Industrial SMD Gainclone - group buy

[jackinnj]

cuttape is "cut" "tape" == if you don't want to buy a reel of 5,000 pieces you can buy 100 or sometimes 10 == realizing this the proto-houses will take your mini-tape and run it in the machine -- very labor intensive.

[sek]

Hi,

well, I'd say I'm in

But I'm not sure if I understand You right, Per-Anders: You are looking for beta testers?

That would mean you supply everything except shipping costs? I think I've got you wrong though

The reason why I'm asking: because I'm short of cash at the moment... But a project like this fascinates me, as I'm currently in the process of developing an LM3875 or OPA541/9 based GC in smd.

Sebastian.

---

My last smd project. Just because it's a rare opportunity to see smt stuff



It's a partially uncrowded board (finished yet) of a USB-DAC (PCM2902) entirely made with Eagle, manufacturer's Datasheets and information from this board

EDIT: And manufactured DIY with overhead slides, laserprinter, Gesichtsbräuner and etching tools on the kitchen table. That goes without saying

[jackinnj]

Originally posted by sek

My last smd project. Just because it's a rare opportunity to see smt stuff
EDIT: And manufactured DIY with overhead slides, laserprinter, Gesichtsbräuner and etching tools on the kitchen table. That goes without saying

I only do etching in the kitchen when the wife is out of the house. Not a good idea to etch on a gas stove, btw -- releases hydrogen gas !

[motherone]

I'm game for beta testing them, peranders.. I haven't done much SMD soldering yet, but I already have a good portion of parts for a SMD-based gainclone (bought them for when I was using smd-adapter boards to minimize the signal path).

[peranders]

Originally posted by sek
But I'm not sure if I understand You right, Per-Anders: You are looking for beta testers?

That would mean you supply everything except shipping costs? I think I've got you wrong though

This is low budget so you have to actually pay me, then after completed task will get rewarded. I know the nature of people so they must have some pressure to actually perform. Money is good for that purpose.

Experience from my QRP01 project tells me that some people are very fast in building and others are really slow (no result yet...). The purpose of the beta testers is to really get results in a give time.

At the moment my project is only food for thought and when it has come so far so it's time to build I will make up my mind exactly how the beta building will be organized.

First I would like to have opinions of the design or at least the specifications.

[peranders]

http://www.apexjr.com/alesis.htm

Not exactly as my project but similar.

Check out this cute pcb!

[peranders]

Originally posted by jackinnj
"QRP" in the lingua franca of ham radio means "small signal" --

My high power amps is called QRO and my low power QRP

[ThorstenL]

Konnichiwa,

Originally posted by peranders
What do you say about a SMD Gainclone project in August, September?

Project name is "Industrial Gainclone", QRP02

While I like the SMD part, may I ask why not make something unusual, instead of just another 1/2 Channel Amp?

How about an active 2-Way bi-amplifier build around LM3875 with an inverting Highpass (3rd Order) and an Inverting Op-Amp as subtractive Filter for the LF. Then apropriate EQ networks in the NFB of the LF section (correction for usual rising MF in most moder "Bass/Mid" drivers) and possibly in the HF section for the high frequencies.

An option should/could be current drive for the speakers.

Fit a non Op-Amp (eg Diamon Transistor) Buffer for the input (BUF634 or BUF04?) and have the PCB designed to handle the PSU with seperate bridges (discrete diodes) and windings per Amplifier. This way 1,000uF (or even less) on the HF section can be used and 10,000uF (or whetever people like) on the LF section.

Scale the Filters and you can "activate" either any 2-Way speaker or make a 3-Way partially active by separating Woofer and Midrange/Treble.

I think that sort of thing would make a ton more sense.

The Example could have the EQ and X-Over set for the TPX cone Seas Coax driver in a nice slim column enclosure (TQWT) using it's < 40Hz resonance to good effect, making for a nice "beginners" project.

Sayonara

[jackinnj]

Originally posted by Kuei Yang Wang
Konnichiwa,

While I like the SMD part, may I ask why not make something unusual, instead of just another 1/2 Channel Amp?

How about an active 2-Way bi-amplifier build around LM3875 with an inverting Highpass (3rd Order) and an Inverting Op-Amp as subtractive Filter for the LF. Then apropriate EQ networks in the NFB of the LF section (correction for usual rising MF in most moder "Bass/Mid" drivers) and possibly in the HF section for the high frequencies.

An option should/could be current drive for the speakers.

Fit a non Op-Amp (eg Diamon Transistor) Buffer for the input (BUF634 or BUF04?) and have the PCB designed to handle the PSU with seperate bridges (discrete diodes) and windings per Amplifier. This way 1,000uF (or even less) on the HF section can be used and 10,000uF (or whetever people like) on the LF section.

Scale the Filters and you can "activate" either any 2-Way speaker or make a 3-Way partially active by separating Woofer and Midrange/Treble.

I think that sort of thing would make a ton more sense.

The Example could have the EQ and X-Over set for the TPX cone Seas Coax driver in a nice slim column enclosure (TQWT) using it's < 40Hz resonance to good effect, making for a nice "beginners" project.

Sayonara

I worked out the PCB design for the above -- enough op-amp power for the buffer, cascaded LR (1) XO and a phase correction circuit (2). As I read more I decided that it would be a lot more than a beginner/kit project, and if not implemented carefully would lead to "the weaping and gnashing of teeth !", i.e. unhappy customeres.

The idea was to prepopulate the board with the no-brainer bypass and decoupling caps (0805), localized regulators, and decent low-noise opamps, and allow the DIY builder to use through-hole devices for the filter resistors and capacitors.

Without some method of measuring the output -- both magnitude and phase (not everyone has a portable PC with a sound card, or an FFT analyzer) it just looked to me as a project which would frustrate more than help. So, perhaps there is demand for a score of boards, but not for hundreds.

Further, in DIY there is an attitude that "more is better" -- not necessarily the case when it comes to crossovers, indeed, just the opposite can be true.

The good thing which came out of the above was an easy-to-build phase meter PCB, as I thought that DIYr's would find this a necessity to properly set the phase of the HI and LO filters. It is cobbled from an Intersil application note. Unfortunately Intersil seems to have stopped making the transistor array, so a new design is underway with an off-the-shelf comparator.

(1) With TI's "Filter Pro" software any permutation is possible, but the adjustable F(3) and Q option are most helpful.

(2) Ballard, R. "An Active Crossover with Phase Correctors, II", Speaker Builder 4/82.

[BrianGT]

Originally posted by Kuei Yang Wang
While I like the SMD part, may I ask why not make something unusual, instead of just another 1/2 Channel Amp?

How about an active 2-Way bi-amplifier build around LM3875 with an inverting Highpass (3rd Order) and an Inverting Op-Amp as subtractive Filter for the LF. Then apropriate EQ networks in the NFB of the LF section (correction for usual rising MF in most moder "Bass/Mid" drivers) and possibly in the HF section for the high frequencies.
...

If a 2-way bi-amp setup is to be made, why not use a 2-channel chip, like the LM4780? Might be interesting.

--
Brian