Simplistic NJFET RIAA

I got a chance to sit and listen over the last couple of days and here's the report.

First a build summery. 2 BIB regulators, parts and boards from tea bag. Nichicon kg10,000uf smoothing caps and 10r current setting resistors. 2 strands of cat 5 wire per connection about 5" long run to the riaa board. I noticed no difference from wires twice this length. Antek 50 va transformer.

The riaa circuit is 43db gain. My cart output is 2.5mv. prp resistors except for the 47k leading from the first stage to the riaa filter. this is a z foil. russian ft3 teflon for 100nf and 47 nf and pio k42 for 15 nf. The output cap is pio k75-10 2.2 uf bypassed with 100 nf ft3. nichicon muse for the electrolytics.
russian caps from Tubes-Store.com - Vacuum tubes, capacitors, nixie, sockets. Wholesale & retail trade. Worldwide shipping.
chassis from Amp Chassis
jfets from FET Audio | Hi-End Audio Projects
prp from Sonic Craft High-End DIY Audio Parts

Now the sound. The stereo image is excellent. I had enough caps to get good matches. The sense of space puts my cd player to shame. The bass carries a lot more weight then my previous build. Detail is also excellent. The buzz of a guitar string, or the wind in a voice. The unit is totally silent, no hum or rushing sound with the volume all the way up and no music playing. The biggest thing I notice is what I'll call snap...the snare drum or sounds soooo good.
As it stands my system is the best it has ever been. This is thanks to the excellent info and help I have found here. I'll drink a beer to you and say thanks...
Evan
 
hFE on BC550C on eBay (yes I know this is is a chance to take)

I have bought some BC550C on eBay and I used the schematic under for the the NPN, and calculated the hFE to match in pairs. the measurements varied between 246 and 314, and there was many good pairs .

Then I took one of the BC550C from the "BIB set for the Salas 1.1" and this one measured 474, so are the ones I bought good enough, and should I buy a load from the quality vendors? The ones I bought have a silver front, with black marking " C550C PH 99 ", are these good enough and not fake of some sort? :confused:

With kind regards

Martin

transistor_matching_bjt_hfe.jpg
 
A thousand and one questions and ideas

I can always use these Philips BC550C then, but is it worth it to one time later change them in to Fairchild? I have seen one distributor that has them, and they are slightly more expensive than On Semi's that I have also found. Well if I am going to do it good why not take it all the way? :D


And I will use this riaa with a Denon DL-160 on a Rega Planar 3 together with a Shure V15III and SME series III tonearm on a heavily modified Lenco L75 that I am still working on.


PS! I am still wondering about the 1M resistor in the Riaa, and what to put in, and what works best together? The metal vs. carbon and low ppm. I have all the resistors in Shinkoh and in matched pairs except the 1M one and the 1.2K and the 47K is not matched and these are in 1W. I have alot of the values and in matched pairs in PRP and Takman REX and REY + Amtrans AMRG 1M and the Vishay Z-foil in 6.8K and in 47K.

The pictured capacitors are the ones I had in mind for the riaa, and they are russian silver mica crM3-5 combined and matched in 0.3% accuracy in 47nF and 15.330nF, it took some time to do I can tell you so I hope it will be worth it.

One of the countlees smart ideas I found here was the post: 7067 and the eylets that made it easier to change resistors. I will try to imitate this by using some copper sleeves made for crimping on wire ends (good quality ones). I am thinking of using these "tubes" through the board permanetly so I think they have to be of copper and not brass does anyone have any thoughts on this? :confused:


My main loudspeakers I use together with a chinese tube amp ( Music Angel KT 88) are currently under a rebuild I found here: http://www.troelsgravesen.dk/Dali800.htm so I have to use a headset evaluating the progress with the riaa.

PS! the crossover in the speaker modification will bee slightly modified in regards to capacitors (some russian teflon and obbligato premium) the coils are the same as in Mr. Gravesens modification.
 

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diyAudio Chief Moderator
Joined 2002
Paid Member
Headphones are a trusty evaluation tool. But they have to be the neutral kind to judge well. Use AMTRANS 1M. If you want good hfe, lowest base spread resistance and noise, higher Early voltage, although not critical in the common base BJT part of the cascode (BC550's role) locate a Japanese exotic.Like Hitachi 2SC2545,6,7 E or F.
 
Amtrams it is then

I will use the Amtrans 1M thanks for the input. I will try to get the Hitachi 2SC2545,6,7 E or F, but I am thinking that this is most noticable in a Low MC version or am I totally wrong?

I will be building one of the Low MC versions to I expect, so it will be very interesting to hear the difference between the standard BC550C and the Hitachi 2SC2545,6,7 E or F. :cool:

With kind regards

Martin
 
diyAudio Chief Moderator
Joined 2002
Paid Member
You will let us know if you can pick up any difference, as I said its not that critical there, regardless the version. I just let you know what is highest spec since you put an expensive build effort and you ask about BJTs anyway. If you can't locate any of those special transistors, 2SC2240BL Toshiba is easier to get, still ~1/3 Rbb' than BC550. The Japanese ones got their pins different, remember to check out if exchanging types.
 
The 2SC1815 has better Vcesat parameters. What I'm looking at is the Ic vs Vce curves. For the C2240 the curves straighten out before .5V Vce, this is very good. For the C2545, they straighten only after about 4V; I wouldn't use it in a current mirror. These don't have much to do with the Early voltage at above 4V Vce, which will determine PSRR as long as you don't go too low. It is not necessarily possible to tell which will have less leakage above these voltages from the datasheets. Whichever has the least slanted lines...
 
BC550C Alternative.

Is it so then that the Toshiba 2SC2240BL alternative that you give here Salas is the better one and even better than the 2SC1815BL if I get all this the correct way?

And do you all think the difference against the BC550C will be noticeable in the high gain MC version 56/60 db, and maybe even with the 43db I am starting with now?


I can at least say that the Hitachi 2SC2545,6,7 E or F is not so easy to find so these alternatives makes it easier.


“vgeorge” has this quote in his posts that I really do believe in: “ "Without deviations from the norm, progress is not possible" - Frank Zappa”

PS! Vgeorge I will not steal this, it is a one time incident



With kind regards


Martin
 
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