JM-70H The Valve Preamp with Shunt Regulator

Started a year ago, following the first successful project JP-200 clone valve preamp,  another valve preamp JM-70H has been created. It took more than 10 months in the final tuning session. During the period, quite a number of experienced audiophiles were invited for serious listening and many suggestions were received in regards to the sound quality of this preamp.

The design is based on the legendary Marantz 7 valve preamp with completely new designed power supply section. JM-70H employed two EI transformers supplying more than enough AC power to two separate SSHV2 shunt regulators, one in each channel for high voltage supply. As a result, the preamp sounds much more transparent, detailed and energetic than any of those with CRC/CLC or serial regulator designs. JM-70H is a preamp that has achieved a level of performance that can be favorable for many experienced audiophiles for the cost of an entry level preamp of big names.

From PCB design to selection of components, JM-70H is not compromised at all. Quite a number of expensive components are used , such as Amrg, Kiwame carbon film resistors, and Mundorf Evo oil , Wima MKP capacitors. All PCB used are heavy duty 2.0mm thickness with 2OZ copper FR4 boards. The chassis is fully made of aluminum with the front panel thickness being 8mm. All panels are completed by CNC machine.

Basic Specification

Tubes Used: V1:  Tungsol 12AX7 Golden Pins,  V2/V3:   JJ 5751
Filament Arrangement : 6.3V AC
Input:  3 sets of RCA for CD/DAC/AUX signals
Output: 1 set of RCA with automatic delay on start up or muting manually by push button on front panel.

Gain: 20db
Output Noise Level:  0.08mv (when input shorted to ground)

Power:  230V/240V
Power Consumption: 40W

For more info or an arrangement of trial,  please contact sales@consoletronics.com

We are Sydney based audiophiles in electronics business.


SSHV2 Shunt Regulator:

 

 

Main Board

 

 

 

  Input Module

 

 

Top view of JM-70H

 

 

 Back View of JM-70H

 

 

 Front View of JM-70H

 

Packaging

 



JP200 Clone - my first audiophile valve project

Based on Jadis JP200 Valve Pre-amp with some modification 

   
Features:

Dual Mono and separate power supply chassis design.

2X EI type power transformers

2X separate tube based regulation circuit boards for B+ high voltage supply involving 2X EL84 and 2X EF86 tubes.

All filament supplies for the main channels are DC regulated and supplied to output and amplification stages separately in each channel.

3X carefully matched and balanced TungSol Gold Pin reissue 12AX7 tubes are used for each channels.

Coupling capacitors are Germany ‘s Mundorf supreme and US made Audio Cap’s RT grade.

All power filtration caps are Nichicon KX grade.

All resistors used in power and preamp sections are audiophile grade Japanese Kiwame 2W carbon film.

Volume is controlled by a ladder type attenuator with all Dale military grade resistors for precise volume control and balance.

Capable of feeding up to 4 sets of stereo signals selected via the professional Takamisawa signal replays

Output signals can be muted by the push switch in the front panel and is about 90 seconds time delayed when the preamp is switched on.

                                                                         

                                         

                                     

                                                                            

                                          

                                     

                                   

                                     

                                         

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With the new dashboard update 14717 or14719, the way used to disable the RGH chip does not work any more. After the update you have to physically disconnect the +3.3V from the the RGH chip to be able to boot oringinal nand. Adding a switch is a simple way but a little messy as you would have to drill a hole on the Xbox360. Some people used a 3.3V relay instead of a switch. But 3.3V relay is not easy to find.

Here we have an electronic solution for the swtich without using a relay or physicall switch. It consists of 2 transistors and 1 resistor as show in picture below:



When the level of pin 2 on Cygnos switch that used to disable RGH chip is Low, its to boot stock nand and High to boot RGH nand. So, when the pin is on High, it turns on Q1 making the base of Q2 low , which in turn switch on Q2. The RGH chip then gets +3.3V power via Q2 that connected to +3.3V rail. The 10K resistor is used to limit the current when Cygnos swith pin2 is on High. it works perfect when tested on a slim Xbox360.

Daul nand with Cygnos360 V2  E on a Slim Xbox360

Cygnos360 V2 E is so far the best device to install dual nand boot for Xbox360 especially for the Slim version. It does not require to cut the tiny CE trace on the motherboard in order to switch between stock nand and hacked nand.

When switching to stock nand, the Glitch chip needs to be disabled. A lot of installs used a replay or toggle switch to interrupt the ground wire. But this can be done by modifying the cpld code without using the a replay or any methods to interrupt the ground wire.

Installation can be viewed at www.consoletronics.com/images/dual_nand.jpg