Tube amplifiers and interstage transformers

I agree with Charles1dad and Larryi, most of the best tube amplifiers I have heard have interstage transformers. And like I said before, some of the highly regarded ones also have interstage transformers.

It looks like if you want your interstage transformer not to reduce the bandwidth or affect negatively the sound you need to buy a really good one.

Still, a lot of amplifier designers and people with high knowledge of audio will go for no interstage transformer approach.

The issue is that besides the impedance matching Interstage transformers bring a kind of naturalness to the sound, question would be how?

I have a 45 SET amp built by Bob Danielak and it sounds amazing. It does not have interstage transformers at all.

Some of the Audio Note kits have interstage transformers and people really talk great things about them.

Alan,
As is usually the case the key is execution. A top quality IT used by a talented builder and placed in a good circuit will turn out fine.I certainly can't offer an explanation but this proper use of IT yields such naturalness and striking realism.My amp's builder Israel Blume much prefers the IT rather than a capacitor in the signal path. Of course other builder/designers will feel the opposite and have their own approach.I heard my amp paired with the Atma-Sphere MP-1 and the sound was also fabulous. My line stage has an IT and is sublime with this amplifier.There's always different paths to great results.
Regards,

Regardless of the technical hows, that is the bottom line: it depends on the implementation.

Maybe I could ask Bob Danielak to build a SET IT amplifier for me so I can compare for myself at home. Maybe one with the darling 1626, which by all accounts looks like a "magical" tube in the presence and soundstage area.

The use of the term "impedance matching" isn't really appropriate for the majority of interstage transformer usage.

Typically output transformers are used to "match" the high impedance of a tube to the low impedance of a speaker so they usually have rather large stepdown ratios.

In the case interstage coupling, tranformers with ratios around unity are typically used. A 1:1 doesn't help with impedance matching, Small step up ratios make the impedance matching worse and it is only the transformers with a stepdown ratio that help in the impedance matching situation and you typically see them used for the drive of an A2 grid.

dave

Thanks for jumping in Dave with a real technical explanation. Could you help us here giving us an idea why interstage transformers when properly implemented add a kind of natural and openness to the sound?

Alan