Burning Amp Workshops

1audio

Member
Paid Member
2004-03-24 5:16 am
SF Bay Area
Bob Cordell and I will be giving a workshop on measuring amps and speakers at the upcoming Burning Amp.

We want some insight into how many plan to attend and any specifics people may want covered.

I think we may be able to measure some participants efforts but really in the context of demonstrating how to measure.
 
Hi Demian,

I have provide Bob Cordell with some pcb designs, for evaluation. They are for power amp designs that are in his new book, BC-1 & DH-220C.
In doing so, Bob has graciously devoted his time and efforts to review these designs, build and test them out, amounting to a wealth of tests and methods that reveal both design and pcb layout improvements. As they say, the proof is in the pudding.
I am unable to attend, as much as I would love too but the video would be fantastic for us who are unable.
If you need info from me just ask (PM). I have set up a google drive where the design specifics reside, so I can share them with you for your presentation. Bob has access to these too.

Good luck.
Rick Savas
 
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We want some insight into how many plan to attend and any specifics people may want covered.

Isn't the number of attendees available from Eventbrite?
As for subjects covered, I am interested in measuring an amplifier's harmonic distortion to be able to adjust it as recommended in some of Nelson Pass' designs. The balance between 2nd and 3rd order harmonics and the phase. I know the latter requires a Twin-T notch filter and member Richiem (R.I.P.) posted some information here:

Build -- Active Twin-T notch filter for distortion analysis

If you guys could present a primer on its use we should be able to revive that thread which has been dormant for almost 5 years. I have purchased most of the parts needed to build the notch filter and am willing to post pictures and comments during construction, if there is interest. I am looking for technical advice for a successful build that can be reproduced by other members.
 

1audio

Member
Paid Member
2004-03-24 5:16 am
SF Bay Area
I'll defer to Bob on the electronics measurements for the most part. The general plan is to show how to measure amps (and speakers) what you can see and some insight into how to interpret what you see. As well as show how to spot and avoid erroneous output. All this stuff can lie and you need to see how that happens and how to verify what you see.

I like the idea of getting more insight on relating distortion to possible circuit issues.
 

chromenuts

Member
Paid Member
2008-12-27 7:27 am
Connecticut, USA
I registered for this seminar.

I am curious as to what equipment/software will be used.

The only resources I have for measurement currently are a MiniDSP UMIK-1 and the open source Room EQ Wizard.

It took me a while to even get REW to function with the UMIK on my older Windows Vista laptop.

Eventually, by following some of the tutorials on the MiniDSP website, I was able to take some frequency sweep measurements of a speaker project and attempt to make some adjustments with a B5 active crossover.

I am a complete novice at measurement. I’ve seen it mentioned that REW could also be used to measure certain aspects of amplifiers. I think the complexity of the software and process has discouraged me from learning and doing more.

For instance. I took several near field and listening position measurements of my front horns, slot loaded bass units and subwoofer in order to try and figure out what to do about adjusting the crossover, gain settings and any filters available.

Ultimately, I felt like I wasn’t taking measurements correctly.

My adjustments to try and obtain a flatter frequency response made the system sound worse.

I was unable to figure out how to measure the different parts of the system in the same manner I am used to seeing published as dB for a 1 watt input at 1 meter. They each had there own amplifier and gain settings.

Eventually I read that room response was the cause of my unsatisfactory results and that I needed to strive for a response that rolled off toward the high frequencies.

This left me in the position of feeling like I was “winging it” by ear.
 

astromo

Member
2017-11-13 11:17 am
BFN
I registered for this seminar.

I am curious as to what equipment/software will be used.

The only resources I have for measurement currently are a MiniDSP UMIK-1 and the open source Room EQ Wizard.

It took me a while to even get REW to function with the UMIK on my older Windows Vista laptop.

Eventually, by following some of the tutorials on the MiniDSP website, I was able to take some frequency sweep measurements of a speaker project and attempt to make some adjustments with a B5 active crossover.

I am a complete novice at measurement. I’ve seen it mentioned that REW could also be used to measure certain aspects of amplifiers. I think the complexity of the software and process has discouraged me from learning and doing more.

For instance. I took several near field and listening position measurements of my front horns, slot loaded bass units and subwoofer in order to try and figure out what to do about adjusting the crossover, gain settings and any filters available.

Ultimately, I felt like I wasn’t taking measurements correctly.

My adjustments to try and obtain a flatter frequency response made the system sound worse.

I was unable to figure out how to measure the different parts of the system in the same manner I am used to seeing published as dB for a 1 watt input at 1 meter. They each had there own amplifier and gain settings.

Eventually I read that room response was the cause of my unsatisfactory results and that I needed to strive for a response that rolled off toward the high frequencies.

This left me in the position of feeling like I was “winging it” by ear.

Firstly, thank you for organising the workshop. Even though you made it tough because I had the angst of choosing between this and the build workshop.

I've signed up and I'd echo chromenuts comments.

It would be great if the workshop used DIY level tools that are preferably easy to use, freeware or low cost software employing low cost and DIY (where possible) interface and testing hardware. I'd like to be able to walk away from the workshop with the knowledge to run basic tests to help me build gear and troubleshoot problems if/when they arise.

I've got a 2020 plan to build a BA-3 pre-amp. The build guide recommends final set up based on measured distortion and harmonics. It's that sort of practical knowledge that I'd like to gain.

Looking forward to the session.
 
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1audio

Member
Paid Member
2004-03-24 5:16 am
SF Bay Area
I have been struggling through the learning curves for Omnimic, ARTA and REW. All these programs do similar things but get there in different ways. At present I plan to use Praxis for the speaker testing because I know it well and can make many measurements quickly with it. I'll try to include some screenshots of both ARTA and REW where relevant but I want to focus on technique and setup which is common to all of the programs.

For electronic testing we will use the QA401 because its light, small, flexible and DIY accessible. Its not the cheapest but will get you results quickly. And you can use it with ARTA (and Virtins, DiANA, etc.) if you want.
 

astromo

Member
2017-11-13 11:17 am
BFN
I have been struggling through the learning curves for Omnimic, ARTA and REW. All these programs do similar things but get there in different ways. At present I plan to use Praxis for the speaker testing because I know it well and can make many measurements quickly with it. I'll try to include some screenshots of both ARTA and REW where relevant but I want to focus on technique and setup which is common to all of the programs.

For electronic testing we will use the QA401 because its light, small, flexible and DIY accessible. Its not the cheapest but will get you results quickly. And you can use it with ARTA (and Virtins, DiANA, etc.) if you want.


Thanks for listening.


Sounds sensible and a reasonable compromise given your constraints.. :up:
 

astromo

Member
2017-11-13 11:17 am
BFN
Credit where it's due (even if a little late), a big thank you to Demian and Bob for sharing their experience and parting with their time for the workshop.

I gained a lot. The people perspective was the real cherry on the cake. Far more engaging that way and a great way to meet new faces.