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Topics - swt

#1
Preamps and Effects / Aion lab series l5
January 13, 2019, 11:19:02 PM
Hi. Just finished this project and i am having problems with r76. Before it, i have audio probe and tested the 4.40 ac volts as per calibration. Right after it, audio is almost lost and ac volts drops down to few millivolts. Any clues?
#2
Amplifier Discussion / paging j m fahey
August 06, 2015, 08:36:39 AM
hey juan. I'm also from argentina but i'll follow the forum rules so i'll speak in english.
Do you have a contact phone or web page or email?.
i build tube amps and fxs, ss amps, etc, but just as a hobby in the quest for good tone. i'm an ee but have dedicated my life to music and martial arts.
the reason for this message is to open your eyes to a new market in argentina. i play jazz and blues, and i think it could be a goal to build a polytone pre with a lm3886 or tda 7293 amp, with fx loop. also a desirable amp could be a fet preamp like the old roland cube with a chipamp, or with irp250 fets. i have lots of friends that can buy that type of amps in a head form, not only from the place i live (neuquen, patagonia), but have friends in bs as, mar del plata, rosario etc, that play jazz and would be really interested in buying a polytone type of amp or aimed sound, at a reasonable price. let me know what you think of this or tell me how to contact you by phone. thanks a lot!!
PS: it could also be nice to have some well built tl 606 or tl 806 cabinets to pair with those amps...
PS2: irp250 would also be nice...i'built a polytone pre with a lm3886 and it sounds good, also built a roland cube pre with tda 7294 and had good results, my friends like them a lot, but i'm not a builder...i do that for myself...and build most of the fet preamps on perfboard...
#3
HI!. although i read past threads, and used the search function, i still have some questions.
I've built the LM3886 power amp from ggg. Changed the 33k feedback res to 22k, the input imp res to 100k and 10uf fb cap to ground to 22uf as in the datasheet.
SO here i go:
do you guys use buffers in front of the power amp?. i think it's useful to use them to adapt the preamp to the power amp. but useful it's not always better.
i've tried a couple of rog circuits, and also the bsiab, and unless i crank the vol, i don't achive gain and volume from the power amp....so: should i use a booster, buffer, or maybe just go up with the feedback resistor to get more gain?
Can i add a couple of diodes ala tube screamer to get soft clipping?. ( maybe through a series resistor to limit them).
Are the single rails preamps enough to excite the power amp?. Because i'm using a bipolar supply of +-25v for the chip.
Thanks a lot for your replies!
will be reporting as i make further advances.
PS: i build tube amps and fxs....so far this is my first transistor amp.
#4
Amplifier Discussion / good mosfet power amp schem??
October 15, 2006, 10:30:46 AM
can anybody suggest a good and simple mosfet power amp for the 20w to 45w range?. i'd like to try one...or find a good use for irf 520 or similar mosfets...thanks a lot!!
PS: maybe a single class A small power amp too...like ne irf 520 or 820 and components...
Thanks a lot!