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Old 19th January 2014, 11:46 PM   #71
spind is offline spind  Canada
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Take your time Jason--you've already given us more of your time and effort than most!
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Old 20th January 2014, 02:36 AM   #72
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OK folks,

Starting off I'm posting the 'As Built' schematic with component designators that match the silk on the boards that are shipping / are shipped and a basic Bill Of Materials. Also provided is a drill template. These will be included in a more comprehensive document to come but I'm putting them up individually since they have been explicitly requested.

Also, as an update:

still4given - 2 - Shipped
ivanlukic - 2 - Alternative payment arrangements made, shipping Monday
quan - 2 - Shipped
triplej - 2 - Paid, shipping Monday
baswamin - 2 - Paid, shipping Monday
potepuh - 2 - Paid, shipping Monday
spind - 2 - Paid, shipping Monday
brianco - 2 - Paid, shipping Monday
Sheldon - 2 - Shipped

So, everyone has paid which means I will be shipping out all remaining packages tomorrow.
Attached Files
File Type: pdf JTK-VSSA BOM.pdf (34.4 KB, 510 views)
File Type: pdf VSSA CCS_asbuilt.pdf (35.8 KB, 739 views)
File Type: pdf JTK-VSSA Drill Template.pdf (1.3 KB, 316 views)
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Old 20th January 2014, 01:25 PM   #73
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Jason,

Couple of questions for you based on your schematic.

1. The 2200uF cap does not seem to have a film bypass. Do you think adding film cap will improve sound? or stated other way, absence of film bypass capacitor wont affect the sound?

2. We saw in LC's VSSA modules that removing diode/resistor D3,D4/R16,R19 improved bass. Will this mod work here too? I am thinking a little ahead to tweaks after the build.

Thanks
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Old 20th January 2014, 04:10 PM   #74
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Hi Jason,

Wow, just got a chance to look over the schematic. We are a ways away from the little 6 transistor amp we started with. For those of us who are trying to learn, would you mind explaining what the added circuitry is accomplishing?

Thanks, Terry
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Old 20th January 2014, 04:35 PM   #75
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Quote:
Originally Posted by still4given View Post
Hi Jason,

Wow, just got a chance to look over the schematic. We are a ways away from the little 6 transistor amp we started with. For those of us who are trying to learn, would you mind explaining what the added circuitry is accomplishing?

Thanks, Terry
Terry,

The short version is just the addition of two CCSs (constant current sources) to feed current to the front end and a VBE multiplier (amplified diode) in place of the diode string for output biasing. Each CCS adds two devices and the VBE adds one more for a total of five small signal devices added as supporting components. The 'core' is still the six transistor circuit.

PMI's version used JFETs for the CCSs and diodes for bias. LazyCats official offering used JFETs for CCSs as well and an IC (band gap reference IIRC) to yield adjustable bias. This is a deviation from Shaan's PeeCeeBee but closer to LazyCat's vision and IMHO still a valid VSSA version. This is why we are here on this thread and not on the PeeCeeBee thread, we are no longer compliant with Shaan's vision and it didn't seem appropriate in LC's thread since that is considered a commercial venture now.

If there are any questions I'll try to address them later tonight.
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Old 20th January 2014, 04:44 PM   #76
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Last update, at least until we see packages arriving to their destinations:

still4given - 2 - Shipped
ivanlukic - 2 - Shipped
quan - 2 - Shipped
triplej - 2 - Shipped
baswamin - 2 - Shipped
potepuh - 2 - Shipped
spind - 2 - Shipped
brianco - 2 - Shipped
Sheldon - 2 - Shipped

All were shipped out via post this morning. Some destinations may take some time to arrive, others will be quicker. Please, please let me know when they have arrived. Thanks everyone. I will continue to work on documentation, but the basics are already posted and that should get everyone started.
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Old 20th January 2014, 04:48 PM   #77
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Hi Jason,

Thanks for the explanation. I wasn't questioning your motives, just trying to learn. Seems this thread is the perfect place for this. I think that is what PMI had in mind when he started this thread.

Thanks again, Terry
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Old 20th January 2014, 08:36 PM   #78
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Quote:
Originally Posted by baswamin View Post
Jason,

Couple of questions for you based on your schematic.

1. The 2200uF cap does not seem to have a film bypass. Do you think adding film cap will improve sound? or stated other way, absence of film bypass capacitor wont affect the sound?

2. We saw in LC's VSSA modules that removing diode/resistor D3,D4/R16,R19 improved bass. Will this mod work here too? I am thinking a little ahead to tweaks after the build.

Thanks
baswamin,

1) I initially began the layout with the option to do film bypasses for the feedback capacitors but began making too many compromises in the layout to leave them on. My initial builds don't have any feedback bypassing and I didn't feel they suffered to be without them. This layout does not accommodate added bypassing, but I don't think it will make any significant difference. Opinions will vary.

2) The VSSA likes a clean and quiet power supply, especially for the IPS and VAS. For anyone who builds with a basic bulk or CRC supply the Ds and Rs are of benefit, they help filter some of the ripple from the mail supply. If you use a good capacitance multiplier supply or SMPS then you could install jumpers instead if you so desired. I'm not 100% sold on the improved bass, but this is DIY, so if you want to try it for yourself I'd love to hear what your opinion is.

In the end, you have a working circuit to start with you can tweak as you see fit. If you find some modification that yields a real improvement then by all means share it so we can all benefit.

Jason
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Old 20th January 2014, 09:56 PM   #79
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thanks for posting so promptly Jason.

Schematic looks good. All variations to the original are based on solid technical reasons and easily reverted if one chooses.
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Old 20th January 2014, 10:30 PM   #80
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Quote:
Originally Posted by still4given View Post
Hi Jason,

Thanks for the explanation. I wasn't questioning your motives, just trying to learn. Seems this thread is the perfect place for this. I think that is what PMI had in mind when he started this thread.

Thanks again, Terry
Oh, no I didn't think that at all. I was just pointing out that for the more 'evolved' VSSA that the CCSs are the norm and not the exception. I just incorporated a different type of CCS, mainly because I'm not fond of JFETS if only for the limited Vds ratings and poorer availability.

It's all about exploring and tweaking as we go. There aren't any major changes, just some subtle 'choices' in implementation.
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