Crown Micro-Tech 600

[Original Burnedfingers]

I guess in all fairness one could say that any amp can be made (redesigned and modified) to not only stay together but to sound somewhat better than it did when it left the factory. One such person on this forum with the ability to turn a sows ear into a silk purse is "DJK"

I have had the pleasure to hear or I should say be subject to equipment that has gone under his iron and been modified. One such example is a local band that employs crowns for the bass that DJK has modified. The amps totally beat you to death and still stay together.

Maybe he can lend some helpfull ideas here.

[v-bro]

You can also build a kit in, like an AMP2, AMP7 or AMP8 from 41hz.com,
they're very powerful, sound the best you can probably find for the money and use only little power (VERY efficient!!!).

Maybe you can even use the same PSU and not even have to cool it with an extra fan... I read: 90% efficient! They hardly even get warm because they're actually class D (but with VERY good sound...).
http://41hz.com/

Look at the "amp. overview" and you'll see which is suitable....

[v-bro]

Look at their price list and you'll start to smile..

[dirtyk777]

The best one i see here has a max ouput of 2 x 500 watts at 4 ohms. I need something at least to be like 800 at 8 ohms(bridged) if possible. I see a hi power kit for sale on the site, but not quite sure how much more power they are sellin me for sixteen bucks. It says it uses a larger capacitor of 10,000 uf. I was going to see if i could use my massive mallory caps i dug out of the crown.

[FastEddy]

dirtyk777: " ... WELL, the whole idea of "cowboying it" kinda scares me when dealing with high power audio. ..."

Figures of speech should not instill fear ... Any voltage above 70.7 VAC should be handled with great respect of course. Tesla's One Hand Rule (at a time) should apply.

" ... Do you think i could use any of these [Sony] parts and incorporate it into the Crown Amp [?]..."

Possibly, but you might end up stripping the Sony boards down to the discreet parts ... caps, coils, etc. to obtain your goals.

My advise would be to "start fresh" (as I did w/ the 202). The Crown amps & circuits (boards) generally are very reliable, notorious for living through a world of abuse. You would have a very decent case, power transformer, switches, gain controls, etc. ... after removal of the main audio board(s), all of which were designed for cool running and longevity.

" ... I need something at least to be like 800 [watts] at 8 ohms (bridged) if possible. ..."

Now that's what I call cowboying it ... It might be possible to do with the existing Crown case & parts ... but there would be serious questions about audio quality ... and the power supply would have to be radically different, negating the "need" of many of the extra parts in the Crown case. ... (What kind of other specs? THD?, "music power" or what? multiple speakers? Is bi-amping a possibility rather than bridging?)

This thread started I believe by considering revisions and improvements to the original Crown amp design. 800 watts (bridged) is do-able. But you might consider something like this:

The Crown transformer has three secondaries with full wave rectification and filter caps: two @ +/- 40 VDC and one @ +/- 15 VDC. Using both of the higher power secondaries and associated parts (diode bridges, large caps, etc.) ... and powering two decent amps, bridged if needed.

Examples: http://aussieamplifiers.com/NX400+.htm ... Mr. Holton's newest creation(s) can be bridged ... although I personally would not do this. I would simply use the existing Crown case, etc., and install both NX400 type (or equal) amps as stereo or dual channel, unbridged = easier, fewer parts, less redesign work, better specs and results. With dual, +/- 40 VDC supply rails to two NX400 type amps, the overall result would be approximately ~~= THD = 0.01 to 0.005 (1K) @ approximately ~~= 250 watts each (because of the lower DC rail voltage).

The limiting factors here are the original Crown transformer & PS parts ... being only capable of (rectified) two channels of +/- 40 VDC. (Your could lash the two secondaries together in series and rectify & filter the result for ~~ +/- 80 VDC, but there are few kit amps or board designed for these higher DC voltages. (It only takes ~ 30 VDC to leave nasty flesh burns, cowboy = )

If you really, really need 800 watts into 8 ohms, with decent specs ... you may have to get another horse to ride.

Seriously, 150 watts or 400 watts with very low distortion sounds a whole lot better than bridged amps resulting in 800 watts (with poor specs) into the same speaker set.

[dirtyk777]

Very good point.

After i wrote that post, i thought about having a pre amp with those small Class D amps that was posted on here earlier. Can you pre-amp those cause that would be super? As for my Crown amp, i'm basically starting to move to the idea that it will be only used for its chassis, the caps/parts, and for its inputs/outputs.

I've learned to deal that an amp designed around ideas in 1986 will not be suitable for loads of today. Right now, i am working with 4pi-18 speaker from www.pispeakers.com (to answer the what load question) So we only have one load as of right now but soon to move to two of the same speaker(once i get more money).

As for sound quality: ~<.00001% distortion only...i cannot deal with anything less....obviously i am just kidding...ha ha. But as for sound quality, i would just like it not to have a fuzz noise over my speakers. Drunk people aren't going to come up to me while dj'ing to tell me that i'm missing punch in the frequencies of 20-30hz unless i come across some people in the forums...in that case my bad.

Bi amping is definitely a possibility i'm looking into: Thus my questions with the class D amps listed.

So new questions have erupted...again.

1. Can the class D amps listed at www.41hz.com be used as a internal pre amp on a speaker?

2. What should i do with the power boards, resistor, caps(expecially the humongo(large) mallory caps), and chassis of this design?

3. Should i use the mosfets in the sony car audio amp?

4. Cowboying it? = IF(Southgeorgia boy)=yes, (Almost Certain Death), (Super cool amp)
(nerdy code joke)

5. Buying a separate board design to create coolness/ or design my own(i did it in like fifth grade but that was to make a hokey dokey radio)

6. Is Dirty K an idiot for thinking a crown micro-tech 600 can be resalvaged?

Thanks everyone for their inputs:

Kyle

[FastEddy]

" ... After i wrote that post, i thought about having a pre amp with those small Class D amps that was posted on here earlier. Can you pre-amp those cause that would be super? As for my Crown amp, i'm basically starting to move to the idea that it will be only used for its chassis, the caps/parts, and for its inputs/outputs. ..."

My sentiments exactly ... good show.

Some References:
New D-Amp Web Site! ... he will have DIY kits "real soon now": " ... DIY module are already built, just wait to finalize some legal paper due to cancelation in a OEM order...Maybe in 1-2 weeks! ..." ... Problem for you may be that these will be associated with special switching power supplies = and may not be usable with the Crown parts.

http://www.hypex.nl/ ... see the "700" model would work with Crown case/parts, but the Crown transformer = +/- 40 VDC rail voltage = too low for single 700 watt output = more like 400 watts, each channel, but bridging of two modules is possible with very good specs. ... see also: UCD700 Layout and Wiring

http://www.class-d.com/Pages/Power-Amplifiers.aspx ... they sell modules, but don't do so for DIY types, only for OEMs. (again, a different PS than Crown would be needed. )

Info only: http://www.nuforce.com/products-monoamps.htm ... the reference #8 & #9 designer lives about four blocks from my house ... DIY kits "real soon now", but rely on special switching supplies

....
" 1. Can the class D amps listed at www.41hz.com be used as a internal pre amp on a speaker? " ... as in "plate amps" ? ... amp built into speaker box = happens all the time and a good solution for the stage where speakers may be remote from mix boards, etc. (see also http://www.hypex.nl/ ... see DS-4 model )

" 2. What should i do with the power boards, resistor, caps (expecially the humongo(large) mallory caps ...?" That's what your garage is for = storage of all those really, really great audio parts = I take 'em to the local surplus outlet once a year for trade = value ~ US$0.50 per pound / US$1 per kilo.

" 3. Should i use the mosfets in the sony car audio amp? " ... No.

" 4. " ... Yes.

" 5. Buying a separate board design to create coolness/ or design my own ...?" ... Get a good DIY kit ... or get pre-assembled modules. (I like Anthony Holton's stuff: http://aussieamplifiers.com )

" 6. Is Dirty K an idiot for thinking a crown micro-tech 600 can be resalvaged? " ... Absolutly Not! , I wish I had one to strip down and use for my AV 400 boards ( http://aussieamplifiers.com/av400.htm ... same / same ala ... http://3dotaudio.com/ampics.html ) ...

[dirtyk777]

Alright so just like any project, The design plans have changed dramatically.

So as of now:

1. Taking out every last thing that is known to crown out of the amp, including the Transformer, due to the fact it looks like the inside of my fishing reel(just with plastic around iron, and magnetic line)

2. Replacing with a new PS board and a new AV400. I like the clean look of the crown you had in that link. Crown's whole set up is cumbersome and probably the reason it gets so hot.

3. What transformer should i use with the AV400 and the PS boards you had.

4. Should I have two PS and two AV400's?

5. I plan on powering the fan with DC and still having it in the middle

6. Pictures are coming, as soon as i find my camera charger.

Thanks again

[FastEddy]

1. Taking out every last thing that is known to crown out of the amp, including the Transformer, due to the fact it looks like the inside of my fishing reel(just with plastic around iron, and magnetic line)

This is the most useful part ... "First, select a transformer ..." or words to this effect from other posters here. What it looks like on the outside, other than in the case of burned conections / covering / plastic tape, etc. is unimportant in the Crown's case = Good stuff if not toasted.

2. Replacing with a new PS board and a new AV400. I like the clean look of the crown you had in that link. Crown's whole set up is cumbersome and probably the reason it gets so hot.

I would get the pre-assembled modules = saves time, expense, possible mistakes ... My old eyes are barely able to solder all those little parts ... but do as you wish. (I got the AV400 "kits", still had to shag a lot of parts, work with magnifying glass, etc.) Note that the assembled modules are within a few US$ of the kits so parts + kits = more than assembled modules

3. What transformer should i use with the AV400 and the PS boards you had.

See: http://www.hypex.nl/ ... transformer section ... note that the bottom one they supply is very close to the specs required ("Suitable for multiple UcD400 amplifiers.") so = +/- 42 VAC X 1.414 = +/- 59+ VDC ...

4. Should I have two PS and two AV400's?

I did for this: http://3dotaudio.com/ampics.html ... but I'm into overkill on supplies. Mr. Holton says two are not necessarily required.

5. I plan on powering the fan with DC and still having it in the middle.

Fan?? We don' need no stinking fan! ... but if you must, seriously consider using the Crown parts with their thermal switching scenario. (The AussieAmplifiers are quite efficient = power MOSFET amps and all they really need is a healthy heat sink (which you may be able to save/use from the Crown).

6. Pictures are coming, as soon as i find my camera charger.

I hope you are not simply doing this all on my say so ... It is difficult to do tech support by blog ... pictures or not.

[dirtyk777]

O no pictures are just here to show you how i'm progressing....plus i like taking pictures. I do have a background in doing circuit work, so im not getting my feet wet for the first time on this project. But i do appreciate an experienced input. Seeing that this amp was made the year i was born, i'm not too sure of the sound quality/overall quality of this system. I just needed suggestions on how to make an amp from this amp, that is up to today's standards.

I do realize class d's don't need no stinkin' fans as you would say, i just felt like if i had a fan laying around, i might as well use it. But i will still save the heat sinks.

As for the transformer, i still think its trashed due to the large what looks like a burn hole i found in the tape. How it would have a burn hole, don't ask me, but it has been laying around a fraternity house for a while. So i'm attributing most of the damage to this thing from that. Also at that website it says, "suitable for multiple"...wouldn't be "overkill" would it?