It's designers privilege to discover amplify music with his creations.
My only work with ready well documented projects and fantasy
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OK... stupid question and i may have missed this in a previous post.
Can you make a DEF work with a depletion n-channel on top and an enhancement mode n-channel on the bottom and phase split and flip the input using a transformer like the F6?
Please don't hit the idiot too hard...
Can you make a DEF work with a depletion n-channel on top and an enhancement mode n-channel on the bottom and phase split and flip the input using a transformer like the F6?
Please don't hit the idiot too hard...
DEF amp with Positive Current Feedback
The simplified schematic is for a prototype DEF amp under subjective study. Please note its salient features:
1. The DEF FET pair operates in the common drain configuration; meaning a follower or power buffer as designed by Mr. Pass.
2. The DEF FET pair was also asked to operate in the common source configuration to give an inverted signal with very low gain across the 0.5 Ohm load tied between ground and the center joint of the 2 PSUs. Voltage gain is ~0.5 divided by Z loudspeaker.
3. The current flowing through the loudspeaker has the same magnitude as that flowing through the 0.5 Ohm resistor..
4. The resultant signal across this 0.5 Ohm sense resistor is the positive current feedback signal Vpcf. It is in phase with the music signal Vin.
5. Both signals are summed, inverted and amplified in the operational line amp [U1]. The contribution of Vpcf in the Vout signal of the OpAmp can be readily calculated.
5. The resistors around this OpAmp give ~ a 3+dB boost or add-on voltage gain to/with Vin.
I'll post the full schematic of this DEF amp. This amp and the loudspeaker gave a unique music signature which is very pleasant.
The simplified schematic is for a prototype DEF amp under subjective study. Please note its salient features:
1. The DEF FET pair operates in the common drain configuration; meaning a follower or power buffer as designed by Mr. Pass.
2. The DEF FET pair was also asked to operate in the common source configuration to give an inverted signal with very low gain across the 0.5 Ohm load tied between ground and the center joint of the 2 PSUs. Voltage gain is ~0.5 divided by Z loudspeaker.
3. The current flowing through the loudspeaker has the same magnitude as that flowing through the 0.5 Ohm resistor..
4. The resultant signal across this 0.5 Ohm sense resistor is the positive current feedback signal Vpcf. It is in phase with the music signal Vin.
5. Both signals are summed, inverted and amplified in the operational line amp [U1]. The contribution of Vpcf in the Vout signal of the OpAmp can be readily calculated.
5. The resistors around this OpAmp give ~ a 3+dB boost or add-on voltage gain to/with Vin.
I'll post the full schematic of this DEF amp. This amp and the loudspeaker gave a unique music signature which is very pleasant.
Attachments
Can the DEF be driven with the BA-3 frontend? Is it enough gain? Will it work with the original schematic?
From article:
From article:
DEF being source follower ....... drive it with anything you have
starting from M2 FE , ending with BA3 FE or whatever
starting from M2 FE , ending with BA3 FE or whatever
Hello. BA3-FE is a current source preamp. It can drive DEF without a coupling cap. But the consequence is that the Vds of its complementary MOSFETS will be unequal. One will loose~ 4Vdc of its Vds and the other will gain ~4Vdc of Vds. This may impact the inherent sonics of BA3-FE.
The schematic in my previous post shows that R4 is the load to U1. It is ~15K in my past schematics. To be used to set the volatage gain of BA3-FE.
You have been experimenting with positive current feedback [PCF] from my read of your posts in the thread of First Watt F7. PCF is expected to be as readily implemented in this combination of BA3-FE//DEF as I showed but with a simpler circuit.
Haha Antoinel if amplifier reproduced sound is very pleasant
what about build nicely one or two extraordinary DEF variants
and then bring your hot new DIY stuff into future Burning Amplifier Festival ?
Congratulations anyway 😀
Thanks Soundhappy for your post and suggestions. Would love to visit a future BA festival, and meet Mr. Pass and all of the attending DIYers.
Someone else did the work for me. I just followed along. It looks easy enough to calculate.
Been thinking, will pcf be more of a regular thing now?
I am extremely late in seeing this interesting thread. I hope this isn't another design requiring unobtainium parts.
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The success of F7 generated enthusiasm among DIYers and caused a revival in the understanding and implementation of positive current feedback [PCF]. For example, DIYer lhquam taught many options to use PCF in the First Watt F7 thread. PCF has and is expected to become more common in diy amps.
PCF has had a definate impact on the way I listen.
I don't think I want to live without that level of driver control. I imagine I'd need an amp with a couple hundred watts of power to get that sense of control.
I don't think I want to live without that level of driver control. I imagine I'd need an amp with a couple hundred watts of power to get that sense of control.
Thanks lhquam. DEF is interesting because it is a very simple design which is highly reliable to implement/operate. I found DEF to be highly enjoyable to experiment with. The SemiSouth SJDP120R085 N-depletion FET and an IRFP-MOSFET are the two basic FETs in DEF. Substitution for R085 is possible by using other available devices; for example UJN1208K. Mr. Pass is expected to write an article on DEF.
I fully agree about the beneficial influence of PCF on the clarity and presence of music. It is readily discernible. I continue to think about using PCF in other diy amps so as to raise their bar of performance.