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Vacuum Tube Audio SP14

74.130.29.193
Posted on July 21, 2016 at 11:09:04
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I had so much fun assembling the PH16 phono-stage that I decided to buy the SP14 line-stage kit. I just completed the circuit board and I'm waiting for the enclosure to arrive. It had to be custom drilled because I ordered the Khozmo 64 step remote control volume. Soldering is kind of fun. I still have to solder some jumpers on the back side of the circuit board. Here are some pictures:


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Sounds lik John's got the "bug" :-), posted on July 21, 2016 at 13:26:03
Batman
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Posts: 4194
Location: Western Pennsylvania
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Contributor
  Since: June 16, 2000
 Can't wait to hear your review. There's nothing like the smell of solder in the morning!

Good luck
Bill


 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 13:27:49
terrybbagit
Audiophile

Posts: 14
Joined: November 12, 2009
 I know how you feel John just completed my third kit and am ready to build another one very addictive

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 14:10:09
M3 lover
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Posts: 6604
Location: SW Mich
Joined: May 29, 2005
Contributor
  Since: July 4, 2007
 John, that one interests me too so will look forward to comments after you complete it and have it in your system awhile.

"The secret of life is honesty and fair dealing, if you can fake that you've got it made." Groucho

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 14:59:39
mondial
Audiophile

Posts: 891
Location: S.E. ASIA
Joined: January 14, 2007
 Hi John ,

It's looking good , welcome to the wonderful world of tubes. Can't wait for you to finish these so you can proceed to a tube amp build. I'm sure when the time comes you'll be active also in the tube & tube Diy section of the audio asylum.

Mondial

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 15:22:57
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I used to build kits 30-years ago or so. Now, this might be the least expensive way to gain entry into vacuum tube audio. ;-)

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 15:23:53
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I'll let you know how I like it!

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 15:27:25
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I'm thinking of setting up a second system in our extra bedroom. I still have a pair of small B&W PM1 speakers so I might also build a tube amp. I'll keep you posted.

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 17:49:27
Jeff V.
Audiophile

Posts: 233
Location: California
Joined: April 15, 2006



Hi John,

looks great! I built a SP14 some time a go. Very good sounding preamp. At some point try some vintage Sylvania tubes. I also really liked the Russian Teflons as output caps. Very cheap on the auction site. You can see them mounted on the outside of the PCB on my build. They are BIG! Enjoy!

-Jeff

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 17:51:53
Mick Wolfe
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Posts: 3365
Location: AZ
Joined: October 10, 1999
Contributor
  Since: September 4, 2000
 I have a friend who bought an assembled version. I think I can confidently say you won't be disappointed. Very nice refined sounding pre-amp.

 

Nice, posted on July 21, 2016 at 18:00:17
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 Im liking it except for the three gain controls. Id probably set the left and right gains fixed with resistors to get those pots out of the signal path and use the same volume control you are using. Are you going to use 6SN7 or 12SN7? The latter are cheaper and the ps change is easy. Keep us up to date.
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 18:37:25
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Hi Jeff,

Those Russian Teflons look nice. Maybe I'll look for a pair. What is their capacitance value?

I bought the upgraded 0.33-uF German Mundorf silver-oil PIO caps, which are the black ones on the outside. The brownish-orange 0.22-uF caps on the inside are the standard ones supplied with the kit. My kit has two outputs so I can compare capacitors. I could buy the Russian Teflons to replace the brownish-orange caps.

I also upgraded to vintage Sylvania chrome-dome 6SN7 tubes. They cost only $20 more than the standard 6SN7 tubes normally supplied with the kit.

Thanks,
John Elison



 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 18:39:28
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 > Very nice refined sounding pre-amp.

Good to hear!

Thanks,
John Elison

 

RE: Sounds lik John's got the "bug" :-), posted on July 21, 2016 at 18:41:20
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 > Can't wait to hear your review.

I'll keep you posted.

Thanks!
John Elison

 

Soldering is Kinda Fun--?, posted on July 21, 2016 at 18:47:10
Des
Audiophile

Posts: 2110
Location: Great Barrier Reef
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Contributor
  Since: August 2, 2000
Wow John ! you learn something every day--I don't know how I missed that after 58 years

ha!

Des

 

RE: Nice, posted on July 21, 2016 at 18:48:15
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I'll be using vintage Sylvania chrome-dome 6SN7's.

> I'd probably set the left and right gains fixed with resistors to get those pots out of the signal path and use the same volume control you are using.

That sounds like a good idea. Those extra pots comprise the balance control, which I rarely use on my present preamplifier.

Thanks,
John Elison

 

RE: Vacuum Tube Audio SP14, posted on July 21, 2016 at 19:18:30
Jeff V.
Audiophile

Posts: 233
Location: California
Joined: April 15, 2006
 John,

The Russian Teflons are FT-3 .22uf. I have listened to the Mundorfs you have in other projects. A very good capacitor in my opinion. I look forward to your opinions of the SP-14. Have fun!

 

RE: Nice, posted on July 22, 2016 at 08:41:20
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 Yes I never used my balance control and dont have one now. I really like that circuit. Im still in nursing rehab and havent soldered since last September. Im jealous! Thanks for letting me live vicariously through you.




ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

Yes it is!!, posted on July 22, 2016 at 12:17:01
Cuernavaca
Audiophile

Posts: 878
Location: NW
Joined: December 23, 2011
 I never tried soldering until I was recovering from a lengthy illness about 15 years ago. I upgraded/repaired a few Dynacos, built 2 Grounded Grid preamps, a Bottlehead preamp and have fixed several solid state components that had various problems that needed some solder work.

I recently purchased a Hafler Transnova 9500 amp with a driver board problem(intermittent crackling in one channel), I am thankful that I have some soldering skills, was able to eliminate the problem by removing excess solder on the board and resoldering more than a few questionable connections. It's a skill that can come in handy. The local repair shop said he couldn't find the problem.

Thomas
"I've never owned a firearm, but I do have an attack parrot!"

 

RE: Vacuum Tube Audio SP14, posted on July 22, 2016 at 15:19:03
WntrMute2
Audiophile

Posts: 782
Location: Detroit
Joined: September 16, 2002





A couple of other tube recommendations that won't break the bank. I'm partial to the RCA staggered blackplate 6SN7. I like it in both the SP-14 that Don Sachs built for me as well as my Wright WLA-12a. Not quite as dark as those Sylvanias but without too much top endyness. I also have a pair of metal based Russian 6SN7s that sound wonderful but are rare as hen's teeth. Finally, i have a pair of beautiful Shuguang Treasure CV181-Zs which are a drop in replacement. They may be too tall for your unit. Don built mine with the tubes exposed. But worth a try.

 

RE: Vacuum Tube Audio SP14, posted on July 22, 2016 at 15:39:11
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Thanks for the recommendations. I'll definitely keep them in mind for the future.

Those CV181-Zs would have to be awfully good to pay $480 for a set of four. Since I'm new to tube equipment, I think I'll try to have some fun with my Sylvania chrome-domes before beginning swapping out tubes.

Thanks again,
John Elison

 

6sn7 tubes, posted on July 22, 2016 at 17:54:04
Cuernavaca
Audiophile

Posts: 878
Location: NW
Joined: December 23, 2011
 I have a Don Sachs built SP-14, and have quite a few 6sn7's, the chrome dome Sylvania's are good as well as the bottom getter Sylvania's, (bad boys), the ones with the 3 hole plates. There a lot of good 6sn7 tubes out there, I also like the Raytheon VT-231 bottom getter, (Navy markings) amognst many others.

Don suggested the Bendix 5852 rectifier. It took awhile to find one reasonably priced...The SP-14 is one nice preamp!

Thomas
"I've never owned a firearm, but I do have an attack parrot!"

 

No, No, No, posted on July 22, 2016 at 18:36:30
WntrMute2
Audiophile

Posts: 782
Location: Detroit
Joined: September 16, 2002
 You only need two tubes. The outboard ones make the difference while the inboard ones are buffers. Also, I bought those tubes for about $139.00 delivered. Check out the forum:

 

Don't mean to rain on your parade, posted on July 22, 2016 at 21:24:36
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 John, you are a way smart guy, and I enjoy your informative posts on this forum (I've learned a lot). I am also happy to see that you are delving into hollow state technology. There is no amplifying device more linear than a triode gain stage. Also, I can certainly relate to the joy of making things with your own hands. BTW, the Khozmo attenuators are a really great option.

Just keep in mind, that in spite of a lot of sales pitch, this may not be the end all be all approach to a "preamp". If I get this right, (haven't found a schematic although I've looked) I call this a line stage, preamps have phono stages. Even by line stage standards, this has an unnecessarily complicated attenuation scheme (looks like you've remedied that). This may also be cathode follower topology, as that is the only reason why I could figure it would need 2 6SN7s per channel. In my book, this may not be an "uncompromised design".

In spite of that, hope you're having fun, and enjoy it. Keep on trucking, DIY is big fun.

twystd

 

What exactly do you mean, then????, posted on July 22, 2016 at 21:32:09
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Are you raining or not????

 

RE: What exactly do you mean, then????, posted on July 22, 2016 at 21:57:33
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 No John, just want you to explore DIY and tubes even more. I am just trying to say that there are more options out there, please keep on DIY'n.

To be truthful, I don't like slamming any projects. I just get my hackles up about companies that oversell their projects with hyperbole, and yes, I feel that this is what is going on here. Us tube fanatics know that cathode followers aren't "no compromise" designs.

Is that what it is? Well really don't know, but with no schematic available makes me wonder. Believe me, there is NOTHING new about tube schematics, and when companies don't give them, I suspect they may have something to hide.

If you are going to claim a no compromise design you need to show me more than these folks are doing.

twystd

 

RE: What exactly do you mean, then????, posted on July 22, 2016 at 23:55:52
John Elison
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Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 > If you are going to claim a no compromise design you need to show me more than these folks are doing.

I didn't claim it to be a no compromise design. I bought it because it fit my budget. Tube equipment can be very expensive these days and Vacuum Tube Audio products seem like a good value to me. So far I'm very pleased with sound quality from my $680 PH16 phono-stage. The SP14 line-stage cost a little bit more, but still seemed very reasonable to me.

The schematic for the SP14 is available online and is shown below. Do you think this is a compromised design relative to its price?



 

RE: What exactly do you mean, then????, posted on July 23, 2016 at 08:46:10
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002

Not meaning to hi-jack your thread but......

The first stage could be seen as a triode gain stage loaded with a triode CCS.

An improvement to the over all design (IMO) would be to eliminate the second stage altogether and take the output off the top of R4 (the "mu" output of the CCS).

A triode doesn't make a very good CCS plate load. It could be replaced with a pentode for better performance or better yet a cascoded pair of depletion mode MosFets like the DN2540.

A step up from that would be Gary Pimm's self biased CCS shown above.

This would give a very low output impedance.

Over all this would be a big improvement and the total cost of the project would be less if the project was designed this way to start with. (one less tube per channel, one less tube socket per channel, less current needed from the power supply, etc..)

If you have to do this on your own......I'm not sure what your cost would be.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: What exactly do you mean, then????, posted on July 23, 2016 at 09:33:18
John Elison
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Posts: 23900
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Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Okay! So, in your opinion it's basically a waste of money. Such is life!

Can you recommend another tube preamp that is designed correctly and includes equivalent features with a price that's the same or less? The special Mundorf output caps added $95 and the remote volume control added $290. Then, with a $20 tube upgrade and shipping charges of $30, total cost for this kit was $1355. I don't know anything about amplifier design, but if you know of a better tube preamp at the same price, I might buy it.

What do you think about the M-125 monoblock amplifiers. I estimate the kit price including tubes will run about $2100 a pair. Do you think these amplifiers are worth the money. If not, can you recommend another tube amplifier with at least 125-wpc and better performance that costs the same or less. I'm thinking of building a tube power amplifier kit as my next project and I need a minimum of 125-wpc to drive my Thiel's.

Thanks!
John Elison

 

RE: What exactly do you mean, then????, posted on July 23, 2016 at 12:07:25
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 John, I certainly didn't mean to offend you, and I apologize. I have been nothing but impressed by your posts on this forum. I know you didn't claim it was a no compromise design, but the manufacturer did. They also claimed it is "the best preamplifier kit available at any price." That statement is certainly debatable to say the least. Claiming anything in the audio world is the best is BS. The best according to who?

I'm sure that the design sounds just fine, and I'm glad you enjoy it. I don't think it is a waste of money. The only reason I posted anything negative, which I probably shouldn't have, is that the site selling the SP14 made some pretty strong claims. I feel there is way too much hype involved in our hobby, and hyperbolic claims by sellers, just rubs me the wrong way.

As far as critiquing the design, I think I'll pass on that. I will say this isn't something I would design for the purpose, but I'm a minimalist. This is just my own audio dogma, which is more of my opinion, rather than a proven fact, and you know what they say about opinions. I certainly wouldn't claim any design that I may make, is the best, that is just unsupportable.

Again I apologize, and am very happy to see you getting involved in DIY and tubes. I hope you continue down this path, and I hope you enjoy listening with this preamp. You are right, DIY does offer good value, and has the satisfaction of making something with your own hands. Don't let anything I say discourage your efforts.

twystd

 

I can see a couple regulators., posted on July 23, 2016 at 14:32:19
violinist3
Audiophile

Posts: 2922
Location: San Diego California
Joined: August 7, 2003
 I like good regulation. I'm tempted.

 

I bought a pair of the CV-181s ..., posted on July 23, 2016 at 14:40:43
Dave Pogue
Audiophile

Posts: 11689
Location: DC Area
Joined: October 9, 2001
 ... for my Modwright/Oppo 105. Thought they looked cool. Sonically, they rank 4th behind two pairs of Sylvanias and one of GEs, all NOS, all cheaper than the 181s. Not an especially good buy, IMO.

 

RE: What exactly do you mean, then????, posted on July 23, 2016 at 18:14:17
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 Sorry John, I probably shouldn't have said anything to start with.

I build all my own stuff and do not pay attention to what's available, gear wise, so I have no recommendations.

When I do see schematics of available stuff, most of the time I can't help but wonder why they design things the way they do.

I should have kept those thoughts to myself.

When you get to the point where you want to build from scratch, give me a heads up.

When building from scratch your design will be guided by the depth of your understand of theory and the level of performance is only limited by how complete that understanding is.

That is to say, if I knew more my system would sound better.

I don't find much guidance looking at commercial products. Most are built to a price point and are not no holds barred designs.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Eloquently said, and I couldn't agree more., posted on July 23, 2016 at 19:26:33
twystd
Audiophile

Posts: 2723
Location: Austin,Texas
Joined: December 9, 2000
 I know what you mean about saying anything to start with, I feel the same way, and am sorry I started this whole mess. I find it hard to keep my mouth shut.

However I am pissed at self serving unsubstantiated claims by commercial interest in this hobby. Not all commercial interests join in on hyperbolic claims. I think there should be ethics involved in commercial advertising, and that extraordinary claims should be backed up with extraordinary evidence.

BTW, for what it's worth, I agree with both your technical observations on the product in question, and your bigger underlying philosophy of understanding. Still working on that one, and hopefully will to the day I die.

twystd

 

RE: Eloquently said, and I couldn't agree more., posted on July 23, 2016 at 20:38:11
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 "Still working on that one, and hopefully will to the day I die. "

That's the thing about knowledge, the more you learn, the more you understand how much more you need to learn.

The day I stop learning is the day I die.

But for now I'm "Still working the problem".


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: What exactly do you mean, then????, posted on July 24, 2016 at 07:14:54
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I seriously doubt I will ever get to the point that I am building amplifiers from scratch. On the other hand, perhaps you know of some manufacturers of tube equipment who design their circuits in accordance with your specifications. Are there any manufacturers you would recommend regardless of price?

Thanks,
John Elison

 

RE: What exactly do you mean, then????, posted on July 25, 2016 at 11:11:52
rosendds@frontiernet.net
Audiophile

Posts: 599
Location: North East
Joined: November 13, 2010
 It will be nice to read your review of the preamp.I built a Hagerman Clarinet about 5 years ago that I still like,but would love to compare it to the SP14.Do you know if all of the supplied resistors are metal film?

Dave

 

RE: What exactly do you mean, then????, posted on July 25, 2016 at 12:13:11
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Yes, all the resistors are metal film. Most of the resistors in the preamp section of the circuit board are precision metal film Dale resistors. They are brown in color with their values stated numerically. The other resistors are also metal film but lower tolerance resistors and use standard color code to depict their values.

I'll definitely keep you posted on how this preamp sounds when it's completed. I'm currently waiting for the enclosure to arrive so I can wire everything together.

Best regards,
John Elison


 

RE: Vacuum Tube Audio SP14, posted on July 25, 2016 at 18:15:36
wheezer
Audiophile

Posts: 4309
Joined: January 24, 2001
 I "think" that's an Aikido (John Broskie) circuit or a variant.

 

RE: Vacuum Tube Audio SP14, posted on July 26, 2016 at 03:37:35
rosendds@frontiernet.net
Audiophile

Posts: 599
Location: North East
Joined: November 13, 2010
 Nice build.Are you putting it in the case that has the tubes exposed on top or enclosed in the case?I read on Don Sachs website that the larger octal tubes sound better than smaller 12ax7 or 12au7 type tubes.

 

RE: Vacuum Tube Audio SP14, posted on July 26, 2016 at 06:40:15
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I'm putting mine in the standard enclosure that hides the tubes inside. The SP14 uses 6SN7 tubes.


 

RE: Nice, posted on July 28, 2016 at 14:26:52
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I just received the balance control pots and they appear to be very high quality stepped attenuators. Therefore, I doubt there is much to be gained by eliminating them from the circuit. I'm going to incorporate them into my preamp just in case I need to adjust balance.

Hope you get back in shape to do some more soldering yourself. These are fun kits to build.

Good luck,
John Elison

 

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