Dear Hugh,
Yes it possible to mark the components as well as polarities. I will be out from my home town for next few days. I will be in touch but it will be possible only on return to complete the artwork.
Thanks on Irfan view. I have it downloaded. Trying out its various features.
Regards
Rahul
Yes it possible to mark the components as well as polarities. I will be out from my home town for next few days. I will be in touch but it will be possible only on return to complete the artwork.
Thanks on Irfan view. I have it downloaded. Trying out its various features.
Regards
Rahul
Interesting thread about fake OPS devices
Since we've talked about this at some point on this thread, I thought I'd point you guys to another thread specifically discussing this issue. It seems that many people in many parts of the world are relating experiences, thus indicating that this is not an issue with L.Road or Lucknow alone. Also, there are interesting comments about how the fakes differ from the real ones, and how to detect one from the other. Check this thread. The interesting thing for me in all these discussions is that the fakes don't just mimic the external appearance... they actually have a reduced-rating but fully functional device inside. In other words, they may work at lower Vceo or lower Ic, but will burn at even half the rating of the original device. Hence, just saying "Everyone is using these devices hence they are originals" does not hold water. One must see under what circuit conditions the devices are being used.
Since we've talked about this at some point on this thread, I thought I'd point you guys to another thread specifically discussing this issue. It seems that many people in many parts of the world are relating experiences, thus indicating that this is not an issue with L.Road or Lucknow alone. Also, there are interesting comments about how the fakes differ from the real ones, and how to detect one from the other. Check this thread. The interesting thing for me in all these discussions is that the fakes don't just mimic the external appearance... they actually have a reduced-rating but fully functional device inside. In other words, they may work at lower Vceo or lower Ic, but will burn at even half the rating of the original device. Hence, just saying "Everyone is using these devices hence they are originals" does not hold water. One must see under what circuit conditions the devices are being used.
Yes, I am surprised there have been no recent posts. This thread usually is at the top of the list always. Perhaps the fiery pace with which our guys have been working is proving to be too much. 
Come on boys, what's the latest?
Vivek
Come on boys, what's the latest?
Vivek
Sorry friends,
I was out of town. Tarun I am sorry could not contact you at Mumbai, the visit was just too hectic. Will be coming again next month.
Hugh and others I will be feeding the component markings and hope to have the Final version of board ready by tomorrow. BTW I have managed to get the connectors for power connection similar to ones used in AKSA in a shop opposite to Precious at L Road.
I will be making a few boards less the legends for test before getting it made for all.
Ashok I remember you had few OP devices from your sample stock. How abt making a good use of them now.
Regards
Rahul
I was out of town. Tarun I am sorry could not contact you at Mumbai, the visit was just too hectic. Will be coming again next month.
Hugh and others I will be feeding the component markings and hope to have the Final version of board ready by tomorrow. BTW I have managed to get the connectors for power connection similar to ones used in AKSA in a shop opposite to Precious at L Road.
I will be making a few boards less the legends for test before getting it made for all.
Ashok I remember you had few OP devices from your sample stock. How abt making a good use of them now.
Regards
Rahul
This is great news. I was looking for them too. I'll go take a walk down that bylane where Precious occupies their first-floor premises... Anyway, I want to check with Precious about original Bourns 3296 trimpots and original Phoenix screw-type terminals.Rahul said:
BTW, Rahul, why don't you too switch from those long sidewinder-type multi-turn pots to the Bourns vertical ones for your design?
And in the time while I was away, Angshu has gone to B'lore and picked up a pair of Vifa D27 tweeters for me from Corrson, and I've gone to Delhi and picked them up from him! 😀
If only I could make something with all this now... 😀
HI!
Tarun :
In fact this shop is just below Precious as you approach the staircase to Precious, this is the front corner shop at right. Something with k.The spade cost 0.60Rs and connector ).65Rs each. Not to worry about procurements I have bought enough for this project This I plan to offer free with the JLH PCBs. After all this whole project
is for friends.
Now Suranjan told me he is aware of of the YP products .
On way to mumbai I also spent some time at Delhi, as mentioned earlier my friends at YP have given me a pair of domes for testing. It probably costs 125 each. Say 250 a pair..
Perhaps he may provide us with something much better specs for the same cost.
In his esteemed opinion these drivers are copied in 1-10K figures in easter
Strill working on the board tomorrow come it will be there parts of our country alone
Tarun :
In fact this shop is just below Precious as you approach the staircase to Precious, this is the front corner shop at right. Something with k.The spade cost 0.60Rs and connector ).65Rs each. Not to worry about procurements I have bought enough for this project This I plan to offer free with the JLH PCBs. After all this whole project
is for friends.
Now Suranjan told me he is aware of of the YP products .
On way to mumbai I also spent some time at Delhi, as mentioned earlier my friends at YP have given me a pair of domes for testing. It probably costs 125 each. Say 250 a pair..
Perhaps he may provide us with something much better specs for the same cost.
In his esteemed opinion these drivers are copied in 1-10K figures in easter
Strill working on the board tomorrow come it will be there parts of our country alone
De-thump and protection
Hello everybody,
I read the thread just yesterday and couldn't resist going through...
DIY India is going to spend lot of money on the Elex and Drivers.
In order to protect the speakers, what I feel is that you should have a temperature sensing on your o/p Qs.
If you come out of the analog world & go to digital, a dethump cum protection ckt can be made from a purpose designed CMOS timer ic.
The ic number is 4541 and I suppose one of u should be able to find out how
The ic has a power on reset facility and the thermistor with a small ckt, may be around LM 339 or even 555 can be made to control the ic in turn puting off the de-thump relay(s).
However you will have to use a seperate recifier/filter for the IC. It can even be half wave.
I have some NTCs. The device is fitted inside a Lug(instead of the wire) and was originally fitted on to the power Q body like a washer, by an Int'l mfr
Take it or ignore it...
Gajanan Phadte
_____________________________________________
This project is too late for me, but I still want to assemble a Class A.
Hello everybody,
I read the thread just yesterday and couldn't resist going through...
DIY India is going to spend lot of money on the Elex and Drivers.
In order to protect the speakers, what I feel is that you should have a temperature sensing on your o/p Qs.
If you come out of the analog world & go to digital, a dethump cum protection ckt can be made from a purpose designed CMOS timer ic.
The ic number is 4541 and I suppose one of u should be able to find out how
The ic has a power on reset facility and the thermistor with a small ckt, may be around LM 339 or even 555 can be made to control the ic in turn puting off the de-thump relay(s).
However you will have to use a seperate recifier/filter for the IC. It can even be half wave.
I have some NTCs. The device is fitted inside a Lug(instead of the wire) and was originally fitted on to the power Q body like a washer, by an Int'l mfr
Take it or ignore it...
Gajanan Phadte
_____________________________________________
This project is too late for me, but I still want to assemble a Class A.
Dear Gajanan,
Thanks for the suggestion. Rather than going active I have seen thermal switches available in mkt that operate at 60deg C. We can simply bolt them on heatsink and operate a relay to switch of the supply. Anyway we still have options open for protective circuitry.
In fact we have just finalised the design selection we all have much to do before we hear the sweet sound of JLH. You are most welcome in this project.
Sorry it took some time to wind off pending work, the final PCB layout I will be uploading in a day or two.
Regards
Rahul
Thanks for the suggestion. Rather than going active I have seen thermal switches available in mkt that operate at 60deg C. We can simply bolt them on heatsink and operate a relay to switch of the supply. Anyway we still have options open for protective circuitry.
In fact we have just finalised the design selection we all have much to do before we hear the sweet sound of JLH. You are most welcome in this project.
Sorry it took some time to wind off pending work, the final PCB layout I will be uploading in a day or two.
Regards
Rahul
sweet sound
All u must be very eager to hear the end product, the sweet sound.
We will not discuss these auxilliary circuits. But a word of caution
60 deg +/- ?
Happy Class A amping.
i will keep an eye on the proceedings
Regards and best of luck.
gajanan
All u must be very eager to hear the end product, the sweet sound.
We will not discuss these auxilliary circuits. But a word of caution
60 deg +/- ?
Happy Class A amping.
i will keep an eye on the proceedings
Regards and best of luck.
gajanan
What kind of thermal switch are these? Do they have a reset button? Personally, I feel the ones without reset buttons are simply easier to use, and just as useful. I'd love to get something similar to these Cantherm switches. They're simple, rugged, need no power supply, can switch a few amperes of current, and just keep on working. Don't know whether they're available in India easily. You also get these other types which are probably better; they switch larger currents.Rahul said:
Many of us don't consider over-temperature protection necessary for Class B amps, but maybe they should be considered essential for Class A.
Another thing: we probably missed one point Hugh Dean was trying to make earlier, about protection strategies. He said that OPS devices are cheaper than speaker drivers, so we can afford to keep OPS stages unprotected against over-current, as long as we are careful to protect speakers. If we adopt this strategy, we must add some sort of DC protection for the speaker. This may become even more critical in Class A amps, where OPS failure due to BJT thermal runaway may be more of an issue than Class B. Any plans about what to do about this? I have a simple circuit in Randy Slone's book which uses some diodes plus a cap to detect DC at the output, and then triggers a relay. Some people don't like speaker output passing through a relay's contacts, but for those of us who don't mind it, this may be a good idea. What say?
Of course, this is independent of what you're doing on the basic amp PCB. These protection things can be added as a separate PCB.
Got the connectors! Thanks, Rahul and Hugh, for pointing this approach out to us.Rahul said:
They're freely available in Champion Rubber Stores, in various sizes (I bought 6.3mm). You get packets of 100 of these for Rs.50. They seem to be silver-plated brass. You also get 100 of the female cable-mounted counterparts for the same price, in packs of 100. The plastic covers for the cable-mounted jacks are Rs.30 for a pack of a hundred. I'll switch to them now.
Hi!
Tarun:
It appears you got a better deal and rubber covers too. I will also buy them on my next visit.
It is similar bi-metal switches I was referring to. I saw them at one of the shops , probably one that sells PICs and Textool 3M ZIF sockets. Cost was Rs60/ quite reasonable one can easily switch off amp supply thru a relay.
One of my friend has a unit that manufacturers Photographic enlargers. Since most of his components are made of aluminium he buys lot of scrap. Often he gets good heatsinks from scrapped equipments, this is ultimately melted in furnace. He has promised to arrange some good heatsinks. Lets hope we get lucky.
BTW tomorrow Mandira Bedi is paying us a visit for a product launch. Lately I had been busy with the arrangements. Tomorrow pass and things will be back at normal pace.
I am sure all my friends would bear with me for the delay.
Regards
Rahul
Tarun:
It appears you got a better deal and rubber covers too. I will also buy them on my next visit.
It is similar bi-metal switches I was referring to. I saw them at one of the shops , probably one that sells PICs and Textool 3M ZIF sockets. Cost was Rs60/ quite reasonable one can easily switch off amp supply thru a relay.
One of my friend has a unit that manufacturers Photographic enlargers. Since most of his components are made of aluminium he buys lot of scrap. Often he gets good heatsinks from scrapped equipments, this is ultimately melted in furnace. He has promised to arrange some good heatsinks. Lets hope we get lucky.
BTW tomorrow Mandira Bedi is paying us a visit for a product launch. Lately I had been busy with the arrangements. Tomorrow pass and things will be back at normal pace.
I am sure all my friends would bear with me for the delay.
Regards
Rahul
I didn't actually buy the rubber covers. And I can always buy and send you the stuff if you want.Rahul said:
Where did you see these switches? I can feel another trudge through those bylanes coming up.... sigh.
I've seen thermal fuses on earlier visits to L.Road. These are freely available and quite inexpensive, but of course they're less useful than reusable cutouts/switches.
Sorry Tarun I do not remember the shop name. Near to this shop was another one that had lot of cooling fans in all shapes and sizes.
I hope this will be of some help.
Regards
Rahul
I hope this will be of some help.
Regards
Rahul
Hi Rahul, Tcpip, et al,
It is interesting to see the thinking of Graham Maynard, a talented designer who wrote in this thread on an amp for 1R loads:
Graham Maynard's Swedish Circuit
You'll need to scroll down the page, almost to the bottom.
This is a Bengt Olssen 'development' of JLH's circuit for mosfets, and something to consider for you guys. It does not appear to be fully Class A.
The problem with JLH's original circuit is the limited power for real world speakers. As a rule, when you are designing for Class A you need hugely robust output devices to cope with the high dissipations, particularly in a hot climate. A mosfet has many problems in Class AB, but is the best choice for Class A because of its incredible thermal toughness and suitability for capacitive loading, and this is something to consider because I would contend that it would sound just as good as the JLH bipolar circuit. I have designed a SE amp using mosfets which dissipates no less than 38W per device (125W IRF150). I built ten monoblocks, and with simple convection cooling, these devices have never failed and will drive purely capacitive loads, such as ESLs. I doubt that bipolars could handle this abuse...
Cheers,
Hugh
It is interesting to see the thinking of Graham Maynard, a talented designer who wrote in this thread on an amp for 1R loads:
Graham Maynard's Swedish Circuit
You'll need to scroll down the page, almost to the bottom.
This is a Bengt Olssen 'development' of JLH's circuit for mosfets, and something to consider for you guys. It does not appear to be fully Class A.
The problem with JLH's original circuit is the limited power for real world speakers. As a rule, when you are designing for Class A you need hugely robust output devices to cope with the high dissipations, particularly in a hot climate. A mosfet has many problems in Class AB, but is the best choice for Class A because of its incredible thermal toughness and suitability for capacitive loading, and this is something to consider because I would contend that it would sound just as good as the JLH bipolar circuit. I have designed a SE amp using mosfets which dissipates no less than 38W per device (125W IRF150). I built ten monoblocks, and with simple convection cooling, these devices have never failed and will drive purely capacitive loads, such as ESLs. I doubt that bipolars could handle this abuse...
Cheers,
Hugh
Bhai log...kahan ho aap sub??
It seems the past month or so by hectic for all of us. Hopefully we can resume soon on this exiting venture as proposed by Rahul
It seems the past month or so by hectic for all of us. Hopefully we can resume soon on this exiting venture as proposed by Rahul
An interesting collection of Class A things
Thought some of you might not have seen this set of pages before, and in particular, some of you may find the schematics interesting in view of our earlier discussions on MOSFET OPS.
Thought some of you might not have seen this set of pages before, and in particular, some of you may find the schematics interesting in view of our earlier discussions on MOSFET OPS.
Want to scale Mount Rushmore in India?
Check the Pass Labs Rushmore active speaker. It's a great inspiration for Class A lovers. It takes care of the low power issue of Class A, and delivers the advantages of active multi-amped speakers. Of course, we don't need to build the 4-way design just like Pass has done... we can always go for some other 2-way or 3-way design. In fact, Pass' choice of using an 80W Class A amp for the extreme low frequencies (the 15" driver) seems to be more a case of "If all you know of is a hammer, all problems appear to be nails", but then I'm ignorant in matters of amps and speakers. I would certainly use a good L-MOSFET-based Class B amp (something the Rod Elliott Project 101?) for that part.
Another interesting thing about the Rushmore is the mechanical design, the location of the heatsink for the undoubtedly large heat dissipation, the audio and power connections, the granite to deaden the front panel. It gives us interesting ideas about how to design our own sexy looking active loudspeakers.
Be sure to read the 4-page PDF file on the Rushmore... it's interesting.
Check the Pass Labs Rushmore active speaker. It's a great inspiration for Class A lovers. It takes care of the low power issue of Class A, and delivers the advantages of active multi-amped speakers. Of course, we don't need to build the 4-way design just like Pass has done... we can always go for some other 2-way or 3-way design. In fact, Pass' choice of using an 80W Class A amp for the extreme low frequencies (the 15" driver) seems to be more a case of "If all you know of is a hammer, all problems appear to be nails", but then I'm ignorant in matters of amps and speakers. I would certainly use a good L-MOSFET-based Class B amp (something the Rod Elliott Project 101?) for that part.
Another interesting thing about the Rushmore is the mechanical design, the location of the heatsink for the undoubtedly large heat dissipation, the audio and power connections, the granite to deaden the front panel. It gives us interesting ideas about how to design our own sexy looking active loudspeakers.
Be sure to read the 4-page PDF file on the Rushmore... it's interesting.
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