What about big IC amps, STK****?

jol50

Member
2007-11-08 2:14 am
What is the deal with big IC amps, I see them in home use all the time but not cars? I have an old Blaupunkt with two http://www.electronica.ro/audio/STK084G.shtml in it. It works well, but is a little weak in bass full range....kind of like a cheaper home unit is. However if I force it as a sub amp it was impressive in the right setup. It has power BJT in the PS too. Completely different than the common modern amp. I cleaned a kind of new techniques home amp the other day and it had a big transformer and one huge IC with a fan on it, that was it....though I have not seen many home amps inside. Do these have a higher cost? I found one of these STK for 18 pounds on ebay in the UK....or do they just suck as amps?:) It sure is a simple looking thing.
 

fizzard

Member
2006-11-02 8:12 pm
a.) General perception, true or not, is that they are inferior in sound quality.

b.) They don't handle the low impedance loads that car guys love.

c.) Professional amplifier builders like to "voice" their amplifiers.

d.) Output transistors probably aren't matched, bias not precisely trimmed, etc. Laser trimming and zener zapping aren't really used on low end consumer products.
 

jol50

Member
2007-11-08 2:14 am
I bet this does have a more flat response, thus the lacking bass. That is one reason I like older alpines because I think they eq them more for a car. I did run this for years on 4 10" at 2 ohms, it is rated for 80w x2 at 2 ohms and 60 at 4 ohms. Max of 24 amps draw. It outperformed a few 300w amps, not cheezy 300 watt amps either, I was amazed. But, that was IB subs so control had a lot to do with it.
 

jol50

Member
2007-11-08 2:14 am
Yes, BPA 260. I have two and the other is blown but have not worked on it yet. It blows fuse with trigger. They worked good but had to EQ bass into them if full range or highs under 200Hz. However, considering some of the cheap amps today and back then I'd say they worked well. Lots of power for 2x60, easily matched typical 2x75s and the best on IB subs. I have wondered for many years why this would stay right at xmax on 10" subs and other amps would go out of control. Old efficient 10s, not big wattage subs. They would move your hair nice.

Don't recall noise being an issue and I like it clear. Others did not like these amps though, I got them cheap back in the day. Noise might have been an issue, we had a lot of noise problems back then I don't see today. When I installed I was putting caps on power wires all the time.

Memory is fuzzy but I thought once linear power or RF had this cube amp, it was tiny and went behind a HU. Powerful thing like a super output HU....sounded good but we could not get the noise out of it from alternator and ignition back then. Pioneer had real low signals on RCA, that was a problem then.

Sometimes I also ran a 260 on highs and other times I did not if I could not get enough bass out of mids. I didn't like to use EQs back then as ones I could afford put noise in the system, so I did a lot of swapping of amps/drivers.

I'll have to find a data sheet, I don't even know how to test one of these big ICs. Seems to me they could change response in the input area easy enough....there must be reasons not to use them even though home equipment does.
 
A BPA260 and some old efficient IB 10's.

Ooh, what's happening? I feel woozy... I'm back in my first car, a '68 Mustang... It's 1984 and I'm looking at a pair of Pyle Driver 10's I just installed in my trunk IB with a BPA260, a BPA 430, Alphasonik EX-2... getting fuzzy now... some kind of 6x9's, maybe Beckers, and something even fuzzier in the doors... It's getting clearer looking at the dash... a Blaupunkt CR2002 cassette deck, and an Alphasonik PEQ-7. What's that crap I'm playing, Huey Lewis? Ugh, toss that out quick!

It's not much by todays standards, but back then it would bring installers out of the shop to have a look. The 260 was NOT lacking in bass.

Eventually ended up with Alphasonik amps, which really did sound better than the Blaupunkt IC amps, paper cone Vifa 10's that went extremely low, 6" Vifa midbass, Alphasonik D6200 plates and a Nakamichi cassette deck.

Wow, thanks for the trip!

S/N ratio wasn't spectacular, but plenty of discrete amps were worse and didn't sound as good overall.

AFAIK, these could be tweaked with external component choices, but that's getting away from the "out of the box" design idea. After building a SMPS, if there's too much design work involved with the IC, the Mfr could've just built a discrete amp for less cost in parts.

If yours is blowing the fuse at turn-on, it's most likely the IC. I only replaced a few, but all were verifiably shorted without even removing them from the board. Often the damage is visible.

Pioneer had real low signals on RCA, that was a problem then.

Oh, man the old component Pioneers? Output was ridiculously low, like 50mV. And their amps used a 12v output that sensed current draw for turn-on. With a nest of wires and that big DIN cable. What a mess. We eventually refused to install them!

Again, thanks for the trip!

Tim
 

jol50

Member
2007-11-08 2:14 am
LOL, I had a smokey and the bandit with 4 10" pyramid paper W10 on that BPA260 it was a perfect match, various 6x9 like sansui and EPI, and 1" domes in front (phillips, later radio shack that sounded/looked the same, boston acoustics for a while- very nice) and once 4" mid before I got rid of that car. Had a sweet nak 2 way crossover that really helped it. Must have been late 80s...Madonna just shook the car :D lol! But I listened to all kinds of stuff. The back window was like a horn I swear. Cut holes in seat foam to mount 2nd set of 10s there....barely could squeak amps between them. The pyles were awesome and near unblowable, they would outrun two of my pyramids but not 4. They don't make them like that anymore....but IB they sounded great and got a lot out of them for little wattage by today's standards. Lots of people laughed at my $15 subs until they heard them, only problem is they were worn out in about two years.

Back then it was an impressive assortment of junk and my first real system. Seems like I changed stuff weekly. You could hear that car rumble a mile away and I am not kidding, could tell the song. I would blow 30A fuses on the amps every week or so on the right bass heavy song. Can't remember HU maybe 999 Kenwood or 9900 something like that. Used metal tapes made on a nice home system, sounded way better than bought. Ran some coustic amps too, they worked nice....old ones that look like a linear not the newer side finned ones. They had TO3 on them. Sansui 10s were not bad either, also ran one of the amps that was a ppi. One winter beater I had was an Omni :) I built a box that just wedged into the hatch at 4cf and two poly 10s with a big port. Made another box with two 6x9 on top of it plus front door speakers of some kind. It nearly thundered as well....was so funny to drive as people back then looked when they heard subs and could not figure out where it was coming from....not that ugly little Omni for sure LOL! Made a custom cover for the hatch so you could not see anything. Oh the fun days!

My friend was going to take the bpa to a tech way back and he can't find the guy, he moved. He is going to bring it back to me next time he stops by so I can look at it. That guy has much of my old system, the coustics and the HU. He has piles of amps most from back in the 80s. He has a LP 2601 he used to run, that was quite a little amp.
 

jol50

Member
2007-11-08 2:14 am
I got my Blaupunkt back and took a look....one channel is shorted completely from + rail to one speaker lead:bigeyes: . I'd say that one is toast. Some of the lettering has come off maybe due to heat, the other one looks ok. Power supply tests ok so far, it would just toast a fuse when you trigger it with or without a speaker.
 
MacIntosh car amps use STK-350- channel driver chips in ALL MacIntosh car amps. I know I have a couple laying around. They are acclaimed for meeting there spec'a both power and distortion wise.


The STK-084G was also used by ADS in their old school Power Plate car amps, Pyramid Car audio used them alot and so did Sanyo in there Brick amp.
In fact STK modules are a Sanyo Electric product , and were used in 79's and early 80's home amps especially Sanyo- Fisher home amps.
 

jol50

Member
2007-11-08 2:14 am
Thanks for the history Justonemoreamp! Minimum 30 order at Audio lab. Someone has them on ebay too, I'll keep looking I don't need it right now. I had a sanyo 100w once and I think it did have them in there. It did not perform like this Blaupunkt though...it may have been smaller as well. Had no bass and hardly was able to run my 6x9 so I swapped it out. Did get a somewhat nice EQ with it a friend still has.

Seems like it would be easy to DIY an amp with these, or copy one even.

I could try to replace them with the 86G its bigger, but with the same rails what difference would it make....not going to mod it.
 
I had a sanyo 100w once and I think it did have them in there. It did not perform like this Blaupunkt though...it may have been smaller as well.

That was a PA-6050, no guts.

The big brother PA-6100 (2x100) was twice as big and had plenty of bottom. There was a 4 channel version of the 6100 called the 6110. It was basically the same 2 channel 100W amp with a motorized power fader mounted internally on heatsinks, and operated by remote. It was a bit of a dog as well.
None of them were worth a flip until you trashed the external "speaker protection circuit."

Tim
 

jol50

Member
2007-11-08 2:14 am
I saw a big one on ebay once, it was 4 or 5 channel and they went on about how great it was....but wattage was pretty low per/ch. I think it had a crossover in it, I laughed given my experience with the small one. Also saw some old blaupunkt that was a 5ch the guy could not get that much out of. I don't even like my new 700w kicker 5ch, not for my use anyway. I didn't know it is only 40wx4 more or less, but the sub channel works nice. Speaker protection? I didn't know much about internals then I just hooked it up and ran it.
 

wazzy

Member
2007-09-06 6:26 pm
Kadoma
stks......

hi guys i have repaired several home systems using stk's and i thought i would build one for my self, because i can, and have since built five different amps using various of the stk41 series, at the moment i am using an amp built with stk 4181, recons it's 70w min into 4ohm not too bad sounding but not audiophile by any means, playing through some event2020 studio monitors, whips the pants of any home system if you use the right parts, LF response can be tweeked by adjusting the values of a couple of capacitors, i have the data sheets for a couple of the afore mentioned ic's the pcb layout supplied is pretty easy to get working, if any one is interested feel free to e-mail me and i'll send them on to you, all pdf's. by the way you can get thd values as low as 0.005% claimed for the stk 4181x can't verify though don't have test equipment, worth considering?:dodgy:
 

wazzy

Member
2007-09-06 6:26 pm
Kadoma
i'm sure that it is possible to bridge an stk amp with the proper bridging adaptor, they seem to be pretty bullet proof, ran one once at max power for the whole day at 2ohms without any issues except that sound quality wasn't anything to write home about, and you need a really big heat sink, if the protection is activated in any way they tend to become a bit hypersensitive and shut down for no apparent reason the next time you try to cause hearing damage! IF you do break one they don't make any smoke, pretty cool i suppose no drama sorry. wiil try to attach a diagram for a bridging adaptor:dodgy:
 

wazzy

Member
2007-09-06 6:26 pm
Kadoma
i wouldn't say simple if you compare to the gainclones, as there is a pretty large number of parts needed to make the things work but if you use reasonably good caps and metal film resistors the results can be quite surprising i used elna caps in mine. the cool thing is the ic's in the stk 41 series are all pin compatible, which means the same board can be used for amps ranging from the little 4122 to the pretty serious 4191, the one i'm using is rated at 70 watts min into 8ohms thats a lot of sound if you have sensitive speakers, i can make the ceiling lose plaster if i really crank it up it is actually too much to stand for any amont of time, she who must be obeyed gets a bit edgy:mad: if you know what i mean:angel:
 
I can tell you one thing! I would guess that IC-based car amps have a bad rep' due to the crapp that was produced for the car audio industry...especially some years ago.

I remember working at a small shop where we sold a lot of low end (read: high-profit) amps and I installed one in a Jeep Wrangler. I think it was a "Cyclone" brand and had terrible sound quality.

Opened the sucker up and inside was a tiny single-IC based amp. Occupied only about 25% of the entire amp housing! Piece of crapp!

But I was curious of this same subject myself.

My guess, speaking as an engineer, is that perhaps due to bulk purchasing you might be able to build/produce a cheaper car amp using standard MOSFETs and low-tolerance capacitors and resistors.

Just my $.05! :snoopy: