65 Amps - More current, less voltage

[jubal81]

I've been watching the 'Lunch with Dan' videos from 65 amps, which is pretty fun. They're usually about an hour of noodling and talking about amps, gear, etc.
One topic he keeps bringing up is that due to the extremely poor quality of current production tubes, he's designing his amps with lower voltages, but significantly raising the current.
Any thoughts on this?
Here's the latest video. It's a long one, but he discusses this near the beginning.

65amps Lunch with Dan Boul PROTOTYPE and Brian Kehew

[jim]

Just about everyone here on the forum will agree that lower voltages sound better.   Lower voltages dictate higher current to accomplish the same amount of work or power --that is a law of nature. There is nothing new here.   Higher quality modern transformers can deliver the current--this translates into  dynamic range.  The older tranformers would experience voltage sag when current was demanded and produce compression. Compression and reverb in vintage recordings can hide recording and musician's flaws.  As for the current state of tube audio--most, not all,  new production tubes are excellent.  For example, I think it is tough to buy a bad sounding 6L6GC today with all the choices available, but it is easy to get a bum EL-34.  Modern preamp tubes each have their own flavor and are fun to experiment with.  They are still in general much quieter then the old stuff that has been rattling around in boxes for fifty years. Vintage tubes are picked over heavily--the good ones were scooped up long ago and what we have left are always slightly used and sometimes noisey. This video about recording the Beatles is interesting, however, and I think I would like to read the book.   Thanks for sharing it.   Jim

[jubal81]

Sorry, I posted the wrong video. It's fixed now.

The way you explained it is pretty much how I thought it should work. That's why his rationale didn't quite make sense to me.

[John]

The way you explained it is pretty much how I thought it should work. That's why his rationale didn't quite make sense to me.

Meaning no disrespect to 65Amps, but it's called marketing. 

[phsyconoodler]

Marketing for sure!

 He fails to realize that many people know a lot of his amps are EL84 based and the originals he copied(not an insult,just a fact) the 18 watt marshall,already had low voltages and high current.
 Same with a lot of vintage tweed amps.
That being said,one of the best sounding amps I've ever built had 505v on the plates(6L6GC) and low current.
My Rebel Rouser amps.They sounded spectacular at any volume,even dimed where they really kicked ass.
There is a whole lot more to tone than the relationship between voltage and current.

[bnwitt]

Well there are two things we all have and one of them is opinions.  Dan is really a very good fellow.  Of all of the (2nd thing we all have) over at the 18 watt forum, he was not one of them.  I would say that Dan and Graydon were always stellar fellows in that forum even when things got nasty.  But remember, they were diciples of the 18 watt amplifier or they wouldn't have been part of that forum early on.  It was a handful of guys who disected that amp because they were driven by it's tone and that was a lot of work.  So it only stands to reason that they would have to be enamered with the EL84 tubes' distortion characteristics.  To each his own.  I have always thought the 5E3 Tweed Deluxe is the finest sounding little beast anywhere but that is just my opinion.  I can't wait to see how I feel about the orginal AC15 with EF86.   Dan has done a lot of work and R&D on his amplifiers and though I've never played one myself, lots of folks rave about them.  Of course when anyone works hard on a project that comes out well, a little self promotion is understandable.

[phsyconoodler]

I love EL84's but they can be problematic in some builds.The dreaded distortion 'fizz' can happen randomly and I've had it happen in a couple of builds.The Zener diode fix doesn't always work either.I was pissed off until I discovered an output dampener circuit that completely kills the high frequencies responsible for the fizz.
  It just is a series of caps and resistors connecting the plates of the output tubes together.Works every time and better than the Zener fix.IMHO.

 The lower the voltage with EL84's the easier they are to work with.That being said,I built one 18 watt TMB with 420v on the plates and had to compensate with lower screens and a lot of juggling with cathode biasing.
 The result was a killer sounding amp,not better than a regular 18 watt,just different.Very punchy.More like the 20 watt in response.No fizz on that one at all.
 I am thinking the quality and frequency response of the output transformer is the key.
    I don't take anyone's word as the 'last word' on any amp build.I find out for myself,even if by accident.

[jubal81]

I can't wait to see how I feel about the orginal AC15 with EF86.

I bought a Winfield Cyclone earlier this year and it really sounds great. It's AC15 style (EF86 + el84), but I haven't opened it up yet to investigate.

There aren't any 65 amps down here, so I've never heard one in person. I love the way they sound on Dan's show, but it's just internet video. After thinking about it some more, I think he's talking more about transformer design than circuit design. More or less: "Oversized power transformers sound better."

[cbass]

I don't know anything about 65 amps but it looked like had a Mizzou shirt on.So he must be pretty bad ass.

[Willabe]

I don't know anything about 65 amps but it looked like had a Mizzou shirt on.So he must be pretty bad ass.

             

[Quatro]

I was pissed off until I discovered an output dampener circuit that completely kills the high frequencies responsible for the fizz.
  It just is a series of caps and resistors connecting the plates of the output tubes together.Works every time and better than the Zener fix.IMHO.

can you elaborate on this please?

Thanks

[HotBluePlates]

I was pissed off until I discovered an output dampener circuit that completely kills the high frequencies responsible for the fizz.
  It just is a series of caps and resistors connecting the plates of the output tubes together.

can you elaborate on this please?

RCA called it a "corrective filter" in the front matter of most of their receiving tube manuals; Dr Z uses it and refers to it as a conjunctive filter in interviews. Search the forum for either of those terms for a more complete discussion.

Bottom line: rather than feedback around the output stage, a corrective filter is applied across the output transformer primary (from one push-pull plate to the other) and consists of a resistor in series with a cap. The primary impedance reflected from the speaker rises with increasing frequency, because the speaker's impedance rises with increasing frequency. The filter's impedance decreases with increasing frequency, so the correct resistor/cap combination can make the output transformer primary impedance appear near-constant. That can reduce increased apparent treble output due to the rising impedance.

RCA suggests values for the resistor and cap: R is recommended as 1.3 times the plate-to-plate impedance of the primary. C should be a value that provides the same output at 400Hz and 1kHz (as tested by applying a signal to output tubes and measuring output voltage at the speaker). RCA continues to say the value is often near 0.05uF.

You can try any values you like and check their effect. Be sure to use a cap rated more than double the B+ voltage (so you'll generally need a 1kV or better voltage rating).

[Katie 77]

yea, the WEM Dominator (reputed origin of the Marshall 18W) and ER15 had 4.7k/.002uF across primaries (to CT)...but a couple later (mid 60s) WEMs I had in the shop used 4.7k/.01uF!
Better sounding amps than the 18W IMO....maybe because of the filters...

Re: 65Amps.....I know Dan personally, and did the schematics & layout designs for his London when he got started (don't ask me any tech questions, I signed an NDA). There's no question that he's a saleman. I like him, but tire of the gaming.
But the whole 'high current/low voltage' is not a new thing...look at a lot of old low power hifi sch using 6L6s or EL34s. In fact....look at Mullard EL34 datasheet...there are design specs for 2xEL34 cathode bias w/ 375V and 75mA per tube! Drop B+ to ~ 300V....and you'd just about have your '22W lowV/hiI' guitar amp.
Incidently, to my ears, lower B+ (~230VDC) on preamps tubes 'sounds' warmer and smoother, too.
Dan also has Sergio Hamernik as part of his brain trust...and if you go to the MM 'Talkin Tone with Sergio' link...you'll find some interesting 'clues'.

Also have to add, he does not use your typical OT specs. It's in the 'clues' at MM.

[bnwitt]

Dan also has Sergio Hamernik (at MM) as part of his brain trust...

Well now that makes perfect sense.  Talk about BS marketing, Sergio is the king of same.  I have done several side by side comparisons of exact amp builds with Heyboer and Mercury Magnetics tranny sets and never found there to be a sonic difference that warranted the rediculous prices Mercury Magnetics charges.  I mean think about it really, if the holy grail amps of yesterday were built with the cheapest trannies money could buy, then why do we need trannies now that cost 400% more than the the others on today's market in order to get great tone?  That's counter intuitive to logic.  

As I said, I think Dan is a nice guy.  Do I think his boutique amp is worth $2,900.  Yes I do.  Do I think my builds are worth that?  Yes I do.  Can I get $2,900 for one of my hand wired amps?  No I can't.  Not without making some famous recording artist's guitarist my partner and talking a bunch of Mojo BS until I'm blue in the face.  Sadly, I'm too darned honest to do that and I find it tiring as well.  Americans have lost the knowledge that "You get what you pay for."  That's why everything comes from Asia and is disposable these days.  It's funny that we blame politicians for sending manufacturing jobs overseas when it is truly our purchasing habits that have done this.  I noticed a long time ago that Doug Hoffman stopped building amplifiers for sale.  Of all people in the tube community he is one fo the gurus out there.  I do believe he figured out what took me a little longer.  If you want to make a million bucks in the boutique amp business, start with two million.

And I don't need any clues on 65 Amps build methods, schematics or layouts.  The good old standby holy grail amp circuits of yesterday that made some of the finest recordings of Rock and Roll sound incredible to me and they are freely available to everyone.  One amp does not fit all any way.  This is why I stopped searching for the "one amp" long ago.  I am currently building (5 ) amps at the moment for my studio.  I might add (1) or (2) more later but I'll never be buying a one size fits all unit because it doesn't exist.  I will have several one trick ponies.

[Katie 77]

Dan also has Sergio Hamernik (at MM) as part of his brain trust...

Well now that makes perfect sense.  Talk about BS marketing, Sergio is the king of same.  I have done several side by side comparisons of exact amp builds with Heyboer and Mercury Magnetics tranny sets and never found there to be a sonic difference that warranted the rediculous prices Mercury Magnetics charges.  I mean think about it really, if the holy grail amps of yesterday were built with the cheapest trannies money could buy, then why do we need trannies now that cost 400% more than the the others on today's market in order to get great tone?  That's counter intuitive to logic.  

As I said, I think Dan is a nice guy.  Do I think his boutique amp is worth $2,900.  Yes I do.  Do I think my builds are worth that?  Yes I do.  Can I get $2,900 for one of my hand wired amps?  No I can't.  Not without making some famous recording artist's guitarist my partner and talking a bunch of Mojo BS until I'm blue in the face.  Sadly, I'm too darned honest to do that and I find it tiring as well.  Americans have lost the knowledge that "You get what you pay for."  That's why everything comes from Asia and is disposable these days.  It's funny that we blame politicians for sending manufacturing jobs overseas when it is truly our purchasing habits that have done this.  I noticed a long time ago that Doug Hoffman stopped building amplifiers for sale.  Of all people in the tube community he is one fo the gurus out there.  I do believe he figured out what took me a little longer.  If you want to make a million bucks in the boutique amp business, start with two million.

And I don't need any clues on 65 Amps build methods, schematics or layouts.  The good old standby holy grail amp circuits of yesterday that made some of the finest recordings of Rock and Roll sound incredible to me and they are freely available to everyone.  One amp does not fit all any way.  This is why I stopped searching for the "one amp" long ago.  I am currently building (5 ) amps at the moment for my studio.  I might add (1) or (2) more later but I'll never be buying a one size fits all unit because it doesn't exist.  I will have several one trick ponies.

I have to agree w/ all of the above...and w/ what I knew about Dan's amps...I didn't build one....not my cup o' tea. I like the old standards. MM is way overrated (and ridiculously overpriced) IMO.

[Fresh_Start]

Slightly off topic but all you need as proof that Mercury Magnetics relies on marketing b.s. is their "volume discount" pricing and their obvious ad buys in Vintage Guitar.

Anecdotally, I built two virtually identical Princeton Reverbs.  Same cabs, speakers, caps, tubes, etc.  One with Mercury Magnetics iron my friend insisted on and the other with Doug's iron.  If I heard any difference at all, Doug's sounded a tiny bit better.  Sweeter high end and cleaner bottom.

Cheers,

Chip

[alerich]

I have finally found my own personal holy grail high gain amp. It's a Sovtek Mig 60 that was modded by Scott Splawn of Splawn amplifiers (back when he was still doing the modding thing back in the late nineties). It runs a pair of Tung Sol EL34B tubes at 640 VDC on the plates. Sounds incredible and has a tremendous amount of grunt. While I'm sure that not every current production EL34 is up to the task the Tung Sol doesn't seem to mind much. Despite what the fellas in the video might think there are some current production tubes that are quite robust and well built just as there is a lot of NOS glass being hustled every day that is junk.

[bnwitt]

Well now you're going to have to share those mods Alerich

[fuzz]

As I said, I think Dan is a nice guy.  Do I think his boutique amp is worth $2,900.  Yes I do.  Do I think my builds are worth that?  Yes I do.  Can I get $2,900 for one of my hand wired amps?  No I can't.  Not without making some famous recording artist's guitarist my partner and talking a bunch of Mojo BS until I'm blue in the face.  Sadly, I'm too darned honest to do that and I find it tiring as well

I think that having his friend Peter Stroud on board helped him to get all the producers and studio (or not) musicians ending with 65 amps. I might be wrong but he seems to be a honest guy too but he has to make his living with this compagny so the price can't be the same that for an amp built for pleasure in your garage .

What I find really intersting in 65 amps is that he "created" something new with a strong image, not based on old tired  marshall , fender , vox designs that everyone copied and still copy . And just for that I think it worth looking deeper into his amps . Devil is in the detail as I read somewhere. He seems to put a lot of thoughts and reflexions in his amps. 

 But  I've never seen a 65 amps myself (pretty rare on this continent) to be sure they're original designs as he says . I've of course gut pics (as all of you  ) but that's not enough to see the truth !  .

For the conjunctive filter that's not the first time I read about that . Isn't it taken  form Hi-fi circuit ?

[HotBluePlates]

For the conjunctive filter that's not the first time I read about that . Isn't it taken  form Hi-fi circuit ?

Maybe the best way to say it is "old tube audio practice". May or may not be related to "hi-fi" and likely predates the use of feedback.

[alerich]

Maybe the best way to say it is "old tube audio practice". May or may not be related to "hi-fi" and likely predates the use of feedback.

The much revered Hammond AO-35 reverb amp used a conjunctive filter on the OT... and it was discontinued in 1964. It's very old school technology. I have not tried it. It's supposed to even out the volume of each frequency so long as the pick attack remains constant.

[bnwitt]

As I said, I think Dan is a nice guy.  Do I think his boutique amp is worth $2,900.  Yes I do.  Do I think my builds are worth that?  Yes I do.  Can I get $2,900 for one of my hand wired amps?  No I can't.  Not without making some famous recording artist's guitarist my partner and talking a bunch of Mojo BS until I'm blue in the face.  Sadly, I'm too darned honest to do that and I find it tiring as well

.....so the price can't be the same ... (as) for an amp built for pleasure in your garage .

Well I have built a buttload amps (over 30 5E3 clones alone) and only the first one was built in my kitchen cause it was close to the beer.  I've had a full blown electronics shop since I was a teenager (and that was the 70s) so I'd say I'm capable of building as good of an amp and even better than 65 Amps.  65 amps doesn't have Merlin working for them I'm sure.

The point is of course that if you want to sell a well designed quality hand wired boutique amp for what it is worth, you have to commit yourself to a huge marketing expense and effort.  That effort requires "Mojo" bullshitting to get folks to want to spend the kind of money that makes the amp profitable and giving away some free amps to name players.  I was asked to give away 2 of my 80 watt SRV vibroverb amps (of which I had one on display for Jensen Speakers during NAMM 2004) to John Fogerty by his equipment manager.  I wasn't prepared to give away almost $4,000 in parts and a lot of labor for 2 amps on a maybe he'll endorse it deal and frankly, I have a pretty good day job with no risk so I passed.  My hat's off to Dan.  He is a hell of a marketing guru.  I couldn't sell fur coats to Eskimos.

[John]

The point is of course that if you want to sell a well designed quality hand wired boutique amp for what it is worth, you have to commit yourself to a huge marketing expense and effort.  That effort requires "Mojo" bullshitting to get folks to want to spend the kind of money that makes the amp profitable and giving away some free amps to name players.

And that is a very good point. A simple browse through a couple guitar and/or amp forums shows the "mojo" mentality that is out there. (It runs in pure tube Class A!!) And marketing in any form, even if just doing the interview thing, show thing etc. gets expensive in time and money.

[SILVERGUN]

Jubal81, back to your original post....
There is a huge range of available volt/amp curves that are useful in building tube amps, and the most important thing to consider is "what are you trying to accomplish?"
There is always a bit of marketing bs involved in any new gear that people are trying to sell you, but there is also a ton of research by guys who have been tweaking these circuits for years, and all you can do is pickup bits and pieces of the puzzle from guys who REALLY know what they are talking about. I'm not one of those guys, but I can tell you this much:

The electrical equation that you can relate to this topic is this simple: voltage X amperage(current) = wattage

Here's an example as it relates to an amplifiers power section:
If you are using lower voltages in your amps power tubes then you must use higher current (monitored and controlled by biasing---a measurement of idle current) in order to produce a specified output (wattage)
OR, you could reduce the output of a given amp by reducing the "current" through the output tubes...(this would be accomplished by biasing the tubes cold, which reduces the current passing through the output tubes, which in turn decreases their output)
Again, there is a wide range of useable specs to help you accomplish a specific goal (headroom, saturation, tube life, etc.), and all you can do is follow the yellow brick road that has been laid out by the masters that have existed here before us........they all do it a little differently and thats how we get 100 amps that all sound different.

I hope that helped more than it hurt.

[Mars-Hall]

I use "new production" tubes in all my vintage amps and otherwise.  The only reliability issues, have all been related to problems with the amp, not the tubes. 

[Katie 77]

I use "new production" tubes in all my vintage amps and otherwise.  The only reliability issues, have all been related to problems with the amp, not the tubes. 

+1
I have customers using new Shugang EL34Bs in their Laney Klipps, w/ no problems (over two years gigging w/ them!). If there is going to be any tube failures...that amp will do it. It's the only EL34 I use and it sounds good (I think circuits have more impact on overall tone anyway).
I don't doubt that there will be the odd failure here and there....but not as often as they make it out to be (fear tactics). I don't care for JJs, but their 6V6 (looks like a 6l6 LOL) takes it and likes it.

[bnwitt]

I have to say Winged C EL84s and 6L6s are just awesome.  They last forever and sound fantastic.  One of my customers brought in his Peavy 100 watt amp the other day saying it had gotten quiet.  He had bought a complete EH tube set online to put in it.  I had installed a matched set of Winged C 6L6s 2 years ago.  I told him "lets test the tubes before we swap them out.  The Winged C 6L6s were still strong and still matched within 3%.  It was only a bad 12AX7 tube.  Changed the one bad tube and sent him on his way with some EH backup tubes.  This fellow plays in two bands 3 gigs a week.  That is a lot of hours on those Winged Cs in 2 years.