valve/miniature can hiss

[ktigerb]

Hi fellow afflicted

I have just finished installing a CJ Prem 6 clone (6CW4 version) in a smaller case (minus the rubber suspension) but have an annoying hiss in the background. Not really noticeable when playing music but irritating between cuts and changing LPs' Everything else sounds fine eg. detail ,soundstage bass etc etc.
(at least a whole lot better than the existing MC stage in my amp.)
Is there anyway to get rid of this hiss(similar to the background noise found on some live recordings)

regards
keith

 

[dhaen]

Hi Keith,

Do you have a link to a schematic?

Cheers,

BTW, I think this might get more response in the tubes forum, shall we move it?

 

[analog_sa]

Hi Keith


All valve circuits with anything but battery power seem noisy below 500uV. What cart are you using? The PS seems a bit basic for real low-noise applications - especially in a circuit with near zero PSRR. I'd be very tempted to give it a listen with the cathode follower removed - it won't improve the hiss but i bet will sound significantly better.

cheers
peter

 

[ktigerb]

Hi Peter and dhaen

Peter the cart is a Micro Seiki MC with 0.082 mV out/2.2 ohms(very low)

dhaen I have the cct in pdf can be downloaded from CJ website ,I see attachment does not allow pdf format and yes maybe moving to the appropriate forum may help. thanks

 

[analog_sa]

With 82uV you can't reasonably expect good S/N from this circuit. If hiss is really important to you (it's not that important to me) you need either a transformer or parallel valves (FETs/Bipolars) and really low-noise power. With a 100uV cart i've had (almost)reasonably acceptable hiss using ECC88 with 36v of NiCd power; very low hiss by using LM394 (but very little music too) and a good music/hiss ratio with a parallel 2SK170 fed by 16v NiMH. I prefer any of the above solutions (minus the LM) to a selection of high quality step-up transformers.

cheers
peter

 

[fdegrove]

Hi,

I have just finished installing a CJ Prem 6 clone (6CW4 version) in a smaller case (minus the rubber suspension) but have an annoying hiss in the background.

When it comes to valved headamps I'm all ears...
It the hardest task you can ever undertake using our old friends.

Nuvistors being hard to come by nowadays a low noise 6DJ8 know as the E188CC or 7308 helps.

Here's a dead quiet example that takes in your cartridge with no pain:

Use very well matched BF244As low noise please, ditto for the valves and find an excellent cap for the MPSA capacitance multiplier.

Take care of layout and any other detail that could possibly influence soundquality and you have yourself a little gem.

Cheers,

 

[ktigerb]

Hi Frank

Thanks I already have this circuit on file "TO DO" from a previous thread + the phono stage .
I got this CJ clone already made in a nice case al la CJ style just after I got a CJ Prem3 pre-amp which I was about to buy until I opened it up to find some one had undertaken some "DIY" mods that were busy coming apart , a real messy nightmare to restore to original but thankfully the seller had someone else who was interested , repair cost no problem so I thankfully let it go but I kept this part for the case more than anything.
The supply Txs' were loose (not boxed)connected with long leads via a plug and socket arrangment (very crappy arrangment)
So I stripped the cct board out of that case and built it into 2 seperate boxes with 1 for psu and 1 for the MC cct board.
Now I know why the original was suspended on rubber belts so it will need to be rebuilt again using a form of suspension , but in a different case to accomodate .

Aside of the gripes it has been real fun , just to be reminded why I never liked valves to start with , the B............. noise .

Regarding your circuit I was wandering would it work using 4 6CW4 's

regards
keith

 

[fdegrove]

Hi,

Regarding your circuit I was wandering would it work using 4 6CW4 's

That should work.

You may even try to put just a pair of 6CW4s in // and use a BF245A J-FET as a CCS.

As usual, try to select the nuvistors and the CCSs for low noise.

The CCSs should also have the same IDSS between channels.

Improving the quality of the cap used in the capicitance multiplier may be worthwhile as well.

At the low currents involved you can even try a battery supply too for the B+.

Happy building,

 

[ktigerb]

Thanks Frank
I meant 2 per channel in // .
Will see what 2 spare sets cost rom CJ or MF , have some beautiful Collins filament TX's in little square grey ally cans of which there should be 4 ( I snitched them +30 yrs ago to use as supply for a colour enlarger e.g 12V@10A) but only one has surfaced so far

regards
keith

 

[fdegrove]

Hi,

Quite likely you'd find cheaper sources than CJ and MF for the nuvistors.

Here's one good source :

AES

Cheers,