Changing my old VFA designs into ONE-BEND CFA plus Current Drives - diyAudio
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Old 25th March 2014, 07:11 AM   #1
mtlin12 is offline mtlin12  Taiwan
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Smile Changing my old VFA designs into ONE-BEND CFA plus Current Drives

After my 50W EU-50 (pls. attached diyaudio: Should I call this pre-amp+ PDB a "SPLIF" Amp?),
it has been 7 years I have no any idea about a new VFA design, until I read Wanye Stegall’s
“One-Bend Amplifier” and thought why not changed my old VFA designs into CFA or plus a
Current Drive to become a new SPLIF CFA?

So last month I started to test on my Diamond Buffer Structure DB-01 pre and headphone amp
into DB-1/2 or DB-0.5, but there is no more a diamond buffer, just use two JFET becoming
A simple class-A output buffer but only ~3mA output not enough to be a headphone Amp.


And then I changed several components of my old “EU-01” Pre-& Headphone Amp becoming a
CFA “EU-1/2”, it was named 1/2 ( or HALF )because of no need to use expensive DUAL-JFETs anymore.

In EU-01 & EU-1/2 I use the same diamond buffer to be a current drive of a headphone amp,
To aloud higher current drive, then I’ll try to use my old 0dB amp which was licensed to a local
Audio company “Morkai” , (they built it with a 10dB ITP transformer and named it “IRON-Amp”)

to make it a new 25W SPLIF CFA EU-25 ( now they are seperated).


(Pls. attached diyaudio: transformer coupled amplifiers & How about a Power Follower with an IPT?)

Attached Images
File Type: jpg VFA_DB-01_Pre-Amp.jpg (511.4 KB, 94 views)
File Type: jpg CFA_DB-0.5_Pre-Amp.jpg (514.4 KB, 92 views)
File Type: jpg VFA_EU-01_Pre-Amp.jpg (416.9 KB, 85 views)
File Type: jpg CFA_EU-0.5_Pre-Amp.jpg (400.8 KB, 77 views)
File Type: jpg EU-01_close look.jpg (223.8 KB, 77 views)
File Type: jpg EU-0.5_close look.jpg (393.2 KB, 21 views)
File Type: jpg Iron-Amp IPT+Current Drive.jpg (167.5 KB, 25 views)
File Type: jpg DB-0.5 JFET MC&Pre-Amp_s.jpg (64.7 KB, 58 views)
File Type: jpg EU-0.5 JFET Pre&Headphone Amp_s.jpg (99.0 KB, 62 views)
File Type: jpg EU-25 CFB Pre + 25W-Amp_s.jpg (100.3 KB, 64 views)
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Old 26th March 2014, 01:09 PM   #2
mtlin12 is offline mtlin12  Taiwan
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And here are the EU-0.5 CFB Pre-Amp Sch. vs old EU-01 VFB Pre-Amp's PDFs.

The topology of the CFB is ready,but some of the components maybe still be changed.

I put the CFA with my friend's pga2320 volume controller kit as the remote pre-amp.

The new CFA's S/N ratio and bandwith seem to be better than the VFB, but both my
X-Fi sound card and oscilloscope had been failed around these years,
so there is no RMAA data or picture I can show here. And I don't have a good
ear to tell the sound differents between CFA and VFA.
Attached Images
File Type: jpg EU-0.5+PGA2320.jpg (349.7 KB, 40 views)
Attached Files
File Type: pdf EU-0.5 CFB Pre-Amp_Sch_v1.0.pdf (56.0 KB, 10 views)
File Type: pdf EU-0.5 CFB MOS SHUNT REG._Sch_v1.0.pdf (52.7 KB, 8 views)
File Type: pdf EU-01_MKII_Preamp_v2.1_A_SCH.pdf (45.5 KB, 11 views)
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Last edited by mtlin12; 26th March 2014 at 01:14 PM.
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