Search found 5449 matches

by mediatechnology
Mon Nov 19, 2012 3:27 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Re: A Direct-Coupled Input-Capacitorless Active Mic Preamp

ricardo - Your 48V supply looks very clean. I noticed that you'd built in short-circuit protection since it appears to enter a cable. I'm thinking about feeding the preamp regulated 66V from the PSU and then putting the 48V ripple eater on the preamp board. Been mulling whether I should provide 48V ...
by mediatechnology
Fri Nov 16, 2012 4:34 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Re: A Direct-Coupled Input-Capacitorless Active Mic Preamp

I took a break from tweaking the power supply I built because I wanted to use it to test a new "recovery" amplifier for the 1510 output. I came up with this: https://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=557 https://proaudiodesignforum.com/images/jpg/Line_Input_AC-C...
by mediatechnology
Fri Nov 16, 2012 4:22 pm
Forum: Pro Audio Design
Topic: A Simple AC-Coupled Balanced Line Reciever
Replies: 0
Views: 15058

A Simple AC-Coupled Balanced Line Reciever

I needed an AC-coupled, high impedance balanced line receiver with exceptional low frequency common mode rejection. I wanted to use a bipolar input op amp with low-value film capacitors for a "non-electrolytic" approach. This requires a high impedance input to reduce capacitor matching re...
by mediatechnology
Thu Nov 15, 2012 8:09 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Re: A Direct-Coupled Input-Capacitorless Active Mic Preamp

Very cool! Looks like D18/D19/C53/C64 do the same (Self) deal by bootstrapping a halfwave doubler perched on top of the +Vbulk across C65. the heater was probably my most important contribution to the Soundfield project Funny. We were always told to the best way to dry the spit out of a microphone c...
by mediatechnology
Thu Nov 15, 2012 12:46 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Re: A Direct-Coupled Input-Capacitorless Active Mic Preamp

$4k preamp... I have long wondered why we couldn't just shunt across electrolytic phantom caps for non-phantom mic operation. "Why have input caps at all?" has been my question since 2007. I would warn anyone considering shunting an input coupling capacitor with a relay the huge discharge...
by mediatechnology
Wed Nov 14, 2012 7:42 am
Forum: Document
Topic: Feld Electronics Vintage Soldering Supplies
Replies: 0
Views: 7859

Feld Electronics Vintage Soldering Supplies

I needed a replacement sponge and tray and stumbled upon Feld Electronics eBay store. I was so impressed with the extra sponges he threw in I gave him a very good review and visited his store. This guy has a lot of vintage soldering tips for Hexacan and Ungar. http://stores.ebay.com/feldelectronicsa...
by mediatechnology
Tue Nov 13, 2012 1:51 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Re: A Direct-Coupled Input-Capacitorless Active Mic Preamp

Thanks John. If it were for a console I'd go for a second winding. C1 & C2 get big fast once you scale the current up. But, the second winding would only need to be 36-40V since it's "perched" on top of the V+ bulk supply. I'm thinking for two channels I'd want to use 470uF/100V for C1...
by mediatechnology
Mon Nov 12, 2012 2:53 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Bootstrapped HV Supply for DC-Coupled Preamp

I was able to test the bootstrapped power supply and it works like a champ. This is the rectifier that derives +85VDC (unregulated) for the floating supply. https://proaudiodesignforum.com/images/jpg/DC_Preamp_Power_Supply_Simplified_BW.JPG DC-Coupled Preamp Power Supply Rectifiers I need about 20 ...
by mediatechnology
Sun Nov 11, 2012 12:18 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Re: A Direct-Coupled Input-Capacitorless Active Mic Preamp

As it turns out the fullwave bootstrapped voltage doubler (tripler) can be made with a second bridge. The entire bulk supply are the five caps and two bridges providing +/-28V and ~+85V. Two caps (100uF/100V) are to float the second bridge. The remaing caps are filters. I'm using a 15VA 36V transfo...
by mediatechnology
Sat Nov 10, 2012 1:12 pm
Forum: Pro Audio Design
Topic: Old: A Direct-Coupled Input-Capacitorless Active Mic Preamp
Replies: 212
Views: 409263

Re: A Direct-Coupled Input-Capacitorless Active Mic Preamp

Well as it is now I get four supply voltages with only five bulk electrolytics and two "bridges" (one bridge and 4X diodes).
The extra cap provides the FW for the tripler and I get better low-line and less ripple current stress from the extra C so I'll take that.