Preamp preference

Phase Linear 2000.
Separate tone and turnover frequencies for each channel, with that beautiful Ambience output for the rear channels.
I did upgrades to mine, and also designed a super better version of it (GPulseLinear 2000, Kit or assembled and tested) from the bottom up. The attachment is a general overview:
Uses "Sound Plus" zero distortion and super low noise Op-amps. Just finishing up the XLR balanced interface PCB this week. Then ordering the front and rear panels that are shown in the attachment. It sounds awesome.
 

Attachments

Interested in info on your balanced to single-ended converters, George...
 
I'll be testing the receiver over this weekend. Its built, just waiting for the dual phono connector coming tomorrow.
The Driver converters, in a few more days...with RIAA curve network in the feedback path using the same chip. The Non-RIAA curve driver will be tested next. Should be awesome. I'll post the receiver first.
I was thinking of designing a "duplex box" with Mutiple channels, one with the RIAA phono curve driver. Maybe add relay switching for selections of inputs to one output...TBD.
 
I'm just interested in the balanced to single ended converter, with emphasis on noise level within the audible range.

It seems most of these sorts of things add a bit of noise... Anything above -100dB would be too high for me personally.
 
usually true with the added noise...but the chip is spec stated at -104.7dBu Un weighted, with the laser trimmed internal resistors! The Distortion + Noise -120dB (22dBu, 22KHz bandwidth). The added external components are not in the signal path, except for the DC blocking Nonpolarized caps on input and output to protect external sources in case of extreme off-set, and one 50-ohm series stability resistor for driving capacitive cables / load. Wide bandwidth @ 2.7MHz, with the internal EMI filtering.
Short circuit protection. Bi-polar supply. The RIAA curve converter all high impedance time constant circuit, so little current = "no" noise contribution. That should be fun to verify!
 
I've had one Carver and two PL preamps. PL's were the 3300 and the old 2000. Never had the 4000, not sure I would go that route. Out of all 3 Bob Carver pre's I have had I preferred the 2000 the best.
 
I have a few Hafler preamps D110s. Sound really really good, but those push in switches become very noisy and hard to fix. I bypassed the tone "in/out" switch since at Center Tone controls measured flat response anyway. I also bypassed the loop in/out switch, so now loop in now bypassed with jumpers on the back panel. All is much better and very quiet. The PL2000...same issues with slide switches... but cleaned up OK, but still "pesky".
My design GPulseLinear-2000 uses sealed toggle switches specified for almost zero Ohm loss at low currents...should last forever. They are expensive but are noiseless. The 4000 has each stage "DC blocked" with caps...not the best way to go, and plug-in boards with noisy connector issues. Not a fan of that one
If you like the PL-2000, you will love the latest technology used in my GPulseLinear preamp. Same functions plus more, and much better specs. 2U high rack mountable chassis.
cheers!
 
J!m said:
Popcorn at the ready!
Click to expand...
Hi. I tested the XLR Driver and receiver with an XLR cable between them. I did have a few issues with a land trace that went missing...and fixed it. That driver chip is distortion LESS. below the test instruments measuring capabilities of .001% . Noise is NO contribution at the floor level of the test instruments at their highest gain settings. That was done late last night. I want to check the RIAA Driver with this, maybe tonight or tomorrow. The tests are with BOTH driver and receiver connected. All looks perfect so far. After the initial tests, I'll clean up the setup, and post the data and pictures. That "SoundPlus" Chip from TI is unbelievable. Clean performance in every way, but a pain in the ass to solder down. I used SN42 "No-clean" solder paste with a hot air iron. Look at the attached specs on this badboy!! I think I will only provide a built and tested version, since it would be very tough to assemble as a kit. This added XLR feature to my GPulse2000 Preamp design will make it super high end product.... I hope!
 

Attachments

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The 4000 is a disaster waiting to happen. It was designed before double sided boards with plated holes were available. It has a mother board with male connector pins and daughter boards that plug in. The pins on the motherboard have cracked solder joints.
  1. If a 4000 is going to be used it is a must that every solder joint on the mother board is resoldered.
  2. The I/O jacks suffer the same issue as the motherboard. They may be hard to find. I bought out a pile from a surplus shop last year.
  3. Roughly 25 years ago I fought with a 4000 for hours and finally sent it to ED. He found a cracked bass/treble pot. As I recall the pots also support the mother board making them subject to failure.
  4. There are a lot of TO92 transistors that are subject to failure or noisey.
  5. If these issues can be overcome a 4000 may be an option.
 
wattsabundant said:
The 4000 is a disaster waiting to happen. It was designed before double sided boards with plated holes were available. It has a mother board with male connector pins and daughter boards that plug in. The pins on the motherboard have cracked solder joints.
  1. If a 4000 is going to be used it is a must that every solder joint on the mother board is resoldered.
  2. The I/O jacks suffer the same issue as the motherboard. They may be hard to find. I bought out a pile from a surplus shop last year.
  3. Roughly 25 years ago I fought with a 4000 for hours and finally sent it to ED. He found a cracked bass/treble pot. As I recall the pots also support the mother board making them subject to failure.
  4. There are a lot of TO92 transistors that are subject to failure or noisey.
  5. If these issues can be overcome a 4000 may be an option.
Click to expand...
Thanks.
This is the kind of feedback I was looking for. :-)
 
GeorgeP said:
usually true with the added noise...but the chip is spec stated at -104.7dBu Un weighted, with the laser trimmed internal resistors! The Distortion + Noise -120dB (22dBu, 22KHz bandwidth). The added external components are not in the signal path, except for the DC blocking Nonpolarized caps on input and output to protect external sources in case of extreme off-set, and one 50-ohm series stability resistor for driving capacitive cables / load. Wide bandwidth @ 2.7MHz, with the internal EMI filtering.
Short circuit protection. Bi-polar supply. The RIAA curve converter all high impedance time constant circuit, so little current = "no" noise contribution. That should be fun to verify!
Click to expand...
 
Update:
I had to spin another board for the Phono version. The balanced converter chip had onboard gain fixed...so the RIAA feedback did not work. My oversight. I added the preamp chip that I already use in my GPulse2000 to a new design... so when that comes in I'll test it. Its a 3 chip design. I have the Receiver board working very very nice. I'll be putting up 3 boxes:
Box # 1. Phono to XLR RIAA curved perfectly as a stereo signal driver for noiseless and distortion less long cable runs. This board will also have line level unbalance RCA outputs, for those who just want the preamp to line level function.
Box #2. RCA unbalanced to XLR Balanced as a stereo signal driver.
Box #3. XLR Balanced to RCA as the stereo signal Receiver.
All three will have the internal 120VAC input supply (+/- 15VDC). I have the chassis designed.

Also: The chassis came in for the full GPulse2000 Preamp. Looks BEAUTIFUL! Wiring it up with all the tested boards. I fully test it this week all enclosed shielded up. Have a look. The interconnect is in final edit. Everything is optional.
 

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  • FRONT VIEW.jpg
    FRONT VIEW.jpg
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  • REAR PANEL VIEW WITH XLRS.jpg
    REAR PANEL VIEW WITH XLRS.jpg
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  • TOP VIEW COVEER OFF.jpg
    TOP VIEW COVEER OFF.jpg
    1.3 MB · Views: 18
  • SCHEMATIC PAGE 8 WITH XLR 2-28-2025.pdf
    SCHEMATIC PAGE 8 WITH XLR 2-28-2025.pdf
    253.5 KB · Views: 3
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