A few weeks ago, a pair of Keltiks crossed my path, and although I hadn't planned of getting any just yet, I couldn't help myself and went and bought them anyway. I already have a pair of Keilidhs I've been planning to turn active, so I already have more amps than I can use right now. My original plan was to use a miniDSP to make a sort of diy Exakt system.
However, the speakers came with a set of Aktiv Stereo cards which I figured I could use to start with. Now these are made to fit in Linns AV5125, 2250 and LK85/140 amps, which I don't have. So I thought I could put together my own Tunebox. The first thing I found was a thread on this site where Fredrik suggested the voltage required to supply power to the cards are around 20 Volts. Well it turns out that I can get +/- 21V from the pre-amp section of my old surround amp. So now my plan is to put the cards in the amp and hotwire them there and then use four channels to run the isobarik woofers, and send the other channels to two external amps.
And now to my problem. And I have to make a n00b alert here, since I'm not formally trained and experienced in electronics. I don't want to ruin any cards or amps so I have breadboarded the cards to see if they work as they should. So I connected them up and measured the voltages. There are check points on the board marked 0V, -15V and +15V. But when I feed the cards 21V I only measure between 7,5-10V on the check points for the different cards. Why is this? It would make sense that I get the stated 15 Volts right?
When I trace the cards I can see that they first pass two parallelled 470 Ohm resistors before entering the LM317/337. So when I measure before the resistors, I do get 21 V on the boards. But between the resistors and the regulators it's down to 10-12 Volts. AFAIK the regulators would need a few volts higher supply than their regulated output, right? What am I missing here?
However, the speakers came with a set of Aktiv Stereo cards which I figured I could use to start with. Now these are made to fit in Linns AV5125, 2250 and LK85/140 amps, which I don't have. So I thought I could put together my own Tunebox. The first thing I found was a thread on this site where Fredrik suggested the voltage required to supply power to the cards are around 20 Volts. Well it turns out that I can get +/- 21V from the pre-amp section of my old surround amp. So now my plan is to put the cards in the amp and hotwire them there and then use four channels to run the isobarik woofers, and send the other channels to two external amps.
And now to my problem. And I have to make a n00b alert here, since I'm not formally trained and experienced in electronics. I don't want to ruin any cards or amps so I have breadboarded the cards to see if they work as they should. So I connected them up and measured the voltages. There are check points on the board marked 0V, -15V and +15V. But when I feed the cards 21V I only measure between 7,5-10V on the check points for the different cards. Why is this? It would make sense that I get the stated 15 Volts right?
When I trace the cards I can see that they first pass two parallelled 470 Ohm resistors before entering the LM317/337. So when I measure before the resistors, I do get 21 V on the boards. But between the resistors and the regulators it's down to 10-12 Volts. AFAIK the regulators would need a few volts higher supply than their regulated output, right? What am I missing here?
It wasn't that expensive! I have a set of Linn Kelidh's which are biamped with a Linn integrated amplifier and another straight amplifier.
The Linn integrated amplifier used an STK "chip-amp". The 100W Linn amp used LM317/337 , hardly SOTA even back then.
Had I known then what I know now...never would have used any Linn electronics. The LP12 revolver is just fine after all these years, however.
I abandoned that idea and decided to use an external pro audio active crossover instead. I realized that I wasn't experienced enough to figure out how to build a DIY Tunebox. Though I might eventually buy used Linn amplifiers that take the cards.
I have a LK140 now, and if I get a AV5125 I can fit the card in the amps to see if the Linn active cards sound better than what I can set in my current external crossover.
I have used a Behringer CX3400 up until now, and used a mix of LK140 for the treble, a Cambridge Azur 540 for midrange and a Audiolab 8000A for the woofers. It's been working fine but I use an old Yamaha AV receiver as a pre-amp and I believe I can improve a lot by using a better pre-amp/dac.
Last week I got a Behringer DCX2496 and I'm tinkering with it right now. I just swapped it with the analog crossover. But I want to take the digital signal straight to the crossover. Much like an Exakt system. I just don't know how to implement a digital volume control in the signal chain. Anyone who can help me with this?
I have a LK140 now, and if I get a AV5125 I can fit the card in the amps to see if the Linn active cards sound better than what I can set in my current external crossover.
I have used a Behringer CX3400 up until now, and used a mix of LK140 for the treble, a Cambridge Azur 540 for midrange and a Audiolab 8000A for the woofers. It's been working fine but I use an old Yamaha AV receiver as a pre-amp and I believe I can improve a lot by using a better pre-amp/dac.
Last week I got a Behringer DCX2496 and I'm tinkering with it right now. I just swapped it with the analog crossover. But I want to take the digital signal straight to the crossover. Much like an Exakt system. I just don't know how to implement a digital volume control in the signal chain. Anyone who can help me with this?
If you want to do attenuation in the digital world you have many choices. You can use any 24-bit or 32-bit DSP to do it, or you can rely on a DAC that has this feature. Of course if you are going active digital crossovers then you will have more than the usual number of DAC channels to manage.
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