 minutes ago, betocool said:

Other time's I've had great results with a fully floating ground (no connection) or weakly coupled (caps and resistors).

In this instance, the aluminium foil is your shield.  It cannot do that job if not properly grounded.

Link to post
Share on other sites
  • 2 weeks later...

An interesting observation and consideration when making preamp which use low gain tubes or low power power tubes is the gain. Sounds obvious but until you compare a preamp with a high gain tube like a 12AX7 or 6SN7 it may not seem a consideration. 

 

With the four preamp I made with high gain tubes a two step volume increase, with my 24 step stepper pot, would give a noticeable increase in volume. Let’s say 2db. But with my 71A  1920s tube based preamp I have to make four steps (four clicks) to get near the same increase or decrease in volume. Two clicks almost has no effect. 
 

Though low in gain there is just enough drive and gain to get full power out of any of the powers amps, SS or tube.  I just have to keep in mind I have to make big adjustments on the volume knob to get the level I want. Thank the audio God the preamp sounds so good. And maybe that’s because I’m using a low power DHT to do the pre work.

 

https://retro-thermionic.blogspot.com/2020/04/mwh-1920s-ux-171a-tube-preamp.html

 

Link to post
Share on other sites


These have been sitting in the da lab for years. Only a few hours of use. Such a shame to have such nice matched tubes (Psvane 12AU7 T series MKII gold pin) unused and not playing music. 
 

I have all the parts. Time to make a SRPP preamp with these fine specimens. 

B0657165-D871-41A0-B5D0-30E91198B552.jpeg

Link to post
Share on other sites

 

On 13/09/2020 at 1:34 PM, betocool said:

I stepped back for a sec, took a breather, and decided to connect the signal input GND at the RCA terminals directly to the chassis (ie, earth). And that did it. All noise and buzzes went away, to the point where the noise levels are similar to the amp's internal phono stage. And that's how I decided to leave it.

 

Cheers,

 

Alberto

 

On 13/09/2020 at 2:25 PM, aussievintage said:

 

Well that's how it should be done anyway.

 

 

Alberto may well have solved his noise problem by connecting signal ground to mains earth, via the chassis earthing bolt.

 

However, I would disagree that "that's how it should be done anyway ".  I generally keep signal ground away from mains ground in anything I build - and rarely get any unwanted noise.  If I do, connecting signal ground to chassis via a 10 ohm resistor solves the noise problem.

 

Andy

 

 

Link to post
Share on other sites
31 minutes ago, andyr said:

However, I would disagree that "that's how it should be done anyway ".

Back to basics Andy.  I was simply saying shields need to be grounded.  You choose where...

Link to post
Share on other sites


2 hours ago, aussievintage said:

Back to basics Andy.  I was simply saying shields need to be grounded.  You choose where...

 

Well, to my way of thinking , "the way this should be done "is as follows (you can extend the concept to balanced interconnects, if you want):

  • of course shields need to be grounded (to work!).
  • earth tags on the input RCAs connects to PCB signal ground - or a signal ground point in a ptp wiring situation.
  • PCB signal ground connects to output RCAs.
  • in this way, signal ground is daisy-chained along the line of components.

If you don't do it this way - but instead connect your RCA earth tags to the chassis - then you will have multiple earth connections in your system as, for safety's sake, each (metal) case should be earthed if it has a 3-wire power cord.  Multiple mains-earth connections cause ground loops.

 

Andy

 

Link to post
Share on other sites
2 minutes ago, andyr said:

of course shields need to be grounded (to work!).

that's all folks  - all the rest is specifics to the case in point, and not necessarily correct.  For example, a case can be one big single point ground. There's nearly  always more than one way to go about it.

Link to post
Share on other sites
2 hours ago, Red MacKay said:

What is the purpose of a 10R resistor here Andy.

 

Ta, Red.

 

I'm not sure of the exact reason, Red, but that's what I was told by an amp designer friend of mine.

 

AIUI, it means that signal ground is just lifted slightly, from chassis ground (as chassis ground is mains-earthed, if a metal chassis is used).  This prevents (or at least, attenuates) noise on mains earth from getting into signal earth.

 

Works for the stuff I  build, anyway!  :)

 

Andy

 

Link to post
Share on other sites


21 minutes ago, crtexcnndrm99 said:

From Russia with love.

 

Looking forward to putting these into my phono stage soon (scissors in the corner for scale :D )
 

7FD5164F-77F8-4259-A001-F8C811B46716.thumb.jpeg.41b95d20eca506def535bb33b73b5f45.jpeg

Teflon? 

Link to post
Share on other sites
34 minutes ago, crtexcnndrm99 said:

Yep, the larger ones are, ‘FT-3’

Used these before and the others (PIO). Both with really excellent results. And often such a cheap purchase. 

Link to post
Share on other sites
24 minutes ago, mwhouston said:

Used these before and the others (PIO). Both with really excellent results. And often such a cheap purchase. 

That’s pleasing to hear. Yup couldn’t buy half a mundorf silver at this size for this price.

 

Have an obbligato film cap coming for the psu, but didn’t have the budget to replace all 5 filter caps at once. Will have to decide which position to replace first.

Link to post
Share on other sites


Aussie post finally got around to delivering my Uwe Beis Analogue to Digital converter kit that @andyr uses.  Runs up to 96kHz Optical and 192kHz Coax.

Busy circuit board but straightforward build with no complications on the way through.  Haven't had a kit before where the resistor leads were bent to the board spacing and cut to length!  On early listening it sounds great with just a standard 12 Volt wall wart.

I built it using the standard set up which is based on a 2 Volt peak input signal, but my cartridge / preamp combo (not adjustable) over drives it just a little.  The peak signal can be adjusted by changing two sets of resistors (4 in each set) so have started that process.  Getting the 8 resistors out was a little fiddly - made easier by the silicone tube on the solder sucker tip..  Quick trip out tomorrow to get new set.

Planning to 3D print it a case and line with copper.

Gibbo 

KIt.jpg

Finished.jpg

Upgrade.jpg

Link to post
Share on other sites
33 minutes ago, gibbo9000 said:

 

Aussie post finally got around to delivering my Uwe Beis Analogue to Digital converter kit that @andyr uses.  Runs up to 96kHz Optical and 192kHz Coax.

Busy circuit board but straightforward build with no complications on the way through.  Haven't had a kit before where the resistor leads were bent to the board spacing and cut to length!  On early listening it sounds great with just a standard 12 Volt wall wart.

 

I built it using the standard set up which is based on a 2 Volt peak input signal, but my cartridge / preamp combo (not adjustable) over drives it just a little.  The peak signal can be adjusted by changing two sets of resistors (4 in each set) so have started that process.  Getting the 8 resistors out was a little fiddly - made easier by the silicone tube on the solder sucker tip..  Quick trip out tomorrow to get new set.

 

Planning to 3D print it a case and line with copper.

Gibbo 

 

 

Great, David.  :thumb:  You will not be disappointed.

 

I run mine at 96kHz using a coax output.

 

Interesting that your phono stage overdrives it - at 2v.  I don't remember adjusting the peak signal down ... but my phono stage certainly doesn't output anywhere near 2v but - every now and again, on a transient - the red 'overdrive LED' flicks on.  "Every now and again ", to me, means I have the gain set perfectly.  :)

 

I would suggest changing over the 12v wall wart to a 12v LPS, though.  I use an Sbooster - but a Gieseler LPS would do a good job, too.  :)

 

Andy

 

Link to post
Share on other sites
14 minutes ago, andyr said:

Interesting that your phono stage overdrives it - at 2v

Thanks Andy - not disappointed from what I have heard so far.  Appreciate you notes that led me to it.

I am also surprised by the overdriving given specs of cartridge / pre-amp - looked like I would have been well under.  But I am getting quite consistent 'overdrive' led on some passages so will have a go at adjusting.  Uwe suggests next 'stable' matching of resistors sets peak at 3v so I will do that and see what happens.  If that is too low the board actually has circuitry to make further adjustments using some circuitry the related USB / Volume control kit uses -- details are on his circuit diagram. 

Will certainly go down the LPS path - wall wart was easy for quick testing it worked and getting a handle on gain.  From specs it only draws 200ma - so may even piggy back off the 12v LPS powering my miniDSP.

Gibbo

 

 

 

 

Link to post
Share on other sites
10 hours ago, gibbo9000 said:

From specs it only draws 200ma - so may even piggy back off the 12v LPS powering my miniDSP.

Gibbo

 

Hah - that's exactly what I am doing, David!  :thumb:

 

(I used a case for my ADC which is large enough to contain 3x 25v caps - as well as the PCB - which feed: miniDSP, ADC and my 4-way digital source selector.)

 

Andy

 

Link to post
Share on other sites

Some close out notes on the Uwe Beis A2D Converter Kit - AD24QS 24 Bit / 192kHz.  https://www.beis.de/Elektronik/ADDA24QS/AD24QS.html#DIY

I have modified the resistors so it is now 3v full scale input and the overdrive led is triggered only very occasionally.

But I did learn a couple of things in case anyone else thinking of building one finds this:

  • The resistor sets Ra and Rb that control full scale voltage should ideally be in multiples of 1.1 to 1.2 - so 2k2 and 2k4 for 2 volts, 3k3 and 3k6 for 3 volts etc.  Uwe's notes "The correct ratio provides an optimal common mode rejection when converting an unbalanced (or badly balanced) signal into a balanced one"
  • The board is set up to easily make the gain fully variable.  The relevant notes are actually under the description for the AD-IOA extension kit under modifications on the AD24QS for the AD-10A.  Basically set the full scale resistors to 5k36 and 5k9, populate R3 and R20 with 30R, and add a 2k pot (negative log recommended but not where to find them!) across points on the ST header (see circuit diagram)

Gibbo

Edited by gibbo9000
Link to post
Share on other sites
On 01/09/2020 at 12:49 PM, mwhouston said:

I really dont know. Hard to connect the batteries the wrong way but odd both went out together. I tested the voltage across them before I pulled them out and it was perfect. Also I’m sure I use the preamp after the better change and it was fine. 
 

Going to put the chips back in for another check but I’m sure they have failed. Lucky I have spares having bought six or so OPAs from RS not so long ago. 

That’s the good thing about being addicted to audio projects you always have 50 spare op amps, Jfets, transistors, etc etc.. I think when the Toshiba 2sk170 went EOL I bought 200 🤣

 

I’m far from  

Link to post
Share on other sites
2 hours ago, hyper said:

 

I think when the Toshiba 2sk170 went EOL I bought 200 🤣

 

 

Do you have any spare you will part with?

 

Andy

 

Link to post
Share on other sites
2 minutes ago, crtexcnndrm99 said:

The obbligato cap arrived today for phono power supply :D 


Here was I thinking it was smaller than the Teflon’s - oops 

 

Yes - but the Obbligato is 22uF, the ruski teflons are 0.22uF!

 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    No registered users viewing this page.





×
×
  • Create New...