| Transformer Coupled Pre-Amp Kit | ||
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Main mail to
[email protected]
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 This project is to be offered in a KIT form using the 5842 tube with transformer coupling. The kit is expected to be sold around 200usd without a chassis. But would include everything needed to build the project. List of materials included
*Optional upgrades would include the shunt regulator, chokes, current regulation for the heaters, Better components (Hovlands or AuriCaps or maybe PIOs). More pictures to come. I am currently looking for a suitable chassis for this project so they might be available soon.
Pictures of the prototype
Optional tube shunt regulator To further evaluate this design I will invite some members of my audio society to audition this pre-amp and to give their comment. A much better evaluation can be done then. Pre-Amp Characteristics Primary this design for audiophiles who utilizes long pre-amp cables or drive solid-state equipment or even drive headphones of 300 ohms. The pre-amp is design for audiophiles who wants the tube sound and as well as the deep bass. Good bass is achievable with this design as the output impedance is very low. Gain of the pre-amp is 2.5 which makes this design easy to used with solid-state equipment with their high sensitivity. This is an quote from a friend who has audition this amp without the latest upgrade. Why battery biased, avoids the necessity of a bypass cap (has to be good quality for good sound) and the all the advantages of fixed bias without any of its negative effects. Also the battery gets charge by itself from tube when its running, free charger but only NiCad as the trickle charge is 20ma only. Power supply for the basic kit would be off a RCRC type with room for upgrade to RCLC type. Testimonials Good Bass, excellent midrange and high frequency-Tony Ho actually the comment was power, kengchow midrange and highs superb man transformer coupled is DA WAY to go- had to edit that for people to understand :) New Developments Currently design for 5842 but more designs will be made for other tubes such as
email me if you would like to add a tube type to try more info and upgrades will be added here. Notes about the preamp UnBalanced to Balanced via the usage of the transformer. The current source loads the tube. Suitable tube candidates should have low rp as well as high mu. The higher the mu the more the stepdown ratio can be used. For unbalanced to unbalanced do not ground the centre tap, - signal is connected to ground. This way the ground on the secondary is floating for reducing hum problems. Transformer Formulas Vp/Vs=Np/Ns Vp= voltage primary Vs= voltage secondary Np= Primary turns Ns= Secondary turns Current Ratio Ip/Is=Np/Ns Impedance ratio Impedance = (Vp/Vs)*(Vp/Vs) Current source should be loaded with high current better linearity.
A shunt regulator develop for the tube preamp. A CCS loading the shunt regulator. This is optional due to the complexity but reduces ripple in the B+ as well has the benefits of regulation Taken from Allen Wright Tube Pre-Amp book
With ripple on the B+, some amount of ripple would appear on the output A regulator helps to lower the output impedance of the power supply. This equates to better bass control and cloudiness over the standard LCLC or RCRC as the output impedance is set by the passive components only. Shunt regulator are bidirectional and can sink and absorb current to hold the regulation while series can only source current and not absorb it. Loading the shunt regulator with a current source kills interactions. Stops any signal, noise, rubbish appearing on the AC line or even the ground line. |
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