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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm

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pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
sanjeev said:
BTW I wanted to mention my past experiences, to provide some context for my comments above.

In the late '90s and early 00's I got interested in stereo and tried a few different types of equipment, including: (a) entry-level SimAudio integrated (b) Bottlehead tube amp (c) Tube pre and power amp (Tube Audio Design TAD150 pre + TAD 60 EL34 amp) (d) Gain clone (e) Audio Gd power amp. (f) a few dacs and transports.

Tried a few speakers, including 3 well-regarded DIY kits (Dennis Murphy, John Kreskovsky, and Selah Audio).

In 2009 settled on John K's open baffle speakers + Audio GD electronics and lived with it for over a decade.

With kids in high school or college, I had more time again and get interested in upgrading in 2019, and this Folsom amp is (hopefully) the last step.
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Hi Sanjeev,

Glad you like the amp and also big thanks to Destroyer OS for such good amp and support!

You should know that in audio, there's never a last step... ;)

All the best!
Do
 
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faithintruth

Member
Joined 2012
Hi Pinnoccio

Great build of the 7293. I'm about to build my first chip amp which is the same amp from Jeremy. Could you support my build if I had any questions or needed pointers? I have built with tubes but I'm still learning.
Could you describe the selection of the input cap? How do I decide on that?

Best regards
Sean
 
pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
Hi Sean,

I can certainly help you on this thread. Please ask all your questions here and DestroyerOS can help you with the build. I will also answer what I can answer no problem.

As for the input caps, I've installed the blue Rifa (Kemet) part F426FG335J250C, on Sanjeev's amplifier. Their really good caps. If you can find the place, you can use the CDE 940C, but they're just too bulky I found for this tiny PCB.

Do
 
Destroyer OS

Destroyer OS

Member
Joined 2005
Yes, some caps are pretty big for it. Another one I like is Polycarbonates but availability is tricky as I know know one place still making them, and sometimes they're on eBay in higher values but $28+ a piece I think. They would also be large.

I made some provisions for larger caps but it's up to the user to figure out how they're going to adapt them.
 
V

vilding

Member
Joined 2020
This is how it looks with a Mundorf M-cap Supreme just casually hanging off the board...
 

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V

vilding

Member
Joined 2020
faithintruth said:
I can see things in Stockholm seem casual.
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:p:p Not as much as people seem to think, though... We have a lot of restrictions and travel bans and so on, but yeah, we can leave home.

On the cap side, I just slapped it on my almost empty boards for visual comparison, so I couldn't say. But I've used them in a pair of speakers before, and they sounded very transparent, fast and clear without any romanticism to the sound. The Jantzens at around the same price sounded a little warmer but equally good. Of course you could pay a lot more and maybe squeese out a few % in
performance, but for me I think at ~15-20£/unit, that's my pain threshold as far as deminishing returns are concerned. I wouldn't pay the price, or more, of the rest of the amp (or speakers) in caps only. Take my findings with a grain of salt as my basis of comparison isn't that big when it comes to high end caps and no science, only ears and emotion, was involved in testing... :)

/Hilding
 
C

ciphercomplete

Member
Joined 2012
I love Jantzens. I have the Superiors and Silver Z-caps in my speaker crossovers. I had some Flat Stack Jupiter aluminum caps that just happened to be 2.2uf laying around and I have those on my amp boards right now but I think I am going to replace them with the Jantzen Alumen z-caps in the final version of my amps.
 
V

vilding

Member
Joined 2020
manniraj said:
Check out Mark Johnson suggestion of using a simple diode like 1N4148 in series with the hot side and a resistor like 470 ohm in series with the other leg of the LED connected to your AC secondary windings should give you a simple solution of front panel LED. I think his suggestion with some photos are listed in one of the thread of Pass Labs forum section.
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Did anyone find the thread or made the circuit? It would be nice to have on store, as clearly and easily as possible... :D
For this one, I think the gentle internal glow will be enough as a power indicator, but for future builds, it would certainly be nice to have a good go-to-ciruit.

/Hilding
 
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