Paradise Builders

[Joachim Gerhard]

http://www.ti.com/lit/ds/symlink/opa627.pdf

 

[Joachim Gerhard]

This is a modern, less expensive alternative but it comes only in SMD so you have to make an adaptor :
http://www.ti.com/lit/ds/symlink/opa827.pdf

 

[shoom]

Algar, great work.
shoom, the 2mV offset you get now is more or less the offset of the Opamp used as servo.
When you want even better you need to use something like an OPA627 that is specced down to 0.1mV.

Hi Joachim

2mv is very good by any standards so I feel no great urge to go further but as it happens I have a few 627 in my parts box so may give that a try.

But

I’m really pleased with the low level offset I now have.

all good so far

 

[Joachim Gerhard]

Fine, i wish you a good listen.

 

[Algar_emi]

Installed the OPA627 and thermal coupling bracket on input gain transistors. I'll report on the result after stabilization

 

[Joachim Gerhard]

Very good.

 

[Salas]

Installed the OPA627 and thermal coupling bracket on input gain transistors. I'll report on the result after stabilization

Are those black resistors Welwyn, or Holco?

 

[RollE2k]

Are those black resistors Welwyn, or Holco?

Looks like IRC / TT electronics to my eyes, but maybe Algar can confirm

 

[Algar_emi]

These resistors are IRC and yes they seems to be Welwyn so maybe Salas you're right. Here the spectrum of the output, using my CLIO system. Input 1Khz, adjusted for 0dBV at the output.

Offset is not lower than 10mv, usually around a few mv. There is really an improvement using the OPA627 for the servo. I removed the output coupling caps

 

[Salas]

Looks like IRC / TT electronics to my eyes, but maybe Algar can confirm

TT is Welwyn's new name also I think.

 

[Salas]

These resistors are IRC and yes they seems to be Welwyn so maybe Salas you're right. Here the spectrum of the output, using my CLIO system. Input 1Khz, adjusted for 0dBV at the output.

Offset is not lower than 10mv, usually around a few mv. There is really an improvement using the OPA627 for the servo. I removed the output coupling caps

Good resistors at 25ppm or 15ppm. Nothing is like Vishay VAR, but much less costly too.

The noise floor looks pumped up for a Paradise I think? Experts will tell.

 

[Joachim Gerhard]

I can see hum, multiples of 50 or 60Hz.

 

[FdW]

Are those black resistors Welwyn, or Holco?

Or my 'beloved' IRC's (maybe someone took a hint as I mentioned these before). I think a very good resistor at a reasonable price. At Mouser they are now listed as IRC/TT.

http://nl.mouser.com/Passive-Compon...P=1yzbpodZ1z0z819Z1z0vpm5&Keyword=irc&FS=True

 

[Salas]

Yes we talk the same RC type parts in the end, its the one and same group of trademark names it shows.

 

[Algar_emi]

The hum is caused by my test setup. I can never remove it when I test phono preamp. If I listen to the Paradise there is no hum, by a low hiss like a tube preamp. The 60Hz and 120Hz noise spikes can probably be discarded from the graph.

 

[Salas]

Do you use Lpad attenuator for the generator's signal? If not, use 1000R series and 10R shunt 1:100. It will slice generator harmonic noise. 100mV setting will give 1mV from 10 Ohm source resistance.

 

[AVWERK]

Very nice build SB!
Your one of the top builders and most dedicated on diyaudio IMO
Great follow through and finish!
Hope the sound lives up to your expectations

Regards
David

 

[Algar_emi]

For the sake of comparaison, here my JLTi preamp, very silent.

 

[Algar_emi]

And the Sutherland PHd, battery supply. Shouldn't have any supply spurious but it is still there I'll try the 100:1 shunt and report back.

 

[Salas]

You should find a way through shielded Lpads or elimination of other causes in your measurement loop so to tame the incoming harmonic noise in order to can see valuable information on your FFTs.