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rmihai 9th September 2005 07:31 PM

Amplifier kit for my needs? Please, help - TY
Hi all,

I've decided to build THE amplifier of my dreams. I am looking for a kit and I need your help.

First of all - Solid State, class AB or Class A up to 10W or so and AB after.

What I will need this amplifier to do:
- frequency range: lows 16 Hz (-6db or better), highs -3db @ 50 Khz and -6db @ 100 KHz
- power output: 100W continous in 8 ohms and 250W at peaks!!!
- impedance: stable between 5 - 16 ohms
- distortion: max 0.01% up to 10W, max 0.1% up to 100W, max 1% up to 250W

I guess that the 250W requirement at peaks might be a strech. And because I do not want the other parameters worsened, then I can manage with lower power at peaks. But that should be at least 140W.

I think this will be the big trick of this amplifier - to make it able to reach 250W at peaks, but keeping the distortion below 1%.

Please let me know of the existence of ANY kit (or design) that will match my requirements.

Thank you very much

PS If I will be able to use the Hitachi Mosfet will be great. If not, I am sure there are other great FET around.

CBS240 10th September 2005 01:23 AM

100Khz eh? Sooooo you want to build a radio transmitter.:confused: If you can hear 50-100Khz, your ears are much better than mine.:cannotbe:

bjackson 10th September 2005 03:02 AM

I think that the answer is just making an amp that delivers 5% distortion at 500 watts, at 250 watts it should be very clean :)

In my experiance, over building is the secret to clean power.

Also, I don't know what source you are using, but redbook pretty much has a brickwall filter at 22Khz, and unless you have some CRAZY ears, you probably can't even hear that high :)

rmihai 10th September 2005 11:57 AM

I use as sources:
- a tunrtable
- a SACD
- from time to time a DVD-Audio player.

Reagrding your comments if I can or cannot hear 100Khz - I think all of us can "perceive" them, even though we are thinking that we cannot hear them with the ears.

AAK 10th September 2005 03:41 PM

Hi rmihai,

I just may have what your looking for. Back a few months ago I started my own little kit operation that unfortunately has been put on standby for the moment. I do have a few assembled 100 watt amplifiers for $249.00, a few already packaged unassembled boards with parts and heatsinks available for $199.00, and if you prefer I'd be glad to sell you just the boards with BOM and assembly instructions for $30.00. Keep in mind that purchasing all the individual parts in single quantities will cost you more the first two offerings. The assembled boards where built to make sure that I'd catch any problems instead of my customers. I built 12 boards and luckily every single board worked the first time with less than 15mv DC offsets. Not bad!

You can visit my website at, which is far from completed, but you can get amplifier specs, and some pics. Missing on the website is the amplifiers THD which I finally got around to measuring last week. The THD measured at better than 0.005% into 8 ohms at 110 watts rms and about the same into 4 ohms. You can also find more info on the thread I created back in may.

I hope to here from you or anybody else. These are great sounding amps that should be playing in somebodies living room instead of collecting dust.

Best regards,


rmihai 10th September 2005 06:58 PM

Hi, I looked deeply into your design and comments. I have to say that I like it - except that you are using BJT instead of MOSFETs.

What do you think? Maybe you can help me with a board for MOSFETs.

Let me know (pm me).


Byrd 10th September 2005 07:27 PM

rmihai - I find it a bit odd that you are wanting to build an amplifier to certain specification - instead of wanting to build one that sounds good and meets some need. There is alot more to an amp than weather or not it uses MOSFETS - alot of esoteric amps use BJT's with great success. You also have not specified how the THD is to be measured, @ 1khz, over the full 20 to 20khz range or what? How about SNR & again what type of measurement do you want?

You state that you can percieve this 100Khz - what speakers are you using to produce this signal? Perhaps you think you may be able to percieve it from the amplifier itself. I would imagine that any 100Khz signal that can be percieved is simply the result of IMD and is infact causing degradation of the signal.

Rather specify what the application is, what music you listen to, what kind of speakers you have, and if you have heard any amplifiers that you like what they are.

rmihai 10th September 2005 07:39 PM

Good points Byrd, and I have to agree with all of them. Being concise, sometime, is not helpful.

Yes THD measured @ 1Khz, preferablly not over the full range, but rather punctual.

SNR of course, all of us would like to be as bg as posible. I would like to be 144 db - is this posible, I doubt. I would be happy enough to be over 100.

but, in the end you are right - the music is that matters.

Before everything I would like to be as emotional, stiring and "musical" as posible a solid state can be. Specs are on the second stage from this perspective.

My speakers are custome designed by a retired long time speaker designer (do you remember ESS?). The speakers have the following parameters:
Impedance: 8 ohms
Minimun impedance: 5 ohms
Sensitivity 83 db!!!
lows: -6db @ 16Hz
highs: - 3db @ 40 KHz

What amplifier I liked. Well, very good point. I like tube amplifier. I listened extensivelly in the past Leak Stereo 60, Marantz 8B, McIntosh MC-75, and Dynaco ST-70. I loved them, but I would prefer to stay in the solid state from now on.

From the solid states I listened to different dealers and persons couple that I really liked:
- CHORD SPM-6000
- EAR M-100A
- THETA Citadel

Byrd 10th September 2005 08:04 PM

I very much doubt that you will be able to get that sort of SNR :bigeyes:

I have built the Leach amp and love it compared to for example NADs as well as a German "high end" MOSFET amp. It does 120 - 150 into 8 and 240 - 300 into 4 depending on powersupply and configuration. It is class AB.

Have a look @ this thread -

There is also a LM3886 amp that is being touted around at the moment which from all accounts sounds brilliant - however I have not heard this one myself but do plan on trying it out. I did not enjoy the standard "Gainclone" amp.

See this thread

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