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Post by Deleted on Jun 2, 2011 23:24:49 GMT
Typical Alex, somebody always has to spoil my achievements, I can't even be last Syd
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Post by Deleted on Jun 3, 2011 10:54:42 GMT
I'm preparing an order for the bits I don't have. Unfortunately 79L15 is no longer stocked at Farnell or RS, ebay search didn't help. Any ideas please?
Is this still the right part if using 20v traffo? (Its a while since I read all of the thread so this might be a daft question!
thanks
Syd
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Post by Deleted on Jun 3, 2011 11:30:03 GMT
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Post by Deleted on Jun 3, 2011 12:12:35 GMT
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Post by Deleted on Jun 3, 2011 12:51:12 GMT
Thanks Alex and Chris. I used Jon's BOM reference at Farnell which gave 'no longer stocked'. I tried RS with the same result. I then searched obviously leaving in too much info, so now sorted with some with slightly different letters. Next query! Also on the list is Film Capacitor, polystyrene, 68pf 5mm pitch but the reference brings up an axial style. Looking elsewhere that's what comes up too. At over £1 each I don't want to get that one wrong! Will these be OK? More to come no doubt, thanks Syd
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jonclancy
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Post by jonclancy on Jun 3, 2011 14:18:56 GMT
I went for 68pf polyprops...
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Post by Deleted on Jun 3, 2011 14:43:48 GMT
Yep, I used axial polystyrene.
If you look at the posted pics of builds you'll see either the polyprops like Jon used or the Axial polystyrenes which can be tombstoned or laid flat with their legs bent inwards (oooh matron!)
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FritzS
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Post by FritzS on Jun 3, 2011 15:25:04 GMT
I'm preparing an order for the bits I don't have. Unfortunately 79L15 is no longer stocked at Farnell or RS, ebay search didn't help. Any ideas please? Is this still the right part if using 20v traffo? (Its a while since I read all of the thread so this might be a daft question! My status ... I am not hurry from Mouser ordered SC-HA 68pF I get only a Mica / 598-CD15ED680GO3F - could I use this instead of the polystyrene film capacitor with the same good result too? 100uF I got only Panasonic FM / 667-EEU-FM1E101 Panasonic FC are obsolete at the order-time 0.1uF Film Capacitor MKT / 505-MKS2.1/250/5 - are this OK? 79L15 are obsolete at the order time - could I use other types? headsinks are open - what recommend? Resistors - from Vishay Beyschlag MRS25 or SMA 0207 (SMA 0414) I got only some values from Mouser, so I must order some from Distrelec or RS too. Open - the 5mm pitch screw terminal with longer leads - which recommend? Which 68 Ohm resistor for output are recommend? 1W ore more? Two ore more in parallel? I have some WIMA MKP4 10uF 100V for input in my stock (optionally). .... JLH Ripple Eater I got 10 uF Panasonic FC - but I think about to use MKS 2-XL 10 uF Film Capacitor (I have in stock) the Suntan 4700uF 10V - I have in stock .... PSU Jaycar other electrolytics and a headsink are open - what recommend? UF4004 are in my stock Fore headsinks - I live in Austria, middle Europe - mostly we have under 30°C, seldom 35°C (measured in room) Which interconnect wire are recommend? Potentiometer - I think about to use the CP2500 Panasonic from Thel-Audio www.thel-audioworld.de/bauteile/regler/Potis.htm
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Post by Deleted on Jun 3, 2011 15:44:31 GMT
Thanks guys, usual thing, read the thread and stuff stacks of times but didn't get around to sorting an order. Of course now I'm fired up I hadn't the patience to reread! I've ordered some of each type. The axial ones because I couldn't find the radial ones, then after the RS order was posted, I find the 5mm ones at Farnell, despite trying several different search terms earlier Syd
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Post by Deleted on Jun 3, 2011 15:56:40 GMT
As you see I had the same trouble. Following advice from Alex I tried a search on RS and using just 79L15, no additional letters, found some no problem. In UK the Farnell link Alex gave showed 'US stock' which adds around £15 to the item, hence the need to search again.
Have you downloaded Will/Jon Excel BOM? - it gives a link to the long-legged connectors at Farnell.
Syd
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Will
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Post by Will on Jun 3, 2011 19:11:59 GMT
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Post by Deleted on Jun 7, 2011 22:31:56 GMT
Hi Alex, phono preamp is now a working model.....well what held it up?....basically taking the suppliers word on the value of a resistor then finding out that your cheapo DMM cant measure above 2 megohms and telling yourself stick it in it's bound to be 20 megohms....ahhh! Whats the diff' between 20R and 20M in the resistive world.....answer......bloody Maplins crap staff. No that's not fair....check everything.... I hear! I hear! Okay TT is sending a nice signal through the AK phono into "The Sandy K In Class A" it's plenty loud enough and if it wasn't for the background hum sounds okay. Question..........the TT has a separate earth wire which went to my Quad 33 preamp....where on The Sandy K should this earth go? Many thanks, Alan
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Post by Deleted on Jun 7, 2011 23:16:44 GMT
HiAlan Because of their VERY high gain , phon preamps are a sitter for problems like that . You may need to try connecting the TT earth wire to various places, such as the HA/ preamp's IEC earth, or even 0 Volts of the HA/preamp. A low level hum will mask all that lovely low level detail coming from the balancing. Regards Alex P.S. Suggestions are welcomed from Frans, Will etc. who have had more recent experience with TTs than I have.
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Post by Deleted on Jun 7, 2011 23:29:59 GMT
Thanks Alex it's time for bed so I'll fiddle about with it tomorrow. Alan
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Post by Deleted on Jun 8, 2011 2:02:28 GMT
15W/Ch. Class A Upgrade. I have just finished upgrading my Class A amplifier to fully DC coupled, using similar circuitry to the Class A HA/preamp project, but with a few component changes that were needed for higher power operation. I also included a Speaker Protection PCB, as used in the 20W SC Class A, due to the increased risks when using full DC coupling in an amplifier.I also increased it's sensitivity a little as per Frans suggested changes to increase sensitivity. I also included increased the bias from 100mA to 1A. The DC offset to the Speaker terminals without the Offset Correctors in use, was 20mV on one channel, and 22mV on the other channel. This was with no Input connected,but when the DC coupled preamp was working into the amplifier, the DC Offset was reduced to <1mV. The JLHs seen are older home brew ones made using a Positive photo etching process. I soon hope to change over to some of my remaining prettier and more user friendly JLH PCBs, that were designed by RG member Greg Erskine. The further improvement in performance has now given me more impetus to upgrade similar looking PCBs in the existing preamp, using my other pair of PCBs that were designed by Will and Jon. Their performance, as well as using dual mono construction , will give speaker listening a further lift. Alex
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FritzS
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Post by FritzS on Jun 8, 2011 4:55:43 GMT
15W/Ch. Class A Upgrade. I have just finished upgrading my Class A amplifier to fully DC coupled, using similar circuitry to the Class A HA/preamp project, but with a few component changes that were needed for higher power operation. I also included a Speaker Protection PCB, as used in the 20W SC Class A, due to the increased risks when using full DC coupling in an amplifier.I also increased it's sensitivity a little as per Frans suggested changes to increase sensitivity. I also included increased the bias from 100mA to 1A. The DC offset to the Speaker terminals with the Offset Correctors in use, was 20mV on one channel, and 22mV on the other channel. This was with no Input connected,but when the DC coupled preamp was working into the amplifier, the DC Offset was reduced to <1mV. The JLHs seen are older home brew ones made using a Positive photo etching process. I soon hope to change over to some of my remaining prettier and more user friendly JLH PCBs, that were designed by RG member Greg Erskine. The further improvement in performance has now given me more impetus to upgrade similar looking PCBs in the existing preamp, using my other pair of PCBs that were designed by Will and Jon. Their performance, as well as using dual mono construction , will give speaker listening a further lift. Alex Alex, looks very nice Please tell me more about your speaker protection.
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Post by Deleted on Jun 8, 2011 5:55:21 GMT
Friedrich The speaker protection was part of the SC 20W Class A amplifier, and is still available as an individual kit from Altronics. www.altronics.com.au/index.asp?area=item&id=K5124As I do not have AC in the main amplifier case, I simply connected a 3.3V Zener diode between the delay input and the +VE supply rail. As the 15W Class A uses +-20V rails, and the Speaker Protector was designed for +22V or higher, I replaced the series protective diode with a link,due to the relay used being a 24V type. I also connected a green LED on the front panel of the amplifier, via a limiting resistor, in parallel with the relay coil,so that I could have a visual indication of the delay time on switch on, or absence of the green LED to indicate protection has been activated. I was surprised to see they did not make provision for that. If you require more information, let me know. I can't post the pages as it is copyrighted material. Alex
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Post by Deleted on Jun 8, 2011 6:28:37 GMT
Revised schematic. I actually used ON NJW0302G and NJW0281G in the output stages. Attachments:
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Post by Deleted on Jun 8, 2011 8:02:38 GMT
Congrats on the new 'heater system' in your house.
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Spirit
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Post by Spirit on Jun 8, 2011 9:35:57 GMT
Where's mine!? Rhetorical question... I know where progress is up to
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Post by Deleted on Jun 8, 2011 9:46:30 GMT
Congrats on the new 'heater system' in your house. Frans I wish it was much bigger. It's the coldest day in Sydney so far this year. To quote David2vk : "Right now it's hard to believe that we were in the midst of our worst heatwave only 4 months ago" Alex
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Post by Deleted on Jun 8, 2011 11:24:20 GMT
I ordered 49710HA for the Will's PCBs as per the BOM. I was rereading the thread last night and Alex you say not to use them, rather use OPA134. I'm doing, I hope, the final order for these boards and the BOM says DIL08. Those on Farnell are DIP 8, are they correct?
Had to laugh at your 'grouse' about the temperature in Sydney. Its midday, mid summer here and its currently 11!
Thanks, Syd
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Post by Deleted on Jun 8, 2011 11:33:24 GMT
The 3u3 Wima are £2.84 EACH! CPC quote less that 50p but they're out of stock. Is there any alternative to these? US Farnell are about 60p each so it seems strange they're so expensive in UK.
Syd
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Post by Deleted on Jun 8, 2011 11:57:59 GMT
The 3u3 Wima are £2.84 EACH! CPC quote less that 50p but they're out of stock. Is there any alternative to these? US Farnell are about 60p each so it seems strange they're so expensive in UK. Syd Hi Syd That's a bloody rip off ! I can't remember which well known UK supplier Dave Mitchell got stocks from originally, but they were much. much cheaper.All you need is 3.3uF film type capacitor, any voltage , but with 5mm lead spacing. Alex
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Post by Deleted on Jun 8, 2011 12:09:55 GMT
I ordered 49710HA for the Will's PCBs as per the BOM. I was rereading the thread last night and Alex you say not to use them, rather use OPA134. I'm doing, I hope, the final order for these boards and the BOM says DIL08. Those on Farnell are DIP 8, are they correct? Had to laugh at your 'grouse' about the temperature in Sydney. Its midday, mid summer here and its currently 11! Thanks, Syd Hi Syd You can try the LME49710 that you ordered, but if the DC offset is a little too high, grab a handful of the cheap TL071 and pick and choose. Yes, DIP8 is correct. It is now 8.2C here and dropping. You need to remember that we have temps that go over 40C a few times each summer ! 4C is expected overnight, but places like nearby Richmond are likely to go to 0. Alex
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