Tubeglowpio
Active Member
This is what I've heard from most, I think they were in some old jukeboxes too and some people say they have a very tubey classic sound but a bit muddy compared to an el84.
tube amp design guys, why no love for 6aq5?
- Thread starter ke4mcl
- Start date
Tubeglowpio
Active Member
The Maggie one is pretty common and people seem to prefer the 6bq5 versions over it, which made believe this even more. I'm sure I'll build one to see for myself someday.
6AQ5?
My fat fingers have a difficult time with 9 pin tubes, 7 pins are like 20% smaller. That could be the reason along with failing eyesight.
Love the thread...
Co-incidentally, I just finished the 6AQ5 SE amp. The plan was to build a tube headphone amp. I did not like the UL configuration, and switched first to pentode, and then to triode. So far, I like the sound of the triode the most, and that's how I assembled it for now. Still need to add headphone jacks and the switch (speakers/headphones) I hope to take some measurements this weekend that I will be happy to share. For now, just a couple of quick pix...
Cheers, Paul
PS. There are a couple of great threads going on here, and the projects could easily use the 6AQ5...
BuzzK's thread on the evolution of the headphone amp
DC-coupled RH84 amp discussion by Tubeglowpio and Dowto1000
Co-incidentally, I just finished the 6AQ5 SE amp. The plan was to build a tube headphone amp. I did not like the UL configuration, and switched first to pentode, and then to triode. So far, I like the sound of the triode the most, and that's how I assembled it for now. Still need to add headphone jacks and the switch (speakers/headphones) I hope to take some measurements this weekend that I will be happy to share. For now, just a couple of quick pix...
Cheers, Paul
PS. There are a couple of great threads going on here, and the projects could easily use the 6AQ5...
BuzzK's thread on the evolution of the headphone amp
DC-coupled RH84 amp discussion by Tubeglowpio and Dowto1000
dowto1000
BANNED
Nice post, appreciated. It appears that your chassis choice is far too small, a common mistake, as the various fields will interact too much.
Here is a ROUGH idea of how I will lay out the prototype 6AQ5 stereo DC SE UL amp.
Its on a previously used 14 gauge steel, welded corner chassis, powder coated Midnight Blue Wrinkle. The big 2 inch washers reduce the tube socket hole - already punched, from Octal to Seven Pin size, and are to be positioned below deck, to be painted satin black.
Regarding fields, see how distanced the Power Transformer and 5U4GB rectifier tube is from the audio stages?
Those two empty holes ( in front of the six audio tubes ) will be for RCA input jacks, with a SHORT wire run ( about 2 inches ) to the grid of the 6SL7 input tubes.
Dowto1000
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I found mine recently at a local electronics store for a pretty good price. Had the usual hum issue, which some new filter capacitors fixed (was interesting putting them in, since the originals were cardboard cans with wires sticking out, but I pulled it off). Just need to solve the AC leakage issue on the input, as well as figure out why the reverb footswitch doesn't have much effect (turning the reverb knob affects its level, but the switch button itself doesn't seem to turn the reverb on or off), and it should be all set. Oh, and learn how to play guitar.
-Adam
cableguy
In Twang We Trust
wa2ise
Super Member
I usually don't bypass the SE output tube's cathode. Unbypassed cathodes will provide some negative feedback immediately (within microseconds) to the output stage. At the cost of less stage gain.
dowto1000
BANNED
To bypass or not to bypass cathode resistors - Rks, that you have brought up, might be a whole other discussion .
By the way, I have found it is very expensive to all-film bypass an Rk " right ", ideally, in a good SE amp !!! This schematic we discuss has both Rks bypassed with capacitors, and most likely cheap / ugly-sounding electrolytics.
I was mainly objecting to the negative feedback applied, a loop. It is fed-back from the 8 ohm Output Transformer's secondary tap, to the Cathode of the Input tube. As such, this mediocre circuit has a totally out-of-time signal being superimposed upon to the incoming new input signal.
LOL, other design problems :
the 100K ( input ) pot is several times too low for a 12AX7
and the 4.7K grid stopper is not good either IMHO.
No grid stopper in the signal path is better - assuming all else has a decent execution and design. Does it ?????
Enjoyed reading your comments.
Dowto1000
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dowto1000
BANNED
The most experienced and best listeners will tell you, the 6AQ5 is far superior sonically to any 6BQ5 / EL84 !!! Just don't use high power dissipations on the 6AQ5's plate ...quality, not quantity prevails. The 6AQ5 tube deserves a good circuit in my opinion. Two stage, direct coupled, all film caps, tube rectification, low DCR, zero negative feedback. Coming up.... soon !!
Dowto1000
If this truly were the case, I suspect there would be significantly more amps designed around the 6AQ5 rather than the 6BQ5. This might be your impression from your listening but where is the evidence to substantiate this?
They are reasons that these members have cited and so are valid for this discussion and might be important for the OP. No doubt the 6AQ5 can sound great, as can many types of tubes. By all means express your enthusiasm but respect the inputs and values of others.
dowto1000
BANNED
Please re-read their reasons. The 6AQ5 sounds better in a SE amp, than 99% of the tubes one can pick. There are only THREE tubes, for Finals, I would use in a SE amp.
Dowto1000
Evidence you ask ??
ON Audio Asylum, a few decades ago, respected listener, the late Joe Rozen posted this " The worst 6AQ5 will sound better than the best 6BQ5 ". People on this Forum have commented on how GOOD a 6AQ5 can sound.
I really don't care what the consensus does. We are stuck with SE amps that - almost all - sound poor to me, following the consensus. Tuners , not amplifiers - not honest.
There are a FEW people who are great listeners, who have compared optimized versions of amps using both tube types, and the 6BQ5 comes in second best.
I think I can build a 6AQ5 SE UL amp that will easily out-perform every DHT Type 45 amp EVER made, except for a few good ones using EML Type 45s !! I will soon know, the 6AQ5 amp's design was done, computed by me this month, need to build it. We shall see, or...hear !!!
Dowto1000
Out of billions of humans one data point opinion does not provide evidence. Opinions vary. Unidentified "People on this forum" commenting on something sounding good does not mean that it is better, best or whatever.
You have your opinion only and are welcome to that but there is no explicit data to back up this claim. Again, the opinions of others are valid and are to be respected but do not substantiate sweeping claims.
By all means please do start your own thread to cover the 6AQ5 SE amp.
knockbill
Lunatic Member
Sorry you don't approve of this design,,, I built it pretty close to Tom's schem and find it to sound pretty good for its simplicity... Seems you are comparing it to a $1K+ design,,, my cigar box version cost less than 10 bux to build...
dowto1000
BANNED
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Hello,
People can certainly say what they want.
Allow me to review the gist of 65, 67 and 68.
Posts 65 and 67 are the same person, commenting on not liking 7 Pin tubes in general ( 65 ) and even a 9 Pin tube is " tippy ". The poster states in 67 he has " no feelings about the tube ".
Poster in 68 says his fingers are fat and he has failing eyesight.
Yes, people can and should be able to say such things. I agree. Fine with me, and you. Give them room to post what they want !! What they posted, however, has " little or nothing " to do with the performance of the 6AQ5 tube. The title of this thread is " tube amp design guys why no love for a 6AQ5. "
Well, I happen to be a tube amp design guy. ( 'Have been since about 1983.) I am talking about a 6AQ5's performance, when optimized, in this thread.
I have designed and built from-scratch two different direct-coupled SE amps using a 6AQ5 in the past . Unlike the thread's title, however, I happen to LOVE the sound of a 6AQ5 when well-implemented. I wanted to express myself, and tell others, of my positive experiences, herein, and how good this tube can sound.
I don't think I need to begin a new thread, to be able to discuss a 6AQ5, in this thread.
On a planned new ( third ) 6AQ5 SE build, after I order parts, and start on construction, I will do a separate thread, to show how I modify parts, etc., and go about my SE builds. ' Also hope to display the upcoming build, via photos. Its fun to share such stuff. People like seeing that.
Most statements I make are ONLY my own opinions, but, it comes from direct experience - from the actual self - designing and building, of P-P and SE amps.
Dowto1000
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