Grounding Scheme
I'm having a little trouble understanding the grounding scheme needed for the F5 board. Here's what I'm currently thinking. (Note, I'll be using a centre tapped transformer.)
Reasoning:
The largest currents are seen at the transformer, then at the PS, then the output, then the input. These should be kept separate other than at one point, but if they have to be combined, combine only a lower current ground to the next highest current ground.
Connections:
SG = "star ground point on chassis"
1) AC ground pin to SG
2) Centre tap of transformer to SG
3) common rail of PS board (first cap) to SG
4) first ground point on F5 board to input RCA "-"
5) second ground point on F5 board to common rail of PS (last cap)
6) speaker output "-" to common rail of PS (last cap)
Questions:
A) Is it a better idea to run the common rail of the PSU board to the Centre Tap of the transformer or directly to the SG? (Or will it make a difference?)
B) Is there a better place to connect the speaker "-"? Direct to SG?
C) Have I made any other stupid mistakes?
thanks in advance,
-j
I'm having a little trouble understanding the grounding scheme needed for the F5 board. Here's what I'm currently thinking. (Note, I'll be using a centre tapped transformer.)
Reasoning:
The largest currents are seen at the transformer, then at the PS, then the output, then the input. These should be kept separate other than at one point, but if they have to be combined, combine only a lower current ground to the next highest current ground.
Connections:
SG = "star ground point on chassis"
1) AC ground pin to SG
2) Centre tap of transformer to SG
3) common rail of PS board (first cap) to SG
4) first ground point on F5 board to input RCA "-"
5) second ground point on F5 board to common rail of PS (last cap)
6) speaker output "-" to common rail of PS (last cap)
Questions:
A) Is it a better idea to run the common rail of the PSU board to the Centre Tap of the transformer or directly to the SG? (Or will it make a difference?)
B) Is there a better place to connect the speaker "-"? Direct to SG?
C) Have I made any other stupid mistakes?
thanks in advance,
-j
MUR1540 a good choice?
Peter and any others,
I know the MUR860 has a good reputation, and though it seems slightly lower in rating than Mr. Pass specified for the F5, would the 1540 make a good substitute?
Or is the 3 Amps difference (4 x 8 versus 35) too small to make a difference?
Thanks,
Rick McInnis
Peter and any others,
I know the MUR860 has a good reputation, and though it seems slightly lower in rating than Mr. Pass specified for the F5, would the 1540 make a good substitute?
Or is the 3 Amps difference (4 x 8 versus 35) too small to make a difference?
Thanks,
Rick McInnis
I've had very good experiences with MUR1560 from Digikey (MUR1560GOS-ND). They have worked well in a couple of DIY Aleph30's.
Data sheet: http://www.onsemi.com/pub_link/Collateral/MUR1520-D.PDF
-David
Data sheet: http://www.onsemi.com/pub_link/Collateral/MUR1520-D.PDF
-David
Good question back up there on the grounding.
What I intend to do is make a heavy copper tie between the 2 speaker "-" terminals. That effectively becomes my star ground.
To that point I run wires from (1) ground of input RCAs; (2) ground points on F5 boards (3) tie all ground points together on PS boards and run 1 wire to the grounding point.
Contruct a breaker consisting of 2 diodes back to back, in parallel with a 10R power resistor and a 0.001-0.01uF cap. Connect one side of this to the ground point and the other side to chassis (safety) ground.
Am I right in this?
Fran
What I intend to do is make a heavy copper tie between the 2 speaker "-" terminals. That effectively becomes my star ground.
To that point I run wires from (1) ground of input RCAs; (2) ground points on F5 boards (3) tie all ground points together on PS boards and run 1 wire to the grounding point.
Contruct a breaker consisting of 2 diodes back to back, in parallel with a 10R power resistor and a 0.001-0.01uF cap. Connect one side of this to the ground point and the other side to chassis (safety) ground.
Am I right in this?
Fran
Re: PSU for F5
PSU boards are most likely still available.
As noted earlier on this page, for a dual mono configuration, 300VA 2x18V toroidal transformers are recommended. Unfortunately, it's hard to say which transformers are available in your part of the world, so look around and see what you find. (They are generally not shipped too far because they are both heavy and relatively easy to make.)
If you're wondering how much capacitance to put in a dual mono power supply, Mr. Pass uses 60,000uF per supply rail in his stereo production model. You could go lower or higher and it wouldn't make much difference, but more is considered better and capacitors are cheap.
Each F5 board is split in half and each half is good for one mono channel, so you will need one F5 board. Each PSU board _can be split in half for different circuits, but should not be for the F5. For mono operation, you will need two PSU boards.
Read the rest of this thread and the other F5 thread - there is a lot of useful information available if you take the time to sort through it.
-j
Pocoyo said:
Pocoyo said:
PSU boards are most likely still available.
As noted earlier on this page, for a dual mono configuration, 300VA 2x18V toroidal transformers are recommended. Unfortunately, it's hard to say which transformers are available in your part of the world, so look around and see what you find. (They are generally not shipped too far because they are both heavy and relatively easy to make.)
If you're wondering how much capacitance to put in a dual mono power supply, Mr. Pass uses 60,000uF per supply rail in his stereo production model. You could go lower or higher and it wouldn't make much difference, but more is considered better and capacitors are cheap.
Each F5 board is split in half and each half is good for one mono channel, so you will need one F5 board. Each PSU board _can be split in half for different circuits, but should not be for the F5. For mono operation, you will need two PSU boards.
Read the rest of this thread and the other F5 thread - there is a lot of useful information available if you take the time to sort through it.
-j
Re: Correct sizes of heatsinks
Hi, I'm a first time diy- er - Yes a Newbe ! I will be building a F3, F4, F5, & Aleph 30,........ One at a time ! I need to find the correct size heatsinks & it would be nice to pick them up all at once, what size do I need - is there an easy way to figure this out.... Thanks for any advice ! dean
Hi, I'm a first time diy- er - Yes a Newbe ! I will be building a F3, F4, F5, & Aleph 30,........ One at a time ! I need to find the correct size heatsinks & it would be nice to pick them up all at once, what size do I need - is there an easy way to figure this out.... Thanks for any advice ! dean
orthoefer said:
I tried Jensens tonight and they work fine, no heat issues at all.
They sound more relaxed and delicate, almost velvety comparing to Sikorels. I cut the traces on PS board to implement 4 pole feature. A small engraver and a blade works well for that purpose.
I have them with MUR3060 diodes, first cap is 15,000/63, the second 10,000/63, with two Mills 0.22/5W in parallel per side. The resistors are only warm.
While originally the amp sounded bright, I'm not getting that impression any more.
Attachments
Peter Daniel said:
Peter, thanks for doing all your tests and reporting the results. Any reason you selected 15,000 and 10,000 mfd as opposed to 2 15,000 mfd caps? At the moment I am a little floored by the cost of Jensen caps, especially for dual mono aps (8 x $50). Any suggestions for sources of Jensen caps? Thanks.
You van also get Jensens from Partsconnexion or from here: http://www.referenceaudiomods.com/M...creen=CTGY&Store_Code=RAM&Category_Code=JE4PA
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