The simplistic Salas low voltage shunt regulator

[canvas]

Well, I only have 12V right now. Is it ok for 5V vout?

Thank you, Salas.

 

[Salas]

Will still work.

 

[HiFiNutNut]

Salas and friends,

My greeting first as I have not been here for a long time.

Sorry for this out of topic post. Earlier in this thread we discussed the DACT-type attenuator Salas recommended. I bought a couple of them (20k) and found them sound nice. Because dust got in it, it started having some cracking sound when changing volumes. It gets worse now so 20 minutes ago I replaced it with a genuine 50k ALPS pot.

Big shock!!! 😡 The sound was obviously different!!! to the worse.

I could never imagine that an ALPS pot has its own sound and I don't think that a pot needs run-in. 😕 I thought that only capacitors have their own sound.

Regards,
Bill

 

[Salas]

Hello Bill. Nice to hear from you.The stepped ones have precise matching is one sure thing, when the conductive track ones differ enough between channels. If you could have them non exposed they could be a good deal those cheapos. There must be a way to wrap something around them or find a cap for those so to not gather dust? Don't know, an old film box or something that you could make a cut out for the wires.

 

[HiFiNutNut]

They sound more transparent to me ears. I think I will email the seller and see if he has got any enclosed ones. At the same time, I guess I will try using spirit and then dust sprays and see if I can clean out the dust.

 

[Salas]

No box cover absolutely a must? Consider some form of makeshift little cover for them after you will clean em.

P.S. Was it Aussie amps kits you were basing your power channels if I remember well?

 

[HiFiNutNut]

Line level preamp / XO with 3 shuntregs - children of the Salas reg - the devils we love for hot sound so hot that if I put the chassis cover on they would catch fire. Will migrate them into power amp chassis one day and cover it up.

 

[canvas]

Hello Salas,

Regarding Q3 & Q8, can I use 2N5458 instead? My supplier only has them and I bought 4 today. Three are measured around 6.5ma~6.9ma Idss, exception one has only 4.8ma.

 

[Salas]

Use for Q3 the 6.5-6.9mA ones. For Q8 use a 2SK170 that has lower pinch off if you got a spare.

 

[canvas]

Use for Q3 the 6.5-6.9mA ones. For Q8 use a 2SK170 that has lower pinch off if you got a spare.

Got it, thanks.

 

[HiFiNutNut]

I bathed the DACT Type 21 Stepped Attenuator in methylated spirits and tuned the pot for a dozen times. When dried, I used some RS Component (expensive) contact cleaner to spray it around and used electrical tape to wrap around the opening area. Soldered it back to the preamp. I turned the pot and didn't hear the cracking sound anymore. So the cleaning was successful. And now the good sound is back!🙂

I then got an email from the ebay seller that "If there are dust inside or bad contact, I always use "3M Contact Cleaner" to clean it. Not recommended to use spirit or alcohol for electrical contacts. Some buyers said that they use "Hot Shrink Tube" to wrap this Attenuator to avoid dust.". It was too late but never mind.

A big lesson has been learned. Forget about the expensive genuine ALPS pot, despite having measured it and found reasonably tight tolerance between channels. Quite an obvious difference in sound quality. These ebay DACT type 21 pots are highly recommended. Thanks for Salas recommendation.

Regards,
Bill

 

[Salas]

Thanks for letting us know. Happy listening.

 

[canvas]

hello Salas,


Can I put sense and force cable together into a shielded twisted cable? Please look at the schema, thanks.

An externally hosted image should be here but it was not working when we last tested it.

 

[AndrewT]

post3733
is this a new schematic, but based on an earlier release?

 

[Salas]

hello Salas,


Can I put sense and force cable together into a shielded twisted cable? Please look at the schema, thanks.

Surely, coax or twisted is recommended. Shield for sense. But use a faster CCS PMOS. Like IRF9610,9620,9510,9520.

 

[Salas]

post3733
is this a new schematic, but based on an earlier release?

This is the V1.2R for lower voltages that can utilize a Jfet cascode since the cascode Jfet's Vmax suffices. It has been posted along with the other higher Vo BJT cascode CCS tail 1.2Rs back then.

 

[canvas]

Surely, coax or twisted is recommended. Shield for sense. But use a faster CCS PMOS. Like IRF9610,9620,9510,9520.

Hi Salas,
Maybe I didn't say it clearly. I mean one shielded twisted-pair cable will be used for sense+ & force+, and so does sense- & force-. By doing that, the force line will be shielded, too. The reason for this is that I'd like both sense and force line being packed together, having same length and being shielded. Will this have any negative effect?

 

[Salas]

Shielding the sense + line with shield to sense 0 would be preferable since it does the voltage nodes. I don't expect it to give you any real trouble however you prefer it, but a force twisted pair and a coax sense wrapped around, would make one defined terminal as easily. You need no thick gauge. I have even used CAT5 twisted pairs and thin coax. The drop on the force lines will be taken into account is the deal.

 

[canvas]

hi Salas,

I got your point. It is better to twist the force lines. Now my problem will be the thin coax. Hard to find here. Mostly thick TV cables...

Thank you again.

 

[Salas]

Avoid TV cables. Just use well tight thin enough to be manageable twisted pairs for sense and force lines per function and then entwine them. That will keep a tight loop area at least.