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DIY audio: what are you building?


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2 minutes ago, Red MacKay said:

Nah, he is obviously no fool and knows what he is doing.  Well done.

 

If you or I were doing it Mark - well that would be pure foolish!

No, I am not that brave either.

The only Tranni I have ever wound (and wound about 6) was a step up Tranni in a SMPS. 10 turns on the primary and 80 on the secondary. Produced 250V from 12 I think. 

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Just did the DEM cap mod on the Marantz along with adding two 6k8 resistors from those two pins shunting to pin 15.

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Edit: need to order some silver mica's for this when I get around to it.

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Lots of other things needed doing today but I made a bit of progress anyway. I wound 2 strands 220 times around the holder which hopefully is the right amount. Half way through I thought I made the holder capacity a bit too small & I was right! It did fit on but it was threatening to jump off at any moment. I went around the loop once before I rang out of time.

 

If you ever want to do this, I highly recommend you grow a third arm first

 

Even if this works, I'd be surprised if I would do it again, if all I was after was a low voltage supply then fine, or to tweak a transformer voltage output, but not 1450 turns to get 150v! Starting with a prebuilt transformer is definitely a winner.

20200524_184832.jpg

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1 hour ago, DQ828 said:

Even if this works, I'd be surprised if I would do it again, if all I was after was a low voltage supply then fine, or to tweak a transformer voltage output, but not 1450 turns to get 150v! Starting with a prebuilt transformer is definitely a winner.

imageproxy.php?img=&key=6052995cfa95af68imageproxy.php?img=&key=6052995cfa95af68

...But think of the satisfaction and bragging rights!  Awesome job.

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On 24/05/2020 at 12:33 PM, mwhouston said:

The only Tranni I have ever wound (and wound about 6) was a step up Tranni in a SMPS. 10 turns on the primary and 80 on the secondary. Produced 250V from 12 I think. 

 

I once rewound a big tranny to make a high current 12V power supply - back in the days before switching supplies etc..  Big job.

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It took me about 1 hr to go around the ring one more time and my back had given by them, doesn't like the stooping over!

 

I have no idea how many more times I need to go around, I wish I had put some markers in the holder as I wrapped the wire on there so at least I would have some idea. At this point I'm going to guess 3ish.

 

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2 hours ago, DQ828 said:

It took me about 1 hr to go around the ring one more time and my back had given by them, doesn't like the stooping over!

 

I have no idea how many more times I need to go around, I wish I had put some markers in the holder as I wrapped the wire on there so at least I would have some idea. At this point I'm going to guess 3ish.

 

Silly man. 

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Hey, check this out - cheap device (can be had for less than $10)  that measures diodes, transistors, resistance, capacitance, inductance etc etc, and even sorts out the pinouts and displays the results graphically.

 

Google LCR-T4

 

 

 

616EUuSuk2L._AC_SL1010_.jpg

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14 minutes ago, Ozcall said:

I have one of those , well very similar and a case on the way at the moment

Looks like it works very well in the videos on youtube.  I just ordered one from Amazon.  Even if it's only a toy, it's so cheap.

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THey are great, I have one in a perspex case.

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1 minute ago, Batty said:

THey are great, I have one in a perspex case.

 

One use I will make of it is to read those damn little 1/4 watt resistors for me.  My eyes can't discern the colours properly on them, they are so small.   :) 

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3 hours ago, aussievintage said:

Hey, check this out - cheap device (can be had for less than $10)  that measures diodes, transistors, resistance, capacitance, inductance etc etc, and even sorts out the pinouts and displays the results graphically.

 

Google LCR-T4

 

 

 

616EUuSuk2L._AC_SL1010_.jpg

Had one for a while absolutely essential.  

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6 hours ago, aussievintage said:

Hey, check this out - cheap device (can be had for less than $10)  that measures diodes, transistors, resistance, capacitance, inductance etc etc, and even sorts out the pinouts and displays the results graphically.

 

Google LCR-T4

 

 

 

616EUuSuk2L._AC_SL1010_.jpg

Didn't even know they existed !

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Do you want it to go low? If not you might find a “midrange” that does that, but it is unlikely if you want to do bass with it.

 

dave

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I'm looking for tips on how to paint MDF speakers, atm I am sanding them to level all the joints, then I assume I need to prime them before painting, I'm thinking of a satin finish.

But as I have not done much serion painting I was looking for advise on how many coats and how far to sand back between coats, even how long to allow the paint tod dry before sanding back.

 

TIA for any help.

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9 minutes ago, Batty said:

I'm looking for tips on how to paint MDF speakers, atm I am sanding them to level all the joints, then I assume I need to prime them before painting, I'm thinking of a satin finish.

But as I have not done much serion painting I was looking for advise on how many coats and how far to sand back between coats, even how long to allow the paint tod dry before sanding back.

 

TIA for any help.

 

It depends on what paint you choose.  Not being funny, but I just follow the instructions on the paint can for drying times and when it can be recoated etc.   

 

When I sand back, I just run my fingertips over the surface and if I feel any pimples or lumps I keep sanding.

 

I have also used textured coatings to finish speakers.  Stone, or crackle finish, or stucco maybe might appeal.

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I'm thinking Satin White as a contrast to the black stands I have on order.

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33 minutes ago, Batty said:

I'm looking for tips on how to paint MDF speakers, atm I am sanding them to level all the joints, then I assume I need to prime them before painting...

Sealing the very absorbent end grain (panel edges) is the issue with MDF. The panel surfaces are easy get a great finish on. So primer/undercoat is good to help get the entire surface sealed and even in texture before applying your finish coats.

I've not tried it, but 'sanding sealer' might be helpful if applied to the edges for a couple of coats (sanding between) before applying the primer/undercoat to the whole boxes.

https://www.bunnings.com.au/feast-watson-250ml-sanding-sealer_p1564778

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39 minutes ago, Batty said:

I'm looking for tips on how to paint MDF speakers, atm I am sanding them to level all the joints, then I assume I need to prime them before painting, I'm thinking of a satin finish.

But as I have not done much serion painting I was looking for advise on how many coats and how far to sand back between coats, even how long to allow the paint tod dry before sanding back.

 

TIA for any help.

Preferably use a colour sanding block, and if using hand don't involve the fingers, using a colour block wet sanding with wet/dry you can wipe the moisture away with the bare edge of the block along It's length and that will show any low/high of pitted areas.

Edited by muon*
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59 minutes ago, Batty said:

I'm looking for tips on how to paint MDF speakers, atm I am sanding them to level all the joints, then I assume I need to prime them before painting, I'm thinking of a satin finish.

But as I have not done much serion painting I was looking for advise on how many coats and how far to sand back between coats, even how long to allow the paint tod dry before sanding back.

 

TIA for any help.

MDF primer then sanding is a good way to go prior to final coats.

 

For the final coats you could use the Houston finish.

 

I have heard it is much talked about. 

 

-Dan 

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31 minutes ago, pwstereo said:

Sealing the very absorbent end grain (panel edges) is the issue with MDF. The panel surfaces are easy get a great finish on. So primer/undercoat is good to help get the entire surface sealed and even in texture before applying your finish coats.

I've not tried it, but 'sanding sealer' might be helpful if applied to the edges for a couple of coats (sanding between) before applying the primer/undercoat to the whole boxes.

https://www.bunnings.com.au/feast-watson-250ml-sanding-sealer_p1564778

I have used that on a guitar.  Works fairly well.

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Case arrived for my new Holton amp. Radical change of plan for me in that im abandoning my idea of building my own rectifier/filter stage and instead have signed up for a pair of the soon to be released Holton PSU boards to be released shortly. After chatting with the main man im convinced this will be a better path for me to follow and in reality he's  a 100x better engineer than I so who am i to argue.

 

20200525_123603.thumb.jpg.a8b59d0688c0d12855d247e5c446c589.jpg

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5 minutes ago, Tubularbells said:

Case arrived for my new Holton amp. Radical change of plan for me in that im abandoning my idea of building my own rectifier/filter stage and instead have signed up for a pair of the soon to be released Holton PSU boards to be released shortly. After chatting with the main man im convinced this will be a better path for me to follow and in reality he's  a 100x better engineer than I so who am i to argue.

 

20200525_123603.thumb.jpg.a8b59d0688c0d12855d247e5c446c589.jpg

Exciting times , can't wait to hear how the result goes - or better still hear in the flesh! 😁

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57 minutes ago, evil c said:

Exciting times , can't wait to hear how the result goes - or better still hear in the flesh! 😁

Where did you order the enclosure. Make, model dimensions and cost. 
 

I like it.  

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I haven't used the FW Sanding Sealer for quite a while but I always found it clogged the sandpaper bigtime, in the end I stopped using it, maybe the formula has changed.

I normally use the MR MDF which I think absorbs less and obviously will standup better if damp/slippage ever becomes an issue. With the last boxes I made I mitered the corner joins so there wouldn't be any raw edges there, and then coated the ends (Open Baffle no front and back) with hard drying glue, spray the boxes with Duratex water based  Texture coat, over sprayed with automotive colour and then overcoated with Mirotone water based satin wood lacquer 😊

If you think about it I have broken a few rules but the finish still looks good with no peeling after 7 years.

 

13-01-20 DQ OB Finished01.JPG

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5 minutes ago, DQ828 said:

 

If you think about it I have broken a few rules but the finish still looks good with no peeling after 7 years.

 

 

13-01-20 DQ OB Finished01.JPG

That looks gorgeous, I like it much better than the overused high-gloss/piano lacquer. And how excellent are those geckos...

 

I’m a woodworking idiot, and eagerly soak up the nuggets of knowledge transpiring from this thread (and a few others).

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Thank you, but I cant claim the geckos as my brother made them for me.

I wouldn't recommend you spray waterbased over automotive paint like I did, the adhesion can be a problem.

 

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9 hours ago, Batty said:

I'm looking for tips on how to paint MDF speakers, atm I am sanding them to level all the joints, then I assume I need to prime them before painting, I'm thinking of a satin finish.

But as I have not done much serion painting I was looking for advise on how many coats and how far to sand back between coats, even how long to allow the paint tod dry before sanding back.

 

TIA for any help.

I found this was really good for prepping mdf especially the end grain.

 

https://www.supercheapauto.com.au/p/septone-spray-putty---blue-acrylic-400g/33228.html

 

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I spent a fortune on loads of hifi gear recently and since I’m a maker, working with many materials, the building of a custom unit to house all the gear was a no-brainer. The way my lounge room is arranged, it had to be quite shallow, at least the lower part, to fit between my 2 seat movie recliner and the wall. The lower section is 360mm deep, but the top shelf is about 20mm deeper to accommodate my turntable.


Even though I’ve made many objects, most are art pieces and precise measurements, being square etc isn’t important most of the time. And this is probably the most extensive joinery I’ve attempted, using only joints and glue. I wanted this thing to look cool, which is far different to making purely  functional furniture. Where I might use a nail gun or screws.

 

I don’t know much about joinery and knew dovetails or mortise and tenons weren’t suitable, or too time consuming, so a quick google had me discover the rabbet joint. This is a simple joint where a recess is cut on both ends of two sides of a box with the other sides glued and fitted into them. There was a fair bit of tedious work cutting and chiseling, but I like the look and it’s straight forward.

 

Basically, I made one long and slender box, to house speakers, turntable, pre & power amps and CD player and one almost square box which acts as the support for one end, and holds most of my record collection. It also has a small area for miscellanies, headphones etc. 

 

The design called for legs at the other end as my subwoofer is placed there and there isn’t a better spot for it. Now it’s built, I see that another record “box” can fit right next to the other and could probably move the sub as I’m putting my tv on the wall, hence making better use of the space.

 

The unit is made out of 15mm plywood primarily. I originally had Tasmanian oak or similar in mind but it’s not cheap. Then I happened to see cypress pine tongue and groove floorboards at my local hardware and loved the grain. It was more affordable and the t&g would make constructing a wide board easier too. I made the top from it, but plans changed a few times and the idea to use ply came after googling for inspiration and seeing some really cool stuff made with low cost materials like osb/chip board, ply and pegboard. I wanted to use osb, but couldn’t source any locally, so went with CD ply. It has one “good” side, which looks pretty good with some light sanding.  The legs were turned from square pine packing posts I got free from bunnings. They came up nice. Was going to paint them red but couldn’t wait to set up all my new gear so they’re coated with clear polyurethane like most of the unit currently.

 

Besides reminding me of a computer desk, I’m pretty chuffed with the result. And if you got this far, congratulations. Sorry about the novella but I figured details would be appreciated 😁

 

I’ll post pics when I get them off my camera.

 

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Brought up the 98db efficient 12" Beymas from system two to have another listen with my 2W 6L6 SE UL power amp. Played it for a few days and loved it. Plenty of volume.  After reading the Salt Cellar article in Stereophile mag recently I wanted to reproduce something like what they set up. That is very low power simple amps with efficient horns. Don't have the horns (not setup for this anyway) but do have the Beyams. 

 

Out comes the 1/3W UX-171A tube amp "Intermezzo". it is about as simpler an amp as you can imagine with only an input tranni and a low power power tube (0.6W). I moved up closer to the speakers and enjoyed a day of classical music at reasonable volume. If you have over 100db sensitive speakers you will have plenty of volume. Zu Druid owners (I can think of one) would love this.

 

I wondered if someone else may have this style of tube sitting around and may want to build the amp. I designed my amp based on an AudioXpress article where another came up with the idea.

 

You need a couple of Tubes, two nickel core Hammond inter-stage trannies, 5K/8ohm OPTs and a 180V PS. Simple. Here the schematic which is my take on the original. I used 9V batteries for the bias which will never go flat from use. There is little to no current drain. 

 

 

Intermezzo PS.jpg

Intermezzo.jpg

Intermezzo_I.jpg

Intermezzo_II.jpg

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Just a warning about my UX-171A amp, the input impedance is 400ohms. I either use one of my many tube preamps with a battery SS headphone amp or my Elite tube preamp which has a HP driver built in. Works well. 

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Reminds of the very first radio sets, built back when there were not so many passive components readily available.  Circuits tended to be mostly transformers and DH valves.    

 

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