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Simple High Performance DC Coupled Class A HPA with sub PPM THD

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#245
Yes, I think 2SK209GR can work. I have not simulated the circuit with it but should be ok. You can always try it while the BF862s are in order. You may like the sound and just leave them in. Main reason I use BF862s is that they sound great and I have many on hand. The spec sheet says either can work.
 
#246
To be honest Morde and X, I might not have enough 2sK's to match enough for both boards out of 20 + pieces. Considering the price of the BF862s from ebay they are certainly cheaper for 50 off.

I guess matching V113-V114 / V133-V134 FQPs wouldn't hurt either? 😉
 
#247
passive420 said:
To be honest Morde and X, I might not have enough 2sK's to match enough for both boards out of 20 + pieces. Considering the price of the BF862s from ebay they are certainly cheaper for 50 off.

I guess matching V113-V114 / V133-V134 FQPs wouldn't hurt either? 😉
Click to expand...

Those 2sk's are sort of old stock Toshiba unobtanium aren't they? It is not absolutely necessary to match the output FQPs but if they came from same tube and you check the Vgs on them and about same range, it should be good. The BF862's ship faster than usual as they are light - maybe 10-12 days in my experience.
 
#250
xrk971 said:
Those 2sk's are sort of old stock Toshiba unobtanium aren't they? It is not absolutely necessary to match the output FQPs but if they came from same tube and you check the Vgs on them and about same range, it should be good. The BF862's ship faster than usual as they are light - maybe 10-12 days in my experience.
Click to expand...

Discontinued but quite good stock at Digi-Key:

2SK209-GR(TE85L,F) Toshiba Semiconductor and Storage | Discrete Semiconductor Products | DigiKey

Mouser has huge stock:

2SK209-GR(TE85L,F) Toshiba | Mouser Finland
 
#251
I am re-auditioning this amp with my DT880-250's. Sounds excellent - the imaging and soundstage are super spacious. The dynamics and clarity outstanding. Makes these cans really shine - so I would say that there is something nice going on here with higher impedance cans. The large voltage swing headroom makes a difference.

Even YouTube tunes sound great...

YouTube

YouTube

YouTube
 
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#252
I finally got around to making an EIC cover plate out of a black piece of polyethylene plastic (organizer tray divider as stock). I basically followed an actual EIC mains cord socket that came with the case for the template. I then installed the 5.5mm barrel jack to allow a clean way to get 12vdc from a wallwart into the amp. You can also see the Xfeed defeat switch on the back.

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#255
Thank you to Jwjarch for taking the latest BOM and splitting it into sections of the breakaway PCB boards that you may or may not want to build. He also included the schematics and stuffing guide diagrams in the same spreadsheets.
I had to remove the 3d renders as the filesixe was too big to upload.

This is very helpful!
 

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#256
Official BOM

Hello Everyone! After a few rounds of editing with X, we have a BOM. A few more additions to X's previous post.

- The BOM has been separated by PCB so you can follow it to build either the
Headphone or Preamp version of this project.
- Parts from Mouser WILL fluctuate in stock. There are already some parts in BOM
that are not in stock. I would have to update it every single day to avoid this.
- That said, if you have ANY questions please post on the thread.
 

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#258
Jwjarch: Right on, man!

I wasn't sure when you were going to have time and I know some people are chomping at the bit to get started. 🙂

For the eBay LDO's just keep looking and I think other vendors may also show up.

These might also work but will require manual setting of the voltage via solder bridge programming,

TPS7A4700 5V 1A Ultra Low Noise Voltage Regulator + Heat Sink - Replace 7805 | eBay

The alterntive negative VR will need replacement of SMT resistors - so not as convenient as a pot. for sure...

TPS7A3301 -15V 1A 16uVrms Ultra Low Noise LDO Negative Voltage Regulator 7915 | eBay
 
#260
Yes, but you would need to add a jumper from one edge to the other to get 3pins to match LM79xx (GND, IN, OUT).

This could similarly be used for positive:
TPS7A4700 Low Noise Power Module RF Audio Board 3V 3.3V 5V 12V 15V 1A Adjustable-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

With a jumper to get pins IN, GND, OUT

The two boards would need a spring clip to be held to the heatsink.

Alternatively, you could mount them off board and have 3 flying leads altogether.
 
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