Full Range TV console

The Good Wife, and I have decided to, tentatively, throw out the tube amp and Magnepans from the living room, and build a monster sound bar for the TV. The idea, has been in the back of my head since the experimental Boom Bench several years ago, out of two folded quarter wave horn speakers with Tang Band 4 inch full range speakers. This time the project is inspired by a more woodsy interior refurbishment, and my love of the 8 inch Visaton B200‘s that reside in the man-cave.

Betsy-K (1)

I found a pair of lightly used Wild Burro Betsy-K speakers, with Planet 10 Phase plugs for sale on Finn.no They will form the basis for the build. Now, instead of doing all the calculations and correctly dimensioning the cabinets, I am going to go the carefree and careless approach of designing something that fits under the TV and seeing what the sound is. Afterwards I will try to amend any issues by ear, with stuffing, baffles, notch filters and similar. Imaging will be bad, bass response is not expected to shake the house. but for uncritical family listening, I think my cohabitants will be pleased. So without further to-do, here is the design:

stereo console

Dimensions are 110cm long by 25cm high by 40 cm deep. What will be inside this box, you ask, TAO?

Um, well,

A chip-amp, possibly with Bluetooth for family members smartphones. Maybe some kind of ported, stuffed, single volume. The volume will not be large enough to make two individual back loaded speaker cabinets in one, I think. Bass will be strengthened by the placement close to the floor, and somewhat in a corner. As far as I have read Betsy’s are a bit bright, and many posters on forums compensate by playing them of axis. So maybe the low position will help a bit in that department. The proof of the pudding is in the listening. But first, shopping and chopping 🙂

Follow this post for updates !

 

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A great introduction to power supplies

Nick Whetstone at Decibel Dungeon, has a great introduction to power supplies for chipamps (Gainclone). Also this is a site with a lot of really accessible intro stuff on any other aspect of the HiFi hobby. Although not directly applicable to tube amps, there is a lot of good, solid advice on understanding, and safely using standard power supply parts in there. Go and check it out!

psu

Image from Decibel Dungeon

Bass reflex Tang Band W4 speakers

Several years ago, at the beginning of this blog I bough two TangBand W4 1320 four inch, full range speakers from Parts Express. I built some quarter wave horn cabinets to mount them in, described in a previous post. Later they turned in to a Boom Bench that didn´t really work out. Then they went into retirement in a bag full of  speaker damping materials and where forgotten for a few years.

13EM7 Amplifier Building the 6S45P amplifier part two

 

 

 

Then about three years ago they resurfaced and I thought I might as well use them for some small speakers.

I researched Applications of the Tang Band W4 and found a nice, simple recepie in the “Swift” by Emil Attid of the website Nth Audio. The plan calls for a 5.5 liter cabinet with a tuned port at 70Hz. Side dimensions 320mm H x 240mm W  and about 150mm wide – depending on material dimensions. Emil Attid provided measurement drawings, so it was a simple thing to cut up some 16mm birch ply I had available. The nice thing about this design is that you can rip 120mm wide strips of ply and then work out the lengths for the individual components afterwords. A straight forward build, with nice proportions.

I hope its ok, Emil, to repost your plan here.

I made one speaker, glued it up except for one side that I left open to work out what damping I liked. Once I had it sounding nice I put it on a shelf along with the rest of the materials and promptly forgot it for 3 years.

It is a problem that once my initial interest in a project is satisfied, I end up not following through with it. Sound familiar?  I am surrounded by these kinds of projects.

Then, a slow Friday at work I decided I needed to finish the thing. I cut up the strips of ply for the second cabinet and glued them up with white glue. In the intervening years I had used up the rest of the nice 16mm birch ply so this time I went for 17mm MDF for the sides of the speaker. They are going to be finished in paint so it does not really matter.

 

Hurray! 100.000 visits jubilee

Thank you to everybody who visits my old TAO of Tubes site over on Blogger. Together we have racked up 100.000 site loads! I sincerely hope some of my posts have been useful.

Due to my dislike og googles data gathering and pressure to move to google+ , I have decided to reestablish TAO of Tubes here at WordPress. For now the Blogger site will continue to exist, but new posts will only be added here at WordPress.  Sorry for the inconvenience.  I hope you will update your bookmark and move with me over here. I would also like to apologize for the building noise and the mess as we are moving inn.

Phono preamp for moving magnet turntable pickups

RJM audios VSPS or Very Simple Phono Stage, for short, at http://phonoclone.com/diy-pho5.html  It´s a simple dual op-amp design with a modified Allen Wright RIAA stage and only 27 parts.
You can read a detailed description of the design on RJMs site. There is also a huge and active thread over on DIYAudio, and a discussion of powersupplys on audioKarma

http://beavishifi.com/articles/phono-preamps/ has published this simple diagram of the circuit. But note that RJM also suggests adding adjustable gain by switching between three values of R2.

My plan is to build this phono pre-amp and install it in a case that is suitable for display in the living room system. I am using strip board to build on. And I´m planning to power it with batteries.

Starting with the socket for a dual op-amp NE5532 in the top middle, I established the power strips next. The chip is powered by +12V  and -12V with reference level, ground, in the middle. I decided to use the bottom strip as ground and the nr 8 pins strip near the top as +12 V.   -12V is not yet assigned a strip, I just soldered on a piece of black wire as a reminder, but later changed this to orange to remind me it is not ground.
Next I connected the right and left  + INputs from pins 3 and 5 to ground via two 47k resistors to establish input level relative to ground.

Next I decided to solder in three R2 resistors. Considering that the inputs may be more sensitive that the outputs, I soldered these resistors from the -IN strips  As suggested by RJM I will use 2.2k for 30dB, 680R for 40dB, and 220R for 50dB. I started with a nice 1% Vishay metal film closest to the middle for 2.2K, but only had ordinary 10% for the 680R and 220R. For the 680R, in the middle, I only had 670s but the nice thing about 10% resistors is that you can find some deviants, and after sorting through 10 of them I had two 675R, which is as close as I will get for now. I also matched the 220Rs and found two that were spot on. All three were soldered to their own strip in the other end where I will later have a 3 way switch to ground to choose gain. Then the strips were Dremmeled away in the middle to create separate channels, like I did, previously, under the op amp.

Next is the RIAA stage between -IN and OUT which is pins 1 and 2 on the left side and pins 6 and 7 on the right side. Due to the amount of hardware going into these strips I need to move one strip down a bit. Intuitively I would move OUT, since -IN might be more sensitive to noise.
I have substituted some values for what I have and this fits RJM´s recommendations for higher precision, which is a plus: 2.2K , 105K and 732K all 1% Xicon Metal Film resistors. For capacitors I am using 1000pF 100V 2.5% WIMA polypropylene and tripling them for the 3nF value. As shown here:

For the final stage in the build its time to add the OUT components. First the bottom strip of the RIAA stage is connected to OUT on pins 1 and 7 with green wire. Then the output coupling components go into place; a pair of 47R 5% Kamaya Carbon composition resistors followed by a pair of 2uF 250V 10% Sprague polypropylene capacitors. unfortunately I did not have 2.2uF, hope it works OK anyway. I mount all these along the OUT pin strips so I have to cut the strip under the components. Finally a 33k resistor to ground to drain of the capacitor. For this resistor I am using a generic 1/4 watt 10% again, I have a 32k and the value is not critical, according to RJM, so I´ll go with it.

Oh, and the Vcc- with the orange wire – I stuck it an an unused strip so I could power the board from the right edge.  Let the the debugging begin!

Follow TAO as he messes around with tube amps, speakers, etc.