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Blue Bomber SE RH6V6 + 6SL7 amp w/pics

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Posted on February 1, 2015 at 13:40:27
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010



First, thank you Alex Kitic for fearlessly posting the schematics and freely helping me and other DIYers with building and enjoying a great sounding SE amp.
I just completed this RH type 6V6 amp with a 6SL7 driver tube. The chassis is painted a dark blue hammertone paint and the tubes are 5692, 5992, and 6l06/5Y3, which were used in cold war B52 bombers and guided missles for communications and guidance systems, hence the name.
The output transformers are mongo units from Norelco reel to reel SE amps. They are twice as big as the usual EL84 SE OPTs. They also come with solder lugs so its easy to wire in your preference of wire types. I chose Cardas and Kimber for signal and output transformer.
The RH circuit is a combination of the "universal" for the 6SL7 driver and the RH84 v2 for the finals. Power supply is CLCLC mostly because the power trans could not support a LCLC configuration. The capacitors are all Solen 400v film type and 2 x 20uf x 250v Seacor film for the driver supply. The all film cap power should mean that the capacitors will be good for the life of the amp. Resistors are 3/4 watt or more mil spec metal film for accuracy and reliability. Bias to the power tubes is set by the LM317 voltage regulator configured as a CCS.
With less than 20 hours of break in time, and Bendix 5992 power tubes and RCA Red Base 5691 in the driver socket the sound from this amp is dynamic and clean. There is absolutely no hum or other tube noises giving the soundstage a black background from which percussion, instruments, and vocals emerge and erupt in a very convincing manner.
The sound of the 6v6 + 6sl7 amp vs the RHel84 amp is quite similar except perhaps a bit more dynamic. All in all a very satisfactory build. I posted some pics as a tribute and as a sincere thank you to all of those who helped realize this project's goals. cheers, Dak

 

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RE: Blue Bomber SE RH6V6 + 6SL7 amp w/pics, posted on February 1, 2015 at 14:43:42
deathtube 667
 Cool.

I might like to try this circuit.

Do you have the schematic or can you tell me what differs from the
RH84 ver. 2 BOM besides the tubes?

Last, did you get any basic circuit performance measurements?

I saw a few others who tried RH6V6, but sadly no performance data was indicated.

 

RE: Blue Bomber SE RH6V6 + 6SL7 amp w/pics, posted on February 1, 2015 at 15:13:00
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010



The front end circuit is basically from the RH "universal" but I did not make it adjustable so I kept the anode to anode fb resistor at 200K. All other aspects of the circuit is kept as is. The power tube section follows the RHEL84 v2 except you change the pinout of the tube socket for octal tube and 6V6. If you use a tube rectifier you can change the B+ with various rectifiers and use for example a 5ar4 with a 6L6 for about 350v B+ or the 6V6 with a 5y3 and a B+ of about 270v B+. cheers, Dak

 

RE:, posted on February 1, 2015 at 16:00:21
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
 I currently have no means to measure its performance other than my DMM.

 

RE: Blue Bomber SE RH6V6 + 6SL7 amp w/pics, posted on February 2, 2015 at 01:06:14
Alex Kitic
Audiophile

Posts: 182
Location: Serbia
Joined: June 25, 2014
 Thank you for appreciating my work.

Now that you made yourself a nice "mini" RH Universal, you can play tube rolling a little bit.

Besides 6SL7 variations like ECC3x you can also play with 6SN7.

Besides the 6V6, you can use old style low dissipation 6L6 metal envelope and 6L6G ST shape, as well as all sorts of 6F6. The 2 Russian versions of 6L6 with lower dissipation also come to mind.

Enjoy ;)
******

http://rh-amps.blogspot.com/

 

RE: Blue Bomber SE RH6V6 + 6SL7 amp w/pics, posted on February 2, 2015 at 03:31:46
deathtube 667
 Hey, thanks.

I might just keep at the RH84 ver. 2 a bit longer before moving on to something different.

There is the issue of matching the BOM and trying some better OPT, then getting some new performance data on the circuit.

Enjoy your new amp.

 

Measurements, posted on February 2, 2015 at 10:01:22
Triode_Kingdom
Audiophile

Posts: 10047
Location: Central Texas
Joined: September 24, 2006
 You might think about using your PC to make basic measurements. When I hand-pick tubes for my EF86/6V6 SETs, I can cut distortion in half. There's sometimes a huge variation from one tube to the next in this regard, even when they're the same date code.

 

RE:What kind of software do you use to get that info? nt, posted on February 2, 2015 at 10:44:57
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
 .

 

ARTA, posted on February 2, 2015 at 11:20:29
richardl
Audiophile

Posts: 3555
Joined: September 5, 2002
 It will measure distortion etc.

 

+1, posted on February 2, 2015 at 13:19:17
Triode_Kingdom
Audiophile

Posts: 10047
Location: Central Texas
Joined: September 24, 2006
 Yes, and you can probably use whatever sound card is in your PC. You might need some sort of simple resistive interface to protect it from the amplifier's full output. I bought a specific soundcard to do this, but any of them should be good enough to look at vacuum tube-generated distortion.


 

RE: soundcards ...get a good one, posted on February 2, 2015 at 14:04:46
deathtube 667
 The ARTA user manual gives recommendations for PC soundcards to use for best results as indicated with the loopback tests.

DAK needs a good soundcard or the noise floor would be too high to get useful measurements.

I use ESI Juli@ or M Audio 192K, get either one or similar.

IME, run a PC without any anti-virus programs offline if possible.

If you can get a cheap XP box for a measurement PC , do that.

The drivers that come with some of these cards are NOT MS signed and anti-virus programs shut down the card/application as soon as you try to open it.

 

RE: More pics., posted on July 31, 2015 at 11:05:43
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010



Just in case I added this.

 

RE: And this, posted on July 31, 2015 at 11:13:03
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010



Although these photos do not show it the latest iteration of this amp has a "hi-lo" bias switch. This allows a more optimum operating situation when using 6l6 type tubes. I just pop in a 5ar4 rectifier for about a 40v bump in B+ over the 5y3, flip the switch to "hi" and use a 6l6 tube. The switch engages the 18ohm resistor in the bias circuit for a more optimum cathode current. cheers, Dak

 

RE: Blue Bomber SE RH6V6 + 6SL7 amp w/pics, posted on July 31, 2015 at 12:05:42
krankkall
Audiophile

Posts: 296
Location: New Mexico
Joined: April 5, 2014
 Congrats!

I made a similar RH-style 6SL7/6V6 amplifier, a few years back.
I ended up using a 6BY5G TV damper diode, as a rectifier tube.
Best 6V6 tubes in my amp, so far, has been Tung Sol USA black glass.
Best 6SL7 tubes in my amp, so far, has been Ken Rad black plates.

Good luck & have fun!!

Steve

 

RE: And this, posted on July 31, 2015 at 15:53:24
Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014
 Rock on man.

Hope you put a cage on that bad boy!

Fun amp.
△This message will self destruct in 10 seconds△

 

RE: And this, posted on July 31, 2015 at 17:47:15
DAK
Audiophile

Posts: 2712
Location: PACIFIC
Joined: August 8, 2010
 Hi G, I don't need a cage as I have no littl'uns around to get zapped or burnt. It is kinda scary having the B+ for the output trans all exposed as it is. If I use those same trans in another amp I will use some heat shrink on the solder lugs to be a little safer. I actually thought of that right after I soldered up the last wire. Oh well, next time I will catch it. cheers, dak

 

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