NEW PREAMP DESIGN

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X usaf electronic tech.
#41
I just received the first PCB today.
This...should be the lowest distortion, lowest noise preamp at any price! THE BEST AND LATEST OP-AMPS, LAYOUT AND SIMPLE TO BUILD AND REPAIR.
The latest Lowest distortion, lowest noise op-amps available. Film caps in signal path, Regulators, careful grounding, separate tone controls and turnover frequencies for each channel. And... the phase linear Ambience output cicuit for rear channels just to add something special. No digital processing!
WILL START PUTTING PARTS ON IT THIS WEEKEND. Will build power supply and regulstors first, and test it.
Then all passive parts installed. The last parts installed, the 4 super op-amps. That way...no chance of static damage.
Then...full bench testing. Stay tuned...
View attachment 77591
I would be interested possibly I have 2000s2 I'm using .
 

GeorgeP

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#43
I’m tuned!

I hope @wynpalmer will stop in at some point. He designed op amps in his former life and knows a thing or two about them. His work on the phono preamp speaks for itself.

I was trying to get him to bring his knowledge and experience to bear on my concept but he decided to stop pursuing it. There was nothing unique about my concept but bringing ideas I like into one package- sort of like what you have done with the ambience circuit.

I specified analogue VU meters for each channel, level trim for each input (for matching) and of course a tape loop.

I posted PDFs of the faceplate design but I’d have to dig those out because it was about a year ago he and I were talking about it.
I did add the trim pots to match each channel for gain, dead nuts.
 

GeorgeP

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#47
Peak detector working nice. Added a sensitivity switch for lower listening levels...1V RMS is max...10V RMS is max for the preamp (30vac peak to peak).
Im adding a very low distortion 10 watt/channel stereo amp option / power supply option for bedroom speakers. Just a plug in. Remove preamp only supply, and plug this in, and add output binding posts a on rear. Making it an easy addition...so the Rev-P2 preamp board getting the needed connectors for either option. Also added a balance control, and moved the AC on switch off the pcb. Saw a low level hum on the left channel...so thats fixed. The new balance control will be to the left of the volume control. The Ambience control, to the right of the volume control. Nice.
Ill upload a better pick of the front panel control locations later.
Headphone jack will be on right side.
Box is 16" wide, 2" high, 8" deep. All black painted steel. Knobs will be silver.
Im starting to drill the box to put the circuits in. This pic shows the LED Peak level indicators...pcb is on inside of course! Just a pic for reference. Vertical pcb and contol heights for drilling holes.
 

J!m

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#49
If I may make a suggestion, George:

Increase the diameter of the volume control. A few beers in and you'll be turning the wrong knobs.

I see how you laid this out with the controls, but I would probably still locate the main gain knob on its own on one side (even if a timing belt inside operates the pot in the optimal location). But a true resistor ladder stepped attenuator is SO much quieter than a pot I don't expect to ever design an enclosure with a potentiometer ever again. It's night and day.
 

GeorgeP

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#50
A stepped attenuator...nice. I'll check. Could also be a digital encoder for a D to A analog converter. To complicated. Then...you can use a remote for drunken dudes who wont get off the couch! Lol. These pots sound nice and feel nice, and can be easily cleaned if needed. Not sure if the came style knob comes a bit larger. Ya could always out a big bold black "V" on it... Lol. I did place it at the center... under my Logo!
 

J!m

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#51
For sure you can use a remote with a few relays and resistors to create a remote attenuator. I think there are kits on eBay that could be grafted in. Selection can be handled similarly.

I suspect an AP could drive a Bluetooth module and you could have a clean faceplate with no knobs at all if you wanted; operate from any smartphone. That way you are not likely to lose the remote.

I prefer actual switches and like the discussions on AK about Wyn’s new design if I get up to flip a record I can get up to adjust the equipment.
 

MarkWComer

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#55
Surface Mount Devices, they are resistors, capacitors, ICs, inductors, etc that have smaller dimensions which allow smaller designs and higher speed automation for assembly.
Extremely short circuit trace distances. Without SMDs you wouldn’t have the small devices we have now- cell phones for example. Gigahertz speeds in our computers would also be impossible.
 

Gepetto

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#56
Extremely short circuit trace distances. Without SMDs you wouldn’t have the small devices we have now- cell phones for example. Gigahertz speeds in our computers would also be impossible.
Not impossible Mark, just more careful design required. Multi-Ghz based pairs often run more than a foot or more in many high speed server and switch designs.
 

MarkWComer

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#57
Not impossible Mark, just more careful design required. Multi-Ghz based pairs often run more than a foot or more in many high speed server and switch designs.
But in that case you’re referring to cable runs, not internal devices. Of course, computers, switches, and routers have their own internal circuits that run at multi GHz speeds, but interconnects also require cabling (cat5, cat6, etc) that can handle those transmission speeds.
 

Gepetto

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#58
But in that case you’re referring to cable runs, not internal devices. Of course, computers, switches, and routers have their own internal circuits that run at multi GHz speeds, but interconnects also require cabling (cat5, cat6, etc) that can handle those transmission speeds.
Nope
 

Gepetto

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#60
Well… guess I’m wrong then…
Diff pairs are run on board to board connections inside switches and servers, not easy to implement but is done.

32G fiber channel and 56G IB are common PCB runs as well as Gen5 PCIe running nearly double that rate. When it has to span to a peer board, those runs can be quite long.

Cables and board are required to handle these transmission speeds. Length hurts so keeping runs as short as possible minimizes losses.
 
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