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Post by claytronics on Oct 23, 2015 21:01:01 GMT
Hi Alex,
Just curious as why a power transistor (2SC5171) is used for Q5 in the schematic when there is hardly any current going through it? Just trying to make my precious stash of 2SC5171's last a little longer. Keep up the great work.
Cheers
Clay
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Post by Deleted on Oct 23, 2015 21:39:57 GMT
Hi Clay
I will soon know (24 hours on bench PSU already) if the attached are as suitable as expected. I just grabbed another 100 for US $9.99 in c a s e these dried up too.
www.ebay.com.au/sch/i.html?_from=R40&_trksid=p2054502.m570.l1313.TR0.TRC0.H0.TRS0&_nkw=100+x+New+SANYO+2SC5707+C5707+NPN+transistors+Japan+&_sacat=0
They may even do a be good job in place of the BC639 too, due to their high HFE ? The complementary 2SA2040 aren't as cheap, but we don't normally need as many of the PNP devices.
The 2SC5171 with the 33 ohm emitter resistor can get quite warm until electrolytic capacitor forming is completed (36 hours typically here) when the larger 2 x 4,700uF parallel capacitors are used.(There is only around 600mV across them)
The other 2SC5171 appears to need a high base current capability because of the large base currents possible at switch on.
I remember years ago seeing a small value resistor used in series with the base junction, when a large value cap was across the base and emitter to help prevent damage.
Kind Regards
Alex
P.S. If required, it should be possible to order further batches of the single JLH PCBs as shown in my photo , at cost price plus P&P . PM Chris for further information about direct ordering and direct payment . |
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Post by claytronics on Oct 23, 2015 22:24:02 GMT
Hi Alex,
Thanks for the fast response. I did think about it may have possibly been due to base current but thought best to check with you. JLH sure knows his stuff so he must have had his reason for picking that device. If I get motivated I might drop my meter in circuit & have a look at start up currents etc. Hey have you ever tried Elna Silmics for C4? They take forever to run in but usually sound good in the end. I use them for decoupling around the output stage of my DAC & find them untouchable in that spot. Wow those Sanyo's on EBay are a bargain, thanks for the link. I will get onto Chris about some boards, good to know as I didn't there were any still available.
Cheers
Clay
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Post by Deleted on Oct 23, 2015 22:48:36 GMT
Hi Alex, Thanks for the fast response. I did think about it may have possibly been due to base current but thought best to check with you. JLH sure knows his stuff so he must have had his reason for picking that device. If I get motivated I might drop my meter in circuit & have a look at start up currents etc. Hey have you ever tried Elna Silmics for C4? They take forever to run in but usually sound good in the end. I use them for decoupling around the output stage of my DAC & find them untouchable in that spot. Wow those Sanyo's on E B a y are a bargain, thanks for the link. I will get onto Chris about some boards, good to know as I didn't there were any still available. Cheers Clay Hi Clay
No, I haven't tried Elna Silmics there. My favourites were actually Suntan Low ESR electros in parallel with a normal electro of the same value. Unfortunately, Suntan used that damned pirated incomplete electrolyte formula, and eventually needed replacing due to domed tops. For analogue areas I find that something like a P a n asonic FC in parallel with say a Rubycon YXF works very well. If both have a very low ESR, HF becomes too detailed, with an overblown soundstage and is ultimately fatiguing. It can also do the same with DIGITAL areas, even when powering an internal LG BR writer !!! That isn't supposed to be possible , is it ? (grin) Incidentally, J.L.H. used BC636 and BC637 initially. He did mention using higher powered devices to avoids the inrush current start up delay problem , but there were no suitable high HFE and high Ft devices available back then ,(or low ESR electros either) and he said this would cause degradation. This is also why the original only showed the max. current as 100mA. The use of the later Toshiba devices permits the J.L.H. to work at >2A provided that the JLH is preceded by a Voltage Regulator or other device to limit the start up inrush current. With my LG BR writer I use series PW5 resistors that are short circuited by relay contacts when the output voltage from the JLH reaches almost full voltage several hundred mS later.
Kind Regards Alex
P.S. Don't forget that when working at voltages as low as +5V and +3.3V you will need to replace the 10K resistor with something like a 1.4mA J506 Current Regulating Diode for proper operation.
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Post by claytronics on Oct 24, 2015 2:21:35 GMT
Thanks Alex,
You certainly are a wealth of information on all this. Chris was very helpful & has given me the info to order some more boards. Works out to $138.50 Aus $ for 26 boards delivered. Certainly very reasonable per board but a rather large quantity for one person. They are single output boards which is good as it makes it more flexible. Alex were you totally happy with the layout, C4 size ect. The only reason I ask is that I regularly design boards & would be more than happy to cad up a one with oversized layout for C. Elna Silmic do a nice 3300uf/10v but it's pretty chunky. I have a great PC fabricator in Hong Kong, ten day lead time & ten board minimum order. Anyway something to think about. I'm located on the Gold Coast QLD so not too far away to ship you some boards when you get low. Panasonic FC's used to be my faveriots then I preferred Pana FM's but these days I find them a little dry/neutral. Tried Nichicon FG's but far prefer Nichicon Muse (KZ) or Elna Silmic II's. As long as you order $200 worth Mouser & Digikey are free FedEx shipping & pricing is excellent.
Hey what about a really compact JLH ripple eater design with SMT's except for the big caps. The Sanyo's you gave me the link for are SMT but still a good size to hand solder. Thanks for all the history on the JLH design, I guess I would need a active probe for my scope to even see any noise/ripple after one of those. That was a great idea with the series PW5 resistor that is relay bypassed after initial inrush current subsides. I designed a mains slow turn on along similar lines for a power amp once. Hey I love all your SC mod stuff. They seem t have gone off track a bit lately, still tying to decide weather to renew my subscription or not.
PS just realised those Sanyo's you linked are thru hole,.
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Post by jc on Oct 24, 2015 2:27:27 GMT
Hi Clay,
That quantity was only the amount I happened to order last time.
If you want less they can do it, I guess the unit price may go up a little though.
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Post by claytronics on Oct 24, 2015 2:33:54 GMT
Thanks Chris,
I might try & find someone in Aus who I could share the order with as it is great value per board.
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Post by Deleted on Oct 24, 2015 3:49:38 GMT
Thanks Alex, You certainly are a wealth of information on all this. Chris was very helpful & has given me the info to order some more boards. Works out to $138.50 Aus $ for 26 boards delivered. Certainly very reasonable per board but a rather large quantity for one person. They are single output boards which is good as it makes it more flexible. Alex were you totally happy with the layout, C4 size ect. The only reason I ask is that I regularly design boards & would be more than happy to cad up a one with oversized layout for C. Elna Silmic do a nice 3300uf/10v but it's pretty chunky. I have a great PC fabricator in Hong Kong, ten day lead time & ten board minimum order. Anyway something to think about. I'm located on the Gold Coast QLD so not too far away to ship you some boards when you get low. P a n a sonic FC's used to be my faveriots then I preferred Pana FM's but these days I find them a little dry/neutral. Tried Nichicon FG's but far prefer Nichicon Muse (KZ) or Elna Silmic II's. As long as you order $200 worth Mouser & Digikey are free FedEx shipping & pricing is excellent. Hey what about a really compact JLH ripple eater design with SMT's except for the big caps. The Sanyo's you gave me the link for are SMT but still a good size to hand solder. Thanks for all the history on the JLH design, I guess I would need a active probe for my scope to even see any noise/ripple after one of those. That was a great idea with the series PW5 resistor that is relay bypassed after initial inrush current subsides. I designed a mains slow turn on along similar lines for a power amp once. Hey I love all your SC mod stuff. They seem t have gone off track a bit lately, still tying to decide weather to renew my subscription or not. PS just realised those Sanyo's you linked are thru hole,. Hi Clay You had me worried for a moment that I may have inadvertently ordered the SMT versions. BTW, I tried 100uF P a n a sonic FM at the output of the JLH and it made it too hard sounding. I used to buy S.C. over the counter at Jaycar, ( I am 10 minutes drive from both Jaycar HQ and Altronics) or on the odd occasion, a Newsagent, but after my legs went late last year, and before my Spinal operation , I was no longer able to purchase it. I have had a look at the contents a few times recently, but nothing much has grabbed my attention enough to start a subscription.They used nice dual input devices in a recent amplifier, but being SMT makes them difficult to select for matching HFE in both channels. It is actually quite hard to check the performance of the JLH, as it's sensitive to where the CRO's earth probe is connected. With my Class A Preamp which uses 2 dual JLHs, I had to make a 10 x low noise opamp preamp in a metal c a s e with 2 x 9V batteries inside. That enabled me to just see a tiny amount of SMPS crap from my TV, where it was previously just a thicker centre line at max. CRO sensitivity at the output RCA sockets., but the opamp wasn't quiet enough to squeeze more gain from it. Will's PCB designs are very nice, but nowhere near as user friendly as those from Greg Erskine, (DIY Audio) who lives on the northern outskirts of Sydney. I would have loved to have seen Greg redesign both the Class A HA/preamp PCB and my version of the S.C. 15W Class A Power Amplifier. Unfortunately, the copper lands sizes used by Will, and mandated by the software he was using, are far too small and make replacing components a nightmare, with a very real risk of damage.You may have noticed a fairly recent post where at a listening session in Sydney, the Class A Preamp and highly modified S.C. DAC beat a >Au. $40K Gryphon preamp and a Bricasti M1 DAC combination ? It's all about power supply , power supply, and power supply, whether a Preamp or a DAC. The front end balancing of the closely matched dual low noise input pair transistors (LS352/2N3811A ) Collector Currents makes a marked improvement in sound stage with both my Preamp and 15W Class A P.A. A simple Current Mirror does not account for the added bias current of the next stage, and there is often > 500mV difference between their collector voltages in most typical designs.
Kind Regards Alex
P.S. I haven't tried this yet, but the 2SC5707 will fit in place of the BC639 in the R.G. designed single JLH PCBs, but not in Greg's dual JLH PCB .
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Post by claytronics1 on Oct 24, 2015 7:10:30 GMT
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Post by Deleted on Oct 24, 2015 8:23:27 GMT
Hi Clay
O.K. I will bite. What is it ?
I can see the 2 Xtals in the top LHS corner, which suggests a DAC .
Chris is more likely to be across this area than I am, as I have been concentrating on improvements with USB Audio recently, and saving higher quality CD rips to USB memory via an UpTone USB Regen, and playing them via the Regen through my main system instead of having a SQ degrading Server in the listening room. Normal rips already on the same USB memory, don't sound as good as fresh rips made using the Regen in line powered by a Linear +9V JLH PSU, and played via the Regen. This suggests perhaps that despite check sums being identical, the earlier .wav files may have suffered irreparable damage due to embedded "Jitter"?
Alex
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Post by jc on Oct 24, 2015 10:24:21 GMT
 I spot the trusty Amanero board on USB to I2S duty. We had a good tinker with those on a thread here. Two approaches were interrupting the 5v bus feed and "injecting" a clean regulated (and JLH!) 3.3v and the use of DIYINHK's galvanic isolating board. Both very useful improvements.
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Post by claytronics on Oct 24, 2015 20:09:28 GMT
Sorry when I did that post yesterday I was having trouble attaching the image & in a rush so the text did not go in properly & will not show up in some browsers.. It is actually a DAC that I manufacture.
This is the text that should have been with it.
Quote
Hi Alex,
yes it makes sense that the Pana FM on the output of the ripple eater hardened the sound up a bit, they are pretty low ESR so not a great spot for them IMHO. Sorry to hear about your legs & back, must be frustrating with Altronics & Jaycar stores so handy.Your class A SC modded preamp sounds spectacular, I have some early kits just sitting there waiting for me when I get the time.I loved the way you tweaked the front end & the DC servo offset corrector. Now getting back to the JLH Ripple Eater I'm getting quite enthusiastic about having a go at getting some boards made myself.I can just add them on to my next work order so will end up getting them very cheap. It will be a double sided with plated thru holes so very DIY friendly for swapping components around. So I will will allow good size & spacing for C4 - any other suggestions? I will label it JLH Ripple Eater with AK mods - correct? PM me your address & I will send you a couple for evaluation. Totally agree with you about power supply is everything when going for good sound. You being a keen builder I thought you might be interested in having a look at my top DAC board. To keep everything legal & approved I run the whole thing from a beefy Daiichi 2.4A 10v AC approved external transformer. Each power supply section is halfwave rectified with a nice Cree SIC schottky diode, then some CRCR filtering using some big Silmics & finally into discrete shunt regulators with a 1000 uf Silmic hanging accross it. Star Earthing for all the psu section.
Well better go, dinner party tonight & wifey calling out for assistance in house cleaning duties.
Regards Clay
The USB regen is certainly interesting, a friend of mine has one & loves it. It needed a decent linear psu to sound right though.
Spot on Chris, the Amanero board plugs straight into the main board & I have a nice separate low noise supply for it. Underneath the Amanaro is the S/PDIF stage using a Wolfston WM8804 chip. I switch the I2S lines with some high quality relays. The S/PDIF has Toslink & coax inputs. The DAC chip is the new AK4490EQ from AKM, 32bit 768K. I'm using it in hardware mode & have two rear toggle switches that let you select four possible digital filter setting inside the DAC chip. Post DAC filtering is a gentle roll off starting at 120K. Output stage is a composite setup with LME49990 / LME49600's, no output caps & dc offset under a millivolt after I trim it. Anyway enough of me raving on about my baby, I just wanted Alex to see how serious I was with the power supply.
Hey getting back to the Ripple Eater, maybe two versions. One standard & the other with on board front end supply. Nice diodes, filter caps & a simple LM317 reg stage. Just connect a transformer to it & you are good to go - what do you think guys?
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Post by Deleted on Oct 24, 2015 21:44:19 GMT
Sorry when I did that post yesterday I was having trouble attaching the image & in a rush so the text did not go in properly & will not show up in some browsers.. It is actually a DAC that I manufacture. This is the text that should have been with it. Quote Hi Alex, yes it makes sense that the Pana FM on the output of the ripple eater hardened the sound up a bit, they are pretty low ESR so not a great spot for them IMHO. Sorry to hear about your legs & back, must be frustrating with Altronics & Jaycar stores so handy.Your class A SC modded preamp sounds spectacular, I have some early kits just sitting there waiting for me when I get the time.I loved the way you tweaked the front end & the DC servo offset corrector. Now getting back to the JLH Ripple Eater I'm getting quite enthusiastic about having a go at getting some boards made myself.I can just add them on to my next work order so will end up getting them very cheap. It will be a double sided with plated thru holes so very DIY friendly for swapping components around. So I will will allow good size & spacing for C4 - any other suggestions? I will label it JLH Ripple Eater with AK mods - correct? PM me your address & I will send you a couple for evaluation. Totally agree with you about power supply is everything when going for good sound. You being a keen builder I thought you might be interested in having a look at my top DAC board. To keep everything legal & approved I run the whole thing from a beefy Daiichi 2.4A 10v AC approved external transformer. Each power supply section is halfwave rectified with a nice Cree SIC schottky diode, then some CRCR filtering using some big Silmics & finally into discrete shunt regulators with a 1000 uf Silmic hanging accross it. Star Earthing for all the psu section. Well better go, dinner party tonight & wifey calling out for assistance in house cleaning duties. Regards Clay The USB regen is certainly interesting, a friend of mine has one & loves it. It needed a decent linear psu to sound right though. Spot on Chris, the Amanero board plugs straight into the main board & I have a nice separate low noise supply for it. Underneath the Amanaro is the S/PDIF stage using a Wolfston WM8804 chip. I switch the I2S lines with some high quality relays. The S/PDIF has Toslink & coax inputs. The DAC chip is the new AK4490EQ from AKM, 32bit 768K. I'm using it in hardware mode & have two rear toggle switches that let you select four possible digital filter setting inside the DAC chip. Post DAC filtering is a gentle roll off starting at 120K. Output stage is a composite setup with LME49990 / LME49600's, no output caps & dc offset under a millivolt after I trim it. Anyway enough of me raving on about my baby, I just wanted Alex to see how serious I was with the power supply. Hey getting back to the Ripple Eater, maybe two versions. One standard & the other with on board front end supply. Nice diodes, filter caps & a simple LM317 reg stage. Just connect a transformer to it & you are good to go - what do you think guys? Hi Clay Unlike Chris, I saw nothing other than the photo using Windows Explorer. I haven't had a wake up coffee yet, so just a few quick points. The attached was designed by Bill from the U.S.A. who is also building the Class A /HA project. I am now mobile enough with the aid of a walker to visit those stores again, except for one major problem. Just over a week ago a big truck forced his right of way from an outside lane to turn left and wrote off my old Magna. If it wasn't so old, the market value would be higher and the front end damage repairable. I am a little bit in limbo here at the moment as far as major projects go, as the house we are renting is up for redevelopment and although our lease has run out, we have yet to receive 3 months notice. Feel free to have a go at other versions of the JLH PCB as it is such a useful design. It pisses me off though when companies like iFi make claims about their world first active noise cancelling techniques. JLH beat them to it MANY years ago ! As for the USB Regen which was a gift from Alex Crespi of UpTone Audio , I am using it in a manner not previously envisaged in order to obtain much higher quality CD rips that are transportable. It annoys me though that so many EEs still refuse to accept that Digital is far from perfect, and that files with identical check sums can sound quite different. The members of Rock Grotto heard it here first , and well respected E.E. and Technical journalist Martin Colloms verified my reports after a series of 6 Blind tests a few years back. Kind Regards Alex
P:.S. Your DAC looks very professional compared with my highly modified S.C. DAC. The JLHs and a Paul Hynes 3.3V regulator take it to a level that makes the original S.C. effort sound very mediocre. Their designs often make good building blocks though !
Incidentally, although the Class A HA/Preamp; is based around the works of both Silicon Chip magazine and U.K. Technical Author and designer Douglas Self, Silicon Chip magazine hasn't published a Class A Preamp design.
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Post by claytronics on Oct 24, 2015 22:23:30 GMT
Hi Alex, I really enjoyed your Silicon Chip DAC upgrade path & have read the threads many times over. I think it was actually part of the motivation that lead to my current DAC design. That's interesting that the CD rips & USB stick playback via the USB regen are improved. I agree that the USB audio path can certainly benefit from psu & filtering/reclocking tweaks. I have had great feedback from Sotm (USB PCI card) owners after I upgraded their cards. I replace all the electros with Nichicon FG's or Pana FM's, film bypasses with nice Wima's & most importantly the USB socket with a Wurth Elektronik filtered type from Element 14. au.element14.com/wurth-elektronik/8492121/conn-usb-2-0-a-w-esd-emi-filter/dp/2442757It has a built in common mode choke on the data lines & a bit of 5v line cap filtering. A bit like AQ Jitter buster but for only seventeen bucks! Thanks for the board layout, will come in handy when I do mine. Cheers Clay PS Mike - I like the Polish housemaid bit, now just have to figure out how to slip her in under the radar! |
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Post by Deleted on Oct 24, 2015 22:35:14 GMT
Hi Clay Incidentally, it took me from 1987 to 2008 to finally get confirmation that complete matching of the collector currents in a well matched ,for both HFE and VBE , Differential input pair resulted in marked gains in soundstage ,transparency etc. Neville Williams from E.A. didn't even reply, and Leo Simpson actually did a 4 page article on my modified design for the old Studio 200 amplifier which I demoed in Jaycar Gore Hill and York St. stores with the permission of their manager. It wasn't until the DIY Audio Current Mirror thread of Nov.2008 that my claims were finally verified. Nelson Pass was a participant in that thread. www.diyaudio.com/forums/solid-state/133018-current-mirror-discussion-15.htmlI will probably be dead and buried before it is finally accepted that .wav files with identical check sums can sound very different though. Kind Regards Alex |
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Post by claytronics on Oct 24, 2015 22:53:06 GMT
Wow Alex that is a long journey. As I said I still have a pair of unbuilt SC 15w class A kits so so I will build them as per your AK preamp version & definately do the front end collector current matching. Very interesting DIY Audio thread too.
Hey I must be a bit slow this morning ( only one coffee) but can you tell me the difference between Wills JLH ripple eater boards & Gregs "Add on shunt reg " boards?
eg is the circuit the same?
Thanks
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Post by Deleted on Oct 24, 2015 23:13:41 GMT
Hi Clay
Look familiar ?
This is what I still presently use. I did also build the RG version using Will's PCBs, but I had to repair it after a small PCB design error with thw new PCB saw the speaker earth being returned via the 10 ohm earth lift resistor.
Both Greg's and Will's PCB designs are functionally identical. The most recent version of Greg's dual PCB can actually be cut in half (carefully!) for 2 separate single PCBs. A future version is likely to have serrations down the centre to facilitate this. I presume that you have also seen that both versions can also be used with 2 added small electros under the PCB with a LM317T replacing the Current Limiter section, to give a regulated version of the JLH ? 2 resistors set the output voltage and no other PCB alterations are needed. Kind Regards Alex
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Post by claytronics on Oct 25, 2015 4:45:57 GMT
Yes Alex, very familiar. I have certainly built a few Altronics kits. I built their S/PDIF signal generator kit which is fantastic for testing DACs. I have trade accounts with Jaycar & Altronics but deal with the latter more these days. Jaycar seem to be moving away from hard core electronic stuff now. In the bottom part of your picture is the small board the DC offset corrector? RE JLH board I'm definately thinking an all in one board might be useful as you always precede the JLH RE with a regulated supply any way. Also I was thinking of using the smaller rectangular heatsinks rather than the big wide one to save board space, what do you think? www.altronics.com.au/p/h0650-16-x-22mm-to220-pcb-mount-heatsink/ I think Chris may have suggested that too. What were the SMT diodes you liked? I can make the pads dual purpose so it would take through hole diodes as well. Once I get a board drawn up I will post it here for your perusal. Hey I like your dual transistor packages on the front end, must track better than seperate packages. Regards. Clay |
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Post by Deleted on Oct 25, 2015 5:36:27 GMT
Yes Alex, very familiar. I have certainly built a few Altronics kits. I built their S/PDIF signal generator kit which is fantastic for testing DACs. I have trade accounts with Jaycar & Altronics but deal with the latter more these days. Jaycar seem to be moving away from hard core electronic stuff now. In the bottom part of your picture is the small board the DC offset corrector? RE JLH board I'm definately thinking an all in one board might be useful as you always precede the JLH RE with a regulated supply any way. Also I was thinking of using the smaller rectangular heatsinks rather than the big wide one to save board space, what do you think? www.altronics.com.au/p/h0650-16-x-22mm-to220-pcb-mount-heatsink/ I think Chris may have suggested that too. What were the SMT diodes you liked? I can make the pads dual purpose so it would take through hole diodes as well. Once I get a board drawn up I will post it here for your perusal. Hey I like your dual transistor packages on the front end, must track better than seperate packages. Regards. Clay Hi Clay Yes, the smaller PCB is the Offset Corrector, and it is similar to that used in the R.G. PCBs. I use the heatsinks shown at the link as I am using a 1U rack case. Jeff C from Brisbane recommended bolting 2 of these together to suit Queensland's higher ambient temperatures. At present I am only using singles with the new R.G. PCBs that I am reluctant to take out again ! www.altronics.com.au/p/h0660-34-x-25mm-heavy-duty-to3p-pcb-mount-heatsink/A
I am using the ES1D SM diodes that have a lower forward voltage drop than average, as well as very low capacitance. Greg's PSU PCB which is a slot in replacement for the original S.C. design, but far more versatile , can take either SM or through hole types in the bridge rectifier section. Like the S.C . design they can also give separate +5V (or 3.3V) output, but there is also provision for an additional +12V or +9V supply using 78xx regulators, which also pre-filters the +5V output and is much better than using a series 100 ohm 5W resistor or a 5V 5W Zener diode as S.C. did. Greg's PSU PCBs can also take the larger Panasonic FC 2,200uF 35V electrolytic capacitors or Elna types. If you crank the leads of the LM317T a little so that it sits closer to the 100nF, you can then fit a larger heatsink such as those used with LEDs , but with a mounting hole drilled in them. This permits use in other higher current applications. A major advantage over the S.C. design is that both main outputs are trimpot adjustable, and not just set by 2 selected resistor values. You will see these PCBs in the attached photo, along with the recent JLH black bottom PCB which uses 2oz. copper. I have a couple of spares of the JLH and PSU PCBs if you would like me to send you a couple of each. The bottom photo was taken before heatsinks were fitted.
Kind Regards Alex
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Post by claytronics on Oct 25, 2015 8:37:53 GMT
Wow Alex your preamp build looks spectacular! Is the offset corrector built into the new RG boards? Looking at the output devices what is the hexagonal metal spacer for? Just a little hard to see in the photo. How does it sound? - silly question I suppose. Great logical layout, so dual external transformers powering it? That is a very generous offer on the pcb's I would love to take you up on that if you are sure you can spare them. I will PM you my details. I have been wanting to make myself a new preamp for ages. Should go well with my new NCC200/ VBE power amp build I am doing at the moment. Shaun on Pink Fish Media has been very helpful getting me all the parts. What power amp do you use?
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Post by Deleted on Oct 25, 2015 9:19:46 GMT
Hi Clay
The offset corrector is built into the RG PCBs, but 78L15 and 79L15 are used instead of the 7815 and 7915 with the later 15W Class A version. The 78L15 can self destruct if you make a mistake. This was also mentioned by S.C. Another problem with this PCB is the tiny copper lands which cause problems if you don't get it right first go. It is powered by 2 separate 18-0-18 30VA (or higher VA ) toroidal transformers.
The hexagonal spacers are for bolting on an additional heatsink with it's mounting pins cut off.
With this design, both active and earth side of inputs are switched to help overcome SMPS crap from non selected SMSP powered sources.
It takes a while to set up the front end balance , but when correctly adjusted the series diode in the differential pair tracks the temperature
differences so that it is near optimum within a minute or 2 after switch on. As mentioned previously, I still use my original PCBs in the 15W Class A which is also DC coupled, including no feedback capacitor. I have attached a photo of a professionally constructed dual mono version of the P.A. that one member had built for him, as well as as my version. With suitable PSUs it can also do up to 7.5W in Class A into 4 ohms, and up to 30W in Class AB into 4 ohms
The power supply powers both the Preamp and the 15W Class A. The 15W Class A uses an electrostatically screened dual 21-0-21 winding transformer from Harbuch which was designed specially for the S.C. design.The S.C. Loudspeaker Protector has been slightly modified so that you see the reassuring switch on delay after around 7 seconds when the front panel LED lights up.
Regards Alex
rockgrotto.proboards.com/thread/10638/reviving-ak-class-preamp-build
rockgrotto.proboards.com/thread/7461/ak-mods-class-15w-amplifier
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Post by claytronics on Oct 25, 2015 12:36:42 GMT
Hi Alex,
Thanks for all the info. I am feeling bad that I have taken this thread off topic though with all my questions. Now reading through "reviving the AK Class A HA"
Heaps of good info there too.
Good night
Cheers. Clay
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Post by claytronics on Oct 25, 2015 21:38:34 GMT
Good Morning Alex,
how did your testing with the 2SC5707 go in the JLH RE? The data sheet info looks very comparable to the previously used 2SC5171 - they just look so dinky & tiny.
As you mentioned with their high dc gain they may actually perform better & also possibly replace the BC639.
Regards Clay
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Post by Deleted on Oct 25, 2015 22:26:59 GMT
Good Morning Alex, how did your testing with the 2SC5707 go in the JLH RE? The data sheet info looks very comparable to the previously used 2SC5171 - they just look so dinky & tiny. As you mentioned with their high dc gain they may actually perform better & also possibly replace the BC639. Regards Clay Hi Clay There is very little noticeable difference when used in conjunction with the Regen. However, on the 16/44.1 track "Come Together-The Beatles" which has a fabulous depth of image via h e a d p hones , I noticed a little too much HF "sizzle" in a couple of places near the beginning.; I double checked, and the Nichicon HE 4,700uF 16V which is in parallel with the P a n a sonic FC has as low an ESR as the P a n a sonic. I expect that replacing that with a Nichicon VZ which is an ordinary electro will correct that. The other JLH uses a normal Suntan (Jaycar) 4,700uF 16V in parallel with the P a n a sonic FC. I reported the Suntan failure problems to Leo Simpson of S.C. with photos, who contacted Jaycar, and I understand that they no longer stock those Suntan electros. As I mentioned previously, 2 low ESR electros in parallel do exaggerate HF detail with Digital, not just with analogue.
Kind Regards Alex
P.S. I hate those inserted links to ads, which is why the additional spacing with some words.
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Post by claytronics on Oct 26, 2015 3:12:22 GMT
Hi Alex,
yes I was wondering what the funny word spacing was, just thought you had finger trouble ho ho
I hate the add links too.
OK, that is good to know the 2SC5707 will work fine, amazingly cheap on EBay. There should be plenty around as I think they are used in PC monitor SMPS supply for the screen backlights. I went through RS & Element 14 & nothing else reasonably priced stood out. Thanks too about the tip not to parallel two low ESR caps for C4 A & B.
regards Clay
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