|
|
Post by firebottle on Feb 2, 2020 11:33:00 GMT
The simple answer is YES. I have proved it this morning with a little experiment.
I have built a stereo amp using Neurochrome boards, shared power supply. The Neurochrome boards have exceedingly good power supply rejection ratio, PSRR.
I have measured for cross talk between channel and there is none. There is only one shared connection, the ground or zero volt of the power supply.
During the last week I have put this amp into two different systems at other locations, both very good, using monoblock amplifiers. In both cases the image width reduced very noticeably.
So I have just made a quick and dirty modification to convert the amp to true dual mono, with completely separate power supplies.
Guess what, the image is wider. Conundrum? Someone explain it please, I don't have an explanation.
|
|
|
|
Post by dsjr on Feb 2, 2020 11:50:37 GMT
You'd know far more about the supply sagging in sharing a common supply compared to two separate ones. I suppose I'm trying to say that a bass heavy channel may pull the other one without the bass down a bit?
One advantage from my times was in having a decent preamp able to drive long cables without loss (hell, even a Quad 33 can do this, but you won't like the band limiting and noise), thereby putting the amps right up to the speakers with very short speaker cables. This assumes the amps don't need long speaker cables to be stable in operation.
It was once told to me that grounding of the two amps was more 'separate' at this end of the chain. I can't explain it better but you may get the drift hopefully of what I'm trying to say.
|
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 2, 2020 11:51:30 GMT
The simple answer is YES. I have proved it this morning with a little experiment. I have built a stereo amp using Neurochrome boards, shared power supply. The Neurochrome boards have exceedingly good power supply rejection ratio, PSRR. I have measured for cross talk between channel and there is none. There is only one shared connection, the ground or zero volt of the power supply. During the last week I have put this amp into two different systems at other locations, both very good, using monoblock amplifiers. In both cases the image width reduced very noticeably. So I have just made a quick and dirty modification to convert the amp to true dual mono, with completely separate power supplies. Guess what, the image is wider. Conundrum? Someone explain it please, I don't have an explanation. It is mad but not unexpected, as I said!! Monoblocks always win out in my opinion and seeing as you have now proved me right, i better do the same to my 686 lol |
|
|
|
Post by firebottle on Feb 2, 2020 12:57:09 GMT
You'd know far more about the supply sagging in sharing a common supply compared to two separate ones. I suppose I'm trying to say that a bass heavy channel may pull the other one without the bass down a bit? One advantage from my times was in having a decent preamp able to drive long cables without loss (hell, even a Quad 33 can do this, but you won't like the band limiting and noise), thereby putting the amps right up to the speakers with very short speaker cables. This assumes the amps don't need long speaker cables to be stable in operation (Naims are better in stability these days I gather and cheap Naim Naits now have output inductors it seems). It was once told to me that grounding of the two amps was more 'separate' at this end of the chain. I can't explain it better but you may get the drift hopefully of what I'm trying to say. The speaker lead length is no problem, I run disparate lengths anyway. I get that a saggy supply can have an effect but the PSRR of the particular boards is immense so technically whatever the supply weaknesses are they should have no effect. The whole image width and presentation gain is more in the mid/high frequencies. |
|
|
|
Post by dsjr on Feb 2, 2020 13:11:42 GMT
Increased stereo separation, especially at high frequencies? Just thinking out loud...
|
|
|
|
Post by sq225917 on Feb 2, 2020 14:53:01 GMT
I cant explain it Alan but I only ever build kit dual mono for my own use, wherever possible.
Assuming crosstalk below -90db or better in a shared chassis it can only be down to sagging rails, unlikely to affect soundstage width, or more likely lower IMD.
|
|
|
|
Post by firebottle on Feb 2, 2020 15:09:23 GMT
Dual mono is the way to go from what I am now hearing, particularly with the Modulus boards.
I did have some monoblocks a couple of years ago and have built quasi dual mono with a shared transformer, however the transparency of the system is now so much better that it really can be appreciated.
Yay!
|
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 2, 2020 15:12:14 GMT
Bollocks.....the pair of ya š¤£š¤£
|
|
|
|
Post by sq225917 on Feb 2, 2020 16:49:53 GMT
Oh yeh, dual mono every time... ;-)
You better get slinging that solder Oli.
|
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 2, 2020 17:00:44 GMT
Oh yeh, dual mono every time... ;-) You better get slinging that solder Oli. Lol, if only I could!!! |
|
|
|
Post by firebottle on Feb 4, 2020 12:22:27 GMT
OK there will further experimentation converting the Neurochrome 286 to dual power supply.
This amp uses a switched mode supply so I have ordered a second to match.
|
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 4, 2020 12:38:47 GMT
OK there will further experimentation converting the Neurochrome 286 to dual power supply. This amp uses a switched mode supply so I have ordered a second to match. I am 100% following your progress Alan, as you know. Hopefully the Coronavirus doesn't slow down the delivery time! |
|
|
|
Post by firebottle on Feb 21, 2020 15:37:10 GMT
OK, the 2nd power supply for the 286 has arrived, in good time compared to the estimate. The board looks similar to this one, as can be seen it's not that expensive. www.ebay.co.uk/itm/SMPS300RE-36V-dual-voltage-300W-230V-Power-Supply-Connexelectronic/142814446122?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649However once I had the top off the 286 and measured properly I realised there was a problem. The internal depth is 200mm, the power supply boards are 100x100mm. There needs to be a 5mm gap all around the pcb for safety, looks like I need to find another 15mm or so, or convert the case into a Tardis  A bit of thinking and increasing the depth of the case seemed the best approach. I have spent all morning cutting and bending an aluminium extrusion, then having to make cut outs where the major dimension fouled the sockets and fixing screws, so quite fiddly. After making a new plate to hold the two pcbs the amplifier looks like this:  The extension frame was covered in some 'carbon fibre' sticky back plastic to look the part.   The result is the only dual mono Neurochrome 286 amp in existence (unless you know better). The performance now has taken on a holographic presentation, most certainly worth the expense and effort to achieve. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Feb 21, 2020 16:51:09 GMT
That look quite cramped.
Glad to āhearā it has made a difference.
When are you doing Oliās?
|
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 21, 2020 17:37:38 GMT
That look quite cramped. Glad to āhearā it has made a difference. When are you doing Oliās? Were gonna have a 686 v DM286 bakoff first. As I said to Alan, when Simon brought his monoblock "486" amplifiers here, I certainly didnt feel like the sound stage was squashed by the 686 when the 486 came out. in fact the 686 was preferable in my system, imo. I was all up for getting it done but now I am less convinced. A bake off is required. |
|
|
|
Post by jimbo on Feb 21, 2020 17:48:57 GMT
I will be watching this one keenly as I am not convinced Dual mono 286 will better the 686.
|
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 21, 2020 17:58:02 GMT
I will be watching this one keenly as I am not convinced Dual mono 286 will better the 686. But will a dual mono 686 be better again?! |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Feb 21, 2020 18:34:17 GMT
I hope to find out, but it will take me a while.
|
|
|
|
Post by firebottle on Feb 21, 2020 18:37:44 GMT
I will be watching this one keenly as I am not convinced Dual mono 286 will better the 686. You need to get around here and hear this James. |
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 21, 2020 18:43:49 GMT
I hope to find out, but it will take me a while. Me too, I'm spent out |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Feb 21, 2020 18:48:36 GMT
I am going to work out the costs etc. and what I need to make a mono block version without an SMPS, even if the amps work well with them.
The Kin seems to work well with them, and for the price difference of the boards, I may as well go 6 rather than 2.
|
|
Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,402
Member is Online
|
Post by Bigman80 on Feb 21, 2020 19:02:08 GMT
I am going to work out the costs etc. and what I need to make a mono block version without an SMPS, even if the amps work well with them. The Kin seems to work well with them, and for the price difference of the boards, I may as well go 6 rather than 2. Very wise K |
|
|
|
Post by jimbo on Feb 21, 2020 19:08:44 GMT
I will be watching this one keenly as I am not convinced Dual mono 286 will better the 686. You need to get around here and hear this James. I know i do. So busy house hunting at moment it is very difficult. |
|
