I've considered the DACT attenuator before. But four gang pots are rather expensive (for balanced input). And it's also impossible to implements remote control.
Over the weekend, I've done further simulation of the circuit.
In order to accept higher input voltage swing, R4 must be lowered to 2K. This means higher current will be drown from the multiplexer which is not a good idea. When the multiplexer fail, the input will not be attenuated at all! A second transistor will be needed to isolate the multiplexer.
With 60 transistors, 80 over resistors and buffer circuits (I've chosen Op-amps buffer), for one channel. I'm beginning to have second thought. Just think of the number of hole I'll have to drill! And on top of that, I will also need +/-15V, +/- 5 V and possibly a micro controller circuit to handle. Phew! The DACT is looking more attractive all the time!
Another thread has pop up in the Solid State forum regarding digital vol. control. Perhaps it is an easier way out.
Anyway, I am still interested to know more of the circuits and any comments, and suggestion is always welcome.
Thanks and regards,
Clemence
Over the weekend, I've done further simulation of the circuit.
In order to accept higher input voltage swing, R4 must be lowered to 2K. This means higher current will be drown from the multiplexer which is not a good idea. When the multiplexer fail, the input will not be attenuated at all! A second transistor will be needed to isolate the multiplexer.
With 60 transistors, 80 over resistors and buffer circuits (I've chosen Op-amps buffer), for one channel. I'm beginning to have second thought. Just think of the number of hole I'll have to drill! And on top of that, I will also need +/-15V, +/- 5 V and possibly a micro controller circuit to handle. Phew! The DACT is looking more attractive all the time!
Another thread has pop up in the Solid State forum regarding digital vol. control. Perhaps it is an easier way out.
Anyway, I am still interested to know more of the circuits and any comments, and suggestion is always welcome.
Thanks and regards,
Clemence
Clemence,
You said it was impossible to implement a remote control to the DACT attenuators. That's not true, Thel Audioworld in Germany sells a kit with a motor to drive the attenuator it costs about 69 Euro. When you have this it's easy to implement a remote control!!
Here's a link: (German page)
http://www.thel-audioworld.de/bauteile/regler/regler.htm
/Freddie
You said it was impossible to implement a remote control to the DACT attenuators. That's not true, Thel Audioworld in Germany sells a kit with a motor to drive the attenuator it costs about 69 Euro. When you have this it's easy to implement a remote control!!
Here's a link: (German page)
http://www.thel-audioworld.de/bauteile/regler/regler.htm
/Freddie
The patent has not yet been processed. It used to be
that we got fairly quick turn-around on applications,
that is to say a year or so, but the patent office
appears to have been overburdened with "business model"
applications and other dot-com craziness.
The advantage of this circuit over prior art is that
it has about 1/10 the noise, 1/10 the distortion, and
will handle 10 times the voltage swing. We intend to
license it to chip manufacturers as a replacement for
the CMOS circuits currently out there.
that we got fairly quick turn-around on applications,
that is to say a year or so, but the patent office
appears to have been overburdened with "business model"
applications and other dot-com craziness.
The advantage of this circuit over prior art is that
it has about 1/10 the noise, 1/10 the distortion, and
will handle 10 times the voltage swing. We intend to
license it to chip manufacturers as a replacement for
the CMOS circuits currently out there.
Re: Switched volume controls
Thank's Mark, but I got the original idea for the transistor/resistor based volume control from a look to the X0 by Nelson Pass.
I still think it works really great with a two stage topology I use for my preamp. It will not work with a single stage amplifier because you will need a lot of different resistor/transistor pairs for the different volume levels.
cheers,
Maik
Thank's Mark, but I got the original idea for the transistor/resistor based volume control from a look to the X0 by Nelson Pass.
I still think it works really great with a two stage topology I use for my preamp. It will not work with a single stage amplifier because you will need a lot of different resistor/transistor pairs for the different volume levels.
cheers,
Maik
I'm glad we got that sorted out. I did not mean to imply who got the idea from whom. I was suggesting that the XO might be using an electronic Shun Vol. Control. And if it's good enough for Pass Lab, then it certainly will be for me.
Now the next question is, can we implement the Shun Vol. Control without an extra stage? I was thinking of 3 x -20db steps before the Preamp and 20 x -1db steps after. We will then get 60 steps of attenuation with 23 switches instead of 16.
Any comments? I don't really like the idea of an extra buffer stage.
Thanks again for all your responds.
Best Regards
Clemence
Now the next question is, can we implement the Shun Vol. Control without an extra stage? I was thinking of 3 x -20db steps before the Preamp and 20 x -1db steps after. We will then get 60 steps of attenuation with 23 switches instead of 16.
Any comments? I don't really like the idea of an extra buffer stage.
Thanks again for all your responds.
Best Regards
Clemence
Clemence,
the reason for the two amplifying stages in my preamp are
the following:
1. for the 10db steps you will need a high ohmic resistor in series with the signal path. The input capacitance of the mosfet in your first amplifying stages is driven by this high ohmic resistor. I tried to drive a power mosfet (irf610) with 10k and I did not like it. Therefor I decided to use a small signal double fet in the input stage.
2. If you drop the second amplifying stage, you must drive the output load through the series resistor for the 1db steps. This resistor can be much smaller but If you like to drive some long cables to your power amplifier it might influence the performance of the system. I use loudspeakers with an active cross over and 4 power amplifiers. The cables are about 5 meters long. I experimented with a lot of preamp topologies and finally I found that in my ears (and my system) the two stage approach is the best.
Regards,
Maik
the reason for the two amplifying stages in my preamp are
the following:
1. for the 10db steps you will need a high ohmic resistor in series with the signal path. The input capacitance of the mosfet in your first amplifying stages is driven by this high ohmic resistor. I tried to drive a power mosfet (irf610) with 10k and I did not like it. Therefor I decided to use a small signal double fet in the input stage.
2. If you drop the second amplifying stage, you must drive the output load through the series resistor for the 1db steps. This resistor can be much smaller but If you like to drive some long cables to your power amplifier it might influence the performance of the system. I use loudspeakers with an active cross over and 4 power amplifiers. The cables are about 5 meters long. I experimented with a lot of preamp topologies and finally I found that in my ears (and my system) the two stage approach is the best.
Regards,
Maik
The Balance Line Stage Pre-Amp article indicates a total of 10 potentiometers for 2 channels.
1. Has anybody ordered the potentiometers from DigiKey as indicated in the article?
2. Does those potentiometers have the provision to be able to be clamp together? I hope it does. e.g. Four potentiometers to form a output volume control and another four for the input. It would look rather silly and inconvenient to have 10 potentiometers sticking out of the face plate! Two looks reasonable.
3. If they can't be clamped together, what are the options for a balanced potentiometers?
I have looked into DACT (CT-1) attenuators that Tony D. suggested but those are so expensive! It's close to $250 for one balanced VR and I think 5K VR is not even available.
I'm hoping to get some feedback on how you guys handle this.
Thanks in advance.
1. Has anybody ordered the potentiometers from DigiKey as indicated in the article?
2. Does those potentiometers have the provision to be able to be clamp together? I hope it does. e.g. Four potentiometers to form a output volume control and another four for the input. It would look rather silly and inconvenient to have 10 potentiometers sticking out of the face plate! Two looks reasonable.
3. If they can't be clamped together, what are the options for a balanced potentiometers?
I have looked into DACT (CT-1) attenuators that Tony D. suggested but those are so expensive! It's close to $250 for one balanced VR and I think 5K VR is not even available.
I'm hoping to get some feedback on how you guys handle this.
Thanks in advance.
Fcel,
There are two positions to control the Preamp’s Volume. P1/P2 at the input side and/or P3/P4 at the output. P5 is used to vary the gain of the circuit and can be omitted. Just swap R15 around to get your required gain. Once fixed, you rarely have to change it again. I use 330 ohm. There is no need to use all of them at the same time.
If you intends to implements balanced input/out, then I would suggest that you use a 10K 4-gang pot. at the input. 5K one are hard to come by and can be left out. However, If you don’t need balanced Input, then any dual gang 10K log pots will do fine at the input side. Just remember to tie the negative input to ground.
Maik,
Thanks for your response.
If time permit, I will try a simple cascode version (not the folded cascode of the X series) of the BZLS. The reduced input capacitance will mean a wider choice of volume control configurations. Hope it sound as good or even better than the original.
Clemence
There are two positions to control the Preamp’s Volume. P1/P2 at the input side and/or P3/P4 at the output. P5 is used to vary the gain of the circuit and can be omitted. Just swap R15 around to get your required gain. Once fixed, you rarely have to change it again. I use 330 ohm. There is no need to use all of them at the same time.
If you intends to implements balanced input/out, then I would suggest that you use a 10K 4-gang pot. at the input. 5K one are hard to come by and can be left out. However, If you don’t need balanced Input, then any dual gang 10K log pots will do fine at the input side. Just remember to tie the negative input to ground.
Maik,
Thanks for your response.
If time permit, I will try a simple cascode version (not the folded cascode of the X series) of the BZLS. The reduced input capacitance will mean a wider choice of volume control configurations. Hope it sound as good or even better than the original.
Clemence
Clemence,
Thanks for the response in regards to the 10 potentiometers. Could you direct me to a web site where I can purchase a 4 gang or 2 gang potentiometers (10K and 5K). I have a hard time locating them and I'm not ready for the DACT potentiometers yet.
In regards to the Balanced or Unbalanced operation, I'm trying to learn how Balanced circuit works. For unbalanced configuration - by tieing input/output to ground - doesn't that have the effect of putting half of the circuits/component to "sleep". If that is the case, I was wondering whether I should consider building the BOZ instead since my intent of use is strictly in unbalance mode - at least for the inputs. But then again, I have also learn on this forum that there is less "noise" in balanced mode which I think it's a good thing.
Thanks for the response in regards to the 10 potentiometers. Could you direct me to a web site where I can purchase a 4 gang or 2 gang potentiometers (10K and 5K). I have a hard time locating them and I'm not ready for the DACT potentiometers yet.
In regards to the Balanced or Unbalanced operation, I'm trying to learn how Balanced circuit works. For unbalanced configuration - by tieing input/output to ground - doesn't that have the effect of putting half of the circuits/component to "sleep". If that is the case, I was wondering whether I should consider building the BOZ instead since my intent of use is strictly in unbalance mode - at least for the inputs. But then again, I have also learn on this forum that there is less "noise" in balanced mode which I think it's a good thing.
Fcel,
For a balanced in/out, you will need step attenuator for precision tracking between the two phases. If you are not ready for that, then I suggest you use a 10K dual pot at the input. Leave out the 5K one. Tie only the input –ve to ground and connect the outputs for balanced operation. You now have an unbalanced to balanced converter. You may also use the output as unbalanced out.
Alps Pots are quite well received and inexpensive. Do a Google search and I’m sure you can come up with plenty of supplier.
Theories behind the Balanced circuit are very well explain in the origin article by Mr. Pass. Most notable benefit is the CMRR. Even if you use only unbalanced in/out, both side of the circuit is still working.
The BOZ and BZLS sound quite differently. I very much prefer the sound of the BZLS. Infect, my very first BZLS was created by joining two BOZ together. It sounded like a totally new beast and kept me excited for a couple of days.
Go ahead and build it. Enjoy!
Clemence
For a balanced in/out, you will need step attenuator for precision tracking between the two phases. If you are not ready for that, then I suggest you use a 10K dual pot at the input. Leave out the 5K one. Tie only the input –ve to ground and connect the outputs for balanced operation. You now have an unbalanced to balanced converter. You may also use the output as unbalanced out.
Alps Pots are quite well received and inexpensive. Do a Google search and I’m sure you can come up with plenty of supplier.
Theories behind the Balanced circuit are very well explain in the origin article by Mr. Pass. Most notable benefit is the CMRR. Even if you use only unbalanced in/out, both side of the circuit is still working.
The BOZ and BZLS sound quite differently. I very much prefer the sound of the BZLS. Infect, my very first BZLS was created by joining two BOZ together. It sounded like a totally new beast and kept me excited for a couple of days.
Go ahead and build it. Enjoy!
Clemence
Clemence,
I've received the two circuits boards that I orderd from AudioXpress today and I'm all ready to order the electrical parts.
I have been doing some searching on the internet for the 2 gang pot for the volume control but I could not seem to find any dealer in the States that sells them! I know, I know, I must have been searching for the wrong part!! I have seen Noble and Alps pots specification but I can't find any information on who sells them. I did not expect that it would be so difficult to find parts. Where did you get yours? I would really appreciate some input. Anyone?
I've received the two circuits boards that I orderd from AudioXpress today and I'm all ready to order the electrical parts.
I have been doing some searching on the internet for the 2 gang pot for the volume control but I could not seem to find any dealer in the States that sells them! I know, I know, I must have been searching for the wrong part!! I have seen Noble and Alps pots specification but I can't find any information on who sells them. I did not expect that it would be so difficult to find parts. Where did you get yours? I would really appreciate some input. Anyone?
Hi fcel,
Below are a few dealers that sell Volume Pot.
http://www.percyaudio.com/
http://www.sonicfrontiers.com/
http://www.thlaudio.com/
http://www.rs-components.com/
Go through the first two to get an ideal of what is available. You might get a better price from the next two suppliers.
Below are a few dealers that sell Volume Pot.
http://www.percyaudio.com/
http://www.sonicfrontiers.com/
http://www.thlaudio.com/
http://www.rs-components.com/
Go through the first two to get an ideal of what is available. You might get a better price from the next two suppliers.
Clemence,
I saw the pot that I needed at the Michael Percy Web site that you recommended. Hey, thanks for the help.
I've got the two transformers, the two circuit boards, other parts that are on the way and a junk metal case from my garage and I think I'll start drilling this weekend to get the project rolling!
I saw the pot that I needed at the Michael Percy Web site that you recommended. Hey, thanks for the help.
I've got the two transformers, the two circuit boards, other parts that are on the way and a junk metal case from my garage and I think I'll start drilling this weekend to get the project rolling!
Finally, I have received all the parts and have the balanced line stage pre-amp built to spec but without P3 & P4 and P5. I'm using 124 ohms for R15 and two of ALPS 2-gang 10K for P1 & P2. Currently, I'm using this pre-amp as unbalanced in/out and there is no hum or noise. I'm assuming that I do not have to short anything to ground even though I'm using it as unbalanced in/out.
I've not done any extensive listening to it yet but my first impression for now is that it's impressive!
I've not done any extensive listening to it yet but my first impression for now is that it's impressive!
An even better volume control than shunt types is where the volume is part of the gain(as in load resistance). There is no resistor in series at all. This approach can't utilize all circuit topologies of course, so it may not suit u. Look here for one version:
http://home.c2i.net/semfielec
and under the first preamp(the hybrid).
I've done a similar version with irf610 MOSFETs instead of tubes, and got some 700kHz bandwidth. I mention this cause an earlier post claimed not to like MOSFETs because of the high capacitance.
I have a doubt about transistors instead of relays because of the incredible improvement I've heard from removing mute transistors in CDplayers. Even though it shouldn't affect the sound, it sure does. Perhaps with a large value resistor in series it doesn't affect the sound as much as when used for muting.
http://home.c2i.net/semfielec
and under the first preamp(the hybrid).
I've done a similar version with irf610 MOSFETs instead of tubes, and got some 700kHz bandwidth. I mention this cause an earlier post claimed not to like MOSFETs because of the high capacitance.
I have a doubt about transistors instead of relays because of the incredible improvement I've heard from removing mute transistors in CDplayers. Even though it shouldn't affect the sound, it sure does. Perhaps with a large value resistor in series it doesn't affect the sound as much as when used for muting.
Balance Zen volume control
What do you think about so called rheostad mode attenuator. Input level is adjusted between hot and cold sides ea. stepped volume pot is connected between positive and negative inputs. That way there is no room for variance to occur and there is only one contact with resistor switching section. I never tried that one but it looks very appealing and I would probably use it in my next pramp. Currently I'm using passive preamp with 5k resistor in series and 100K motorized Alps to the ground. I didn't go for stepped attenuator to the ground because I want to have remote control option. Anyway that setup worked well so far and I only had about 3dBs gain lost.
What do you think about so called rheostad mode attenuator. Input level is adjusted between hot and cold sides ea. stepped volume pot is connected between positive and negative inputs. That way there is no room for variance to occur and there is only one contact with resistor switching section. I never tried that one but it looks very appealing and I would probably use it in my next pramp. Currently I'm using passive preamp with 5k resistor in series and 100K motorized Alps to the ground. I didn't go for stepped attenuator to the ground because I want to have remote control option. Anyway that setup worked well so far and I only had about 3dBs gain lost.
5k ganged pot
I have searched with google and browsed all of the links above, I am still unable to find a 5k ganged pot for use at the output side (I can find plenty of 10k and above). Can someone please point me to place where I can buy them (not DACT, something reasonably priced).
If they are not available, can I use 10k pots with a 10k resistor in parallel. I guess that will distort the resitance curve, but does not appear to be too bad:
10.000 10.0000 5.0000
5.0000 10.0000 3.3333
2.5000 10.0000 2.0000
1.2500 10.0000 1.1111
0.6250 10.0000 0.5882
0.3125 10.0000 0.3030
0.1563 10.0000 0.1538
0.0781 10.0000 0.0775
0.0391 10.0000 0.0389
0.0195 10.0000 0.0195
0.0098 10.0000 0.0098
Also, in this case I should be able to get rid of R11 and R12 - the 100k resistors in parallel with 5k output pots. Maybe, just replace the 100k resistors with 10k and the 5k pot with 10k. Can someone please comment on this.
Pl ignore my stupidity
, I am an absolute noob to diy - it will be some time before I attempt this, am trying to learn as much as I can right now.
I have searched with google and browsed all of the links above, I am still unable to find a 5k ganged pot for use at the output side (I can find plenty of 10k and above). Can someone please point me to place where I can buy them (not DACT, something reasonably priced).
If they are not available, can I use 10k pots with a 10k resistor in parallel. I guess that will distort the resitance curve, but does not appear to be too bad:
10.000 10.0000 5.0000
5.0000 10.0000 3.3333
2.5000 10.0000 2.0000
1.2500 10.0000 1.1111
0.6250 10.0000 0.5882
0.3125 10.0000 0.3030
0.1563 10.0000 0.1538
0.0781 10.0000 0.0775
0.0391 10.0000 0.0389
0.0195 10.0000 0.0195
0.0098 10.0000 0.0098
Also, in this case I should be able to get rid of R11 and R12 - the 100k resistors in parallel with 5k output pots. Maybe, just replace the 100k resistors with 10k and the 5k pot with 10k. Can someone please comment on this.
Pl ignore my stupidity
, I am an absolute noob to diy - it will be some time before I attempt this, am trying to learn as much as I can right now.- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.