Hello all DIYers!
I'm having a preamplifier project going on (I am not the only one, I guess 🙂). At first I thought the preamp would have semiconductor input switches and volume control (MAX4662 and CS3310), but then I looked at the Pass Labs Aleph P 1.0 service manual and saw how simplified the input switching and volume control was. Now I'm re-considering my own preamp design and I have some questions:
1. What kind of relays you would use for audio switching (of what brand / model).
2. Wouldn't the relays be really stressed when used in volume controlling (especially the "LSB" relay)? Do they last? Do I have to be afraid of connection failures and "static" in the sound?
3. Hasn't the development in solid state switches made them an alternative worth considering (recent switches have on resistance something like 2.5 ohms or less)?
Thanks in advance
Janne
ps. My first post here 🙂
I'm having a preamplifier project going on (I am not the only one, I guess 🙂). At first I thought the preamp would have semiconductor input switches and volume control (MAX4662 and CS3310), but then I looked at the Pass Labs Aleph P 1.0 service manual and saw how simplified the input switching and volume control was. Now I'm re-considering my own preamp design and I have some questions:
1. What kind of relays you would use for audio switching (of what brand / model).
2. Wouldn't the relays be really stressed when used in volume controlling (especially the "LSB" relay)? Do they last? Do I have to be afraid of connection failures and "static" in the sound?
3. Hasn't the development in solid state switches made them an alternative worth considering (recent switches have on resistance something like 2.5 ohms or less)?
Thanks in advance
Janne
ps. My first post here 🙂
Hi there Janne,
Good luck in your preamplifier. The use of a relay is a very good idea. You don´t have to worry about any stresses on the relays. The currents are so small you won´t have any problems. So don´t use big relays rated 5-10A. You can use ones rated at 1-2A. Try to find relays that are sealed from the enviroment like omron or siemens have . They are small in size and a few models are offered with gold or rhodium contacts for very long life. So if you find sealed relays with good contact material thats what you need.
About semiconductors, now that hard to say. They don´t seem to have the sound of simple circuits even if theoreticaly they are perfect. They are never used in high end circuits.
Anyway good luck again
Greetings
Ilias
Good luck in your preamplifier. The use of a relay is a very good idea. You don´t have to worry about any stresses on the relays. The currents are so small you won´t have any problems. So don´t use big relays rated 5-10A. You can use ones rated at 1-2A. Try to find relays that are sealed from the enviroment like omron or siemens have . They are small in size and a few models are offered with gold or rhodium contacts for very long life. So if you find sealed relays with good contact material thats what you need.
About semiconductors, now that hard to say. They don´t seem to have the sound of simple circuits even if theoreticaly they are perfect. They are never used in high end circuits.
Anyway good luck again
Greetings
Ilias
volume ctrl
Hi,
i find the aleph P 1.0 volume control very interesting.
It seems to be much simpler than the P 1.7's.
ADC0804 is a cheap 8-bit AD-Converter and the investment in 6 relays per channel seems reasonable.
Unfortunately the drive circuit is not shown in the service manual.
Service Manual location:
http://www.passlabs.com/pdf/Apserv10.pdf
volume ctrl circuit is on page 7.
What kind of input is expected on the "Ref B" input?
How can you make this attenuator move one step up and down?
The only thing that i want is a remote controlled ladder attenuator that can do without complex control computer etc (or at least i don't want to build the control computer).
I would use a kit remote control/receiver.
Any pointers to similar projects are appreciated.
Thanks,
Timo
Hi,
i find the aleph P 1.0 volume control very interesting.
It seems to be much simpler than the P 1.7's.
ADC0804 is a cheap 8-bit AD-Converter and the investment in 6 relays per channel seems reasonable.
Unfortunately the drive circuit is not shown in the service manual.
Service Manual location:
http://www.passlabs.com/pdf/Apserv10.pdf
volume ctrl circuit is on page 7.
What kind of input is expected on the "Ref B" input?
How can you make this attenuator move one step up and down?
The only thing that i want is a remote controlled ladder attenuator that can do without complex control computer etc (or at least i don't want to build the control computer).
I would use a kit remote control/receiver.
Any pointers to similar projects are appreciated.
Thanks,
Timo
what is not shown ?? the layout hmm ref b is from the PS thik it is 9,1 or 18,2 V from the zener stack...
if any body decides to draw a layout for the AD chip...plz mail it to me on hifi@hotbrev.com
/micke
if any body decides to draw a layout for the AD chip...plz mail it to me on hifi@hotbrev.com
/micke
The Sutherland Engineering Preamp uses the MAX335 serial switch for switching instead of relays and for volume control uses the LM1972. The only draw back is you will have to program a microcontroller to control both.
I have been told that the "Build Your
Own High-End Audio Equipment" book, available
through Old Coloney Sound Labs has some good volume
control schematics
For what its worth.
I have been told that the "Build Your
Own High-End Audio Equipment" book, available
through Old Coloney Sound Labs has some good volume
control schematics
For what its worth.
Hi Micke,
Ok, only a voltage on Ref B. Fine.
And you adjust volume with what? The 100 k pot??
Regards
Timo
Ok, only a voltage on Ref B. Fine.
And you adjust volume with what? The 100 k pot??
Regards
Timo
to my understandign yes...if you draw (a working) layout of the input part plz mail it to me on hifi@hotbrev.com
/micke
/micke
- Status
- Not open for further replies.
- Home
- Amplifiers
- Solid State
- About volume control and input switching