Melcor 1731 PCBs.. Where we left off....

Hi!

Cricklewood Electronics here in uk had no BD136/7 transistors, but gave me BD139/BD140 instead. All the data seemed the same to me in my ignorance, but what does anyone else think?

Any clues?

Andy P

I think that those would work, but check the pinouts!

BD135 = BD137 = BD139
BD136 = BD138 = BD140

in terms of pinout. The main difference is that BD139/140 can take more Vceo.

I just use them on mine.

cheers!

from Tony:

concerning the pins, i wouldn't mind sharing an order with any of you...
the minimum quantity at my local electronicstore was 500 and a long time before delivery...

Click to expand...

How did your pin-finding turn out ? If you got that bag of 500 I'd be willing to buy some from you.

Thanks / groeten,

Peter

I'm planning to stuff 4 Melcors... can 1/8W resistors be used? or is 1/4W ok?

Greg,

I haven't built a Melcor yet, but I used 1/8th watt resistors on Fabios 2520 RC v1's. They work fine so far! MUCH easier to assemble. I started with 1/4Watt, and de-soldered and started again! No smoke so far . . . . Just Sweet top end from my API 553 inspired switchable frequency passive eq. Haven't build the LF bit yet, due to a lack of Inductors/Funds, but i am smitten with the open, sweet highs. . . . Just like the real deal. Gonna build some Melcors this weekend to compare.

Good Luck!

Andy P

How crucial is the value of R11, R12?
this is 8.2R btw.

Not all suppliers have resistors under 10 ohm, would be stupid to try putting 2 in parallel.

:guinness:

Tony.

Hi Peter,

I havent hear dback from mouser so far??
I'll try to ad those milmax pins to our order.

:sam:

Tony

I havent hear dback from mouser so far??
I'll try to ad those milmax pins to our order.

Click to expand...

Hi Tony,

Sounds good - what do they have for minimum amount ?
I have eight PCBs upcoming from from Jay so could use about 60 sets (pin+hole) in total.

If it's a hassle or potentially confusing for the Mouser-order, doing without those pins would be OK for me as well, since I figure I'll probably install these opmaps permanently (fixed) in a motherboard.
That's not as neat, but would be OK for me - so if it turns out these pins are hard to get or when they only come in insane minimum quantities...

Bye,

Peter

How crucial is the value of R11, R12?
this is 8.2R btw.

Click to expand...

I'd try to get the intended value. As you'll know, higher valued resistors here will reduce the quiescent current a bit in the output-section.

I must say I'm a bit puzzled by the Melcor-schematic though - there's only one diode in front of the output-section - which has the same voltage drop as the sum of 1Vbe-NPN + 1Vbe-PNP + Iquiesc*(R11+R12). One would say that without a signal the output-section is about 'off' but I must be overlooking something.

Bye,

Peter

alo
fired my bauman api,with 1731 melcor,after a stupid problem i had,and found it works damn fine.
no noise,lots of gain,and after a quick test with a api3124+,the sound of both units it is almost identical,with melcor sounding more forward in the high freq.3124 sounded more soft.i had melcor with +-15vdc.
as the api 3124,the pad was needed on almost loud sources.
these listenings were done with a u89 on vocals,and d112 on a bass trough a super lead and a ampeg cabinet.
when i can give more details,i will tell you.
thanks fabio.
best regards
pedro

Hi Pedro,

Just curious, what in- & out-TX did you use ?

Peter

yeah Pedro, this is great news! :thumb:

:sam:

Tony

alo
tx in it is cinemag75101apc.
tx out it is sowter api clone.
best regards
pedro

Thanks Pedro.

Bye,

Peter

alo
more news.
let me see if i can put it in english.
been recording with api/melcor,some guitars and there is a funny thing about the sound.when you hit the guitar strings hard,the sound of the api kind of breaks(?).in other words,seems the same that happens with tube rectifires in guitar amps,i think they call it swag.well,in the api/melcor it happens and i like it very very much.
i made this listenings with a 441 mic,wich have low output,so i need to give more input at the api.
that is a funny effect.
best regards
pedro

Did it do the same thing with the pad on?

GREAT PEDRO!!

quick test with a api3124+,the sound of both units it is almost identical,with melcor sounding more forward in the high freq.3124 sounded more soft.i

Click to expand...

:shock:
Let us know more! I though Melcor was more sweet sounding that 2520...

:guinness: :guinness: :guinness:
Fabio