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Old 28th February 2004, 11:03 PM   #131
gjo is offline gjo  India
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Quote:
gjo, what's an AKSA enclosure? I have two EL34s I removed from my grandpa's old valve radio. Not sure if they work, and their leads are badly corroded. Made by BEL. Actually, my uncle identified them as EL34s, since their markings were all rubbed off.
AKSA is an Australian solid state amp kit sold without trannies and chassis. I bought a 55wpc version (they have a 100wpc version also) of these a year ago and use it with a solid state preamp. I also have an all tube system for audio.

George
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Old 29th February 2004, 01:42 AM   #132
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Default Polysterene caps

Hello Tarun,
Quote:
How easy or difficult is it to find polystyrene caps, say 100V rating and small values?
by tarun

As easy as writing to me. I have a lot of these in my shack with different voltage ratings- 5% tol. Use them for my RF circuits especially in RF oscillator circuits. Imported. I will give some of them away if you're interested. Alternatively, if time is of the essence you can try looking into a few ham shacks in Mumbai who might have them, like the Mumbai Amateur radio Club (MARC) . Many hams normally do.

100PF, 110PF 120PF 150PF 180PF 220PF 270PF 330PF 390PF 470PF,560PF 680PF 820PF 910PF 1000PF 1200PF 1500PF 1800PF 2000PF,2200PF 2700PF 3300PF 3900PF 4700PF 5000PF 6800PF .01MF

I hope that helps.
Patrick
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Old 29th February 2004, 06:41 AM   #133
tcpip is offline tcpip  India
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Default Re: Polysterene caps, knobs, AKSA amps...

Quote:
Originally posted by gjo
Tarun I will also be interested in some knobs....
Once you get your set, let us know the quantities and pricing with the photo...
I had a rich NRI friend stay over for the weekend. She owns a Canon digital camera, which takes lovely pics at 1600x1200. So I quickly shot some pics, and am posting them in a separate thread here. The background to these knobs you already know. I can always ask one of my DIY friends to pick up some more knobs from Uncle Harry, wrap each in a piece of newspaper, put them in a packet, and courier them to you, if you can send him the payment by DD. But these are not the custom-made knobs. Those are still "under discussion". I'll probably ask Harry to make 20 of them, 2" (not 2.5"... will look too big on a 2U chassis front plate), maybe 1" to 1.5" height, and a fine grain finish to match the ones I've photographed.

Quote:
AKSA is an Australian solid state amp kit sold without trannies and chassis. I bought a 55wpc version (they have a 100wpc version also)...
Check www.aksaonline.com ... and the designer, Hugh Dean, is a member of this Website, and uses the moniker "AKSA". He likes George a lot... he told me in an off-list email.

And Patrick:
Quote:
100PF, 110PF 120PF 150PF 180PF 220PF 270PF 330PF 390PF 470PF,560PF 680PF 820PF 910PF 1000PF 1200PF 1500PF 1800PF 2000PF,2200PF 2700PF 3300PF 3900PF 4700PF 5000PF 6800PF .01MF
Thanks for the info. Are polyester caps the same as polystyrene caps? And how much will these caps cost, say for the 1nF value? And what is the spacing between the leads for them?

Tarun
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Old 29th February 2004, 07:13 AM   #134
tcpip is offline tcpip  India
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Default Large black finned heatsink

This is the heatsink I'm using for my current amp project. It's 330mm long. I've fitted four BJTs on it; it'll be used for a stereo P3A.
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Old 29th February 2004, 07:22 AM   #135
tcpip is offline tcpip  India
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Default Heatsink with PCB

And this is how the PCB will bolt onto the heatsink. This is the partly populated board for the stereo P3A. I've decided not to populate the last few parts till I solder the hookup wires... it'll be very difficult to maneouvre the hookup wires once the larger components like fuse holders are in place.

I prefer to fix TO247 type transistors, and TO-220-derived ICs (e.g. gainclone chips) with a bar in front, rather than depend on that solitary off-centre bolthole at the top. If you just depend on that one bolt, the bottom portion of the IC/transistor tends to rise a bit, and this sharply reduces heat transfer. This is a lesson faithfully copied from Randy Slone's book.

The aluminium bar I am using cost me Rs.10/foot, from any hardware store which sells Al channels and sections for sliding windows and the like. The bar is about 3.5mm thick, and about half an inch wide. I drilled the holes. I use 3mm bolts. I fix them to the heatsink by drilling and tapping holes in the heatsink.

This heatsink cost me about Rs.550 from Visha. It is sold at a rate per cm running length. You can calculate the rate per cm. The only crib I have against this heatsink is that it's 100mm wide, not the exact 88mm I'd have needed to precisely fit onto a 2U chassis. Ah, well...
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Old 29th February 2004, 07:58 AM   #136
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Default About POlyester and polyesterene caps

Hello all

Quote:
Are polyester caps the same as polystyrene caps? And how much will these caps cost, say for the 1nF value? And what is the spacing between the leads for them?
by Tarun

No not same.
Difference between Polyesterand polysterene caps - Former are low cost, good stability and available in a large range of values. These are the most widely used capacitors for general purpose applications. Greencaps and MKT type capacitors are examples of polyester (polyethylene terephthalate) film capacitors.The latter ar usually chosen for applications requiring tight tolerance coupled with extremely high stability. Polystrene also exhibit a predictable temperature coefficient used in conjunction with particular ferrite cores makes highly stable tuned circuits for RF oscillators and high speed switiching. polystyrene capacitors are expensive and tend to be rather sensitive to heat. Used them in the shack in my RF oscillators, Phase Locked loops (PLL) VCOs and in my clock pulse for the homebrewed freq.counter amonfg other things.

Cost around $1-5 each from the US depending on value. My stock are half imported and half salvaged from old radios and foreign 'maal'.

lead lengths and spacing.... need to look in the shack and dig up the dust.Heh heh!! OK will let you know about that later.

By the way if you really want to know, how different dielectric caps make a difference in audio with all the math details, do look into our friend Steve Bench's site at http://members.aol.com/sbench102/caps.html. He's a telecom engineer in San Diego and has rich exp.on topics about caps and relevance to sound.

I hope that helps.

Patrick
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Old 29th February 2004, 11:16 AM   #137
tcpip is offline tcpip  India
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Default Banana sockets in plastic cup from MX

Thought I'd post a picture of this thing, since the camera was there. Just to show you what Rs.125 bought me. One thing missing is the pair of gold-plated brass shorting strips. One strip shorts both the black sockets, the other shorts the red ones. I've removed the strips since I will almost certainly be using the four sockets separately; I intend to use active xo in my speakers.
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Old 29th February 2004, 01:23 PM   #138
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Default MX Speaker posts

Here's a pic of the round MX speaker posts I was talking about. Taken thru a friend's webcam, excuse the poor quality.
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Old 29th February 2004, 03:05 PM   #139
gjo is offline gjo  India
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Tarun

What do the square terminals cost? Do they have a hole to insert bananas and then allow you to tighten the nut? I bought similar ones from Parts Express and Zalytron at about $5 each IIRC.

BTW, there is a week old thread on this forum for a group buy on a gainclone amp at $50 exclusive of tranny, chassis and hardware.

George
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Old 1st March 2004, 04:50 AM   #140
tcpip is offline tcpip  India
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Quote:
Originally posted by gjo
What do the square terminals cost? Do they have a hole to insert bananas and then allow you to tighten the nut? I bought similar ones from Parts Express and Zalytron at about $5 each IIRC.
They have a hole for the banana plug, but no mechanism to tighten the grip on it afterwards. The whole square thing cost me Rs.125; I'd mentioned it earlier, I think.

Quote:
BTW, there is a week old thread on this forum for a group buy on a gainclone amp at $50 exclusive of tranny, chassis and hardware.
Yes, I saw it. The PCB was designed in a way which I'm not comfortable with. There are no mounting holes. What makes it worse is that the designer has made space for large and (I presume) heavy caps on the board. The entire board is expected to stay suspended in space on just the solder joints of the LM chip. This is very naive. One member has pointed this out, and the designer has added a mounting hole somewhere in the "centre"; I didn't bother to look.

Personally, after doing some armchair studying of the gainclone chip and circuit, the only way I think such a circuit will be secure and reliable will be if
  • the PCB is clamped to the heatsink with two L-brackets of the kind I'm using for my P3A above, and
  • a metal bar is clamped across the chip, pressing it down on the heatsink. These chips simply do not press against the heatsink enough if you just use that one bolt on the top, and this fault increases their temperature, and that's when their super-sensitive SPIKE protection kicks in, making the sound audibly worse.
I can't figure out how designers who want to extract the maximum quality out of these chips just use one top-mounted bolt to press the chip against the heatsink.

I'm trying to design my own PCB for the Gainclone; I can always get my own PCB made using the resources I've discovered so far, and the handful of passives that the Chip Amp fans seem to like (Rifa caps, Black Gates, etc) are not the ones I'd spend my money on at this stage anyway. Therefore, I think I'll be happier going my own way. I have obtained an Eagle library device definition for the LM3875 done by someone else. I've added a guard area around the device to keep space for a clamping bar and bolts. And I've designed a PCB for it with mounting holes. If you want to see the board layout, let me know.
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