NOSValves said:
Russell,
Don't get me wrong I'm not saying the circuit shouldn't be built without the iron. But what many I guess don't realize is... The front end of a Marantz 8B is nothing to right home about. A pentode input tube (voltage amp) with a long tailed pair phase splitter. Very basic but solid design in fact the entire amp is very basic. The magic is definitely in the Iron.
Craig
Yes the front ends description sound archaic, but sounds great.
A pentode first stage? sounds like it could be noisey...but it isnt. Many simple circuits sound great. The only way this debate could be settled is to try the outputs with a different circuit, and I doubt thats going to happen, unless some lucky dude out there happens to have a couple sitting around! BTW, have you ever tried this (clone 8b) or is this just a feeling you have? I gues the closest way to somewhat settle the debate is to build a 8B clone. Steve at Angela has, and was very impressed. I was led to believe that it used someother transformer, but dont know which one it was, as I mentioned he never printed those plans in the DIY section even though I bugged him regularly about it for years in the 90s. If anyone did have a pair of outputs from marantz, Steve probably would! Yes the old tranformers are nice, but I dont know if they are the only source of the magic. An output transformer is probably one of the biggest weak points in a pushpull design..basically adesign compromise. A good transformer does as little damage as possible and logically isnt a source of magic in and of itself. That being said, these particular transformers were VERY important to this circuit, as is evidenced by the historical fact of all the trouble saul went to to get them done proper. NO DOUBT they have a great deal to do with the sound, but simple though it might be, SO does the circuit. Many old front end designs are extremely simple, especially the long tailed pair. they also happen to sound excellent. One of my current amps uses 1/2 of a 12ax7a as the amp, then a 12au7a as phase splitter. Basically it is extremely simple , but is so transparent
it is ridiculous.In the 8B, that pentode first tube also has a lot of drive, and when run quietly in the proper circuit, works great. BTW, your previous post spoke of the importance of those coils to the circuit, but now in your latest post you state the circuit isnt the magic, the transformers are. Clearly we are both right to some extent! The old Mullard circuits similarly use a pentode (ef 86 as the first tube, then a dual triode for phase splitting duties, and can give excellent results as well. Sad thing is, these amps are getting very old. One must wonder how long these tranformers service life is. I similarly wonder about my Mc 225 in that regard. I have grown up surrounded by these pieces and plenty of NOS tubes. Even sadder, I guess I will see the day when these fine amps are crapping out. Already the nos tube suppliers are starting to run out. Maybe the transformers are more durable than I fear, I hope so. I dont know how having one rewound would come out, I am sure someone out there knows. Unfortunately, I have never owned an 8B, but know someone who did and spent time lusting after it. It was sold and I couldnt swing it. They also had a pair of the older mono block twos maybe? I cant remember. They were similar appearing to the 8B, but less tubes of course. The Mcintosh seems to be more rare than the macintosh stuff, just dont see much of it. Very attractive stuff.
Party on,
Russellc
