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Phono board options

How do you want the functionality split up

  • Four small boards

    Votes: 6 18.2%

  • Two boards, each a complete channel

    Votes: 13 39.4%

  • Two boards, stereo front end and stereo EQ

    Votes: 1 3.0%

  • One big board

    Votes: 11 33.3%

  • Don't care

    Votes: 2 6.1%
  • Total voters
    33
  • Poll closed .
Chops54 said:
Switching isn't ideal though is it? It makes the signal paths longer for a start which seems contrary to this design or am I missing something here? I'd suggest having plug in modules as the worst case scenario and if anyone has more than one turntable I'd suggest they have more than one phono stage.
Click to expand...

I'm not keen on plug-in modules - you have even more crappy connectors in the signal path. Unlike a switch, you don't even get wiping action to the surfaces clean.

For the common case (one cartridge), everything can and should be directly wired.

As the switch is after the first stage, the signal levels are fairly reasonable, and so it is no worse, but no better, than the main source selector problem.

Multiple complete phono stages, by building an EQ stage for each path, is another option if people prefer to do things that way; it involves a lot of extra parts and is undoubtedly the millionaire's route.
 
PigletsDad said:
Multiple complete phono stages, by building an EQ stage for each path, is another option if people prefer to do things that way; it involves a lot of extra parts and is undoubtedly the millionaire's route.
Click to expand...


I didn't realise this phono stage was going to be that expensive ;)
 
df_genius said:
I've just had the head amp transistors to find for this build, I ended up with 2SA1085 (could not find 2SA1084's anyhwere but 1085's just seem to be rated to higher voltages) and 2SC2546 off ebay. I was planning on building this with veroboard, but can wait for PCB's. A some point I plan to compare it with my Salas Jfet phono stage which I have just finished (when I have optimised the ground configuration, I am still having hum problems).

PD, with all MC phono stages being particularly sensitive to ground layouts, can you comment on a recommended ground configuration for this cct, or at lease a decent place to start from?
Click to expand...

The input, from the cartridge, should be isolated from the case or other earths, and be routed direct to the input board. The layout I used was to use star earthing within each module, then to have an overall star connection, with a single earth return from each module within the phono amp (or the whole pre-amp if you integrate it with a line stage).
 
df_genius said:
I've just had the head amp transistors to find for this build, I ended up with 2SA1085 (could not find 2SA1084's anyhwere but 1085's just seem to be rated to higher voltages) and 2SC2546 off ebay. I was planning on building this with veroboard, but can wait for PCB's. A some point I plan to compare it with my Salas Jfet phono stage which I have just finished (when I have optimised the ground configuration, I am still having hum problems).

PD, with all MC phono stages being particularly sensitive to ground layouts, can you comment on a recommended ground configuration for this cct, or at lease a decent place to start from?
Click to expand...

DF Genius
What is your opinion on sound quality from the Salas phono

Alan
 
Hi PigletsDad,

Which 2SK117's?

2SK117-BL
2SK117-GR
2SK117-Y

Is there a UK supplier?

Capacitors planning to use Wima MKS2 or MKS4 unless there is some thing better.

Sharif.
 
audioflyer said:
Hi PigletsDad,

Which 2SK117's?

2SK117-BL
2SK117-GR
2SK117-Y

Is there a UK supplier?

Capacitors planning to use Wima MKS2 or MKS4 unless there is some thing better.

Sharif.
Click to expand...

Dalbani certainly have 2SK-117 in the UK. In the US I know Ampslab have them.

For the MM application, I would go with the higher current BL selection, but GR would work too if you can't get BL.

For the small value caps, I would go polystyrene 5%; if you can get a tight tolerance (2% or 1%) so much the better. I would choose some sort of polypropylene for the big coupling caps, say Wima MKP or FKP. MKS would work, but they sound a bit flat and grey.

I am unconvinced of the merits of boutique caps, but you waste/spend a lot of money on fancy parts. Personally, I would go for good quality main-stream parts like those suggested.
 
337alant said:
DF Genius
What is your opinion on sound quality from the Salas phono

Alan
Click to expand...

Alan,

Initial impressions are very favourable indeed. The Salas stage is held in very high regard, I plan to get a PD phono stage built as well to compare. What I will say is that the Salas phono is largely governed by the quality of the power supply and resistor values/supply voltages need to be tailored to match the idss of the JFets used and the gain required, so it's not suited to a beginner

From what PD says his phono stage has good PSRR and would appear to need little customisation providing one of the three flavours he has specified fits the bill (unless you have a cartridge with uncommon output levels and load requirements I'm sure you will be fine)
 
Yes, there are links from here to the schematics for the various front-end variants and the EQ board. If you can wait a bit, I will search them out and post them again.

The main input board is easily customisable, so even fairly wacky cartridges should be supportable. I gave parts values for low output MC, high output MC and MM.

The FET board is a valid alternative for MM or other high impedance types (like say the very rare Stax electret cartridge). It will have very marginally lower noise at high audio frequencies when used with strongly inductive MM parts like say a Shure V15. In the midrange, where the ear is sensitive to noise, both designs should be indistinguishable, and limited by the intrinsic noise from the source. It would work OK for a high output MC, with a minor noise penalty, but is not optimal for a low output MC.

The final variant is for ultra-low output MC cartridges, like the Kondo, or some Ortofon models. Unless your cartridge puts out less than say 200uV, I would stick with the main option, using the suggested parts values for low output MC.
 
337alant said:
Thanks PD look forward to seeing that :):cool:

Alan
Click to expand...

Sorry,

It will take a bit longer than I thought - my pro flickr account needs to be renewed, and the images we want are in the section that can't be seen with the free account. This may take me a day or two to sort out; my login credentials are on a different machine.
 
That looks pretty good Sharif. Personally I wouldn't know where to start with something like this so I think you should take a pat on the back for getting it this far. I'll be interested to see what the single MM and MC boards look like too.
 
Looks good Sharif.

What are people planning on using for regulators? I know PD said that an LM317/337 is fine for the 24V rails, and the 12V rails need a quality power supply, but I guess some of us will want to use the best regs we can. Are op-amp "super" regs or the latest generation of shunt regs well suited to this phono stage?

Can we suggest a power supply board for those with less experience that is relatively easy to build?
 
I think the HackerCap is a good fix for most diy projects. A little bit bigger than the MiniCap but it's a versatile one size fits all psu board for anything needing a split rail supply. I just need some more! As for the regs, once I've got my VBE boards ( using Hacker's VBE circuit ) installed in my NCC200s and I'm happy with the results, I'll probably go with those again. The psu boards and transformer go in one box and the phono board(s) and the regs go in the other.

Edit. A bit rude of me there not to add that PD may already have a psu/regs outlined for this. Apologies if that's the case.

Great job with the dedicated boards btw Sharif. In the last image, the MC only version, the two halves of the board aren't symmetrical ( the six transistors, top and bottom rhs ) Can you expand on that please?
 
Chops54 said:
Great job with the dedicated boards btw Sharif. In the last image, the MC only version, the two halves of the board aren't symmetrical ( the six transistors, top and bottom rhs ) Can you expand on that please?
Click to expand...

On a mirrored board layout the transistors may have to be rotated around to prevent the tracks from crossing over, or worst still a link being added to connect it to the relevant track.

Sharif.
 
This is the regulator supply I'm planning to use for the testing the boards.

Its based on the LM317 and LM337 tracking regulator.

http://www.flickr.com/photos/60527312@N06/6240099300/

6240099300


Sharif.
 
People like to use different regulators and supplies, and for a DIY project I think it is probably best to give that choice. My suggestion is to use LM317/LM337 set to +/-24V for the EQ board, and something simple, like say a TR, to step this down to +/- 12V for whichever front-end board is used.

I'm not sure I see a lot of added value in a mirrored layout, although it looks nice.
 
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