My pleasure. One of the reasons we took the OPA134 is that the OPA627 is costly.
But i am happy that you got such good results. Yes, matching better then 1% is tough.
I usually do not match better then 10% but i am lazy.
But i am happy that you got such good results. Yes, matching better then 1% is tough.
I usually do not match better then 10% but i am lazy.
Is there any mid-end OPA that is better than 134 and cheaper than 627?
I'm asking because i have also matched to +-0,5hFE to my input stage. And as i will be using the no airgap amorphous core input transformer on the line stage i would perfer to have as low DC voltage on the output as possible.
I'm asking because i have also matched to +-0,5hFE to my input stage. And as i will be using the no airgap amorphous core input transformer on the line stage i would perfer to have as low DC voltage on the output as possible.
There are some like the OPA827 and ADA4627. Problem is that they come in SMD cases and can usually not stand the PSU voltage of the Paradise.
You have to bite the bullet.
You have to bite the bullet.
One last resort is the LF411. It is specced to better then 0,5mV.
I used it successfully several time.http://www.ti.com/lit/ds/symlink/lf411-n.pdf
I used it successfully several time.http://www.ti.com/lit/ds/symlink/lf411-n.pdf
Great, i'll probably add that one to my Mouser order. ~2x 4EUR i can pay, but not 2x >20EUR.
Especially since i don't even know if i may get down to that level, since i have matched with resistors on a experimental breadboard, so it may maybe vary a bit. 🙂
I first had 10x trasistors matched at once, but then i have "re-matched" the ones with one resistor setup, to skip the variation between the resistors, so i think it should be pretty close (+-0,5hFE with that setup).
Especially since i don't even know if i may get down to that level, since i have matched with resistors on a experimental breadboard, so it may maybe vary a bit. 🙂
I first had 10x trasistors matched at once, but then i have "re-matched" the ones with one resistor setup, to skip the variation between the resistors, so i think it should be pretty close (+-0,5hFE with that setup).
Hi,
maybe a nonsense idea, but what about impedance matching the OPAmps inputs to lower the Offset?
The output Offset of a OPAmp consists of two parts, a generic Input Offset and a input impedance related.
The generic Input Offset is specified in the Datasheets. Typically bipolar input OPAmps perform clearly better in this regard. Representatives are OP77/177, OP90 and OP27.
The input impedance related offset is due the input biasing currents of inverting and noninverting inputs generating offset voltages over the connected impedances.
with DC-Servos typically one input is grounded and the other is connected to a high valued resistor of ~100k to 1Meg. Due to the by orders lower bias currents of FETs and JFETs, OPAmps with such input devices will give lower output offset than the bipolar input OPAmps with their lower specced inut offset values.
If one now matches the input impedances by not connecting one input directly to gnd but trough a similar valued -as connected to the second Input- resistor to gnd, one could tune the Output Offset to 0V using cheaper bipolar OPAmps.
Or does this come with a too hard noise penalty?
jauu
Calvin
maybe a nonsense idea, but what about impedance matching the OPAmps inputs to lower the Offset?
The output Offset of a OPAmp consists of two parts, a generic Input Offset and a input impedance related.
The generic Input Offset is specified in the Datasheets. Typically bipolar input OPAmps perform clearly better in this regard. Representatives are OP77/177, OP90 and OP27.
The input impedance related offset is due the input biasing currents of inverting and noninverting inputs generating offset voltages over the connected impedances.
with DC-Servos typically one input is grounded and the other is connected to a high valued resistor of ~100k to 1Meg. Due to the by orders lower bias currents of FETs and JFETs, OPAmps with such input devices will give lower output offset than the bipolar input OPAmps with their lower specced inut offset values.
If one now matches the input impedances by not connecting one input directly to gnd but trough a similar valued -as connected to the second Input- resistor to gnd, one could tune the Output Offset to 0V using cheaper bipolar OPAmps.
Or does this come with a too hard noise penalty?
jauu
Calvin
Last edited:
The LF411 has a balance pin, a lower specced voltage Offset/Drift bipolar input OPAmp could servo it.
Best of both, advantage of input bias/offset current at pA level of a JFET input OPA, plus voltage offset/drift of a bipolar OPA.
(Danny Kaye, who will Inspect the Inspector)
Hi Frans
With my own work I try to keep the following in mind.🙂
‘’more haste less speed’’
I like to make sure that I have predictable results before plugging in just to be kind to the rest of my set up.
I’m not sure if anyone noticed that I went directly to Calvin’s lovely buffer which among other things has the ability to zero out its own offset.
That does not change the amplifier offset but then it’s not adding any DC to the OP.
Sounding just fantastic by the way but now time to play with the cart loading.
I’ll be back with another low level fly by later.
excellent observation. not sure noise would be a problem, as this feeds into the current source and as such the impact is limited in my opinion. but I will let MiiB and JG comment....
Calvin, most servos I see are first order LP, what are your thoughts on 3rd order? The corner frequency could be a tad higher (and speed up the settling on power-up), and the impact at audio frequencies could be lower, especially in the bass.
We have a special case here. The servo in the Paradise has a weak action due to the
" household " design that MiiB did. Also i do not see a reason to reduce the output offset under 1mV. That is certainly not necessary in Audio even when you connect a transformer.
There will always be some minimal drift, no matter what.
I do more worry that some claim here that the Paradise has quite high audible hiss. The samples i build and heard where very quiet.
" household " design that MiiB did. Also i do not see a reason to reduce the output offset under 1mV. That is certainly not necessary in Audio even when you connect a transformer.
There will always be some minimal drift, no matter what.
I do more worry that some claim here that the Paradise has quite high audible hiss. The samples i build and heard where very quiet.
Hi Frans
With my own work I try to keep the following in mind.🙂
‘’more haste less speed’’
I like to make sure that I have predictable results before plugging in just to be kind to the rest of my set up.
I’m not sure if anyone noticed that I went directly to Calvin’s lovely buffer which among other things has the ability to zero out its own offset.
That does not change the amplifier offset but then it’s not adding any DC to the OP.
Sounding just fantastic by the way but now time to play with the cart loading.
I’ll be back with another low level fly by later.
Don't you critique me boy 🙂 I am the one working on this for ages and on my amplifier for 2 ages 🙂 all tiptoeing through the tulips 🙂 but I do get your drift. Now quick get me a listening report! SOON!
Some ware in the mpp-thread (I think) I did write something about this (a long time ago). The general (my general impression) is/was, do balance the input currents, and use an 'output'-filter on the servo (ft about 1/3 (or so) of the servo ft) to remove (if any) possible noise).
The servo I would use 1Meg/1u for an ft of 0.16Hz. Then you will need a series resistance on the output of the servo that U use to drive some input (of the circuit that you are servo-ing). Split this resistor in two and add a capacitor to ground from the center, set the ft to 0.5Hz (or there about).
Your new servo will act like a filter parallel to the input signal and with a ft of 0.5Hz (and a minimum resistance of (one halve of the resistor that was split 🙂 typically larger than 50k (what I would do)).
Slightly OT.
I've been waiting for a month now for Peter to send me out a Pre-reg order. Is there anywhere else to get the raw pcb's I've had enough of waiting for someone who doesn't reply to emails. I could have had the parts over two weeks ago if I had sourced them myself.
Does anyone know anywhere else I can get the pre-reg boards?
I've been waiting for a month now for Peter to send me out a Pre-reg order. Is there anywhere else to get the raw pcb's I've had enough of waiting for someone who doesn't reply to emails. I could have had the parts over two weeks ago if I had sourced them myself.
Does anyone know anywhere else I can get the pre-reg boards?
When you use the calvin buffer,the temp. seems to be a bit om the high side....
Is it beter to use a bigger heastsink?
the one used is the fisher sk482 75
http://www.fischerelektronik.de/fileadmin/fischertemplates/download/Katalog/heatsinks.pdf
page A86.
And what to use.😀
Is it beter to use a bigger heastsink?
the one used is the fisher sk482 75
http://www.fischerelektronik.de/fileadmin/fischertemplates/download/Katalog/heatsinks.pdf
page A86.
And what to use.😀
Other looney suggestion might be to force a cheap JFET input opamp in class A, zero it at stasis temperature with a trimpot.
Why operate a class AB output stage opamp in a class A phono circuit.
(LF opamps handle 2/3d of a W)
Look Ma, opamps from the stone age.
Attachments
Hi Dad I’m back🙂
You win
A few words on what I have at the moment and why I wanted to spend time acclimatising to the new sound.
Up until now I’ve been using Nick Gorham’s tricked up WAD phono stage. (Yes tubes) Audio note SUT input, depletion mode mosfets and battery bias on the first stage. Gas zenner shunted B+. (Thanks Nick)
My turntable
NAS with graphite platter mod, Speed box SE PSU, Ladegaard DIY tone arm (nope not made by me as my metal work is pretty poor) and Lyra Dorian Cart. Not super high end but what I could afford at the time.
I’ve had the WAD stage for years and TBH I’ve struggled to find anything to best it at a price that I can afford to pay.
Up until now I’ve tended to avoid Solid state phono stages because I’ve found that to my ears they can tend to sound a little sterile and lacking in musical cohesion compared to my tube stage.
The build
The build was pretty challenging by any standards but I managed to get through it with help and encouragement. Along with the build guid and superb contributions on this thread.
Luckily enough I had some great advice from Simon (SQ225917) before I started the build which really helped.
Thanks Simon
So after all of the long hours of matching and measuring I dropped the needle on the record with more than a little trepidation given my previous solid state experiences.
Some thoughts on the sound😀
Firstly
Hissss? What hiss?
This has to be one of the quietest phono stages that I’ve ever heard. No hum and a pretty low level of hiss. BTW I have Texas Naked foils as my RL’s which may help keep the noise floor low (or maybe not).
The first thing that becomes pretty obvious is the deep, wide presentation which is vast along with pin point imaging which is quite incredible. The top end is so sweet and lucid but without ever straying into glare or grittiness (so no aspirin needed). The bass is tight, well rounded and soooo deep but at the same time always tuneful.
The listening session was long ending up with a huge stack of played favourites waiting to be returned to the shelf.
I’ve tried to avoid the HIFI mag type listing records that most people have never heard but can I play just one record?
Thanks for the indulgence.
Rodrego y Gabriela which for those who don’t know it is Spanish/Mexican guitar music (kind of). It has a great version of ‘’Stairway to Heaven’’ BTW.
Anyhow the first track ‘’Tamacun’’ is a real scorcher and turns quite a few stages I’ve heard to a blurred mush pretty quickly. (I saw them a few years ago at Glastonbury and they were awesome. I was going to take Dad but he said he felt a little old for such things).my present phono does a nice job of portraying one guitarist sitting on the others lap but not so the paradise which clearly presented two guitarists sitting comfortably apart. It also did a super job of portraying the interplay between musicians with all of the fingers on frets that make the performance more real and present.
Every strum, pick and flick perfectly rendered and every thump on the guitar body giving a reciprocal thump to the chest. It gave of the fine detail and impeccable imaging that really brings music to life with heart and soul.
A blisteringly dynamic and powerful presentation.
A simple recording but then they are usually the hardest to get right.
I’ve played everything from Jazz to Glitch Techno and the paradise took it all in its stride never tripping once.
Firstly
Hissss? What hiss?
This has to be one of the quietest phono stages that I’ve ever heard. No hum and a pretty low level of hiss. BTW I have Texas Naked foils as my RL’s which may help keep the noise floor low (or maybe not).
The first thing that becomes pretty obvious is the deep, wide presentation which is vast along with pin point imaging which is quite incredible. The top end is so sweet and lucid but without ever straying into glare or grittiness (so no aspirin needed). The bass is tight, well rounded and soooo deep but at the same time always tuneful.
The listening session was long ending up with a huge stack of played favourites waiting to be returned to the shelf.
I’ve tried to avoid the HIFI mag type listing records that most people have never heard but can I play just one record?
Thanks for the indulgence.
Rodrego y Gabriela which for those who don’t know it is Spanish/Mexican guitar music (kind of). It has a great version of ‘’Stairway to Heaven’’ BTW.
Anyhow the first track ‘’Tamacun’’ is a real scorcher and turns quite a few stages I’ve heard to a blurred mush pretty quickly. (I saw them a few years ago at Glastonbury and they were awesome. I was going to take Dad but he said he felt a little old for such things).my present phono does a nice job of portraying one guitarist sitting on the others lap but not so the paradise which clearly presented two guitarists sitting comfortably apart. It also did a super job of portraying the interplay between musicians with all of the fingers on frets that make the performance more real and present.
Every strum, pick and flick perfectly rendered and every thump on the guitar body giving a reciprocal thump to the chest. It gave of the fine detail and impeccable imaging that really brings music to life with heart and soul.
A blisteringly dynamic and powerful presentation.
A simple recording but then they are usually the hardest to get right.
I’ve played everything from Jazz to Glitch Techno and the paradise took it all in its stride never tripping once.