Kevin,

Apart the input device That 340 , do we need match the transistors?

If use jets input like 2sk170 and j74, are there any change to the resistor values of the input stage circuitry?

Thanks

 

You might try reading the thread before asking questions...

On 1/11/2022 at 5:09 PM, Pars said:

Would there be any problems with using BC556B parts with BC546C? Both On-Semi? I'd be buying 100 of each. Vendor doesn't have the 546B parts in stock (on-semi).

 

 

If this question is still relevant, try TME, they have the OnSemi 546B on stock

On 2/7/2022 at 2:05 PM, kevin gilmore said:

so split versions of the cfa3 board.

stack the boards together and put on the heatsink (minimum heatsink vertical dimension 83mm)

stack the boards together, use angle bracket mount horizontally for low profile chassis

etc

 

cfp3smt2splitamp - CADCAM.ZIP 61.71 kB · 24 downloads cfp3smt2splitpre - CADCAM.ZIP 77.07 kB · 26 downloads

Do I assume it correctly, that the pre board is intended to be flipped along the Vcc axis in order to have the 3way posts aligned on the same side with the shortest possible connections?

that is one of the ways of building it.

On 3/26/2021 at 3:04 AM, Kerry said:

Work in progress...

I should be able to test soon 🤞

Did this make through the testing? I love doing smt just to spite people!

I've been pulled away from this to launch our Aeras e-stat amp, but will be getting back on this after the launch.  

SMD is not done to spite people   I'm trying to meet get specific size requirements and it seems to be the way the world is going.

6 minutes ago, Kerry said:

I've been pulled away from this to launch our Aeras e-stat amp, but will be getting back on this after the launch.  

Hey Kerry, what is the Aeras e-stat amp?

I'm launching a new company and this is our first product.

Here's the announcement:

 

Look what the cat just dragged in 🙂

Prior I start desoldering any components from my other boards, I thought I'll ask if anyone might need two fully populated (except Opamps and JFETs) wider boards. Not trying to make any profit, will sell at BOM cost, DM me if interested. 

Those have never been powered up, build to specs, MJF devices tightened to 0.8Nm using stainless steel hardware, 105°C Panasonic FR electrolytics and WIMA/Kemet/Murata caps used as well as Bourns 3296W trimpots and Mill-Max IC sockets. All BC556B/BC546B onsemi devices were selected from 100 and are matched to Idsss.

If not sold, are you going to transfer most components to split boards?

Out of curiosity, are split boards so much better than wider boards to justify hard work of desoldering and soldering a lot of parts?

1 hour ago, Helium said:

If not sold, are you going to transfer most components to split boards?

Out of curiosity, are split boards so much better than wider boards to justify hard work of desoldering and soldering a lot of parts?

To be honest the only reason for me moving to split boards is pure cosmetics, because I can fit them better in my case which is taller but same 32cm width as my external dual GRLV PSU.
If I was going to use a standard 43cm case I would not switch, no reason to.

Originally I planned to use the wider boards in the same case with the left board on top and upside down and right board on bottom, leaving space in the middle for the rod coming from the back where the input selector board would be holding the pot as well. But this is not as nice as using the split boards.

I would not move everything, probably only the MJF devices, the Bourns trimpots, some caps and maybe the 1R CMF resistors. 

@kevin gilmore would there be any benefit in using low inductance resistors like Caddock or Fukushima MPC74 for the 1 ohm resistors?

the inductance is going to be really low in any case.

Has anyone any adapter boards left or gerbers for using 2SJ109/2SK389 in the 14-pin JFET socket? I am sure I was looking somewhere at these, unfortunately can't find anymore. 

there are gerbers for the k489/j689 and the 2sc3381/2sa1349

pretty sure the  2sj109/2sk389 is compatable with the 2sc3381/2sa1349 board

you are looking for that340.zip

 

 

Kevin,

The pinout of the bipolars is not compatible with the 2sj109/2sk389. I did boards for those and can supply the gerbers. They should also be in one of the dynalo, etc. group buys that Steve ran (sbeylo) some time ago.

Thanks, Kevin, found it. The pinout for the 2SA1349/2SC3381 do not line up with 2SJ109/2SK389 though, despite being the same package. Will make a new one and post it. 

5 minutes ago, Pars said:

The pinout of the bipolars is not compatible with the 2sj109/2sk389. I did boards for those and can supply the gerbers. They should also be in one of the dynalo, etc. group buys that Steve ran (sbeylo) some time ago.

Great, Pars. Could you please post here. Thanks mucho!

 

Edited March 17, 20224 yr by audiostar

Here they are.

THAT340-J109-K389-JFET.zip

On 3/17/2022 at 2:09 AM, Pars said:

Here they are.

Thanks, Pars! 

Which pins are you using on the lower side, that go into the 14-pin socket, do you have the p/n handy? Thx

I actually got them from ebay. I think Kevin had posted a link in one of the threads, probably the Dynalo thread. Ebay isn't showing me who or what these are (only goes back to 2020 purchases). I'll keep looking.

EDIT: it was something like these: https://www.ebay.com/itm/254636284745?hash=item3b49815b49:g:CGIAAOSw8s1gnfky

Edited March 29, 20224 yr by Pars

49 minutes ago, audiostar said:

Thanks, Pars! 

Which pins are you using on the lower side, that go into the 14-pin socket, do you have the p/n handy? Thx

the pin header  I use is 127-1-4010-8002-310 made by Nextron.

Or you can search "Nextron 2.54mm round pin" on Ebay

Thanks, guys! I am looking for something that is not too long and does not stick out too much of the IC socket. Also most of the pins I got are square.

Edited March 29, 20224 yr by audiostar

On 11/29/2017 at 7:50 PM, kevin gilmore said:

Newest version of the current feedback amplifier with the servo not in the audio circuit so that you can use cheaper opamps. But if you run 30v, you still need 30v capable opamp. Like opa551.  what the noise difference if any, I don't know yet.

I was checking old messages in the thread and found this. 

As I am running 30V dual GRLVs (with the new split boards), do I need to change from standard OPA445 to OPA551? Looks like... still not powered on for the first time. 

Looking through the specs, the OPA445 goes indeed up to 45V, confused.

Edited April 3, 20224 yr by audiostar