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GSP Preamp

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Post Options Post Options   Thanks (0) Thanks(0)   Quote morris_minor Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jun 2014 at 12:18pm
A blade approach to adding functionality with discrete electronics appeals to me, but I'm an ol' fogey. With more and more microprocessor controlled units around, converting everything to the digital domain, the discrete analogue route is becoming more and more retro, and falling behind the mainstream IMO. I don't see GSP being able to compete with the big Corporations and their economy of scale for development, tooling, marketing etc. Sound quality is the first casualty despite plenty of folk bigging it up for back-handers. The unfortunate fact is that producing excellent kit doesn't make people buy it if it doesn't fit in with their preferences which have been skilfully manipulated by the audio press to favour their advertisers.
Bob

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Accession MC/Enigma, Accession MM, Reflex M, Elevator EXP, Era Gold V
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bi-wire Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jun 2014 at 1:21pm
I am interested to follow the development of this.
Hmm, not sure about the smokey black front panel; prefer the look of the Majestic.
I am in a minority (of 1 possibly) but I don't think tone controls are required. I know I have already lost this argument but would ask that they be 'by-passable'(is that a word?).
Peter

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jun 2014 at 2:33pm
Hi Peter, I'm not thinking of putting tone controls on the preamp.

I made a suggestion of a 'card frame' for people wanting to 'design their own system'. It would be very expensive for me to develop a series of 'standard' cards, but it would not be the first time - broadcast studios were often done this way. However, I don't think the average hi-fi customer would have a clue what I'm talking about, even though they seem able to spec-up a new car from all the options available (if they can afford a new car that is..). Sorry for rambling Sleepy

My personal thoughts about the styling of the preamp are to use a Proprius-like case that is 380mm (industry standard?) wide, 76mm high (with 14mm feet to make it 2U), and 254mm deep.

The front panel would need to be thicker at 6mm so as to counterbalance the tug of the interconnects at the back. It can be recessed-in or it can be as per the Majestic - stuck on the front.

As for the remote, I'd been developing my own a couple of years ago, using different technology to regular remote controls to try and prevent interference with other products. There are so many remote control codes for standard remotes that I would probably get it all wrong...

To add input selection will require me to make it addressable to generate more codes than a simple up/down for volume control.

That would not be compatible with a standard manual switch input selector on the front panel of the preamp! Such an input selector would have to follow the same routine as the remote, and switch by relays - the only visible indication of selected input possible would then be by using LEDs.

Such a level of automation adds complexity 'inside the box'. It also demands power: whereas all the cicuitry of a manually controlled preamp could be easily powered by one PSU1, the power budget is increased considerably by the automation, and then the question of how signal purity/quality will be impacted has to be broached.

One answer would be to run the automation on rechargeable battery, and in such a scenario, the remote itself could be made rechargeable when not in use. However, if used repetitively, the automation of the preamp could fail due to the battery discharging faster than it could take on charge.

Another option is to use a more powerful external power supply than the PSU1. The Proprius power supply has proved itself capable of good audio reproduction: it is switched mode and self adjusting to any AC mains.

Some may ask why a remote power supply, or even why not make a bigger PSU1? The answer to these questions lies in global safety and environmental standards: not all of those inviting pieces of hi-fi equipment you see are innocent! Most break the law in one or more countries around the globe.

Not every manufacturer who uses a built-in power supply conforms to world IEC standards, which they should if they sell their products outside Europe. In fact, it is illegal for certain pieces of equipment to be sold in some countries unless they are certified to one standard or another. Add to that the environmental standards and mains derived power supplies are a real headache to those who bother to comply.

Some decide to risk it. I know of at least two quite well-known makes who do. I also know of at least two makes who are very safety and environmentally conscious - one being me!

It is exremely expensive to comply and so a bigger PSU1 could cost between £10K and £20K to obtain approval - likewise for a built-in power supply.

The above being a good reason why a few brands outsource, using external power supplies which carry the required approvals.

Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bi-wire Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jun 2014 at 3:00pm
Originally posted by Graham Slee Graham Slee wrote:

Hi Peter, I'm not thinking of putting tone controls on the preamp.

I made a suggestion of a 'card frame' for people wanting to 'design their own system'. It would be very expensive for me to develop a series of 'standard' cards, but it would not be the first time - broadcast studios were often done this way. However, I don't think the average hi-fi customer would have a clue what I'm talking about, even though they seem able to spec-up a new car from all the options available (if they can afford a new car that is..). Sorry for rambling Sleepy

My personal thoughts about the styling of the preamp are to use a Proprius-like case that is 380mm (industry standard?) wide, 76mm high (with 14mm feet to make it 2U), and 254mm deep.

The front panel would need to be thicker at 6mm so as to counterbalance the tug of the interconnects at the back. It can be recessed-in or it can be as per the Majestic - stuck on the front.

As for the remote, I'd been developing my own a couple of years ago, using different technology to regular remote controls to try and prevent interference with other products. There are so many remote control codes for standard remotes that I would probably get it all wrong...

To add input selection will require me to make it addressable to generate more codes than a simple up/down for volume control.

That would not be compatible with a standard manual switch input selector on the front panel of the preamp! Such an input selector would have to follow the same routine as the remote, and switch by relays - the only visible indication of selected input possible would then be by using LEDs.

Such a level of automation adds complexity 'inside the box'. It also demands power: whereas all the cicuitry of a manually controlled preamp could be easily powered by one PSU1, the power budget is increased considerably by the automation, and then the question of how signal purity/quality will be impacted has to be broached.

One answer would be to run the automation on rechargeable battery, and in such a scenario, the remote itself could be made rechargeable when not in use. However, if used repetitively, the automation of the preamp could fail due to the battery discharging faster than it could take on charge.

Another option is to use a more powerful external power supply than the PSU1. The Proprius power supply has proved itself capable of good audio reproduction: it is switched mode and self adjusting to any AC mains.

Some may ask why a remote power supply, or even why not make a bigger PSU1? The answer to these questions lies in global safety and environmental standards: not all of those inviting pieces of hi-fi equipment you see are innocent! Most break the law in one or more countries around the globe.

Not every manufacturer who uses a built-in power supply conforms to world IEC standards, which they should if they sell their products outside Europe. In fact, it is illegal for certain pieces of equipment to be sold in some countries unless they are certified to one standard or another. Add to that the environmental standards and mains derived power supplies are a real headache to those who bother to comply.

Some decide to risk it. I know of at least two quite well-known makes who do. I also know of at least two makes who are very safety and environmentally conscious - one being me!

It is exremely expensive to comply and so a bigger PSU1 could cost between £10K and £20K to obtain approval - likewise for a built-in power supply.

The above being a good reason why a few brands outsource, using external power supplies which carry the required approvals.

 
Thank you, Graham, I understand now.
 
Separately, can I raise the subject of stepped attenuation rather than the Alps type volume control and see what reaction that gets .... Ermm
 
Peter

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jun 2014 at 7:20pm
Originally posted by Bi-wire Bi-wire wrote:

Separately, can I raise the subject of stepped attenuation rather than the Alps type volume control and see what reaction that gets .... Ermm


Don't know how I'd drive a rotary switch with a motor, so a decent pot would be best for remote control.

I'd agree that in using stepped attenuation the signal 'passes' through the same fixed resistors (or would do) as the rest of the circuitry, and not some screen-printed variable conductivity carbon deposit on a piece of circular paxolin to achieve an 'audio-taper'. No matter how good the wiper finger is (or fingers if thinking of the 'blue velvet' are), there will always be some mismatch.

The only way to remote this would be a board full of relays, but then what about contact resistance? Relays don't have the requisite wiping action and if you look at signal relay specifications you'll notice one about minimum contact current. The best do 10uA but how much current would flow where the signal was -60dB?

Likewise, when switches wear they're going to have the same effect.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bi-wire Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jun 2014 at 11:14am
Originally posted by Graham Slee Graham Slee wrote:

Originally posted by Bi-wire Bi-wire wrote:

Separately, can I raise the subject of stepped attenuation rather than the Alps type volume control and see what reaction that gets .... Ermm


Don't know how I'd drive a rotary switch with a motor, so a decent pot would be best for remote control.

 
Yes, I thought that would be your reaction. I don't have an answer either Ermm. I guess if we have to have remote operation (which I accept is pretty well essential for the market as a whole) then it has to be the best possible pot you can realistically source.
 
What about stepped attenuation and no remote as an alternative implementation, or is this just introducing another unnecessary complication when it comes to marketing, etc?
Peter

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Frostg Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2014 at 1:57pm
Why do we have to have a remote?
If using vinyl you have to get up to turn sides, unless you have jukebox.
So i don't understand why it is not possible to get up to set volume how you want it. 
We seem to want to over complicate everything.
Cry
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