Sound King 300B tube guitar amp The Sound King is a super responsive and lively guitar tube amplifier with the natural presence and musical resonance of an acoustic instrument. The pure joy of experiencing the electric guitar in this way is enhanced by an unusual range of clean and distorted sounds. For giving one of the world's favorite instruments its voice, guitar amplifiers deserve a little love too. These amps and speakers are the powerhouses of your audio setup, turning your guitar's output from a simple electric current into those familiar sounds. For easy, go-anywhere amplification, start out with a combo guitar amp.
At around two watts, I've found it needs a bit of preamp gain to play really well on most speakers. That said, the sound here is exceptional. Female vocals in particular are really great with this amp; very much in the room and 'live'. The soundstage is amazing too, and is easily one of the best I have heard. This diminutive little amp that has put several much higher priced pieces of equipment to shame.
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- Jun 29, 2014 Looking pretty good. From a design standpoint 6sl7 and 6sn7's are very different, but from a guitar amp standpoint a 6sn7 will do nicely with those values. Depends on guitar, if I run my amp with 6sn7 and P90's or danelctro pickups it sounds great, if I want to plug a telecaster in I have to swap that sn for an sl.
- Hence, if you intend to use the 5692 as a drop-in for a 6SN7 in an amp running 6SN7 voltages and currents, be prepared to have your 5692 last no longer than a normal 6SN7 at best. Fact 3: By the late 1960s, tube manufacturers were relabelling tubes willy-nilly in an attempt to minimise their losses in what was essentially a dying market.
- The 6SN7EH tube is a beautiful sounding tube, on par with RCA's red base 5692 tube. It maintains a linear response while being able to accept a full voltage. Vintage tube amp users and audiophiles will be thrilled to find that a superior quality, ultra low noise replacement 6SN7 tube finally exists.'
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Posted: 01 Oct 2013, 22:12 |
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Joined: 28 Dec 2010, 22:07
Posts: 352 | Hi all,
I'm proposing an idea so people can comment on it and I can gain some perspective. I may end up building this amplifier.
Audiophiles like 6SN7s. They also seem to like low-power triode amplifiers. The idea here is that, because the power is so low, less amplification has to happen before the speakers are driven. Then the listener relies on super-efficient speakers so the 3 watt amplifier sounds like a 50 watt transistor amplifier driving cheap speakers.
To this end, I am thinking of an amp using a 6U8A pentode/triode that feeds a 6SN7 output stage. The pentode will have a fair amount of gain (much more than the usual triode stage) and accept feedback on the cathode. The triode will directly couple to the pentode amplifier stage and act as a phase splitter. The 6SN7s are a push-pull stage. With 350v on the plates I could probably get 3 watts from the output stage. The triodes would work with fixed bias, allowing for a higher level of output power that possibly hinges on 5 watts per channel. Again, I don't need a lot of power.
Thanks for your input.
Ed
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Posted: 02 Oct 2013, 07:53 |
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Joined: 27 Jun 2011, 10:13
Posts: 146
Location: PA | A 6sn7 can take 500V B+ on the plates with no prolbem. Afther all it was used for a vertical output tube in 1940's TV sets.
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Posted: 02 Oct 2013, 15:48 |
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Joined: 04 Jun 2008, 20:59
Posts: 4285
Location: Arizona, USA | Hi, It would probably work, but my sense is that you will be lucky to get more than 1-2 watts clean out of it. Still a worthy project. For triode based power amp stages I usually figure that they can not really deliver more than about 30% of their max dissipation rating. The 6SN7 (both triodes operating) can only dissipate 7.5 watts. At max output the distortion will typically be about 10%. Backing it down to about 75-80% of max will usually yield a much nicer sounding amp. PP with fixed bias is probably the way to go. I would probably design it with a CCS in the cathodes. Just personal preference. Even then I might put about 5-6 volts on the grids to overcome the minimum voltage needed by the CCS to function best.
Good listening
Bruce
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Posted: 03 Oct 2013, 01:09 |
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Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC | A 6sn7 can take 500V B+ on the plates with no prolbem. Afther all it was used for a vertical output tube in 1940's TV sets. Yep! I use them as drivers for audio amps using transmitter output tubes. Use 600V on one 845 and it's lived three years same set of tubes!
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* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
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Posted: 03 Oct 2013, 17:29 |
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Joined: 27 Jun 2011, 10:13
Posts: 146
Location: PA | I use 6SN7's in my 813 PP amps and have used them in my 211 PP amp with 550 on the paltes and they have lasted for years no prolbem.
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Posted: 05 Oct 2013, 01:41 |
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Joined: 28 Dec 2010, 22:07
Posts: 352 | I'm still working on the design. Here's what I'm thinking..get a 10 watt OPT that's meant for 6V6s and run two 6SN7s per channel in a push-pull parallel set up. That would give roughly the right impedance for the plates, plus the tubes could shove more power. I'd have a 6CG7 to amplify the signal right from the input jack and feed the volume control. This stage would be outside the normal feedback loop and ideally have a low gain, like 5. It would feed the volume control and the 6U8A pentode, which would be inside the feedback loop. For the OPT, I'm thinking something like an Edcor GXPP 10K-8. I don't like putting CCSs in tube amplifiers unless they themselves are made with tubes. It's a big tube world out there and you may do what you like, this is just what I like to do.
Ed
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Posted: 09 Oct 2013, 14:05 |
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Joined: 06 Jun 2008, 18:23
Posts: 5310
Location: Australia |
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Projects: 'Carbon' - MM phono preamp | 180W RAW Class D amp | 'Illusion' - 6SN7 SRPP preamp in a plastic jiffy box | 'Salt Cellar' - Mono 807 triode integrated amp |
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Posted: 09 Oct 2013, 14:13 |
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Joined: 04 Jun 2008, 20:59
Posts: 4285
Location: Arizona, USA | Hi, All pretty much standard except for the 6CG7. Why that particular tube, particularly since they are getting costly. A 12AU7 might be a better choice. 6CG7s make pretty good drivers if you need current, but as a voltage amplifier they may introduce more noise because of the higher idle current needed to stay on the best part of the gain curves.
Good listening
Bruce
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Posted: 09 Oct 2013, 14:48 |
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Joined: 02 Mar 2009, 12:41
Posts: 1111
Location: Vänersborg, Sweden | I think the Firefly is based on 6SN7, but that could be a guitar amp.
Else I have ideas for a 6SN7-SE using parallelled 6SN7s:
http://www.hififorum.nu/forum/topic.asp?TOPIC_ID=89277
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Magnus
'If you don't know where you are going, any road will get you there.'
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Posted: 10 Nov 2013, 03:39 |
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Joined: 28 Dec 2010, 22:07
Posts: 352 | Gents,
In a few months, I should be at a point where I can go forward with this. I don't have a schematic but I can describe it to you. Those of you who know what a push-pull amplifier looks like will have no problem visualizing it. Those of you who don't can look it up.
Stage 1: a triode preamplifier. Most likely a 6N2P or 6922 triode, one per channel.
Stage 2: a volume control. Potentiometer. 100K or 500K, depending on what I have.
Stage 3: a pentode voltage amplifier, accepting negative feedback. A 6U8A
Stage 4: a triode, split-load phase splitter. A 6U8A.
Stage 5: a triode push-pull stage, 6SN7. One entire tube per channel.
For now, I'm intending to use a Hammond 269JX per channel, ensuring I can bias my output stage rather hot and not have any problem with output. The feedback is for the purpose of taking the higher gain and turning it down into something more usable, while removing distortion caused by the tube stages. I also got some 70v 10w line transformers ($3 each) that will be the output transformers. I'll use the 0.625w and common taps to touch the plates and use the 2.5w tap for B+. I'll also double the impedance of the speakers used on the output, meaning I'll get 16K ohms, plate to plate, instead of 8K. The 6SN7 likes higher impedance.
No telling when I'll start this project.
Ed
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Guitar Amp 6sn7 Sound Generator
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