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Thread: New Preamp
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November 6, 2021, 04:23 PM #1
New Preamp
I posted last year about a DIY preamp I build using a Khozmo attenuator. I was really pleased with the SQ of that preamp which was a nice improvement over the Parasound JC-2 I had been using. I've really been enjoying building my own gear over the past couple years, so I thought I'd see if I could build another preamp pulling out all the stops (at least to the extent of my ability) to see if I could make a meaningful improvement.
It's taken me most of the year to complete this, partly because I've had to wait for boards and parts, and also because I had a couple of other projects I started in the meantime. But as of today, it's in my main system and sounding pretty sweet. Since it has no break-in and barely any warmup, I can't really assess how much of an improvement it is, but it doesn't seem to be a step back in any way.
The new preamp, shown in the upper right, is a two chassis design with a separate power supply chassis (middle left side). I gave DIYAudio.com contributor "Salas" top billing since I'm using output boards and shunt regulators that he designed.
The power supply has a custom Toroidy 400VA transformer with nine secondaries. These feed four independent +/- linear supplies with CRC filtering to provide independent DC supplies for each channel and for each of the two voltages required (+/- 12V and +/- 17V). A separate 5V regulator supply provides power for the Khozmo attenuator. This is connected to the main chassis with a 14 conductor umbilical cable.
The main chassis uses two 2-channel Khozmo relay-switched attenuator boards to support fully balanced input selection and attenuation. I'm using Takman REY shunt resistors and Audio Note silver tantalums for the series resistors. I set this up like my previous preamp with three balanced inputs and three single ended. After switching, these feed a unity-gain input buffer so that my preamp has an input impedance of 500K. With my previous preamp, I did not use an input buffer, so I had to use a much higher impedance attenuator, and I think this still caused some issues with my DAC which has a high output impedance. This input buffer also converts the single ended inputs to balanced before the attenuator.
The attenuator feeds two separate output stages. One is the same AMB.Org A24 buffer I used in my previous preamp, built with Z-foil resistors. This provides both a single ended and balanced output. I'm using the single-ended outputs to drive my subs.
The second output stage is a fully-balanced implementation of the Salas DCG-3 single-ended class A design. This is a very low distortion discrete high-current line stage (and headphone) amp that has predominantly second-order distortion. This is built with hand-match transistors and premium components (Z-foil and AN tantalum resistors, Nichicon and Wima decoupling caps, etc.).
All audio wiring is done with solid-core silver with PTFE insulation. Connectors are Viborg and Furutech.
The DC supplies from the power supply chassis are regulated using Salas UltraBib regulators. These are class A shunt regulators which provide low output impedance and very low noise, but require a fair amount of heat sinking.
I built the chassis primarily using custom designed powder coated panels from Front Panel Express. I used 6mm panels for the top and bottom. The thicker panels from PFE aren't perfectly flat, but overall I'm pretty pleased with the way it came out.Main: SGC SonicTransporter i9 Optical, Sonore Signature Rendu SE, Denafrips Gaia, Denafrips Terminator Plus, DIY Preamp, DIY 300B PSET Monoblocks, DIY GR Research Line Force with dual 4-stack servo subs, PS Audio Power Plant 12, AQ Diamond USB, Tubulus Argentus i2s, Iconoclast 4x4 UPOCC XLR, DH Labs Red Wave and Power Plus PCs, Kimber Select KS-3035 speaker cable
2nd: Auralic Vega G2, DIY Purifi amp, GR-Research NX-Studio speakers.
HT: Marantz AV8802a, Sunfire Theater Grand, Revel Performa F50/C50, Epson 5050, Stewart 92" Firehawk G4
Extra: Schiit Yggdrasil A2, DIY FirstWatt F5 Turbo monoblocks, DIY Neurochrome Mod-286 monoblocks, DIY Purifi monoblocks, DIY Preamp. Revel F30, Totem Mani-2.
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November 6, 2021, 04:27 PM #2
Re: New Preamp
Great job Jay, I look forward to your future posts on how it sounds.
Marty
Aurender N20 / SonicTransporter i7 / Roon
MSB Premier
Constellation Inspiration Preamp 1.0 / Mono 1.0
Dynaudio Confidence 50 / SVS SB13 Ultra
PS Audio Powerplant 15
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November 6, 2021, 04:43 PM #3Fleetwood Deville by Oswald Mills Audio, Vienna Acoustics Haydn Jubilee, Wharfedale Linton w/ stands, Klipsch RB-75, Klipsch RP-160M.
Job INTegrated. Luxman L-595aSE
NAD C 658 streamer.
First Watt SIT-3, Job 250 Monos, NuForce STA200, AkitikA GT-102 amp, ASL Wave monos, Dennis Had 45 monos. Absolute Audio Labs PCF 25 amp (improved First Watt F7 super clone)
Topping D90, RME Audio ADI-2 DAC FS, ModWright Ultimate Sony XA-5400ES.
Burmester 948, McIntosh MCLK12, Kimber Kable, Siltech, Cardas, Avanti Audio cables.
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November 6, 2021, 06:40 PM #4
- Join Date
- Mar 2018
- Posts
- 437
Re: New Preamp
Congrats, that's really nice work there and I'm glad it sounds great. I am also a DIY'er and have built many kits. However, none of mine have come out looking that nice.
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November 6, 2021, 07:00 PM #5
Re: New Preamp
Thanks for all the kind words. I really enjoy the process of the design and build, and it's very satisfying when it actually sounds good. That hasn't been the case with all my projects, but my hit rate is improving over time. With about five hours of operation so far, this preamp is sounding very nice. I can't wait to hear what it sounds like after a week or two of burn-in.
Main: SGC SonicTransporter i9 Optical, Sonore Signature Rendu SE, Denafrips Gaia, Denafrips Terminator Plus, DIY Preamp, DIY 300B PSET Monoblocks, DIY GR Research Line Force with dual 4-stack servo subs, PS Audio Power Plant 12, AQ Diamond USB, Tubulus Argentus i2s, Iconoclast 4x4 UPOCC XLR, DH Labs Red Wave and Power Plus PCs, Kimber Select KS-3035 speaker cable
2nd: Auralic Vega G2, DIY Purifi amp, GR-Research NX-Studio speakers.
HT: Marantz AV8802a, Sunfire Theater Grand, Revel Performa F50/C50, Epson 5050, Stewart 92" Firehawk G4
Extra: Schiit Yggdrasil A2, DIY FirstWatt F5 Turbo monoblocks, DIY Neurochrome Mod-286 monoblocks, DIY Purifi monoblocks, DIY Preamp. Revel F30, Totem Mani-2.
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November 6, 2021, 09:09 PM #6
- Join Date
- Feb 2016
- Location
- west Michigan
- Posts
- 713
Re: New Preamp
Super nice job.
The layout and implementation can be quite a challenge getting everything to fit and align properly without looking like you threw spaghetti in there.
Yes it is very rewarding to have a project come together and actually perform as expected.
Keep us posted.My System
Acoustic Revive RTP-4
Innuos Pulsar
Lampizator BALTIC4
Cary SLP-05
Pass XA30.5 or
Line Magnetic 845ia
Reference 3A Reflector's
Pr SVS SB3000 Subs
Cables & Tubes "subject to change without notification".
Complete system on battery power/solar
Core Audio Design Rack
DIY bass traps and custom curved diffusors.
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November 6, 2021, 09:12 PM #7
Re: New Preamp
amazing! congrats! ...i really with is had the knowledge to be able to build something that technically sophisticated. there is nothing more satisfying than a well executed diy project.
viking acoustics berlin r mk2 | almarro a318b + air tight atc-5 (phono) | clearaudio concept + virtuoso v2 MM | t+a dac8 dsd + diy transport + roon rock
alp-tone audio analog cables | core audio designs plyKraft 3L | hifi racks ltd podium t5-iii
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November 7, 2021, 12:12 AM #8
Re: New Preamp
Very nice! I also love that you are using Arek's attenuators. Arek Kallas is the owner of both Hattor and Khozmo which is his line mainly designed for DIYers.
McIntosh C49, MC152, MR85, R778 | T+A DAC 8 DSD | KEF LS50 Meta w/S2, KC62 (x2) | Rega RP8, Ania Pro, NEO PSU | Technics SL-1500C | Audio Technica VM750ML | Hexmat Eclipse, Yellow Bird, Molekula, Molekula Mini | Pro-Ject VC-E | Falcon NW PC Server (Roon Core & HQPlayer) | Microsoft Surface Pro 6 (Roon Controller) | Wyred 4 Sound ISO Recovery, DC Recovery | Abyss Diana Phi | Schiit Jotunheim 2 | Astell&Kern SE200 | Oppo BDP105
“One of the great challenges in life is knowing enough to think you're right but not enough to know you're wrong”
"You can't use reason to convince anyone out of an argument that they didn't use reason to get into"
― Neil deGrasse Tyson
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November 7, 2021, 10:45 AM #9
Re: New Preamp
Cool !
2chl : Vincent Sp331MkII, W4S STP-SE Stage 2, Kef 201/2, KEF 140, Vapor Breeze, Lumin, Bryston CD, BHA-1, Quicksilver Headamp, HD650, HD800s, HD820's, Dan Clark 1.1, Focal Stellia, OPPO 203, 105. ( Boxed up: Pass Xa-30.5, VPI Classic, Dynavector DV-20XL, Manley Chinook, Cadenza Bronze)
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November 7, 2021, 12:23 PM #10
Re: New Preamp
Really really nice!
Mark
Kharma DB9 Signature
Pass Labs XP32......incoming
Pass Labs X350.8
Esoteric N-05XD
VPI Avenger with Magnetic Drive
Manley Chinook Phono Pre
Ortofon Cadenza Black cartridge
Kharma Elegance speaker cables
Kharma Elegance interconnects
REL Subs
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November 8, 2021, 12:44 PM #11
- Join Date
- Mar 2018
- Posts
- 437
Re: New Preamp
The drama of powering a kit on for the first time is a bunch of fun. Pointing out to folks that you built it is the very best feeling ( if it didn't blow up ).
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November 8, 2021, 01:13 PM #12
Re: New Preamp
Looks great!
_______________
Mike
Amplification: MBL 6010D, MBL 9008A Monos
Analog: Kuzma R, Kuzma 4Point (11”), MSL Ultra Eminent EX
Phono Pre: Pass XP-27
Digital: Esoteric N01XD Esoteric K05
Speakers: MBL 101E MKII
Subwoofers: REL Carbon Specials
Conditioner: Shunyata Triton 3
Power Cables: Shunyata Sigma 1 & 2, Alpha 2, Delta and Venom
ICs and SCs: Wireworld Platinum 8
Rack: Artesania Exoteryc
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AudioShark forum is a leading forum site for High End Audio Discussion, Stereo System Discussion, Home Theater System Discussion, Best Home Stereo System Discussion, Home Theater Installation Discussion etc.
The AudioShark forum was created for sharing the passion of high-end Audio. We have Audiophiles from all over the world participating and sharing their knowledge. From novice to experts, you will find a friendly environment for discussing about High End Audio, Stereo System, Home Theater System, Home Stereo System, Home Theater Installation, Amplifiers, Speakers, Subwoofers, Integrated System, Acoustic treatments & Digital Room Corrections and many more.
At AudioShark, we also have incorporated an exciting Marketplace where members can peruse terrific buys on used gear, as well as meet dealers and discuss the purchase of new gear.
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Industry Participation Disclosure : The owner and administrator of Audioshark is the owner of Suncoast Audio LLC in Sarasota Florida. Suncoast Audio has a full brick and mortar presence in Sarasota with several great show rooms with many world class brands. More information can be found at http://www.suncoastaudio.com
Audioshark is a community of like minded individuals. Audioshark welcomes participation from all manufacturers and owners of all brands and products. It is our belief that online forums provide a community of like minded audiophiles and music lovers to encourage the growth of this wonderful hobby.
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It looks like you changed or augmented the power connector for the main board. Can you post a picture of what you did?
Lumin U2 Mini