Because R3 affects the base current & operating point ot TR2/3 not just the input impedance.
Change components to the left of C1.
Change components to the left of C1.
I'm not sure I understand this. The damage is done by the minidsp being there. The level of volume adjustment in the digital domain, shouldn't make any further difference. Adding analogue boards will further reduce the dynamics you are interested in. I don't understand the project brief. It seems like a project to make things worse?Yes true I can adjust the level in the DSP but I don't like dropping late amounts digitally, so just want to trim digitally only by a few db if possible
@friendly1uk, hi
The system uses multiple subwoofers controlled by a mini DSP 10x10 unit for EQ and timing (subs only), the 10x10 is unfortunately analogue in which is then internally converted to digital and back again (Reasonable quality A>D and D>A DACs, with an upgraded unit with better power supplies etc). The output impedance to the 10x10 is 560 Ohms. I'd love to do all DSP digitally before converting to analogue, but this is not an option outside of £10k plus of investment and a total reconfiguration and there are only a few devices that can do this unless you buy a poor sounding AV processor and I had an Acurus ACT4 and it was easily 'beaten' sonically by analogue out from a good BR player into an old naim AV2 (go figure....)
All the subs currently are 'driven' by BK Electronics BPSB500 plate amplifiers and they are sonically very good indeed as I have experimented with alternatives and even replaced the amplifiers in my Sonus Faber Crimona subs with these units. They are Mosfet with strong power supplies and high damping factor amps. All these units have pre amps included as well as power amps (they have gain and phase etc) I do not use phase or other controls other than gain. This allows me to get the amps in the ball park, I simply trim then digitally.
Why not just cut significant db digitally ?
Interestingly during the evolution of my system, adding and aligning more subs I did at one point have quite a large amount of db cut to some subs in the 10x10 HD, I then read about the SNR reduction when digitally cutting volume, so I bothered to adjust and reset all volumes (matching curves identically in REW as the gain is analogue on the 500's) reducing analogue gain. It was better enough for me to A-B in case something else had changed, it was better with trim only in the DSP
So I want to A-B the 1000W units and see if they are as good as the 500's and not realise that they could be better configured with a small pre-amp/buffer etc. I could of course just adjust the gain in the DSP and I am sure it would work fine, but I want to get the units to work and sound as good as they can. So I will try the passive pot and probably leave alone if they sound as good or better with just a pot, but I'm bound to have an itch to try a small preamplifier in the loop at some stage incase I miss some performance for the sake of a small investment and experiment. Also I can try the pot wide open and trim digitally to check too, again.
The system uses multiple subwoofers controlled by a mini DSP 10x10 unit for EQ and timing (subs only), the 10x10 is unfortunately analogue in which is then internally converted to digital and back again (Reasonable quality A>D and D>A DACs, with an upgraded unit with better power supplies etc). The output impedance to the 10x10 is 560 Ohms. I'd love to do all DSP digitally before converting to analogue, but this is not an option outside of £10k plus of investment and a total reconfiguration and there are only a few devices that can do this unless you buy a poor sounding AV processor and I had an Acurus ACT4 and it was easily 'beaten' sonically by analogue out from a good BR player into an old naim AV2 (go figure....)
All the subs currently are 'driven' by BK Electronics BPSB500 plate amplifiers and they are sonically very good indeed as I have experimented with alternatives and even replaced the amplifiers in my Sonus Faber Crimona subs with these units. They are Mosfet with strong power supplies and high damping factor amps. All these units have pre amps included as well as power amps (they have gain and phase etc) I do not use phase or other controls other than gain. This allows me to get the amps in the ball park, I simply trim then digitally.
Why not just cut significant db digitally ?
Interestingly during the evolution of my system, adding and aligning more subs I did at one point have quite a large amount of db cut to some subs in the 10x10 HD, I then read about the SNR reduction when digitally cutting volume, so I bothered to adjust and reset all volumes (matching curves identically in REW as the gain is analogue on the 500's) reducing analogue gain. It was better enough for me to A-B in case something else had changed, it was better with trim only in the DSP
So I want to A-B the 1000W units and see if they are as good as the 500's and not realise that they could be better configured with a small pre-amp/buffer etc. I could of course just adjust the gain in the DSP and I am sure it would work fine, but I want to get the units to work and sound as good as they can. So I will try the passive pot and probably leave alone if they sound as good or better with just a pot, but I'm bound to have an itch to try a small preamplifier in the loop at some stage incase I miss some performance for the sake of a small investment and experiment. Also I can try the pot wide open and trim digitally to check too, again.
The SN issue hadn't crossed my mind, but of course, a smaller signal is closer to the noise floor, and thinking a bit further, dynamically has less far to fall.
I reckon with reduction only in mind, I would find whats good with a cheap VR, then buy some nice fixed resistors to replicate it. Using the minidsp for fine adjustments after that.
I reckon with reduction only in mind, I would find whats good with a cheap VR, then buy some nice fixed resistors to replicate it. Using the minidsp for fine adjustments after that.
looking at the active option in parallel. I have seen a review of this unit, seems okay and very cheap. The 18v-0-18v AC transformer will cost more. I would just use one channel on each or possibly run two mono pots and have the powered unit in one sub amp and the output to both. Any thoughts ?
https://www.aliexpress.com/item/100...djYhPKwC&utparam-url=scene:search|query_from:
https://www.aliexpress.com/item/100...djYhPKwC&utparam-url=scene:search|query_from:
The units are coming together and I have ordered one of the super cheap pre-amps above a 5534 with regulator supply all it needs is a 18 0 18 transformer, so wondering if there are any recommendations for reasonable items I will be space limited if I keep it inside. I’ll use the inside lid (I have some aluminium covers I had folded up)
Ideally a relatively low profile toroidal and perhaps a 40-60 KVA so useful for something else if I prefer the passive solution
Any suggestions ?
Ideally a relatively low profile toroidal and perhaps a 40-60 KVA so useful for something else if I prefer the passive solution
Any suggestions ?
£30 on the doorstep?
https://www.aliexpress.com/item/1005007786819127.html
I could shave a fiver off, but you would loose the mounting hardware. A cost that's usually separate.
It's 100VA, and copper, which shouldn't need saying, but from China it does.
A 30VA from eBay is £20 but needs the hardware https://www.ebay.co.uk/itm/285615718000
I'm not sure how much use an 18-0-18 100VA will have in the future.
I'm chewing over the idea of a normal transformer. Less thought towards mounting them, more energy dense, and it's not a high stress situation. A pre-amp may not need the virtues of a toroid, but be more interested in the smoothing caps, or even regulators used. As you say, these are not expensive boards.
https://www.aliexpress.com/item/1005007786819127.html
I could shave a fiver off, but you would loose the mounting hardware. A cost that's usually separate.
It's 100VA, and copper, which shouldn't need saying, but from China it does.
A 30VA from eBay is £20 but needs the hardware https://www.ebay.co.uk/itm/285615718000
I'm not sure how much use an 18-0-18 100VA will have in the future.
I'm chewing over the idea of a normal transformer. Less thought towards mounting them, more energy dense, and it's not a high stress situation. A pre-amp may not need the virtues of a toroid, but be more interested in the smoothing caps, or even regulators used. As you say, these are not expensive boards.
Thanks, yes I will look at the smoothing caps and upgrade, suddenly it’s a black hole of hang on what about a better opamp I’ve already committed to a better pot and thinking about space and whether some nice film bypass might be squeezed in !
I have got plenty of Silmic and KZ, ES around for better filters caps
The pre will ideally be in the 35mm gap by the side of the caps. I’ll work out a little sheild too
I have got plenty of Silmic and KZ, ES around for better filters caps
The pre will ideally be in the 35mm gap by the side of the caps. I’ll work out a little sheild too
lol
There is always something better to try, but before testing, perhaps I was getting ahead of myself. Looking for a satisfying reason to cheap out on the transformer. That 35mm gaps not a lot to play with. That 100VA isn't going in there, and the 30VA is 32mm + hardware. I'm not sure I would want to cram that in. I would have to give airflow some thought. Plus that 35mm is defined by the caps, and the removable case it seems. So there is no fixing point yet
There is always something better to try, but before testing, perhaps I was getting ahead of myself. Looking for a satisfying reason to cheap out on the transformer. That 35mm gaps not a lot to play with. That 100VA isn't going in there, and the 30VA is 32mm + hardware. I'm not sure I would want to cram that in. I would have to give airflow some thought. Plus that 35mm is defined by the caps, and the removable case it seems. So there is no fixing point yet
Thinking of using the side of the alloy panel to mount the pre and wire so the connections can allow the lid to come off with the preamp on. I wonder if two transformers close would be okay
Edit: I think I posted on the wrong thread lol
Back on this topic, I would be surprised if the transformers didn't interact. Even crossover inductors are turned through 90 to not effect eachother.
Back on this topic, I would be surprised if the transformers didn't interact. Even crossover inductors are turned through 90 to not effect eachother.
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A quick read and I think with an additional sheild if I can fit it should be okay, as the pre transformer will be 10+mm away and oriented differently
I’ll have a little bit of a mock up to see I gave a 12v fan that showed a good reduction in temp so will fit with a thermostat- I’ve already decided to build a small unregulated linear as the switch mode has given me the jitters about RFI
I’ll have a little bit of a mock up to see I gave a 12v fan that showed a good reduction in temp so will fit with a thermostat- I’ve already decided to build a small unregulated linear as the switch mode has given me the jitters about RFI
Attachments
I use Arctic fans, and I think one has it's own thermal control now. Let me see..
https://www.arctic.de/en/P12-TC/ACFAN00176A
38C target, through fan speed regulation. You can set it's voltage lower, to limit full speed. Should be quiet, considering it's
Late for work.. gone
https://www.arctic.de/en/P12-TC/ACFAN00176A
38C target, through fan speed regulation. You can set it's voltage lower, to limit full speed. Should be quiet, considering it's
Late for work.. gone
I found a pot of flux that measures 34.5 mm diameter its 75mm x 34.5mm most of the potential 50-60 VA options seems to be 34mm or some more, so very tight !
But at 34mm I could fit and copper foil wrap the side of the caps as well, the leads could come out at the top as the internal height is 100mm +
Easy !
But at 34mm I could fit and copper foil wrap the side of the caps as well, the leads could come out at the top as the internal height is 100mm +
Easy !
This looks like an option 50VA https://www.switchelectronics.co.uk...8-toroidal-transformer-50va-0-18v-vigortronix
I think they got the dimensions wrong. My ebay link to their shop, shows the size of them all.
You might need to go to the manufacturers site.
The foil idea might create a shorting ring, if it comes loose.
You might need to go to the manufacturers site.
The foil idea might create a shorting ring, if it comes loose.
Looks like Toroidy might have something suitable, I'll confirm dimensions.
I do like the copper foil, if you add to clean surfaces it sticks very well, seems to be removable in a week or two but after then it's really difficult to get off without a Stanley knife and a lot of isopropyl alcohol
I do like the copper foil, if you add to clean surfaces it sticks very well, seems to be removable in a week or two but after then it's really difficult to get off without a Stanley knife and a lot of isopropyl alcohol
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