C0G caps
While building the Rod Elliott amp, I once encountered one ceramic cap of 500V rating. I don't know why he asked for such a high rating... I've written to him, asking him. Is this in any way related to the stability requirements of the Miller cap? Since I don't understand any of these things of amp design, I'm totally lost.
Is this grade of cap easily available elsewhere? I saw it on the RS India Website after reading your post (check stock numbers 211 4971 and 264 4652), but don't know how much they'll charge. They have good metal oxide film power resistors for Rs.9 (2W) and Rs.16 (3W) each... these prices compare well with prices abroad, so not everything is untouchable. Does C0G cap imply 5% tolerance? Wherever I've seen them, they seem to have this tolerance. Does X7R mean 10% tolerance? Do we need to bother about these differences in audio circuits (not the tolerance, but the tempco).roadkill said:
While building the Rod Elliott amp, I once encountered one ceramic cap of 500V rating. I don't know why he asked for such a high rating... I've written to him, asking him. Is this in any way related to the stability requirements of the Miller cap? Since I don't understand any of these things of amp design, I'm totally lost.
Great going guys...
true to the nick 'tcpip', tarun this has really expanded into a network...and great support from others...
i wish i could contribute...no excuses though...
here are bits and pieces of information i could gather..
Corrson:
Ok for all those interested here's the list of drivers that corrson stocks...
P17WJ00-08
TC14WG49-08
TC18WG49-08
D27AG05-06
D25AG35-06
D25ASG35
Please refrain yourselves from ordering anything now
there has been minor hickups, Vivek and myself are getting it sorted out...will keep u posted of the developments.
Regarding enclosures:
Would it be possible to get enclosures done from these readymade aluminium channels available. If possible i'll try drafting some designs. I think it can be done. I have trouble approaching these aluminium fabricators. Language problem for i dont understand the local language and it goes real crazy...
And am sure we can locate some anodizers and powder coaters...some of them are there along NH7 and should be in plenty in other industrial estates like peenya and all. IF some one who knows the local language can accompany me, probably we can go knocking at those doors.
There are two agencies one is called arrow electronics..i dont remember the exact names, will have to dig up some old business-cards. We used to get all exotic components like some dacs, recievers, opamps etc thru these ppl and another lot from universal. It seems there are couple of shops in SP road which sells stuff like crystal SPDIF recievers, ADI DACs, ADC's, FPGA'a, OMRON relays etc. will find out the details.
For boards, in small quanities there is this place called Hi-Q, they can make u any kind of board...If we plan to have a group buy probably we can consider this option. They are heavily mechanised and 'pricey' but can get those boards done to whatever specs...6 or 8 mil tracks, SOIC's TQFP anything, single to multilayer burried vias...all kinds of them...They used to do PCB prototyping for us. But is not an economic option for small quanities..say one or two boards. TQFP and other fine pitch component soldering is very difficult to be executed manually.and that too by a soldering iron.especially resoldering...first of all the pins are too fragile and close...there is this place called peninsula Electronics who used to do the assmbly...U give them the bom and they do the rest...!Again not a viable option if its not 20 -50 boards...But i'll try to get the details from them. Our requirements(at work) always used to be some high end boards, but still in small quantities..thats y i am sure that these guys can take small orders...but will it balance the overheads involved is something to be looked at.
Ok
i really want to try out the ensloures using Aluminium channels and acrylic. If any one from bangalore has any leads on this please let me know. I've a feeling that the kind of enclosures etc we are looking at, can be easily done by basic machines. Probably the requirement for the numeric controlled species can easily be done away with and roadkill can save his job
what say ppl..?
On Sjp Road, there is a place that sells copper and brass bars. In case some one wants to try something really exotic with these...
And i'm really sorry for the wholly disorganised post..had to hurry
Thanks
ajju.
true to the nick 'tcpip', tarun this has really expanded into a network...and great support from others...
i wish i could contribute...no excuses though...
here are bits and pieces of information i could gather..
Corrson:
Ok for all those interested here's the list of drivers that corrson stocks...
P17WJ00-08
TC14WG49-08
TC18WG49-08
D27AG05-06
D25AG35-06
D25ASG35
Please refrain yourselves from ordering anything now there has been minor hickups, Vivek and myself are getting it sorted out...will keep u posted of the developments.
Regarding enclosures:
Would it be possible to get enclosures done from these readymade aluminium channels available. If possible i'll try drafting some designs. I think it can be done. I have trouble approaching these aluminium fabricators. Language problem for i dont understand the local language and it goes real crazy...
And am sure we can locate some anodizers and powder coaters...some of them are there along NH7 and should be in plenty in other industrial estates like peenya and all. IF some one who knows the local language can accompany me, probably we can go knocking at those doors.
There are two agencies one is called arrow electronics..i dont remember the exact names, will have to dig up some old business-cards. We used to get all exotic components like some dacs, recievers, opamps etc thru these ppl and another lot from universal. It seems there are couple of shops in SP road which sells stuff like crystal SPDIF recievers, ADI DACs, ADC's, FPGA'a, OMRON relays etc. will find out the details.
For boards, in small quanities there is this place called Hi-Q, they can make u any kind of board...If we plan to have a group buy probably we can consider this option. They are heavily mechanised and 'pricey' but can get those boards done to whatever specs...6 or 8 mil tracks, SOIC's TQFP anything, single to multilayer burried vias...all kinds of them...They used to do PCB prototyping for us. But is not an economic option for small quanities..say one or two boards. TQFP and other fine pitch component soldering is very difficult to be executed manually.and that too by a soldering iron.especially resoldering...first of all the pins are too fragile and close...there is this place called peninsula Electronics who used to do the assmbly...U give them the bom and they do the rest...!Again not a viable option if its not 20 -50 boards...But i'll try to get the details from them. Our requirements(at work) always used to be some high end boards, but still in small quantities..thats y i am sure that these guys can take small orders...but will it balance the overheads involved is something to be looked at.
Ok
i really want to try out the ensloures using Aluminium channels and acrylic. If any one from bangalore has any leads on this please let me know. I've a feeling that the kind of enclosures etc we are looking at, can be easily done by basic machines. Probably the requirement for the numeric controlled species can easily be done away with and roadkill can save his job
what say ppl..?
On Sjp Road, there is a place that sells copper and brass bars. In case some one wants to try something really exotic with these...
And i'm really sorry for the wholly disorganised post..had to hurry
Thanks
ajju.
C0G caps: the advantage these provide over "normal" X7R/Y5V/Z5U caps is that the capacitance does not vary with the following:
1) humidity
2) temperature
3) applied DC bias
4) soldering temperature
This usually matters in RF circuits and where the absolute capacitance is important. It's useful in an audio context mostly for Miller compensation caps and for active filters (which is what I'm using them for). The effect of the capacitance varying with applied voltage is thought to be one cause of "capacitor sound". They all come in 5% tolerance (see SMDin's website). Unfortunately, they aren't available in values greater than about 10 nF. Beyond that, film caps are probably the best bet. I remember I had this delusion that someone on Lamington road will stock 5% and 1% film caps, and getting laughed out of every shop! Tempco matters most when the caps are used in active filters. Some filter topologies (I believe the Linkwitz is one of them) are very sensitive to component tolerance, so the response can go crazy as the temp changes. With miller caps, usually the values are chosen a bit bigger than that required to stabilize an amp (for a better phase margin), so temperature-induced variation shouldn't matter too much. Still, you can counter that argument with "why take a chance?"
I'm not quite sure why Mr. Elliot wants you to use a 500V cap. Maybe he meant mica caps, which I've not been able to locate anywhere. Best I could find are polystyrene caps (available at Universal), which I used for Miller compensating a MOSFET power amp. MOSFETs used are IRFP240/IRFP9240, available at Chandan Electronics (opposite Vishal Electronics, I believe there is another shop called Chandan). Cost me a pretty penny (400 bucks a pair).
Tarun, the IEC sockets I bought incorporate an EMI filter as well as a fuse holder. They're quite big, encased in metal for shielding. This should filter out junk on the power lines if it has a good earth connection. They're from Elcom, and cost quite a bit (~Rs. 120). I bought them from Mumbai, "Precious Electronics" (a Tolkein fan, maybe?)
PCBs: the laser print to bromide method is what my PCB guy uses. He returns the bromides too. I wonder if it really makes a diff if it's on normal A4 copier paper or on butter paper.
My circuits: No, these aren't from Elektor, they're the result of browsing through Analog Devices website. They have this amazing device called the AD1954 SigmaDSP: a DSP core with a pre-programmed ROM to implement a 7-band EQ, compressor (good when watching DVDs at night), volume, subwoofer crossover and de-emphasis. It takes in left-justified, right-justified or I2S data, and includes three DACs for left, right and sub. I'm using two of these to implement a 4.1 system. Wish I could attach an image of the board, but it's huge (needs at least 200 dpi when exporting from Eagle to differentiate b/w the tracks and the ground plane). And in case you're wondering, I got the chips from ADI as samples. I mailed the ADI sales rep asking if I'd be able to buy two for prototyping, he said ask for samples. In hindsight, I wish I could have got a more general purpose DSP like the SHARC. I use them at work, so I have all the programming tools. Anyway, the sample rate converter is an AD1892 with an SPDIF input. I plan to run the input to my sound card (SB Live, which can put out all six channels as independent SPDIF signals).
ajju, I'm interested in finding out about DACs, if you have any leads, pass them on. Arrow probably has an MOQ, so we could order together to beat that? I'm also considering an "Elektor-style" cabinet (refer the covers of issues where they present the Crescendo), the case side walls are made of extrusions with front, back, top and bottom bolted on. I've already bought the extrusions from Shri Maruthi Metals (lead provided by Ashwin, thanks!). At my old workplace, we used to give Hi-Q 8 layer boards with BGAs. They can do it, but the costs wll be high. We used to give them prototype boards (ie, just two boards), so quantity is not a problem. If I remember right, the quote for a production run of two 8-layer cPCI sized boards (230x166 mm) was Rs. 12000. This included impedance control, silkscreening, 6 mil tracks... we won't need that kinda stuff, so I'm guessing a two layer non-impedance-controlled, masked board would be ~ Rs. 2k. The tech assistant at work solders TQFPs like he's been doing it since childhood... I guess if the board is soldermasked, it's not so hard. See Numbnut's guide to soldering (funny!) One thing he uses which I've not been able to find is very fine desolder braid. I can add a step to his guide, to coat the pads with liquid soldering flux. Helps if the board is dirty.
Don't know how many of you will be interested by this... Ankit Corporation stocks graphic LCDs which don't have any onboard controllers. They're big, and fairly cheap. I bought a 240x64 display with an EL backlight for Rs. 700. However, you have to make the controller yourself. Initially, I was hoping to use a CPLD, but gave up when I couldn't find one (help, anyone?). I later programmed an Atmel MCU to do this, and it works fine. The MCU also does some processing, so it can receive commands to draw lines, boxes, text, etc, not a string of "put pixel here" commands. If anyone's interested, I can send them the circuit used, including PCB layout. I will be using this in an amp (no, I'm not crazy!)
I have a doubt: what are "Neutrik Speakon" connectors used for? I'm guessing for speakers...
I use binding posts from MX, which come in a round plastic cup. Gold flashed, seem to be of reasonable quality, 50 bucks each.
Apologies for the size of this post.
1) humidity
2) temperature
3) applied DC bias
4) soldering temperature
This usually matters in RF circuits and where the absolute capacitance is important. It's useful in an audio context mostly for Miller compensation caps and for active filters (which is what I'm using them for). The effect of the capacitance varying with applied voltage is thought to be one cause of "capacitor sound". They all come in 5% tolerance (see SMDin's website). Unfortunately, they aren't available in values greater than about 10 nF. Beyond that, film caps are probably the best bet. I remember I had this delusion that someone on Lamington road will stock 5% and 1% film caps, and getting laughed out of every shop! Tempco matters most when the caps are used in active filters. Some filter topologies (I believe the Linkwitz is one of them) are very sensitive to component tolerance, so the response can go crazy as the temp changes. With miller caps, usually the values are chosen a bit bigger than that required to stabilize an amp (for a better phase margin), so temperature-induced variation shouldn't matter too much. Still, you can counter that argument with "why take a chance?"
I'm not quite sure why Mr. Elliot wants you to use a 500V cap. Maybe he meant mica caps, which I've not been able to locate anywhere. Best I could find are polystyrene caps (available at Universal), which I used for Miller compensating a MOSFET power amp. MOSFETs used are IRFP240/IRFP9240, available at Chandan Electronics (opposite Vishal Electronics, I believe there is another shop called Chandan). Cost me a pretty penny (400 bucks a pair).
Tarun, the IEC sockets I bought incorporate an EMI filter as well as a fuse holder. They're quite big, encased in metal for shielding. This should filter out junk on the power lines if it has a good earth connection. They're from Elcom, and cost quite a bit (~Rs. 120). I bought them from Mumbai, "Precious Electronics" (a Tolkein fan, maybe?
)PCBs: the laser print to bromide method is what my PCB guy uses. He returns the bromides too. I wonder if it really makes a diff if it's on normal A4 copier paper or on butter paper.
My circuits: No, these aren't from Elektor, they're the result of browsing through Analog Devices website. They have this amazing device called the AD1954 SigmaDSP: a DSP core with a pre-programmed ROM to implement a 7-band EQ, compressor (good when watching DVDs at night), volume, subwoofer crossover and de-emphasis. It takes in left-justified, right-justified or I2S data, and includes three DACs for left, right and sub. I'm using two of these to implement a 4.1 system. Wish I could attach an image of the board, but it's huge (needs at least 200 dpi when exporting from Eagle to differentiate b/w the tracks and the ground plane). And in case you're wondering, I got the chips from ADI as samples. I mailed the ADI sales rep asking if I'd be able to buy two for prototyping, he said ask for samples. In hindsight, I wish I could have got a more general purpose DSP like the SHARC. I use them at work, so I have all the programming tools. Anyway, the sample rate converter is an AD1892 with an SPDIF input. I plan to run the input to my sound card (SB Live, which can put out all six channels as independent SPDIF signals).
ajju, I'm interested in finding out about DACs, if you have any leads, pass them on. Arrow probably has an MOQ, so we could order together to beat that? I'm also considering an "Elektor-style" cabinet (refer the covers of issues where they present the Crescendo), the case side walls are made of extrusions with front, back, top and bottom bolted on. I've already bought the extrusions from Shri Maruthi Metals (lead provided by Ashwin, thanks!). At my old workplace, we used to give Hi-Q 8 layer boards with BGAs. They can do it, but the costs wll be high. We used to give them prototype boards (ie, just two boards), so quantity is not a problem. If I remember right, the quote for a production run of two 8-layer cPCI sized boards (230x166 mm) was Rs. 12000. This included impedance control, silkscreening, 6 mil tracks... we won't need that kinda stuff, so I'm guessing a two layer non-impedance-controlled, masked board would be ~ Rs. 2k. The tech assistant at work solders TQFPs like he's been doing it since childhood... I guess if the board is soldermasked, it's not so hard. See Numbnut's guide to soldering (funny!) One thing he uses which I've not been able to find is very fine desolder braid. I can add a step to his guide, to coat the pads with liquid soldering flux. Helps if the board is dirty.
Don't know how many of you will be interested by this... Ankit Corporation stocks graphic LCDs which don't have any onboard controllers. They're big, and fairly cheap. I bought a 240x64 display with an EL backlight for Rs. 700. However, you have to make the controller yourself. Initially, I was hoping to use a CPLD, but gave up when I couldn't find one (help, anyone?). I later programmed an Atmel MCU to do this, and it works fine. The MCU also does some processing, so it can receive commands to draw lines, boxes, text, etc, not a string of "put pixel here" commands. If anyone's interested, I can send them the circuit used, including PCB layout. I will be using this in an amp (no, I'm not crazy!)
I have a doubt: what are "Neutrik Speakon" connectors used for? I'm guessing for speakers...
I use binding posts from MX, which come in a round plastic cup. Gold flashed, seem to be of reasonable quality, 50 bucks each.Apologies for the size of this post.
Neutrik Speakons
Roadkill,
Yes, u're right, for speakers and amps. This is a live sound connector, that facilitates a more convenient way to jack up the hi current speaker terminals so that it saves time with live sound installation. Very revolutionary new plug. I used binding posts earlier, and work OK and I still use them for my DIY pro-audio gear in my living room but like I said again live sound is a bit different.
Patrick
Roadkill,
Yes, u're right, for speakers and amps. This is a live sound connector, that facilitates a more convenient way to jack up the hi current speaker terminals so that it saves time with live sound installation. Very revolutionary new plug. I used binding posts earlier, and work OK and I still use them for my DIY pro-audio gear in my living room but like I said again live sound is a bit different.
Patrick
COG caps
The stability of the capacitance with applied voltage is the biggest advantage of COG caps when used as VAS compensation. The modulation of the miller capacitance is minimized thus reducing distortion.
Some times a cascode stage is added to the VAS stage to do the same thing.
Angshu
The stability of the capacitance with applied voltage is the biggest advantage of COG caps when used as VAS compensation. The modulation of the miller capacitance is minimized thus reducing distortion.
Some times a cascode stage is added to the VAS stage to do the same thing.
Angshu
Rod Elliott's high-voltage ceramic cap
I got Rod's answer. He says that it's well known that a ceramic cap goes non-linear when it approaches its voltage rating, let alone exceed it. So, using a ceramic cap of very high voltage rating keeps the cap well within its linear range. And he finished by saying that if I can find it, I should use polystyrene: "still by far the best (IMO)."
How easy or difficult is it to find polystyrene caps of, say 100V rating and small values?
Tarun
I got Rod's answer. He says that it's well known that a ceramic cap goes non-linear when it approaches its voltage rating, let alone exceed it. So, using a ceramic cap of very high voltage rating keeps the cap well within its linear range. And he finished by saying that if I can find it, I should use polystyrene: "still by far the best (IMO)."
How easy or difficult is it to find polystyrene caps of, say 100V rating and small values?
Tarun
Speakons
I found quite a few other connectors which have these properties on the RS site. I'm thinking of using some of the cheaper varieties of these to connect an outboard power transformer to multiple amp chassis. Lowish voltage (+/-50V), high current, low contact impedance, high reliability, no accidental disconnection, and three cores in one plug. Very handy, I thought.
Me too. But normal binding posts either have no locking mechanism (banana plugs) or have locking but can't be easily plugged in or removed (spade connectors fixed by screws). As far as I can make out, Speakons and other similar connectors have the following features:roadkill said:I have a doubt: what are "Neutrik Speakon" connectors used for? I'm guessing for speakers...
- High current rating (16A or more): good enough for speakers
- Very low impedance: less than 100mOhms. Good for low voltage high-current apps
- Locking of some form: no accidental disconnection
- Easy plugging and unplugging without any unscrewing, shorting, etc
- Usually, for 3-pole connectors, the earth connection is made before the other connections, so that you can plug and unplug safely when it's live
- Insulating body (which most banana plugs don't have)
I found quite a few other connectors which have these properties on the RS site. I'm thinking of using some of the cheaper varieties of these to connect an outboard power transformer to multiple amp chassis. Lowish voltage (+/-50V), high current, low contact impedance, high reliability, no accidental disconnection, and three cores in one plug. Very handy, I thought.
Interesting posts guys, kdeep it up. I am also interested in some things..MRF Vapocure guy ,Kaveri Coats (P) Ltd near Lingarajapuram did a nice wrinkly coating for my AKSA enclosure, looks better than powder coating. This guy is an expert and does some cars for Vijay Mallya, BTW!.
Tarun I will also be interested in some knobs. Plan to upgrade my new tube preamp volume control to a Noble stepped one, may need a decent knob. Once you get your set, let us know the quantities and pricing with the photo.
I am interested in a source for tubes, I plan to get a spare matched quad of Svetlana EL 34s next month from the US, for my power amp but if these are locally available, then I may want to look at it.
George
Tarun I will also be interested in some knobs. Plan to upgrade my new tube preamp volume control to a Noble stepped one, may need a decent knob. Once you get your set, let us know the quantities and pricing with the photo.
I am interested in a source for tubes, I plan to get a spare matched quad of Svetlana EL 34s next month from the US, for my power amp but if these are locally available, then I may want to look at it.
George
About Neutrik Speakons
patrick
Yes exactly...... sorry if I forgot to mention the locking feature which is the main reason wy I use Speakons in the first place. For DIY audio at home I still use MX binding posts because I don't remove them every 24 hours. But I need to carry that convenience in all my homebrewed poweramps for 'live' use.That way my people don't just pull of the wires after an event and a hard days work as they normally do now.
patrick
Tarun,
Rod's answer holds good for electrolytics, mostly. Ceramic caps with Y5V dielectric (most common for values > 47nF) change capacitance dramatically with applied voltage, causing distortion. With electrolytics, there must be a DC bias, and if the applied bias is not within around 40% of the capacitor rating, the value will be out of tolerance. This is particularly bad considering elcos usually have tolerances like +80%,-20%. Film capacitors do not suffer from nonlinearity effects, but they do suffer from parasitic inductance. This is not a very observable effect for audio, but makes itself known at RF or in high-speed digital ckts.
The point you mentioned about Speakon connectors making ground contact before signal is irrelevant when it comes to speakers. You shouldn't attach/remove connectors which carry very heavy currents when powered up, because arcing can corrode the contacts. Besides, what if your amp output stage is BTL? This really makes a diff for signal contacts. RCA jacks were probably designed by someone more inclined to cost cutting, since they deliberately make signal contact before ground
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.
OK, I got my DSP board back today, and it was a bit of a disappointment... many tracks had shorts to the ground plane
. I had a "cure" for this: I got me a 12AH lead acid battery, hooked it to the ground plane and burnt out the shorted sections! 
Some of the soldermask got damaged, so I touched it up with nailpolish (who here can get me green nail polish? 
). Maybe I was being over-ambitious, I had set the ground plane polygon's spacing to 10 mil... I later found that even 15 mil would have worked fine. Silly me. 
Anyway, next time you guys make a PCB with a plane, you know what not to set the spacing to... Other than that, the TQFP pads have formed quite well, no shorts there.
Rod's answer holds good for electrolytics, mostly. Ceramic caps with Y5V dielectric (most common for values > 47nF) change capacitance dramatically with applied voltage, causing distortion. With electrolytics, there must be a DC bias, and if the applied bias is not within around 40% of the capacitor rating, the value will be out of tolerance. This is particularly bad considering elcos usually have tolerances like +80%,-20%. Film capacitors do not suffer from nonlinearity effects, but they do suffer from parasitic inductance. This is not a very observable effect for audio, but makes itself known at RF or in high-speed digital ckts.
The point you mentioned about Speakon connectors making ground contact before signal is irrelevant when it comes to speakers. You shouldn't attach/remove connectors which carry very heavy currents when powered up, because arcing can corrode the contacts. Besides, what if your amp output stage is BTL? This really makes a diff for signal contacts. RCA jacks were probably designed by someone more inclined to cost cutting, since they deliberately make signal contact before ground
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.
OK, I got my DSP board back today, and it was a bit of a disappointment... many tracks had shorts to the ground plane
. I had a "cure" for this: I got me a 12AH lead acid battery, hooked it to the ground plane and burnt out the shorted sections! Some of the soldermask got damaged, so I touched it up with nailpolish (who here can get me green nail polish? ). Maybe I was being over-ambitious, I had set the ground plane polygon's spacing to 10 mil... I later found that even 15 mil would have worked fine. Silly me. Anyway, next time you guys make a PCB with a plane, you know what not to set the spacing to... Other than that, the TQFP pads have formed quite well, no shorts there.Polysterene caps
Hello 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
Hello Tarun,
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
Re: Polysterene caps, knobs, AKSA amps...
And Patrick:
Tarun
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.gjo said:
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:
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
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...
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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About POlyester and polyesterene caps
Hello all
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
Hello all
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
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.
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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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
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
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.gjo said:
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'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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