The simplistic Salas low voltage shunt regulator

[Salas]

I guess a resistor of 15k with a 1.1uF capacitor would do. That gives a -3dB point at 10Hz. I use the reg to drive opamps that have excellent PSSR below 100Hz, so a higher corner frequency does not matter. I guess I could even reduce it to 4.7k if I use 1.1u || 1.1u and raise the -3dB point to 15Hz. This would reduce the impedance and increase the current.

What is the ideal current through there?

I would take that down to 1Hz any day. Op amps proved susceptible to change from batteries to shunt V1 in Marinos words that used it on his 627 pre. Especially in bass dynamics he said. So just make it. Play hands on in your system. All else is waste of time IMHO.

 

[HiFiNutNut]

Salas,

So you are a good engineer, not a good witch.

Seriously, thank you for pointing those out to me. As I said before, I follow the engineers and just do what they tell me.

I will build it first but may compare it to the film cap tweak. In that case, what resistor value should be used between the g and s?

I don't have Paypal to pay Spensor so I ordered the parts from Futurlec yesterday. I hope the parts will arrive within 10 days (from Thailand) and the parts are geniune.

Regards,
Bill

P.S. Sorry I had not read your later post when I typed and posted this.

 

[jkeny]

Salas,

So you are a good engineer, not a good witch.

Seriously, thank you for pointing those out to me. As I said before, I follow the engineers and just do what they tell me.

I will build it first but may compare it to the film cap tweak. In that case, what resistor value should be used between the g and s?

I don't have Paypal to pay Spensor so I ordered the parts from Futurlec yesterday. I hope the parts will arrive within 10 days (from Thailand) and the parts are geniune.

Regards,
Bill

Bill,
I ordered 2SK170GRs from Futurlec (for another project) & when I sat down to measure them for this shunt reg, I found them all over the place (see my post some pages back) which makes me wonder if they are fakes. I'm going to try the BL range ones in a V1 build to prove them. I emailed them about this a number of times looking for a replacement of the 40 devices I bought & finally they responded saying they would send me 40 2SK1058s. I don't know if this is a mistake or an offer to compensate but I agreed

 

[Salas]

300R should get you down to 1mA, better use a 1k trimmer, every njfet needs a little different and you can go even lower with such a trimmer, upping your main ref resistor so you can accomodate lower corner for small cap at hand. Use a phoenix connector for the Vref so you can experiment freely with it as a subsystem. I.e. Leds, your thing, TL431, whatever. As in Jameshill board.

I am not an engineer, I am a diyer. I only manipulate some simple circuits, mostly based on well known subsystems. More, its over my head.

Salas,

So you are a good engineer, not a good witch.

I will build it first but may compare it to the film cap tweak. In that case, what resistor value should be used between the g and s?

.

 

[HiFiNutNut]

Bill,
I ordered 2SK170GRs from Futurlec (for another project) & when I sat down to measure them for this shunt reg, I found them all over the place (see my post some pages back) which makes me wonder if they are fakes. I'm going to try the BL range ones in a V1 build to prove them. I emailed them about this a number of times looking for a replacement of the 40 devices I bought & finally they responded saying they would send me 40 2SK1058s. I don't know if this is a mistake or an offer to compensate but I agreed

jkeny, thanks for your note.


Does anyone in OZ have some spare 2sk170?

Are there any readily available parts that can be a sustitute?

If all failed, I will just registor with Paypal and get it from Spensor.

 

[jkeny]

jkeny, thanks for your note.


Does anyone in OZ have some spare 2sk170?

Are there any readily available parts that can be a sustitute?

If all failed, I will just registor with Paypal and get it from Spensor.

Hey Bill,
My Futurlec SK170s may be good but just not graded well - I only know when I build the V1 shortly - so you may not need another source!

 

[Salas]

Does not matter much in the regs. Just find 2 0.1-0.3mA near ones for under the Vref, and about 1mA different around.

 

[jkeny]

Does not matter much in the regs. Just find 2 0.1-0.3mA near ones for under the Vref, and about 1mA different around.

Sorry, I don't understand - do you mean that Q5 & Q6 in the attached schematic is OK if with 0.1 to 0.3mA of each other? mA range doesn't matter?

 

[Salas]

As long as they are between 6-10mA ie BL it will work fine. 0.1-0.3mA I care for same position jfets in symmetric regs. 1mA between Q5 and Q6 is fine. They are on other positions. Also 1mA is fine for the symmetric position of the led version njfet under the 3 leds to the left.

 

[HiFiNutNut]

Salas,

Does it mean I don't need to measure them before use and randomly pick up any to put in the board? or there are some that may be out of the desired range?


Jkeny,

Thanks for you info again. To be on the safe side, I cancelled my order. Futurlec seems to be reasonable to deal with and they acted on my email promptly for cancellation without any hassles.

I have just registered with Paypal and will need to wait for up to 3 days because I can use it. I will then buy them from Spensor. It is bad that I need to wait for another 10+ days perhaps. I would like to get it now and build and listen to it tomorrow.

Regards,
Bill

 

[Salas]

We said they must fall between 6-10mA as a pool to pick from. Each symmetric position must fall 0.1-0.3mA close. Between positions, 1mA is OK. In other words, you can peak 7 & 7.3 for those under the Vrefs in a symmetric, 8 and 8.3 for those over the driver bjt or vice versa and no problem. I believe you undertsand that you must note them after Idss measurement so to know what you have to pick.

 

[HiFiNutNut]

Cheers!

 

[jkeny]

Bill, I'd imagine that it is a good idea to measure them before use and pick close ones as they come in a range!

 

[RCruz]

It looks worst then it is in reality.... Here you have a practical method:

First you measure each jfet and note it´s value and a ref number (123.....)

Then you input both values as columns in a excel sheet. (Remenber to name the first cell for Nº and the second one for Idss and input the values below).


Then you sort by the idss column and choose the pairs by their numbers.

Quite effective.

When you start building, You must measure the chosen ones again so you are sure there are no mistakes...

Works like a breeze

Ricardo

 

[jkeny]

I just write the idss beside each jfet - it's easy to scan 50 or so for close matches - don't need a computer. I can see excel being useful for large nos but I don't have the time for all that measuring

 

[HiFiNutNut]

Salas and Iko,

I have just sent an email to Spencer. Cross fingers for getting the 2SK170BL.

I am working on my Farnell order item list. Please check if the versions are suitable:

For v1:

IRFP240 => found IRFP240PBF
IRFP9240 => found IRFP924P0BF

For v2:

IRFBC40LC => No IRFBC40LC available, only IRFBC40APBF
2n5088 => Found 2n5088, 2n5088G, 2n5088BU
mpsh81 => Found mpsh81"D27Z

Let me know if they are NOT OK.

I read that MPSH81 (PNP) is to replace BC560C (PNP) in v1. This is for the neg rail. What is to replace BC550C (NPN) for the pos rail?

I will be building both. Iko, thanks for posting those schematics and simulating v2 for me. They are for 15.7V rails. I am using SOIC opa627s on browndogs and even the top one runs a bit hot on +/-15VDC and I can imagine the one soldered underneath the browndog may get less heat dissipation. So for +/-15VDC rails I prefer to go under instead of higher. I think I can use exactly the same schematics and component values you posted, only with the 1n4744 replaced with 1n4743 (v1), and 1n4737 replaced with 1n4736, to get about 13.6V instead of 15.7V, to reduce the heat on the opa627 for some peace of mind. Have you got an existing PCB design for v2? If not, I could use ExpressBCP to draw one in reference to the PCB layout of the existing v1.

Thanks,
Bill

 

[Melon Head]

PBF = Lead Free = no problem

 

[Salas]

Salas and Iko,

I have just sent an email to Spencer. Cross fingers for getting the 2SK170BL.

I am working on my Farnell order item list. Please check if the versions are suitable:

For v1:

IRFP240 => found IRFP240PBF
IRFP9240 => found IRFP924P0BF


Let me know if they are NOT OK.

Thanks,
Bill

-Spencer never failed anyone. No worries.

-They are OK. (IRFP9240PBF - IRFP240PBF).

 

[iko]

Bill, wait, I got some sources for some of those parts that you won't believe. I'll send you pm. Don't worry about Spencer, many of us got hundreds of 2sk100s from him, myself included.

 

[HiFiNutNut]

Thanks guys.

Iko, you can send me message via email as in my profile.

Regards,
Bill