Hi WonderChild,
I agree with the others... find a used monster from the 1970's (Marantz, Pioneer, Sansui, etc.) for cheap and spend your money on a speakers and a CD player. Heck, you're on the same island as Rod Elliott... he has some good amps. Build one of those or find someone who is willing to part with one.
We're not trying to reign on your parade... just trying to save you the lessons we have all learned the hard way. How hard? Try hard earned money.
That said, you need proof so I'll attempt to provide...
1) 2 x 80watts continuous. Check the back of the unit for it's power consumption... if it draws less than 160W from the wall, then the spec is false. I suspect that will be the case. You should go see for yourself.
2) Peak music power output. There are varying definitions of this versus RMS power, but let's just say for arguments that it might be able to deliver this. The problem with this is that there is no reference for how long the peak lasts. Is that 1 millisecond or 1 microsecond. I doubt it is 1 sec since that starts to get into the realm of continuous which we are told is around 80W. IME any equipment that quotes PMPO isn't even worth looking at... just a bunch of overblown numbers.
3) Separate left/right supply. But wait... only one large toroid. That is one single supply. Technically they could say that every stage has its own supply, but that would be easily read as embellishing.
4) THD 0.5% from 20-16kHz. For solid state, 0.5% is very poor. It is what happens with the entry level AV receivers when you crank them past 50%. My very old Marantz is 0.08% from 20-20kHz. My active monitor run 0.05% from 20-20kHz. You want hear what that's like, go to the pro shop and listen to the Tannoys.
And what happens from 16kHz to 20kHz? That range holds the wonderful sizzle of cymbals and snares. It contains a lot of the upper harmonics of female vocals. Maybe you can't hear up there any more, but if you have already lost your hearing at those frequencies then you have been in the mosh pit far too often.
Lastly, go listen to it in the store. But before you push play, try this test... with the CD player disconnected. Just turn the volume all the way up and put your ear to the speaker cones. There should hardly be a sound... better if no hiss at all. That's the noise floor. Good equipment has a noise floor that is cannot be heard. Check this with a cassette deck. Play a blank cassette... and listen to the hiss. Kind of the same thing only less power.
ensen.
I agree with the others... find a used monster from the 1970's (Marantz, Pioneer, Sansui, etc.) for cheap and spend your money on a speakers and a CD player. Heck, you're on the same island as Rod Elliott... he has some good amps. Build one of those or find someone who is willing to part with one.
We're not trying to reign on your parade... just trying to save you the lessons we have all learned the hard way. How hard? Try hard earned money.
That said, you need proof so I'll attempt to provide...
1) 2 x 80watts continuous. Check the back of the unit for it's power consumption... if it draws less than 160W from the wall, then the spec is false. I suspect that will be the case. You should go see for yourself.
2) Peak music power output. There are varying definitions of this versus RMS power, but let's just say for arguments that it might be able to deliver this. The problem with this is that there is no reference for how long the peak lasts. Is that 1 millisecond or 1 microsecond. I doubt it is 1 sec since that starts to get into the realm of continuous which we are told is around 80W. IME any equipment that quotes PMPO isn't even worth looking at... just a bunch of overblown numbers.
3) Separate left/right supply. But wait... only one large toroid. That is one single supply. Technically they could say that every stage has its own supply, but that would be easily read as embellishing.
4) THD 0.5% from 20-16kHz. For solid state, 0.5% is very poor. It is what happens with the entry level AV receivers when you crank them past 50%. My very old Marantz is 0.08% from 20-20kHz. My active monitor run 0.05% from 20-20kHz. You want hear what that's like, go to the pro shop and listen to the Tannoys.
And what happens from 16kHz to 20kHz? That range holds the wonderful sizzle of cymbals and snares. It contains a lot of the upper harmonics of female vocals. Maybe you can't hear up there any more, but if you have already lost your hearing at those frequencies then you have been in the mosh pit far too often.
Lastly, go listen to it in the store. But before you push play, try this test... with the CD player disconnected. Just turn the volume all the way up and put your ear to the speaker cones. There should hardly be a sound... better if no hiss at all. That's the noise floor. Good equipment has a noise floor that is cannot be heard. Check this with a cassette deck. Play a blank cassette... and listen to the hiss. Kind of the same thing only less power.
ensen.
Now you've got serious offer of a trusted name brand without the hassle of learning solders.
whats new if it is not true hifi (let alone hi end). better to get old and running gear, and you are sure it has been running ever since that get a new one that could be the lemon of the bunch.
purplepeople have provided a basic test of good amp design.
whats new if it is not true hifi (let alone hi end). better to get old and running gear, and you are sure it has been running ever since that get a new one that could be the lemon of the bunch.
purplepeople have provided a basic test of good amp design.
the_wonderchild said:
Wonderchild.
Here's a URL:
http://www.amchome.com/Merchant2/me...ode=3025a&Category_Code=Integrated+Amplifiers
It's a nicely made bit of kit. I prefer the sound of my home built gainclones though!
The website says $400 new (that's US dollars too........)
I'm about to get on a plane to England via Singapore, so we can discuss a price when I'm back nearer a PC, or you could email me:
steve@murrey-skurr.com
SteveM
well, i can say i'v learned the hard way with those koda, klf or sutch amps.. i bought a dolby surround amp once, off qxl.com and it was simply the worst i have ever heard, really! i'v got creative pc speakers that sound better..
important to remember that you get what you pay for, particulary if you'r buying new stuff.
btw i was 15 when i bought the amp too..
im 17 now, and i'v learned my lesson. im building gainclones and diy speakers. i dont have a single regret.
important to remember that you get what you pay for, particulary if you'r buying new stuff.
btw i was 15 when i bought the amp too..
im 17 now, and i'v learned my lesson. im building gainclones and diy speakers. i dont have a single regret.
BlackDog said:
Oha!
My father has one of those, I bought it in London for him, some years ago.
New, but with a good price, better than here at the time.
Not bad at all in standard form.
And with some changes in the preamp, very good indeed.
Much better than the Denons and Yamahas.
Really, those 30W RMS seam like much more.
Wonderchild, this is a good option for you.
Oh Gosh!
I thought I'm the youngest in this forum...
But he is an year younger than me...
So now I'm 2nd youngest
I gotta finish off my tube amp before he catches up...
Hey wonderchild, you've got a big advantage!
You got a lot more time to learn stuffs while my time is restricted by HUGE amount of school works and EXAM PERIODS (seriously, I only get around 30 mins per day to do whatever I want)...
Anyway, nice to see you mate!
Cheeeeeeeeeers,
JayJay
I thought I'm the youngest in this forum...
But he is an year younger than me...
So now I'm 2nd youngest
I gotta finish off my tube amp before he catches up...
Hey wonderchild, you've got a big advantage!
You got a lot more time to learn stuffs while my time is restricted by HUGE amount of school works and EXAM PERIODS (seriously, I only get around 30 mins per day to do whatever I want)...
Anyway, nice to see you mate!
Cheeeeeeeeeers,
JayJay
Re: Oh Gosh!
I turn 16 in October so then you could say we are practically the same age.
I also usually get restricted from work but not as much as you probably would, although i do Year 11 Psychology even though i am in Year 10.
Anyways nice to meet ya, and by the way don't worry about me catching up to you, i'm still learning and taking more of an interest in DIY speakers.
jamesjung21 said:
I thought I'm the youngest in this forum...
But he is an year younger than me...
So now I'm 2nd youngest
I gotta finish off my tube amp before he catches up...
Hey wonderchild, you've got a big advantage!
You got a lot more time to learn stuffs while my time is restricted by HUGE amount of school works and EXAM PERIODS (seriously, I only get around 30 mins per day to do whatever I want)...
Anyway, nice to see you mate!
Cheeeeeeeeeers,
JayJay
I turn 16 in October so then you could say we are practically the same age.
I also usually get restricted from work but not as much as you probably would, although i do Year 11 Psychology even though i am in Year 10.
Anyways nice to meet ya, and by the way don't worry about me catching up to you, i'm still learning and taking more of an interest in DIY speakers.
Man, I was just joking!
I ain't got any time to work on the tube amp right now...
Exams are coming up in a week or so...
Is it CIE (Cambridge International Examination)??
My friend really really really wants to learn psychology, but it's not available in our school as CIE course...
The guy talks about psychology almost 24/7
I'm currently learning year11 course.
Oh, wait a minute... I gotta be careful whenever I say something to you, cos you'll probably analyse my character
Cheers,
JayJay
jamesjung21 said:
My high school allows me to do a Year 11 subject (called VCE here in Victoria, Australia) while i am in Year 10. Thing is though, i still do the work and exams for that subject because for that subject i am considered a VCE student.
Oh, wait a minute... I gotta be careful whenever I say something to you, cos you'll probably analyse my character
LOL
koda amplifier
Wonderchild:
I´m from buenos aires, in the deep south...
A pair of years ago I bought the same amplifier that you describe, koda branded, as a bargain. Maybe 100 u$s dollars.
I opened the case and i became amazed with the amp´s innards: good quality metal film resistors, a very nice 250 w toroidal transformer, 20.000 uF per channel of capacitance via Rubycon standard electrolytics, a protection circuit based on relays, and very good Toshiba transistors -not counterfeit, but the real thing, and still sounding good-.
Really, I dont understand the economics of the manufacturer.
The source selector is connected via a rod to a switch in the back of the amp, near the inputs: nice touch.
The sound... in a first instance not so good. Hard, cold, electronic.
I supposed that the preamp section, based in ne5534 opamps, was the culprit. I disassembled it -its very easy, because is independent, in a discrete pcb, and connected to the power amp section via jumpers- and leave only 1 pot for the volume, 100k -cannibalized from the same preamp pcb-, in a layout that suggest some resemblance with a passive preamp, but inside the Koda case.
The sound became much more listenable, and the coldness described vanished.
Lately, I had made a discrete active preamp based in OPA 637-buf634, gain 2, using the Koda only as power amp: I´m very pleased with the results. A subjective opinion is relative, but I think the combo sound very good: better than a Rotel, for example.
In the input stage of the Koda power stage I suggest a swap of capacitors: the original electrolytics, 4.7 uF, must be changed for something better: maybe polyprops.
If you can afford the amp, buy it and experiment. It´s fun and experimentation what this game is all about.
Regards
Wonderchild:
I´m from buenos aires, in the deep south...
A pair of years ago I bought the same amplifier that you describe, koda branded, as a bargain. Maybe 100 u$s dollars.
I opened the case and i became amazed with the amp´s innards: good quality metal film resistors, a very nice 250 w toroidal transformer, 20.000 uF per channel of capacitance via Rubycon standard electrolytics, a protection circuit based on relays, and very good Toshiba transistors -not counterfeit, but the real thing, and still sounding good-.
Really, I dont understand the economics of the manufacturer.
The source selector is connected via a rod to a switch in the back of the amp, near the inputs: nice touch.
The sound... in a first instance not so good. Hard, cold, electronic.
I supposed that the preamp section, based in ne5534 opamps, was the culprit. I disassembled it -its very easy, because is independent, in a discrete pcb, and connected to the power amp section via jumpers- and leave only 1 pot for the volume, 100k -cannibalized from the same preamp pcb-, in a layout that suggest some resemblance with a passive preamp, but inside the Koda case.
The sound became much more listenable, and the coldness described vanished.
Lately, I had made a discrete active preamp based in OPA 637-buf634, gain 2, using the Koda only as power amp: I´m very pleased with the results. A subjective opinion is relative, but I think the combo sound very good: better than a Rotel, for example.
In the input stage of the Koda power stage I suggest a swap of capacitors: the original electrolytics, 4.7 uF, must be changed for something better: maybe polyprops.
If you can afford the amp, buy it and experiment. It´s fun and experimentation what this game is all about.
Regards
errare humanum est
errata: the new preamp is based in opa627, not opa637, that is unstable in low gain.
the configuration is something similar to Pavel Macura audio buffer, but with some gain and with an Alps pot at the input. You can make a search in other threads to see more about it.
Enjoy.
errata: the new preamp is based in opa627, not opa637, that is unstable in low gain.
the configuration is something similar to Pavel Macura audio buffer, but with some gain and with an Alps pot at the input. You can make a search in other threads to see more about it.
Enjoy.
the_wonderchild said:
I built a chip amp knowing nothing beforehand about electronics. It not really that difficult. The gainclones are not complicated and simply require careful assembly to avoid bad connections and shorts. There are many boards available if you want to keep it as simple as possible. I think Rod Elliot has a board for chip amps. After you have built a couple you will probably feel confident enough to try one of his bigger amps which will likely run circles around anything you could afford to buy.
Obviously you have to take extreme care when using electricity since one mistake could be serious trouble, but there is plenty of information about safety one the web.
I have no idea what this amp your looking at sounds like but many people here speak very highly of the chip amps. Check these out:
http://sound.westhost.com/project19.htm
http://www.decdun.fsnet.co.uk/gainclone.html
The second site in particulair is oriented to people who know nothing about electronics. You will find all the information you need.
Just be careful and read what people have to say about safety.
As for this amp your looking at, maybe it does sound great for the money. There is a lot of stuff coming out of China (i think this is, right? I didn't look to carefully) that are absurdly cheap for the performance you get. You've heard it so your probably the best to judge.
If it sounds good, well then youll have a nice amp until you get the upgrade bug. If you learn to build your own, you'll have a nice amp, plus a great deal of new knowlege, and a sense of accomplishment, which is probably the best benefit of all. I sure wish I knew about this stuff before I made decisions about my education and career. I might have taken a different path.
Good luck and have fun.
koda amp, modifications
Hola a todos. (Hi all...)
As suggested by Palesha, in a first instance I tried to swap Opamps in the pre section of the Koda amp. There were no major improvement in sound quality.
OPAS tested were OPA604, OPA134, OPA637 and OPA627.
Power supply is +/-18v, so opa637 and 627 ran very hot: in the verge of disaster, something terrible considering the price of these IC´s.
Opa604 performed a lot better in this respect, but only in the temperature aspect. The sound remained terrible.
Also, -and I think very important-, circuit layout is optimized for NE5534, a bipolar opamp whose optimum implementation is something different to fet input opamps as the Burr Brown chips described.
There is the tone control section in the way too -based, as the rest of the pre, in NE5534´s-, interacting in a way that, at least to me, was not good sounding.
And the whole pre section has too much gain to my liking, making too evident hisses and other distortions. That also limited the usefulness of the volume control, because of the very short range of control: it was imposibble to exceed the 09:00 hs position without clipping!
Then I decided to simply remove the pre section, as I did.
And I did it as follows:
Disconnected wires -2, shielded and jumpered- from the output of the source selector (at the back of the amp) to the input of the pre.
Disconnected wire -2, shielded and jumpered too- from preamp to power amp section.
Removed all input jacks, with a lot of caution a patience.
Substituted them with only one pair of good quality female rca jacks, gold plated, mounted in a tiny fibreglass board, and screwed that to the chassis, using the original holes for jacks and screws. It takes a little patience and some measuring, but it´s quite easy.
Removed the preamp section, pots, etc, from the front of the amp. Easy task.
Removed the rod that connects the source selector switch -located in the back of the amp, next to the input jacks- with the source selector knob.
Then, I cannibalized the 100k volume pot of the junked preamp, and made a variable shunt series attenuator: the variable shunt element is the 100k pot, the fixed series are a pair of 25k good quality resistors.
Power amp input impedance is 47k, so there´s no problem.
Then, the pot was mounted in the front of the amp, and the part of the fascia crowded with the tone control and source selector holes was neatly dressed with a piece of mahogany, to disguise those details.
That piece of wood is something special: I performed a process called ¨lustre a la goma laca¨ to embellish it, -I suppose that is the spanish equivalent to ¨french luster¨- ; the counterpoint between the original anodized front, and the red accents of the mahogany, is very eye pleasing.
Now, the amp looks as something entirely different -more highbrow-, of a quasi hig end pedigree.
And the sound is leagues better.
Maybe the Toshiba Sc5200´s transistors and the amplifier circuit implementation has something right in it, maybe the very good power transformer, or maybe all.
I don´t know.
But I like it. Cheap, fun, good, nice and rugged.
Something very rare in HiFi.
It´s a sort of power amp wit only 1 input and a volume control.
Minimalism, as they say...
In a second instance I decided to partner the amp with a opa627/buf634 pre -that I have mentioned in an earlier post-, and the results were stunning, at least to my ears.
But that is another story.
Cheers.
Hola a todos. (Hi all...)
As suggested by Palesha, in a first instance I tried to swap Opamps in the pre section of the Koda amp. There were no major improvement in sound quality.
OPAS tested were OPA604, OPA134, OPA637 and OPA627.
Power supply is +/-18v, so opa637 and 627 ran very hot: in the verge of disaster, something terrible considering the price of these IC´s.
Opa604 performed a lot better in this respect, but only in the temperature aspect. The sound remained terrible.
Also, -and I think very important-, circuit layout is optimized for NE5534, a bipolar opamp whose optimum implementation is something different to fet input opamps as the Burr Brown chips described.
There is the tone control section in the way too -based, as the rest of the pre, in NE5534´s-, interacting in a way that, at least to me, was not good sounding.
And the whole pre section has too much gain to my liking, making too evident hisses and other distortions. That also limited the usefulness of the volume control, because of the very short range of control: it was imposibble to exceed the 09:00 hs position without clipping!
Then I decided to simply remove the pre section, as I did.
And I did it as follows:
Disconnected wires -2, shielded and jumpered- from the output of the source selector (at the back of the amp) to the input of the pre.
Disconnected wire -2, shielded and jumpered too- from preamp to power amp section.
Removed all input jacks, with a lot of caution a patience.
Substituted them with only one pair of good quality female rca jacks, gold plated, mounted in a tiny fibreglass board, and screwed that to the chassis, using the original holes for jacks and screws. It takes a little patience and some measuring, but it´s quite easy.
Removed the preamp section, pots, etc, from the front of the amp. Easy task.
Removed the rod that connects the source selector switch -located in the back of the amp, next to the input jacks- with the source selector knob.
Then, I cannibalized the 100k volume pot of the junked preamp, and made a variable shunt series attenuator: the variable shunt element is the 100k pot, the fixed series are a pair of 25k good quality resistors.
Power amp input impedance is 47k, so there´s no problem.
Then, the pot was mounted in the front of the amp, and the part of the fascia crowded with the tone control and source selector holes was neatly dressed with a piece of mahogany, to disguise those details.
That piece of wood is something special: I performed a process called ¨lustre a la goma laca¨ to embellish it, -I suppose that is the spanish equivalent to ¨french luster¨- ; the counterpoint between the original anodized front, and the red accents of the mahogany, is very eye pleasing.
Now, the amp looks as something entirely different -more highbrow-, of a quasi hig end pedigree.
And the sound is leagues better.
Maybe the Toshiba Sc5200´s transistors and the amplifier circuit implementation has something right in it, maybe the very good power transformer, or maybe all.
I don´t know.
But I like it. Cheap, fun, good, nice and rugged.
Something very rare in HiFi.
It´s a sort of power amp wit only 1 input and a volume control.
Minimalism, as they say...
In a second instance I decided to partner the amp with a opa627/buf634 pre -that I have mentioned in an earlier post-, and the results were stunning, at least to my ears.
But that is another story.
Cheers.
as hell, more than anything else, not because of the +/-18v PSU voltage, but if you are using it with a gain of less than 5x.the koda amp experiment
ja ja ja!
I was very inexperienced in those days, -maybe two years ago- and now I´m only a bit better...
I´m a sort of experienced newbie, and my skills at electronics are rather crude.
I supposed that swapping opas was sort of ¨plug´n play¨, you know, substituting one thing with the other without a clue, and making no measurements, and only listening to the engender to seek that elusive good sound...or fumes...
poor OPAS...
But they survive, by miracle. Curiosity dont kill them, -my curiosity-, but I suppose they don´t have 7 lives.
I must admit too that, being anxiuos as I am, I have received a good dose of electric shock doin´ this DIY and patchwork thing, but no pain, no gain...
Well, now I don´t make heavy measurements neither: only impedances, voltages and things like that. Maybe in the future, if I got the time and the instrumental...
But at least take my time to read the forums, and the specifications of the chips, and some book.
And with the help of the knowledge of people like you I make my DIY tourneé. It´s fun. It´s interesting.
It´s what audio used to be in the past, I suppose.
But this amateur thing have it´s flavour; ...amateur, a word derived from amour, from love...
And that labour of love, despite it´s ¨dilettante¨ caractheristics, is what makes this diy thing enjoyable.
Cheers
ja ja ja!
I was very inexperienced in those days, -maybe two years ago- and now I´m only a bit better...
I´m a sort of experienced newbie, and my skills at electronics are rather crude.
I supposed that swapping opas was sort of ¨plug´n play¨, you know, substituting one thing with the other without a clue, and making no measurements, and only listening to the engender to seek that elusive good sound...or fumes...
poor OPAS...
But they survive, by miracle. Curiosity dont kill them, -my curiosity-, but I suppose they don´t have 7 lives.
I must admit too that, being anxiuos as I am, I have received a good dose of electric shock doin´ this DIY and patchwork thing, but no pain, no gain...
Well, now I don´t make heavy measurements neither: only impedances, voltages and things like that. Maybe in the future, if I got the time and the instrumental...
But at least take my time to read the forums, and the specifications of the chips, and some book.
And with the help of the knowledge of people like you I make my DIY tourneé. It´s fun. It´s interesting.
It´s what audio used to be in the past, I suppose.
But this amateur thing have it´s flavour; ...amateur, a word derived from amour, from love...
And that labour of love, despite it´s ¨dilettante¨ caractheristics, is what makes this diy thing enjoyable.
Cheers
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