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  #1  
Old 02-20-2012, 02:53 AM
Pern Pern is offline
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Planning new DIY Rotary Mixer..

I'm at the moment planning for a new DIY rotary mixer. New to this is a FX send/return functionality and a CUE Mix function. I removed the CUE/Master blend functionality and added a complete CUE mix for all channels.

What do you think of this concept ?


2U Version:






3U version:



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Last edited by Pern : 02-20-2012 at 10:04 AM.
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  #2  
Old 02-20-2012, 03:40 AM
man_traic man_traic is offline
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very nice - 6 channels and that would be my dream mixer
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  #3  
Old 02-20-2012, 03:41 AM
man_traic man_traic is offline
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oh and why did you remove cue/ master blend curiously?
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  #4  
Old 02-20-2012, 04:00 AM
Pern Pern is offline
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The PCBs will be per channel. So it can be used as a 2ch - 6ch mixer. I just need 4.

With a CUE mixer i can do real mixes in CUE mode and not just a blend. One example is when mixing to a song with a slow intro i can put that song on 2 players, one that loops a CUE point with a better mixing tempo. Then mix that loop into the slow intro and have full volume controll over the CUE/Test mix. It's also usefull when adding Jingles/effects/samples in mixes (Internet/Radio broadcasting) etc. And i just like this CUE concept :-)

I'm also thinking of having the option to use the CUE MIX as a second per channel FX Send/Return when not using it for CUEing. Enabled when MASTER (CUE MIX FX) is selected on the HP/VU Select switch.

Like this:

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Last edited by Pern : 02-20-2012 at 05:50 AM.
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  #5  
Old 02-20-2012, 11:59 AM
Pern Pern is offline
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Another reason i'm planning another DIY rotary mixer is that i want to split the functionality to different PCB's. And the main Audio path will be on its own PCB, this is from LINE in to MASTER OUT (Not Booth out). I will also do this main Audio PCB in 2 different versions, one IC based and one Discrete version. But i still haven't decided if i will do this in Bozak style or using one of my Discrete OP designs.
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Last edited by Pern : 02-20-2012 at 12:07 PM.
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  #6  
Old 02-21-2012, 07:42 PM
deepending deepending is offline
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I like the 2u version - a lot. Very simple control panel. The Cue Mix concept is a good approach I agree, I like it as well.

I would buy this kit, would build a 3 channel version.
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  #7  
Old 02-21-2012, 08:54 PM
bossa nolyx bossa nolyx is offline
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Quote:
Originally Posted by Pern
...added a complete CUE mix for all channels.

What do you think of this concept ?
A concept I also thought about many times. I could go with that, biggest advantage could be for home users that don't want to stress their neighbors in late evening home sessions. You can easily mix with these knobs.... but an external headphone amp can do the same in this situation...
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  #8  
Old 02-21-2012, 10:48 PM
Pern Pern is offline
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Quote:
Originally Posted by bossa nolyx
...biggest advantage could be for home users that don't want to stress their neighbors in late evening home sessions. You can easily mix with these knobs.... but an external headphone amp can do the same in this situation...


By using the "HP/VU CUE MIX-MASTER" switch you choose if it's the master signal or the CUE MIX signal that goes into the built in headphone amp, so why would you need an external HP amp ?
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  #9  
Old 02-21-2012, 11:55 PM
Elliot Thompson Elliot Thompson is offline
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Quote:
Originally Posted by Pern
Another reason i'm planning another DIY rotary mixer is that i want to split the functionality to different PCB's. And the main Audio path will be on its own PCB, this is from LINE in to MASTER OUT (Not Booth out). I will also do this main Audio PCB in 2 different versions, one IC based and one Discrete version. But i still haven't decided if i will do this in Bozak style or using one of my Discrete OP designs.

Use your own Discrete OP design if you want to be recognised for your work and not another bloke copying a Bozak mixer.

I would imagine your market would be the deciding factor. Although. If your customers trust you, they will embrace something original created by you without thinking twice.

Best Regards,
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  #10  
Old 02-22-2012, 01:27 AM
Pern Pern is offline
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With "Bozak Style" i am not talking about cloning the Bozak Schematics, I really doesn't think that is interesting to do since there is so much better components available today. It's also easier to add new functionlity to a new design than trying to modify the Bozak. Cloning the Bozak schematics would only be a cheap marketing trick. And this will also be a DIY project so i don't have to think like that and can focus on doing a design that i like.

I'm talking about to use the same type of simple gain stages (SRPP etc.) but in a new design or not. So the question is more - Simple Discrete Gain stages or Discrete OPs. I like the Simple Gain Stages, but with Discrete OPs i have much better control over how much and what kind of THD that is "added" to the signal etc.
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Last edited by Pern : 02-22-2012 at 02:56 AM.
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  #11  
Old 02-22-2012, 04:12 AM
bossa nolyx bossa nolyx is offline
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Quote:
Originally Posted by Pern
By using the "HP/VU CUE MIX-MASTER" switch you choose if it's the master signal or the CUE MIX signal that goes into the built in headphone amp, so why would you need an external HP amp ?
No I meant, if you do not have any of this, there's alway a way to mix in headphones.

sorry that I have expressed myself wrong
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  #12  
Old 02-23-2012, 09:30 AM
Elliot Thompson Elliot Thompson is offline
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Quote:
Originally Posted by Pern
With "Bozak Style" i am not talking about cloning the Bozak Schematics, I really doesn't think that is interesting to do since there is so much better components available today. It's also easier to add new functionlity to a new design than trying to modify the Bozak. Cloning the Bozak schematics would only be a cheap marketing trick. And this will also be a DIY project so i don't have to think like that and can focus on doing a design that i like.

I'm talking about to use the same type of simple gain stages (SRPP etc.) but in a new design or not. So the question is more - Simple Discrete Gain stages or Discrete OPs. I like the Simple Gain Stages, but with Discrete OPs i have much better control over how much and what kind of THD that is "added" to the signal etc.


Such a question would be solely up to you for you are the only one who has access to the schematics.

The only thing you should take into consideration is10 to 20 years from now, will the design be so proprietary that it will be difficult to attain parts in the event a component breaks down.

From a sales point of view, the customer will not care provided the unit works as described. The customer will be more concerned on controls in which he or she can manipulate to his or her taste. Not something configured to a fixed value embedded in the circuitry.

Best Regards,
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  #13  
Old 02-23-2012, 09:45 AM
Pern Pern is offline
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Quote:
Originally Posted by Elliot Thompson
Such a question would be solely up to you for you are the only one who has access to the schematics.

I publish all the schematics, BOMs and building descriptions for all my projects. So when relased, everyone will have access to these.


Quote:
Originally Posted by Elliot Thompson
The only thing you should take into consideration is10 to 20 years from now, will the design be so proprietary that it will be difficult to attain parts in the event a component breaks down.

That's the same problem as with Bozak parts today. But i don't see this as a problem since there is no "strange" components i the schematics. Transistors and FETs can always be replaced with others, sometimes with some minor resistor adjustments.


Quote:
Originally Posted by Elliot Thompson
From a sales point of view, the customer will not care provided the unit works as described. The customer will be more concerned on controls in which he or she can manipulate to his or her taste. Not something configured to a fixed value embedded in the circuitry.

I really don't think that people are interested in doing major changes in the schematics in a discrete design (and actually not in any larger design). Have anyone ever done that to a Bozak mixer ? Adding/changing functionality is one thing, but doing mods to a core schematic ? If you got the skills and want to do modifications to a discrete design and got the schematics, then it's easy to do.
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Last edited by Pern : 02-23-2012 at 10:27 AM.
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  #14  
Old 02-23-2012, 10:29 AM
Captainjr Captainjr is offline
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Keep in mind that the original USA built Bozak mixer designs we talk about are all over 40 plus years old (1970s up) and the parts are all still available if you know who to get them from. Just recently some of the FETs became obsolete and are a bit expensive but we are talking about some very old units still functioning and being repaired today. Look at the mint late production all original DLCs and other nice shape DL units that pop up on e-bay that have all original internal workings plus all the members here on WAVE who have and maintain original Bozak mixers. Good advice Elliot because you do want to keep it as simple with common parts for as long as you can.

Last edited by Captainjr : 02-23-2012 at 10:38 AM.
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  #15  
Old 02-23-2012, 10:37 AM
Pern Pern is offline
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Quote:
Originally Posted by Captainjr
... and the parts are all still available if you know who to get them from.

Isn't it always like that :-)

I agree 100% that it is a good idea to avoid small series components from smaller companies, even if they got fantastic data.

But it's a little different now compared to how it was 40 years ago. When the Bozak mixer was designed and say 20 years after that OPs wasn't very good so there was a big market for high quality discrete components. Today OPs are much better so that the commercial lifespan of discrete components are shorter. So i don't think we can expect to find some modern components still available in 40 years from now.

And you can get great sound with standard components also, here is an example of a Discrete OP that sounds very nice and use cheap easy to get transistors.

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Last edited by Pern : 02-23-2012 at 12:33 PM.
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  #16  
Old 02-23-2012, 05:26 PM
Captainjr Captainjr is offline
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Pern, if you could provide the operating voltage and values of resistors R1-R9, the capacitor values for C1 & C2, and the diodes you use I would like to build a mock up of this circuit and have it compared to an original Bozak audio circuit. I would then publish all findings here on WAVE for everyone to evaluate on their own. Is the information I need on your web site or could you just forward it to me and I will try and do this over the coming weekend in my spare time. Thanks!
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  #17  
Old 02-23-2012, 07:18 PM
Richi Richi is offline
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The endless looking back at discrete is a little nostalgic for me. There a so many schematics available for discrete Op Amps, no need to just focus on one from the past. Why not create a design for a DIP package then you can choose between IC based or discrete to your liking. I prefer the PSRR and the lower noise floor of modern IC over discrete.
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  #18  
Old 02-23-2012, 11:34 PM
Pern Pern is offline
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Quote:
Originally Posted by Captainjr
Pern, if you could provide the operating voltage and values of resistors R1-R9, the capacitor values for C1 & C2, and the diodes you use I would like to build a mock up of this circuit and have it compared to an original Bozak audio circuit. I would then publish all findings here on WAVE for everyone to evaluate on their own. Is the information I need on your web site or could you just forward it to me and I will try and do this over the coming weekend in my spare time. Thanks!

This design isn't really interesting to compare to a Bozak mixer like that since my main goal when designing it was to get a low THD. I'm not trying to copy the sound of the Bozak mixer, i don't think it would ever be 100% the same since the design is different. The goal is to create something new with a great interesting sound. And this is just one of many discrete OP design i have, and at the moment i haven't decided wich to use yet.

BJT OP - THD (SPICE Simulated):
- Standard transistors (BC550C/BC560C) : 0.000095%
- Modern transistors (2SC2240/2SA970) : 0.000052%



In another test design my focus was not to get the lowest possible THD but to get close to the Bozak summing amp THD (this is not the design above). The reason i did this was to learn how to control the harmonics generated in a discrete OP design and what this does to the "sound". And i also got a Bozak summing amp built on a original PCB using the original FETs and transistors to test with.



Before i was more focused on the data sheets and the better specs a OP had the better it "must" sound. Today i listen more and look less at data sheets, perfect data isn't always the same as a great sound.
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Last edited by Pern : 02-24-2012 at 07:53 AM.
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  #19  
Old 02-23-2012, 11:58 PM
Pern Pern is offline
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Quote:
Originally Posted by Richi
The endless looking back at discrete is a little nostalgic for me. There a so many schematics available for discrete Op Amps, no need to just focus on one from the past. Why not create a design for a DIP package then you can choose between IC based or discrete to your liking. I prefer the PSRR and the lower noise floor of modern IC over discrete.

Doing a "DIP package" is what i'm planning for the Discrete OPs, but it will be a little larger than a std OP, more like the 990 format. So i will also do a PCB with a 8-pin DIL socket on it. This way it's possible to use a std OP or my discrete OPs. You can also then mix these in any way you want.

PSRR and SNR is important, but i would never choose a OP over discrete i general just focusing on these. A high quality PSU will improve any design and for SNR you can't just look at the OP, the overall design affects this more than the choice of OP. Just look at UREI 1620, this must be the worst design ever from a SNR point of view :-)

I prefer a well designed Discrete OP using high quality components, running on high supply voltages (like +- 24V) and with a high quality PSU. But there are some good modern OPs available. And you can also get great results with a TL074, it depends what you are focusing on and what type of music you are playing. There is a huge difference if you are playing Classical or House music.
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Last edited by Pern : 02-24-2012 at 06:21 AM.
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