RE noise in oscllators- I just explored the issue with my Shibasoku. 1 KHz can be at the 1 X 10 or 10 X 1 (two extremes of the resistance arms) and I tried 5 X 1 a midpoint (sort of). I expected the noise to be highest at the highest resistance (1 X10) but it was at the midpoint. Both ends were exactly the same (-114) and at the midpoint about 3 dB higher (-111). So much for my simplistic inner model for how it works.
Low power though they may be, the top flite bjt opamps with/without a composite output stage are awfully hard to beat in their voltage range. And a whole lot more compact on a PCB. At least from my perspective, you have to have a solid reason to go discrete in this application. Or some form of a composite discrete/ic solution.
There are aspects to an IC that are very difficult to do with discretes, like matching and multiple emmiter transistors. However the IC does have process limits. And I would like some of opamp A and some of opamp B which can't really happen. But a "hybrid" using a discrete front end with cascoded JFETs and a buffered output may get the best of everything.
Maybe someone can point out some opamps with useful internal connections brought out other than the 5534.
In the case of the Shibasoku amp circuit it doesn't save a lot except real estate. They liked their circuit enough they used it in a number of places. That circuit also needs +/- 25V so not easily dropped in.
Maybe someone can point out some opamps with useful internal connections brought out other than the 5534.
In the case of the Shibasoku amp circuit it doesn't save a lot except real estate. They liked their circuit enough they used it in a number of places. That circuit also needs +/- 25V so not easily dropped in.
A hint for Dave 😉: Compare the OPA211 and OPA1611 datasheets and check if someone has measurement data of the former.
Samuel
Mr. Wurcer, is it true that a hypothetical 1nV/rtHz jfet input opamp won't fit in a regular 8 lead SOIC case?
Just for a frame of reference as to what is readily available in analog generators -- my lightly tweeked Krone-Hite 4402B; Thru its attenuator/level control and output amp:
-138 and -136dBv 2H and 3H into 100K at 4KHz. Typical performance. Using the ShibaSoku 725D and QA401 on the analyzer monitor output.
I would expect better designs to be at least >10dB better.... which I know Davada's is. See #4810.
When can we get design/pcb?? 🙂
THx-RNMarsh
-138 and -136dBv 2H and 3H into 100K at 4KHz. Typical performance. Using the ShibaSoku 725D and QA401 on the analyzer monitor output.
I would expect better designs to be at least >10dB better.... which I know Davada's is. See #4810.
When can we get design/pcb?? 🙂
THx-RNMarsh
Last edited:
Maybe not as easy as it seems to get down to SOTA performance..... I just read Bruce Hofer uses composite in his latest and greatest... AND, he said it was the hardest thing he ever did in 46 years at this.
??
-RNM
Last edited:
The data at #4866 was only after 5 minutes of being turned on. But after about an hour I rechecked and the 3H only had risen quit a bit; more than 10dB !!
Apparenty I last adjusted it with top off. With top off the 3H dropped. So I will have to ventilate this a little and or put some holes where I can drop a tunig tool thru for adjusting trim pots I added.
Which all brings up.... how stable is harmonic distortion, temperature-wise, with your new designs?
With retune -144dBv and -138dBV for 2H and 3H. [zero = -100dB]
THx-RNMarsh
Apparenty I last adjusted it with top off. With top off the 3H dropped. So I will have to ventilate this a little and or put some holes where I can drop a tunig tool thru for adjusting trim pots I added.
Which all brings up.... how stable is harmonic distortion, temperature-wise, with your new designs?
With retune -144dBv and -138dBV for 2H and 3H. [zero = -100dB]
THx-RNMarsh
Last edited:
Depends, it could fit in one of the more recent processes but the largest possible die would make for an expensive part and a very narrow market.
I'm doing some pruning right now. Reducing the controller cost without performance loss.
Might add in some extra features. Like conversion to a high Q tuned band pass filter for sound card source filtering. Simple things with not much added cost.
Also, I could be wrong but I thought someone here from TI said that the OPA211/1611, the OPA827, and OPA1641/2 all had some tweaks and perform better now than when originally released.
Everything has to be automatic doesn't it. I am thinking about that but a manual one can be done right now. It's just matter of opening the control loop, adding some damping and bit of input conditioning. If you want the auto you'll have to wait for revision x.
The problem is control without raising the distortion.
I am happy with manual..... Its the low distortion I want with variable freq. The rest are just ideas for you to play with.
THx- Richard
THx- Richard
Seems unusual as mask iterations are rather expensive; also many of the distortion effects I see are of rather fundamental nature (e.g. related to available power and basic topology chosen) so not easily improved without drastic changes. But of course almost everything happens in this world; if you can link to a post giving details let us know!
Samuel
Thanks, this is obscure unless you already know to check, it would be useful to have some indication when identical parts are known by different names.
Probably help a lot of people who wonder why common amps such as the LM4562 and LME49710 are absent from your list.
If the OPA1611 really is identical to the OPA211 then it is eliminated as a serious contender.
Best wishes
David
http://www.diyaudio.com/forums/anal...pedance-jfet-input-op-amps-4.html#post4129606
This is the closest I remember to process improvement wrt 164X and 827 (among others).