New Directions at Modwright!!!

0 Members and 1 Guest are viewing this topic. Read 13995 times.

Tyson

Re: New Directions at Modwright!!!
« Reply #40 on: 11 Sep 2018, 10:21 pm »
I think an EL84 tube amp is a fantastic idea - it's a seriously overlooked tube and it sounds great.  The world already has enough EL34/KT66/KT88/6550 amps.

Especially if you could arrange the quads of tubes in a cool pattern or otherwise give it some visual flair, it'd be a hit.

modwright

Re: New Directions at Modwright!!!
« Reply #41 on: 11 Sep 2018, 11:29 pm »
Thanks,  I always like to make our gear look good! I was thinking of a dark grey to black powder coated enclosure with some texture perhaps with the transformer belends powder coated Illusion Malbec, which is a deep burgundy wine color. Silver or black knobs, not sure. Flat black if gloss chassis or gloss knobs if flat chassis. And yes, the tubes arranged in a visually pleasing way.

I am still waiting to hear how Jack makes out with the transformer design for four P-P parallel EL84's.

I appreciate your FB!

Dan

Rusty Jefferson

  • Full Member
  • Posts: 416
Re: New Directions at Modwright!!!
« Reply #42 on: 12 Sep 2018, 03:05 am »
...... I hesitate however, because everyone seems to get a bored look on their face when I mention the EL34 tube.

I also thought about a P-P 300B integrated, at about 25W.

If anyone has an opinion about the tube integrated design and tube choice, please let me know. I believe there is a market for a GOOD, reasonably priced, 25W-30W Class A tube integrated that sounds better than the current offerings on the market.

Thanks,

Dan
I do understand why folks give you the blank stare when you mention the el-34 p-p amp. I feel like I've heard hundreds.  Same for the p-p 6550 family. Many fine amplifiers in there, though.

I like the idea of the p-p 300b amp, except I'd have to get a quad of the new/reissued WE tubes. Unfortunately for me, if there are quality tubes available for my gear I use them, because they sound so much better. And it's also challenging to get both great bottom end and top end with the 300b.

One potential I'd like to see is a p-p 845 integrated.  That would get you 50 watts per channel, and I'd find that more enticing than another 30 watt integrated.  And NOS tubes are not realistically available to 99% of us. I wouldn't even consider it.

Tyson

Re: New Directions at Modwright!!!
« Reply #43 on: 12 Sep 2018, 05:07 pm »
Thanks,  I always like to make our gear look good! I was thinking of a dark grey to black powder coated enclosure with some texture perhaps with the transformer belends powder coated Illusion Malbec, which is a deep burgundy wine color. Silver or black knobs, not sure. Flat black if gloss chassis or gloss knobs if flat chassis. And yes, the tubes arranged in a visually pleasing way.

I am still waiting to hear how Jack makes out with the transformer design for four P-P parallel EL84's.

I appreciate your FB!

Dan

Plus the Gold Lion EL84 is a pretty nice looking tube (and sounds great too), and only $50 per matched pair:


modwright

Re: New Directions at Modwright!!!
« Reply #44 on: 12 Sep 2018, 05:22 pm »
Agreed, the EL84 is not expensive and can be readily sourced new at least, without breaking the bank.

In that same frame of reference, NOS EL34's, 300B's or 845's are going to cost a FORTUNE! I don't know that tube cost is really a relevant factor in this case. Or if so, then the EL84 is about the least costly of the bunch. The 300B and 845's new are among the most expensive. Even at four tubes total for 300B or 845, it would still be less costly to re-tube an 8-tube EL84 amp.

Now if the goal is to get closer to 50W, then the choices shift to 845, KT88, KT120, KT150.

Dan

modwright

Re: New Directions at Modwright!!!
« Reply #45 on: 12 Sep 2018, 05:24 pm »
The 845 P-P is another idea. The only drawback to using the 845 is the nominal/ideal 1200V operating voltage.  Even 800V-1000V is still lethal and a bit unnerving to work with. The rest of the tubes we are discussing are operating in the 300V-500V range.  That is a dangerous voltage, and it hurts when you slip up and get zapped, but it won't end your life.... We did one pair of 845 SE mono blocks and they were build to operate at 1200V. At that voltage, I had to take into consideration the wire insulation, proximity of any conductors with respect to anything carrying that voltage and even that all solder joints and connections had no sharp points or edges. At 1200V, a sharp point on a solder joint will cause a focused charge that will actually glow magenta as the air is ionized and turned to plasma.

We were able to achieve 32W with a single 845 in Class A2, pure SE. If we ran a pair on P-P Class A and ran the plates at closer to 800V, we could probably still comfortably get 40W-50W.  I would have to see.

I LOVE the sound of SE 845's! The 845DS mono blocks that we built (90lb each!) are the most magical amps I have ever heard! They have a quality that is simply unique. We used a single gain stage (6HV5 tube - capable of 3KV plate voltage), cap coupled to an 845 tube transformer coupled as SET. The circuit is so simple and elegant!

I will consider this. I  know that Line Magnetic has achieved success with amps in the $4K-$5K and similar power, using 845's. Being made in China is the only way that they can reach this price. I could probably come close, made in the U.S., factory direct, depending on the cost of the enclosure.

Thanks,

Dan

Rusty Jefferson

  • Full Member
  • Posts: 416
Re: New Directions at Modwright!!!
« Reply #46 on: 12 Sep 2018, 06:29 pm »
I agree that there is something magical about well implemented 845 amps. I'm sure your custom made monos are awesome.

Good luck with the el-84 integrated, and apologies for getting off topic.


Tyson

Re: New Directions at Modwright!!!
« Reply #47 on: 12 Sep 2018, 06:56 pm »
Dan, have you ever considered doing Single Ended Parallel only and not do the Push-Pull?  I've not heard one, but they are supposed to keep the magic of true SET sound while giving you more power. 

modwright

Re: New Directions at Modwright!!!
« Reply #48 on: 12 Sep 2018, 07:21 pm »
We already have the A30 mono blocks, which use 3 x EL34 per channel in SE parallel to produce 30W of power. Because this is SE and pure Class A, the transformers are heavy, about 15lb each and as a result, the amps are mono blocks.  Each amp weighs about 48lb with just two transformers and a single choke.

When it comes to SE power, 30W iron will be the same size, pretty much no matter what tube is used. P-P allows for smaller output transformers to achieve the same power. I also agree that most P-P amps that I have heard do NOT sound as good as just about any SE amp, whether SET or pentode tube.  However, due to the unique winding configuration of Jack's output transformers - borrowing from technology perfected in development of the A30 mono blocks - the sound is still VERY sweet and musical. It does not have the cold, hard or even diffuse sound of most P-P amps.

In my opinion, it is the use of gross amounts of Global feedback in most P-P tube amps that causes this.  First of all, much of the even order harmonic distortion is cancelled in P-P config, leaving only the odd order distortion harmonics. This is why a lot of global FB is used, to reduce distortion and also improve bandwidth. Jack has discovered that IMD - Intermodulation Distortion - plays a big role in the overall sound.  By focusing on ways to reduce IMD, you already get much lower THD (Total Harmonic Distortion).  So, even in P-P, while there are odd order distortion harmonics present, the overall distortion spectra is very low. And, most importantly, the IMD is very low!

I first heard this when visiting Jack several  years ago to learn about transformer winding. At the time, I just wanted to be able to wind my own custom value chokes for different applications.  Jack taught me a lot in that time. While I was there, I heard a 10W EL34, SE amp that he had designed, based on this low IMD technology.  I was absolutely impressed by the sound of this little amp.  I could describe it in no different way other than to say it was special and extremely musical.  We compared it to a number of different P-P and even a 300B amp that he had built and none of them had the same qualities.

Our A30 amps are built with transformers that use the same winding technique as this first 10W amp. Jack used this same technology, applied to a P-P output transformer, and found that the same results with regard to IMD could be achieved there also.  When he sent me the 10W EL84 amp to listen to, I heard that same magic as the 10W SE EL34 amp I heard several years ago.

So, to answer you question, parallel SE typically does sound better. The cost is paid in the size and expense of BIG output transformers. With Jack's new P-P transformers, I am confident I can achieve the same sound in a 30W integrated with transformers sized so as to NOT give you a hernia when you pick it up.

In closing, it is a fact, I have since learned, that given enough FB (skies the limit, right?!), the output transformers can be very small and have minimal core size. You could make a 100W P-P transformer, with enough FB in the design, such that the transformer's size would be MUCH smaller than a 10W SET output.  It would measure well, with good BW and low distortion.  It would sound terrible however and may also have no bass. Jack has taught me that there is a true art to the design of tube amp output transformers.

Dan

Tyson

Re: New Directions at Modwright!!!
« Reply #49 on: 12 Sep 2018, 07:36 pm »
Ah gotcha.  Thanks for the detailed response, that makes sense.

Genez

Re: New Directions at Modwright!!!
« Reply #50 on: 12 Sep 2018, 07:50 pm »
.........











« Last Edit: 13 Sep 2018, 05:40 pm by Genez »

modwright

Re: New Directions at Modwright!!!
« Reply #51 on: 13 Sep 2018, 03:55 pm »
Hi, this could certainly be done. Something like the EL84 design would not be a very large piece. In fact, the 10W unit could be quite compact. The problem is that 10W is a very limited market as far as speakers go. I would still think that the 30W version could suit your needs.  What are the max dimensions that you would consider compact?

Thanks,

Dan

modwright

Re: New Directions at Modwright!!!
« Reply #52 on: 13 Sep 2018, 03:56 pm »
Another tube under consideration for a P-P tube integrated, is the 6L6.  This tube has a long history in HiFi and there are A LOT of different 6L6 and variants available.  Power ratings would support our goal of 30W I believe. Input welcome.

No matter what design we do, I don't intend for this to be a huge amplifier. It will really depend on the size and weight of the transformers, but P-P should allow us to keep this in check, in the 30W range.

Thanks,

Dan

Genez

Re: New Directions at Modwright!!!
« Reply #53 on: 13 Sep 2018, 05:15 pm »
Hi, this could certainly be done. Something like the EL84 design would not be a very large piece. In fact, the 10W unit could be quite compact. The problem is that 10W is a very limited market as far as speakers go. I would still think that the 30W version could suit your needs.  What are the max dimensions that you would consider compact?

Thanks,

Dan

Hi Dan....   I was thinking about a good tube preamp.  Not looking for an amp.   Something small with true balanced circuits.

Tyson

Re: New Directions at Modwright!!!
« Reply #54 on: 13 Sep 2018, 05:16 pm »
Another tube under consideration for a P-P tube integrated, is the 6L6.  This tube has a long history in HiFi and there are A LOT of different 6L6 and variants available.  Power ratings would support our goal of 30W I believe. Input welcome.

No matter what design we do, I don't intend for this to be a huge amplifier. It will really depend on the size and weight of the transformers, but P-P should allow us to keep this in check, in the 30W range.

Thanks,

Dan

Of all the pentodes, the 6L6 might be the closest in sound to a true SET.  I have a pair of RCA 6L6GA tubes in my amp right now and they are just beautiful sounding. 

modwright

Re: New Directions at Modwright!!!
« Reply #55 on: 13 Sep 2018, 05:32 pm »
Thank you, that may be a way to go! I just need to see if we can achieve 25W-30W in an integrated with these tubes.

Dan