tube amp design guys, why no love for 6aq5?

[JonL]

Hi dc, thanks for the insight into the 6AQ5's history. Great first post; welcome to AK!

 

[nichesound]

I bought this little bitty amp that had two 6AQ5 tubes and one little preamp....it was a stupid amp. The person who did this did not have much imagination.

I turned it into a lil monster....added a 10 watt xfmr that is used for school pa systems to push an 8 inch speaker....and added a lot of cool stuff...like a master volume, along with cathode capacitor switches...and the thing is a screamer...here is the layout..I made a schematic and will look for that and post it.... I hope someone will go out and build these for buds like I did ... I gave these to friends for the enjoyment!

 

[dowto1000]

Bump:

Its 2018 now.

Had a friend in 2017 build a 6AV6 directly coupled into a 6AQ5, loaded into a 8K/5K to 8 Ohms SE output. He tried it triode and UL.. Loved its sound. Chose UL.

I have just this past week designed another one, also directly coupled, with 1/2 a 6SL7, as my own next 2018 build. 5U4GB rectifier, L1/C1/L2/C2 filter, below 20 Ohms of series DCR in L1+ L2. 5651 tube-regulated driver stage B+. All film caps throughout. Expect it to perform well. UL.

Dowto1000

 

[dowto1000]

Bump:

Its 2018 now.

Had a friend in 2017 build a 6AV6 directly coupled into a 6AQ5, loaded into a 8K/5K to 8 Ohms SE output. He tried it triode and UL.. Loved its sound. Chose UL.

I have just this past week designed another one, also directly coupled from 1/2 a 6SL7, as my own next 2018 build. 5U4GB rectifier, L1/C1/L2/C2 filter, under 20 Ohms in series DCR from L1+L2. 5651 tube-regulated driver stage B+. All film caps throughout. I expect it to perform well. UL.

Dowto1000

I LIKE the 6AQ5 's sonics !!! Better sounding than MOST Finals tubes, and it easily out-performs any EL-84, 6BQ5 , no contest at all.

General 6AQ5 Direct Coupled amplifier TOPOLOGY :

Note conservative 6AQ5 tube dissipation ( at Golden Ratio...62% of 12 Watts ), wiring details, type and gauges.

Notice please, extremely low series resistances in the amplifier design - of the entire B+ supply.

Designed / implemented, mainly by ear - not a textbook.

Have fun, I sure do.

 

[AdamAnt316]

This is the only 6AQ5 amp I own:

Epiphone EA-33RVT "Galaxie" from the early '60s. I'm not much of a guitar player, but it has very nice tone, plus excellent reverb and tremolo effects. Not in the best shape, and I still have some work to do on it (I get some AC leakage on the input, and the reverb button on the footswitch doesn't seem to have much of an effect), but it's a pretty good amp otherwise. A friend of mine gave me a bunch of 6AQ5s, including some 6005s, so I should be good for awhile.
-Adam

 

[electronjohn]

6AQ5 is one of a number of often-overlooked tubes usable as power amps...6CU5 & 6CW5 come to mind as well. And, although not as inexpensive as some, the 6CL6 can see some output applications as well.

 

[mhardy6647]

Cute little Canadian pp 6AQ5 console amplifier. Not a bad sounding little piece even as found (and the price was right).

PP 6AQ5 console amp 021714 by Mark Hardy, on Flickr

The 6AQ5 was, in essence, a 6V6 in a 7 pin miniature envelope and was fairly commonly used in car radios in the pre-transistor era.


from RCA RC-21 manual, available from Pete Millett's wonderful site www.tubebooks.org

 

[dowto1000]

Car Radio,

a 6AV6, cap-coupled, to a SE 6AQ5 ...........................RCA Manual, dated 11-56.


Dowto1000

 

[dowto1000]

Perhaps the best, most encouraging 6AQ5 comments of all, from Joe Rozen :

https://db.audioasylum.com/mhtml/m.html?forum=set&n=61072&highlight=6aq5+Joe+Rozen&r=&search_url=/cgi/search.mpl?searchtext=&b=AND&topics_only=N&author=energyandair&forum=ALL

Dowto1000

 

[kmolles]

I need to nail down a project using the 6AQ5.....I just check my inventory and I have 120+ of them!

 

[mashaffer]

Hmm... After I finish the RCA Resto-rod I will have to take a look at my Zenith SE 6AQ5.

 

[knockbill]

^
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That's a little 6AQ5 amp in my Avatar. - The 6AQ5s are GEs branded IBM since it sits atop my IBM computer!

I have been considering building an amp with a six-pack of 6AQ5s in each channel, using 4K Shumacher transformers. Should be able to cull a few matched sets from the 300 or so tested ones I have...

I just read this thread,,, if anyone is interested it trying out 6AQ5s,, Toms SE amp (his Audiophool site has/had the schematic)... I built it as my first tube amp scratch build a while ago, and used the the 2 small OPTs from a Moto 3channel amp,,, sounded promising, but lacked some bass... I've since found a pair of Woodward (606) OPTs for a buck at a radio show, and its a brand new animal!!!
Took a bit to sort the FB, but the effort was well worth the ride... 6AQ5s are basically 6V6s with a lower Vp,, and they are dirt cheap!!!!

 

[soundmotor]

I need to nail down a project using the 6AQ5.....I just check my inventory and I have 120+ of them!

Before Danielak published the "Darling" SET amp, 1626 power triodes were on the free table at hamfest & radio swaps. Not any more, 6AQ5 s on its way up too.

 

[dowto1000]

Hello you all,

Besides posting here, I have been VERY focused, last ten days or so, in developing and finalizing a design for a new SE UL 6AQ5 stereo amp.

I have done many design iterations, intensely attacked this project, with PSUD and calculators, and have finally got it down - to where I would like to build a prototype stereo amp. My Direct Couple tube circuit, from a 452.71 VDC simulated B+ supply, nicely balances - out to only 0.31 VDC ( 0.000068477 % ) theoretical, using standard value resistive parts. Way cool.

Amp will use Hammond power supply iron. Three power supply chokes,... DCRs uber low !! , 8 and 11 Ohms.. Stereo amp tube line-up becomes

(1) 5U4GB
(1) 6SL7GT ( 1/2 for each channel )
(2) 5651 ( gas voltage - reference, or regulator tubes )
(2) 6AQ5s

Unlike almost all amps audiophiles have ever experienced, or may see in our audio arts, front end B+ will be fully tube regulated, with a separate 5651 for each 6SL7 triode section. All film caps throughout, every " C " position multiple-bypassed. Also, high current ( 1,500 A. instant peak ) industrial film caps become part of B+ supply - after the tube rectifier, powering the Finals. This new cap-type gets the very leading edge of musical transients, previously always MIA in amps existing today,........ at least - to my own present understanding.

Very conservative tube operating points, 7.45 Watts dissipated from a 12 Watt rated ( maximum ) 6AQ5 anode, gives a high-quality ( relaxed ) sound and many years of trouble-free long tube life. Designed for ALTEC speakers, VOTTs, 604s, etc.

Have fun, I sure do.


Dowto1000

 

[dowto1000]

I just read this thread,,, if anyone is interested it trying out 6AQ5s,, Toms SE amp (his Audiophool site has/had the schematic)... I built it as my first tube amp scratch build a while ago, and used the the 2 small OPTs from a Moto 3channel amp,,, sounded promising, but lacked some bass... I've since found a pair of Woodward (606) OPTs for a buck at a radio show, and its a brand new animal!!!
Took a bit to sort the FB, but the effort was well worth the ride... 6AQ5s are basically 6V6s with a lower Vp,, and they are dirt cheap!!!!

Here is the URL to the above-mentioned Audiophool schematic:

http://audiophool.com/Schem_A/amp.gif

I do not like this above design - at all. Unwanted global Negative Feedback loops, etc etc. Someone can post something far better to copy, I hope.

Dowto1000

 

[dowto1000]

Dt1K,

You should move this to a new thread and keep us updated with the cost of the project as it progresses.

Thanks

Reasonable idea.

It just has been design-developed over the last ten days ( actually ten years ). Cost may be $1,000 or so, as a minimum, in parts. If I went wild with multiple botique film cap bypassing, add $2K more ! DynamiCaps have doubled in price, last several years. Use 6 or 7 in every "C" location, and this adds up quickly !! But ...OHH, what certain values do sonically.


Dowto1000

 

[JonL]

This is the only 6AQ5 amp I own:

Epiphone EA-33RVT "Galaxie" from the early '60s. I'm not much of a guitar player, but it has very nice tone, plus excellent reverb and tremolo effects. Not in the best shape, and I still have some work to do on it (I get some AC leakage on the input, and the reverb button on the footswitch doesn't seem to have much of an effect), but it's a pretty good amp otherwise. A friend of mine gave me a bunch of 6AQ5s, including some 6005s, so I should be good for awhile.
-Adam

I had one of those once upon a time. Forgot all about it. I guess I sold it (foolishly) at some point because I certainly don't have it any more!

 

[Tubeglowpio]

I just read this thread,,, if anyone is interested it trying out 6AQ5s,, Toms SE amp (his Audiophool site has/had the schematic)... I built it as my first tube amp scratch build a while ago, and used the the 2 small OPTs from a Moto 3channel amp,,, sounded promising, but lacked some bass... I've since found a pair of Woodward (606) OPTs for a buck at a radio show, and its a brand new animal!!!
Took a bit to sort the FB, but the effort was well worth the ride... 6AQ5s are basically 6V6s with a lower Vp,, and they are dirt cheap!!!!

I wonder why so many people dislike the 6v6 for hifi, I almost built a 6v6 amp before till I did some searches and most people said the el84 was better and that 6v6 is better left to guitars. Interested to hear more positive experiences with this tube and comparisons to el84's and others.

 

[Pio1980]

I don't dislike them, they do sound good SE and were the reliable workhorse 10WPC P/P sheet beam tube of choice for several years before the world standard EL84/6BQ5 pentode replaced them. The 6V6 replaced the popular 42/6F6 pentode, intro'ed ca 1932/1936.

 

[mhardy6647]

The pp 6V6 Maggotbox console amps sound pretty good to me.
harman/kardon (at least) used 6V6 variants (7408) in some of their "value priced" tube equipment which, again, seems OK to me.