Phono stage, what capacitors?

[Reid Malenfant]

Hi guys & girls (i do recall seeing at least one here ;) ) I'm just about to start a little project up & i'd like some advice if anyone can help :)

I have just purchased a rather nice quality phono pre amp kit with balanced outputs. Specs look absolutely excellent & knowing the ICs used it should sound pretty good to. The only thing is it's not exactly using top quality capacitors for signal transmission & before i go & stuff this board i'd much rather get decent caps in there beforehand.

You see it's a rather thick fibreglass board that is through hole plated & then gold flashed. Even though i'm used to soldering & desoldering including through hole plated stuff i'd rather not have to :lol:

So what suggestions do you have? There look to be one cap each on the left & right MC input & two each in the feedback network surrounding the MC gain stage (these will all be passing audio signals). All are 220uf 35V. Though these values probably provide such a low LF corner frequency i could get away with 100uf most likely.

The MC stage then feeds into the MM stage (a selector switch decides which is used) & again we have one cap on each channel (22uf 50V) & one on the feedback loop of each channel (220uf 35V).

Finally 4 caps on the output because it's balanced (220uf 35V).


I appear to have located a load of Elna Cerafine caps at a reasonble price & i have also found a few Silmic at what looks like a good price. However i'd like others opinions on what might be good coupling capacitors for use at these really low voltages.

Thanks in advance for any replies :)

[Techno Commander]

I presume they are electrolytics?
Nichicon are rather good and well priced.

[Reid Malenfant]

Indeed they are, non polarised at that as well ;) I was figuring on bypassing them with something like 220nf or 470nf film caps, not that it's really needed but i have quite a few kicking about.

[Mike]

Oscon are rather excellent for the bypass caps... I use 220uF 35V ones in my own phono stage, so I feel pretty confident in recommending them.

[Reid Malenfant]

Oscon are rather excellent for the bypass caps... I use 220uF 35V ones in my own phono stage, so I feel pretty confident in recommending them.
Yes i looked at those as well :) When you say bypass caps do you mean more of a power supply thing as in from ground to each supply rail? If so that's also good as i might have some kicking about here anyway. If not you just reminded me i have some black gate caps.

What i'm really after is something great that will transfer AC but at really low voltages. More of an audio than a decoupling capacitor.

Cheers for the input though Mike :) At least you reminded me of things i might have to find. Could be in the shed, loft, greenhouse (no kidding :lol:) or in the house - somewhere :doh:

[Mike]

Hi Mark,

They're in the signal path bypassing the cathode resistor...

It's not the best pic but you should be able to get the idea.

*EDIT*... just checked and they're actually 220uF 10V, not 35V!

http://img829.imageshack.us/img829/5492/phonor.png

[Sahib]

That cap is to provide AC ground to the signal to compensate for loss of gain. Although strictly speaking using Oscon there would be a bit like cracking a walnut with a sledge hammer, in the world of hobby the cost of it is nothing.

[Mike]

That cap is to provide AC ground to the signal to compensate for loss of gain. Although strictly speaking using Oscon there would be a bit like cracking a walnut with a sledge hammer, in the world of hobby the cost of it is nothing.

That's true... there is a noticeable (and worthwhile - at least to me) increase in gain. Particularly at low frequencies. :)

[Mike]

I have just purchased a rather nice quality phono pre amp kit with balanced outputs. Specs look absolutely excellent & knowing the ICs used it should sound pretty good to. The only thing is it's not exactly using top quality capacitors for signal transmission & before i go & stuff this board i'd much rather get decent caps in there beforehand.

Hi Mark,

Could you post (or point to) a schematic?... It might be helpful. :)

[Snoopdog]

How about these ClarityCaps as fitted to the latest 'Special Edition' of the Whest PS.30 RDT mc/mm phono stage:)

http://i3.photobucket.com/albums/y76/crystalref/005-4.jpg

[Mr. C]

Hi Steve,

Quick question for you, can you use the balanced and singled ended outptuts at the same time?

Cheers Tony

[Reid Malenfant]

Hi Mark,

Could you post (or point to) a schematic?... It might be helpful. :)
I'd love to, the only thing is i'd probably be breaking copyright laws :rolleyes:

Let me see what i can do. What i can tell you is it's a design by Douglas Self & it was/is the phono stage used in his precision pre amp that made as a load of articles in approximately 1996. This is now being manufactured by The Signal Transfer Company in West Yorkshire. If you have the book "Self On Audio" you'll no doubt find the circuit diagram in there ;)

Let me see if i can find a link to a circuit diagram, nope but you can have a picture (http://www.signaltransfer.freeuk.com/RIAAbal.htm) :scratch:

[Snoopdog]

Hi Steve,

Quick question for you, can you use the balanced and singled ended outptuts at the same time?

Cheers Tony

Hi Tony

Not sure. You would have to ask James Henriott.

I have only tried the Whest with single-ended interconnects albeit that I aslo have balanced inputs on my Karan preamp.

Martin T uses balanced connection with his PS.30 and prefers it.

[Mr. C]

Hi Steve,

I was wondering if the balaned output stage was buffered in any way, as James (nice guys has suggested best NOT to use both.

Any chance of mailing me a picture of the whole board please Steve.

Many thanks

Tony

[StanleyB]

Is this topic not one for the Drawing Board, rather than the Blank Canvas:scratch:?

[Snoopdog]

Hi Steve,

I was wondering if the balaned output stage was buffered in any way, as James (nice guys has suggested best NOT to use both.

Any chance of mailing me a picture of the whole board please Steve.

Many thanks

Tony

Tony

Pictures emailed to your inbox at info@coherentsystems

Regards

Steve

[Reid Malenfant]

Is this topic not one for the Drawing Board, rather than the Blank Canvas:scratch:?
I did consider that, yes. However as i only want input on peoples thoughts regarding different capacitor types for use in a phono stage it's not exactly a DIY project yet ;)

When it comes to building it i may well put a thread up where you suggested :)

[StanleyB]

I did consider that, yes. However as i only want input on peoples thoughts regarding different capacitor types for use in a phono stage it's not exactly a DIY project yet ;)

When it comes to building it i may well put a thread up where you suggested :)
In that case it's one for the Analogue Art section, or not?
It's not my BB, but sticking to the structure is most helpful to anyone looking for specific info in the allocate section I would think :rolleyes:.

[Ali Tait]

I like the Clarity Cap ESA's.Cheap and very good IMO.

[Mr. C]

Many thanks Steve :)

If you were looking to try a 'seriously good cap'

Then so far I have tried absolutely nothing that has come even remotely close, mad money without question though if you really wish to hear what is really going on these have no equal.

Amazing caps (http://www.v-cap.com/copper-teflon-capacitors.php)

However hearing is believing (we have no connection with VH-audio either)

Have just finished off a new dac, previous we used the straight Telfon v-caps which are just superb, but these take thing to a new dimension.

[Reid Malenfant]

In that case it's one for the Analogue Art section, or not?
It's not my BB, but sticking to the structure is most helpful to anyone looking for specific info in the allocate section I would think :rolleyes:.
In all honesty i'm not fussed what section it goes into...

If a mod reads this please have a good think about what section this thread should be in & please feel free to move it to the relevant section - thank you :)

My apologies if i stuffed it in the wrong section to begin with :doh: I had no idea it'd cause any upset :scratch:

[Ali Tait]

If you want to spend some money,then the best I've heard so far are SCR teflons,not cheap but worth it IMO.

[Mr. C]

,not cheap but worth it IMO.

Ali,

You hit the nail on the head there, it is justifing the cost v's what possible gain could be achieved.

[Reid Malenfant]

Hi Ali, perhaps i just ought to add that the capacitors will only have so much room on the PCB. I know there appear to be a couple of different things being discussed on here so fair enough ;)

I have space for maybe 12mm diameter radial electrolytics & that's pushing it.

Just waiting to hear back from a chap with a load of Cerafines to see exactly what size they are. I have also located a load of decent film caps which i'll use to replace the cheap 63V versions on the board for the high pass filter (20Hz).

That seems a little high to me so i'll recalculate the resistors in the filter to lower it to about -3Db @ 15Hz. Apparently the higher the capacitor voltage used in this filter, the lower the distortion, the same will apply (in the audio passband) by lowering the frequency that the filter cuts off at. I have found a load of 400V caps that'll fit :)

[Mike]

I like the Clarity Cap ESA's.Cheap and very good IMO.

Err... 220uF? :scratch:

You can get the 22's but they'll be bloody big! And they're rated at 630V which might not be ideal for the voltages even if you could get them to fit on that board (http://www.signaltransfer.freeuk.com/RIAAbal.htm).

[Ali Tait]

Oops,missed that bit! Ok,forget film caps then,doubt you'd get anything that would fit.

[Mike]

Oops,missed that bit! Ok,forget film caps then,doubt you'd get anything that would fit.

:);)

[Reid Malenfant]

Finally bought all the caps i need to do a better job with this thing :) All caps that will pass a signal will be Sanyo Os-cons & the two caps that are used as power supply bypassing will be Panasonic FC caps. The difference here being that instead of 220uf i have managed to source some 2200uf that will fit :lol:

Supply will be NiMh rechargable batteries which will be recharged automatically as soon as the phono stage is powered down. Looks like i need to buy 30 x AA NiMh cells, found them pretty cheap though - so no ripple at all when music is playing. With the circuit current draw the whole thing will be good for 24HRs of playing time with no need for recharging.

Bring on the cap delivery! I want to get started ;)