Author Topic: Newbie & Not-so Noob Thread: Questions (FAQ) on Receivers/Amplifiers (Read 190972 times)

homer · « **Reply #120 on:** Oct 29, 2003 at 02:05 PM »

Quote from: RU9 on Oct 29, 2003 at 01:32 PM

What is difference between a passive attenuator and a passive preamp?

Thanks.

the volume control on most passive preamps is basically a passive attenuator.

Gino · « **Reply #121 on:** Oct 29, 2003 at 02:09 PM »

Akyat, I asked Mr. Rivo about that and a pre amp output as well for my Rotel. He says it can be done as long as you have schematics for your amp. Now that's the problem. Hehehe.

av_phile · « **Reply #122 on:** Oct 29, 2003 at 02:27 PM »

I remember buying some schematics from Raon. Can't remember the shop name though. I believe you can just ask some electronics shop about it.

Gino · « **Reply #123 on:** Oct 29, 2003 at 03:39 PM »

They have manufacturer model specific schematics?

akyatbundok · « **Reply #124 on:** Oct 29, 2003 at 04:59 PM »

hmm... i'll go back to raon one of these days to look for schematics. i saw some schematics for sale on the web but i think i'd rather get it from raon. sir av_phile, any idea how much they cost? para lang wag tayo mataga sa presyo.

Garp · « **Reply #125 on:** Oct 29, 2003 at 05:38 PM »

I think you're looking for the store right beside eleshop--forgot the name though. The buy and sell schematics.

joan2 · « **Reply #126 on:** Oct 29, 2003 at 06:41 PM »

Quote from: akyatbundok on Oct 29, 2003 at 01:38 PM

Is it possible to convert the AUX input of my integrated amp into a power amp direct input?

I was hoping to use my old integrated amp as a separate power amp for my receiver but unfortunately it did not have main ins. This way i could use both the digital & analog outputs of my DVD player for playing movies & music respectively. When watching movies i switch to AUX to bypass the integrated preamp and use my receiver as the external preamp. When playing music i just switch to CD input to use the integrated preamp. I dont have to power up my receiver when playing music. I also dont have to switch speaker cables.

yes it is possible. or you can put in a 1/4 in phone jack that automatically by-passes the preamp out and make your power amp direct in possible, this way you don't disrupt the operation of your integs, besides it is more tedious to connect rca plug than a single phone plug imho..

joan2 · « **Reply #127 on:** Oct 29, 2003 at 06:44 PM »

Quote from: Gino on Oct 29, 2003 at 02:09 PM

Akyat, I asked Mr. Rivo about that and a pre amp output as well for my Rotel. He says it can be done as long as you have schematics for your amp. Now that's the problem. Hehehe.

if what you want is just to put a main-in/ preamp-out connectors i can do it even without the schematics....Oriental Diagram Center is the one selling all kinds of schematics and is right beside Eleshop....

joan2 · « **Reply #128 on:** Oct 29, 2003 at 06:52 PM »

Quote from: av_phile on Oct 29, 2003 at 02:27 PM

I remember buying some schematics from Raon. Can't remember the shop name though. I believe you can just ask some electronics shop about it.

av_phile,
are you into electronics too? i like your style of writing, very clear and to the point!!!

akyatbundok · « **Reply #129 on:** Oct 29, 2003 at 07:25 PM »

Quote from: joan2 on Oct 29, 2003 at 06:41 PM

yes it is possible. or you can put in a 1/4 in phone jack that automatically by-passes the preamp out and make your power amp direct in possible, this way you don't disrupt the operation of your integs, besides it is more tedious to connect rca plug than a single phone plug imho..

sir joan2, can i still control it from the front panel? i may need to occassionally switch between power amp & integrated amp operation depending on whether i watch DVDs or CDs. thanks!

i agree about sir av_phile's writing style, pwedeng pwede pang audio mag.

joan2 · « **Reply #130 on:** Oct 29, 2003 at 08:45 PM »

akyat,
what happens is that one stereo phone plug with rca dual jacks, will be used, now if you want to use the power amp only, all you do is plug it in, then when you are done just unplug it, and your system goes back to normal...i can even rig you switching breakout box so that all you do is just turn the knobs to whatever your setup requires...

Gino · « **Reply #131 on:** Oct 29, 2003 at 08:46 PM »

Joan2, can I have your contact info please. I want to have a main in (for using external preamps) as well as a preamp output (yung volume controlled).

I can be reached at [email protected]

joan2 · « **Reply #132 on:** Oct 29, 2003 at 08:51 PM »

akyat,
diagrams costs around 10pesos per page...
gino,
you can call me 6438957....in about 10 minutes....

joan2 · « **Reply #133 on:** Oct 30, 2003 at 06:46 AM »

akyat,
as follow-up to your questions about damping factors, another thread was started at diyaudio, this should be fine reading:http://www.diyaudio.com/forums/showthread.php?s=&threadid=22107

av_phile · « **Reply #134 on:** Oct 30, 2003 at 09:48 AM »

Quote from: Gino on Oct 29, 2003 at 03:39 PM

They have manufacturer model specific schematics?

Yes, they have it. each schematic has the corresponding brand and model number

av_phile · « **Reply #135 on:** Oct 30, 2003 at 09:52 AM »

Quote from: akyatbundok on Oct 29, 2003 at 04:59 PM

hmm... i'll go back to raon one of these days to look for schematics. i saw some schematics for sale on the web but i think i'd rather get it from raon. sir av_phile, any idea how much they cost? para lang wag tayo mataga sa presyo.

If i recall right, you only pay the cost of having it photocopied. The schematics are organized in some clear folder album. They don't sell them but you pay for their photocopies. That was so may years back. Don't know if they have the same selling scheme. Persoally, i wouldn't mind spending P100 foir the schematic i need.

av_phile · « **Reply #136 on:** Oct 30, 2003 at 09:58 AM »

Quote from: joan2 on Oct 29, 2003 at 06:52 PM

av_phile,
are you into electronics too? i like your style of writing, very clear and to the point!!!

Thanks joan2. I WAS an electronics hobbyist in my college days, having indulged in assembling SS amplifier kits and repairing just a few units as help to some friends.

Gino · « **Reply #137 on:** Oct 30, 2003 at 10:01 AM »

Ah...who do I look for? Certainly not a Joan2.

akyatbundok · « **Reply #138 on:** Oct 30, 2003 at 03:38 PM »

Quote from: joan2 on Oct 29, 2003 at 08:45 PM

akyat,
what happens is that one stereo phone plug with rca dual jacks, will be used, now if you want to use the power amp only, all you do is plug it in, then when you are done just unplug it, and your system goes back to normal...i can even rig you switching breakout box so that all you do is just turn the knobs to whatever your setup requires...

sir joan2, you mean you can put a 1/4" stereo phone socket at the back? then i can plug into it with my existing interconnects by using an adaptor like this?

does it mean you have to drill a hole at the back to accomodate the socket? i may want to use the headphone jack at the front.

thanks!

joan2 · « **Reply #139 on:** Oct 30, 2003 at 05:17 PM »

akyat,
yes, that is the connector, if you are willing to have the back of your amp drilled with a 3/8 in hole for the jack....the headphone jack in front will also be fine....

akyatbundok · « **Reply #140 on:** Oct 30, 2003 at 05:44 PM »

i think i'll prefer the socket to be at the back. my short interconnect may not be able to reach the front. ideally though, it would be nice to have some kind of switch at the front bcoz the back of the amp would be hard to reach in my case. i wonder if its possible to hijack one of the unused switches like the "softness" or "subsonic filter"? i can see that the AUX input idea may not be possible.

Leiko · « **Reply #141 on:** Oct 30, 2003 at 05:53 PM »

Toroids + EI transfos: can these be interchanged in an amp, provided their specs are identical? Are there other considerations (except space perhaps)?

Am considering replacing some toroids but so far can't find local winders of such.

joan2 · « **Reply #142 on:** Oct 30, 2003 at 06:50 PM »

Quote from: akyatbundok on Oct 30, 2003 at 05:44 PM

i think i'll prefer the socket to be at the back. my short interconnect may not be able to reach the front. ideally though, it would be nice to have some kind of switch at the front bcoz the back of the amp would be hard to reach in my case. i wonder if its possible to hijack one of the unused switches like the "softness" or "subsonic filter"? i can see that the AUX input idea may not be possible.

with the phone jack that we will use, there'll be no need for a switch, just pull out your phone plug and your integ returns to previous state, just by unplugging...as said before i can make you a box to accomodate your cables and put a switch there so that you only setup once, after that you only need to turn knobs to what ever you want to do with your sysmtem, this can be done...

joan2 · « **Reply #143 on:** Oct 30, 2003 at 06:56 PM »

Quote from: Leiko on Oct 30, 2003 at 05:53 PM

Toroids + EI transfos: can these be interchanged in an amp, provided their specs are identical? Are there other considerations (except space perhaps)?

Am considering replacing some toroids but so far can't find local winders of such.

possible to replce a torroid with an ei but not that simple, for a given va(volt-ampere) rating, the torroid will be about half the size and weight, althought footprint may be the same but the height will certeinly be different, so if you have a low profile unit, it will be difficult to purchase standard off the shelf transformer, you have to use custom made ei traffos....if you can give me an idea of your present torroid dimensions, and the power ratings of your amp then maybe i can help you....you can try Poodmon in Legarda, sampaloc, they are the oldest rewinding shop in manila that i know of...i can do the rewind for you if that torroid is not potted, otherwise, very difficult, besides i am very busy now doing computers...

Leiko · « **Reply #144 on:** Oct 31, 2003 at 04:34 AM »

well, this can wait. am actually contemplating converting 220 to 110v and reading from previous posts, may try higher rating (VA?) for more power.

btw, why do other amps have autovoltage features? is that a design of the transfo or is there another device in between the transfo and the mains cord?

joan2 · « **Reply #145 on:** Oct 31, 2003 at 01:34 PM »

Quote from: Leiko on Oct 31, 2003 at 04:34 AM

well, this can wait. am actually contemplating converting 220 to 110v and reading from previous posts, may try higher rating (VA?) for more power.

btw, why do other amps have autovoltage features? is that a design of the transfo or is there another device in between the transfo and the mains cord?

if you mean the amp can operate from 100 to 240 volts, this implies an smps (switching mode power supply), others have a multitap primary winding

Leiko · « **Reply #146 on:** Oct 31, 2003 at 05:40 PM »

i think that's the "smps". it is usually indicated by 110~220. I assume such also requires a multi-tap? How do I install an "smps"? or part ba ng transfo design 'yun?

sorry, this thing really confuses.

joan2 · « **Reply #147 on:** Nov 01, 2003 at 01:29 PM »

leiko,
smps uses another type of transformer, the chopper transformer, it is not the same as the convetional transformers that we know, it uses electronics, and is subject all by itself.....

many amps being exported from japan have a voltage selector at the back, they do this because it makes good business sense to them than making amps with fixed voltage tranformers, if a unit is to be exported to usa for example, then all they have to do is change the voltage tap, and to europe, they do the same thing, changing taps is more economical than changing transformers to fill up an order..also they do not need to stock up on each type and this means lower inventory, and a lower inventory means higher profits!!! are you still with me? many of the amps that we buy are made based on business decisions....

Leiko · « **Reply #148 on:** Nov 03, 2003 at 08:23 AM »

thank you Joan...

well, there's no shortcut to auto-volt. A swtiched/multi-tap will be economical indeed.

followup question: is there a way to protect a 110v component by adding a fuse (or something) that will break in case it's plugged accidentally to 220V?

akyatbundok · « **Reply #149 on:** Nov 03, 2003 at 10:21 AM »

About the speaker A & B terminals of an amp: Aren't they just connected in parallel?

I was wondering if this can be used to compare speaker cables. I'll plug cable A into speaker A, and cable B into speaker B. Then both will connect to one speaker pair with the HF/LF jumper in place. So when i switch to speaker A, i will be listening to cable A... when i switch to speaker B, i will be listening to cable B.

Now if i switched on both A & B with the jumper in the speakers still in place, will it short my amp? Note that the + and - aren't touching, just A+ to B+, and A- to B-. Well actually i know the answer to this one coz curiosity got the better of me and i couldnt resist. Not the most scientific procedure that, risking a short like i did, but in case people out there are starting to get those bright ideas, at least the gurus here could warn them.