Your journey with lower-watt tube amps -- Can a kit be good enough?

Hi @atmasphere ,

In parallel to the McIntosh MC30 I had Marantz 8b.

I used these amplifiers with Spendor 2/3 and Altec 604E with original n1500 crossovers.

This Marantz was burned by one of the previous owners.

So output transformers were fixed, and power transformer and choke was replaced by a local transformer store built. On another hand, I and one of my technician friends replaced resistors to RikenOhm, capacitors to Black Gate and signal capacitors to Audio Note tin and copper foil. The technician adjusted the feedback of the Marantz. So this Marantz 8B had pluses and minus versus the original Marantz 8B. I also used the original Mullard EL34 on this Marantz.

Yes this Marantz 8B sounded more clear then McIntosh MC30. But despite Marantz bass wasn’t bad, MC30 bass was on the other league. It was also a big difference in complex music reproduction. 8B was good on very simple music but the sound became muddy and congested with bigger number of instruments and voices. On the other hand, the complex music wasn’t an issue for MC30. The Plinius 8200 Mk1 integrated that I had then also had a problem with playing complex music, but it did it a little bit better than Marantz.

Yes this Marantz 8B sounded more clear then McIntosh MC30. But despite Marantz bass wasn’t bad, MC30 bass was on the other league. It was also a big difference in complex music reproduction. 8B was good on very simple music but the sound became muddy and congested with bigger number of instruments and voices. On the other hand, the complex music wasn’t an issue for MC30.

@alexberger Sounds to me as if the modifications didn't have the desired effect. Feedback is a bit more complicated than it might look on a schematic. The Marantz 8B has a more sophisticated feedback design than most amps you see from that era; IMO/IME its unlikely that a technician 'adjusting' it would be successful in getting the amp to actually perform better.

@hilde45 Thanks!

Hi @atmasphere ,

 Power supplies of all vintage tube amplifiers from 50-60x look so miserable with such small capacitors.  It is especially true for stereo amplifiers when PS is used for both channels in parallel without any separation. I can say for sure such a PS will not work for a SET amplifier without feedback even if it is just 2 watt power.   

How does it work in all these vintage amplifiers? Does feedback make them less sensitive to PS or the reason is the push-pull topology?

@alexberger Do some of these vintage amps use a choke in the power supply?

Hi @invalid ,

Yes most of vintage amplifiers use chokes in power supply.

But they use very small capacitors in B+.

The issue with small capacitors is not the 120Hz noise from AC , but voltage stability during playing of load and complex music.