Hopefully this week, as soon as tomorrow for a 2 week time frame.
I will post it in the GB thing. Still working out some details with Salas regarding the kits.
Myself and TBJ (tea bag jr) are measuring transistors galore.
Hey Tea.
10ohm
Gain is 2x (499ohm)
EDIT : My DN2540 are at match at 1.010 (~101mA) with 10ohm source resistor (Some of the DN2540 samples was a little higher, but i found two perfectly matched)
Jesper
Last edited:
The resistor value can always be differentiated per M3 to have same current results between channels when not having matched DN2540s. As described in the guide. I have given guidelines to Tea on how to select two fixed resistor values that will keep in ballpark for low or high bias mode for his DN2540s batch. He will go the other way because of population. He will match M3 pairs from a tolerance bracket that will bring good following between channels and +/- 5% from nominal bias figures. So hopefully everybody will have nothing more to do than choose low or high bias provided resistors and go solder them along the two provided pre-selected M3s. Those 1W resistors will be low ppm top brand name also. I wish him patience because its a tedious task.
He now sent me averages from midrange VGS (OFF) DN2540s he was surveying during the weekend. He measured those M3s tend around the 100mA mark with 12R. But they mostly tend to 140mA with 8.2R. They would probably average tighter around 150mA with E48 7.87R but that value is unusual for stocked parts and certainly not readily available in what types we want so I recommended him to get E24 7.5R. That one will result to some high bias builds at 160mA+ but it will lessen the chances of below 150mA such builds. Which is not too bad because when someone chooses high bias normally prefers chances to end up higher than nominal vs lower. Both 12R and 7.5R are good for stocked DALE CPF series at Mouser.
Salas, for a line output build what is the preferred bias. Is higher a bit better subjectively?
nash
No. I run 100mA myself. Which is already very high bias for line duty lets not forget. For 60 Ohm or lower impedance headphones higher bias is better though. But you can try yourself to also compare for any use since there will be two sets of resistors at hand.
DCG3 R3 value
The now BF256B (J3) batch in Tea's hands is too strong for 4-5mA correct Id in circuit when R3=150R. Expect to find 220R R3 in his parts set.
Who have own J3s check they give 4-5mA with 150R using the following test circuit. If not any of them do, change your R3 value accordingly.
The now BF256B (J3) batch in Tea's hands is too strong for 4-5mA correct Id in circuit when R3=150R. Expect to find 220R R3 in his parts set.
Who have own J3s check they give 4-5mA with 150R using the following test circuit. If not any of them do, change your R3 value accordingly.
Attachments
Transformer / Torrid
So i am in for ordering the parts for finishing up my project.
I was thinking of using two of these Torrids for dual DCSTB : http://www.produktinfo.conrad.com/datenblaetter/500000-524999/518662-da-01-de-Ringkerntrafo_2x18V_50VA.pdf
I was thinking, that they are good German quality?
Soo about headphone output jack's... what is prefered here ? (XLR / Jack 3.5 / Jack 6.35)
Any good brands (Neutrik perhaps?) Anything elso to consider.
Jesper.
Btw: Salas i just recieved an SMS, that my PI Dac is ready for picking up at local postoffice today Pi-DAC+ I2S audiophile sound card for Raspberry Pi
So i am in for ordering the parts for finishing up my project.
I was thinking of using two of these Torrids for dual DCSTB : http://www.produktinfo.conrad.com/datenblaetter/500000-524999/518662-da-01-de-Ringkerntrafo_2x18V_50VA.pdf
I was thinking, that they are good German quality?
Soo about headphone output jack's... what is prefered here ? (XLR / Jack 3.5 / Jack 6.35)
Any good brands (Neutrik perhaps?) Anything elso to consider.
Jesper.
Btw: Salas i just recieved an SMS, that my PI Dac is ready for picking up at local postoffice today
Pi-DAC+ I2S audiophile sound card for Raspberry Pi
Prefer magnetically shielded transformers if you can get.
I had the professional locking Neutrik socket with the release button but I decided against installing it because it puts an additional step to pull out the cans which takes force to press and pull. It can move a medium weight box if you will not hold it down. Its really for live sound stage mix security where people can trip on or pull random cables and you don't want the drummer's headphone to go off line in the middle of his solo etc. Neutrik has nice non locking ones too.
I prefer 6.35 since all good cans come with an adapter that takes 3.5 on the back.
Nice with the Pi DAC, seems popular. Let us know if it sounded really better with that.
I had the professional locking Neutrik socket with the release button but I decided against installing it because it puts an additional step to pull out the cans which takes force to press and pull. It can move a medium weight box if you will not hold it down. Its really for live sound stage mix security where people can trip on or pull random cables and you don't want the drummer's headphone to go off line in the middle of his solo etc. Neutrik has nice non locking ones too.
I prefer 6.35 since all good cans come with an adapter that takes 3.5 on the back.
Nice with the Pi DAC, seems popular. Let us know if it sounded really better with that.
Yes i know... they are too expensive i think... I rather do some shielding on them myself instead (Some cans maybee)?
Let's see what i deside
I will try to set my amp up, here at the end of the week, and do some more listening. -There has only been a couple of hours on it yet as now.
Jesper.
Jesper,
those Sedlmaier toroids are inexpensive but have no shielding at all (like Salas said), and in a preamp you definitely want that.
Schuro is selling nice toroids with electrostatic and magnetic shield... they actually look very similar to the ones I have custom made at Rondo Müller.
https://www.hifituning24.de/transformatoren/ringkern_vergossen_v-rkt-ms-sw/65va-2x18v.php
They cost double, but its worth it. They should ship to your country as well.
those Sedlmaier toroids are inexpensive but have no shielding at all (like Salas said), and in a preamp you definitely want that.
Schuro is selling nice toroids with electrostatic and magnetic shield... they actually look very similar to the ones I have custom made at Rondo Müller.
https://www.hifituning24.de/transformatoren/ringkern_vergossen_v-rkt-ms-sw/65va-2x18v.php
They cost double, but its worth it. They should ship to your country as well.
What is 95 Zloty? Something like 22 Euro? I don't know about send costs though.
TTSA0050 - Transformer AUDIO TSA50VA - voltage to 50V - Shop Toroidy.pl
TTSA0050 - Transformer AUDIO TSA50VA - voltage to 50V - Shop Toroidy.pl
The hat is only cosmetic indeed. Can even be detrimental when ferromagnetic. It just takes a flux band in touch and around the windings to shield. They put that before the plastic film strips wrapping is done. The wires exits still offend and they better be oriented away from circuits and signal runs. Nothing is like an R-Core in the end but this is not a phono stage and a shielded toroid can achieve a decent enough reduction of its original 50Hz magnetic field. Also the split-bobbin frame ones are better than their conventional counterparts. But not greatly so.