opa 627bp in MHZS cd33

CAT SIR,

can do me a favour? since u had change zener to 100V, your anode voltage of the tube should be about 100v now, can use measure the chatode & grid voltage when CD is not playing? is it ~45v??

if not mistaken when anode voltage is ~75v, the cathode voltage ~26-28v.


Dear KK sir,

from your experience for 2c51/6n3 tube what the best voltage different between anode & cathode? 50v?

Dear Cat,

Refer the attachedment, pin 2&8 is the cathode, pin 3&7 is the grid, 1&9 is the filament, pin 4&6 is the anode.

So you just put 1 probe on the ground and 1 probe on either pi which you which to test.

e.g: if you put 1 probe on the ground, another probe on the pin 6, u r measuring the one of your anode voltage, if you put the probe on pin 4 you are measure another anode voltage.

Hi T,

i did post some tetsing on the tube but not include rusia tube, anyway in mandarin.

Hi T,

Here's some brief info on the 6N3/2C51/5670 tube which i had try in my system. (Bada 6N3 CDP, audiolab 8000A (mod with BG cap & jensen big tank, AE AEGIS1 speaker (mod with vishay mkp &mkt + damping)

Tube tested:
1) Eclipse pioneer 2c51 (later known as bendix) - neutral, good detail & good bass - suit instrument lover. suit bookshelf speaker who need more bass. sound not as fast/crispy as tungsol.

2) Bendix 2c51 - characteristic similar as clipse pioneer but more dull/dark, slightly less musical & detail

3) Tungsol 2c51- very good detail & cripspy at HF & MID but bass is slightly less
4) WE 396A - more emphasis on mid (vocal), very musical, suit vocal lover but may not suit instrument lover like me

5) GE5670 - Soft, less detail, nice sweet vocal - suit vocal lover too but less detail than 396A

6) united electronic - dark, not musical...can't impress me so far...
5) GE 5670

Dear Cat & viewer,

T is right, just place the black pin on the ground, & red pin on the the place u need to make measurement.

No need remove vacum tube, your red pin from multimeter just touch at the 9pin socket's lead on the pcb.

Dear T,
then your CD33 circuit is a lot diferent from my BADA HD21. wehen my voltatge at zener =100v, my anode is the same =100v, grid & cothode will increase to ~45+.

ur cd33 is using 2 tube, is they use 1 tube for 1 channel?
my bada using only 1 tube (use for 2 channel)

when it zener =75v, gtid & cathode~28+v,

so the differential voltage is ~ 54-10.3 = 43.7v

my different voltage is ~47V

T, VIEWER,

U got any idea on the nipon chimi con oil cap in the picture (black)?
it is a film cap or electrolytic cap?

anyone kno0w the sound quality of this cap?

Dear cat,
ur measurement when cd not playing right?

since your zener use 100v thus your plate getting 96.7V is normal (i'm wonder how come T getting only 54v?, may be he refer to another tube?))

But the diffential voltage is ~33.7V for tube 1 which is quite low, maybe this is 1 of the reason your dB may read low. Try check your cathod resistor value, is it correct when u change it back as u had cahnge the whole board or compare the resitor value with the original and see....

your 2nd tube differntial is ~50V which is normally use.... when we compare T, n my cdp which using this 2c51/6N3 tube normally they use ~40-50v voltage differences.

So i suggest u check your cathod resistor value  (compare with original, n measure the value see it fall in the tolerance range not?)

or if your other friend got the same cd u do the measurement then compare n look at the cathode resistor wheter same value?

Cat,

Since i don't have the schematic of your CDP as i'm using bada not cd33 so i'm not sure your 2 tube is for 2 channel or for 2 stage( stage 1 & 2).

If 2 tube for 2 channel then the reading for both tube should be similar but if is is for 2 stage then it can be very different.

cathode resistor is the resistor connected to the cathode the give the voltage on the cathode (they use voltage drop theory). V=IR

For e.g,

if the the cathode resistor is 10R and create cathode voltage say 5V at plate voltage 70V. When u accidently replace with 100R then, it will created higher voltage drop, then ur cathode voltage will read >5V.

Since u said u had change a new board, in case they put in wrong resistor at teh cathode side then it will change the cathode voltage....

Cat,

Your testing shld be correct as you reading make sense, but viewer's measurement may be wrong for chathod & grid voltage (it look weird), his reading on plate & filamet shld be correct.

We are now measure the idle volatge, if u play the CD then the voltage will change (flatuate acording to audio signal if not mistaken)

dear Cat,

u had to put on the tube for testing..... it will make a lot differences....

ss

Dear Cat,

i agree with T, your CDP reading look ok....


the filament voltage 5.6V is ok but i had saw some article say that for 6N3/5670 tube the best result is when filament voltage ~ 5.9-6V (recomended by some audio guy).

Dear cat,

Below are some comment from the articles i read.

为了发挥6N3最靓丽的音色、减少交流噪音干扰，灯丝电压采用直流供电，并且不用6.3V，而是用5.9V-6V给5670（6N3）供电音质最好（这是一位胆迷通过实验得出的结论），

for that u need to check your PS to filament.

For e.g, refer the schematic, the diagram below is a supply to the filament, i can change the 6.6 zener diode to adjust the voltage supply to filament.

If your supply filament supply is AC normally they use resistor to control the voltag ethen u can change the resistor to obtain voltage u 1.

If your PS for filament is control by zener as in my diagram, then changing the zener will change the filament voltage.

So what u need to do is to check how's the suppy voltag eto the filament, if u can draw out a schematic of the circuit on this supply to the filament then it will be easier to mod.

Hi, T,

In case Cat, replace the 6V regulator, it is still the giving 5.6V, he could just use a 7v regulator with a 6V/6.2V zener diode right?

Dear Viewer,

Understand that u had recomve the filter at power supply. which part of the filter you remove? u remove the inductor and coupling cap for the AC?

Dear KK Sir,

Do you think the AC filter is good or bad for audio system?

Dear Viewer,

I had remove the AC filter in my Bada CDP, the sound is more analog & natural & smoother now but seems lack of some excitement less punch....

Dear Viewer,

I didn't take the picture as it is just a simple mod.
May be too use to some of the colouring, after remove the filter need some time to adapt. Generally i like to sound after mod especially when listen to vocal.

By the way i had also modify my Montor Audio old speaker with Mundoft Zn cap. I'm wondering why the Mundoft cap not popular use in HK? I myself feel that the mundoft Zn is much better than the Solen & ERO cap. The price also acceptable e.g a 3.3uF/250V is ~RM40/pc (~HKD75)

I use MA R100, product of 1989, metal tweeter but paper woofer.
i purchas eit 2nd hand the casing not so good so i had vanish it, i also use the silicon glue in side the casing to enhance the strength of the box and paint the black Tar at the inner wall. place 2 sand back in the box as well.
CAP REPLACE WITH MUNDOFT zn, RESISTOR WITH kIWAME.

Anyway, i found the original speaker hook up cable is quite good so didn't change it.

you just need t to browse through this forum u will get a lot info how people here mod the CD 33 but becareful...this is fragile unit for modification....good luck!