DIY Amps for NX-Oticas

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mkrawcz

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Re: DIY Amps for NX-Oticas
« Reply #100 on: 21 May 2021, 01:50 pm »
I finally got around to building a Folsom EC7293. I initially used a pair of cheap Kemet film caps for the input cap and it sounded good. I changed those out to VCAP ODAMs and now this amp sings.




Jaytor

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Re: DIY Amps for NX-Oticas
« Reply #101 on: 21 May 2021, 02:10 pm »
Very nice!

AKLegal

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Re: DIY Amps for NX-Oticas
« Reply #102 on: 21 May 2021, 02:45 pm »
Yeah, that is excellent work. I have one of those new, smaller soft start boards from Neurochrome that I plan on using for a preamp project. They are so much easier to fit into a chassis than those huge old ones lol.

My Mod186 monos have been in my system for months, I am going to switch out for my Folsom for a while.

mkrawcz

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Re: DIY Amps for NX-Oticas
« Reply #103 on: 21 May 2021, 03:37 pm »
Yeah, that is excellent work. I have one of those new, smaller soft start boards from Neurochrome that I plan on using for a preamp project. They are so much easier to fit into a chassis than those huge old ones lol.
Tom's ISS board is worth every penny. I will not build an amp without it. I will probably end up drilling out a hole for a trigger jack and use that feature of the board as well.

Jaytor

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Re: DIY Amps for NX-Oticas
« Reply #104 on: 21 May 2021, 03:51 pm »
Tom's ISS board is worth every penny. I will not build an amp without it. I will probably end up drilling out a hole for a trigger jack and use that feature of the board as well.

I agree - nice design. I'm using it in my new preamp build. This one uses a separate power supply chassis.



I have four unregulated +/- supplies (two for each channel) that feed different parts of the preamp, plus a regulated digital supply for the input selector and stepped attenuator control/display. The unregulated supplies will feed shunt regulators that are mounted in the main chassis close to to circuit boards they power. I've been building the boards for the main chassis, but haven't started putting everything together yet. A 14 conductor umbilical cord delivers the DC power to the main chassis.

Early B.

Re: DIY Amps for NX-Oticas
« Reply #105 on: 21 May 2021, 04:04 pm »
This thread is awesome!

mkrawcz

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Re: DIY Amps for NX-Oticas
« Reply #106 on: 25 May 2021, 11:33 pm »
My Mod186 monos have been in my system for months, I am going to switch out for my Folsom for a while.
All I have to say after a week of break in is the Folsom amp is awesome.

sarora9

Re: DIY Amps for NX-Oticas
« Reply #107 on: 26 May 2021, 01:07 am »
mkrawcz, how does it compare to your other amps? Very curious. (I have a Folsom 7293 too and v. happy with it.)

mkrawcz

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Re: DIY Amps for NX-Oticas
« Reply #108 on: 26 May 2021, 01:25 am »
mkrawcz, how does it compare to your other amps? Very curious. (I have a Folsom 7293 too and v. happy with it.)
It’s subjective, but I think it beats the Neurochrome and the Elekit. I haven’t tried comparing it to my BHKs yet, but it might be pretty close. The dynamics and soundstage are right up there. I have some Audio Note caps coming tomorrow to try for the feedback cap to see if there is anymore to be gained.

sarora9

Re: DIY Amps for NX-Oticas
« Reply #109 on: 26 May 2021, 01:40 am »
OK that's pretty high praise. I have not heard neurochrome or Elekit myself but have read the praise for them.

Waiting to hear about your experiment with the capacitor; the one in mine is good but not an expensive one

sarora9

Re: DIY Amps for NX-Oticas
« Reply #110 on: 26 May 2021, 01:41 am »
(deleted duplicate post)

tull skull

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Re: DIY Amps for NX-Oticas
« Reply #111 on: 27 May 2021, 04:14 am »
Guys I know this is a little bit from left field and also a little bit under your skill level but your discussion prompted curiosity to know if you have had any exposure/experience with the Akitika kit? Thanks for your time.:)

mkrawcz

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Re: DIY Amps for NX-Oticas
« Reply #112 on: 28 May 2021, 10:16 pm »
OK that's pretty high praise. I have not heard neurochrome or Elekit myself but have read the praise for them.

Waiting to hear about your experiment with the capacitor; the one in mine is good but not an expensive one
I changed out the feedback cap at C3 from a Nichicon ES to an Audio Note standard foil and it completely changed the amp. Before, the amp had this lower mid bloom that was not right, the soundstage was smeared, and the sound was slightly veiled. The new cap changed everything and this amp is amazing. My BHKs probably have it beat in dynamics, but the Folsom is at least as good with the soundstage and clarity. The soundstage may even be a little better. Considering what it cost to build this amp, its untouchable.

AKLegal

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Re: DIY Amps for NX-Oticas
« Reply #113 on: 30 May 2021, 01:34 am »
I changed out the feedback cap at C3 from a Nichicon ES to an Audio Note standard foil and it completely changed the amp. Before, the amp had this lower mid bloom that was not right, the soundstage was smeared, and the sound was slightly veiled. The new cap changed everything and this amp is amazing. My BHKs probably have it beat in dynamics, but the Folsom is at least as good with the soundstage and clarity. The soundstage may even be a little better. Considering what it cost to build this amp, its untouchable.

I got the impression from Jeremy that the choice of feedback caps wasn't a big deal (I might be misremembering). Those Audionotes are cheap enough to try. Unfortunately I mounted the amp boards on the heatsink instead of on the baseplate like yours. Switching that cap will be a half a days work for me lol.

I don't hear the same issues with the soundstage or with the mid bass as you did though. Even on comparison to my Neurochrome amps. I have a pair of Jantzen Silvers on the input.  I had a pair of Flat stack Jupiters on there first but I found them a bit too smooth, laid back and lacking detail.  I can't remember which Nichicon I used for C3 but I know I didn't use the same green ES version you did. The only thing I remember for sure is that they were 1000uf if that matters at all.

mkrawcz

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Re: DIY Amps for NX-Oticas
« Reply #114 on: 30 May 2021, 01:55 am »
The Nichicon ES is easy to spot. It’s bright green. If yours is gold it’s probably a KZ and that cap is probably a lot better. Jeremy has been recommending the Rubycon ZL which I think is a similar cap to the Audio Note. I think Rubicon actually designed the Audio Note. The feedback cap definitely makes a big difference. That’s why he left it up to the builder to pick one instead of including it in the BOM.  My regret was not soldiering in a socket header for easy cap swapping.

RonP

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Re: DIY Amps for NX-Oticas
« Reply #115 on: 13 Jun 2021, 09:25 pm »
I had some Folsom 7293's built into mono-blocks by pinnocchio over at diyaudio forum's. He did a fantastic job and answered my 9 million dumb emails along the way. A really top notch build.

I only have a few hours of listening on them right now but quite like them.

A few highlights
- XLR in
- Quality Caps and wiring
- Soft Start

He links to the build thread here https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm-post6657513.html (you'll probably want the English translation in the very next post)

He gives a summary of his listening impressions on the bottom of the next page https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm-post6672922.html

Here are a few pics installed here in TX. I had to order another Amp Stand from Butcher Block Acoustics.












 :popcorn:

(Those are the tape lines on my carpet from LOTS https://www.youtube.com/watch?v=CyTkwkK8ON0
and some cheap yoga blocks https://www.amazon.com/Gaiam-Yoga-Block-Supportive-Latex-Free/dp/B00LY9O83G/ref=pd_bxgy_img_2/134-6843275-0604568?_encoding=UTF8&pd_rd_i=B00LY9O83G&pd_rd_r=3a255a5d-e97a-4c6b-9d74-9c8435b82851&pd_rd_w=jx0GQ&pd_rd_wg=tfnYL&pf_rd_p=fd3ebcd0-c1a2-44cf-aba2-bbf4810b3732&pf_rd_r=YHWNCDB2PJ06AM5ZFYX3&psc=1&refRID=YHWNCDB2PJ06AM5ZFYX3 I'm using to get the speaker cables off the floor)

AKLegal

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Re: DIY Amps for NX-Oticas
« Reply #116 on: 13 Jun 2021, 11:14 pm »
Those are solid RonP. I am using those same Neurochrome buffers in my preamp build which is currently mounted to a sheet of mdf. The buffers are extremely transparent.

Jaytor

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Re: DIY Amps for NX-Oticas
« Reply #117 on: 13 Jun 2021, 11:43 pm »
@RonP - Very nice build. I bet those sound great. I love the Toroidy transformers. I've used them in my last couple builds.

Did you consider using an input transformer instead of the Neurochrome buffer and input cap?


RonP

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Re: DIY Amps for NX-Oticas
« Reply #118 on: 14 Jun 2021, 12:42 am »
thanks guys!



Did you consider using an input transformer instead of the Neurochrome buffer and input cap?

It never dawned on me. We could have used your VTV board and popped a tube on there. oooh la la

Jaytor

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Re: DIY Amps for NX-Oticas
« Reply #119 on: 14 Jun 2021, 03:43 am »
I think the advantage of the approach you took is that it is less suspectable to larger DC offset which can saturate a transformer. Downside is higher cost. Of course each approach will also sound a bit different. I'm using Miflex caps as high pass filtering caps between my preamp and amps and they sound great.