Vintage Silicon
#16 Re: Vintage Silicon
Most of the DACs I have built have. or are able to have, differential/balanced (ought to find out the difference) outputs, typically with transformers or because they're balanced voltage out devices. It makes sense to have the option to use that balanced capability so I thought I would make a new buffered passive 'pre-amp' using my remaining four BUF-03 devices (and, obviously, a suitable attenuator).
Here's a schematic of the single-ended BUF-03 buffer;
I'm thinking I'll just double up on the buffers so that there's one on each hot/cold signal line or is that simplicity exposing my lack of knowledge about these things? I'm assuming DC offset would still need to be nulled on each line realtive to ground.
Any advice/observations will be greatfully received.
Here's a schematic of the single-ended BUF-03 buffer;
I'm thinking I'll just double up on the buffers so that there's one on each hot/cold signal line or is that simplicity exposing my lack of knowledge about these things? I'm assuming DC offset would still need to be nulled on each line realtive to ground.
Any advice/observations will be greatfully received.
Sorry, I couldn't resist!
#17 Re: Vintage Silicon
That's sort of the point with balanced, there is no ground just the difference between the two lines.I'm assuming DC offset would still need to be nulled on each line realtive to ground.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
#18 Re: Vintage Silicon
Thanks Nick.
Methinks I should've had more coffee before posting the question; I do understand the basic principle of having the two lines so that the differntial signals cancel common mode noise, although, to be honest I had always assumed pin1 of an XLR to be ground.
I'll have a think and try again.
Methinks I should've had more coffee before posting the question; I do understand the basic principle of having the two lines so that the differntial signals cancel common mode noise, although, to be honest I had always assumed pin1 of an XLR to be ground.
I'll have a think and try again.
Sorry, I couldn't resist!
#19 Re: Vintage Silicon
Pin 1 is connected to the shield of the cable, but the pin inside the equipment is connected to ground, chassis, signal ground or nothing varies. Also don't assume that ground is voltage wise between the hot and cold pin, consider phantom power.although, to be honest I had always assumed pin1 of an XLR to be ground
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
#20 Re: Vintage Silicon
I've been having a think about this and have concluded that I was asking the wrong questions.
It is true that most of my source components are equipped with balanced outputs (or could be very easily) but I allowed my thinking to be muddied by a discussion about the input stage of the Mellow OTL amp (on the 'Beginners' topic), which is able to take a balannced input that is likely to yeald better results than the single-ended option. The reality is that I haven't build a Mellow OTL amp so it's all hypothetical whereas the amps I have working (or in progress) all have single ended inputs. So the question is actually about using balanced sources with single-ended amplifiers.
I want the ability to use an analogue attenuator (rather than relying on digital volume control) and I have a balanced passive attenuator so what I believe I actually need is a buffer stage that'll take the outputs from the balanced attenuator and convert them to single-ended to drive my single-ended amplifiers.
If the Mellow OTL ever becomes a reality I could just put a suitable balanced attentuator on its inputs.
I'll start to look out for a balanced to single-ended unity-gain buffer and start a new thread in due course.
It is true that most of my source components are equipped with balanced outputs (or could be very easily) but I allowed my thinking to be muddied by a discussion about the input stage of the Mellow OTL amp (on the 'Beginners' topic), which is able to take a balannced input that is likely to yeald better results than the single-ended option. The reality is that I haven't build a Mellow OTL amp so it's all hypothetical whereas the amps I have working (or in progress) all have single ended inputs. So the question is actually about using balanced sources with single-ended amplifiers.
I want the ability to use an analogue attenuator (rather than relying on digital volume control) and I have a balanced passive attenuator so what I believe I actually need is a buffer stage that'll take the outputs from the balanced attenuator and convert them to single-ended to drive my single-ended amplifiers.
If the Mellow OTL ever becomes a reality I could just put a suitable balanced attentuator on its inputs.
I'll start to look out for a balanced to single-ended unity-gain buffer and start a new thread in due course.
Sorry, I couldn't resist!
#21 Re: Vintage Silicon
I finally got around to reworking my buffered passive to make use of the Academy Audio Muses volume control module I have available. Still some stuff to do to reinstall the power supply but tested it on the bench today with a temporary hook-up and it's coming together well. The Muses unit has an LED display and remote control sensor and I've experimented with having a front panel 3D printed to accomodate them - quite pleased and the textured finish you get with 3D printing looks quite nice - I'll use 3D printing again!
Sorry, I couldn't resist!
- pre65
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#22 Re: Vintage Silicon
The front panel screw looks wrong, should it be a countersunk type ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#23 Re: Vintage Silicon
Yep, the countersinks are actually for allen bolts - didn't have them to hand when I was putting it together to test.
Sorry, I couldn't resist!
#24 Re: Vintage Silicon
To be more helpful
https://www.mouser.co.uk/datasheet/2/40 ... 532288.pdf
Yes, you could but by doing that you are not taking advantage of the balanced nature of the signal. If you used something like a THAT 1200 or a transformer you would get the advantage of the cancellation of errors and ignoring any DC offset (up to 12v with the THAT part).I'm thinking I'll just double up on the buffers so that there's one on each hot/cold signal line or is that simplicity exposing my lack of knowledge about these things? I'm assuming DC offset would still need to be nulled on each line relative to ground.
https://www.mouser.co.uk/datasheet/2/40 ... 532288.pdf
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
#25 Re: Vintage Silicon
Thanks Nick, that looks interesting and helpful - I'll have a proper read later as (proper) balanced operation is still something that is of interest.
It'll not be with the BUF-03s though as, apart from this buffered passive preamp project, I've reserved the remainder of them (including a couple of spares) for use in the preamp I'm working on for the MoFo/OB project. That preamp will use, after the volume control, 2P29L valves to give around 20dB gain for the MoFo but I'm also including a second set of outputs after the volume control, buffered with the BUF-03s, to feed the LP filter/bass amplifier. In essence I'm putting active and buffered passive 'preamps' together in one chassis so it will be quite versatile for other use cases.
Although I'm not currently using the balanced operation possibility, the fact that my DSD DACs have transformer coupled outputs is useful as it means the Muses volume control module shouldn't see any DC offset on its input, eliminating the need for (electrolytic) caps there.
It'll not be with the BUF-03s though as, apart from this buffered passive preamp project, I've reserved the remainder of them (including a couple of spares) for use in the preamp I'm working on for the MoFo/OB project. That preamp will use, after the volume control, 2P29L valves to give around 20dB gain for the MoFo but I'm also including a second set of outputs after the volume control, buffered with the BUF-03s, to feed the LP filter/bass amplifier. In essence I'm putting active and buffered passive 'preamps' together in one chassis so it will be quite versatile for other use cases.
Although I'm not currently using the balanced operation possibility, the fact that my DSD DACs have transformer coupled outputs is useful as it means the Muses volume control module shouldn't see any DC offset on its input, eliminating the need for (electrolytic) caps there.
Sorry, I couldn't resist!
#26 Re: Vintage Silicon
Finished of my BUF-03 equipped buffered passive 'preamp' this morning - nulled the DC offset of the buffer stage and had a listen with headphones - sounds good and no pops or other nasties (I omitted the DC blocking caps from the volume control) - just letting it cook before final adjustment of the DC offset and fitting the top of the enclosure.
For info, it's equipped with an Academy Audio Muses volume control with remote control (volume, balance, mute) and the power supply is a Jan Didden 'Silent Switcher' (+/-15VDC from a 5V wallwart).
I'm now using countersunk allen bolts to fit the front panel to keep Phil happy.
For info, it's equipped with an Academy Audio Muses volume control with remote control (volume, balance, mute) and the power supply is a Jan Didden 'Silent Switcher' (+/-15VDC from a 5V wallwart).
I'm now using countersunk allen bolts to fit the front panel to keep Phil happy.
Sorry, I couldn't resist!
- pre65
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#27 Re: Vintage Silicon
Allen set screws ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#28 Re: Vintage Silicon
??? Aren't set screws headless
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
#29 Re: Vintage Silicon
The packaging says 'Countersunk Allen Bolts' so that'll do me.
I know set screws as grub screws so I'm with Steve.
I know set screws as grub screws so I'm with Steve.
Sorry, I couldn't resist!
- pre65
- Amstrad Tower of Power
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- Location: North Essex/Suffolk border.
#30 Re: Vintage Silicon
No, a bolt is only partially threaded but a set screw is threaded it's entire length.
Headless threaded thingies could be grub screws.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)