Going down the rabbit hole of DIY-ish stereo passive preamps. Because of my room layout, I need (some kind of) balance control. I'm fine with using two Alps pots, for example. But would like to have remote. Best I've found is the latest Tortuga, and I'm sunk into the LDR 'debate' - not enjoying, but understand it's part of the territory. I think there's a SMD resistor option. But I'd be happy enuf with a pair of motorized Alps, controlled by one remote (or two merged into a universal remote). Seems like a kludgy workaround, so i'm wide open to suggestions. Are there options out that I'm missing? Or any other ideas/vendors/sources? Thanks!!
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'Passive Preamp' Recommendation? - with remote and balance control
- Thread starter Lego
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AnalogSteph
Major Contributor
In a nutshell - don't.
Do you know the expression "cut off your nose to spite your face"? That's kind of what "passive (non-)preamps" are about, eliminating a potential problem by introducing some rather bigger ones. (Most importantly, a tradeoff between input and worst-case output impedance that'll get at most decent. With how good analog circuitry can be these days, any fear of it definitely is not warranted.)
And LDR attenuators? Well, those can be rather lo-fi indeed.
Instead of worshipping at the altar of the hi-fi gods (and I do mean that quite literally), what about identifying your needs and researching adequate solutions from there? Audio playback may seem like magic but it definitely isn't.
A balance control is no doubt effective but crude, a very 1980s kind of solution. We can do much better when dealing with room acoustic problems these days. In order to proceed, more information about your room / speakers and an idea of existing playback equipment to be integrated and a budget would be very useful.
Do you know the expression "cut off your nose to spite your face"? That's kind of what "passive (non-)preamps" are about, eliminating a potential problem by introducing some rather bigger ones. (Most importantly, a tradeoff between input and worst-case output impedance that'll get at most decent. With how good analog circuitry can be these days, any fear of it definitely is not warranted.)
And LDR attenuators? Well, those can be rather lo-fi indeed.
Instead of worshipping at the altar of the hi-fi gods (and I do mean that quite literally), what about identifying your needs and researching adequate solutions from there? Audio playback may seem like magic but it definitely isn't.
A balance control is no doubt effective but crude, a very 1980s kind of solution. We can do much better when dealing with room acoustic problems these days. In order to proceed, more information about your room / speakers and an idea of existing playback equipment to be integrated and a budget would be very useful.
I second every word that @AnalogSteph wrote.
- Thread Starter
- #4
I have two monoblock amps. With regards to room layout, I'm in a smallish flat in urban environment, and my computer source(s) and Thorens table, amps along the west of living room and kitchen (another listening position) on the east, projector screen on the north wall behind/between speakers. I rarely sit and listen to music in the southern sofa sweet spot, so i seldom adjust volume, without left/right biasing the speakers depending where i'm doing my activity, which may involve both passive and active listening. This is an architectural (immovable) limitation/challenge and not strictly 'audiophile' - It's also one that may be shared by others. I'm merely seeking a pragmatic solution to my remote/balance needs (as above), which i may have overlooked in the marketplace - real or ideas.
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- Thread Starter
- #5
I only begrudgingly got into the LDR 'world' because that's the technology that Tortuga highlights, and I am considering Tortuga only because it the only vendor that i've found that has any semblance of a feature combination of remote-control/balance. That's why I'm here to ask if anybody else knows of a device that has those feature combination (and not many other features/functions are necessary/desired), or some DIY workaround. technically I'm not really seeking a 'balance' control, rather 2 independent pots, that can be remote controlled with one device. thanks
As far as impedence considerations, it's over my head - what i know is that i've liberated these sizable amps from a receiver*, bypassed pre, and they sound MUCH more alive even with the low-end pair of pots i'm using now. My goal is to replicate with better pots and remote control. *recapped beomaster 8000 - considerable (14 kilograms?) power supply and 150wpc into 4ohms
As far as impedence considerations, it's over my head - what i know is that i've liberated these sizable amps from a receiver*, bypassed pre, and they sound MUCH more alive even with the low-end pair of pots i'm using now. My goal is to replicate with better pots and remote control. *recapped beomaster 8000 - considerable (14 kilograms?) power supply and 150wpc into 4ohms
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What's LDR?
mhardy6647
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Light Dependent Resistor
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My Adcom GFP-750 has balance and volume via remote in active mode. It's a 20yo preamp though, but it's really solidly built if you can find one. Remote balance is pretty hard to find.
Hi Lego,
I have owned a Tortuga LDR preamp for a few years. One of the strengths of Tortuga is the marriage of impedance which is automatically adjusted with an algorithms specific to Tortuga.
Sometimes the marriage of impedance and other times not quite.
I sold it and I will not go back. I find the sound a bit dull, lacking in dynamics and definition.
I find an active buffer like the DCB1 (conception Nelson Pass) to be far superior, mine is a DIY mount made from a quality PCB. But there is no scale. It won't be easy to find one.
In your place I would look for a quality active preamp.
I have owned a Tortuga LDR preamp for a few years. One of the strengths of Tortuga is the marriage of impedance which is automatically adjusted with an algorithms specific to Tortuga.
Sometimes the marriage of impedance and other times not quite.
I sold it and I will not go back. I find the sound a bit dull, lacking in dynamics and definition.
I find an active buffer like the DCB1 (conception Nelson Pass) to be far superior, mine is a DIY mount made from a quality PCB. But there is no scale. It won't be easy to find one.
In your place I would look for a quality active preamp.
DSJR
Major Contributor
S'cuse me for butting in, but the LDR preamps I've seen are so complex on the power supplies to power the things to work in as linear a way as possible, it kind-of makes a joke of the entire 'passive' concept, especially when a 10k plastic Omeg pot (couple of quid each) can 'sound' so transparent and only fails in the bottom ten degrees of travel when channel imbalances can occur (shunt style attenuators are claimed to be superior to this, but my concern is the impedance matching swings with each 'step' on the things so each volume 'step' is basically a bodge I reckon).
A shame they abandoned the solid state option, at least for now, but a Schiit Saga+ or Freya+ may be all you really need here as the latter at least offers active or passive operation and isn't hugely expensive on its home market at least.
A shame they abandoned the solid state option, at least for now, but a Schiit Saga+ or Freya+ may be all you really need here as the latter at least offers active or passive operation and isn't hugely expensive on its home market at least.
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It seems to me that the key thing here is that the remote should be able to adjust parameters that optimise the listening experience from a number of (non-ideal) listening positions throughout the space - correct?
I'm not sure how sophisticated you want to go, but a more effective solution would be to use a DSP unit with multiple inputs and remote control that can be pre-configured with a number of presets that adjust not only L/R balance, but also delay (and also amplitude and phase response, if you wanted to get more technical with it).
There are a few products on the market that would do the job very well. Given your budget seems to be about $1-2k (?), the obvious choice would be the MiniDSP SHD. I would run the PC via the SHD's digital inputs and the TT preamp via its analogue inputs. The unit comes with an excellent little measurement microphone, which will allow you to take the acoustic measurements necessary to optimise the system for each of the various listening positions.
If $1200 is over-budget, there are numerous cheaper options available that would do the job 99% as well, e.g. MiniDSP 2x4 HD, which costs about $280 once you include the measurement mic.
vintagemaniac
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I've bien living quite happily for some time with this : selectable passive/active (then 100 R output impedance) , dual vol control w/remote and luxury resistor ladder pot inside, nice enough looks and build to my taste : http://www.hattor.com/dualmono_preamp_the_big.html
Sure, with the Hattor you can turn off the output opamp stage (which I don't recommend since it levels output impedance while being dead silent) and you've got a passive unit with remote and stuff !
Hi @Fledermaus
Sometime ago I would be looking for such a device.
I'm wondering what are you connecting to your preamp; I mean do you need a preamp ?
Who would need a preamp ? 
I use it to concentrate analog sources such as CD player (used once in a while) and FM tuner (used almost daily), on top of streaming DAC, and to have shared volume management and source selection for everything with one remote - convenience !
In fact I could go radical, ditch a number of boxes including DAC and go direct from RPi to DSP/active Xover's USB input, - but I like stacking gear !
I use it to concentrate analog sources such as CD player (used once in a while) and FM tuner (used almost daily), on top of streaming DAC, and to have shared volume management and source selection for everything with one remote - convenience !
In fact I could go radical, ditch a number of boxes including DAC and go direct from RPi to DSP/active Xover's USB input, - but I like stacking gear !
MRC01
Major Contributor
If you construct a passive attenuator using a standard voltage divider layout with metal film resistors, and your sources have low output impedances, and your destinations have high input impedances, then it may have lower noise and distortion than an active preamp. Especially at the low to medium volume levels we normally use for listening (-20 to -40 dB from full scale). With perfectly flat frequency response through the audible spectrum. And perfect L-R channel balance at every setting, something analog pots don't achieve.
Calculations and examples on which I base my opinion are here.
In summary, if the basic requirement for transparency is 1:10 impedance ratios on both sides (source to passive input, and passive output to destination), then a 5k attenuator meets that goal for most systems with solid state devices. That is, most sources have < 500 ohm output impedance, and most destinations have > 12500 ohm input impedance.
However, I understand the advice to avoid passives. It has a pragmatic sensibility. An active preamp is more "plug and play", doesn't require the impedance matching, and if they have higher noise and worse channel balance than a passive, the difference may not be audible. And the best active preamps have noise performance that equals or exceeds what a passive can do, like the Topping A90 Amir reviewed here.
Calculations and examples on which I base my opinion are here.
In summary, if the basic requirement for transparency is 1:10 impedance ratios on both sides (source to passive input, and passive output to destination), then a 5k attenuator meets that goal for most systems with solid state devices. That is, most sources have < 500 ohm output impedance, and most destinations have > 12500 ohm input impedance.
However, I understand the advice to avoid passives. It has a pragmatic sensibility. An active preamp is more "plug and play", doesn't require the impedance matching, and if they have higher noise and worse channel balance than a passive, the difference may not be audible. And the best active preamps have noise performance that equals or exceeds what a passive can do, like the Topping A90 Amir reviewed here.
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Who would need a preamp ?
I use it to concentrate analog sources such as CD player (used once in a while) and FM tuner (used almost daily), on top of streaming DAC, and to have shared volume management and source selection for everything with one remote - convenience !
In fact I could go radical, ditch a number of boxes including DAC and go direct from RPi to DSP/active Xover's USB input, - but I like stacking gear !
Thanks, I thought you chose it because of other, then source management reasons.
I made my resistor based attenuator before but not so happy about it. Above @MRC01 's post and impedance match could be a reason.
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