DIY Marantz 7C

Hi Cat,

When u purchase this M7 pcb, is it come with schematic diagram, part list and instruction to assemble it? Do u have softcopy of it, if yes can u email it to me? I will see whether i can DIY 1 with direct soldering...

i recently had DIY a tube preamp using 6N3 tube but result not so good need a lot fine tune and study.....

ss

Thanks for the link.

By the way what's the transformer specification you are using?
240V:300V? how many A?

Dear Cat,

Do u mind telling me how much u spend to purchase the M7C kit? is the price include the transformer?

Hi all,

Attached is the photo of the 6N3 tube preamp i recently made, since the diagram i have is not complete some of the rsistor value is not given, i'm still working to finetune it....

it's mid especially the vocal is vibrating, do you think it is because of wrong value use in low pass/high pass filter? At this moment i did not use any volume pot.

i had change the various value of the cathodr resistor but it only affect the volume not the quality of the sound.....

the vibration most serious at vocal rangr, and a bit on high frequency, low frequency is ok....

ss

this the schematic i use and measurement done as in the picture... hope some expert here can advise me why the sound at vocal range is vibrating....
thank you...

Dear Vash,

Thanks for guidance all the time.... i will shift to your proven 6N3 if i still not able to figure out the problem...

Dear Cat,

I got no choice in Malaysia not easy to find part or at premium price....so has to make use of all sort of available resources....

I wish to do scafffolding too but can't get the not sure where the get the coper rod....

Accphoto,

Need your advice.

Recently i DIY a 5687 tube pre amp, when use on DVD player as a source, no hum/very little hum but when use Bada tube CDP as source will have high hum.

the hum sound is ngggg at woofer only. then i disconnect my grounding in my tube CDP, hum sound become worst, got eee sound from the tweeter as well (much more distortion).

i didn't ground my supply to the filament.

Besides, what shall i adjust if i replace the 12AX7 in M7 to 12AU7?

TQ

Dear Accphoto,

Since the preamp i make is in a wood box, so no grounding to the box. all grounding connecr to the main ground on the 3 pin plug.

for my CDP, the ground of the pcb is connected to a capcitor then to the chasis (to reduce rf) so the chassis is actually not grounded.

Dear all,

My tube preamp is using 5687 tube (circuit close to audionote M7 but i run B+ at 130V only).
The noise reduce a lot after i do the following changes:

1) change to metal casing
2) restructure the grounding (use star grounding)
3) add in another C-R-C (total 4 CRC in series)
4) Reduce plate resistor ( increase the voltage supply)

Thank you everybody here for advice.

no source of cheap choke in malaysia at this moment..

i'm think instead of choke can i just use the inductor 10mH?

maybe use 1 C-RC follow by 1 CLC....

Hi, Accphoto,

Can i have your email so that easier for me to contact you. Thne i can make arrangement with you to buy the choke....

thank you.

Hi,
attached is the 5687 tube pream/buffer i made.

Using the attached schematic but some changes
1) use only 4.7k plate resistor
2) B+ = 175v
3) chatode resistor =470R
4) SOLID STATE half wave rectifier
5) 1uF cap
6) C-R-C filter

next will make another 1 using
1) ~250v B+
2) 10K plate resitor
3) choke
4) 0.47uF mundorf ZN
5) separe box for power supply
hopefully sound will be much better

云外天,

The tube preamp i made is same as your post 5687单管胆前级 in your web but i change the 1M to 470k.

plate resistor audionote using 50k, vt4 using 10k.

do u know what is the effect of th eplate resistor and the cathode resistor?
i understand that by using higher plate resistor can get better dynamic, how about cathode resistor and cathode capacitance? how's the value will affect the sound?


Do u think a DIY marantz M7 is much better than this 5687?

No problem, i like to read mandarine/chinese. Sorry for inconvenient as i do not has software to key in chinese word.

By the way may i know your your voltage measurement on the position below during idle:

1) voltage before the 50K resistor
2) voltage after the 50k resistor (on the plate)
3) wht's teh value of capacitor (uf) at the chatode
4) voltage at chatode

Dear all,

Please be fair to the youngster today.

Compare to olden days, nowadays the attractment is much more, there more alternative as well (people tends to distract when have too many choice), become trend had changed, good in academy doesn't promise the good future...and they are other alternative....a lot rich man do not have university level of education...

Nowadays, whatever you want you can buy it easily with money, indirectly we seldom squeeze our brain to invent/devlepoment thing using knowledge learn from school. As those who do not obtain high education tend to take up higher risk & challenge.

Today's engineer do not need to trouble shooting to component level--> it is more on software, machine will give error code, anything goes wrong just replace the whole pieces of board...

Life for the future generation become tougher, they need to have good knowledge and also brave enough to explore to own business.....

A lot of people like to emphasis on IQ & EQ, in fact youngster today generally has higher IQ & maybe also EQ than old generation. But their ability to face set back & falure is much pooprer. Olden day we will not suitcide when fail the exam......so who adding the pressure on this poor youngster??
a lot people tend to think that higher education level = higher knowledge.... but is it true?