jose

Sorry Steve but I´m not sure. 1 set is 8 pieces? If it´s ok. I would like change my order If it´s not a problem, I would like only 2 set´s and add one unbal/bal tube.

I´m using the un/bal boards like preamp with my CFA balanced. Input/selector -> 10k pot -> un/bal -> CFA It work perfectly so I´m very happy. Now I can start my preamp chassis. With the buffers I need to think what can I do because I don't feel comfortable using it with Offset. Obviously the easiest thing would be to add capacitors in the output, but clearly that is not the goal. I will try to make several set of macheted transistors to see if I can get one that is below the 8mVolt that I currently have.

CFA2 only has 10K input impedance so if I want to use buffers I´d have to add a 40k resistor on the buffer output.

Joe Hisaishi meets Kitano films... small delight

Brad Mehldau trio "ODE"

It's good to know that it sounds. As for the peaks, I don´t like to turn on the amplifier with the headphones connected to it. I prefer turn on and wait a few seconds... but I also know people who don´t like to connect the headphones with the amplifier turned on by the short that the connector produces

Good observation

There is virtually no difference between using the OPA or not (I understand that I should not either, right? Opa here is not working as a servo). The four buffer have more or less the same offset (8mvolt) All fets are matching around 530 ~ 540hfe and 540 ~ 550hfe (P to P and N to N) Is a closer match necessary? If so, which would be the most critical?

Have you tried to change the THAT340 for other?

Yes, only like a test, decreased Bias for example until 600mVolt and check the offset.

Do I need use any resistance on the Buffer output?

Have you tried to download the BIAS?

If you have 3.3volt, something is wrong.

Yesterday I tested my pcb's and they seem to work correctly. Offset on un/bal output is 0mVolt (with servo). With buffer I measure an offset of 8mVolt on the output in each one. It's right? I'm using OP27.

EH 6CA7 and Tung sol EL34 maybe?

Happy Birthday

Change of pads and rotor.

Thanks Michael!!! I have inventory of bought devices but I prefer the KSA1156 too. It's more easily to fixed. I'm waiting for trafos Edit. I saw you answer

Disastrous management

million per year, it's a lot of money for a small business...

José James

Before touching anything, I would first change the resistance of 500 Ohm. About offset, In my case the Offset was influenced by the BIAS too high and by the THAT340.

Yes, you can change r500 (next to Trimpot) for other from 620 Ohm to 1K.

Thanks Birgir but both are very difficult to find too. I´m working on my Megatron and checking the threadt I found references to STN9630 and KSA1156 but I would like to be secure.

To replace the 2SA1968, which is the best option? The STN9360 or the KSA1156? *STN9630 is SMD (I have boards for adapt this to TO220). *KSA1156 The Pins are the opposite, you just have to rotate it.