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AD797 Phono Stage Build and Help Desk Thread

GreatTone said:
I used this Hammond enclosure, which was big enough to work in, but not too big:

http://angela.com/hammonddiecastaluminum739x472x206enclosure1590d.aspx

It's 7.39" x 4.72" x 2.06" -- it's pretty plain aluminum, but works for me. I do kind of like that other case with the top that bends over the sides. Seems like it would provide easy access.
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For anyone looking to build inside a Hammond cast aluminum (1590 style) enclosure, try pedalpartsplus.com for a HUGE variety of finishing options at very inexpensive prices.
 
sachu888 said:
I suggest everyone to try Russion PETP K73-16 caps.Tey are inexpensive and will outperform most of the exotic caps.They are available here http://www.ebay.com/itm/2-2uF-63V-P...642?pt=LH_DefaultDomain_0&hash=item5d3011027a
I have no affiliation with the seller just a happy customer.I have suggested these caps to few members and they all have found vast improvement over Wima's or Panasonic.There is a good read here abut these caps http://www.diyaudio.com/forums/parts/143675-petp-capacitors-one-best.html

Regards,
Sachin
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Hi, I'm curious about the voltage, it's only 63 volts, there are other K73 PETP's available at larger voltages, any thoughts?

http://www.ebay.com/itm/2-2uF-160V-...pt=Vintage_Electronics_R2&hash=item2eb8138ee8
 
Mind you that I have never been one to get heavily into capacitor swapping and whatever "sound" they may or may not impart...but the mention of these Russian caps got me curious so I did a little research. It seems that PETP is polyester. The WIMA caps specified for this project are polypropylene, which are pretty widely accepted to be superior in audio applications. Some folks on the audio internet like the PETPs, others say they aren't very good. YMMV.

Like I said, I have no experience with these caps, and have never specifically compared polyester vs polypropylene, but just thought I would throw this out there.
 
GreatTone said:
Mind you that I have never been one to get heavily into capacitor swapping and whatever "sound" they may or may not impart...but the mention of these Russian caps got me curious so I did a little research. It seems that PETP is polyester. The WIMA caps specified for this project are polypropylene, which are pretty widely accepted to be superior in audio applications. Some folks on the audio internet like the PETPs, others say they aren't very good. YMMV.

Like I said, I have no experience with these caps, and have never specifically compared polyester vs polypropylene, but just thought I would throw this out there.
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I noticed the same thing, it would be good to have a side by side comparison as maybe they are constructed differently.
 
HypnoToad said:
I noticed the same thing, it would be good to have a side by side comparison as maybe they are constructed differently.
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Yes, I stumbled onto an old internet thread where the subject was being debated hotly. Some were swearing by the PETP, others were appalled that they let it into their house, much less their stereo. At one point, someone mentioned the MKP as though it were a dirty word. Ehh...I'm happy with my 797 phono stage with the 2.2uF WIMA MKP10s -- sounds quite fine to me.

One thing I have been noticing...it's so revealing that it has forced me to make some very minute adjustments to my VTA/anti-skating. Less than half a mm of VTA made an audible difference I don't think I could have detected before.
 
G'day all, capacitors, I've happily used ordinary MKT's in phono preamp applications with fine results although recently as I detailed in this thread I've been quite impressed by WIMA capacitors in this loading application. http://www.audiokarma.org/forums/showthread.php?t=504630

It is all a bit mysterious but the WIMA's (with a polypropylene dielectric), sure sound lovely compared to the ceramic capacitors for some reason. :yes: Regards, Felix aka catman.
 
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I have read only good reviews about PETP caps from the people who actually used it.I was also not comfortable using them in my B1 when first 1more suggested these tho me.They made a good improvement over stock Axon caps.I will try them in SSP when I build it.Ak member Murli using it in SSP and they are performing way better than Panasonic 2.2uf.They may be some kind of Polyester but made under military specifications.My suggestion is try it to believe it.

Regards,
Sachin
 
I've finished stuffing the board and contemplating a temporary mock-up while I decide the final casing. I have a couple LOMC carts on-hand to try thru it for gain and SQ. I need enuff quiet gain to work with a passive controller if possible.
 
Which carts? I'm running 1.2K ohms gain for a .2mV cart with no noise, but not into a passive. You can probably push it further.
 
jimreeves said:
Which carts? I'm running 1.2K ohms gain for a .2mV cart with no noise, but not into a passive. You can probably push it further.
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An LOMC DL-103M and a VLOMC/lo-'Z' O'fon MC20MkII, The O'fon recommends a 10^ loading FWIW. I'm pre-setting FB at 1.5k for both.
 
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Pio1980 said:
An LOMc DL-103M and a VLOMC/lo-'Z' O'fon MC20MkII, The O'fon recommends a 10^ loading FWIW. I'm pre-setting FB at 1.5k for both.
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I'd be curious to know if you get any phono stage noise at 1.5K. I started mine at 1K for a 0.3mV cart and it was a tad low. I upped it to I believe 1.25K. It could stand a tiny bit more gain, but right now it is as close to CD quiet as a phono stage can be, IME. So I'd be interested in learning if it can be pushed higher without detriment.

PS: I think you'll like this phono stage. It's done some amazing things for my system. However, it's so revealing it's caused me to go back and tweak my VTA and anti-skate, because if they are at all off, it's audible and irritating. Now that they're dialed in...wow.
 
Related question: what is the effect of changing the load resistance? For my AT33EV, I set the impedance at 100 and went with it. But I just read an article about this cart where the writer says he preferred it at 200 ohms. I confess I don't like too much fiddling and experimenting, and would rather just set and forget. But am I missing something here by not increasing the load? Exactly what effect does changing it have? Thanks.
 
Often the cart will sound brighter and less meaty at higher resistance. I recall reading that raising the resistance is actually lowering the load, so raising it would lower the amount of electrical damping.
 
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