[NelsonVandal]

Quote:

Originally Posted by Filburt /img/forum/go_quote.gif Nelson, where do you get your 2SA1016/2SC2362? bdent has some but some posts on diyaudio seem to indicate they only stock the "F" grade which has the lowest beta. bdent's site doesn't specify what grade they have other than it's the "K" type, where K seems to just specify a different Vcbo and Vceo.

I bought them from bdent.com. SA1016 Hfe 300 - 330 and SC2362 200 - 300. I've got some from a member at diyaudio.com that he had bought from profusion. The Hfe of those were slightly higher. Lowish Hfe or not, they sound much better than the other small signal transistors I've tried.

 

[majkel]

Which BC550's are you referring to? I have very nice memories with those from Fairchild. Not yet tried from NXP but their BC337/BC327's sounded worse.

 

[Filburt]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif I bought them from bdent.com. SA1016 Hfe 300 - 330 and SC2362 200 - 300. I've got some from a member at diyaudio.com that he had bought from profusion. The Hfe of those were slightly higher. Lowish Hfe or not, they sound much better than the other small signal transistors I've tried.

I was thinking of using them in my CKKIII build I'm doing. I picked up some 2SA968/2SC2238 for output; not sure if those will work well or not.

 

[Pars]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif I bought them from bdent.com. SA1016 Hfe 300 - 330 and SC2362 200 - 300. I've got some from a member at diyaudio.com that he had bought from profusion. The Hfe of those were slightly higher. Lowish Hfe or not, they sound much better than the other small signal transistors I've tried.

Anyone know what the 2SA1016K-AA is that bdent carries as well? Same price, not shown in datasheet. The -AA version of the 2SC2363K is cheaper.

 

[NelsonVandal]

Quote:

Originally Posted by majkel /img/forum/go_quote.gif Which BC550's are you referring to? I have very nice memories with those from Fairchild. Not yet tried from NXP but their BC337/BC327's sounded worse.

I've tried both Fairchild, NXP and noname. There's no major difference between them.

 

[Pars]

I found that the -AA version is tape and reel.

I've seen mention in this thread as well as on diyaudio of Profusion? WHo are they? Google didn't find a website. I take it they only do large orders (100 pieces or more)?

When changing out transistors (this in an I/V stage) are only the transistors in the signal path of interest, or should all of them (CCS, etc.) be changed? Design is rbroer's less simple, and so far I have only changed Q4 and Q6 in the attached schematic. I may just do the rest of them; they are currently 2SA970/2SC2240.

 

[looser101]

Quote:

Originally Posted by Pars /img/forum/go_quote.gif I found that the -AA version is tape and reel. I've seen mention in this thread as well as on diyaudio of Profusion? WHo are they? Google didn't find a website. I take it they only do large orders (100 pieces or more)?

Profusion

I assume that's what you are looking for.

 

[NelsonVandal]

Quote:

Originally Posted by Pars /img/forum/go_quote.gif I found that the -AA version is tape and reel. I've seen mention in this thread as well as on diyaudio of Profusion? WHo are they? Google didn't find a website. I take it they only do large orders (100 pieces or more)? When changing out transistors (this in an I/V stage) are only the transistors in the signal path of interest, or should all of them (CCS, etc.) be changed? Design is rbroer's less simple, and so far I have only changed Q4 and Q6 in the attached schematic. I may just do the rest of them; they are currently 2SA970/2SC2240.

I think Q4 and Q6 (and the SK389) are the most influential transistors in this circuit. If I understand the circuit right, it's a single end folded cascode topology, where Q4 is input and Q6 the cascode and SK389 is a buffer stage. Do you know at what currents the transistors run?

Does it sound good? Have you already rolled transistors?

 

[Pars]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif I think Q4 and Q6 (and the SK389) are the most influential transistors in this circuit. If I understand the circuit right, it's a single end folded cascode topology, where Q4 is input and Q6 the cascode and SK389 is a buffer stage. Do you know at what currents the transistors run? Does it sound good? Have you already rolled transistors?

I'm not using the buffer, though I do have 389BLs and 170BLs. I had already changed Q4 and Q6. I completed changing the other 3 BJTs and am listening to it right now. It sounds great (but it did with the sa970/SC2240s as well).

IIRC, Q3 has 9-10mA thru it (+/-15V PSU, TL431s drop 2.5V). About 10mA was the highest I could get the 970/2240s to be stable (stage has no feedback). From my reading, it would appear that the SA1016/SC2362s don't really iike higher currents either.

The hFe on these transistors is a bit low (my SC2362s were measuring 190s to just under 300; SA1016s were low 300s), and I got them from bdent so they are F grade.

 

[NelsonVandal]

Yes, the Sanyos don't like too much current. I feed mine not more than 1 - 2 mA. Didn't you notice any difference?

 

[Pars]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif Yes, the Sanyos don't like too much current. I feed mine not more than 1 - 2 mA. Didn't you notice any difference?

It seemed quite stable at the present currents, even without the servo installed. I did quite a bit more listening, but recollection being fickle, I can't say which sounds better. I was rather pleased with what I was hearing however. Typo in my previous response also (2SC2240 when I meant 2SC2362).

 

[xslavic]

hi,i know that this post is old but i wanted to ask where do you put the 10pf capacitor, between pin 6 and 2 =

 

[rds]

 
Quote:

 If you take "good" amplifier boards, there are often small ceramics close to the opamps, but the electrolytics are far away. I've seen some measurements of doing this (read it on Diyaudio, not measured myself), and the result is worse than using just electrolytics close to the opamps.

Not very convincing without seeing the measurements or the circuit measured.  Regardless, there's a reason why op-amps makers recommend "fast" ceramic caps close to the op-amp.  This picture tells the story if you understand how non-deal capacitors behave as a function of frequency:
 

 
PS that's from the opa627/637 datasheet
 
 
Edit: Just realized I replied to a comment from over 3 years ago :$

 

[xslavic]

why ceramic? isnt better using polypropylene or polyester capacitors ?

 

[holland]

Quote:

why ceramic? isnt better using polypropylene or polyester capacitors ?

for what?
 
decoupling?  no.
signal?  yes....and no.
 
for decoupling, it's hard to beat ceramic, low ESR, low ESL, and temperature stable.
for AD797 decompensation I would personally use mica, for temperature stability and stable capacitance over a high bandwidth instead of plastics.
 
as to where to put the cap, read the datasheet.