# Audio System Twister AMP Mods (w/ pictures)



## drumcrusher

hey guys. ive been working on a few mps for our fellow forum member HiloDB1 for a while. with christmas and all that entails at my job, ive finally started wrapping the whole project up. its been pretty nice working on these amps. i never had any experience with them in the past but have heard good things about them. they are really sweet amps as im sure some of you know already, and i believe they were modeled after the design of some of the Zapco competion amps. namely the ones where the tranformers were located along the back wall of the board against the heat sinks. the owner sent me 3 F4/ 380's which are 4 channels @95 wpcat 4ohms. and 2 F2-500's which are rated at 2 x 230 wpc. they are new enough to have mostly surface mount parts which is a little more time consuming to work with. you also have to be a little more careful not to lift any of the traces when removing those suckers, but the boards are well built and solid, so that wasnt much of a problem. im goint to post some general pictures of the boards for now to show what ive done. ill post more details as i get the photos edited. my photoshop doesnt work on this new macintosh so i need to get some software, until then its been a little slow going. (if anyone has a free version of photoshop for mac let me know... haha). the owner basically wanted caps changed out with higher quality parts. i used elna silmic 2 caps extensively in the audio sections, bypassed with either polypropeline, or poly styrene film caps.ive been using Wimas or these really nice EMZ caps that i have to order from Europe. EMZ bought the machinery from Siemens when the later stopped making these parts, and began making them just like siemens did. they are really nice sounding, and they look really good too. in the power supply and some of bigger caps i used Panasonic FC's, or FM's when they were available in those sizes. FM's are slightly better for audio than the FC's in power supplies because of the lower esr numbers, among other things. i like the elnas for audio signals, as they give a warm sound with rich smooth bass. ive used the Muse caps too, and they are nice, but seem a little brighter.


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## drumcrusher

one of the main problems with working on car audio amplifiers/ eq's is the size, and lack of room on the board for parts. of course, it usually seems that the best parts, as far as capacitors go are always huge compared to the parts they are replacing. you have to improvise many times in order to make them fit. its a challenge many times, which is kindof cool to get creative with it, but many times, its not possible to use a part that would be best. car audio is in a lot of ways a game of compromises though. still, you can do a lot of things that the builders of the amps couldnt without going broke, or charging a lot more for their products. the owner of the amps didnt want to go into the whole op amp rolling this as the 5532's that are in these amps are pretty good. if they were to be swapped out there is no guarantee that there would be much of an improvement that you could hear, especially while cruising down the road. another one of those compromises i guess. the opamps are also smt types that are a pita anyway, so im kindof relieaved that he didnt. ha. im having the same dilema in a zapco studio 500 that im working on, as it has 4 5532's also im smt form. not sure if i want to swap them in an amp that already sounds fine. ill be posting threads on that and an old lanzar opti crossover that ive been working on soon.


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## drumcrusher

mounting bypas caps on the bottom of the board is one way of dealing with space issues. i upped the 50v 1000uf caps in the power supply to 63v 1200uf. the extra voltage should add logevity as they are not going to be pushed that hard. for the 1200uf's i try to bypass them with at least a .01uf film cap. the caps on this particular amp are .039 phillips polyester. pollyester is fine in this application, as well as ceramics or polypropeline. the later is usually larger and sometimes wont fit. the polyester does just as well though in this application. the 2200uf's are bypassed with those green ero 1818 polyesters. they are .22uf. and finally the wimas are .039 too. they are bypassing 470uf panasonic FM's. ive also used silver micas in these spots but they are pretty big.


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## TrickyRicky

For SMD I use a rework station, it makes it a whole lot easier. Even when removing multi-pin through hole components such as 4gang pots (12 pins in a 5mm x 7.5mm).


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## drumcrusher

yea ive thought about getting one of those and probably will eventually. ive mostly been working on threw hole designs though so i havent needed one too much. ive been mounting the smt's onto brown dog adapters a lot recently so i need to come up with something.


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## HiloDB1

epper:epper:epper: Nice work :thumbsup: cant wait to hear them.


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## drumcrusher

Cool man. I'll get with you later about you getting to hear them soon.


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## drumcrusher

sorry for the tiny files. here are some more pics of the work i did on these twister amps.


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## drumcrusher

and sorry for the darkness.


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## drumcrusher

i was sceptical to bypass the 10uf input caps at first because i have heard that some people have experienced some problems when bypassing the elna silmics. in some designs apparently it can introduce a high pitched almost inaudible noise. there wasnt a problem in any of these amps. i started with only .0015uf styrenes to smooth out the high frequencies. that is the reason for bypassing with film in the audio sections. the electrolitics handle the lower frequencies and the fims smooth out the highs. in power supplies its for a different reason all together. the smaller film caps lower ESR and "quicken" the signal. there are disagreements as to which helps the most, and you would think that you would only need to do this in the signal path, but bypassing supply caps can affect things at least as much. some people wil only bypass power supplies. but thats not near as fun. the only problem with doing this kind of work on someone elses amplifier is that you wont have time to hear the finnished product after the caps have been broken in. some companies state that their caps can take 100 hours to really get the smoothest sound out of them. unless you let them run for days on end its kindof hard to let them burn in. but, they do improve with age. ive been thinking about using plexiglass bottoms on some of my personal amps but these twisters would take some serious modifications to do something like that. and they look pretty cool on their own.


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## drumcrusher

these are higher rez


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## drumcrusher

etc...


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## HiloDB1

Im all smiles.


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## Matt R

Cool man, nice work!


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## drumcrusher

Thanks man. Means a lot coming from you.


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## cajunner

tidy looking, when it should look like a mess.


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## drumcrusher

I hear ya. I still have that 400x4 for you if you're still wanting some glory day fosgate power. I just picked up a power 650 mosfet so i have no need for another 4 channel.


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## hambone

are you interested in working on some other twister amps i have 2 that need a little love 

thanks


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## cajunner

drumcrusher said:


> I hear ya. I still have that 400x4 for you if you're still wanting some glory day fosgate power. I just picked up a power 650 mosfet so i have no need for another 4 channel.


cool, I know how that is. I have a 400a4 just sitting on the shelf myself.

and those Hafler eq's aren't doing anything either, just gathering box patina, lol..

good to see you've been able to stay busy, if I get a wild hair I'll pm ya.


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## drumcrusher

Are your twisters in working order, or are they needing to be repaired?


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## sprocketser

Wow , great work in here , what was the goal , did you want to have a flatter response from Power Amps ! Meaning more hifi sounding amps !

Keep it on .


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## drumcrusher

The owner of the amps would be the one to answer that question man. I think he was wanting something that set his amps apart from any other twisters out there. And there's nothing wrong with a little bling as long as it helps improve on an already great amp. ( at least thats how i look at it)


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## sprocketser

Hey thanx for the reply drum , Tought they were yours for some reasons . If it s like the high end audio it makes a difference , might not be too much of a difference , but it makes one .


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## sprocketser

You re the shop owner . Any links !


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## drumcrusher

I do the mods out of my home actually. I have a bunch of amps/ eq's i work on of my own, and sometimes i do other peoples if they are interested in having mods done. Most of the stuff i buy is old school equipment. A lot of zapco's, haflers, fosgates lanzar, etc. some are more favorable to the mods than others, and many already use really good parts. Takes a lot of testing and listening to hear the results. And to be real, a good clean sounding car amp is going to be hard to be improved on audibly when you are listening to them driving down the road with your windows down.


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## sprocketser

Hey cool , I know about driving with windows done can be quite different , lol .
I meant stopped / windows up . 

Yep old school s way easier than newest stuff to work on . 

Good to hear some guys do some mods on car audio stuff .

Can something good be done with old Phoenix Gold !


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