QUDOS - the brilliant new amplifier boards from Avondale
- Thread starter misterc6
- Start date
Pine Marten
pfm Member
I converted my 110 monos to Qudos+ minicap6 boards a few months back and am very happy with them. I bought ready built boards directly from Les and apart from checking bias and dc offset have left them as stock. I am curious as to the idea of feeding the "front end" of the boards with a regulated supply as described in the previous few posts. I'm interested in finding out what the benefits, sonically, are to this idea. I'm reasonably skilled at building smaller circuits such as described, on veroboard,or does someone do ready made bare pcbs? There is certainly space in the shoeboxes for this. Might also fit Vellemann protection boards at the same time. The 32.5 is stuffed with RSL boards, which have on board regs and the HiCap has self built TeddyRegs and recent new big caps!
RichardH
Bodging pleb
Les's gyrator boards may do the trick, but aren't quite the same as the suggestions above - which are, to be fair, untested. However, I would expect the results to be in line with the comments Teddy made about the NCC200 regulation back in the thread I linked to previously.
Pine Marten
pfm Member
Thanks for the link, Richard, very interesting read. Looking forward to any further ideas you or others may have on this subject.
BobMaximus
pfm Member
I feel I should point out here that if one of those regulated front ends fails, then this’ll result in full on DC across the speakers. Without some sort of protection, I’d feel uncomfortable with this arrangement. In other words, you need to know what you are doing.
However, I’d be interested to know if the regulation really does provide a worth-while improvement over the stock resistor / capacitor smoothing.
However, I’d be interested to know if the regulation really does provide a worth-while improvement over the stock resistor / capacitor smoothing.
RichardH
Bodging pleb
You're wise to sound a note of caution, Bob!
I have the Velleman speaker protection module installed in my amp (which protects from DC), so hopefully am safe on that front. Having said that, I intend to run these as standard for a good while - otherwise I won't have an idea how they perform compared to the NC200s - though I do have this front end reg on the NC200s at present.
I have the Velleman speaker protection module installed in my amp (which protects from DC), so hopefully am safe on that front. Having said that, I intend to run these as standard for a good while - otherwise I won't have an idea how they perform compared to the NC200s - though I do have this front end reg on the NC200s at present.
James Evans
Bedroom Bodger
Richard, did you ever get confirmation from Les on the differing resistors values in the two different NCC220 schematics posted earlier?
BobMaximus
pfm Member
OK Richard. Another point is that you need to keep that diode D4 and its associated resistor in place. Otherwise, the charge across the smoothing capacitor will be “stolen” by the output stage. In other words, the capacitor replacing C5 becomes superfluous. Plus you should probably increase its size, to take into account the current dissipated by the LM317. Just a thought anyway!
RichardH
Bodging pleb
No, not as yet. I imagine he had plenty of emails to deal with on his return. I might check with him later, but don't want to keep bothering him.
martin clark
pinko bodger
V good comments by BobMaximus.
- Do have DC protection in place at the amp's output if you like amp-tinkering DIY!
- The feed to the reg could be tapped-off after the standard diode+R (although 10R+100uF is a low-pass at 16hz which any 3pin reg will eat and if sustained - will simply drop out of regulation if the raw supply is pulled down a long way, so no worse than a standard NAP: nothing bad will happen. you won't distinguish it as loss of performance by ear, because things will be at f'ing loud for a while already at that point..)
- Practically, the real/most-likely risk of loosing one front-end rail is likely to be mechanical failures in the wiring, rather than the electronics you might choose to add for front-end 'regulation' (whatever form of filtering you choose) : as soon as you take such a thing off the amp pcb, consider well how your sub-circuit is put together, and how that could mechanically fall apart / the inter- wiring fail. One loose/dodgy/'just-tacked-for-now' wire could put you in the territory BM describes. Make it all robust in a mechanical sense, as well as an electrical one, and you'll be fine.
- Do have DC protection in place at the amp's output if you like amp-tinkering DIY!
- The feed to the reg could be tapped-off after the standard diode+R (although 10R+100uF is a low-pass at 16hz which any 3pin reg will eat and if sustained - will simply drop out of regulation if the raw supply is pulled down a long way, so no worse than a standard NAP: nothing bad will happen. you won't distinguish it as loss of performance by ear, because things will be at f'ing loud for a while already at that point..)
- Practically, the real/most-likely risk of loosing one front-end rail is likely to be mechanical failures in the wiring, rather than the electronics you might choose to add for front-end 'regulation' (whatever form of filtering you choose) : as soon as you take such a thing off the amp pcb, consider well how your sub-circuit is put together, and how that could mechanically fall apart / the inter- wiring fail. One loose/dodgy/'just-tacked-for-now' wire could put you in the territory BM describes. Make it all robust in a mechanical sense, as well as an electrical one, and you'll be fine.
grahamdocman
pfm Member
Having had a brain fart and consulted Martin, here is the corrected diagram - still untested in anger, so be warned:
Hi Richard, this is really helpful.
But I think I'm being a bit slow off the mark, I can't see any difference between this schematic and the one in your post #399 which you initially felt was incorrect ? Has the image in #399 been automatically updated ?
Thanks for your advice,
Graham
mega lord
Centre tapped
Has anybody considered changing NCC200 populated boards to qudos (NCC220) spec ?
*The resistor and capacitor value changes are easily done as is the removal of R29 (100R) and D5 (1N4148).
*The 2N5551 bias transistor (TR5) could be left as is if not increasing the bias current past 38mA or a BD237 could bolted to the heatsink with flying leads to enable higher bias current.
*The one component that I don't know about is the output transistor (change from MJ15003 to MJ15004). Could the MJ15004 be inserted in place of the 15003 without too many hassles ? Do tracks need to be cut, bits of wire soldered in ?
Many thanks.
*The resistor and capacitor value changes are easily done as is the removal of R29 (100R) and D5 (1N4148).
*The 2N5551 bias transistor (TR5) could be left as is if not increasing the bias current past 38mA or a BD237 could bolted to the heatsink with flying leads to enable higher bias current.
*The one component that I don't know about is the output transistor (change from MJ15003 to MJ15004). Could the MJ15004 be inserted in place of the 15003 without too many hassles ? Do tracks need to be cut, bits of wire soldered in ?
Many thanks.
