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Old 30th July 2008, 05:30 AM   #1
tcpip is offline tcpip  India
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Default A group-build project for a tube power amp in India

There have been lots of discussions in this thread about exploring options to build a tube power amp for tube beginners in India, given our serious constraints about sourcing parts. We've actually located one veteran transformer manufacturing company which has designed and built their own range of audio OPS transformers for tube amps. There's at least one brand of high-end Indian tube amps which uses these transformers with excellent results. This encourages us to try a full amp.

There are of course a large number of other exotic components to source, and there's the tube-inexperience of most of us to also take into account.

Starting a new thread to take all this discussion forward. Looking for inputs/ideas from all over the world, of course, though some of the parts decisions may be taken based on sourcing constraints for us in our Glorious Motherland.
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Old 30th July 2008, 05:50 AM   #2
chrish is online now chrish  Australia
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Do you have problems with importing things from the postal service? I have heard there is a lot of corruption and theft of postal items in some countries. If it is OK, you may wish to source some of the capacitors and valves from the former Soviet states. I have not had a problem with shipping or bad goods from any of the ebay sellers of this stuff. Of particular interest might be the small signal valves such as 6N1P, 6N2P, 6N23P and output valves such as 6P3S (6L6) 6P14P (EL84) and 6P15P (EL83).

Good luck with the projects. If there are any good sources for gear in Mumbai, let us know, I get there once or twice a year.

Chris
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Old 30th July 2008, 06:10 AM   #3
Vivek is offline Vivek  India
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In India, the postal service is not bad at all. It is the customs duty etc which sometimes makes it too expensive to import. That has been the problem for Indian DIYers otherwise there is no problem for Indians to order from sites like ebay. The Indian ebay does not stock DIY audio stuff.

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Old 30th July 2008, 07:12 AM   #4
sagar is offline sagar  India
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Great!! More than the economics of a group buy, im personally more interested in picking the brains of the more experienced builders in India and learning a lot more about audio electronics through this project. Another advantage would be that as a group buy, most of the purchases can be staggered over the period of the build : one year by some estimates, keeping things nice and happy at home Hope to see the more experienced posters from India piping in on this thread soon.
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Old 30th July 2008, 07:16 AM   #5
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Hi,

Am member of this forum from very very long time but a passive one !!

Its nice to see that finally indian group buy taking place !

Tarun Rikhav has said soo much about you !

Vivek how are you buddy ?? long time no see !!

Will be watching very closely the developments of this thread !

Regards.
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Old 30th July 2008, 07:17 AM   #6
sagar is offline sagar  India
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Quote:
Originally posted by Vivek
In India, the postal service is not bad at all. It is the customs duty etc which sometimes makes it too expensive to import.
Isn't it duty-free to import upto 25,000 rupees of items at one-time, especially electronics? I think that even if the group buy orders exceed this amount, the fact that it is an import of components rather than fully-built up systems should qualify for lower duties. Will need to get more info more the DGFT website.
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Old 30th July 2008, 10:13 AM   #7
gjo is offline gjo  India
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Tarun:

I am willing and able to share my experience to assist this project going forward..

AFAIK, the 25K exemption limit is for baggage when one comes in from abroad, and not for stuff that is sent through the postal dept.

Going out from my earlier post, one needs to define output. My guess is that the range of 30+ wpc is fine, and one can easily consider a Dynaco clone, without getting into scratch building. The transformer specs are available, and all it needs is reverse engineering of the transformers, without getting into any IP issues.

I have a pdf copy of the Dynaco assembly manual that can be sent to anyone interested. One needs to look at what the cost of the mains tranny and output tranny will be, to get some idea about costing. The chassis, valves, choke and hardware are other cost items, and most Dynaco clones have a driver board that is offered by various vendors.

At the upper price band look here:

http://www.avahifi.com/root/equipmen...ultimate70.htm

There is another from Curcio Audio( Dynaco-doctor), and Triode Electronics also offers these, as does Welborne Labs.

Once you guys do some research and understand what are the various components, it gets a bit easier.

I am currently in the process of redoing a similar amp(Welborne Labs ST-70), and have done some research, so I can share some info with you. My amp was a kit from the US, using Magnequest output transformers, but I got it assembled many years ago by a friend who had very little experience in valve amps-though he was a PhD in physics and knew all about ss amps. The net result was that he made a hash of it.

I am now trying to salvage it, using an avahifi board that I have ordered, and hope it will come out right. In the meantime I have two other valve amps to play around with, so this is a low priority project for me at this time.

(As an aside: I have an unused, surplus board, with detailed assembly manual, with components, except tubes, mounting plate, chassis, hardware and trannies that I bought some years ago from Welborne Labs for a similar amp-for details see:

http://www.welbornelabs.com/st70.htm

The item I have is the ST 70A-if anyone wants it, after he has done all of the research, please let me know. I can offer it at cost. However, one needs to factor in all the rest of the stuff, to arrive at a more accurate costing of this amp as a project. Merely buying this will not be enough..)
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Old 30th July 2008, 10:18 AM   #8
gjo is offline gjo  India
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Amp power -interesting read from Welborne, somewhere in the middle of the page.

http://www.welbornelabs.com/recomendspeaks.htm
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Old 30th July 2008, 11:09 AM   #9
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Hi all,
i would be interested in this project, i have a classic case of tube-inexperience so am hesitant to start a project on my own. i know no one has done a costing for the project but do you have any ballpark figures?

look forward to reading more about this,
mymindinside
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Old 30th July 2008, 11:48 AM   #10
sagar is offline sagar  India
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Quote:
Originally posted by gjo

AFAIK, the 25K exemption limit is for baggage when one comes in from abroad, and not for stuff that is sent through the postal dept.
Right you are. From what I can gather online, valves/tubes for amplifiers are charged at 12.5% specific duty per piece. Other components such as potentiometers, resistors, capacitors are duty-free. I think once there is some interest in the build and a consensus on the BOM, then looking into what needs to be imported and whats locally available would make sense.
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