Leach amp vs Quad vs others

[jondoe]

Hello everyboddy.
I am about to build myself a 3way active speaker (stereo).

I saw earlier that the Leach amp is very popular and from my knowledge is also very good.
I heard people saying Quad707 is the ultimate in virtuosity and i know it is one of the best amps out there.
I also heard that Anthony E. Holton's amps are great (especially for hi power).

My question:
Which one of those should i build ?
I mean, i heard that the Leach is especially good for subs while the others, i don't know.
I need max 200W/8ohm low distortion, and the amps will be used up to 100W with some active limiter on the inputs so they won't be anywhere near clipping.
I read somewhere on Mr. Linkwitz's site that it's a very good idea to use the same type of amp for all speakers so i intend doing that.
I need the schematic to need as little as possible tuning (here the Quad wins) and to be as stable as a rock for i don't have access to any kind of oscilloscope (i used to when i was young, oh man time flies, eh ... , whatever ... ).
I also have zero experience with MOS transistors in audio (allways used them for switching) so i might be tempted for the BJT schematics since i've done some audio work with them in my teens.

So what can you recommend me ?
Thanks for the time taken to answer.

[still4given]

I just built a P101 from ESP Audio .
It was very easy to build, the PCB's are reasonably priced and it doesn't need any exotic parts. It is a MOSFET amp if that matters. The MOSFET's are still available. It is rated at 200W@8ohm. I thinks it sounds wonderful. It needs 70V rails for the 200w but I run mine on 45-0-45 Toroid and it plays way louder than I need.






I built this as a three channel. One board is not installed in the pictures, but is now. Unless you are planning to run this thing full out, you don't need anywhere near as large of heatsinks as I used. Even running it hard with all three channels it barely gets warm.

I'm presently using the third channel to drive my JBL B360 Subwoofer while the other two handle two JBL 4425's and it works very well.

Blessings Terry

[AndrewT]

Hi,
some of our contributors have said the Leach is low in the bass department.
I have not heard one but the toplogy should not give rise to this.
Carefull attention to PSU and time constants should give it as much grunt as any other.
IMO you can mix topologies and/or manufacturer and/or power for active amps. Can I suggest full classA for the treble at half bass power and hi bias classAB at 75% of bass power for the mid.
You can fudge these numbers a lot once you know your crossover freqs.
Some suggest equal gain for all amps but you can even tailor this to match unequal speaker sensitivity.
Lots of scope for design input, good luck and keep us informed.

[jondoe]

still4given,
I'm aware of your amp(s). I saw these pictures some time ago here on the forum (and in fact i use to show them to some friends of mine as how they can design a case that's functional and nice looking too, with available parts).

I also like the P101 but i have a generalized problem in paying for stuff that comes from international space. I mean, it is hugely complicated (unless if you're willing to pay the double or you have connections at the customs so that they don't think you ordered atomic bomb spare parts and escort you with the police or charge you accordingly. somebody i know ordered some MJ samples from ON semi and the customs office called him to give clarifications on what was in the package -it was transistors - oh, then you have to pay 60$ taxes, needless to say the order+shipment was something like 20-30$ so he said goodbye and showed them 1 finger).
Another thing which is somewhat related, i can get only 2SC5200/2SA1943 pairs that i can know for sure they're the real thing. Even price cannot guarantee you're not getting a fake (shops around here can't allways tell if they have genuine merchandise).
That's why i thought about the Leach amp.

AndrewT,
My PSU has one 1000W/2x57V/20A trafo with 4x17400 Sprague screw terminal caps for the sub (i could increase this number, but for now, it's OK) and 2x800W/50V/25A trafos (one for each polarity) for the mids and his (i may buy another trafo to separate the mids from the highs, but these trafos i allready have and for now they're OK). Each amp (mid & hi), even if it is connected to the 2x800 trafos has it's own rectifier and caps (i plan on using the same tipe of caps for these).

I don't plan any class A (the electric bill is not going away) but will do some high bias AB.

From the speakers that i can get, these are the crossover freqs:
LO < 100Hz at 12db/oct
12dB/oct at 100Hz < MID < 24 dB/oct at 8Khz
HI > 8KHz at 24 dB/oct.

One more question.
If i will opt for the Leach (which i most probably will) what is it's usual DC output error since i plan to use a SuperTweeter directly coupled to it's output for the hi part ? If it's too high i might need to pair the transistors or use a DC servo (which is kinda extreme).

Thanks again.

[still4given]

Hi Jon,

Sorry to hear that. I forget sometimes how good we have it here in the States.

I'm almost finished with a Leach Superamp. If I get it done in time to help, I will post my findings.

I am using a 55-0-55 trannie and 4 100v/10Kuf filter caps. I used the original Leach foil pattern and made my own boards. You can see them here.

Hopefully I will get it up and running this week sometime.

Blessings, Terry

[jacco vermeulen]

Or how good we have it here !

Just a week ago i aquired 100 original Toshiba 1301/3280 for pennies and cents the piece.
Little brothers of the 1302/3281.
Ordered for repairs of the first digital integrated amplifier, the Philips DFA888, around $800 msrp in 1990.
Apparantly Philips daughter company in Japan, Marantz, handled the logistics of the Japanese output devices for the DFA888, as the accompanying label states Marantz, Japan.

Thinking of trying these on the Leach too.

Did i already mention i just love the Web ?

How do you know you will not receive fake MJ's for the Leach, Dead One in Romania ?
The MJ15003/15004/15015/15016/15024/15025 have been faked too, i noticed.
How about if someone private sent you an envelope, JonDoeIY ?

[sam9]

Given your situation (no international purchases), I would suggest the Leach amp for a simple reason: the circuit and it's construction is extensively documented on the web and common parts are used.


Otherwise, I would have recomended the P101 for a multiple amp project as it is very compact thus making the assembly into the enclosure easier.

[jondoe]

Helluo Jacco,

How do you know you will not receive fake MJ's for the Leach, Dead One in Romania ?
The MJ15003/15004/15015/15016/15024/15025 have been faked too, i noticed.

Ohh my. Actually i'm 99% sure everything here is 99% fake. No s**t. Really. Buy a screwdriver - it's fake (i bet you can't imagine this one).
Buy a rezistor - it's fake. Just about everything you can easily get your hands on is like this (a little less locally made food products, not imported ones).

Oh, and check this out. I can get "real" MJ15003/4 for roughly 8andsome $$$. This price is the same for every living "real" tranzistor out here. Kinda cheap, ha ?

I can only be sure on the 2SC/2SA because somebody over here gets them directly from the manufacturer but about 9$/piece is a little cheap for me ( i can buy, hm, let's see, 8 from my monthly payment in order to not go bankrupt, but that's it for the next 2 months).

How about if someone private sent you an envelope, JonDoeIY ?

OOOOOHH. I'm planning dreaming about this and a couple of brunettes tonight when i go to sleep. But like every good dream, i'm suddenly taken out of it by Mr. Smith asking me: Ok Mr. Anderson who calls himself Neo, what kind of subversive devices have you in this envelope ? Have you gone to the enemy? You must pay for this somehow (cash or otherwise). And then he tries something that i can't describe. Better yet, watch southpark when Cartman gets somethin' ******** up his ******* by the aliens.
OOOOOHH. I better not sleep tonight. Arghhhhh

PS
If i receive ("unconceivable") such an envelope, how is the "return receipt" "cough" "cache'r'somthin' " get back to the sender ? Well, in the case he/she's not Mother Teresa.

sam9,
I like Leach. I like gettin' my hands dirty (just gotta have something to work with). I never did a simple design in my life (for me that is, allways for my pals). I never found exactly the parts needed so i improvised. I'm the master of improvisation, alltho sometimes it's not worth it (like now). When i get a blown, say, digital source selector that costs let's say 200$ (yeah, happened to a friend on a techniks amp) i go and buy parts for about 20$ and make a same function boad and place it on an IC sochet instead of the original IC and it works (TM).

So i definitely will built Leaches (sometime in the unforseable future)

Hey, allmost forgot,
THANKS

[jacco vermeulen]

JonDoe,

What a coincidence, i saw those brunettes too last night.
I guess living in Romania is sort of like Vegas ?

If i can help you with some parts and there is a chance that you will not be invaded by an alien, sending an envelope is easy.
i suppose people from Romania can send letters abroad too ?
Doing someone a favor is the cheapest way of feeling good about yourself.
If i were Mother Teresa, i'd be a drag queeen.

[jondoe]

Man Jacco, you are really somethin' (not that i didn't really know that from reading this forum).

What a coincidence, i saw those brunettes too last night.

Man i'm psykic.

i suppose people from Romania can send letters abroad too ?

AAHHmmm... Well, check this out. I once upon a time (about 5 years ago) saw some pretty colorfull pictures on the internet that were called Linux. I said nice program. Of course it was not such thing but... whatever. I want it. But how do tou get it ? The net back then was paleolithic for simple people like me.
- So i said, VISA ? what's that ?
- The BANK : a minimum of 5000 USD deposit and you have one.
- Me: U gotta be fc**n jokin'
- Bank: No dude, now split ...
Went to Western Union, OH, wait, there's no such thing...
Went to some international bank: payment is 30% of the amount sent but not below 20$. Huh ? My transport was 3$/3CDs and 6$/shipment
You gotta be kiddin' no?
Some banker employee said: Hey, make yourself a bank and there you go ...
Me really pi***ed by then.

So i saw "Money Order" (I discovered later that Money order ment some sort of check, which is kinda back to VISA)
Oh Great, my language, i'm gonna send some money.
Grabbed a brand new 10$ Bill, stick it in a brand new holiday card (with no text on it, just some flower picture) together with the order and sent to the USofA.
4 weeks later, VOILA, MY brand new CDs.

OK, ok, but what's with the greeting card you may ask ?
Well, you never know how some wacky postal worker might have seen the bill through the envelope but not through a 1.5 mm thick paper folded in two.

So yes, we can send/ receive letters.
(I can't speak about time machine electronic parts since i haven't received such a thing but the CDs came fine. Now i hear that postal service is improved somewhat, some pretty rich guy bought 1 pair of Shivas for 800$/piece i guess and they arrived ok, but i know only of this guy, everybody else is scared of the premium to spend).

Doing someone a favor is the cheapest way of feeling good about yourself.

Then i would be feeling extra good for all my friends which have (by the way extra good quality) salvaged parts given by me from ancient equipment dumped from abroad locally as scrap. But that's ancient history and my friends are gone slim as my stock of these parts go down.

If i were Mother Theresa, i'd be a drag queeen.

If you say so...

Happy whatever.