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Topics - mensur

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Amplifier Discussion / 55W Fet Poweramp
« on: June 18, 2011, 09:53:18 AM »
Hi guys, I'm asking the advice for the  power amp that I designed.
It's a almost all FET discrete amp(except the bipolar current source and mirror, which only improves the linearity of the amp, and doesn't affect the sound).
I'm going to use the kind of Marshall MF350 negative feedback which is also used in MG series.

I know how to design voltage feedback, but I'm not familiar with current feedback.Can someone explain me how this feedback works, so that I can design PCB and share whole project with you guys.

Thanks

3
Preamps and Effects / Mesa GEQ Inductors - Gyrators
« on: October 11, 2009, 06:09:14 AM »
Hi guys,
I'll try to replace mesa inductors with gyrators, but I need some help:
1.Is the transistor emitter bias resistor fine(6.8K), or I should use another value?
2.Do I need to use dual voltage supply for the circuit?



Thanks

4
Tubes and Hybrids / Hybrid
« on: August 05, 2009, 06:33:17 AM »
Hi guys,
I made a hybrid amp. Roccaforte preamp and 100W MOSFET (TDA7294) SS amp.
I designed PCB (for the rocca and TDA):
Roccaforte Schematic & PCB.pdf
Some pics:







But I have a problem, I have noise and hum in the amp, here is sample:
Rocca Problem.mp3
and here is layout how i connected the amp,internally:
Rocca Layout.pdf

What can be the problem? Help me to solve this.


5
Preamps and Effects / Waves GTR3 Preamp
« on: February 19, 2009, 08:45:24 PM »
Hi guys, i need help!!!
I designed the preamp based on the interface manual specs:

OUTPUT BALANCED XLR:
Output impedance: 50 ohm
S/N: >105 @ line level, >70 @ mic level (S measured at 1%, 1 Khz, A Weighted)
Response: 20-20Khz , -3dB @11Khz, -5dB @ 20Khz
THD+N: <0.005 (< -90dB) @ -10dB below max sensitivity level
Sensitivity: 1.1Vrms @ line level, 2.5 Vrms @ mic Level
Gain: 11dB @ line level, -28dB @ mic level. ±1.5dB.



Is preamp OK, is it balanced output?
Voltage supply range is from 9-24V.

7
Preamps and Effects / Peavey 6505+ FET EMULATION
« on: June 26, 2008, 04:29:30 AM »
Can guys on the forum help me with creating of this super hi-gain preamp*(pedal)?I have the schematic of the 6505+, and i wanted to share it with you.I have drawn the LEAD channel, and i need some help. How to bias FET's on this circuit (what are the values of the trim pots)?Must I change values of the source(cathode) resistors?Are the resonance and presence controls ok, since i bypassed phase inverter?I will draw the PCB right away when you guys give me some answers.I will appreciate any help.
Here is the original schematic of the 6505+:
http://img505.imageshack.us/my.php?image=6505schemvc0.jpg
Here is my schematic:
http://img262.imageshack.us/my.php?image=6505vu0.jpg

8
Schematics and Layouts / The best JCM800 SS emulation
« on: March 02, 2008, 01:14:16 PM »
Does anybody has GV2(Guv'nor Plus) schematic?If you do,please send it to me, i am willing to make it as the preamp,and as the poweramp i will use mg100dfx power amp(i have the schematic,it's pretty simple).I think that is going to be closest JCM800 SS emulation.
If anybody is interested in making this project,please let me know?

Thanx

9
The Newcomer's Forum / TDA7294?Help, please
« on: January 13, 2008, 07:21:47 PM »
Is it possible to run a TDA7294 as poweramp,and as a preamp Randall RG100ES preamp?
TDA7294 is a 100W(hifi)poweramp,can i use it as a guitar poweramp?
Here is the sch. of TDA7294:
http://bp2.blogger.com/_noz8x6lNwLk/R3tEkXwg_WI/AAAAAAAAASM/FK6KJDXfPIw/s1600-h/01.jpg

Thanx

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