Start to Salivate - My Tube Amp Candidates - Your thoughts welcome

[Nodric]

Hi all,

New member/first post, so be gentle! Also I am no expert, just someone who has played with electronics over the years, and can solder to a good standard

Having just completed my Scope Clock See Photos Here I am ready to start on my 'first' amplifier project, and am blessed with having acquired 1200+ tubes (All NOS), along with a nice Tektronix scope, HP audio sig gen, and lot's of other nice test gear and discrete components, including 300+ capacitors that all test perfectly (including leakage thanks to the Heathkit cap tester I also got).

Having sorted and tested my major numbers I have the following candidates for pre-amp and power amp. All tubes match within acceptable measurements, so I'm very lucky!

2 x Tungsol 6550 Grey 3 hole Plates Top and Side getters (only option is SE as I don't have any more and they are sooo rare)
2 x RCA Red Base 5692 (Read that they are sonically stunning?)
3 x RCA Brown Base 5692 (Could I combine these well with the red base examples?)
2 x GE 7027a
5 x GE 8417
1 x RCA 8417
2 x GE 5 Star 6386 Matched Pair (Ultra Rare I read?)
1 x GE 6386 (not 5 star)
1 x GE EL34/6CA7 (wish I had a pair)
5 x GE 5751
1 x United Electron 5751
1 x RCA 5751WA
1 x GE 12AX7 (wish I had more)
3 x GE 12AY7
2 x United Electron 12AY7
7 x GE/RCA 12AV7

I do have many more 12xxx tubes so if I missed any good ones let me know. I also have an array of rectifier tubes (5U4GB/5R4 amongst them), and so if anyone wants to recommend the bests ones to use I'd also be grateful. Main listening is radio, and vinyl (Thorens TD160 with an SME 3009 MKII Improved coupled to a Shure V-15 Type III). Current amp is a Quad 405-2, Quad 34 pre, FM4 tuner coupled to a pair of B&W DM6s. I'd like to continue with the DM6s if they will match well to tubes.

I'd love some feedback on which to choose for which application, although I assume only the 6386s and 12Axxs are only good for pre-amping? I also lean heavily to single ended as this seems to be the 'audiophiles' favorite, although I suspect that comment will generate much debate

Once I have the right tubes chosen, I'll move onto which trannies to use, and then the 'spare tubes' might be offered (really cheap) to a good home, or someone who gives me great advice and help on the way

TIA

N

 

[the_manta]

Welcome on bord !
First, you're a bit on the wrong track. Having a stash of tubes is nice but this guarantees nothing. You can build a perfect amplifier with nearly every kind of tube. Intelligent circuit design makes this possible. On the other hand, there are EL34 which sound awful.
Why not don't you start with some theory about valve operation and circuit design. Don't get me wrong, I won't badmouth your first post but if a 6386 tube is a five-star one or not really is the most unimportant thing when you want to get started in building a tube amp. (When you light the amp up the first time and the tube blows with a nice 'bang' you will have wished it wasn't a five-star !!! )
There are thousands of designs out there with those mainstream and standard tubes you mentioned. Sound is subjective so maybe you like the sound of a starvation mode operated 12AX7 whereas I prefer a 12HG7 with lots of current.
What I want to say is, put the tubes aside, they won't ran away (or get gassy....that takes lots of years) and get familiar with the tube business. Read here in the board, build some small test circuits and amplifiers etc. When you start with the big project at once, your next posts will be titled: "why does my amp oscillate/hum ?", "what's that blue glow ?", "Can I swap a 6L6 with EL34" etc.
You will have much more fun learning and applying everything step by step.
And...this one is important. Never let the so called "audiophiles" try to give you silly ideas. Make your own decisions, ask when you're not sure and try it out.
I hope you don't misconceive my post but experience tells you how not to get started with something new.

PS: Be sure to have some spare tubes for the scope clock. These things eat them up really quickly.

 

[kevinkr]

What Manta said..

One potential choice if you are chomping at the bit would be Tubelab's simple SE using the 6550s in UL or triode mode, but I would first do a whole lot of reading and studying up as suggested by Manta.

 

[Eli Duttman]

Amps and speakers have to be viewed as parts of a whole. What sort of speakers do you already own or plan on acquiring? What are you using for signal sources?

Some of the NOS power tubes you have are valuable and it may make sense to sell them, thereby funding "iron", etc. purchases.

A possible use for the 5692s, which are "glorified" 6SN7s, is in a Williamson topology PP power amp. Really good O/P "iron" is essential, when constructing a Williamson. Otherwise, phase shifts can eat you alive.

 

[Nodric]

What Manta said..

One potential choice if you are chomping at the bit would be Tubelab's simple SE using the 6550s in UL or triode mode, but I would first do a whole lot of reading and studying up as suggested by Manta.

Hey guys thanks for the advice, but maybe I should clarify. I have 30 years of playing with electronics, and was building tube stuff as a teenager back in the 70s, and do have a nice lab at home. I've also worked in related industries for most of my career. I am familiar with safety and testing procedures, and have worked with high voltages for a long time. I used to work on microwave equipment as a job, so I tend to keep my fingers away from the dangerous stuff

However, I have not yet invested time (and money) in a high end amp so far, but that does not mean I've not read the forums/articles quite extensively. I just find myself getting lots of conflicting information, which I guess is the nature of the beast (sound being 'very' subjective).

I have many text books dating back to the 40s, and I do understand a great deal of the theory, but I am not as knowledgeable as many of those who can write schematics and work out NFB, or Bias on the back of their hand, or better still in their heads, so I wanted to seek out some constructive advice on a good combination of tubes from those I've been lucky to acquire. I have access to a 539b so was able to verify the condition and quality of the tubes, all unused before I tested them.

If your advice is to simply read more posts, and then go build a simple amp and slowly graduate to big boy stuff then off I'll trot. I think I am capable of more, and may just have to take pot luck with the various schematics out there, and then read/tune/adjust if the sound does not meet my expectations.

For instance I've seen a nice amp project using the 5692 as a driver for pair of 8417s in SE mode.

I'll keep reading

 

[Nodric]

Amps and speakers have to be viewed as parts of a whole. What sort of speakers do you already own or plan on acquiring? What are you using for signal sources?

Some of the NOS power tubes you have are valuable and it may make sense to sell them, thereby funding "iron", etc. purchases.

A possible use for the 5692s, which are "glorified" 6SN7s, is in a Williamson topology PP power amp. Really good O/P "iron" is essential, when constructing a Williamson. Otherwise, phase shifts can eat you alive.

My current gear is:

Thorens TD160/SME 3009 MKII Improved/ Sure V15 Type III
Quad 405-2/Quad34/FM4
B&W DM6 Penguins

My first thoughts are to replace the Quad elements with the future tube gear.

My primary listening is Radio and Vinyl (Prog Rock/Vocal/Keyboards).

And yes, my plan once I've selected the right sets of tubes for me, is to sell the rest to pay for the O/P and Choke Iron etc. This is partly why I want to narrow down my best options, before I sell the wrong tubes

 

[kevinkr]

Hi Nodric,
Perhaps in your case it is just down to thinking about the sort of system you want to put together - sounds like you're well equipped for the technical end of things, it's just a question of integration, choosing the right speakers, amp design, and sources for what you want to achieve - something I've been working on for a long time.

In any event you will have a lot of fun figuring out what direction to go in and building it out..

 

[overtheairbroadcast]

Never mind my post. I typed too slow and posted even slower... Original post below. I'll add one thing -- Pete Miller's amplifiers seem quite nice and the over the top 300B amp there has got me thinking way down the road when I get that good.


I have read and seen some amplifiers that defy logic in that they should not sound good at all. First they are cheap, use television sweep tubes for output, pentodes for input, mosfets, silicon, and all for about $400 or so. I have just decided that this will be the next likely candidate for project number four for me (I have three so far).

And they sound great. Television sweep tubes! I mean really.

Now I have seen really great tubes in amps that makes you wonder, "what is that horrific noise? "

It boils down to design and the ingredients . Find a good design and spend the money on good components like iron, capacitors, pots, chassis, and all the other things that will make it a great sounding amplifier.

And add in a lot of research and reading. Then construct and test. You'll have fun in the process ; trust me.

 

[Nodric]

Hi Nodric,
Perhaps in your case it is just down to thinking about the sort of system you want to put together - sounds like you're well equipped for the technical end of things, it's just a question of integration, choosing the right speakers, amp design, and sources for what you want to achieve - something I've been working on for a long time.

In any event you will have a lot of fun figuring out what direction to go in and building it out..

I think you maybe right, and that there's no 'magic' answer. I know I love my bass, but it has to be very clean, and I love crisp clear and natural vocals, so I'll focus on what designs seem to have been successful in delivering that for others.

Maybe I'll do a simple RIAA phono stage for my TT and feed that to the 405 and, then take it from there. Maybe I'll keep all the tubes and try several different amp designs, but then I'll have to sell the car to buy the iron

 

[kevinkr]

The 8417 would be prime candidates to sell on, they're worth a lot of money and replacements down the road are not going to be readily available.

From what you've described a fairly large PP amplifier is probably what you need to pursue. I'm running home brew Onkens of >100dB efficiency with 20W GM70 SE amps, and it gets loud, very loud.. What is the efficiency of your B&W speakers?

Definitely check out Morgan Jones latest Valve Amplifiers (edition 4) when it finally shows up at Amazon for some inspiration..

 

[Nodric]

And they sound great. Television sweep tubes! I mean really.

It boils down to design and the ingredients . Find a good design and spend the money on good components like iron, capacitors, pots, chassis, and all the other things that will make it a great sounding amplifier.

And add in a lot of research and reading. Then construct and test. You'll have fun in the process ; trust me.

I think I get it now I'll sift through all the stuff I've printed and book marked, and then start narrowing down amplifier project one...

I also have lot's of TV and Ham tubes so maybe I can mess there sometime too. Have a pair of 807s that would be fun

 

[Nodric]

The 8417 would be prime candidates to sell on, they're worth a lot of money and replacements down the road are not going to be readily available.

From what you've described a fairly large PP amplifier is probably what you need to pursue. I'm running home brew Onkens of >100dB efficiency with 20W GM70 SE amps, and it gets loud, very loud.. What is the efficiency of your B&W speakers?

Definitely check out Morgan Jones latest Valve Amplifiers (edition 4) when it finally shows up at Amazon for some inspiration..

Thanks Kevin.

The B&Ws only have an 88db sensitivity, and need a 100w solid state amp to make them work well, so maybe not the best candidate for a tube project. I was just trying to reserve budget

I certainly follow your reading advice, and look at PP designs more closely.

 

[Eli Duttman]

Thanks Kevin.

The B&Ws only have an 88db sensitivity, and need a 100w solid state amp to make them work well, so maybe not the best candidate for a tube project. I was just trying to reserve budget

I certainly follow your reading advice, and look at PP designs more closely.

The B&Ws need power and good damping factor, in order to "dance". FWIW, I think I see a reasonable path to system synergy. A project of acquisition and complete overhaul of a Harmon/Kardon Citation II, ala Jim McShane, will give you 60 WPC continuous and upwards of 130 WPC instantaneous, along with a good damping factor. That will do very nicely for the DM6s. As the owner of a "Duece", I can tell you the chocolate behemoth betters most SS amps at playing bass.

The higher than usual I/P impedance of a Cit. 2 makes a passive control center quite feasible. Whether you go that route or a buffered volume control with source switching is a matter of personal preference.

There are lots of good phono preamp designs to choose from. The tweaked RCA schematic I've uploaded is about as easy as they come in the building dept. and a highly satisfactory PSU for the circuitry can be built around an inexpensive Allied brand power trafo.

 

[Bibliophile]

Hi Nodric
Love the 'scope clock.
Any link to construction details?
Cheers

 

[boywonder]

Nodric: What's your budget for this project? Do you have any iron? Do you have more than a pair of any output tube candidates?

 

[Tubelab_com]

One potential choice if you are chomping at the bit would be Tubelab's simple SE using the 6550s in UL or triode mode, but I would first do a whole lot of reading

The 6550's in an SSE will make about 8 WPC in triode mode, or about 14 WPC. With 88db speakers it will be loud enough for small room listening, but will not shake the house. It's a good project if you want to build a tube amp, and plan to build a bigger one some day. Either way save the 6550's.

The 6386 tubes have no use in a tube audio amp. They however are rare and are the control VCA in an old audio compressor (Fairchild?) that is worshipped by the vintage tape recording crowd. Sell them on Ebay ($50+ each). The 8417's are a good audio tube for 50+ WPC, but also rare and quite fragile (very close grid to cathode spacing) and subject to early failures. I would sell them to someone who needs them for an old amp.

Big powered tube amps are not cheap, due to the cost of transformers. Use the money from the sale of these tubes to fund the cost of transformers. Several of us here have figured out how to make 100+ WPC for the lowest possible cost. This thread details a 18WPC amp developed by Pete Millett, and modified by me for much more power. TV tubes are used to get big power for minimal $$$$. Read the whole thread if you have a whole lot of time:

http://www.diyaudio.com/forums/tubes-valves/151206-posted-new-p-p-power-amp-design.html

There will be some more higher powered tube amps coming in the future, but nothing is ready just yet.

 

[overtheairbroadcast]

Big powered tube amps are not cheap, due to the cost of transformers. Use the money from the sale of these tubes to fund the cost of transformers. Several of us here have figured out how to make 100+ WPC for the lowest possible cost. This thread details a 18WPC amp developed by Pete Millett, and modified by me for much more power. TV tubes are used to get big power for minimal $$$$. Read the whole thread if you have a whole lot of time:

http://www.diyaudio.com/forums/tubes-valves/151206-posted-new-p-p-power-amp-design.html

There will be some more higher powered tube amps coming in the future, but nothing is ready just yet.

Mr., Tubelab,

That was the amp I was talking about (red board and all). With your mentioning modifications to it, you have really re-sparked that interest in the pmillet TV sweep tube amp and given me a lot of reading to do too to check out your modifications (101 pages worth). Awesome.

 

[Nodric]

Hi Nodric
Love the 'scope clock.
Any link to construction details?
Cheers

How's your German

The circuit was designed by a great guy called Bernhard Thiem. This is his site where you can get the PCB and small components Thiem-Work He speaks fluent English but his site is all German.

If you want the CRT Tube, and the post acceleration board (for the HT Anode) then you can get those from Jan Zuerst also in Germany. His site is in English and he also speaks fluent English if you email him. Ask Jan First ® ; electron tubes and more He also supplies the toroidal transformer for the kit, but you can also get that elsewhere.

Be aware that my CRT is at +1500 VDC at the anode cap, and a PD of 2400 VDC between negative and positive, so it's going to make you dead if you're not very careful and respectful of the power supply. Make sure you have a HV Probe before attempting this build.

The case was made from Walnut (American not UK Walnut) and I was able to use my father in laws milling machine machine to cut the slots for the glass, but a router would work. The brass panel was made by hand and the pots, switches and fuse holders came from Digikey in the US. The glass was cut and polished by a local company for me.

It really is the most pleasing thing to have built.

Total cost was about $500 when everything was factored in, and 100hrs of my time. The case took much longer than the electronics!

 

[Nodric]

Nodric: What's your budget for this project? Do you have any iron? Do you have more than a pair of any output tube candidates?

I can stretch to about $1000 for the iron and discrete components. I can get the chassis CNC cut and chromed for cost through a friend in the family

I am looking at a pair of Hashimoto HC-507u that run about $480 for a pair, so that leaves me some room for a good PT and some Chokes.

The tubes I listed are the ones I have. I do also have a pair of 807s, which I know some have used in high power amps, but I was concerned about the quality of these, and the very high voltage I'd need to use them, plus ugly anode caps

I have a pair of 6AS7G tubes, but I think I'd need four in PP mode if I wanted to try these as I'm not sure if they'll work in SE. I also read they are used in OTL amps, but they seem over complex, unless for a headphone amp, which then seems to be huge tube for just cans use.

I also have a pair of 6011 mercury Tetrode Thyratrons, but I'm sure they're not much use for amps, but would look pretty all glowing in the dark

Arrrgggghhhh, too many options!

 

[Nodric]

The 6550's in an SSE will make about 8 WPC in triode mode, or about 14 WPC. With 88db speakers it will be loud enough for small room listening, but will not shake the house. It's a good project if you want to build a tube amp, and plan to build a bigger one some day. Either way save the 6550's.

Yes I intend to hang onto the 6550s.

The 6386 tubes have no use in a tube audio amp. They however are rare and are the control VCA in an old audio compressor (Fairchild?) that is worshipped by the vintage tape recording crowd. Sell them on Ebay ($50+ each). The 8417's are a good audio tube for 50+ WPC, but also rare and quite fragile (very close grid to cathode spacing) and subject to early failures. I would sell them to someone who needs them for an old amp.

The 6386s will be on evil bay later this week Thanks for the heads up!

I have five of the 8417s and they are good candidates, but your advice about their life concerns me if I need replacements in 10 years time.

Starting to narrow down the field.

Can I use the 5692s in PP class A?

Big powered tube amps are not cheap, due to the cost of transformers. Use the money from the sale of these tubes to fund the cost of transformers. Several of us here have figured out how to make 100+ WPC for the lowest possible cost. This thread details a 18WPC amp developed by Pete Millett, and modified by me for much more power. TV tubes are used to get big power for minimal $$$$. Read the whole thread if you have a whole lot of time:

http://www.diyaudio.com/forums/tubes-valves/151206-posted-new-p-p-power-amp-design.html

There will be some more higher powered tube amps coming in the future, but nothing is ready just yet.

I have some of the tubes mentioned in that thread, so I'm going to have a big cup to tea later and wade through it for education.