Eros Alternate Build Thread

[Paul Joppa]

1) Yes, I believe the 100uF bypass across the Eros 6922 cathode resistor is a player, and a better capacitor is likely to make an improvement.

2) The 100uF and 2200uF cathode bypass capacitors are chosen to maintain suitable phase margins for stability in the servo bias loop. The symptom would be a very slow pumping action, which should be easily audible. But so far in my experimentation, I have never actually produced this problem. My analysis and modeling is too crude to give detailed answers (also the tube and transistor gains will vary between devices, and with temperature) so I can't say clearly what values will not work. For what it's worth, making the small one larger and the large one smaller would be going in the wrong direction.

[xcortes]

Thanks Paul,

that's good info.

[Grainger49]

   .  .  .   For what it's worth, making the small one larger and the large one smaller would be going in the wrong direction.

So the 100uF could be smaller and the 2200uF could be larger?  Or are you referring to the voltage rating or physical size?  That would make my above statement vice versa.

[xcortes]

I have the layout ready. The section above the dashed line is the vertical plane on the back. The section below is the horizontal plane on the bottom of the chassis. I think I'm ready to start detailing the FPE chassis.

[Paul Joppa]

So the 100uF could be smaller and the 2200uF could be larger?  Or are you referring to the voltage rating or physical size? 

Haha! Sorry, it was unclear and has been a confusion before. Yes, from a stability standpoint the 100uF could be a lower capacitance and the 2200uF could be a larger capacitance. Below about 50uF, the 6922 cathode bypass will have an audible effect on bass extension and I do not recommend it.

I think 160v is close to an optimum rating for the 100uF if it is electrolytic, and the 2200uF should have a low voltage rating, like 4 or 6.3 volts. Higher voltage ratings should work; they will eventually lose their ability to withstand the full rated voltage but should continue to perform well at lower voltages as long as it's enough to maintain the chemistry. Sorry I don't understand that low-voltage chemistry very well yet.

[xcortes]

Thanks for clarifying. I had understood it the other way around!

[xcortes]

Here's a candidate:

http://cgi.ebay.com/BLACK-GATE-NH-series-electrolytic-capacitor-68uf-350V-/220665924138?pt=LH_DefaultDomain_0&hash=item3360b6ca2a#shId

[xcortes]

Mike Percy confirmed he has in stock the Standard Black Gates 100 UF 160 V at $13.95. That's what I'll use for the 6922 cathode resistor capacitor.

I think I'm done with capacitors. Now to resistors...

[xcortes]

This is the on/off switch:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=360-1784-ND

Since it will be mounted from the inside on the frontpanel I will use a #4-40 threaded hole placed on the reverse side.

[xcortes]

I asked IAG audio about the thread size of their board and strips. Answer: "All boards and strips use US 4-40 thread size"

[Brillo]

I'm in the process of installing AuriCaps in place of the .01uf and .03uf stock caps.  Can someone confirm I have the lead orientation correct before I finalize? 

.01uf Caps:
AuriCap red lead to T4U and black lead to T5U
AuriCap red lead to T12U and black lead to T11U

.03uf Caps:
AuriCap red lead to T2U and black lead to T1U
AuriCap red lead to T14U and black lead to T15U

Basically, just match black to black?

Thx
Chris

[Paul Joppa]

You are correct.

[johnsonad]

Chris,

Do you have enough room in there to stuff the Auricaps in?  Also, how close did you match them and who may I ask did you get them from?

Regards,

Aaron

[pro_crip]

Xavier, would you be so kind as to publish your BOM? I'll be building my own Eros, hopefully shortly, and having that info handy in one spot would be a boon to all eros builders. Thanks for listening.

Rich

[xcortes]

My project has slowed down. I have no more BOM than what is documented in this thread. At this point it looks like I will build it in the stock chassis with a few minor part changes.