Ricardus

I guess that you might say I was scared away.  Some day I will tell you why. Anyway, I have built three of the circuits and they have surprised the people who heard the difference in gain level and low noise. I have added a blue LED connected via two 1 meg resistors-one each to pin two and pin three of the male XLR. It must be a blue or otherwise clear bright LED. I don't know why though.  Len.

Can you post the latest schematic?
Audio mastering for hire..


Can you post the latest schematic?

I may of course be wrong here but, if  'Computerlen' and 'Lennie' are one and the same,  the schematic is in the 3rd post.
This is the schematic that both seemed to be talking about anyway so, one way or t'other

Edit:  I've attached it again here just in case.   Note -  this is *not* my schematic or design. 
« Last Edit: February 02, 2020, 08:00:10 PM by Winston O'Boogie »

Ricardus

Didn't he say he made some changes? Isn't that what the ruckus was about?
Audio mastering for hire..

Didn't he say he made some changes? Isn't that what the ruckus was about?

 I'm not exactly sure what the crux of the ruckus was. 
I got the impression a lot of it was over the use of phase vs polarity, and there was also the suggestion the circuit had low end loss but then Lennie said he had no problem.   I  incorrectly wrote Flack instead of Flak and had also earlier expressed concern with the low gate-source voltage of the cascoding K170's  and suggested using other devices there.    There may have been other stuff.

As a solution, maybe Abbey has a spare pcb of the circuit he did that you could snag?



 





Ricardus


As a solution, maybe Abbey has a spare pcb of the circuit he did that you could snag?

 I already have four of them.  :)  They came last week.  The transistors just arrived in the mail (the dual FETs) and the mousers cart for two of Abbey's circuits and some other stuff I'm working on should be arriving any minute.  :)

I was just curious about this one also.
Audio mastering for hire..

I already have four of them.  :)  They came last week.  The transistors just arrived in the mail (the dual FETs) and the mousers cart for two of Abbey's circuits and some other stuff I'm working on should be arriving any minute.  :)

I was just curious about this one also.

That's great.  Was it easy enough in the U.S. to get the LSK389's?  Expensive? 
I don't know the little important details of the schematic/design that he decided on but, from what he said on here, it should do a really nice job. 
Let us know dude  :) 

Ricardus

That's great.  Was it easy enough in the U.S. to get the LSK389's?  Expensive? 
I don't know the little important details of the schematic/design that he decided on but, from what he said on here, it should do a really nice job. 
Let us know dude  :)

 I got the LSK389's here:

https://store.nacsemi.com/products/detail?part=LSK389A-TO-71

$8.66 each but worth it. Easy to get. (edit: Apparently their pricing fluctuates based on I don't know what, because when I bought these they were $8.66, but when I checked again they were over $10, now they're back to 8.66)
 
I soldered up one of the boards but didn't finish the whole thing because I woke up with a stiff neck and being hunched over my bench wasn't helping, but I wanted to do something. Building cheers me up. I am also waiting for an m2.5 tap to come for the metalwork.
« Last Edit: February 23, 2020, 02:53:14 PM by Ricardus »
Audio mastering for hire..

abbey road d enfer

I got mine there
https://www.ebay.com/itm/5-pcs-LSK389-Ultra-Low-Noise-Monolithic-Dual-N-Channel-J-FET-/283491526786
It's the cheapest I found, but they don't ship internatinally, only to the US.
I had them sent to a friend there, but the cost of posting back to France doubled the price. Ridiculous, innit?

Actually, this seems an interesting alternative
http://fr.aliexpress.com/item/32912426650.html?spm=a2g0o.productlist.0.0.253d5eddJkzoxe&algo_pvid=fd77ee0d-e50c-4c6b-867a-904b18af09c6&algo_expid=fd77ee0d-e50c-4c6b-867a-904b18af09c6-13&btsid=7730ca6b-f5e7-4b1d-97c3-68a22620b906&ws_ab_test=searchweb0_0,searchweb201602_1,searchweb201603_53

or maybe the SMD version.
Nag is that I would need to re-lay the board...
« Last Edit: February 06, 2020, 12:33:39 PM by abbey road d enfer »
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Ricardus

I've gotten stung by the fake semi thing on ebay before, Particularly when I was looking for 2n3819s for my u87 builds. I did get some LM394's there for my SSL preamp builds, but I guess I found a reputable vendor.

I'll b buying more from the link I provided above because I know exactly what I am getting. It's pricey but hey, you only live once.
Audio mastering for hire..

Very cool, thanks for the pic and links Ricardus and Abbey  :)

P.S.  hopefully your stiff neck is better by now.



Ricardus

I'd much rather build my own. More fun.
Audio mastering for hire..

Lennie

Re: Low output ribbon/ dynamic microphone phantom-powered circuit
« Reply #72 on: February 17, 2020, 05:33:03 PM »
What you mean is "Reverse Polarity" as reversing phase does not exist.

And yes reversing the polarity by swapping Pin 2 and 3 of the XLR connector should not impact the sound.

I'm pretty sure you are doing something wrong, like for example  swapping Pin 1 and 2 (instead of Pin2 and 3)

You are right but  after being wrong for most of my life it certainly is tough to correct myself. Len.

Lennie


Lennie

For weeks I have  been searching for  a wiring diagram so that I could build a circuit powered from the phantom power from my mixer but none of the 48 volts gets to the dynamic or ribbon mic.  I have come up with the perfect 4-transistor circuit.  The low level from my Shure SM7 is boosted by more than 20db which is enough so that there is no need to increase the gain control of my mixer and therefore not increase the noise level.  It uses 4 fet transistors and 3 resistors and 2 caps.  Really easy to build.

I am puzzled by something. When I build the circuit using transistors, there's no problem. When I build using the LSK devices the gain is noticeably lower. I figured that there should be no level differences. Any suggestions?

abbey road d enfer

I am puzzled by something. When I build the circuit using transistors, there's no problem. When I build using the LSK devices the gain is noticeably lower. I figured that there should be no level differences. Any suggestions?
What do you mean by "transistors"? The LSK device is a pair of transistors in a single package. What are you comparing it to? FET's, as well as bipolar transistors, have wide variations between types, some have more gain than others. Even within the same type there are large variations.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Lennie

What do you mean by "transistors"? The LSK device is a pair of transistors in a single package. What are you comparing it to? FET's, as well as bipolar transistors, have wide variations between types, some have more gain than others. Even within the same type there are large variations.

Silly me. I assumed that you had followed the wiring diagram that I had put up. I should have stated that the transistor numbers I use are -2SK170 fets. Two are in the LSK389 package as you know. I am just saying that, twice when building the preamp circuits I found the LSK packaged transistors to be quite noticeably lower in gain but whenever I built the circuit using only the transistors there is plenty of gain. I wonder if any one else might notice this as well.

abbey road d enfer

Silly me. I assumed that you had followed the wiring diagram that I had put up. I should have stated that the transistor numbers I use are -2SK170 fets. Two are in the LSK389 package as you know. I am just saying that, twice when building the preamp circuits I found the LSK packaged transistors to be quite noticeably lower in gain but whenever I built the circuit using only the transistors there is plenty of gain. I wonder if any one else might notice this as well.
OK. I have experimented with 2SK170's, while I was waiting for the LSK389's to arrive.
First experiment I used 4 of them in the parallel configuration originally planned for the 389's. The circuit just didn't work. The FET's acted like a short. I then experimented with just two of them; the circuit works and the gain is quite high. I haven't experimented with the 389's in  the circuit you're using. I didn't want to put at risk the 389's (they're rated at 40V max).
It looks like the commonly available 170's have a higher gain (Gm) than the 389. They both come in different gain categories, A, B and C. I think the "A" type is the most adequate in this application because the "B" and "C" type require more current  than what phantom can supply.
In addition the 2SK170 exists in a version that's intended for switching applications; I believe that's the most common type found on Ebay or Alibaba.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Lennie

OK. I have experimented with 2SK170's, while I was waiting for the LSK389's to arrive.
First experiment I used 4 of them in the parallel configuration originally planned for the 389's. The circuit just didn't work. The FET's acted like a short. I then experimented with just two of them; the circuit works and the gain is quite high. I haven't experimented with the 389's in  the circuit you're using. I didn't want to put at risk the 389's (they're rated at 40V max).
It looks like the commonly available 170's have a higher gain (Gm) than the 389. They both come in different gain categories, A, B and C. I think the "A" type is the most adequate in this application because the "B" and "C" type require more current  than what phantom can supply.
In addition the 2SK170 exists in a version that's intended for switching applications; I believe that's the most common type found on Ebay or Alibaba.


The circuit that you directed me to below is the one I had put up here. You mention that you used just two of the FETS in a circuit and they worked well. Is there a diagram of just two FETS as a preamp? Len.


Thank you so much for the information.  I didn't know about the different gain factors of the 2SK170's. Would you mind showing me the wiring for using only two of the FETS?  Len.
« Last Edit: February 18, 2020, 08:07:33 PM by Lennie »

abbey road d enfer


Thank you so much for the information.  I didn't know about the different gain factors of the 2SK170's. Would you mind showing me the wiring for using only two of the FETS?  Len.
Do you mean with the circuit there?
https://groupdiy.com/index.php?topic=74016.msg938568#msg938568
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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