DIY EAR 834p phono stage - a short evaluation/ test with those chinese PCBs

[spaceistheplace]

John, on one channel one of the protection resistors is smoking when I power up so I need to find the short, because that it what it most likely is. But right now I am spending most of my free time just chilling out as I am trying to not upset the strained muscles in my chest after lifting a heavy steady off the lathe about 5 weeks ago. Its been painful and very slow to heal, old age again. 

Andy

I didn’t see this before. Are you talking about the dropping resistors on the amp board?

Have you checked your wiring and psu arrangement?

I had a similar issue at one point because a very fine strand of wire was not soldered and touching another track.

Keep in mind the Douk has exposed tracks. But you are using the xuling?

[spaceistheplace]

Those are the ones, 1uf arizona blue cactus (think they are rated at 200 though so not sure tbh) for the 0.15 i have some jensen pio either alu or copper, the copper are larger but i think i can make them fit

PS the Jim’s audio board is quite different in its heater wiring from the Douk and Xuling (series, not in parallel). I would avoid it. I think the others are superior.

The Douk board is the largest of all. I would go with:

1. my previous advice on mounting beneath the board covered in heat shrink and being sure to ground the casing.

Either way the Arizona 200VDC is under the specified 250VDC. The voltage from V3 is around 150V but you want the higher rating for headroom / piece of mind and to not put the cap under strain.  Also, not having appropriately rated caps can cause *destruction* of your other board components, or especially with the 1uf coupling cap location your other connected gear. Stick with board listed values, especially so for the 1uf Voltage rating. Higher voltage rating is always welcomed as long as it can fit in the board supplied location.

2. You can go with the Sprague and Vishay specified in the build guide for the Douk for a more predictable fit. They are of reasonable cost and are seen in the highest quality components by very reputable audio outfits.

I think any audible difference you would notice between these high quality examples would likely be either sociological phenomenon or the small differences in tolerance.

Again, my two cents and no offense intended to capacitor connoisseurs.

I have been personally unable to reliably differentiate between value and channel matched highest quality coupling capacitors.... the keys in that statement being “value and channel matched”, “highest quality” - polypropylene, PIO, military spec etc. and “coupling” - the .15uf and 1uf values.

Of course, adequate voltage rating is absolutely necessary, with additional padding recommended when possible.

Tubes on the other hand, or RIAA or loading resistor changes I’ve found are instantly and distinctly audible.

So I guess what I’m trying to say is pick your battles wisely; there’s plenty elsewhere to address that will provide a more bountiful return.

Also, always make sure you are using adequately rated parts! Capacitors can explode! It’s not fun or safe!

A PIO (like the Arizona) leaking or exploding is especially unpleasant.

[Irate]

PS the Jim’s audio board is quite different in its heater wiring from the Douk and Xuling (series, not in parallel). I would avoid it. I think the others are superior.

The Douk board is the largest of all. I would go with:

1. my previous advice on mounting beneath the board covered in heat shrink and being sure to ground the casing.

Either way the Arizona 200VDC is under the specified 250VDC. I think this is still acceptable as the voltage across it is around 150V but do not quote me on that. Stick with board listed values.

2. You can go with the Sprague and Vishay specified in the build guide for the Douk for a more predictable fit. They are of reasonable cost and are seen in the highest quality components by very reputable audio outfits.

I think any audible difference you would notice between these high quality examples would likely be either sociological phenomenon or the small differences in tolerance.

Again, my two cents and no offense intended to capacitor connoisseurs.

I have been personally unable to reliably differentiate between value and channel matched highest quality coupling capacitors.... the keys in that statement being “value and channel matched”, “highest quality” - polypropylene, PIO, military spec etc. and “coupling” - the .15uf and 1uf values.

Tubes on the other hand, or RIAA or loading resistor changes I’ve found are instantly and distinctly audible.

So I guess what I’m trying to say is pick your battles wisely; there’s plenty elsewhere to address that will provide a more bountiful return.

Also, always make sure you are using adequately rated parts! Capacitors can explode! It’s not fun or safe!

A PIO (like the Arizona) leaking or exploding is especially unpleasant.

Thanks for the tips! the capacitors were originally marked for speaker crossovers (on the backburner for the foreseeable future) but i saw the values might work so thought i might repurpose them. I hadnt thought about grounding the cases as they arrived already covered in clear heatshrink but it certainly makes sense.

I have some nice bits for the riaa section all closely matched so im looking forward to getting it up and running. I got half of roberts psu done yesterday, once thats done ill start on the 834 board but i think ill need to go through the threads on here first...

[drat]

Thanks for the reply, John.  I do have the .15 PIOs soldered in place. I was mostly curious about the audio effect, that is would I lose a lot of bass as it is in effect a high-pass filter.  I have in two previous builds had bad experiences with the Russian PIOs - to my ears at least.  It could be they require a certain amount of time to "settle in" but I wasn't patient enough for that.  I know many, many people with more knowledge and probably better ears really like them, though, and the designer of my last build highly recommended the PIOs as well.  I'll stick with the .15 PIOs.

Paul

[spaceistheplace]

Thanks for the tips! the capacitors were originally marked for speaker crossovers (on the backburner for the foreseeable future) but i saw the values might work so thought i might repurpose them. I hadnt thought about grounding the cases as they arrived already covered in clear heatshrink but it certainly makes sense.

I have some nice bits for the riaa section all closely matched so im looking forward to getting it up and running. I got half of roberts psu done yesterday, once thats done ill start on the 834 board but i think ill need to go through the threads on here first...

There’s a build guide here which contains most of the relevant highlights from the main thread:

I tried to give everything fair mention, while also not overwhelming people with options.

http://www.lencoheaven.net/forum/index.php?topic=26658.0

[spaceistheplace]

Thanks for the reply, John.  I do have the .15 PIOs soldered in place. I was mostly curious about the audio effect, that is would I lose a lot of bass as it is in effect a high-pass filter.  I have in two previous builds had bad experiences with the Russian PIOs - to my ears at least.  It could be they require a certain amount of time to "settle in" but I wasn't patient enough for that.  I know many, many people with more knowledge and probably better ears really like them, though, and the designer of my last build highly recommended the PIOs as well.  I'll stick with the .15 PIOs.

Paul

Try the PIOs and see.

The bass is much more effected by the 2M resistor location left after the Thorsten mods. See the build guide for resistor selections based upon the type of tube you are using in V2. Leave 2M for new stock tubes like the SPAX7.

Again I’m not saying that caps cannot influence sound, just that the whole thing is a bit overblown in my opinion.  maybe one should address other areas first and then circle back.

Also, it’s a tight squeeze. Many modern audiophile types won’t fit very well and that causes its own possible parasitic issues. This is more important than many think.

The Vishay Roederstein MKP and Sprague Orange Drop are two very high quality alternatives that I’ve confirmed fit well and are in stock at Mouser.

I’ve had great results with the older USSR Mil parts. I haven’t met many I didn’t like.

The K42-Y is extremely similar in construction to the Arizona Capacitor actually.... Arizona Capacitor was formerly Westcap, which made Military PIOs for various harsh conditions in hermetically sealed metal enclosures.

Bringing everything up on a variac would always be my suggestion with capacitors in general to allow them to form, especially so with those that have been on the shelf for a while.

If you find you don’t like them I have some Polystyrenes you might want to try instead.

[spaceistheplace]

Thanks for the reply, John.  I do have the .15 PIOs soldered in place. I was mostly curious about the audio effect, that is would I lose a lot of bass as it is in effect a high-pass filter.  I have in two previous builds had bad experiences with the Russian PIOs - to my ears at least.  It could be they require a certain amount of time to "settle in" but I wasn't patient enough for that.  I know many, many people with more knowledge and probably better ears really like them, though, and the designer of my last build highly recommended the PIOs as well.  I'll stick with the .15 PIOs.

Paul

That depends on the input impedance of what you are feeding it to (the load), not the construction quality so much.

Perhaps in the instance you felt the the capacitor was to blame rather than a better match to your preamps input impedance.

Also this is strictly speaking for the output coupling capacitor. Don't attempt to revise the .15uf position.

Important to note: There are a variety of issues to be very conscious of, as this can have catastrophic results if you don't understand what you are doing- as in totally ruin your upstream gear.

So, be careful. A calculator can be found here:

https://www.v-cap.com/coupling-capacitor-calculator.php

For the capacitors yes, you might give them a day to settle. You can always feed a signal through it but turn off your speakers.

In other news, I've managed 834 posts!

[Chris65]

In other news, I've managed 834 posts!

You'll have to stop posting now John ! Or add another 108 years to your age.

[Jessica_K]

One cap that must never be underateted is the output cap (1uf) as it blocks 150V or so from the cathode of V3, specially if the Thorsten mod is made. If that part fails then the amp that is being fed from the phono amp could see the whole cathode voltage and although a valve amp may have enough headroom to not get damaged you can say bye-bye to any solid state amp unless it’s clamped so rate it as high as possible and at least 250V better still above 350V

Robert

[Irate]

One cap that must never be underateted is the output cap (1uf) as it blocks 150V or so from the cathode of V3, specially if the Thorsten mod is made. If that part fails then the amp that is being fed from the phono amp could see the whole cathode voltage and although a valve amp may have enough headroom to not get damaged you can say bye-bye to any solid state amp unless it’s clamped so rate it as high as possible and at least 250V better still above 350V

Robert

Thanks Robert, thats made my decesion for me! I finished your psu board yesterday btw, thanks for the brilliant instructions, ive not done anything with dangerous voltages before so was great to have the instructions.

[paczin]

Hi all,

Wow, how big this topic became since I last visited it Mine is on build for some time, but I'm not in a hurry. Next step will adding some mods from John's topic. Also i saw this new PSU board from Robert and I think to add it to my build too. My main concern is my transformer, will it be suitable for that PSU?

[spaceistheplace]

230V on the lower end I believe but should work fine. I believe he spec-ed 250V to be conservative. But I’d wait for him to confirm himself.

Also those kiwames look a bit close to the rectifiers in the PSU, maybe even touching? Perhaps mount them underneath the board.

What resistors are you using in the 51k position? That would be a good place for a foil if you so choose.

The electos on the main board seem cramped. I don’t see space for the other 2.2k resistor to be mounted in the first stage.

Everything else looks good. The mods are not too complex, give them a try and report back.

While not a mod per se your tube choices, especially V1 and V2, can make a substantial differences in my experience.

[spaceistheplace]

Something I was reading that may explain my feelings on the 12AU7.

Important to note that our PSU provides somewhere around 280V while Thorsten’s mods of the original circuit reflected I believe a PSU providing less than 200V. The 12AU7 thus may not be the best fit:

“Looking around to find my problem with the last stage, I was reading in details the 12AU7 specs sheet. One parameter catch my eyes;
Heater negative with respect to cathode, 180V max.”

“In my case, Vcathode = 260V, and the heaters are only 30V above ground, so I have 260-30 = 230V, way over the maximum 180V.”

Thread here: http://www.diyaudio.com/forums/tubes-valves/131776-own-version-ear-834p-clone-3.html

Also curious to try the recommended 12AT7 as an improved cathode follower that has specs more in line with our needs.

Like one poster said I think this circuit deserves a better cathode followers however I’m unsure what would be the best practical solution.

Thoughts?

[paczin]

230V on the lower end I believe but should work fine. I believe he spec-ed 250V to be conservative. But I’d wait for him to confirm himself.

Also those kiwames look a bit close to the rectifiers in the PSU, maybe even touching? Perhaps mount them underneath the board.

Yes, they are veeery close, but not touching. Those Kiwames are very big. Good idea to move them to the other side

What resistors are you using in the 51k position? That would be a good place for a foil if you so choose.

Wright, but where is that position? Can't see it on the pcb layout

The electos on the main board seem cramped. I don’t see space for the other 2.2k resistor to be mounted in the first stage.

John, look at this photo, 2k2 resistors I have in this positions. Am I missing something?

Another question - should I replace those 2W Kiwames in green circle? Theoretically they should be 3W... Don't know why I bought that value for this place.

I will also remove those two black quite expensive Mundorfs (fortunately I bought them for a half of the price) and 2m & 3m3 resistors underneath.

[spaceistheplace]

2W is sufficient,I believe the ones in the circle dissipate ~1.2W. However higher values will provide more stability.

The wattage specs on the board don’t reflect actual wattage but are good rules of thumb for temp stability.

On the other point I guess I was just giving a quick glance and it appeared off the way you took the photo, so I take that comment back.

The 51k value is the input resistor.... in the middle there closest to the signal input.