XLR Balanced lines for turntable to preamp, and New Preamp Design update.

[GeorgeP]

As an Electronics Engineer I designed a new distortion less Preamp with Ambience rear channels... similar to the Phase Linear 2000, but much much better.
The overall design is 99% complete. Offered as a kit, also semi kit with tested PCBs, and also complete built and tested. That is posted elsewhere on this site.
The front panel and real panel are designed and look beautiful. Attached below. I'm added an array of XLR balanced inputs and outputs for best noise immunity. Those PCBs have just been ordered.
I also just designed a Balanced XLR output driver with a perfect RIAA Curve. Now you can put the turntable up to almost any length of XLR cable at Line level to a preamp with XLR inputs, or...use the XLR balanced Line receiver I also designed for this... changes it back to un-balanced RCA Jacks at the preamp if you don't have XLR connectors on the preamp. When this effort is done, I will release everything as kits with options as you want.
I work full time at Brookhaven National Laboratory and work on this project outside the job... Its a labor of love! I just added a few updates on the design for XLR connectors.

 

[wattsabundant]

Well, you've certainly been busy. A few thoughts:

• I'm not sure what the quality of the pots are, but it is a minor concern for reliability with them mounted directly to the board. Of course, plated through holes help.
• I think very few people will want to buy the equipment to work with surface mount components. Of those who would consider it, even fewer have the skills to work with it.
• What is the purpose of the 10 watt amplifier? Headphones? Ambiance? It's probably overkill for headphones. As a main amplifier it is undersized.
• The speaker connectors are binding posts? 1/4" jacks?

 

[J!m]

SMDs certainly come with a steep learning curve but if I can do it (eventually) I think people with actual skill can.

 

[GeorgeP]

Well, you've certainly been busy. A few thoughts:

• I'm not sure what the quality of the pots are, but it is a minor concern for reliability with them mounted directly to the board. Of course, plated through holes help. The
• I think very few people will want to buy the equipment to work with surface mount components. Of those who would consider it, even fewer have the skills to work with it.
• What is the purpose of the 10 watt amplifier? Headphones? Ambiance? It's probably overkill for headphones. As a main amplifier it is undersized.
• The speaker connectors are binding posts? 1/4" jacks?

POTS:
The quality of the pots were a nice surprise... feel very smooth and produced unnoticeable noise! I saw no "scratchys" ON THE SCOPE AT ALL when making measurements.
SMT:
It will be offered as all kit, or...tested sub-assemblies, or a total built/tested product. It a chance to learn and offer reduced price at the same time. The smallest part is 1206 so not bad. The XLR balanced board is a challenge because that chip is a tighter pitch package. I may not offer that assembly as a full kit but built and tested. TBD. I will be building that board up when the board arrives, and see. The chips and semiconductors are soldered with SN42 self-cleaning solder paste. Easy, once you get the hang of it. all other parts are SN63 self cleaning solder paste. The can also be installed with a fine tipped standard soldering Iron. I built the first prototype that way. At that time, I didn't have the HOT AIR tool. Now, thats all I use!
10 Watt Amp:
It drives the headphone, even the power hungry 8 Ohm types. I love the amps, more than enough for the bedroom. with typical vented speakers on the market these days. I like loud RockN roll, and I find the power level good for that in the bedroom. Its a 25W peak... 10W RMS. the power supply is just sufficient for 10W RMS all channels driven. Music peaks is 100W total for all four speakers. The connectors are TWO 1/4 Phone jacks. I had NO Space for binding posts! Note: When the jacks are not used...the +/- 17VDC regulated DC sources are shut off.
Ambience:
The rear channels contain the Ambience signals, derived with a difference Analog "computing" circuit. I improved the version that the Phase Linear 2000 preamp uses. I think it sounds very cool...and level adjustable. Perceived loudness is like being at the recording source room...the sound is everywhere, just like at a concert hall, or stage. I bought a Phase 2000 a few years ago, refurbished it with the better chips and decided to add that function to my design. Till you hear it, you won't believe it. Now, regular 2-CH sounds almost dead. I think that's why surround sound 5.1, 7.1 etc is sort of standard for home theater. For me, and others who like their vintage stuff.... this a very cool way to go clean analog, and easy to add on.
FYI: My system...Phase Linear 700 for the front AR9s Bi-amped with Phase Linear 400 series 2 for the upper drivers (Raine 2-way electronic crossover with adjustable delay for phase correction. Phase Linear 400 Driving the Rear AR90s (smaller AR9s), not Bi-amped with the ambiance outputs.
All Phase Amps are upgraded and DC protected.

The XLR balance RIAA driver board that outputs line level is in the works. I'm prototyping that in a few weeks, is another fun project. Imagine having a turntable 100 feet away, and no hum or added noise! Well that the add-on I'm trying to work out. For now, the phono inputs are RCA only.
Sorry for the "wordy" responses. Its a labor of love!
George

 

[GeorgeP]

SMDs certainly come with a steep learning curve but if I can do it (eventually) I think people with actual skill can.

Agreed. The assembly instructions are extremely helpful in the smt learning process. If anyone wants to try a subassembly first...I would suggest the Power supply, then the precision peak detector display...Then decide if you want to take on the main preamp board. That board is 1206 resistors for the smallest parts...can be done with tweezers and a fine tipped iron. I did my first prototype preamp that way, no big deal. I'll add soldering techniques to the manual. I did not add 0805, 0402 or dreaded 0201 sized parts. No reason to. Its not a cell phone! I wanted this to be a nice experience, not a super frustrating nightmare. A steady hand helps ALLOT!

 

[nakdoc]

You will need to remain underground since the preamp is not UL certified. I'd advise deleting the AC outlets to reduce potential liability.