Search found 5447 matches

by mediatechnology
Mon Jan 12, 2009 5:17 am
Forum: Build
Topic: 1510 -- servo, or not ?
Replies: 24
Views: 74389

Re: 1510 -- servo, or not ?

Randy; The T-Bias scheme does allow the use of smaller values because of the higher CM impedance on the right-hand side of the caps. I wouldn't go much lower than 22 uF though which eliminates the use of film caps due to size. On the single-supply preamp non-polarized capacitors are required because...
by mediatechnology
Sun Jan 11, 2009 7:14 pm
Forum: Build
Topic: 1510 -- servo, or not ?
Replies: 24
Views: 74389

Re: 1510 -- servo, or not ?

The drawing looks good Randy. Can the "pin2 to 3"..200pf cap be either a 220 or 180 ?? Yeah either one. I'm reminded of the movie "Mr. Mom" where Mr. Mom is asked "Are you rewiring for 220?" Mr. Mom answers "Yeah 220, 221." As you point out those 1R5 stop resi...
by mediatechnology
Sun Jan 11, 2009 3:02 pm
Forum: Build
Topic: 1510 -- servo, or not ?
Replies: 24
Views: 74389

Re: 1510 -- servo, or not ?

The OP07 (or OP77) trimmed would be inexpensive. That's the option I've considered for the DC preamp. Either that or an LT1012.
by mediatechnology
Sun Jan 11, 2009 8:38 am
Forum: Build
Topic: 1510 -- servo, or not ?
Replies: 24
Views: 74389

Re: 1510 -- servo, or not ?

Thanks for posting here freqband. I've spent a lot of time lately with the 1510/1512. If you're going to be using this for instrumentation my recommendation would be to just use a Cgain and eliminate the output servo. I do recommend a stepped resistor gain control however for precise repeatability. ...
by mediatechnology
Sat Jan 10, 2009 8:07 am
Forum: Pro Audio Design
Topic: OTB Mixer Using Current Summation
Replies: 137
Views: 214226

Re: OTB Mixer Using Current Summation

Nice work John. Very simple using two duals. I think keeping the RC network in there is a good thing.
by mediatechnology
Thu Jan 08, 2009 1:19 pm
Forum: Pro Audio Design
Topic: OTB Mixer Using Current Summation
Replies: 137
Views: 214226

Re: OTB Mixer Using Current Summation

I think we'd need a pan kill of at least 70 dB or more since that's about what a conventional pan pot would produce.
by mediatechnology
Thu Jan 08, 2009 12:14 pm
Forum: Pro Audio Design
Topic: OTB Mixer Using Current Summation
Replies: 137
Views: 214226

Re: OTB Mixer Using Current Summation

The perhaps flaky data sheet I looked at was something like 8-10 nV/rt hz for those opamps. FWIW something like a 5532 driving the CV would very likely be more than adequate sonically and cheap. The 33078/33079 is more like 4.5 nV/rt Hz: http://www.onsemi.com/pub_link/Collateral/MC33078-D.PDF Not t...
by mediatechnology
Thu Jan 08, 2009 11:03 am
Forum: Pro Audio Design
Topic: OTB Mixer Using Current Summation
Replies: 137
Views: 214226

Re: OTB Mixer Using Current Summation

John - After thinking about it I went "oops." Yes the DC performance will only be as good as the op amp.

The MC33178/33078/79 are dirt cheap, low Vos and low noise. I'd blow off the passive pad, large C and just drive Ec with the op amp. Less parts to stuff.
by mediatechnology
Thu Jan 08, 2009 9:53 am
Forum: Pro Audio Design
Topic: OTB Mixer Using Current Summation
Replies: 137
Views: 214226

Re: OTB Mixer Using Current Summation

Using a low noise transistor as an emitter follower I can pad down the opamp noise, and deliver a pretty low output impedance.
OK, I follow you there. But wouldn't this also pad down the output offset allowing "looser" (and higher output impedance) quads like a TL074?

Thanks for this....
by mediatechnology
Tue Jan 06, 2009 3:20 pm
Forum: Pro Audio Design
Topic: OTB Mixer Using Current Summation
Replies: 137
Views: 214226

Re: OTB Mixer Using Current Summation

I dusted off my thinking cap, last night, and I can't figure out why not just add a simple unity inverter to split the CV for symmetrical drive?
That's what I was thinkin' too. Looks like an MC33179/MC33079 quad would seem ideal or two duals.