New Projects (pics)

[Handcrafted Tone]

I've been talking about a few new projects lately, but due to time and money limitations, most of these projects are not finished yet. I thought I'd let you guys know what I'm working on, and maybe kick around a few ideas to improve.

First up is the Jensen Twin-Servo, that will fit in the API 500 series lunchbox. This pre is amazing. Ultra low noise and distortion, and double the bandwidth of a single stage topology. IT SOUNDS GREAT!

The only problem with this guy is I'm borrowing the metal work from my Eisen Audio preamp, and I'm unsure where I should source this metal bracket.

-edit - I borrowed the dimensions of the DIY500 just for this prototype, only to save time in research. I need to modify the bracket to be used with my design. I'm planning on using a completely different layout, but for ease of use in this PROTOTYPE, I used these dimensions.

The next project spawned from curiosity. Do IC's really suck, or is this another case of audio industry marketing? It turns out they do not suck. They can sound Perty darn good! So I made up two little IC to 2520 footprint converters, one for single-stage, and another for dual stage IC's.

The single stage IS FREAKIN AWSOME. I included a trim to tweak out DC offset, and power supply bypass caps. I tried out the OPA604, AD797, and the NE5534. All three had slightly different characteristics, and all sounded great compared to a JH990C. I used a 312 card to test. I'm not 100% about output driving capabilities, but they drove a Cinemag CMOB-2S with about 25' of cable with no problem.

The dual opamp to DOA footprint converter was a continuation of the previous idea spawned from this Burr Brown APP note: http://focus.ti.com/lit/an/sboa031/sboa031.pdf
It uses both gain stages in a dual opamp to double output drive capability. It sounds fantastic, but it becomes unstable at the highest gain settings. :sad: Does anyone with more experience know why? I'd like it to be a drop in replacement for a 2520. The gain settings that the oscillation occurs is so high that you'd never use that setting, but I still want to find out why it's happening and how to fix it.


You can also see in that pic my attempt at a simple DOA. I used the topology of my Sphere M1200 card, and tried to shrink that down into a 2520 footprint. It sounds really good at low gain, but there is not enough headroom for a mic pre (it distorts really bad). I'll have to dedicate some time to this one someday.

and last for now, a noise gate based on the THAT application note, built around the 4301 dynamic processor chip. I just plugged it in today, and it works great, but there is some oscillation associated with the release control I still have to work out.

There are two other projects in the works, but I should probably finnish up these first.

BTW BIG thanks to Olimex, that processed my pcb order even though I was a day past their deadline (they took the whole month of Aug off for vacation). I didn't realize bulgaria was like 10 hours ahead of LA.

 

[Svart]

I never did understand why TI did the dual opamp like that, You would expect a slight delay for the second opamp..

 

[Kit]

Looking good. :thumb:

Opamps can be great. Like all other things, the end result depends on design and implementation.
And they are cheap.

Any metal shop worthy of its name should be able to bend up those module L-brackets for you. Should not cost to much.

 

[Ptownkid]

Really interested in the DIY gate...

 

[Boswell]

It sounds fantastic, but becomes unstable at the highest gain settings. Does anyone with more experience know why?

This sounds like a phase margin problem, brought on by having the extra voltage follower "helper" to get additional output current. A small polystyrene or NPO/COG capacitor (10 - 22pF) across the feedback resistor should cure the trouble.

 

[rafafredd]

The gain settings that the oscillation occurs is so high that you'd never use that setting

How much gain are you talking about? I don´t think anyone would use more than 60dB anyway, as there is also gain in the input AND output transformers...

 

[Handcrafted Tone]

I got the gate working. It sounds great. Somehow a wrong resistor found it's way in there. I'll post sound samples later.

I'm trying some different values in the feedback loop of the dual opamp. Not perfect yet, but close. The oscillation is in the top 5-10% of the pot's rotation, a gain setting I never use. Usually if it is that high the noise makes it unusable anyway.

 

[edanderson]

i work in the same building as jens, of eisen audio. i don't have any financial interest in his business, but i'd like to see him (and all DIYers) succeed. so when i read this:

[quote author="Handcrafted Tone"]The only problem with this guy is I'm borrowing the metal work from my Eisen Audio preamp, and I'm unsure where to source this "metal L bracket." If anyone knows a cheap manufacture that can make these in low quantities, the info is greatly appreciated. [/quote]

it made me a bit queasy. you ordered his kit, used it to help package your idea, verify your measurements, etc. and now you want to copy his metal work and have it made inexpensively, and sell it to other people. :roll:

may i suggest that you contact jens instead? i'd guess that he'd be willing to sell you a small quantity brackets at a good price. and if your business takes off, you can order together, and both save money due to economies of scale (quantity discount). working together, and sharing the proceeds appropriately is better than trying to undercut each other.

ed

 

[edanderson]

[quote author="Handcrafted Tone"]I'm trying some different values in the feedback loop of the dual opamp. Not perfect yet, but close. The oscillation is in the top 5-10% of the pot's rotation, a gain setting I never use. Usually if it is that high the noise makes it unusable anyway.[/quote]

it sounds like you are pushing the opamp too far; not enough feedback (= too much gain) and the configuration is unstable. in addition to experimenting with caps, you should also consider a resistor in series with your pot, to set the maximum gain. that way you can crank the pot to the end of its rotation, but not enter the gain range that is giving you oscillation.

ed

 

[Ptownkid]

[quote author="edanderson"]i work in the same building as jens, of eisen audio. i don't have any financial interest in his business, but i'd like to see him (and all DIYers) succeed. so when i read this:

[quote author="Handcrafted Tone"]The only problem with this guy is I'm borrowing the metal work from my Eisen Audio preamp, and I'm unsure where to source this "metal L bracket." If anyone knows a cheap manufacture that can make these in low quantities, the info is greatly appreciated. [/quote]

it made me a bit queasy. you ordered his kit, used it to help package your idea, verify your measurements, etc. and now you want to copy his metal work and have it made inexpensively, and sell it to other people. :roll:

may i suggest that you contact jens instead? i'd guess that he'd be willing to sell you a small quantity brackets at a good price. and if your business takes off, you can order together, and both save money due to economies of scale (quantity discount). working together, and sharing the proceeds appropriately is better than trying to undercut each other.

ed[/quote]


Hahaha

Man, you make it seem like there's something new about metal L brackets that fit an API lunchbox...

 

[Handcrafted Tone]

[quote author="edanderson"]i work in the same building as jens, of eisen audio. i don't have any financial interest in his business, but i'd like to see him (and all DIYers) succeed. so when i read this:

[quote author="Handcrafted Tone"]The only problem with this guy is I'm borrowing the metal work from my Eisen Audio preamp, and I'm unsure where to source this "metal L bracket." If anyone knows a cheap manufacture that can make these in low quantities, the info is greatly appreciated. [/quote]

it made me a bit queasy. you ordered his kit, used it to help package your idea, verify your measurements, etc. and now you want to copy his metal work and have it made inexpensively, and sell it to other people. :roll:

may i suggest that you contact jens instead? i'd guess that he'd be willing to sell you a small quantity brackets at a good price. and if your business takes off, you can order together, and both save money due to economies of scale (quantity discount). working together, and sharing the proceeds appropriately is better than trying to undercut each other.

ed[/quote]


I already talked to Jens about making this pre months ago. I had a working prototype (home etch) before I bought his kit. I am not going to use his dimensions in my pre, but due to convenience, I used them in this prototype. I've planned out 3 other 500 series modules, and none of them use his dimensions. I think he did a great job, but we should encourage the 500 series cards, and not worry about who thought of it first. (oh wait, it was API) :wink:

Your idea about ordering bulk with Jens is great, if he is willing I would greatly appreciate the partnership.

BTW, Jens kit is awesome and completely worth the money. I told him I'm done with the 312/512 stuff and I'm leaving all that to him. Im not planning on offering this as a kit (with switches knobs pots and stuff), but it would obviously need mounting hardware. I may leave the front panel design up to the buyer (but offer a .fpd template, or a generic front plate)

COME ON EVERYONE BUY A LUNCHBOX, or lets come together and make one. It will be the new DIY craze. It is a great format for pres, eqs, comps, effects hell what ever you can think of. Metal work is a minimum, and it looks totally pro. Why hasn't this caught on here yet?

 

[Handcrafted Tone]

[quote author="edanderson"]
it sounds like you are pushing the opamp too far; not enough feedback (= too much gain) and the configuration is unstable. in addition to experimenting with caps, you should also consider a resistor in series with your pot, to set the maximum gain. that way you can crank the pot to the end of its rotation, but not enter the gain range that is giving you oscillation.

ed[/quote]

Thanks Ed, I'll work on it tomorrow after work.

 

[peter purpose]

Very tasty Rob..... :thumb: :thumb:

 

[laitue5]

Wow! Which software did you use to design those boards?

 

[Handcrafted Tone]

I got hooked on eagle from cadsoft. I like it a lot. It is available for all platforms and free for non-comercial use (3"x4" max 2 sides). I stepped up to the full version.

I used Olimex to fab the boards (http://www.olimex.com/pcb/index.html) They will even accept .brd (eagle) files instead of gerbers.

Everything in eagle actually makes sense, but it will take a newbie a LONG time to realize that. :grin:

 

[laitue5]

:thumb: Thanks I?ll try.

 

[edanderson]

[quote author="Ptownkid"]
Hahaha

Man, you make it seem like there's something new about metal L brackets that fit an API lunchbox...[/quote]

so... if i were to order your green pre parts kit, make a list of the parts, post asking where to source some of them, add a few components of my own choosing, and then sell it as a kit, that would be totally cool, right? 'cause you're hardly the first person to come up with a parts list for the green pre. and i would have done some work, making my copy of your list.

or are you saying that you know someplace where i can call them up and say, "i want a metal bracket that will fit an API 500 lunchbox... yeah, you know, the back part... thingy... and um, the screw holes, holes for the switches, DI jack, and gain pot all need to line up with a eisen audio PCB" and they'll know exactly what i'm talking about AND will sell it to me for a reasonable price?

i'm all for HT selling his boards. they look very good. whether he sells this one or others as a 500 module or whatever, i'm sure it will all be great. but why try to reinvent the bracket when jens has exactly what he needs? i doubt HT can get them in small quantity for a better price than what jens would charge him.

ed

 

[Ptownkid]

[quote author="edanderson"][quote author="Ptownkid"]
Hahaha

Man, you make it seem like there's something new about metal L brackets that fit an API lunchbox...[/quote]

so... if i were to order your green pre parts kit, make a list of the parts, post asking where to source some of them, add a few components of my own choosing, and then sell it as a kit, that would be totally cool, right? 'cause you're hardly the first person to come up with a parts list for the green pre. and i would have done some work, making my copy of your list.

[/quote]

That is a very poor comparison....he is talking about one piece of metal that does not affect whether someone wants and eisen audio pre or a handcrafted tone pre.

and yes, the dimensions of a bracket to fit an api lunchbox are not hard to get, nor is it difficult to draw it up in autocad.

I'm all for standing up for our brethren and to help support their endeavours, but we're talking about an L bracket here man.

Let's not forget the fact that we are cloners...

As for the green bom, I'm using the same one everyone else is man.

 

[Ptownkid]

I guess I should point out that I do agree that going in together for them would obviously be beneficial for all involved

 

[ruairioflaherty]

Handcrafted Tone (dude do you have a real name?)

I've put fairly serious thought into the idea of a DIY 500 series rack as I'm sure you have but I think the low power rails are a limiting factor for 500 series DIY. If I were going to (and I will time and money permitting) build a rack system I would design it to address the shortcomings of the 500 series most notably the low rails and the small front panel are. As has been discussed before I like the idea of-

-A 4U rack (this means longer front panels, more room for eq knobs, meters etc)
-high (er) voltage rails (+/-24v? and 48v) with regulators on board each unit ala 7th circel
-A deeper chassis to allow deeper units (in a perfect world one could even design a mating unit with regulators to allow 500 series modules to be used in the rack)


There are plenty issues that would need resolving to make this a reality but if it worked it would have all of the advantages of the 500 series (bar buying a rack off the shelf $$) and none of the disadvantages. Porting existing designs like the G1176, 990 servo pre (with full 24v rails), 1272ish pre would/could/might happen over time and the larger module size would allow more flexibilty for new projects.

I liked the sentiments expressed by Soundguy on here a while ago when he said that for him DIY was not about saving money but rather about building a box the way he wanted to and making it better - I would like to apply that to the 500 series but for now this is just talk Jens and Handcrafted are out there doing it for real,

cheers,
Ruairi