Going on from what Viren mentioned, let me also just caution you folks about tube amps.
Merely getting the "iron" a chassis and a Pete Millet PCB is not enough, the amount of hand holding that is needed afterwards is also of an equal order of magnitude for an inexperienced builder-maybe more. This is not for the faint hearted..
Having built both pre and power amps both solid state and tube from kits, trust me on what I say!
1. The voltages one encounters in these are very high-in fact they are lethal-we're not talking about 440V, but much higher ones, which can be lethal.
2. Building an amp from a kit is far more difficult that a solid state kit. Physically handling the much heavier parts are more difficult, there's far more soldering to do given the number of valve pins, errors can creep in far more easily, requiring redo, in the absence of step by step instructions.
3. A good manual with colour photographs, pictorial descriptions, circuit diagrams and step by step instructions make things more manageable. A poorly prepared manual is a real headache. To know if the assembly is okay and to trouble shoot, check voltages are specified in many manuals, we may not have those since this is a plan to scratch build.
To get an idea about how a valve amp manual looks like, check the Magnequest site-they have the SETH 2A3 builders manual on line as a 6.45MB PDF file here:
http://www.magnequest.com/diy_lessard_2a3pp.htm
George
Merely getting the "iron" a chassis and a Pete Millet PCB is not enough, the amount of hand holding that is needed afterwards is also of an equal order of magnitude for an inexperienced builder-maybe more. This is not for the faint hearted..
Having built both pre and power amps both solid state and tube from kits, trust me on what I say!
1. The voltages one encounters in these are very high-in fact they are lethal-we're not talking about 440V, but much higher ones, which can be lethal.
2. Building an amp from a kit is far more difficult that a solid state kit. Physically handling the much heavier parts are more difficult, there's far more soldering to do given the number of valve pins, errors can creep in far more easily, requiring redo, in the absence of step by step instructions.
3. A good manual with colour photographs, pictorial descriptions, circuit diagrams and step by step instructions make things more manageable. A poorly prepared manual is a real headache. To know if the assembly is okay and to trouble shoot, check voltages are specified in many manuals, we may not have those since this is a plan to scratch build.
To get an idea about how a valve amp manual looks like, check the Magnequest site-they have the SETH 2A3 builders manual on line as a 6.45MB PDF file here:
http://www.magnequest.com/diy_lessard_2a3pp.htm
George
Hi Navin,
Looked up Pete Millet's design - it's the push-pull EL34/KT88 etc.
with "universal" driver, right?
The design's fine, and the PCBs make assembly a lot easier, but it does require a crucial input transformer. Even Delta will have difficulty making that - good low loss cores are just not available. For a starter amp, it may be better going with a traditional design - input stage, phase splitter/driver, and output stage. Many such circuits are available off the net.
Also, decide on an output valve, and stay with it. EL34s are the most economical, with many current manufacturers. Designing for multiple output valves doesn't really work out - the operating points are too different. Better to optimise for one.
And point-to-point wiring is not too difficult. Needn't have a PCB to work from. There will be plenty of wiring anyway, to go from power supply, to valves, to transformer. It's challenging, but doable!
Regards,
Viren
Looked up Pete Millet's design - it's the push-pull EL34/KT88 etc.
with "universal" driver, right?
The design's fine, and the PCBs make assembly a lot easier, but it does require a crucial input transformer. Even Delta will have difficulty making that - good low loss cores are just not available. For a starter amp, it may be better going with a traditional design - input stage, phase splitter/driver, and output stage. Many such circuits are available off the net.
Also, decide on an output valve, and stay with it. EL34s are the most economical, with many current manufacturers. Designing for multiple output valves doesn't really work out - the operating points are too different. Better to optimise for one.
And point-to-point wiring is not too difficult. Needn't have a PCB to work from. There will be plenty of wiring anyway, to go from power supply, to valves, to transformer. It's challenging, but doable!
Regards,
Viren
virenb said:
Viren, some time back Wayne (cogsncogs) had designed an EL34 amp that used 1 6SL7 and 2 6SN7s for the input and phase splitter. It used a LTP and I think it is quite a simple design and does not require any input transformer. I'll try and search this... or we could use the HIF 87 or Dynaco ST70 schematics as well.
this is Wayne's circuit
http://www.diyaudio.com/forums/attachment.php?s=&postid=811638&stamp=1136905599
for those who want to reduce cross talk and are willing to add an extra 6SL7 try this
http://ekingsbu.users4.50megs.com/ampEL34.html
or this
http://www.ptsoundlab.com/tubes/amplis/el34/25WPP/blocutc25wppel34.htm
or this
http://www.triodeel.com/acrotrio.gif
Eico HF 87
http://www.triodeel.com/eicohf87.gif
http://www.diyaudio.com/forums/attachment.php?s=&postid=782652&stamp=1133787551
dynaco ST70
http://www.kta-hifi.net/projects/amp_page/st70amp/st70.html
for those who are not hung up on Octals this schematic with a 12AT7 with a 6SN7 is also quite simple
http://home.alphalink.com.au/~cambie/EL34_cct.gif
I have seen many a design including the Ella Consonance and Pete Millets desgin described above that can use KT88s or 6550s in lieu of the the EL34s. Adjusting bias is not really that much trouble.
An intersting site to check out the various components in a Dynaco clone amp is:
http://www.dynakitparts.com/
http://www.dynakitparts.com/
If you are looking at a ST-70 like design for EL34, KT88 etc, there
are a few good designs available -
Shannon Park's design -
http://www.diytube.com
Here's the recent driver board from Matt (earlier with Triode Electronics),
which is open source and uses 6SN7 tubes -
http://www.blackburnaudio.com/
Based on my own expereince, I agree with George that this kind of project
can take up to a year if you are starting from scratch. I finally
have all the parts, but need to make a suitable chassis.
I would like to make it in stainless steel. My current idea is to use
one of those stainless steel serving/chafing trays, which are commonly
used at buffets. Cost under Rs 1000.
http://cdn.overstock.com/images/products/3/L11228049.jpg
Any recos for a good metal work shop in Hyderabad who can cut
the holes for tubes and transformers in the tray?
are a few good designs available -
Shannon Park's design -
http://www.diytube.com
Here's the recent driver board from Matt (earlier with Triode Electronics),
which is open source and uses 6SN7 tubes -
http://www.blackburnaudio.com/
Based on my own expereince, I agree with George that this kind of project
can take up to a year if you are starting from scratch. I finally
have all the parts, but need to make a suitable chassis.
I would like to make it in stainless steel. My current idea is to use
one of those stainless steel serving/chafing trays, which are commonly
used at buffets. Cost under Rs 1000.
http://cdn.overstock.com/images/products/3/L11228049.jpg
Any recos for a good metal work shop in Hyderabad who can cut
the holes for tubes and transformers in the tray?
my goodness, how many watts do you guys need?!
I would have though a nice little SET would be a good place to start....
Decware has a nice kit -- http://www.decware.com/newsite/SE84CDIY.htm
-- can be easily adapted to p2p, low parts count, no need for massive OPTs, simple schematic, easily available tubes...
I would have though a nice little SET would be a good place to start....
Decware has a nice kit -- http://www.decware.com/newsite/SE84CDIY.htm
-- can be easily adapted to p2p, low parts count, no need for massive OPTs, simple schematic, easily available tubes...
quadtech said:
Try to find a "Laser cutting/bending" shop. I tried one of them recently in Bangalore (rishilaser.com) to get some chassis done. Some may not do *one* piece but may do 10...others like Magod Laser in Bangalore (which I have NOT tried) will do one if you meet their minimum order value (about Rs. 2500). They can take the drudgery and clumsiness out of making the basic frame with all its bends and flanges, and you can later tweak it to your liking. All they need is a good Autocad drawing. The precision is what looks really good. And if you make it out of Aluminium, then you can simply wet sand the panels and etch them in Dranex drain cleaner (basically NaOH) to get some incredible results at home!
Tarun and others -good idea to start a separate thread
First of all, it makes sense to agree on broad specs and budget.
Since most people already have speakers, the power needed to drive a broad range of speakers currently owned by people, will determine the design. Then there will be some custom hardware, like power and output trafos, valves, etc. Finally chassis and other components, etc.
A detailed parts list will help clarify many things incl cost. In the US a kit amp using El 34s and producing 30-35 wpc will cost around $750-850 at the lower end. While the chassis may be cheaper here, I don't think most of the other parts will be significantly cheaper.
I could be wrong on this, though!
First of all, it makes sense to agree on broad specs and budget.
Since most people already have speakers, the power needed to drive a broad range of speakers currently owned by people, will determine the design. Then there will be some custom hardware, like power and output trafos, valves, etc. Finally chassis and other components, etc.
A detailed parts list will help clarify many things incl cost. In the US a kit amp using El 34s and producing 30-35 wpc will cost around $750-850 at the lower end. While the chassis may be cheaper here, I don't think most of the other parts will be significantly cheaper.
I could be wrong on this, though!
Bumping a really old thread!
This is some custom work done for me by a friendly fabricator in Mumbai. The cases took over two months from brief to completion, and I've never even met this person, only spoken on the phone
I have no idea about the cost yet because these were built as prototypes. Given the lack of CNC equipment for tiny orders like this the cost is expected to be pretty high (not been informed yet, ambulance is on standby). The finish is brushed anodised aluminum, all panels are 6mm thickness except the top which is 3 or 4mm.
The 2U case will house a PA100 wired point-to-point, with the power supply mounted on the case floor. The 3U will house a fully balanced BPA200 using Audiosector LM4780 amplifier boards with onboard power supply, and 400VA transformer per channel. Chips mount directly to the heatsink and the 4780 boards mount vertically, epoxied or glued to the case floor by their edges. Depth is around 8", the maximum profile width I could find. Little tight but still enough for everyone to be crammed in.
Those interested in similar custom chassis work and do not know who this person is (a bunch of you already know - he also makes speaker stands and hifi racks!), can contact me for his number. He is not cheap, but it is worth it because he is also an audiophile of sorts.
This is some custom work done for me by a friendly fabricator in Mumbai. The cases took over two months from brief to completion, and I've never even met this person, only spoken on the phone
I have no idea about the cost yet because these were built as prototypes. Given the lack of CNC equipment for tiny orders like this the cost is expected to be pretty high (not been informed yet, ambulance is on standby). The finish is brushed anodised aluminum, all panels are 6mm thickness except the top which is 3 or 4mm.
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The 2U case will house a PA100 wired point-to-point, with the power supply mounted on the case floor. The 3U will house a fully balanced BPA200 using Audiosector LM4780 amplifier boards with onboard power supply, and 400VA transformer per channel. Chips mount directly to the heatsink and the 4780 boards mount vertically, epoxied or glued to the case floor by their edges. Depth is around 8", the maximum profile width I could find. Little tight but still enough for everyone to be crammed in.
Those interested in similar custom chassis work and do not know who this person is (a bunch of you already know - he also makes speaker stands and hifi racks!), can contact me for his number. He is not cheap, but it is worth it because he is also an audiophile of sorts.
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Superb case work. 6mm is really thick. THe case will be part of the heat sink too!
The 4780 is a very dense chip and needs a lot of cooling if it is being bridged or in your case parallel-bridged. It might just make more sense to use a set of 3886 instead as that would offer more surface area for the transfer. I al told that 3886TF are now available for about Rs. 400 each.
Ah but the amps are already with me. Both are pretty old now, but the PA100 is housed in a Dinrack chassis (which will be repurposed for more suitable things) and the LM4780 was my main amp for three years in my last Mumbai stint It was kept in a drawer all its active life, and I need to revive it to drive my L18 speakers...
It was kept in a drawer all its active life, and I need to revive it to drive my L18 speakers...
Heatsink is an off-the-shelf profile. Fabricator simply buys and then it is cut to length, drilled and tapped and finished in powder black. He showed me samples for his own work and I decided to use them in this project as they seemed perfect for the chipamp.
The base is not very thick, so you really can't build a discrete amp with these sinks if you wanted.
The base is not very thick, so you really can't build a discrete amp with these sinks if you wanted.
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