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J.N. Stills 70 watt integrated amp

hayseed

hayseed

Herder of sheep
Has anyone here built Joseph Norwood Stills 70 watt integrated tube amp from "Glass Audio Projects"? I'm sort of on the fence about ordering parts to build it. It would be my first ground up build.

If need be I can try and post the schematics for full review.

Looking for opinions I guess.

Cheers, Guy.
 
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hayseed said:
If need be I can try and post the schematics for full review.

Looking for opinions I guess.

Cheers, Guy.
Click to expand...

Please do.
This thread jogged my memory. I was at an audio show in western Pa. some years back and Ryan Inman was there with his build of that amp. This was not long after it was published. I had listened to it and recall being thoughly impressed. Time moved on and my thoughts of building one myself passed. Now I have time to do such things I would consider building one myself.
 
vinylkid58 said:
Go for it. Let me guess, PP KT88?

jeff
Click to expand...

Heh yep four of em, doubles as a space heater.

I was a little afraid I would get replies like, "70 watts, what do you need all that power for?".

I have yet to hear a person say, "I love this car I just wish it had a little less horse power."

I will post the schematic in the morning, I'll need daylight to take the picture.

This has been in the dream stage for about a year now, I plan to build some horns to go with it, you should be able to hear it in space, I hope they like jazz up there.
 
hayseed said:
I was a little afraid I would get replies like, "70 watts, what do you need all that power for?".
Click to expand...

if you insist. What do you need that much power for?

....asks the guy who's working out a deal to end up with a pair of 100 watt monoblocks.
 
Okay schematics away.
100_2810.jpg

100_2809.jpg


I can load up a parts list too if need be.

So..upon review, will this thing work or am I looking at a "Reds fuse popper"

Thanks, Guy.
 
Hi Guy,

Looks like the splitter is the popular Mullard.

The other popular splitter is the Williamson. The Paraphase and later Floating Paraphase were the first splitters for PP.

Do they say anything in the article about it? I bet it will work and sound nice!

If you could please post the parts list that would great!

Randy
 
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Thanks for the replies, you know I love this forum right?
I really should become a paying member.

I should also say that I'm a "solder by numbers" guy. I can follow directions but I don't really know what the theory is behind what I'm doing. So when you say splitter the first thing that comes to mind is the air dam on the front of my car. :D

It is a good article though.
So here is the parts list, if it is unclear I can type it out too.
Behold!
100_2811.jpg


this is a photo of the S-5 16 watt tube amp that left me wanting more.
100_2068.jpg


Thanks again, Guy.
 
Shadowdog I went ahead and transcribed the whole article and dropped it in two parts in your PM box. I can say for certain the article has been read by me through and through.

I have been kicking this idea around for a long time, I guess I may as well just go for it, I figure if I order the parts and the are sitting there staring at me I will have no choice but to build it.

I will document the daylights out of this build, the good and the bad, I promise.

Stay tuned.

Cheers, Guy.
 
Hi Guy -- Stills authored a number of articles for Glass Audio, and while I could pick at some aspects of his designs, I do applaud his KISS approach and how he directed his projects to all levels of diyers.

One comment I would make for your consideration is the OPT. Stills always championed Hammond, likely because of their numerous outlets and quantity regarding availability. And while the particular Hammond he chose for this amplifier has had good reviews, no Hammond OPT can match the performance of Dynaco transformers or their modern day clones. Plus, the Hammond transformers require the goofy feedback selection switch and reconfiguration of the secondary wiring to accommodate all the various output taps, where as you have no such issues with the Dynaco clones.

If you did upgrade to a Dynaclone (MK III) transformer, it would be a perfect match for this amplifier, and provide a significant performance upgrade, but would require a reworking of the feedback/stability networks. I realize that this is beyond your capability at the moment, but did want you to realize that a notable performance improvement is possible with this swap if you have facilities/friends who are capable of making the necessary changes for you.

Other than than, you should enjoy the amplifier very much.

Good luck with your build!

Dave
 
Guy,

Thanks! Been getting Error can't log onto server just for AK. Pulled the plug on 3-4G hub to reset!

Regards,

Randy
 
dcgillespie said:
Hi Guy -- Stills authored a number of articles for Glass Audio, and while I could pick at some aspects of his designs, I do applaud his KISS approach and how he directed his projects to all levels of diyers.

One comment I would make for your consideration is the OPT. Stills always championed Hammond, likely because of their numerous outlets and quantity regarding availability. And while the particular Hammond he chose for this amplifier has had good reviews, no Hammond OPT can match the performance of Dynaco transformers or their modern day clones. Plus, the Hammond transformers require the goofy feedback selection switch and reconfiguration of the secondary wiring to accommodate all the various output taps, where as you have no such issues with the Dynaco clones.

If you did upgrade to a Dynaclone (MK III) transformer, it would be a perfect match for this amplifier, and provide a significant performance upgrade, but would require a reworking of the feedback/stability networks. I realize that this is beyond your capability at the moment, but did want you to realize that a notable performance improvement is possible with this swap if you have facilities/friends who are capable of making the necessary changes for you.

Other than than, you should enjoy the amplifier very much.

Good luck with your build!

Dave
Click to expand...

Hey Dave thanks for the suggestions, it really is something to think about. I'll have to do some price comparisons too. I have a pretty tight budget. As I was thinking about this I figured if I can just get it built I can then upgrade parts later as the budget permits.
Thanks again for the response, and words of encouragement.
Cheers Guy.
 
J. N. Still has designed several tube power amps. (The amp in question in the OP is a POWER AMP-not an integrated). The 70W design uses 4 KT-88 tubes in the output, the schematic posted above is NOT the 70W amp. Rather, it is a 30W design, using 2 KT-88 tubes in the output. It is a MONO amp, 2 being required for stereo.
 
Phototone said:
J. N. Still has designed several tube power amps. (The amp in question in the OP is a POWER AMP-not an integrated). The 70W design uses 4 KT-88 tubes in the output, the schematic posted above is NOT the 70W amp. Rather, it is a 30W design, using 2 KT-88 tubes in the output. It is a MONO amp, 2 being required for stereo.
Click to expand...

The schematic shows one side of the amp, you will notice in the parts list it explains that. The article calls for a matched quad of KT-88s. I have poured over quite a few schematics and there is an even split some will show the full lay out, if you will, and others will specify "left or right side shown".

The stereo schematics in the RCA tube manual have single tubes in the power supplies but note that an extra tube, wired in series, is required for "stereo".

That is the only thing I don't really like about the J.N. Stills amp, well that and the "hum control thing". I like the notion of an all glass set up. Word around the campfire is that the "bridged diode" gizmo is superior to a couple of tubes, I'm certain it's less expensive.

The real story here isn't so much that I want to become a card carrying electronics whiz, I want a great sound system like you find in the high end audiophile cataloges but I don't want to drop 10+ grand on it. I could never justify that kind of expense. A turntable that costs more than my tractor? It's not going to happen. I may not be a whiz but I am pretty crafty, I can build just about anything. I'm writing this from the "fortress of solitude" that I built from the ground up. With the exception of my fancy new tractor, I have rebuilt most of the equipment here. I can read a manual and I can follow directions. I like to think I'm following the "can do" spirit that made this country great.

Sorry for the little ramble there, but now you know where I'm comming from. Thanks for the input, either way.
Cheers, Guy.
 
This is not an intergrated amp its a power amp with a slector switch on the front of it , like a lot of the newer Chinese amps , It would need a line stage and a phono stage to be a true integreated amp on a phono stage with the line stage built in too have enough gain built in for a mm phono cartridge .

The sound of it will depend on what output transformer you choose to use with it .

http://www.diytube.com/phpBB2/viewtopic.php?t=5651
 
Hay -- Be aware that there is an error on the power supply page. The secondary center tap of transformer T1 (and all the items connected to it) must be grounded. If not, then the heaters are not referenced to ground, and there is no return circuit for the B+ delay relay to operate from as shown.

Dave
 
battradio said:
This is not an intergrated amp its a power amp with a slector switch on the front of it , like a lot of the newer Chinese amps , It would need a line stage and a phono stage to be a true integreated amp on a phono stage with the line stage built in too have enough gain built in for a mm phono cartridge .

The sound of it will depend on what output transformer you choose to use with it .

http://www.diytube.com/phpBB2/viewtopic.php?t=5651
Click to expand...

Stalker, go read what I said, I don't want to copy and paste it.

I pretty much knew I was going to be into a preamp, I was thinking about headphones too. I don't know why, I don't have any neighbors. The life of a bachelor farmer is a tough one.

You wouldn't want to buy a motorcycle would you?

Thanks for the reply.
Take 'er easy, Guy.
 
dcgillespie said:
Hay -- Be aware that there is an error on the power supply page. The secondary center tap of transformer T1 (and all the items connected to it) must be grounded. If not, then the heaters are not referenced to ground, and there is no return circuit for the B+ delay relay to operate from as shown.

Dave
Click to expand...

Dave, thanks for the heads up.

Cheers, Guy.
 
I'm a bit confused about the filter caps, C4 and C5. I'm assuming they're wired in series, which doubles the voltage, but that's still only 700 volts, connected directly to 800 volts on the windings?
 
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