The Nemesis 813 PP Amplifier

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steve s
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#241 Re: The Nemesis 813 PP Amplifier

Post by steve s »

Ray P wrote: Mon Apr 08, 2019 7:11 am It's not Russion in origin but a WW2 copy of a German Wehrmacht transmitter valve.
That's a fair point Ray..
But Russian valves are very often a copy of one of the West's tubes, but it does not mean they will sound as good as the originals...although I've heard some very nice new 2a3's over the years and some of the 300b's are getting quite good
But as always, beauty is in the eye of the beholder as they say...
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IslandPink
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#242 Re: The Nemesis 813 PP Amplifier

Post by IslandPink »

The 4P1L is definitely a fine-sounding valve, Steve. I wouldn't say the same about the 6C4C's. The GM70 , especially the copper, does seem to be an exception too ( though the filament supply is critical ).
The equivalent Russian IDHT's to common types seem to be poorer-sounding, except the 6N6P's of the right vintage ( pre-1990's ) , though those are really only equivalent to ECC99's, which are not great in my experience.
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izzy wizzy
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#243 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

IslandPink wrote: Mon Apr 08, 2019 11:31 am The 4P1L is definitely a fine-sounding valve, Steve. I wouldn't say the same about the 6C4C's. The GM70 , especially the copper, does seem to be an exception too ( though the filament supply is critical ).
The equivalent Russian IDHT's to common types seem to be poorer-sounding, except the 6N6P's of the right vintage ( pre-1990's ) , though those are really only equivalent to ECC99's, which are not great in my experience.
Oh dear. This isn't great for my line stage with my 6N6Ps. If I had 46s in my power amps, I could have 4P1L in the line :)

Or maybe 6V6 triode strapped in the amp leaving 4P1L in the line. I noticed Lynn seemed to mention the 6V6 instead of 45s for the middle of the Karna at some point. Having heard the DHT though, I'd like to keep some of that in the amp. Is a triode strapped 47 an option? Haven't found much info on a short look.

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Stephen
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#244 Re: The Nemesis 813 PP Amplifier

Post by Cressy Snr »

The 6V6 is a stonkingly good valve. I had it triode strapped, driving the JJ 2A3-40s in my pink SET. Sounded sweet and detailed.
GE, JJ and 1950s Mazda (French variety) were the best performers.
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izzy wizzy
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#245 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

Isn't it funny how these things go full circle re valve choices. The first page of this thread starts by questioning use of 813s. And now I'm back at it with the only other valves in it. And yet here on page 17, I still don't have a pair of properly working amplifiers but it feels much closer now than ever before.

It was never my plan for them to be a me too kind of thing as a destination but something that can be developed over time so I must keep my eye on the first stopping point; an amplifier that actually goes. Would seem simple enough but hasn't quite worked out to be; this being the first amplifier I've tried to build at about a dozen attempts over more than 15 years.

So being a bit picky right now over 46, 4P1L, 6V6 seems funny to me however would still love it to be 46s :D

Thanks for the input guys.

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Stephen
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IslandPink
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#246 Re: The Nemesis 813 PP Amplifier

Post by IslandPink »

izzy wizzy wrote: Mon Apr 08, 2019 12:20 pm Oh dear. This isn't great for my line stage with my 6N6Ps. If I had 46s in my power amps, I could have 4P1L in the line :)
No, I mean that 6N6P's are very good, the ECC99 isn't, at least in PP mode. I tried ECC99, 5687 and 6N6P as PP drivers for 300B's , the 6N6P's were best, although that may have been slightly due to imbalance ( = 2nd-harmonic ) as Nick says the 6N6P's are typically not as well matched as 5687's. But anyway, I recommend pre-1990's 6N6P's. The bad ones (I tried in an Aikido driver) are the nice looking gold-grid ones , they have a nasty 'edge' to them.
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IslandPink
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#247 Re: The Nemesis 813 PP Amplifier

Post by IslandPink »

Thomas really isn't helping your project -
http://vinylsavor.blogspot.com/2019/04/ ... -mono.html
"Once you find out ... the Circumstances ; then you can go out"
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izzy wizzy
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#248 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

IslandPink wrote: Sat Apr 20, 2019 3:46 pm Thomas really isn't helping your project -
http://vinylsavor.blogspot.com/2019/04/ ... -mono.html
Yup. He's got them all. Surely my 4P1Ls will arrive soon and can move on from '46 land' and hope it won't be too traumatic. I should really be wiring up them loctals ready to just plug them in.
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izzy wizzy
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#249 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

Got some cheap chinese sockets and the 4P1Ls arrived this week. First insertion of valve meant I couldn't get it out and when I finally did, it ripped the pin sockets out of the base. Had to do some prising of valve socket pins to get them in and then beant them over so they wouldn't come out.

Popped them in the amp and after a few wrong moves, got it going. But it hums like mad which is a bit annoying. I've AC heated them but never seen anyone AC heat them. Took the connection to the tail from the fil centre taps. I'll try DC as a next move which should be relatively easy but annoying. Have heard they are microphonic and sure enough they are, much more so than the 46s.

Looked at how others triode wire them and most connect G2 and G3 to anode. I've never done that before, must be a reason, but followed what others do. Normally G3 goes to the cathode/fil. Maybe I should try a stopper on G2 before DC fils.

So now I have one very quiet 46-813 and one mad humming 4P1L-813. There are still some slight differences in the fixed bias circuits to the 813s so should really sort them out before proceeding. I would never have thought it would be this hard but think it will be worth the hassle.

Cheers,
Stephen
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izzy wizzy
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#250 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

Thought I'd have another go with AC. Paralleled the 4P1L filaments for 2.1V and took the common tail feed off resistors across the fils. Way less hum but it varied when I wiggled the valves in the socket. These cheap Chinese sockets are rubbish. Too tight to get the valve in as sold and I may have prised the contacts apart too much for a snug fit. It might only be the loctal pin that is loose. So hard to tell. Any other sockets cost more than the valves :shock: but may have to be the plan. It's quiet enough to be able to do a comparison with the 46 amp hopefully tomorrow.

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Stephen
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IslandPink
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#251 Re: The Nemesis 813 PP Amplifier

Post by IslandPink »

My sympathies. I was lucky enough to get a few teflon/silver-plated sockets a few years ago from Gerry. Their only fault is that the central sleeve tends to follow the valve out, when you pull the valve.
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izzy wizzy
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#252 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

I'm trying with the 2nd pair of sockets to knock them into shape with a bit more finesse so have taken the sockets out to get the loctal pin right first; tight enough but not too tight and then fiddle with the individual sockets to get them right and then reassemble the socket and bend the socket tabs over at right angles to hold them in. From new, if I put the valve in, all the sockets come out with it. If I got the valve all the way in, I doubt I'd get it out. Even with all this, I doubt I'll get the valve out without some kind of lever. But I keep telling myself, the valves are cheap :)
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izzy wizzy
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#253 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

Tonight had a chance to compare channels. For completeness I should swap the amps over on the speakers to see if I hear the same differences but not tonight. The 4P1Ls are doing more of what I want. 46s are very nice but maybe not having 46s could be a good thing. I can see why people like the 4P1L and from the comparisons so far on a variety of music, I prefer them which is quite exciting.

Down side are microphonics which they are known for. I have seen ideas on this so will have to read more.

I will need DC on the fils and thank goodness, they're low current so I'll have to look at how to do that in a PP arrangement. Options I've seen are parallel with the tail taken from the centre tap of the fils but have also seen series with the tail taken from the centre join of the two fils. Not sure of which is technically better.

And if they are series fed, is the voltage more important or the current? If voltage, then series feed may be not the go and if current is important, then parallel not so good. hmmmm .... no don't want that but if anyone has experience or ideas, that would be welcome.

Cheers,
Stephen
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izzy wizzy
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#254 Re: The Nemesis 813 PP Amplifier

Post by izzy wizzy »

Second channel is now 4P1L. This frees up the 2.5V transformers that were feeding the 46s. They were meant for the 866 MVs. This is an area where things went very wrong before but fingers crossed, not this time.

The 4P1L need DC and my choice is now Andrew's boards if available but failing that, Rod Coleman's. That's 4 supplies in all. Time for a rumage in the shed for transformers.

I'm kicking my self a bit as I should have used 4 supplies on the 813s; 2 x 5V supply per 813. It would have cost me no more and offered better flexibility and from what I read, possibly better sound keeping the fils seperate rather than in parallel. They're relatively cheap and I still might do it which would leave 4 supplies left over. Maybe some 833 people might want them.

Cheers,
Stephen
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Paul Barker
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#255 Re: The Nemesis 813 PP Amplifier

Post by Paul Barker »

“Options I've seen are parallel with the tail taken from the centre tap of the fils but have also seen series with the tail taken from the centre join of the two fils. Not sure of which is technically better.“

2nd way not an option in direct heated 4p1l as bias affected.
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