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Paul Spencer

DIY audio: what are you building?

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nice  do let us know how it sounds

 

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Thanks Owen.  Yep, I had to do a bit of googling to remind myself about which direction is which :)

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Ever tried to fix something which is not broken because you think it shouldn’t work that way it does. I have made four of these active load preamps. In the second last one I added a headphone driver. When head phones are plugged in the jack it cuts out the RCAs out which are used when Elite is just a preamp. 

To get better performance from the preamp/HP amp I moved the pot from the backend (where it is on the other three builds) to the front end. That meant the expensive Jansen CuPIO output caps could feed directly into the HP chip amp with no other input cap needed. 

The reason why this cct. is described with attenuator on the rear is because active load is very microphonic. With the attenuator on the output you hold the noise down and the music level very quickly swamps any noise from the tubes. BUT put the pot on the front you get the full microphonic noise unattenuated and the music level lower. Fortunately some old RCA 6SN7s aren’t naturally noisy and with these in the system the preamp/HP amp is very good. But put some better Psvane or Chuguang tubes in the noise swamps the music. 

I’ve spent two weeks trying to get the microphonics out. It’s a part of the build. Best I can do is move the pot to the backend and add some interstage caps into the HP chip amp section. Best way to go.

7E1E4D85-4AFE-4F5B-8218-877C69B30374.jpeg

25BF875C-0789-4A6A-B9A1-9762CF509581.jpeg

9F28A68B-EC1B-48F9-BA3A-A15360BC7F44.jpeg

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A little bit closer.  Probably another few hours of work left.
 
installed a Khozmo 64step attenuator with amrg resistors. 
 
duelund 20ga tin plated wire used for hook up.
 
will heatstrink exposed cables after run-in.
 
58F00717-FF40-4EE5-B3F4-74C6377338B4.thumb.jpeg.0c9f0a93f89e19fa9c4a0b8002048010.jpeg
Nice work mate. You always have nice taste in gear.

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5 hours ago, Sub Sonic said:

Can I ask where you got the tubing? Looks interesting 🙂

A place in melbourne called Darpac. They use similar tubing for concrete pillars, but it is often plastic lined, which i avoided as i'm relying on adhesives a lot for this build

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4 hours ago, tuyen said:

A little bit closer.  Probably another few hours of work left.

 

installed a Khozmo 64step attenuator with amrg resistors. 

 

duelund 20ga tin plated wire used for hook up.

 

will heatstrink exposed cables after run-in.

 

58F00717-FF40-4EE5-B3F4-74C6377338B4.jpeg

You have some nice capacitors there. Have you had a chance to experiment much with the Miflex caps?

 

SS

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1 hour ago, Upfront said:
4 hours ago, tuyen said:

A little bit closer.  Probably another few hours of work left.
 
installed a Khozmo 64step attenuator with amrg resistors. 
 
duelund 20ga tin plated wire used for hook up.
 
will heatstrink exposed cables after run-in.
 
 

Nice work mate. You always have nice taste in gear.

Thanks mate.  I cant help myself. Go crazy on partsconnexion after every payday.   Forever poor.    Boutique hifi though!

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Thanks mate.  I cant help myself. Go crazy on partsconnexion after every payday.   Forever poor.    Boutique hifi though!
I actually laughed out loud when I read that!

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8 minutes ago, Sub Sonic said:

You have some nice capacitors there. Have you had a chance to experiment much with the Miflex caps?

 

SS

 This will be my first taste with the Miflex copper foil caps.   They seem well built.  Price was right as well  (compared to duelund/mundorf sgo/jupiters).    

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1 hour ago, tuyen said:

Thanks mate.  I cant help myself. Go crazy on partsconnexion after every payday.   Forever poor.    Boutique hifi though!

Have you used Hificollective in the UK? Decent prices and realistic shipping cost compared to North America 🙂

 

SS

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On 23/05/2019 at 3:27 PM, A J said:

I think I want this t-shirt

I have one.

 

Although is a bed shirt these days  :)

 

EDIT:  Oh wow... That was an old post.  Have I been gone that long  (?!!)

Edited by davewantsmoore

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Made these up for a fellow SNAer and DIYer. 1/2M twisted silver plated fine copper  wire. Two earths at the originating end one at the terminating. Following Allan Wright’s guidelines for light weight RCA plugs. Silver soldered and directional. 90pf capacitance. 

BBD49031-985C-476F-92D4-A6418777333D.jpeg

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Going on with the Audio Analyser thingo...

 

Small recap: STM32H7 nucleo microcontroller board with Ethernet interface, a DAC and an ADC, and software in Python to see audio data over the Ethernet interface. All open source.

 

Work is ongoing, no easy task, however, some major successes that encourage to go on:

- Was able to find a configuration that allows me to sample at 96KHz smack on.

- Was able to send out a waveform through the DAC (PCM1793)

- Was able to get data in on the ADC (PCM1802)

- Was able to send commands (stop, start, read, etc) to the microcontroller using the Ethernet interface and Protocol Buffers (Google: "protobufs").

- Able to read in data from the ADC and send it over the network interface to the PC.

 

And this is where we're at. I still have some issues to look at, synchronisation, operation, GUI, and many more, but, the basic stepping stone is there.

 

First image is the device itself: at the far end, in white, the controller board and just in front the ADC and DAC. Both are bridged together, basically the DAC output feeds into the ADC input. A tangle of cables, but it works. That should be replaced in some future by just one board.

IMG20190818190000.thumb.jpg.09dc347b33fd8c22fc485d46291fb5f0.jpg

 

And here, the data capture displayed on the PC:

Figure_1.thumb.png.9442a5edeb582ed08a1ed0cec2d81bf6.png

I haven't scaled anything, the format is still 32 bit signed integer and you can see I have some spikes that are due to some memory overlap on the data transferring. I need to sort that out, like I said, among other things.

 

Cheers,

 

Alberto

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On 13/08/2019 at 6:54 PM, Sub Sonic said:

Have you used Hificollective in the UK? Decent prices and realistic shipping cost compared to North America 🙂

 

SS

Used them on a number of times. 

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On 13/08/2019 at 8:54 PM, Sub Sonic said:

Have you used Hificollective in the UK? Decent prices and realistic shipping cost compared to North America 🙂

 

SS

Yes, me too, many times.

Good people, good service.

 

Cheers, Owen

Dark Lantern blog - http://darklanternforowen.wordpress.com/

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Godda love the sound of ferrite in the Morning. Replacing the 1st order/2nd order Xovers on my 12” Beyma concentrics. They have been moved temporarily into my main system to work with my wine box 2W 6L6 SE UL power amp. At 98db sensitive there is plenty of vol. 

 

As I found with the Beyma 15” (recently sold) a 1st order Xover allows the full dynamics of these impressive Spanish drivers to come through. Xing at 1KhZ into the 2” titanium (16ohms) and Mylar tweeter with just the 1.27mH choke and 10uf cap. A 7db pad bring the tweeters down to the woofer level. Great sound.

06B0ACA0-E181-4C15-96FB-027AC2E46AEB.jpeg

Edited by mwhouston

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Built these preamp modules sometime back but wasn’t happy in the enclosure they were in or the PS. It’s a two stage preamp with a common cathode second stage. Whole idea is the preamp section is stage one and driver section on the back. Should drive better into SS power amps or long interconnects. 

 

Also the front end is universal so any 12A?7 can be used in the preamp section and a 12AU7 or 12AX7 on the back end. But the design is flexible and tubes can be mixed at will.

 

Also the part finished PS cct. brd. All my tube PS are choked (Hammond 5H) and this one is no exception. HT is double Pi; C-L-C-R-C. With snubbing caps. The filament voltage is DC single Pi C-R-C with 2X 4700uf of capacitance. The HT was 400uf of filtering and combined with the choke makes for an extremely quiet PS. The choke appears to provide better channel separation also. 

 

Tubes here are Mullard long plate re-issues. Brand new, never heard them. 

55930DFF-CC79-4518-AF4D-5693F4026DCC.jpeg

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For those interested here is the bottom of the preamp brd. Two lots of Russian PIO caps for interstage and output.

 

Metal Rs, ceramic tube sockets and all built on a turret brd. Looks messier than my normal builds but I like solid core hookup and shortest hookups possible. Not always a Rembrandt but electrically and sonically good.

28EA652D-20DF-4A15-BD99-0BDBE1858EEB.jpeg

Edited by mwhouston

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My first post. I'm rebuilding my Apoogees Centaur Minor, new box (+8 liters) ribbon decoupled from woofer box, external xover box, and a pair of subwoofers, 60 lts sealed powered by an icepower a250 module. Plus acoustic panels and diffusers. It's a long time work, all by hand with no CNC.

20190819_143446_Film3.jpg

20190816_174238_Film3.jpg

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The all FET headphone amp had two PSs it was being sold with (since withdrawn). Here is the inside of the linear PS. 3X 4700uf caps, high current bridge and some snubbing caps. Dead quiet PS. 

4F9BB739-8919-4A7A-9F6F-0E1490D2390E.jpeg

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If I donated a can of beans to a feed the world program for every time I  got left and right speakers mixed, from the day I got into hifi, as of this morning, I would have cured world starvation. 

 

Hearing bass on the left from classical vinyl had me pull out the test record. Sure enough right and left we’re Xed over. I pulled out the phono stage then the preamp to check (and meter) wiring, all clear. 

 

Then examined the power amp. All perfect. While reconnection the speaker to the power amp I realised my mistake. The same one I have faithfully committed regularly over the last 45 years. 

 

Thanks to me no child would have gone hungry had I beaned my mistakes to the world.  My main system has always been OK because after any re-configs I test it with a few test tracks. But this temp system has had a few re-configs. Somewhere along the line I had a brain fart. 

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4 minutes ago, mwhouston said:

for every time I  got left and right speakers mixed

Heck yes - and it sometimes takes ages to notice that somethings up. 

Balanced XLR's are my usual genius moment, don't have the white/red left/right thing, both are black.

... and of course audiophile purity means nothing has a balance control - something that would let you figure it out straight away

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3 hours ago, n0bleINtP said:

... and of course audiophile purity means nothing has a balance control - something that would let you figure it out straight away

That's provided that the pre/amp built was wired correctly. For "audiophile purity" my first couple of builds I used two separate volume pots so I could balance. The last I went for a balance pot. Took me a while for the penny to drop on that one.

 

Because (like others it seems) I get left and right wrong I have recorded one of my test records to computer, cd and cassette so I can test everything.

Still plugged one of my speakers in reverse phase the other day.

 

 

 

 

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The final PS with choke, heater limiting resistor and cords. After building about a dozen of these this is the best so far. So lots of images taken. Happy to build these PS for others. Works with 6 and 12V small tubes (e.g. 12AX7) and the likes of 6SN7s. 

 

This one is for a two stage preamp with cathode follower. 

B2EFB44D-787B-4B1E-8DBF-E6001037FD0D.jpeg

CC8CC51B-5B1C-42DF-8ECB-1B57D88EAA3B.jpeg

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