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 Post subject: Re: What are you DIYing?
PostPosted: Thu Apr 21, 2016 5:16 am 
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Well, if you go for a projector, you've got a screen. WOW.


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 Post subject: Re: What are you DIYing?
PostPosted: Thu Apr 21, 2016 10:22 am 
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Location: Saskatoon, SK. Canada
Believe it or not I had such a bad suckout that when the subs were stacked in that location the bass was almost non existent unless you were standing a foot in front of them.
Once I moved each of them to the front corners the house started to cry. The door leading to the furnace room 30' feet away rattles like it is possessed. lol
Lot's of pressurization in here.
The room is roughly 24 x 30.


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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 1:00 pm 
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Location: Medicine Hat's where E's at, AB, CA
Well, I am putting the last few finishing touches on this Decware SEC84-based amp that I bought in kit form from a fellow CAM'mer a while ago.
It has been built using some upgraded components when compared to the original kit and was given the "Hazen Grid Mod" that Mr. Deckert talks about in his latest amplifiers.
I am still needing to install an Input selector to turn it into an integrated stereo amp, but so far the single set of inputs have allowed me to test it out using both SS and tube preamps with very convincing results.

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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 1:20 pm 
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Lovely little amp build. Thanks.

mechstek wrote:
Well, I am putting the last few finishing touches on this Decware SEC84-based amp


I've sort of hankered after a Decware tube headphone amp kit, but such a thing does not exist anymore.


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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 1:43 pm 
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Toby wrote:
I've sort of hankered after a Decware tube headphone amp kit, but such a thing does not exist anymore.

I've not heard it, but the Borbely head phone amp looks quite interesting.
Uses 6gm8 (ecc86) tubes - which was a low voltage tube designed for car radios.
The most difficult part may be getting a hold of the MOSFET's.
However, there is no output cap.

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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 2:10 pm 
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It does indeed. So much so that I could spend a long long time working out how to build it. Um, what is the diode with the opposite-pointing fins at each end of the straight line, in the symbol at the bottom of the diagram ?

Uunderhill wrote:
the Borbely head phone amp looks quite interesting.


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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 2:20 pm 
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I really should be working on our kitchen reno.
But here is an oscillator I designed to test audio amps.

When the output of the NAND gate goes high, current flows through the 100K variable resistor to charge up the 10nF cap.
When the voltage at the cap rises high enough, it trips the NAND gate to go low.
Then the 10nF discharges via the 100K variable resistor.

The shape of the waveform created is based on the number e.
https://en.wikipedia.org/wiki/RC_time_constant

The NAND gate used needs to be a CMOS type with a schmitt trigger.
The first Op Amp acts as a buffer, so that it doesn't load the charging and discharging of the 10nF cap.
The second Op Amp provides the volume control.
A static charge can fry CMOS - so chip sockets will allow easy replacement.

The case I used was from an old parallel port switch box and a 12 Vdc wall wort provided the power.
Actually a "12Vdc" wall wort measures 15Vdc.

The NAND gate and Op Amp had their own voltage regulator.
Generally speaking digital and analog should have their own supplies.
.


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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 2:37 pm 
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Toby wrote:
It does indeed. So much so that I could spend a long long time working out how to build it. Um, what is the diode with the opposite-pointing fins at each end of the straight line, in the symbol at the bottom of the diagram ?

Uunderhill wrote:
the Borbely head phone amp looks quite interesting.
That's a Zener diode, Toby, a specialized diode designed to take advantage of a semiconductor's inherent resistance to reverse current. Basically, it's a voltage regulator that works by conducting at a predetermined reverse voltage called the breakdown voltage, in this case 2.5V. Here, it appears to be configured as a current mirror to control current through Rs.

The negative input isn't shown as tied to ground, but I assume it can be for single-ended operation.

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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 2:44 pm 
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Toby wrote:
It does indeed. So much so that I could spend a long long time working out how to build it. Um, what is the diode with the opposite-pointing fins at each end of the straight line, in the symbol at the bottom of the diagram ?

Uunderhill wrote:
the Borbely head phone amp looks quite interesting.


The diode at the bottom is called a Zener Diode.
http://www.farnell.com/datasheets/2045811.pdf
When reversed biased, they are used as a simple voltage reference.
The idea is that as current flowing through them may vary, but the voltage drop across them remains reasonably stable.
In this case, the voltage reference is 2.5Vdc and part number is a 1N5222.

The 10K resistor is used to set the current flowing through the zener.

The 2.5 Vdc reference is used to help set up Q3 as a current source.

Both the tube and Q2 operate in class A.

I've just noticed an issue with this design - that occurs during warm up.
A tube typically takes 11 seconds for the heater to warm up and get the cathode working.
However, the MOSFET's need the tube to be working to set the bias.
So I suspect the output will hit one of the voltage rails + or - 24Vdc until the tube warms up.
There is no cap on the output.
So the output will be + or - 24Vdc for about 11 seconds during warm up - yikes !

One solution may be to have a power switch for the heaters
and another switch for the circuit.

The other issue may be getting a hold of the MOSFET's.
http://www.bdent.com/2sj79-renesas-audi ... istor.html
.


Last edited by Uunderhill on Sun May 15, 2016 3:15 pm, edited 1 time in total.

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 Post subject: Re: What are you DIYing?
PostPosted: Sun May 15, 2016 3:11 pm 
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Thank you, gentlemen! Another demonstration that the only dumb question is the one I don't ask. :roll:


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 Post subject: Re: What are you DIYing?
PostPosted: Tue Aug 09, 2016 2:27 pm 
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A friend asked me to help her with assembling a Clone headphone amplifier (Help meaning build the whole thing and give it to me when its working) I think she got the board off eBay, looks decent enough. I am now curve tracing all of the transistors to match them into pairs (bought 100 of each). Also trying to figure out a better heat sink solution that is cost effective, not fond of putting that much heat onto the surface of the circuit board.

Update:
Fabricated a chassis from some spare aluminum I had in the shop, gave it a quick shot of Grape (her favorite colour) It will have solid wood sides (probably cherry as I have a bunch) mounted using threaded inserts. The top will be clear Lexan drilled for some ventilation and lightly sprayed with the Grape colour to create a translucent top

It is now up an running.
I used a medical grade transformer with flux band and shield between the primary and secondary, this makes for a quiet power source the regulation is also much better with the voltage rails being +15.1 and -15.06 after the regulators and filter caps. I seriously over build the power supply using a 50VA transformer and 6800 uF filter caps. The plans called for Ultra fast avalanche Diodes with .1uF caps across them to slow them down a bit, my experience has shown that ultra fast diodes can sometimes cause noise so I elected to go with standard speed diodes and the .1uF caps the result is dead silence on the output at any gain setting and volume position. The measured DC offset is not bad at power on its 2.1 mV and 4.5 mV after warm up it drops to 1.7 mV and 3.6 mV not perfect but not bad for a design that relies on transistor matching to control DC offset.
The sound is amazing with excellent high frequency extension and well controlled bass, voices are clear with no midrange bloom, cymbals sound as the should with no evidence of smearing, the sound stage has both width and depth. I like the little amplifier so much so it will be hard fro me to hand it over to it rightful owner but I don't think it will be too long before I build one or more for me.


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 Post subject: Re: What are you DIYing?
PostPosted: Tue Aug 09, 2016 3:20 pm 
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Kvn63, if I'm not mistaken, those look like the classic TO-220 profile. If you mount them vertically, you can always do what we used to back in the day and cut out small individual rectangles of double sided copper-clad PCB and bolt those to the transistors vertically with heatsink compound. Twice the length of the transistor can dissipate quite a bit of heat, but any length up to the height of the PS caps should do nicely. Another old trick is to use thin gauge aluminum sheet pieces the same size as the earlier PCB material or even wide enough to bend 90 degrees on opposite sides of the transistors.


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 Post subject: Re: What are you DIYing?
PostPosted: Tue Aug 09, 2016 4:25 pm 
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That looks class A/B. How hot can they get in a 200mW A/B amp? What's the bias current?

Why would the board be designed that way if heat was an issue?

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 Post subject: Re: What are you DIYing?
PostPosted: Sun Feb 26, 2017 6:34 pm 
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In light of drywhitetoast's very great new thread...
http://www.canuckaudiomart.com/forum/vi ... hp?t=45843

I thought I would bring back this thread since I did not purchase these new babies, but rather build them.
It was a little more than I thought it would be but I am very happy I "went for it".

I can now stop with my Klipsch "fascination", it really cannot get any better... can it?

I did take a ton of pics along the 3 month build journey (10 months from the planning stage) and I may start a dedicated thread, but for the time being...

Where it started back in November:
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And now:
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-- 26 Feb 2017 21:46 --

Sitting purdy in their corners...

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 Post subject: Re: What are you DIYing?
PostPosted: Mon Feb 27, 2017 2:13 am 
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Looks sweet!! Which horns are those on top?


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