EAR834 - component questions...

[netphreak]

Hello all,

I have ordered the Ear834 kit including valves from Douk - not very impressed with the component specs vs. what's printed on the PCB... Can anyone help me with my somewhat limited electronic skills here?

• 1: The PCB says 9 x 22uF/400V (3 on the power PCB, 6 on the preamp PCB) - I received 9 x 47uF/400V. After quite some "googling" both values seems incorrect, and I should use 33uF/400V. Now - how important is this? Will the 47uF/400V capacitors be OK to use?
• 2: On the preamp - PCB says 2 x 100uF/10V - I received 2 x 330uF/16V. OK to use???
  
• 3: On the preamp - PCB says 0.15uF/250V - no markings on my received resistors... Should I order new ones? Should these capacitors be non-polarized (nothing indicates + or - on PCB) - and what type is preferred?
  
• 4: Transformer - should I use toroidal, r-core or something else? Is this a component I should spend a lot on, or go cheap? I plan on having the power and preamp in the same cabinet, but it will be quite wide/deep and I will isolate power and preamp as good as I can.
• 5: I notice many builders us a choke on the power PCB. Why should I use one?
• 6: Some builders add a volume pot - why? To make volume of turntable equal to other inputs like CD etc.?
• 7: If I should replace some components with higher quality ones - which ones would make the biggest difference?

I hope at least some of my questions are understandable

[Jay]

Q 1/2,   I had this same kit with what looks like the same components they do all work ok. if your components look the same as mine then carry on
 
3,  If there not marked + - then it doesn't mater which way they go.

 

[Jessica_K]

1/. Any caps will work here as long as they are 400V or more and 22uf or more
2/. Again this cap has limited effect on the amp. It can have a slight effect on the RIAA. The voltage required is low so any voltage from 6.3V is good here. If you use a Elma simec II 100uf  6.3V here they are cheap (pence) and are sonically very good here
3/. These caps should be high voltage (400V or more) non polarised. I like the mordorf evo oil
but it's personal preference
4/. R core is said to be sonically better than toroidal better than standard EI core. I personally would not spend more here than being spent on the other components.
5/. Choke or no choke. There is a small sonic difference but worth it
6/. The amp has a very high gain that does not suit all forward amps. Some use direct input to a power amp so need a volume pot. So it's more to do with usage though for just reducing the output a simple divider would be cheaper and better
7/.  Umm well put in good signal caps (the non polerised ones) and I have changed the 47k input resistors to as low as possible noise types. I have used Kiwame. And finally the RIAA caps must be silver mica and 1% if not already.

Robert

[netphreak]

Thank you for your answers so far. Based on the answer from rekinchin I have ordered:

2 x ELNA SILMIC II 100uF/10V (I'm sure 6.3V would work fine as well, but I feel more comfortable with higher or similar voltage as on PCB...).
2 x 0.15uF/450V MUNDORF M-CAP® EVO OIL (since I have no personal references myself - let's hope the price tag will be justified).

Volume pot is not needed for my current usage, if I'll need it at a later point I can always add it then.

[Jessica_K]

Also use mordorf caps for the 1uf and 12/15nf if you can afford it, even if they are the non oil type would be good
Robert

[netphreak]

12/15nF?

I may be tired tonight, but I can't find any caps lower than 0.1uF...

[Chris65]

Think he meant 120nF/150nF = 0.12uF/0.15uF.

[netphreak]

That was my first guess also, but since I already took the advice and ordered 0.15uf caps... Oh well, I'll find some Mundorf's @ 1uF anyway

[tubeactive]

 Greetings ! Your concern with parts quality and values are good concerns. Surely, you have seen the various LH threads about this well received unit, right ? This one has the schematic on a recent page:

http://www.lencoheaven.net/forum/index.php?topic=20984.375

 I hope that comes in handily for you.

   Now, let's discuss some parts, shall we ? The type of .1 or .15 uf coupling caps you choose will be important to the sonic signature of the completed unit. Surely, for now, use what parts you have on hand. Then, after the preamp works, you can sub in "different" types of caps which will yield "different" sonics. The 330 uf may actually be "too high" for this circuit, with the 100 uf Silmic II definitely preferred. Every R-C "network" has a time constant. Multiplying the R x C = a time constant, measured in uSeconds. Then, divide 159,155 (a mathematical constant) by the time constant and you get the frequency at + or - 3 db depending on the particular circuitry. In this case, that 100 uf bypasses a 2200 Ohm cathode R. It "was" a critical design value. It's resulting time constant is near .7 Hz. Using the 330 uf yields a time constant of .2 Hz, which does not seem much different, but is actually very different. I really do not want to confuse anyone with this math, but the 100 uf will be -3 db at .7 Hz and the 330 uf will be -3 db at .2 Hz. The lower we go in frequency, the more the possibility of rumble and subsonic aberrations due to possible tonearm/cartridge resonance mismatches. That is why I mention the 100 uf is probably a critical decision. Also, this part of the circuit lies within the active feedback phono EQ loop. So, the sound quality and part value is definitely very important. Silmic IIs sound very endearing, by the way...
  The other 22 uf, 33 uf or 47 uf are for power supply "decoupling" or hum filtering. More importantly, these caps contribute to the sound, especially the bass solidity, definition, impact and control. Your 47 uf are fine for those positions.
  The 1 uf caps are for the output coupling cap, the output of the cathode follower. Sonic importance is significant here. Cathode followers can be made "better sounding" with the right cap. Mundorf might be great. Other Paper In Oil (PIO) or polypropylene might be great also. Which type you prefer will be up to you to decide. Remember that the plasticized capacitors, tend to require a long "break-in" time to settle into the circuit. Consider this before making any sound quality judgements. We can get "too hung up" on parts types, rather than simply listening to the music. However, since you are literally "building" a product, the effects of varying grades and types of parts can be understood by you, in real terms. The DIY approach allows us to build a product as great as possible...

[Jessica_K]

Signal cap values required from input side to output side of the PCB
150nf = 0.15uf
10nf = 0.01uf  (some use 12nf or 15nf here, effects base response)
1uf

All above are available in 650V Mundorf MCap EVO Oil Capacitor
From hifi collective so should be found elsewhere

Robert

[netphreak]

tubeactive: thank you so much for a VERY educational and enlightening answer! Oh yes, I have been reading thoroughly before posting, in here and elsewhere. It's a steep learning curve, but I'll get there eventually
Alright. I'll follow the advice and keep the 0.1uF and 1uF that I already soldered - and place it on top position of things to replace after some listening - together with a choke and better tubes

rekinchin: I still can't find any 0.01uF caps! You are referring to the 0.1uF(100nF), right?

I can get an R-Core transformer off ebay for about US$ 40,- Will this be a good choice? Toroidal is a little more expensive (not by much). I have read that R-Core will be a good choice, but it may have a larger magnetic field which could be e problem for the tubes... Or?

Thank you for all the answers to a new user in here

[Chris65]

Signal cap values required from input side to output side of the PCB
150nf = 0.15uf
10nf = 0.01uf  (some use 12nf or 15nf here, effects base response)
1uf

Seems to be some variation on the second coupling cap, some circuit diagrams show 0.01uF. Others & the Douk PCB have 0.1uF.
This circuit diagram you provided earlier also has 0.1uF (C4).

           

[Jessica_K]

That was an early simulation schematic Chris65. The correct value is 0.01uf
Such as
       EVOO-010: 0.01uF 650V Mundorf MCap EVO Oil Capacitor
       From www.hificollective.co.uk

Changing this value to 100nf produces a lift at 20hz of about 0.25db


Although (using that schematic above) you can remove it all together by removing R7 and R14 along with the cap C4 and replace with a bit of wire where R14 was. PLUS changing the value of R6 to 120k. This lifts the bass a little more sounds good and saves money



Robert

[Chris65]

Call me Chris, please.
Just pointing out the variations, & your simulation was titled 'original'. An original schematic has 0.1uF caps, of course that may have been changed later.

Changing this value to 100nf produces a lift at 20hz of about 0.25db.

Would that be audible? Looking at the builds in the main thread, plenty have the 0.1uF caps.

[Jessica_K]

Technically Chris no, the min is said to be 1db, however. Small difference in the shape of the response can give different "feelings". Such as dull, bright, warm, bass heavy etc. It all comes down to personal preference and the rest of the system. Overall the frequency response limits remain same with either part or none.

The simulated response is if I remember right is about 0.75db. But even using 1% components in reality is likely to be around 1.5db (+/- 0.75db)

Robert