solderdude
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Post by solderdude on Aug 21, 2013 17:22:54 GMT
When you are using a DCDC converter on the PCB you can use either wallwarts.
Both have about the same power rating.
They do produce common mode garbage but the DCDC converter on the PCB 'blocks' the biggest part of it.
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Post by drymdrum on Aug 21, 2013 20:31:00 GMT
Hi Frans,
thanks for sending board it arrived AOK today and very nice too.
For the time being it's in the project box...pending as I've a handful of woody bits to
have a bash at in the next few weeks.
Regards,
Alan
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Deleted
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Post by Deleted on Aug 24, 2013 21:35:40 GMT
does anyone know where i could buy some self adhesive pcb stand-offs without paying through the nose. tried farnell, but they want £20 min order. tried toby, a dozen cost 96p but nearly a fiver with delivery !  i should have ordered them with the rest of my bits, was an oversight. |
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juke
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Post by juke on Aug 24, 2013 21:54:26 GMT
Ebay seems to have what you want, 4 for a couple of £s, seems a lot for all they are but better than your current choice!
Syd
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Deleted
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Post by Deleted on Aug 24, 2013 22:12:24 GMT
Ebay seems to have what you want, 4 for a couple of £s, seems a lot for all they are but better than your current choice! Syd the only ones i can see on ebay have a 4mm hole requirement. i believe the pcb for filter has 3mm holes. also it seems a waste to buy 25, and i would need to buy a 4mm drill bit to open out the pcb's holes. i may as well go with the "toby" option, i guess. |
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Post by micmacmo on Aug 26, 2013 23:20:50 GMT
Boo-yah, Frans. Boards arrived safe and sound in today's mail. Thanks!
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solderdude
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Post by solderdude on Aug 27, 2013 11:37:52 GMT
Now it's 'just' a matter of populating it (which isn't that difficult) and building it in an enclosure with connectors and switches (which is the more daunting task)
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BMF
contributing
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Post by BMF on Aug 27, 2013 23:44:39 GMT
Frans,
I received my active filter PCBs, today....Thank You.
Now need to decide which ones to build and order the BOMs....hmmmm
Keith
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Post by micmacmo on Aug 30, 2013 4:45:46 GMT
The Pro's of the Page 35 correction filter is only one section is present and that section lowers the 8-10kHz peak. The increase in highs (above 2kHz going up to 50kHz) is 'fixed' to a level BUT if Rx06 is replaced with a 1k potmeter you can increase or decrease the highs lift with the turn of a potmeter. .... Another 'tweak option' might be the sublows/lows that could be increased a bit if so desired. Components that may have to change value is Cx02 and Rx03. For those wanting to experiment here you could insert small sockets for Cx02 and Rx03 to 'play' with values and solder in fixed values when ready. One could do the same for Rx06. Frans, I like the idea of being able to tweak the peaks and shelves. Can I assume that using sockets with swappable transistors will introduce less noise than using a pot? And if so, what alternative values would you recommend for RX03, RX06 and CX02 (which are listed in the page 35 BOM as 5.6 kOhm, 220 Ohm and 1 uF respectively)? Thanks! |
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solderdude
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Post by solderdude on Aug 30, 2013 6:32:58 GMT
potmeters and resistors used in the circuit are all relatively low Ohmic and will have much less contribution (non-existent in real life) compared to the used opamps with the only exceptions being Rx11, Rx14. These are the components that determine the actual noise levels of the circuit.
Alas they must be relatively high resistance in order for the circuit to work.
Rx03 determines the lift of the sub-bass, the HIGHER the value the more sub-bass LIFT. Wouldn't take it beyond 12kOhm (not needed)
Rx06 determines the max lift of the top end, the LOWER the value the more LIFT. Wouldn't make the value smaller than 1/10th of Rx04.
Cx02 determines the FREQUENCY of the lows lift. The LOWER the value the higher the frequency point so if you want more bass you need to use 470nF instead of 1uF. each halving of the value doubles the frequency where the filter starts to have an effect. You may want to alter Rx03 when Cx02 has decreased in value.
For the resistors I would recommend to change Rx03 and Rx06 with small potmeters (10k and 2k respectively) and 'adjust' to your liking.
Use many different types of music to determine the best value.
Then measure the value of the pots and choose a value closest to the one you measured. Doesn't need to be 1%, standard E24 series is more accurate than your ears and differences between even the best matched set of drivers (the hearing works logarithmic)
If you want less highs boost (compared to 220 Ohm) try 270 Ohm and 330 Ohm for instance.
If you want more bass boost try 470nF
If you want more subbass boost replace 5.6k for 8.2k
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Post by micmacmo on Aug 30, 2013 15:00:31 GMT
Thanks for the advice, Frans. I hadn't fully appreciated the exact roles of Rx03, Rx06 and Cx02.
EDIT: Just recalled another question. Is it possible to shift the position of the 8kH notch? If I hear a spike in my T50RP, it's closer to 10kHz.
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Deleted
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Post by Deleted on Sept 2, 2013 18:23:38 GMT
Frans
when fitting the rca connectors , do they need to be isolated from the case?
cheers
Simon
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solderdude
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Post by solderdude on Sept 2, 2013 18:36:36 GMT
Thanks for the advice, Frans. I hadn't fully appreciated the exact roles of Rx03, Rx06 and Cx02. EDIT: Just recalled another question. Is it possible to shift the position of the 8kH notch? If I hear a spike in my T50RP, it's closer to 10kHz. If you want to move the 8kHz point to 9 kHz you will have to lower Rx11 from 56k to 47k If you want it even further at 10kHz you will have to lower Rx11 from 56k to 47k AND also lower Cx04 from 3.3nF to 2.7nF |
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solderdude
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Post by solderdude on Sept 2, 2013 18:37:55 GMT
Frans when fitting the rca connectors , do they need to be isolated from the case? cheers Simon I recommend to tie all 4 of them (or 6 if you plan to use an input selector as well) to ground. |
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Post by micmacmo on Sept 3, 2013 19:12:48 GMT
I've uploaded a complete "shopping list" for the page 35 version of the T50RP filter to Google docs. You can find it here: docs.google.com/file/d/0B_svLQu7hxPtQlJHUzdJTFU5UEk/edit?usp=sharingMy purpose for sharing is two-fold. I'm hoping some kind souls on this forum will review it to make sure I didn't make any newbie mistakes (or overlook any components). And I'm hoping that others will be able to use it for their own builds. While this is a "stock" version of the filter that includes everything but a desktop or wall-wart DC power supply, I've also added a section to the list for optional changes. (I will be using collet sockets to allow for component swapping.) These options include: - Rx03 alternative to modify the amount (dB) of sub-bass lift. - Rx06 alternatives to modify the amount (dB) of top-end lift (dB) - Rx11/Cx04 alternatives to adjust the precise location of the 8-10 kHz notch These mods are outlined in these posts: diyah.boards.net/post/3425/threaddiyah.boards.net/post/3502/threadOtherwise, this version uses the option 4 power supply. It uses a DPDT switch (on and pass-through) with no LEDs. I currently have a 5VDC 3A wall-wart that I'll be using, so it's not on the list. Some specific questions: Because I'm using the recommended DCDC converter, do I need to change anything re: rectifiers? Any particular recommendations for wire? Please let me know if you have any problems downloading the list. |
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