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Some times less is more ........

71.30.108.24
Posted on September 15, 2014 at 10:52:14
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013



Don't let all the clip leads fool you; the front end shown in the photo above is comprised of only one 6bq5 in triode mode per channel, three resistors per channel and one cap per channel if you don't count the filament resistors. It doesn't have driver tubes because it depends on the line stage to drive it. The psu is seen in the background, but even it could be smaller if I used modern filter caps. I just used what I had on hand to bread-board it.

It sounds great and it is 2 watts per channel with one 6bq5. If you need more watts the second page of the link below shows how to daisy chain up to 5 of them for up to 10 watts.

I have not a/b tested it against my true SE triode amps yet, but from what I have heard so far I think it will give them a run for their money. I think one of the reasons it sounds so good is that there is so little extra stuff in the signal path. The KISS principle at it's best.

If any one is looking for an easy to build, inexpensive, great sounding tube amp you might want to read through the article that is linked below.

 

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Agree, posted on September 15, 2014 at 12:08:54
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 As I have gotten older, I have gone to a simpler and simpler system.

Used to have a SEVEN-way Fulton P-22 Premiere system, which took large amps to drive. Now, I have gone "back" to using two-way efficient speakers, much like the ALTEC 604B my Dad installed in our home when I was eight years old.

The big joy today is that I can use a one to three Watt amplifiers on these sensitive speakers, which allows for SET amps. With such amps, I am enamored with the simplest practical circuit I can implement, my favorite being two stage, and direct coupled.

Have fun in your audio journey. Try a 6AQ5 triode connected, instead of a 6BQ5.

Jeff Medwin

 

RE: Agree, posted on September 15, 2014 at 12:14:11
bcguitar
Audiophile

Posts: 1328
Location: Maryland
Joined: March 2, 2005
 I keep thinking about a Marantz 9 like amp using 6AQ5 in triode, or even just a pp 6AQ5 triode amp. My Fisher 20As sound amazing with all the mods but I don't need the power with 103db speakers.....

 

RE: Agree, posted on September 15, 2014 at 14:05:20
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 I'll have to see if I have any of those in my stash.

 

RE: Some times less is more ........, posted on September 15, 2014 at 14:37:34
Lee of Omaha
Dealer

Posts: 1800
Location: Omaha NE
Joined: September 8, 2006
 My own prejudice is toward simple topologies. They are a heck of a lot easier to get good-sounding than complex architectures, but let's not forget McIntosh--complex topology, fantastic sound.

I think maybe most of us can design simple amps that sound good, but it takes a Frank McIntosh to make complex work.

 

Or a Tim de Paravacini nc, posted on September 15, 2014 at 16:17:28
mobiasloop
Audiophile

Posts: 100
Location: SW Missouri
Joined: August 14, 2014
 nc
"...the fool doth think he is wise but the wise man knows himself to be nothing but a fool." Will Shakespeare

 

RE: Some times less is more ........, posted on September 15, 2014 at 18:01:04
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Never heard a tube mac, only solid state, and I wasn't too impressed with that. I do believe in KISS though.

 

RE: Some times less is more ........, posted on September 16, 2014 at 07:15:09
electrovice
 The schematic does not give a value for the grid resistor. Is there a preferred value?

John

 

RE: Some times less is more ........, posted on September 16, 2014 at 08:16:26
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 I wondered about that too. I made a WAG that he used 47k for both those resistors as they are tied together, and just used the one label. It worked fine as I could tell, but maybe someone else can tell us both what it really should be? Better still would be if someone could explain how we could calculate it so we can learn something to boot.

 

RE: Agree, posted on September 16, 2014 at 08:19:29
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 If your speakers aRE REALLY 103 db, you do not need to listen to push pull at all. A single 6AQ5, Type 45, 2A3, etc., with a good implementation, will easily, easily power that speaker and sound superior to any Marantz 9 out there. I owned M-9s, rack mount, and can speak from experience.

Email me privately and I'll be pleased to send you amp building ideas to consider .

Jeff Medwin

 

RE: Agree, posted on September 16, 2014 at 09:45:47
Al Noakes
 If your speakers are 103dB sensitive then what you should try is a 6E5P spud amp :)

Al

 

RE: Some times less is more ........, posted on September 16, 2014 at 10:08:19
sonicboom
Audiophile

Posts: 81
Joined: June 10, 2003
 It's usual for the grid stopper to fall in the 100 to 1000 Ohm range when used on tubes that tend to oscillate in the very high frequencies. I don't know if the EL84 has such tendencies. If not, then you could possibly omit the grid stopper. Alternatively, grid stoppers in the range of 10K to 50K are used for dc blocking purposes and is seen mostly in guitar amps where things are often overdriven.

 

RE: Some times less is more ........, posted on September 18, 2014 at 14:10:40
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Went and did a little research and that is a grid stop resistor and the 47k I used is too high. Suggested values are 1k or less. I will give that a try and see if it makes any difference.

 

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