OPENAMP1 - MM phono preamp open project

[vardenis]

Has anyone bought OPENAMP1 pcb, changed their mind and would like to resell it to me?

[AudioLapDance]

Originally Posted by kamis

NE 5534 op-amp is BJT type, but it is suitable for high inductance MM cartidges since it has low current noise of only 0.5pa, four times lower than ultra low noise op-amps. And its total noise data is decent.

Hi Kamis, it looks like you understand the details. Sorry if I implied otherwise.

Here's the NE5534 noise.
NE5534 noise.png

Here's the OPA627 noise.
OPA627 noise.png



NE5534 In=0.4pA /(Hz)^(-1/2)

OPA627 In=1.6fA /(Hz)^(-1/2)

femto! 0.4pA vs 0.0016pA or 400fA vs 1.6 fA

(but I have no idea if the tests are identical enough ... and how do you even measure femtoamps?!?!? :-0)

And here are the graphs:
NE5534
NE5534 noise graphs.png

OPA627
OPA627 noise graphs.png

[PMA]

In addition, 5534 is not unity gain stable and must not be used in this preamp!!!

[kamis]

I used NE5534 with 4.7pf between pins 1and5, as Doug Self did in his all active RIAA phono , to force it in unity gain mode.
Of course OP 627 is better, but NE5534 is suitable ,same as OP27 op-amp.
I think that even TL071 is good enaugh-buffer is taking the hardest job to drive low impedance RIAA eq.

[AudioLapDance]

Originally Posted by kamis

I used NE5534 with 4.7pf between pins 1and5, as Doug Self did in his all active RIAA phono , to force it in unity gain mode...

You should have said that before. Someone might have taken your suggestion and ended up with a potentially unstable preamp. (And I still don't know if it will work like that in PMA's schematic?!?)

Originally Posted by kamis

... Of course OP 627 is better, but NE5534 is suitable ,same as OP27 op-amp...

OPA627 and OP27 are FET input opamps with ~400 times less current input noise than NE5534. And that's just one spec ... I don't think you fully appreciate the extremely high level of technical performance that PMA has achieved with the OPENAMP1. Please review his measured graphs (not just 'in theory' or "I think the performance is this good") and compare them to other designs.

I'm just gonna say it ... It blows them away!

And ironically, it's better because of the subtle details that you keep implying don't matter! Do you see the irony?

Originally Posted by kamis

... I think that even TL071 is good enaugh-buffer is taking the hardest job to drive low impedance RIAA eq.

(did you check to see if it was unity gain stable, or FET vs BJT input?)

...

"Suitable" and "good enough" are not suitable and good enough for PMA, that's why he created his superior phonopre. Lucky for people like me, that don't have his knowledge, skill, perseverance, testing equipment or gruff exterior, because I can get the benefits of his work, if I follow his instructions!



Ok, let's get back to the point of this thread:

PMA's buffered phonopre! Which he states must use OPA627 (or at least OPA134) to achieve the posted performance.

[kamis]

First of all, OPA134 has worse measured spec than NE 5534, but it is said to be more immune to RFI noise than BJT inputs. Tl071 is unity gain stable very old J-Fet design . OP27 is aBJT op-amp. Input current noise of NE 5534 is low enough not to increase total noise of the circuit with high inductance MM. I used Shure VST-V cartridge and my very similar preamp was dead quiet.4oo times better noise has no any influence, not even half a db.
I listened to almost all known audio op-amps in my various phono preamps, but J-Fet input complemantary two stage RIAA DC servoed is much better ,
Preamp which is subject here is very good, easy to build and I wish a good soldering to all builders.

[AudioLapDance]

Originally Posted by vardenis

Has anyone bought OPENAMP1 pcb, changed their mind and would like to resell it to me?

...from my cold, dead hands!

This is an issue for those that don't have the official PCB (I believe I got the last one).

Proper PS bypassing of both the 627 and the 1010 buffer, proper grounding, low-level signal routing ...

Perhaps a couple of people who know what they're doing could post their point-to-point layouts?

PS No, PMA won't be doing any more soon (please don't bug him, we need him for his technical advice, not simple corrections) and I don't think he'd be OK with a copy of his PCB...

[mlloyd1]

very slow progress, almost all passives mounted so far.
hopefully faster progress this weekend when the women are out shopping and leave me in peace to play

these are the 4 cartridges I've got to play with.
will wash up some vinyl tonight then go to bed.

mlloyd1

[AudioLapDance]

You Sir, are a trailblazer!

Looking good! What parts have you selected?

Res:
Yageo metal film
Vishay RN

Caps:

Bypass:

.1/50v metal films
Panasonic FM electrolytics

And those are some sweeeeeet carts. I'm especially interested in the M97xE (I bargain bin shop and end up with a lot of warped records: this cart specializes in warped records!)

[mlloyd1]

thanks!

just the usual parts i have in my stock; the bypass film caps are some panasonic metalized polyester i happened to have that would fit. they've served me well as bypass caps for many years. the frequency shaping caps will be wima or vishay fkp series. the cartridge termination caps will be some nice polystyrenes i have. i'll match up caps up tonight, although i might have already set aside some matched sets from years ago.

btw, i been using this L/C meter for years: it works great. back when i used to work for a telecom giant and had access to nice and expensive "toys", i compared it against some very expensive L/C meters and it was just as accurate. also helped me get my turntable cable capacitance very low also. can't beat it for $100.

my biggest issue right now is i really like the terminal blocks PMA selected, but I don't have any of those and can't find a US source (google hasn't been MY friend this time). anybody have any ideas? they are the wago255 series ... i'd order some from overseas, but I really don't need any other parts right now and i'm sure the shipping co$t$ would eat me alive ...

thanks,
mlloyd1