Has anyone built this amp from the BuildAudioAmps site?Project 61 – BuildAudioAmps. It uses 2SA992 transistors that are hard to find.Could I use the MPSa56 transistors instead that were used in the original blamless design?
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The circuit also has touches of JLH,s designs apart from different feedback philosophy .
Click on -
2sa1085 - Search Results | Farnell UK
Gets you 2SA992, I replaced them with =2SA1085 in a JLH design --which are higher spec. including low noise but typical industry -obsolete ,its all going SMD .
Output noise was very low when I tested them in-situ .
Also-
Transistor Base Numbers 2Sxxxx to 2SBxxxx | Cricklewood Electronics
Click on -
2sa1085 - Search Results | Farnell UK
Gets you 2SA992, I replaced them with =2SA1085 in a JLH design --which are higher spec. including low noise but typical industry -obsolete ,its all going SMD .
Output noise was very low when I tested them in-situ .
Also-
Transistor Base Numbers 2Sxxxx to 2SBxxxx | Cricklewood Electronics
Search also for KSA992, equivalent to 2SA992, ditto KSC1845/2SC1845 NPN's
[ BTW this is a classic Doug Self Blameless circuit, with CFP outputs and two-pole compensation - don't think its JLH related ]
[ BTW this is a classic Doug Self Blameless circuit, with CFP outputs and two-pole compensation - don't think its JLH related ]
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I did say it has touches of JLH and I did say different feedback=compensation .
John put his where the slew rate was not affected
John put his where the slew rate was not affected
Thanks.
The design,according to the article is a combination of The Doug Self Blameless Amp and a Randy Slone design.Has anyone had any experience of building designs from this site:Building Audio Amps.I just came across it the other day.They have over 60 audio related projects with board layouts and component listings but unfortunately no forum.
The design,according to the article is a combination of The Doug Self Blameless Amp and a Randy Slone design.Has anyone had any experience of building designs from this site:Building Audio Amps.I just came across it the other day.They have over 60 audio related projects with board layouts and component listings but unfortunately no forum.
Hi Lawrence, I have started a Youtube channel with educational videos which may be helpful to you. I cover there the 2 stage amplifier, the so called Blameless Amplifier.
Check them out at:
SW Audio
YouTube
Regarding your amp in the picture, not a big fan of the CFP output stage when you have more than one output pair. I would change it to an Emitter Follower, preferentially a type II.
Best, Sandro
Check them out at:
SW Audio
YouTube
Regarding your amp in the picture, not a big fan of the CFP output stage when you have more than one output pair. I would change it to an Emitter Follower, preferentially a type II.
Best, Sandro
Mouser has over 50,000 KSA992 in different lead outs - all TO92 package by On Semi.
Sandro great to hear about your You Tube channel.I've been looking for something like this for ages.Just started from the beginning and have subscribed.Are you currently working on an audio project?
Many Thanks
Lawrence
Member
Joined 2009
Paid Member
Nice amp Lawrence,
LTP input with CFP output - maybe check out the P3A thread for additional ideas on parts etc.
P3A Comparison table ( long .... )
I made something with a Singleton input, TGM8, which is perhaps, another thing that JLH liked to use but your amp already looks close to optimal. In my amp I also used two output pair but in a Class C mode for the 2nd pair.
LTP input with CFP output - maybe check out the P3A thread for additional ideas on parts etc.
P3A Comparison table ( long .... )
I made something with a Singleton input, TGM8, which is perhaps, another thing that JLH liked to use but your amp already looks close to optimal. In my amp I also used two output pair but in a Class C mode for the 2nd pair.
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Hi Lawerece, the series has a companion design project, the SW_VFA_01. The letters are nothing creative, VFA: Voltage feedback Amp, 01: It is the first of the series.
Best, Sandro
I like “blameless” style.
However, for the blameless VAS, you should add some current protection for base-emitter of the bottom transistor.
However, for the blameless VAS, you should add some current protection for base-emitter of the bottom transistor.
For transistors, if voltage is not high, BC556..BC560 series is a good choice. For high voltage amp, I use 2n5401. I Just give example for pnp here, you can find the related npn by yourself. Note that they have different pin out. It may not be a drop in replacement.
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Due to advancement the original replacement for the 2SA992 at the time was the 2SA1085 ,this BJT was used by many when it came out.
Whether you can get genuine replacements is another thing in 2021.
Whether you can get genuine replacements is another thing in 2021.