using bipolar electrolytics instead of tants in calrec eq?

[James HE]

I want to build the gyraf calrec eq, but the cost of all the tantalum caps is a bit prohibitive especially for my first real project. Radial leaded tants from mouser are at the cheapest $1.55 or so (Vishay sprague). For a stereo version that's about $37.00 just for the tants. Nichicon bipolar electrolytics at $.23 each are much cheaper. Since I'm still feeling my my way around electronics, I want to keep costs down. How would electrolytics be in that specific circuit, bipolar or polar?

Or anyone know a source for some cheaper tants? The SMD tants seem to be a lot cheaper, is it possible to use those?

 

[khstudio]

My guess is the Tants are in there for a reason... can't be certain though.

Could be tone but my guess would be function.


Kevin

 

[emrr]

You're gonna spend way more than $37 worth of time PLUS $37 changing it to tantalum later, if the others don't work out. Just spend the $37. They are there for a reason. If the cheaper parts made sense, they'd be in the plans already.

 

[StephenGiles]

I very much doubt if your ears could hear the difference!

By the way, if a deaf person has to go to court, would he go to a "hearing"??

 

[Svart]

tants were likely used due to size and tolerance. bipolars were expensive and hard to get and good unipolars were also expensive but not so hard to get.

Try them, I also doubt you will hear a difference.

 

[shabtek]

Tants are used in many critical applications. I recall reading on Rod Elliots ESP that he discourages their use because they always go leaky. I used one once to ac couple stages and noticed 10vdc on the side that should be at ground potential so I deduced there was dc leakage ...this also threw off the bias of the following stage. Subbing in a bipolar electrolytic corrected the prob. Is this common?

 

[Svart]

yes. tants almost always short when they go bad.

 

[alk509]

Note that most tants are polar, so no need to replace them with bipolar Al-electros... regular ones will probably do.

There are bipolar tants, though, so make sure.

Peace,
Al.

 

[Samuel Groner]

There are bipolar tants, though, so make sure.

That's interesting, never seen before--can you point me to a brand/type? I guess this is just a back-to-back arrangement?

Samuel

 

[alk509]

I know Vishay makes them. Sprague used to make them also, but I don't know if they still do. In fact, Google "tantalum non polar" and the first thing that pops up is this eBay auction for some vintage Sprague non-polar tants.

I'm sure they're just two regular tants back-to-back in one package (like they do with Al-electros).

Peace,
Al.

 

[emrr]

So, we're going to save a measely $31 here to second guess a designers intentions? Seems pretty short-sighted. Now, it's different if you are sure you like the cheaper kind better.

 

[alk509]

[quote author="emrr"]So, we're going to save a measely $31 here to second guess a designers intentions?[/quote]

WE are not... James is. :wink:

I agree that James's motivation for wanting to use electros is like buying a Ferrari and cheaping out on the power windows, but bear in mind the age of the desk: If the designer was making this same unit today instead of in the mid-80s, he probably would use Al-electros, too. Space may have also been an issue for the designer, wheras James's EQ isn't going in a cramped mixing board. I'll take a good quality Nichicon Al-electro over a tant cap any day of the week.

Then again, if he got good quality Nichicons, he probably wouldn't save any money anyways...

Peace,
Al.

 

[emrr]

Okay, improper use of 'we'. But, why then did Gyraf the re-designer keep them in the re-design we're talking about building?

 

[James HE]

[quote author="emrr"]Okay, improper use of 'we'. But, why then did Gyraf the re-designer keep them in the re-design we're talking about building?[/quote]

That's really the question I'm wondering to. It's not really a matter of saving the little bit of money, but in light of some things I had read about tantalums before posting, I wondered if they had to be there, or if it was some preference of the (re)designer, or just a desire to keep it much like the original. If a few dollars gets me some electros to try in there and see for myself then why not try and see. I can later get the tants if I want. Just needed reassurance that nothing was going to blow up before I tried! lol. I'm hoping to build a mono version first and see if I like it, looking for an eq for my live acoustic rig. Then maybe do a nicer stereo version for the studio after getting more experience.

 

[Boswell]

As a professional electronic designer, I would think very carefully about using tantalum capacitors for interstage coupling or anywhere where leakage current could cause a problem. Tants have properties (like low ESR) that are well suited for de-coupling. This includes emitter/cathode resistor bypass and flying capacitor applications, as well as in power supplies. Allow 50% headroom on the voltage rating on tantalums, but don't under-rate them too much, e.g. don't use a 25V part on a 1.2V rail.

 

[StephenGiles]

It's often more costly to wish (with hindsight) that one had done/not done something - I'll bet that one or two folks are thinking just that in the Lebanon right now!

 

[Svart]

as a professional designer I would NEVER use tants anywhere, especially PSU decoupling. Although they are great in the size-to-capacitance aspect, they have a tendency to really hose things when they go bad. I work in an industry where products are continuously getting hammered with odd transients and other hazards like moisture. Tants aren't very good when shocked, even lightly. If they are used as decouplers they tend to short to ground until they either take something else with them as they die, like the output of a Vreg, or until the explode. They also don't like reverse voltages at all.

I stick to electrolytics and plastic caps for most applications and in sensitive applications I like the new aerogel and the new double layer caps when i need super high capacitance in a small package at a low voltage.

Reminds me of a time when someone stuffed a 6.3v 100uf tant on a 35v rail. I had the damn thing in my hand when I juiced it up. POW!!! OWWWW my hand stung like someone had slapped it! the tant came apart with the bang of a .22 and bruised my palm. the PCB flew out of my hand and about a foot away. It was the only one like it in the whole bunch too.

:thumb:

 

[peterc]

I used electrolytics in my Calrec EQ which I then sold to Matt A. Sounded very nice....

Peter

 

[aurt]

While the tants may contribute to the "sound" of the unit, Al 'lytics sub in fine. Actually, I'm no great fan of the "sound" of tants, unless properly biased. That's a different kettle of fish, however.
There was a time when many designers felt tants were the answer to all capacitor ills. I think we've passed that time now. As has been mentioned, they fail short, which can prove really annoying. I've replaced many in service in professional studios with never a complaint about something not sounding right.
Apparently there is actually something of a tantalum shortage for the past couple of years, which accounts for the difference in price.

Just my two cents. Your milage may vary.

 

[gar381]

Ampex ATR-100 machines have tons of tants accross power rails.

Here is what can happen when one shorts!!

I don't want to have to fix this. :evil: :evil:

YOU SHURE AS HELL DON'T WANT TO HAVE TO FIX THIS!!!!

Stay away from tants in this day of good electros :thumb:

GARY