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Acurus A250 and starground

What gear should I buy to start make some serious measurements of the amplifiers: Watt, THD+N, S/N ratio and so on. I have a laptop, I'm on the market for an oscilloscope, but what else: software/hardware ect?

Regards
 
KNielsen said:
What gear should I buy to start make some serious measurements of the amplifiers: Watt, THD+N, S/N ratio and so on. I have a laptop, I'm on the market for an oscilloscope, but what else: software/hardware ect?

Regards
Click to expand...

Well unfortunately that's a very broad subject and the best answer is that it depends on you and your budget. Its been covered at length in the past. I'd recommend that you go over to diyaudio and start digging in the "Equipment & Tools" forum. There's a thread there that was started with a similar theme recently, here. There have been others in the past.

I started with an old HP334, then moved up to an HP339A, added a Quantasylum QA400 then sold the HP339A and bought a pair of Amber 3501's before deciding I really needed a good automated system that would store data. Then I moved up to my current system which is an old Audio Precision System One which I'm quite happy with. Warning*** The AP stuff requires a custom interface so do a LOT of research if you're going to go that route.

Everything you'll look at will have its pluses and minuses and some of the minuses are significant so do your homework on whatever you're thinking about buying.
 
mondialfan said:
Well unfortunately that's a very broad subject and the best answer is that it depends on you and your budget. Its been covered at length in the past. I'd recommend that you go over to diyaudio and start digging in the "Equipment & Tools" forum. There's a thread there that was started with a similar theme recently, here. There have been others in the past.

I started with an old HP334, then moved up to an HP339A, added a Quantasylum QA400 then sold the HP339A and bought a pair of Amber 3501's before deciding I really needed a good automated system that would store data. Then I moved up to my current system which is an old Audio Precision System One which I'm quite happy with. Warning*** The AP stuff requires a custom interface so do a LOT of research if you're going to go that route.

Everything you'll look at will have its pluses and minuses and some of the minuses are significant so do your homework on whatever you're thinking about buying.
Click to expand...
Wow I actually thought it would be easy :)
Audio Precision had my attention, and thought it was just a simple purchase and ready to measure. I'll do as recommended and see what comes up;)

Thanks
 
Stupid question... The amp works perfect but,,,,,

Some one told me that I have made a two groundloops!!
The two black metal pieces on each side of the caps. I'm told to cut this connection near the wires for the output stages??? The connection between 4/5....
I've attached the setup:
- 1/2 from bridge rectifiers
- 3 central groundpoint
- 4/5 out
IMG_20190929_222548_919.jpg
FB_IMG_1569868449291.jpg
 
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Have you looked at the QuantAsylum products? I don’t have any personal experience with them but have had my eye on the QA401 for a while and they are much less money then even an old used AP.
 
KNielsen said:
Stupid question... The amp works perfect but,,,,,

Some one told me that I have made a two groundloops!!
The two black metal pieces on each side of the caps. I'm told to cut this connection near the wires for the output stages??? The connection between 4/5....
I've attached the setup:
- 1/2 from bridge rectifiers
- 3 central groundpoint
- 4/5 out
View attachment 1632194
View attachment 1632198
Click to expand...

I don't think having the two ground bars or straps or whatever you want to call them in the outside pairs of caps is a good idea. I think that overall it would be better to have a solid plate that was wider and reached all of the caps ground terminals instead of having the short wires connecting the outer caps to the main ground plane. However if the amp is quiet and you're happy with it then I'd probably leave it alone.
 
Fsatsil said:
Have you looked at the QuantAsylum products? I don’t have any personal experience with them but have had my eye on the QA401 for a while and they are much less money then even an old used AP.
Click to expand...


The QA401's attenuator will not suffice for an amp with the output capability that the A250 has. You'd have to build an additional attenuator to measure a 300+ Watt amp at full power.
 
KNielsen said:
Wow I actually thought it would be easy :)
Audio Precision had my attention, and thought it was just a simple purchase and ready to measure. I'll do as recommended and see what comes up;)

Thanks
Click to expand...

If you want to look into the AP stuff. You need to do a lot of homework especially for the older AP stuff like the P1P, ATS 1, & System One. This link has some more info about the older AP System One options and how to communicate with them. I'm using the APIB LPT translator that is mentioned with a laptop running Win 98SE.

Also if you're on Linkedin, a fella named Duke runs a user group there. He's an ex-AP employee and repairs/upgrades the old legacy AP stuff. He's also a good source of knowledge/parts/service for them. Duke also sells a USB adapter that will run both the old System One and a newer System Two on modern computers with Win7 & Win 10. Duke goes by the name Audio1Man on DIYAUDIO.
 
mondialfan said:
I don't think having the two ground bars or straps or whatever you want to call them in the outside pairs of caps is a good idea. I think that overall it would be better to have a solid plate that was wider and reached all of the caps ground terminals instead of having the short wires connecting the outer caps to the main ground plane. However if the amp is quiet and you're happy with it then I'd probably leave it alone.
Click to expand...
The A250 is dead quiet, I cannot hear it connected to my speakers, and the torodial never makes a sound as it did before I started. After the mods it's the rest of the system that has come to my attention regarding noise. As DIY never ends?? ;)
I'll leave it, but when I build the PSU I did find it an odd solution the way the schematic established the connection to ground at the e.caps...

Regards
 
If your amp is dead quiet I wouldn’t mess with it. Sometimes you try to fix a problem that doesn’t exist and you end up with a new problem.
 
I actually would try it, if I had access to god equipment, see what's happening. But for now it's good, all measurements are good, no loops :)

-- I can only recommend people to try enhance their grounds like I did. Big improvement in soundstage.
BUT NOT WITHOUT SERIOUS MEASUREMENTS AND VERY GREAT CARE MUST BE TAKEN WHEN POWERING UP!!! -- Do this wrong, and you'll end up with a dead amp before you even know it! ;) Actually I wouldn't recommend it! Just in case....
 
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I've got an A250 that's only playing mid/treble from right channel... Any idea what's wrong??
Everything looks good on the circuit.
My main focus was around D11/R11/C12/Q15..., But the rest is also ok.....
Thanks
 
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KNielsen said:
I've got an A250 that's only playing mid/treble from right channel... Any idea what's wrong??
Everything looks good on the circuit.
My main focus was around D11/R11/C12/Q15..., But the rest is also ok.....
Thanks
Click to expand...
Ok... D6 is not measuring correct. I pull it, measure.. then ok.. anyways I find a new diode, install on D6. Know it is also measuring incorrectly. Not like D3..
 
Problem solved. Bad connection at C7.. :)
Still don't understand why D3 an D6 don't measure the same mounted in circuit?
 
I'm learning..... Haven't got any more time for today but so far:
D6 is toasted, measuring as a resistor.
Changed D6
D3 is ~27mohm/4mohm (I'll suspect this to be faulty, but haven't checked the datasheet)???
D6 is now in circuit ~22mohm/0.8mohm
I have desoldered Q9/10. - They are ok.
Q5/12 is also ok.
There are no burned areas, nor signs of leaks or shorted solderings on the board.
I do not see 27mVdc as signs of Q4/11 being damage, but there is a leak somewhere..

That's it for today.. we have guests the rest of the day, although this is more interesting right now :)

Regards
 
Sorry I've been very preoccupied lately so I'm a bit late in responding.

D6? Hmm that's not one that generally fails. About the only way this should fail is if the resistance from the neg rail to D6 drops really low like well below 10k ohms for some reason. This could be due to a failing R14 or a solder bridge possibly bypassing R14.
 
mondialfan said:
Sorry I've been very preoccupied lately so I'm a bit late in responding.

D6? Hmm that's not one that generally fails. About the only way this should fail is if the resistance from the neg rail to D6 drops really low like well below 10k ohms for some reason. This could be due to a failing R14 or a solder bridge possibly bypassing R14.
Click to expand...
actually I think you are right in your assumption. R14 did show odd figures in circuit. About 500ohms or something. When I desoldered D6 and replaced with new, R14 where as RN60's are... Spot on!
But I'm not taking any chances, the Dim Bump didn't blow but, turned off as it should, even though the 220uf R7 wasn't properly connected. I'm afraid if something else has been damage when full power was applied.
I do find it odd that D3 dont measure the same as D6 in circuit. I'll continue checking the transistors when time allows. For me October has started quite bad in many ways, lots to do ;)
But maby a faulty current form D6 is what I saw when adding a little volume to the speakers?? I hope (fingers crossed)...

Thanks and God day to you :)
 
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