[INDIA] Group Amp project

[corbato]

Do you think there are Pass designs which fit this description?

I was just checking out the passdiy site that you gave. Mind boggling stuff ! I'm going to spend the night browsing that site. I can see some SE designs. Look at the 'legacy' section.

I would personally prefer this sort of power rating only for a tweeter in a 2-way or 3-way setup. I think the mid needs more power, specially if like me, you want to have one mid handling everything from about 150Hz to say, 3KHz..

Are you sure of that range? I think going down to 150Hz could prove daunting for a Midrange driver. I would ideally like to Xo at 300Hz.

Strangely, I too have reached a point where I want to build active xo instead of passive.

Both have their own share of pitfalls. Phase alignment is one issue that would worry me a lot. Easy to mess up even a seemingly good active design particularly if you choose haywire xo points.

I guess some will want the minimalist volume-pot-only approach, and others will want a conventional preamp.

Ideally I'd like no vol pot/attenuator at all Since that is not possible the broad thumb rule for me is just a pot if located in the amp body. Else a line stage with moderate gain, particularly as Phono is my main source. For those who are contemplating the simple pot/active line stage here is a quick rundown:

1. Simple Pot:
Things can’t be simpler. Your precious signal doesn’t need to traverse another maze of electronics/resistors/capacitors/solder joints/PCB tracks. This results in lower distortion and better linearity. Flip side is that you are looking at a high output impedance and capacitance. Your pot is away from the Amp and interconnect can play nasty capacitance games. The worst part is that a passive stage is well passive. As in dead. If you need gain to drive an amp then you are stuck. Not if you like a dynamically punchy sound.

2. Active preamp:
Usually an a pot followed by an amplifying device – valve, IC, etc. With or without feedback. It usually overcomes the negatives of the passive design. You get lower output impendence, your interconnects are less of a factor and you really have the wherewithal to drive a power amp to clipping. Flip side is you may loose clarity and may actually end up introducing noise to audio signal.

The third possibility is a gain stage followed by passive stage. Not my idea of a linestage because it incorporate all the failing of both the above topologies. So you need to decide what you want.

Want to do do LR4 based on dual-opamp chips?

Do you have the LR formulae? I want tweak my Tube XO.

My answer for now is very clear... I don't want to try them for my first couple of projects. Let me get a few reliable, inexpensive amps completed first.

Most sensible. Can’t see any reason why you won't be proceeding to Tubes in no time

…DOZ..

Forget it. This one is looser. I built just one channel with fairly standard devices. Sounds pathetic. It’s hard to set up and maintain the bias, which drifts like a drunkard. I was attracted by the simplicity and the fact that it is based on the JLH ’69 design, which I know sounds terrific. I really admire Rod Elliot but this one I didn’t like. Most regrettably.

Rahul:

JLH is my first preference as I’ve heard the ’69 version. FWIW Sonodyne used basic JLH Class AB design for their most successfully amp from the ‘70s. Direct Coupled. They also used the Leach Amp design for their LAB series 120+120 watters (1978) amp. I realised this recently when browsing Sonodyne Technician Manual at the local dealer. Maybe Navin can confirm this with his friend Anindyo of Sonodyne.

I think you have the most experience with MOSFETS in the group so I will take your word on that. If we are getting MOSFETS for that cost then nothing like it. I'm looking at the Pass DIY site (thanks to Tarun). I can see that Pass uses IRF devices. Will you check out availability of these in the local market? Of-course we can always ask On Semi to send any sample by paying the 20$ handling charge.

Ampman

Thanks for the offer. You will have to endure us clowns for what we are. I’m sure all of us are assured that professional advice is at hand. Tarun will particularly like it. He only likes professionals

Sunil:

You need to be fairly careful with phase alignment issues with an active XO. In the worse case situation you may end up shifting 180 deg at say 1kHz ! Yes its is possible. And do you really need to go tri-amp. Unless you are very skilled with theory and possess right equipment, I don’t think this is the right choice. I’d rather do a Bi-Amping project first. Read up Linkwitz-Riley papers if you can. You may find them on the net. Best of luck.

Vivek:

Do you have the Crescendo schematic? I’ve heard so much about it. A Mumbai online company is offering kits for around Rs. 1700 IIRC.

While your anxieties are real, I do not like the idea of adding a non-linear thing like a fuse or relay contacts in the output path. My best bet is to find the real devices and run them under the specified envelop. DC obviously is not a good thing for drivers

 

[Rahul]

Hi! Friends

Thanks Amp Man for joining what do you suggest for a high quality 60-80W amp and for a 200-250W amp.

Tarun I checked data on IRFP250 from different manufacturers. Hexfet is proprietry technolgy of IR for mosfet manufacture hence they refer to it as Hexfet and others as MOsfet . For all practical reason hexfet is Mosfet.

More commonly available one is IR it has a continous rating of 30Amp at 25deg C this falls as temp increases. St microelectronics gives their rating as 33amp.

By reputed vendor I refer to one who is able to give bills for what he sells ie stands behind his stock. I do not think it is just to consider all that is sold in local mkt as fakes after all each town has its share of electronic units. Ron elliot has many examples of fake BJTs ( Not bought from India) As you truly pointed its worldwide. This limitation we will have with any design.
As far as importing is considered I am sure, on MOSFETs the importars will give us better quotes on bulk purchase in comparison to mkt price. I somehow do not feel comfortable with foreign sourcing every time I decide to make a project.

What the heck I am willing to take a chance on 6 MOSFET purchased locally. It may prove fruitful.

By raw power I ment something to drive the sub I feel three or four decimal THD figure would be an overkill here.

I summarise my requirements as a pair of medium power high end amplifier ie 15-25W possibly a class A with lower power output. One high power amp 200-250W good sonic quality but not the ultimate.

Amp man as regular user what is your opinion about these devices, can we rely on our local mkts. Any suggestions on tried tested designs.

Looking forward to all suggestions

Regards

Rahul

 

[Vivek]

Ashok, I do not have the schematics but they are freely available on the net. I also remember people having posted it on this forum. A search should throw up something.

Vivek

 

[Rahul]

Hi ! Ashok

Crescendo is an acclaimed design . My friend Charu at Mumbai does sells kits online but it is mostly the VEGA/ VISHA stuff. I am sure many would have seen his site I can always contact him for details on any of his kits.

http://www.circuitsonweb.com/resources/Audio_Electronics/Power_Amplifiers/

7-8 years back one of my friend made this 240W design. Yes N ch MOSFET and it was well behaved. This was originally published in Elektor and has lot of protection have a look.

http://www.geocities.com/pa_schematics/240Wpoweramp.html

While you are at Pass DIY Ashok also go thru the Citation 12 Mosfet version under legacy I have the boards ready with me.

I feel like going for JLH class A and the N Ch ausie as both are simple designs, lot of documentation and easily available components. If nothing else JLH can even work with 2N3055 from BEL while we await imported BJTs.

Open to suggestions

Regards

Rahul

 

[corbato]

Vivek, Rahul
Thanks for the crescendo info. Not something I will contemplate anytime soon.

Rahul,
I'm steadying my resolve toward the JLH revised. While I looked at all Pass amp project, I'm yet to commit myself to a MOSFET amp.

In a previous post you had mentioned ex-WD heat sinks. Can you give some details on them ?

Thanks

 

[sunil]

Ashok,

Thanx for the concern. Let me present my case & you tell me where I've gone wrong. I know about the phase alignment issues possible with a 3 way active X/O. I started out 2-way but quickly ran aground just getting the costs for a good quality 2way or 3way passive x/o. I had to pad the tweeter by 3db & put in a zobel to keep the impedance constant. I considered winding the inductors myself & even that did'nt exactly work out cheap, for 14gauge. Factoring in the time & effort involved I started thinking active. I already had baffle diffraction in the 2-way actice x/o so that was not an issue.

Then came the issue of the amp I had for the t/m. It is good for the mids but the highs can get harsh at higher levels. Since the average sensitivity of the speaker was about 88db, I thought ( please correct me here if I'm wrong ) with an average loss of about 5-10db in the average furnished living room with the speakers about 10ft away I was not going to get very good, clear, loud sound, around 90db. C'mon once in a while playing RUSH at insensible volumes helps......

The active x/o is consistent with designs available on rane, linkwitzlabs or ESP. It is a 2-way kit from John Pomann which I have changed for a 3-way. It uses good components, atleast what most people say is good. For the baffle diffraction I had some help from Alex Megan. The linkwitz transform is yet to be wired. I know I'm risking it big here but a lot of people have good things to say about 3-way x/o's as well. The x/o is crossed at 3500 & 200. I've tried to keep the baffle diffraction compensation within one driver, the midrange. The baffle width is 7 inches. These crossover points don't fall in the critical range of hearing, or so I hear.......

The tweeter & the midrange are not time-aligned. They are on the same front plane. Even if they were time-aligned would'nt there be phase alignment errors with the cone of the midrange having to move a lot more than the tweeter. Is this a valid argument ? Isn't this a problem by itself ?

Since the power is now available for the individual drivers especially during dynamics, are'nt the drivers going to be operating at their optimum levels. They are not going to contend with each other for power on loud passages or during dynamics. The music I listen to is mostly like that. Tribal Tech, Rush, Zappa, Coryell

The drivers are D27, P13wh & P21wo-39-08

This is why I am keen to get a low power amp for the tweeter, something that is sweet & won't be harsh at the volumes my hearing-impaired brain likes to listen to.

Any corrections, thoughts, comments are more than welcome.
I have access to stuff from down-under & we can do a group-buy, if you like.

Cheers,
sunil

 

[corbato]

Hi Sunil

I had to pad the tweeter by 3db & put in a zobel to keep the impedance constant.

Thats fine I'd think.

I considered winding the inductors myself & even that did'nt exactly work out cheap, for 14gauge.

Not to mention sore fingers

Factoring in the time & effort involved I started thinking active.

Quite sensible.

..with an average loss of about 5-10db in the average furnished living room with the speakers about 10ft away I was not going to get very good, clear, loud sound, around 90db.

On the contrary, with separate amps you may get uncomfortable that the 1kHz to 2kHz range. Our ears are most sensitive at this range to any perceived peak in dB and/or phasing.

The x/o is crossed at 3500 & 200...These crossover points don't fall in the critical range of hearing, or so I hear.......

Yes you are right. Messing around with the so called golden band is not advisable. But my only worry with this thinking is how to find squawkers that handle things less than 700Hz nicely. Back in my younger days I had a wonderful book called "Build and Test your own Speaker System" or something like that. It proffered a thumb rule of xoing at 800Hz for an 8" woofer and 500Hz for 12". I built many speakers with that in mind. They sounded quite nice at least those days, when we mostly listened to loud Led Zep or Deep Purple things.

Even if they were time-aligned would'nt there be phase alignment errors with the cone of the midrange having to move a lot more than the tweeter. Is this a valid argument ? Isn't this a problem by itself ?

Yes and No. The time alignment theory by voice coil placement at best is erratic. Not a problem by itself when you consider what bigger mistakes one can make by aiming for that socalled symmetrical placement idea relative to the other enclosure.

They are not going to contend with each other for power on loud passages or during dynamics.

Actually a bigger problem occurs within your amp, where the entire spectrum of music is fighting for a fixed power handling capacity and looking to out put the same level.

This is why I am keen to get a low power amp for the tweeter, something that is sweet & won't be harsh at the volumes my hearing-impaired brain likes to listen to

Since you like to listen to music at a robust level consider the following power bands amps for tri-amping:

High: 15 to 20 watts approx
Mid: 40 to 55 watts
Low: 100 to 120 watts.

I'm sure your active XO has gain setting for individual freq band. You mentioned that you have changed that 2 way XO to a 3 way. Did you cascade one stage or did you add an additional stage to the existing design. Quite easy actually either way.

I'm sure your tri-amp project will be come out with flying colours. Keep posting the details so that we can all learn.

 

[Rahul]

Ashok

Agra has COD (Central Ordinance depot) any thing that is withdrawn all over the country is sent here. The local mkt Chipitola is the main surplus mkt with lot of disposal dealers. Range of stuff available is amazing be it auto spares, clothings , communication equipment, electronic stuff, binoculars test instruments etc etc... all used. Even parachutes, laser sights just amazing.

Heatsink is integral part of any equipment and here it is not the local stuff we are accustomed too but quality stuff mostly all imported and mil spec. Something on the lines of what we see in foriegn projects and high end commercial equipment. There is lot of variety, plain ones for diode mounting and also huge ones 5-10 kg each range or more, usually back panel of high apearage charger and other power supples. Then again heatsink from transmitter is also there now you can imagine a 1KW transmitter heatsink, amp there is usually Class AB and only 50% efficient. Then again HS from telephone exchanges, troposcatter units and number of things that even I could not make out head or tail. Generally these heatsink may have the transistors mounted on them genuine Motorola devices mil grade, as to junk dealers used components are not worth keeping. 3055 and 3773 as well as diodes are generally removed as it can be sold but anything else stays. There is lot of Russian stuff all hevy solid metal job just at scrap value.

Ashok of your interest there are lot of tubes miniatuire 9 pins, octal, ceramic tetrode just name it.and transformers from simple ones to 2KV or more from even in KVA ranges again this is all Mil spec like Hypersil transformers. Sorry not PP audiophile garde but old PA system yes.

All sort of test instrument is also available eg AVO 7 or 8 multimeter goes for Rs300/, scope in range of 1.5-3K, moving coil meter is also availble by tonnes good stuff SIEMENS etc goes for Rs20/ each. I recently purchased a Tektronix 2465B scope 4 channel 400MHz BW, for 2k. (Of course I had to repair it). You also get get function generators. Electronic equipment price is approximated at Rs50-100 per kg depending upon its condition, weight and appearance. New plastic panel stuff goes cheap> Main reason I got Tek scope for 2K, an old heavy Aplab 50Mhz was priced at 3K.

Of interest to DIY community, cooling fans are there , cetrifugal blowers, brushless, muffin from 3inches to more than 12inches dia.

Heatsink goes slightly higher than scrap rate last i bought they were Rs100-130/ per kg depending upon the condition and holes less holes more expensive but max around Rs130/. Amazing part since all the dealers are lincesed all stuff is sold on BILL. Pricing much depends upon your bargainig skills. My experience in dealing with dealers has been very good as most of them are Jains and quite honest once committed they stick to their words and do not take you for a ride. Much of the availibity also depends upon what has been auctioned lately but heatsinks are year round stuff.

For any thing even close to an Class A amp I highly recommend these used heatsink as they are much more efficient and offer bettar cooling than the usual stuff available in mkt. Cost apart.

A word of caution there is no guarantee that thing would work if you invest in complete electronic stuff after all it has been scrapped for a valid reason but generally I have managed to get them going.

I have given reference of other stuff so that DIYers of India can benefit at large. Hope this will be of help.

Regards

Rahul

 

[Rahul]

WARNING:

I have visiting this mkt for last 15 years. After sometime you will find your room starting to resemble the junk mkt.

 

[sunil]

Rahul,

The heatsink stuff sounds really good. Good stuff is expensive & with class A its going to be big. Can we all agree on what we are going to put together, Class A, class AB, 25w, 50w, 100w. This project sounds really good & we should make it happen. I'll leave it to the experts to decide which design is best.

Ashok,

Thanx for that. So with a 3-way active x/o I'm going to have phase errors in the 1khz & 2khz anyways. Is that it ?

The power band you've spec'd for tri-amping hit the nail on the spot. For the tweeter, that is exactly what I'm looking at, 25-50w. The rest is what I've already got. The x/o has gain adjustment for the tweeter only. Although padded by 3db, if I need more I want the flexibility. The 2-way was cascaded to a 3-way. The outputs are taken from the 1st & 3rd stages. I based the design on the stuff put up by Rod Elliot.

Cheers,
sunil

 

[tcpip]

Agra has COD (Central Ordinance depot) any thing that is withdrawn all over the country is sent here. The local mkt Chipitola is the main surplus mkt with lot of disposal dealers. Range of stuff available is amazing be it auto spares, clothings , communication equipment, electronic stuff, binoculars test instruments etc etc... all used. Even parachutes, laser sights just amazing.

Man! This was one post of the kind which makes all the time I spend on this site worthwhile. Don't know how to say "Great stuff!!" loudly enough so that you can hear. It's not just how useful this info is for me (don't know when I'll ever go to Agra... I've never been there yet and half my life is over), but how interesting and evocative your description was.

Imagine! Building arrays of amps with big heatsinks and transformers (the two costliest items) all retrieved from disposal sales. At most the heatsinks may need to be re-anodised, for appearance sake. Slurpp! And finally, one day, I may even be able to afford a 'scope. The first thing I'll do with it is to put one probe in each ear of my wife, and actually see what goes on between those ears. Any other married member here felt this way?

 

[tcpip]

The anatomy of a fake power transistor

Tarun I checked data on IRFP250 from different manufacturers. Hexfet is proprietry technolgy of IR for mosfet manufacture hence they refer to it as Hexfet and others as MOsfet . For all practical reason hexfet is Mosfet.

Got it. Thanks.

By reputed vendor I refer to one who is able to give bills for what he sells ie stands behind his stock. I do not think it is just to consider all that is sold in local mkt as fakes after all each town has its share of electronic units.

Rahul, I don't think I really should spend any more time arguing this point, because I think I fully understand your perspective, and any more arguments can lead to misunderstanding.

Just wanted to make one last attempt to clarify my point. The key point to understand here is that even the most reputed dealer, paying his Sales Tax and selling with a pucca bill, can be selling fakes. This was my reason to cite the case of Digikey Canada. The reseller does not know that these are fakes. He is just the last man in a chain of international distribution, and his immediate upstream chap may not know about the fakes either. It has been found that merchandising personnel, doing bulk deals for international distribution markets, often strike "very competitive one-off" deals from parties they do business with, and such one-off deals can sometimes be fakes, re-routed (laundered?) through "regular" channels to look respectable.

Let me explain a bit about how fakes work. We in India think that fakes are cheap knock-offs made by one sleazy guy with a monocle, sitting in a 5'x5' tenement in one corner of a slum, and shipped off at night in covered pick-up trucks. In the semiconductor world, fakes don't get made this way. Fakes are made by very large factories who have spare capacity, who identify that there are high-priced transistors (usually power transistors, both MOSFET and BJT) which can be "re-made" at a lower price and sold for high margins. The real margins in legal production of authentic stuff is wafer-thin, hence this constant search for "opportunities."

So, these guys will pick up, let's say, the very-highly-faked 2SC3281, which sells for a dollar in the wholesale market. They'll pick up the semiconductor core of the 2N3055 and package it in a TO247 case, with proper electrical connections, and label it "C3281". They'll sometimes omit the manufacturer name, or represent the label in some other format, so that they can even escape legal action at the crunch. This product, if sold as a 2N3055, would have cost perhaps ten cents in the wholesale market.

Now, what the end-user gets is actually a fully-functioning 2N3055 in a 2SC3281 package. The difference between the 2SC3281 and the 2N3055? Very big for some of us, but not at all that big for many of us. How many of us push a 2SC3281 to its limits of Vceo or the limits of its operating current? What we'll find is that the fake transistor will blow when you play your amp at high volumes but will behave quite okay at lower volumes. There are hundreds of circuits where a 2N3055 put in place of a 2SC3281 will not cause any problems most of the time. In audio power amps in particular, specially in OPS of Class B amps, you'll find that the OPS devices are stressed very little when you listen at "normal listening levels", but are stressed very heavily at full volume. For such apps, the fake devices will fail at full volumes, and the end user will simply conclude that he'd "pushed his amp too hard." The truth may be that he'd not even scratched the limits of a real 3281. And how many of us can tell the difference in linearity between a 2N3055 and a 2SC3281 unless we do careful A-to-B comparisons? Angshu made his first Doug Self Blameless amp with 2N3055s, and he said they sounded excellent. And let's face it: a 2N3055 can push out perhaps 6A of current. How often do have 6A of current flowing through our speakers? Our home use systems don't need the high rating of the top-class power devices. Yes, we'd love the linearity and extra reliability, but we are incapable of noticing the difference if we are given a fake.

So our end-user goes to the market, gets a replacement device (another fake), and again starts using the amp, believing it to be as good as new. Once again, if he plays the amp hard, it blows. And the cycle continues. If on the other hand he had these devices in a Class A amp, it would probably blow every evening.

I believe that many Indian (and non-Indian) end-users, right now, may be using fake devices in audio power amps without realising it. This is particularly true of those who buy Indian-made PA amps for "sound systems" for hotels and renting out for festivals and parties. Such systems are always manufactured under tremendous cost pressures.

Now I hope I've been able to explain that the reputation of the dealer and the presence or absence of a pucca bill has no connection with whether the transistor is a fake or not. The only way you can depend on a dealer is if that dealer procures his parts straight from the manufacturer, i.e. NatSemi or Toshiba. Digikey, Allied, RS, and a lot of the other big players do. I am sure not a single Indian retailer (not distri, but retailer) does. They don't have the volumes.

What the heck I am willing to take a chance on 6 MOSFET purchased locally. It may prove fruitful.

Fully agree. After all, you're talking of a risk of Rs.250. My problem, which does not apply to you, is that I am very poor at troubleshooting and repair. Hence, I want to take steps that problems don't arise at all, rather than take a risk and then have a part blow up in my face.

By raw power I ment something to drive the sub I feel three or four decimal THD figure would be an overkill here.

I now understand. You want a subwoofer amp. Yes, for such amps, you can use much more simple designs. Cool!

 

[tcpip]

It proffered a thumb rule of xoing at 800Hz for an 8" woofer and 500Hz for 12". I built many speakers with that in mind.

A good rule from a more modern source (Vance Dickason's Loudspeaker Design Cook book) says that if you build a 3-way, you should either have one decade or at least three octaves as the minimum gap between the lower and upper xo frequencies. This means that one-decade gap translates to 300Hz-3KHz, or 200Hz-2KHz, and so on. Three-octaves is a little less.

High: 15 to 20 watts approx
Mid: 40 to 55 watts
Low: 100 to 120 watts.

I find this diagram useful to understand music power distribution across frequencies.

 

[tcpip]

Are you sure of that range? I think going down to 150Hz could prove daunting for a Midrange driver. I would ideally like to Xo at 300Hz.

Aha! The trick I intend to use is to not use a traditional midrange driver at all, but use a so-called full-range driver. Something like a Fostex or a Jordan JX92S. That can handle a decade-wide range quite well.

Ampman

.... Tarun will particularly like it. He only likes professionals

I'll get you for this one day. Watch out!

Tarun

 

[Rahul]

Thanks! Friends

I sincerly hope we are able to come up with something useful.

Tarun

I realise often vendors are unaware of the electrical charecteristics of stuff they are selling. Sadly we have to live with fake components for now. For a one off unit purchasing direct or from suppliers in foriegn countries can be done but it becomes difficult when we have to compete in our local mkt. For our Amp use we can go in for foreign sourcing.

I just remembered about PCB layout I suggest you tryout "Sprint Layout" ver4 a German software, demo version is available for download, you will be able to master it in an hour I am sure, it is very simple and very good. Then download its Russian version4 from:

http://ra3ggi.qrz.ru/file.shtml

This has all features enabled saving , printing , two point autorouting, block area fill, groundplane and even appearance of complete finished PCB.

On subject of amps my opinion, a single sided PCB for the OPTI-MOS design is not an easy job it will require lot of trial with the placement.
As far as complexity is concerned class A JLH is very simple to assemble, it is only heatsinking and power supply we have to pay more attention to. Given our limitations JLH appers to be attractive. If we make any other design it still would keep nagging me that I have try out a class A solidstate amp.
Options still open for high power amp.

Sunil and thers I have made the PCBs for Pass modification of Citation12 and presently assembling them. Just check out about this design for our use. 45W /ch into 8ohms is my conservative guess it will push out. I will put up a pic of assebled unit and PCB in few days, you all will be able to see one of the heatsink purchased from disposal stuff.

While working along the lines I also peeked into one of the chinese amp 5ch from 'Horror'. In case there was a possibilty of modifications and much to my horror I found it was only 2 ch unit inside.final transistors are C4466 and A1693 one each per channel, volume control PCB has a BA5053 chip and tone control is based on 4558 dual OP amp.Power transformer is torroidal and supply caps are 10,000uF/50V 2nos. It appears 5 inputs are summed up and output for sorrounds derived from main L&R thru resistors in series. All in all a waste of money i feel. Price 4K.

Recently I was at IIT Kanpur conducting workshop have a look at the pictures:

http://www.indiahams.com/techkriti.htm

My radio call ia VU3WJM.

Regards

Rahul

 

[tcpip]

I just remembered about PCB layout I suggest you tryout "Sprint Layout" ver4 a German software, demo version is available for download

Does it run on Linux? If not, there are plenty of other Windows-based packages too, but I use Linux.

On subject of amps my opinion, a single sided PCB for the OPTI-MOS design is not an easy job it will require lot of trial with the placement.

There's the PCB design with component placement diagram that he's given in his book. One can always try to replicate that.... it's single-sided. About 6"x9". I'm not suggesting that OptiMOS is the only way to go, but in case you want to, we have lots and lots of info from the designer's book.

This is getting interesting... good you started us all on this Indian group build thing. Now if only the professionals would leave us alone....

 

[corbato]

Rahul:
Awesome info on the COD. I'm sure you may even be able to pick up Manpacks for your use too. Keep an for AF modulating tubes such as 845.

Do you think it is feasible to collect Heat Sinks from COD for JLH group build? i think I'll give those used Transformers as pass for a Class A project.

Ok. So how many of us are in this group build. I'm going to Germany this month end and I can collect WIMA MKP capacitors for the JLH or any other project. Just let me know your requirements. I can despatch the same to whoever needs 'em by 1st week of April. But then any one interested will need to tell me know as I will ask my contact in Germany have them ready.

I'll again emphasis that Semi should either be requested as "phiokat ka maal" or bought from RS. Resistors to should be sourced from RS. They sell Caddock too. And I offer to build and ship the chassis for those keen.

Lets freeze on the JLH. Its simple. It sounds good.

 

[corbato]

Posted by tcpip

..Something like a Fostex or a Jordan JX92S

Yes I'd thought of a FR. But do you get these in Mumbai?

I'll get you for this one day. Watch out!

You threating to let loose a certain Ape on me?? I'm wetting my pants already

 

[corbato]

Recently I was at IIT Kanpur conducting workshop have a look at the pictures:

What? so many OM's and not a single YL ???

My 73's 2 u.

 

[tcpip]

Jx92s

Yes I'd thought of a FR. But do you get these in Mumbai?

Strictly speaking, I got my pair of JX92S in Bombay. I asked a friend to order them from E J Jordan UK, and he paid full courier charges. The Customs guys decided that only two drivers means it's a sample, and charged no duty. My friend (a hardware reseller and audio keeno) thus procured the pair through absolutely proper channels, and gave me a bill with sales tax added. And I got them in a week's time, delivered to my doorstep. Any hardware reseller who occasionally imports items will be able to do this for you, provided you are willing to pay shipping costs. The drivers cost me UKP 150 or so for the pair, and another UKP 50 or so for courier charges.

Jordan is one of the few speaker driver makers who sell retail quantities directly to customers anywhere in the world.