The new "My Ref" Rev C thread

[madisonears]

I just received my kit, and I have a couple questions regarding possible customization.

First, I intend to use this amp to power mids/highs of actively crossed speakers. Therefore, no need for bass below 100Hz or so. In fact, if it improves the handling of the upper freq's and allows me to safely use lower impedance midrange speakers, I would prefer to filter lows at the amp's input. Can I adjust the DC blocking filter C1/R1 to raise the cutoff without harming the rest of the amp? Could I use this filter to eliminate that portion of the active xover altogether? Is it 6dB/octave? In that case, I'd want a -3dB corner of about 150Hz.

Second, can the gain be adjusted to match the amp I'll be using for the bass speakers, or is the Rev C's gain fixed?

Peace,
Tom E

[vonfilm]

I will be following this thread closely when my kit arrives.

[madisonears]

Peter or Uriah:

There are two notes written on the PCB itself: one at R42 and one at R2 concerning the values of these resistors. I don't understand their significance, and I wonder how you arrived at the values you supplied in the kit. What is the effect of varying these component values? I am not second guessing you; I just would like to know how you chose these values.

Peace,
Tom E

[ClaveFremen]

Something to read:

R42:
http://www.diyaudio.com/forums/showt...502#post758502

R2:
http://www.diyaudio.com/forums/showt...710#post845710

[schro20]

Originally posted by madisonears
at R2 concerning the values of these resistors. [...] I just would like to know how you chose these values.

The board is exactly the last board layout produced by TP including all the writing on the silk layer. The values of all components are exactly according to the last BOM produced by TP. This includes
that bypass caps were changed from 100nF to 220nF. These are C7/17/18/19/20/21. The silk say 100nF the contents of your parts bag have 220nF for these.

Peter

[Coreyk78]

I'm just thinking about things while I'm bored at work...
I got my kits yesterday but didn't have much time to really look things over yet, but I'm wondering if there are any capacitor locations where it would be worth it to use some boutique caps?

Reason I ask is I have some muse and silmic II caps along with a fair sized collection of Russian PIO caps, K42-Y, K40-Y, and FT-1 teflons. I will probably build it using the standard components first to use as a baseline, but I'm just wondering which caps would be good to bypass or replace if I do some tweaking in the future

[ClaveFremen]

C9, if you you think Silmics or Muses are better than FCs in signal path.

I think so.

So I've already buyed 220uf 35V Silmic II and 220uF 50V Nichicon KZ for this position.

For C9 bypass I'll use a 0.01uF Vishay MKP1837.

[madisonears]

I got 220uf FM's in my kit, not FC's, for C1, C2, C9 and C14. Nice!

Please note that 100nf bypass C7, C17, C18, C19, C20 and C21 have all been changed to 220nf. The silk screen says 100nf, but that's where the AVX 220nf's go now. I would consider upgrading those, at least at C21.

I don't recognize coupling C13 brand. BOM says Kemet MKP, but label on cap says AV. That's probably where you'll get the best return with upgrade. There is plenty of room there and different hole spacing for a variety of cap types.

Peace,
Tom E

[ClaveFremen]

For C13 I've selected Evox-Rifa PHE426, that according to Humblehomemadehifi 's caps test, should be pretty good; it will be bypassed by a Vishay MKP1837 as well.

[schro20]

Originally posted by madisonears
I got 220uf FM's in my kit, not FC's, for C1, C2, C9 and C14. Nice!

Indeed. After originally thinking about getting FCs we realized that FM was better (and we got a better price; wonders happen).

Peter