2nd Gen Build Started (that didn’t take long…)

[Dr d]

Great results, well done. Having just build a 2nd gen amp, it was interesting to follow your experiences. If I could make a comment on voltages, you may find this helpful. I found that the V1 and V2 plate voltages were particularly sensitive to the performance of the amp. With Hammond iron also, I found 2k2 > 27K > 2k2 (Tonys dropping string values) gave me 175-180v V1 and about 185 - 190v on V2. These voltages really opened up the amp and made it sing. Ge 12AX7As and balanced GE 12at7 sound really nice and yes, the EVM 12L is perfect for this amp. I am really impressed with the Hammond iron and the amp improves significantly as it burns in. Lovely amp. I hope this helps. Enjoy.
Ps. I much prefer the 3rd gen setting!

Thanks for the info Doc!

I’m still thinking of increasing the 3k3 I replaced the first dropping resistor with just because the line voltage seems to vary up to 8vAC. My V1 is sometimes 185, sometimes 192; and V2 can vary from 193 to 201. I’m leaning toward that resistor vs the B+5 because the voltage swing on the plates doesn’t really affect the tone - but the “feel” between 445vdc and 455 vdc is noticeable in the amp’s response. Very subtle, but certainly there.

I’m also starting to prefer the “bass knob pulled/3rd gen” sound as well.

IMHO I would still revert back to the original values. The 2k2 will keep the PI voltages at a good level (ie around the 290V mark) and then by increasing the 22k to 27K, that will stabilise the V1 and V2 plate voltages to the level I have suggested. I must give credit to Talbany for these suggestions. They definitely worked for me....and we share the same iron!
Cool that you like the 3rd gen setting!

[Raoul Duke]

Alright, final configuration of this build is as follows:

- The main dropping resistor on the power supply board is and will remain a 3k6. The 4 and 5 nodes retain the original values. This got my V1 values down to where they needed to be and the resulting V2 drop helped me balance the two channels better. Beautiful cleans and nice crunchy OD without volume disparity. Granted, the volume runs around 2 o’clock and the OD runs about 10 o’clock - but they both sound great with no perceived volume difference. I control the overall volume with the level pot and everything sounds good!

- The bias supply resistor is and will remain a 2k2 - which allows me to bias both Tung Sol and JJ 6L6GC closer to the center of the bias pot travel. The TSs seem to feel and sound tighter. The JJs perform well also and either are perfectly acceptable. Power tube choice flexibility is nice.

- final tube compliment is Tung Sol 6L6GC-STR power tubes, V1 is ANOS 60’s GE 5751, V2 is ANOS National/Tungsram 12 AX7, and V3 is ANOS JAN/Philips 12AT7.

Really happy with how this build turned out. Taking the time to run through the different options to get it sounding “just so” was a bit of a challenge at times - but well worth the time and effort.

Thanks again to all who helped; very much appreciated!