[zygadr]

Some of you may remember a while back where I experimented with low plate voltage 845SE amps including Sakuma's schematic etc.

Well, after being dismantled for some time due to other projects, I recently built a stereo version that was DIRECT COUPLED..........just for fun as I'd never built such an amp before.

It's basically a paralelled 6SL7 running on 100v which is direct coupled to an 845 that has a B+ of 500 volts.

Being direct coupled and having the 845 running on near 100ma of current, this amp should not work..............but it does!!!

It's probably only a couple of watts, but with 106db horns, it's plenty

One thing I know for sure and have learnt this the hard way : Direct coupling is INCREDIBLE.

I've allways ignored claims that you need great capacitors for coupling and the same for interstage transformers. Well, maybe you do.......................but when you have NOTHING in between driver and power stages..................WOW!!!! 

[JakeJ]

So no caps or resistors n the signal path?  As close to the "straight wire with gain" concept as possible.  Sounds very interesting.  Plus you are running plate voltages on both tubes well below the norm.  Stands to reason you are not getting much power but in your application it's not the issue, sound quality is.

OK, picture or it didn't happen. 

[zygadr]

Correct Jake!

I was expecting to hear little if no difference in the sound but was shocked at what came out of those horns :

Instrument timbres were all of a sudden unmistakable. The music seemed unrestrained and tuneful, bouncing along with pace and rythm............just like the real thing.
A kettle drum roll was jaw dropping as the mallots hit the skin and the copper body was exactly that - ''COPPER''.

I have made many so called ''straight wire with gain'' amps both solid state SE and valve, but all had capacitors somewhere in the chain.

Without starting a war on caps versus transformers, I will have to politely disagree with Nelson Pass's statement that the sins of capacitors are far from the sins comitted by output transformers or the amplifying devices themselves.

This is NOT what I have found.............the only good cap is a dead cap(in the signal path that is)

[JakeJ]

Cool!  All components are "sinful" in their own way but we must use them or the 'trons won't flow.

Again, pictures please and add a schematic if possible.  I'm sure others are lurking with interest!

[zygadr]

Will do when I get a chance

[Steve]

I was expecting to hear little if no difference in the sound but was shocked at what came out of those horns :

Instrument timbres were all of a sudden unmistakable. The music seemed unrestrained and tuneful, bouncing along with pace and rythm............just like the real thing.
A kettle drum roll was jaw dropping as the mallots hit the skin and the copper body was exactly that - ''COPPER''.

I have made many so called ''straight wire with gain'' amps both solid state SE and valve, but all had capacitors somewhere in the chain.

Without starting a war on caps versus transformers, I will have to politely disagree with Nelson Pass's statement that the sins of capacitors are far from the sins comitted by output transformers or the amplifying devices themselves.

This is NOT what I have found.............the only good cap is a dead cap(in the signal path that is)

Hi Zy,

You provided a great observation. Very good capacitors used 15-20 years ago are no longer available (have to special design/order now). Not surprising that "Scientific types" and special interest sellers etc on other forums claimed either "all caps sound the same", or emphasized certain "sounding" caps to match their designs, or designs/tubes pushed; and what capacitors you see/hear today is what is left.   

You provided a great and accurate observation Zy.

[zygadr]

Hi Zy,

You provided a great observation. Very good capacitors used 15-20 years ago are no longer available (have to special design/order now). Not surprising that "Scientific types" and special interest sellers etc on other forums claimed either "all caps sound the same", or emphasized certain "sounding" caps to match their designs, or designs/tubes pushed; and what capacitors you see/hear today is what is left.   

You provided a great and accurate observation Zy.

Cheers Steve.

What you say is dead right. Capacitors do ''something'' to the sound............and what we have at our disposal today is a distortion or veiling of the true signal's heart and soul.
That's the only way I can describe it...............even though it sounds melodramatic and corny

[Fearless Beaver]

Hello zygadr,
would be very, very, very interesting to look at schematics of this direct coupled amp. Also, is it possible to increase output power? My speakers are not so effective