Interesting thread. I think I hear my (happily working for 3+yrs) A500 asking for some modification loving... Is that schematic still available?
jhpike_at_cox_dot_net
TIA!
jhpike_at_cox_dot_net
TIA!
Hello linuxworks
i did the mod you showed on your fotos cool, my question is it possible to remove the hole display board ?
thanks
hironimo
i did the mod you showed on your fotos cool, my question is it possible to remove the hole display board ?
thanks
hironimo
It lives!
This is an old thread but still a good one and it reminds me that many of you in other countries won't have got to hear about a discovery we made here in the UK concerning the A500.
Quite simply, it's performance improves dramatically when bi-amped. This of course assumes that your speakers are bi-amp capable. The main improvement was in 'boogie factor'. The A500 suddenly discovers 'rhythym' and 'groove' when bi-amped.
This is an old thread but still a good one and it reminds me that many of you in other countries won't have got to hear about a discovery we made here in the UK concerning the A500.
Quite simply, it's performance improves dramatically when bi-amped. This of course assumes that your speakers are bi-amp capable. The main improvement was in 'boogie factor'. The A500 suddenly discovers 'rhythym' and 'groove' when bi-amped.
Hi,
can you be more specific?What do you mean by bi-amped? You can't bi-amp
an amplifier!!!
B.L
Bi-amping: using two amplifiers instead of one.
In our case, one amp drove the bass units and the second amp drove the treble units.
Hi there,
I know this is an old thread, but hopefully I can get some help.. 😱
I've just performed the above mod on one channel of my A500. I was unable to get the OP2134, so I went for the LM4562-MA thinking that would also be compatible
It hasn't worked!! The speaker "pulsates" with a loud humming noise. As you turn up the volume pot you can hear the music getting louder but it's very distorted and the pulsating and humming gets louder to!!
I'm no expert on this matter but I imagine the LM4562 is not a straight drop in replacement like the older OP2134 is??
Is there any modifications I need to make to the surrounding components to make the LM4562 work in this circuit?? Or is there a newer better version of the OP2134 that would be a straight drop in replacement??
Cheers..
Murphy
Hi there !
Can someone give me info about A500 Power Transformer ...
I got some info to deliver 2x52v - but i dont know what is VA .. someone even talk about 600VA ????
Thanx !
Can someone give me info about A500 Power Transformer ...
I got some info to deliver 2x52v - but i dont know what is VA .. someone even talk about 600VA ????
Thanx !
I know that there are many factors which result in quality sound or the opposite, but in a blind A/B/X level-balanced test of several studio/PA amps, an amp measuring 3% crossover distortion had a noticeably inferior stereo dimension and overall less interesting character than the rest.
I don't know if "this equals that", but in case it does, there it is.
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Ok, So not much feedback about my op amp dilema 😕
I was studying the circuits for the A500, and I'm now wondering if it's easier/possible/better to actually bypass the input stage (remove both Op amps and C53) and inject the signal directly to the junction of C19 & R65?? I am driving the A500 with a DCX2496 using J Didden's active i/o mod..
Any thoughts will be appreciated..
Cheers..
Hi,
That OP-amp is crucial for this amp to work, do not remove it. Just look at pin 5 (+in), that is the overall feedback in this circuit!
If you just swap the OP-amp (with something entirely different) oscillations will most likely happen. Compensation must be altered if you want to use a faster/slower OP-amp.
Thanks for your reply..
I figured as much about IC2.. 🙁
So,, can I get LM4562 to work in this circuit,, or do I just revert back to JRC4580.. This thread originally states OP2134, but I cannot seem to get the smd version in Aus, and I wonder if I would have had the same problem using them as well??
Cheers..
Murphy
Anybody to send me the schematics of the A500 (wwwebdrei(at)aon.at) or can tell the voltages of the toroid ?
Thanks
Michael
Thanks
Michael
Has anyone experienced problems with A500 channels randomly going quiet?
I've got 8 (yes, eight!) A500s running my cinema room and ChA on one of them goes quiet every so often. Its deffo the amp as I've swapped amps around and it follows that particular amp. The only way to cure it is to wiggle the XLR or jack. I've tried both thinking it might be a duff XLR connector but the symptoms persist. I've had it in bits, gone over all the solder joints with a magnifying glass and an iron, cleaned and reseated all the connections, no joy. 😕
Also has anyone done distortion measurements with the OPA2134 opamp mod? I think I've got a tube of SOIC package OPAs somewhere 🙂
I've got 8 (yes, eight!) A500s running my cinema room and ChA on one of them goes quiet every so often. Its deffo the amp as I've swapped amps around and it follows that particular amp. The only way to cure it is to wiggle the XLR or jack. I've tried both thinking it might be a duff XLR connector but the symptoms persist. I've had it in bits, gone over all the solder joints with a magnifying glass and an iron, cleaned and reseated all the connections, no joy. 😕
Also has anyone done distortion measurements with the OPA2134 opamp mod? I think I've got a tube of SOIC package OPAs somewhere 🙂
LM4562 will made this amp oscillate! The input OP is the crucial part of this amp, and I will play the game on the safe side: OPA2134, OPA2604, OPA2111. Definitely not LM4562 series! Has anyone tried QSC (same circuit, but it has DIP sockets for easy OP swapping)?
