Hiraga "le monstre"

[danieljw]

Hi All....

Yes its after midnight...

Just put some bits on the le monstre take 2.....

this time it has special bits on it....

all 0.5 W 1% resistors are tantalum or should i say - unobtanium
the two 5W power resistors are metal oxide non inductive...

the caps are ELNA Cerafines, the transistors are all matched originals, the JFETS are all matched originals, the output stage is the only thing non original it is upgraded to Sanken 2SA1186/2SC2837... much faster / lower Cob.

i superglued the small signal stuff together to enhance thermal tracking.

any how i need one more part which is the dc offset trimpot i will get a multiturn one tommorrow....

then its time to power up this little beasty...


-Dan

[Lumba Ogir]

Dan,
extremely nice (and genuine) output devices. Who's idea was it anyway?

[danieljw]

Thanks Lumba,

Just some forum guy - you wouldnt know him

[njepitt]

Dan: Nice job on the boards!!

Cheers

Nigel

[danieljw]

thanks mate,

will elt you guys know the results with the tantalums/sankens etc

[danieljw]

Just fired it up in my break....

Had to trim the bias down from 2.4A !!!!! adding a 1k in parallel with the existing 1K biass resistor yeilds 1.01-1.05A stable.

I did notice a couple of things if anyone is build one.

if you wait for the amp to get stable once you have set the one amp bias you can achieve <10mV with a 25 turn pot easily. with quite low drift. +/- 5mV

The bias level is quite critical for stability at 8R high power at high frequency.

ie if you have 2+ Amps bias on this one it is/was not stable at >20kHz with max output. (i think the 716/756 pair begins to become saturated)

once you have 1 Amp... the amp is very stable. I was able to achieve over 1MHz.

I will post some Scope/MSO pics when i get a chance.

-Dan

[danieljw]

Ok....

to save people who dont want large-ish images loading please see here for the le monstre MSo shots.

notice these is some ringing on the square waves at higher frequencies.

I will work out a cure for this. however i think it is just the measurement setup leads etc.

http://s300.photobucket.com/albums/n...urrent=000.jpg

-Dan

[neazoi]

Daniel,
So the PCBs work fine, I am very glad about it

I just got some shinkohs and I will soon post some components for selling if anyone wants to build this at a lower cost.

I have found greater wattage shinkohs (1-3W) but I have found all of them! VERY costy though...

I have some questions about your build.

Firstly, how you sold the input transistors together? Is it some special paste or just the standard white ceramic thermocouple paste?

Secondly, since I am at the final stage of building it too as you know, I would like you to describe in details the bias tuning process (where you connect the ampmetter, what adjustments, what values etc, is there any case of burning out the transistors if bias is wrong for a lot of time etc).
I think it will be fery helpfull for me as well for the other members that build this monstre

So you are building it using only batteries or mixed mode?

[danieljw]

Daniel,
So the PCBs work fine, I am very glad about itYes very happy they are nice and neat thanks !!!!

I just got some shinkohs and I will soon post some components for selling if anyone wants to build this at a lower cost.good idea

I have found greater wattage shinkohs (1-3W) but I have found all of them! VERY costy though...well done they are quite hard to find all the right values !!!!

I have some questions about your build.

Firstly, how you sold the input transistors together? Is it some special paste or just the standard white ceramic thermocouple paste?i used a tiny dot of super glue

Secondly, since I am at the final stage of building it too as you know, I would like you to describe in details the bias tuning process (where you connect the ampmetter, what adjustments, what values etc, is there any case of burning out the transistors if bias is wrong for a lot of time etc).
I think it will be fery helpfull for me as well for the other members that build this monstrei just tested it today. and the bias started at 2.4A which is more than double. the temp rises quite quickly however it is not thats dangerous as long as its only for say a few second or so. the value which gave me 1.01-1.05A bias was 500 Ohms. my suggestion is start at 1k and decrease until you get 1A using fixed resistors. in paralell

So you are building it using only batteries or mixed mode? I just tried it with a lab supply... i will try with batteries when i can afford some !!!!!!!!!!!!!!! let me know how your building goes !!!!

[neazoi]

Just a quick question (a bit silly though, but just to make sure)
Where do you connect the ampmetter to measure the bias?

Originally Posted by danieljw

Daniel,
So the PCBs work fine, I am very glad about itYes very happy they are nice and neat thanks !!!!

I just got some shinkohs and I will soon post some components for selling if anyone wants to build this at a lower cost.good idea

I have found greater wattage shinkohs (1-3W) but I have found all of them! VERY costy though...well done they are quite hard to find all the right values !!!!

I have some questions about your build.

Firstly, how you sold the input transistors together? Is it some special paste or just the standard white ceramic thermocouple paste?i used a tiny dot of super glue

Secondly, since I am at the final stage of building it too as you know, I would like you to describe in details the bias tuning process (where you connect the ampmetter, what adjustments, what values etc, is there any case of burning out the transistors if bias is wrong for a lot of time etc).
I think it will be fery helpfull for me as well for the other members that build this monstrei just tested it today. and the bias started at 2.4A which is more than double. the temp rises quite quickly however it is not thats dangerous as long as its only for say a few second or so. the value which gave me 1.01-1.05A bias was 500 Ohms. my suggestion is start at 1k and decrease until you get 1A using fixed resistors. in paralell

So you are building it using only batteries or mixed mode? I just tried it with a lab supply... i will try with batteries when i can afford some !!!!!!!!!!!!!!! let me know how your building goes !!!!