Hi PMA,
Do you have any good reason to use only two rectifier diodes and not a diode bridge with a center tap transformer : lower hum frequency, higher conduction angle of the diodes ?
Do you have any good reason to use only two rectifier diodes and not a diode bridge with a center tap transformer : lower hum frequency, higher conduction angle of the diodes ?
Please forget rectifier, it was not the case. I pointed to capacitance multiplier.
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It is a schematic of the produced circuit, dual voltage from single-winding transformer was a condition.
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It is a schematic of the produced circuit, dual voltage from single-winding transformer was a condition.
Topology is OK, but fets are better because they allow the output caps to be reduced to .1uf or so. This sounds better with sensitive circuits, believe it or not.
Case material
Mr. Curl.
I am interested in going back to an earlier point of discussion.
The case material.
Particularly the machining of the case from Aluminimum.
In severeal posts it was mentiond that this gave a (relatively) gas tight design.
It was also mentioned that it provided rigidity
It was also mentioned that it provided a good faraday cage.
Sugestions of using it as a heat sink were allso made.
Also the seamless look is just COOL
Though I have no direct experience of such exotic enclosures I am interested in any comments that you would share on three points.
1) the rigidity - Obviously this will help with microphony and solder joint stress. Yet in the internal photos there is no sign of other damping or mechanical decoupling. Was the case good enough on it's own?
2) EMI suseptability. From an EMI standpoint aluminimum is not optimum. May be this is not a design issue for your designs, but with such a high bandwidth I would worry about EMI.
3) What other case materials were considered? Copper? Composites?
Many thanks
Brian
Mr. Curl.
I am interested in going back to an earlier point of discussion.
The case material.
Particularly the machining of the case from Aluminimum.
In severeal posts it was mentiond that this gave a (relatively) gas tight design.
It was also mentioned that it provided rigidity
It was also mentioned that it provided a good faraday cage.
Sugestions of using it as a heat sink were allso made.
Also the seamless look is just COOL
Though I have no direct experience of such exotic enclosures I am interested in any comments that you would share on three points.
1) the rigidity - Obviously this will help with microphony and solder joint stress. Yet in the internal photos there is no sign of other damping or mechanical decoupling. Was the case good enough on it's own?
2) EMI suseptability. From an EMI standpoint aluminimum is not optimum. May be this is not a design issue for your designs, but with such a high bandwidth I would worry about EMI.
3) What other case materials were considered? Copper? Composites?
Many thanks
Brian
Brian,
if you had read this thread you would have found answers to Al and EMI.
Many of you guys want repeating in circles instead of training your brains.
if you had read this thread you would have found answers to Al and EMI.
Many of you guys want repeating in circles instead of training your brains.
Electrostatic fields can be stopped dead in their tracks with a piece of foil.
Electromagnetic fields can be re-routed to avoid sensitive circuitry using high permeabiliy materials to capture and steer the flux. OR, the mag-fields can be dissipated (converted into heat) by using a sufficient thickness of conductive materials.
😉
Electromagnetic fields can be re-routed to avoid sensitive circuitry using high permeabiliy materials to capture and steer the flux. OR, the mag-fields can be dissipated (converted into heat) by using a sufficient thickness of conductive materials.
😉
Silver would be best. Now, the preamps sell retail for about 5 million yen each. The cases cost me about $3000 for a set, and rising. Should I increase the price to 10 million yen?
I'm not making any more Blowtorch preamps so why don't you make the trillion yen preamp Mike? Maybe Nelson can help you. 😀
silver
I apologise if
1) I missed the element of discussion
2) I did not ask the question in enough detail to truly indicate my question.
I agree with the issues of cost and silver, however in my work I have found that Aluminium ( in this case {BOOM Tishhh} is was cast ) particularly bad for the long term absotption of EM fields. This was probably due to corrosion of the attachment points using dis-similar materials.
We returned to steel.
This is in volume consumer products that I design ( 12 Million Satelite TV recievers shipped so far) .
I my field the quality of manufacture and end user installation environment are significant factors in the longevity of the product in this respect.
These are variables for which you are not so 'strong' in your environment.
On the microphony front.
We clearly measure the effects from the vibration of things like the hard disk head servo, fan motor etc. in video audio and tuners. And yes it is microphony, because you can rap the components and see the impulse response.
The effect is strongly influenced by the component choices, but I am becomming increasing convinced that with DSM silicon it is an increasing effect.
On my home amplifiers I can measure impulses as high as the -60dBV level prior to case installation.
However I don't have a calibrated impact source at home so I cant tell what the energy profile of the impact is.
At these kinds of levels I have put a fair amount of effort into mechanical mittigation on my home designs.
So my question (microphony) was is this a consideration in the design process ?
Brian
I apologise if
1) I missed the element of discussion
2) I did not ask the question in enough detail to truly indicate my question.
I agree with the issues of cost and silver, however in my work I have found that Aluminium ( in this case {BOOM Tishhh} is was cast ) particularly bad for the long term absotption of EM fields. This was probably due to corrosion of the attachment points using dis-similar materials.
We returned to steel.
This is in volume consumer products that I design ( 12 Million Satelite TV recievers shipped so far) .
I my field the quality of manufacture and end user installation environment are significant factors in the longevity of the product in this respect.
These are variables for which you are not so 'strong' in your environment.
On the microphony front.
We clearly measure the effects from the vibration of things like the hard disk head servo, fan motor etc. in video audio and tuners. And yes it is microphony, because you can rap the components and see the impulse response.
The effect is strongly influenced by the component choices, but I am becomming increasing convinced that with DSM silicon it is an increasing effect.
On my home amplifiers I can measure impulses as high as the -60dBV level prior to case installation.
However I don't have a calibrated impact source at home so I cant tell what the energy profile of the impact is.
At these kinds of levels I have put a fair amount of effort into mechanical mittigation on my home designs.
So my question (microphony) was is this a consideration in the design process ?
Brian
We tend to avoid steel, because it can add non-linearity to the equation. I don't like thin aluminum, because it can vibrate easily. We were making a 'statement' product, so we went 'all out' Today, I hope to find a less costly solution.
... and thin aluminium would not shield against lower frequency magnetic field component, due to skin depth.
Costly..
At work
We had significant sucess with Metal Matrix Composite, but that was several years ago in a different industry. I think that the cost would make Silver look really cheap!
From a vibration point of view Quiet Steel is nice, Especially if you get it with a copper flash. ( Helps the EMI )
However it is a pain to weld/form.
Personnaly I have had a lot of sucess with my home designs with Copper sheet bonded to a carbon fiber honeycomb sheet.
I glued it alltogether by vacume bagged it into a mold.
I now have the closet thing to a stealth preamp!
IMO the dis-similar materials help damp the system. The copper and carbon helps soak the EMI
Brian
At work
We had significant sucess with Metal Matrix Composite, but that was several years ago in a different industry. I think that the cost would make Silver look really cheap!
From a vibration point of view Quiet Steel is nice, Especially if you get it with a copper flash. ( Helps the EMI )
However it is a pain to weld/form.
Personnaly I have had a lot of sucess with my home designs with Copper sheet bonded to a carbon fiber honeycomb sheet.
I glued it alltogether by vacume bagged it into a mold.
I now have the closet thing to a stealth preamp!
IMO the dis-similar materials help damp the system. The copper and carbon helps soak the EMI
Brian
Again - you need thick copper to shield against low frequency magnetic component of the field. Coated plastic would not help against it.
Copper sheet
the copper sheet is 3mm ~1/8th inch
Oh and yes that was a typo, but quite a good one 🙂
Though the carbon fibre is rather good at absorbing stray fields.
the copper sheet is 3mm ~1/8th inch
Oh and yes that was a typo, but quite a good one 🙂
Though the carbon fibre is rather good at absorbing stray fields.
Schematic or circuit forthcoming?
Whew! I read through this rather long and entertaining thread in the hope that I might find some interesting schematics or a design for a line level or phono gain stage. Hopefully a schematic that might have something to do with the CTC Blowtorch preamp; Did I miss it? If so, point it out to me
In looking at the CTC (http://www.tgaudio.com/pictures/Blowtorch_Silver_Interior.JPG) I am struck by the use of hookup wire. Tiny circuit boards (reminiscent of Eagle derived PCB in terms of size) with long wire connections. I find this interesting because it seems to go against the idea/trend of large PCB with ground planes (harks back to old tube pt-to-pt based designs). So, the shortest copper path between active components/stages is not necessarily the most musical path? I like the Teflon RCA boards – I have used this idea in a couple of passive crossovers.
John – does this mean that you will not be showing the CTC with Roger West at W-CES again this year? What a pity.
Whew! I read through this rather long and entertaining thread in the hope that I might find some interesting schematics or a design for a line level or phono gain stage. Hopefully a schematic that might have something to do with the CTC Blowtorch preamp; Did I miss it? If so, point it out to me
In looking at the CTC (http://www.tgaudio.com/pictures/Blowtorch_Silver_Interior.JPG) I am struck by the use of hookup wire. Tiny circuit boards (reminiscent of Eagle derived PCB in terms of size) with long wire connections. I find this interesting because it seems to go against the idea/trend of large PCB with ground planes (harks back to old tube pt-to-pt based designs). So, the shortest copper path between active components/stages is not necessarily the most musical path? I like the Teflon RCA boards – I have used this idea in a couple of passive crossovers.
John – does this mean that you will not be showing the CTC with Roger West at W-CES again this year? What a pity.
The circuit boards have double ground planes, but we prefer point to point wiring in this preamp BECAUSE the switches and the pots that we are using REQUIRE the use of point to point wiring. It may seem that we could have made the case somewhat smaller, but THEN we could not have had enough room for EVERYTHING that we had hoped to put into the box when it was first designed, such as a buffer card for long cable runs and fully balanced inputs and outputs. Most people opted for the simpler version, so we had some space left. Since we used the best wire that we could find, and broke we it in, on the spool, and noted the directionality of the wire on application, we were able to use a quality silver wire and get away with it (thanks again Bear).
In the case of schematics, I decided not to publish any, BUT a good preamp could be made from the published schematics of others who attempted to emulate the preamp on this thread.
Our latest CTC designed preamp, that is much cheaper and easier to make, has little or no wiring, BUT it has double ground planes on a big circuit board. It should be available sooner or later.
In the case of schematics, I decided not to publish any, BUT a good preamp could be made from the published schematics of others who attempted to emulate the preamp on this thread.
Our latest CTC designed preamp, that is much cheaper and easier to make, has little or no wiring, BUT it has double ground planes on a big circuit board. It should be available sooner or later.
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