Enhanced Pultec 电路图.pdf

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1、Freitag, 23. Januar 2009 DIY | studio | mail Enhanced Pultec Equalizer Project Enhanced Pultechttp:/www.nrgrecording.de/html/enhanced_pultec.html 1 of 52/04/11 11:24 AM RadioFans.CN 收音机爱 好者资料库 Description Here you can get the files for a very easy diy project (hopefully) ;-) Its the Filter Circuit o

2、f the well know Pultec Program Equalizer EQP1A. The circuit is not original. No tubes and other dangerous or expensive parts are involved here. The idea was to have a circuit close to the original (the beloved inductor based filter circuit from pulse technologies) but with easy to find components. I

3、n the beginning the filter was passive. The gainstage was added later. Id seen pultecs without tubes but with a discrete opamps. So if the pultec would be designed these days. maybe they wouldnt use tubes, too? 0:-) But thats a question for Eugene Shenk from Pulse Technologies himselfs. ;-) If you w

4、ant the tube version of this EQ you could either google for “pultec eqp” and youll find informations about how to build it with tubes and close to the original. Another Idea is to use the nice SRPP Gainstage from Jakob Erland (Gyraf Audio). So you dont need the opamps pcb. But everything will be muu

5、ch more expensive. Lundahl Transformers, Tubes, Mains transformers. The PCB Layout The pcb layout of the filter pcb fits on a 160 x100mm pcb (eurocard). The gainstage/input output stage fits on a half eurocard format. There are pinouts for two inductors. You have to use one at a time of course! Real

6、ly, the sound will not be better with two inductors! ;-) Here you can download the pcb files and component placements: Layout for the Filter PCB Layout for the Gainstage PCB The inductor The pcb layout is made for RM8 cores from “epcos”. Max (ioaudio) can make inductors, too! Theyll fit into the pcb

7、. You can also wind the inductors yourselfs. Its not that hard. This can be done by hand. Steffen has some informations about how to wind your own inductors on his website: Enhanced Pultechttp:/www.nrgrecording.de/html/enhanced_pultec.html 2 of 52/04/11 11:24 AM RadioFans.CN 收音机爱 好者资料库 http:/diygall

8、ery.de/DIYsites/inductor.html If you want to diy the inductor: You have to calculate the turns for each tap/pin. It depends on which core material youre using. There are different core materials available for the RM8 core from epcos. If you choose a higher value core material youll need less turns a

9、nd vice versa. If the core is filled with wire but you need to add some turns. either your wire thickness is too big or your core material is too low. (or both) ;-) 1600nH and 0,14mm wire worked for me. This may work for you. But measure the values in the end if theyre right: 26mH=127 turns 39mH=156

10、 turns 78mH=221 turns 155mH=311 turns 312mH=442 turns The capacitors You can use wima capacitors, orange drops or styroflex capacitors if you want. The layout is made for wima capacitors. Some capacitors are wired in parallel because the arent available for with the exact value. You could match some

11、 capacitors if you want to have the 100% correct value. Capacitors can have around 20% tolerance. Potentiometers and switches You can use what you like. Lorlins will do. Its nice to have a shortened switch on the low frequency switch. That because youll here some plops when switch through the freque

12、ncies. (only when the potentiometer is clockwise). Grayhill or elmas will do a great job, too. Manley are using Grayhill for example. The Gain Stage The PSU is on the gainstage pcb. You can use 7818/7918 (18V Voltage Regulators) to use NE5532 opamps or 7824/7824 (24V Voltage Regulators) if you want

13、to use burr brown OPA2604 opamps. Youll need a power transformer with two secondary windings. 18V AC/AC should work for 18V. There is a gnd lift circuit on the board. You can add a switch on the backside of the case. Connect “chassis gnd” to the chassis. Dont forget to remove the powder coating or l

14、aquere where you want to connect the gnd at the case. If you want to have a power switch, just switch one phase of the mains connections. The earth of the mains connector must be connected to the case all the time! Maybe you need to adjust the gain when the filter is turned on. Replace the 18K resis

15、tor next to the “OUT, GND, IN1,IN2” connections with a trimpot and adjust the level while the filter is NOT in bypass mode. Input and output level must be the same then. Either you just leave the trimmer in the circuit or measure the resistor value and replace the trimpot with a resistor. If your se

16、e smoke on the pcb something is wrong. Probably the 10R resistors next to the voltage regulators are on fire ;-) They act like a fuse. There is a short somewhere. Connect your multimeter to GND and then measure the 10R resistor at the side where the ground lift switch is. if there is a short (e.g. l

17、ow resistance on the multimeter) find the short and remove it. :-) Modifications Instead of having one switch for the low frequency you can use two lorlin switches. You can change the cut frequency and the boost frequency seperately. (if this helps) ;-) Enhanced Pultechttp:/www.nrgrecording.de/html/enhanced_pultec.html 3 of 52/04/11 11:24 AM Enhanced Pultechttp:/www.nrgrecording.de/html/enhanced_pultec.html 4 of 52/04/11 11:24 AM Enhanced Pultechttp:/www.nrgrecording.de/html/enhanced_pultec.html 5 of 52/04/11 11:24 AM