Even with the 8i6 having an input impedance of 44k the transformer I described is an attenuator. The voltage in the secondary is 4 times the voltage in the primary.
VS = 4*VP
If we call what the 8i6 sees V8i6 the output impedance of the transformer and the input impedance of the 8i6 act as a potential divider
V8i6 = (44/(44+160))*4*VP = 0.86*VP
If we do it right and make the output impedance of the transformer 1/10 of the input impedance of the 8i6 that gives us an impedance of 4.4k in the secondary, which is 275 in the primary. We've simply moved the problem to the primary as 275 will be lower than the output impedance of the Bass Station.
If someone wants to juggle the numbers and come up with a scenario where a transformer can provide a boost, please do.
Audio interface line input level
Re: Audio interface line input level
Merlyn, transformers are not potential dividers.
As the first example that I found look at the Sowter 3483, a "600 Ohms to 10k Ohms".
That is near as jazz 1:4 and gives a loss of only 0.3dBu when loaded with 10k and with a source resistance of 40 Ohms. Now, the source R of the Bass Station will not be that low but it could easily be 100-120 Ohms. But the load is 4. times 10k so I submit that the transformer WILL give a decent chunk of the desired 12dB boost.
This does not of course get around the fact that transformers used in isolation (Boom! Boom!), without being specifically 'tweaked' to the actual circuits will always give a bit of a ragged response but a voltage boost they certainly will give!
Otherwise how have all those valve pre amps worked for the last near century?
Dave.
As the first example that I found look at the Sowter 3483, a "600 Ohms to 10k Ohms".
That is near as jazz 1:4 and gives a loss of only 0.3dBu when loaded with 10k and with a source resistance of 40 Ohms. Now, the source R of the Bass Station will not be that low but it could easily be 100-120 Ohms. But the load is 4. times 10k so I submit that the transformer WILL give a decent chunk of the desired 12dB boost.
This does not of course get around the fact that transformers used in isolation (Boom! Boom!), without being specifically 'tweaked' to the actual circuits will always give a bit of a ragged response but a voltage boost they certainly will give!
Otherwise how have all those valve pre amps worked for the last near century?
Dave.
Re: Audio interface line input level
As I said:
I think we are all agreed, even without the sums, that a step-up transformer wouldn't be appropriate for the OP's specific application, but there are applications where step-up transformers can be -- and routinely are -- used to boost signal levels passively.
Again, as I said, dynamic mics, especially ribbons, rely on it. As do some moving-coil pickup preamps. And quite a few outboard processors and mixing consoles rely on step-up output transformers to provide the required pro output level (usually 1:2 ratios, for a 6dB boost).
So it is incorrect to claim "passive circuits can't boost a signal". They can, in certain correctly-engineered circumstances, which I feel is an important educational and practical point which warranted correction.
Hugh Robjohns wrote:The fixed level line inputs in the 8i6 have an impedance of 44k, apparently, but your argument is entirely valid. Step-up transformers tend to be used with (relatively) high-impedance inputs for the practical reasons you state
I think we are all agreed, even without the sums, that a step-up transformer wouldn't be appropriate for the OP's specific application, but there are applications where step-up transformers can be -- and routinely are -- used to boost signal levels passively.
Again, as I said, dynamic mics, especially ribbons, rely on it. As do some moving-coil pickup preamps. And quite a few outboard processors and mixing consoles rely on step-up output transformers to provide the required pro output level (usually 1:2 ratios, for a 6dB boost).
So it is incorrect to claim "passive circuits can't boost a signal". They can, in certain correctly-engineered circumstances, which I feel is an important educational and practical point which warranted correction.
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- Hugh Robjohns
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(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
Re: Audio interface line input level
Wow, Thanks for all the replies! Much appreciated!
Ef37a - yep, you hit the nail on the head, it's when headphone monitoring that I have the problem. With my speakers (ae22's) I can turn everything else down a bit and crank the speakers, but on headphones (hd650) it starts to get too quiet. And I live in a one bed flat, so headphones are often my only option.
Hugh - you found the solution! That's exactly the sort of thing i'd been looking for, but I kept getting home stereo type results that didn't quite fit because I didn't know quite what to search for. Cheers!
Two cleanbox pro's should sort me out. I have a rat's nest of a set up based around a guitar, bass, bass-station, a bunch of cheap pedals and 5 axoloti's which are synth/fx/drum machine/sequencers/loopers/samplers, depending on what i've got loaded in them. They put out a similar level to the bass-station, maybe even quieter, so they should benefit too.
Regarding the rest of the interface, I'm really happy with it, it sounds ace, and recordings are clean. I thought the 'air' setting would be a gimmick, but it seems to really open up my muddy-high-gain-humbucker strat.
The passive solution was a bit of a stretch, but if you don't ask... Thanks all for the science part, it's interesting, though i will have to re read to fully understand.
Cheers,
Matt
Ef37a - yep, you hit the nail on the head, it's when headphone monitoring that I have the problem. With my speakers (ae22's) I can turn everything else down a bit and crank the speakers, but on headphones (hd650) it starts to get too quiet. And I live in a one bed flat, so headphones are often my only option.
Hugh - you found the solution! That's exactly the sort of thing i'd been looking for, but I kept getting home stereo type results that didn't quite fit because I didn't know quite what to search for. Cheers!
Two cleanbox pro's should sort me out. I have a rat's nest of a set up based around a guitar, bass, bass-station, a bunch of cheap pedals and 5 axoloti's which are synth/fx/drum machine/sequencers/loopers/samplers, depending on what i've got loaded in them. They put out a similar level to the bass-station, maybe even quieter, so they should benefit too.
Regarding the rest of the interface, I'm really happy with it, it sounds ace, and recordings are clean. I thought the 'air' setting would be a gimmick, but it seems to really open up my muddy-high-gain-humbucker strat.
The passive solution was a bit of a stretch, but if you don't ask... Thanks all for the science part, it's interesting, though i will have to re read to fully understand.
Cheers,
Matt