SET amp owners thread

[DasguteOhr]

I believe the Lamm ML2 is one of the best sounding SET amps ever made. I chose not to get a pair after struggling with the 63CC in my Lamm ML1.1 push pull. Lamm said that he’d have to throw away 75% of them to get tubes to his SPEC.

I never doubted that it would sound good, but it does so even if you don't push the tubes to their limits.
Just try it out, take a screwdriver and a multimeter and set it to 260mA (0.26 volts). If you don't like it, you can change it at any time.
I consider the value for a 6c33 tube to be optimal (45 watts at the anode)not at the limit
P.S
If you put the tubes in the oven for 5 hours at 120 degrees (no fan-assisted heating) and then let them cool down in the oven overnight, you'll only throw away 40% at most.

 

[morricab]

I have tried dozens of amplifiers, solid state and tube, with my Quad 2905’s. Nothing is as sublime sounding as my JJ 322 parallel SET. It uses two pairs of 300B’s per channel to produce about 20 watts, which feels ample for my listening tastes. It’s a behemoth weighing almost 100 pounds. The literature on it describes the output transformers as “C-cores”.

JJ Electronic - JJ322

JJ Electronic - Vacuum tubes, Capacitors, Amplifiers

www.jj-electronic.com

View attachment 154952

I had this amp for years and it is quite good except for the highs being too “soft “ for lack of a better word. It would not drive well “normal” speakers but on my horns it was quite nice.

 

[morricab]

As I understand it, the ML2 transformer is the same size and specification, just a different manufacturer.

I thought one review said later versions were heavier?

 

[Kingrex]

I replaced a few components that were no longer working properly, and a few cables because they were humming a bit. You can clean the sockets with interdental brushes and isopranol alcohol.

What size interdental brushes for driver type tubes?

Any way to remove the residue. I find when I clean, solvents lift contaminants, but you need something like cotton to wipe off the mess and remove it. If you don't remove it, it will settle back to where it was. On you metal.

 

[DasguteOhr]

What size interdental brushes for driver type tubes?

Any way to remove the residue. I find when I clean, solvents lift contaminants, but you need something like cotton to wipe off the mess and remove it. If you don't remove it, it will settle back to where it was. On you metal.

Buy a set of different sizes so you'll always have the right size. Alcohol cleans well if any dirt remains, and Q-tips for your ears help wipe it away. Never seal tube contacts with anything; it will attract more dust and dirt.

 

[jeff1225]

I never doubted that it would sound good, but it does so even if you don't push the tubes to their limits.
Just try it out, take a screwdriver and a multimeter and set it to 260mA (0.26 volts). If you don't like it, you can change it at any time.
I consider the value for a 6c33 tube to be optimal (45 watts at the anode)not at the limit
P.S
If you put the tubes in the oven for 5 hours at 120 degrees (no fan-assisted heating) and then let them cool down in the oven overnight, you'll only throw away 40% at most.View attachment 154959

I've heard that if you sprinkle them with cinnamon you get a wider soundstage.

 

[microstrip]

I believe the Lamm ML2 is one of the best sounding SET amps ever made. I chose not to get a pair after struggling with the 63CC in my Lamm ML1.1 push pull. Lamm said that he’d have to throw away 75% of them to get tubes to his SPEC.

By that time (around 1998) the 6c33's were so cheap that this was not a concern ... I remember buying them from Ukraine at around $20 each in 12x boxes and matching them for the Graaf OTL's.

Manufacturers who select and burn-in tubes typically claim rejection rates around 50%.

 

[DasguteOhr]

I've heard that if you sprinkle them with cinnamon you get a wider soundstage.

If I were you, I would pour wine into the bowl so you don't have to drink while listening to music.

 

[jeff1225]

If I were you, I would pour wine into the bowl so you don't have to drink while listening to music.

I drink all of my wine through a straw. The bowl works perfectly.

 

[godofwealth]

I had this amp for years and it is quite good except for the highs being too “soft “ for lack of a better word. It would not drive well “normal” speakers but on my horns it was quite nice.

I suspect that’s why it makes a good match with my Quad 2905s, which can sound a bit harsh with typical solid state amplifiers.

 

[Atmasphere]

IMO it should have been called a distortion generator, not an amplifier. I can't understand how a core starts saturating at 1kHz at 1W!

The BAT VK60 used a toroidal output transformer. Toroids are very good at getting the inductance needed for deep bass (can be good to just a few Hz) and are very good at highs too (easily going past 100KHz at high power)! But their weakness is any DC in the core will easily cause saturation.

'DC on the AC line' is a common problem that is a direct result of this quality. In a power transformer the DC on the line can cause the transformer to rattle (vibrate). It is for this reason we use 'DC Blockers' in our amps (as many other manufacturers do) to prevent the toroidal power transformer being noisy.

In the case of an output transformer the easily saturated part will make distortion quite quickly. The only solution is dynamically matched output tubes so that at any power level there's no DC difference between the two tubes. In practice this is very difficult since you have to use a curve tracer (Techtronix made a good one) for the tubes. I very much doubt most users were doing that; the measurement suggests that BAT was not doing that either. If one of the tubes were to die you'd likely have to replace the pair.

 

[microstrip]

The BAT VK60 used a toroidal output transformer. Toroids are very good at getting the inductance needed for deep bass (can be good to just a few Hz) and are very good at highs too (easily going past 100KHz at high power)! But their weakness is any DC in the core will easily cause saturation.

Now that you refer to it, I remember that the Nagra VPA (push pull toroidal transformer, 845 tubes) had a similar distortion versus frequency curve.

'DC on the AC line' is a common problem that is a direct result of this quality. In a power transformer the DC on the line can cause the transformer to rattle (vibrate). It is for this reason we use 'DC Blockers' in our amps (as many other manufacturers do) to prevent the toroidal power transformer being noisy.

Yes, vibration due to DC can be a nightmare in transformers, particularly when we are using equipment made in a 60 Hz country in 50 Hz lands, as most manufacturers do not test them in such conditions.

Do you use the high value capacitor / diode bridge type of blocker?

In the case of an output transformer the easily saturated part will make distortion quite quickly. The only solution is dynamically matched output tubes so that at any power level there's no DC difference between the two tubes. In practice this is very difficult since you have to use a curve tracer (Techtronix made a good one) for the tubes. I very much doubt most users were doing that; the measurement suggests that BAT was not doing that either. If one of the tubes were to die you'd likely have to replace the pair.

 

[Atmasphere]

Yes, vibration due to DC can be a nightmare in transformers, particularly when we are using equipment made in a 60 Hz country in 50 Hz lands, as most manufacturers do not test them in such conditions.

Do you use the high value capacitor / diode bridge type of blocker?

We spec all our transformers for 50Hz operation. And yes, we use a DC blocker of that style.