The DynaGrid Rectifier Design Log

New Product from Decware coming this fall.

UPDATE: 6/27/2025

After a year of reading the STR thread on this forum, I wasn’t surprised to find the sound can be noticeably better than a good 5U4G using the right tubes. Getting the ideal tubes for a specific amp or preamp kind of turns it into a power users game vs., something for someone newer to tubes.

Rectifiers, such as the 5U4G, introduce a natural voltage drop and nonlinear impedance, creating a "sag" that softens dynamics and adds a warm, musical quality to the sound, often perceived as richer and more engaging. This sag enhances harmonic richness and provides a smoother response to transients, complementing complex music with a pleasing compression effect.

Solid-state diodes, while more efficient and precise, deliver a stiffer, linear power supply that can sound clinical or harsh in some systems, lacking the dynamic interplay and tonal warmth that tubes impart. The exception would be something like the ZMA where you use capacitors that are 1000 times larger than normal.

To improve upon the average 5U4G rectifier meant exploring more and more exotic $$$ rectifiers until you end up with something like the STR.  


The natural voltage drop and sag of a rectifier is factored into the amplifier design and especially the amplifier voicing. But even with the factory original rectifier tube, as the voltage at your wall outlet changes up and down, the B+ voltage of your tube rectified amplifier will also change. This can be why your amp sounds a little different from session to session in some homes or apartments.

The rectifier tube will also drift over time. There is no way to know this, because there is no high voltage meter on amplifiers.  It would be nice if there were, and you had a way to adjust the B+ to not only the amplifiers design center, but outside of the design center to experience how that affects the sound so long as it is limited to a safe window of operation.

Another minor problem with rectifier tubes is that tubes do in fact drift and diminish over time. Since a rectifier has two plates inside they both have to be precisely matched.  If one drifts away from the other, there will be reduced performance and likely increased hum.  Using two separate tubes, or more, for rectification requires that they be matched and stay that way for optimal results.

Anyway, I wanted a single device, with a single tube to prevent having to match tubes, that would work for everything be it an amplifier or preamp. Basically anything that can use a 5U4G or similar. Say from 30 mA to the 5U4G max rating of 225 mA, one product that does it all.

I’ve taken a unique approach to this that has many advantages.  

This is what I’ve done:

I've replaced the rectifier with a pair of 3 amp solid state diodes that drives an 845 triode with adjustable grid bias to replicate the 5U4G voltage drop and sag characteristics but with infinite adjustability within a safe operating window so the voltage drop can’t be decreased or increased too much.

Additionally a soft start is built-in using this approach which is particularly nice for directly heated triode amplifiers.

The 845 tube was chosen because there are so many different brands available that it drives the price to as low as $50 a tube.  Also, rated at 100 watts the tube will rarely see 11 watts in this design and operates at well below half it’s rated voltage so I would expect it to last possibly for the life of the product.  This takes a lot of the cost out of ownership because the infinite adjustability eliminates the need to roll different tubes.  You can just dial it in, watching the meter as you go, and hearing the results in real time.

As an example; You might decide that a Sarah 300B amplifier sounds better at 380 volts rather than 405 volts with the particular tubes you’re running.  With the meter you can always see what the voltage is so if the wall voltage drops and your amp is reading 370 volts, you can raise it to your magic number.  Or if it’s too high, you can drop it.

So here are some bullet points of sorts:

Hybrid Approach: Hi current solid-state diodes eliminate tube rectifier failure modes, while the 845 triode provides tube-like sag and warmth, controlled via adj. bias.

Adjustable Voltage Drop: Allows real-time tuning of B+ voltage, avoiding the need for tube swapping and ensuring compatibility across all tube rectified amplifiers and preamps that would use anything from a 5Y3GT, 5R4G, 5AR4, 5U4G, 274B.

Monitoring: Both amplifier current and B+ voltage meters let you see how much current your amplifier draws with the tubes that are in it, and what the high voltage is at in real time.

Simple Design: A single 845 triode that almost never wears out with two meters a power switch and a knob to adjust the voltage drop.

Thermal Efficiency: External heat management and diode efficiency lower amplifier temperatures, enhancing component longevity. For example, the Sarah amplifier temperature dropped from 128’F to 110’F.

Dynamic Response Control: Adjustable bias mimics tube rectifier “sag” or provides a stiffer supply, offering tonal flexibility not possible with the 5U4G or fixed aftermarket rectifiers.

As you can see, this design log (unlike previous ones) jumps into the design after it has already happened.  I’ve been testing it for 6 months or so, and it took about that long to design it to function the way I wanted and be completely safe.


I can confidently say that no rectifier tube I own can touch it sonically, it's sooo meaty and holographic... even my collection of high dollar 274B’s do not sound as good. And to even have a collection of high dollar rectifiers means you have also had some blown ones because so many come from eBay and China.

This will be the rectifier tube that can’t be bested at any price and lasts for life.  Additionally it will likely increase the life of all the tubes in the amplifier, show less stress to the transformers, increase capacitor life, and lower the heat of the amplifier, so again if you run exotic tubes in your amp, this could easily increase the usable lifespan.


I’ll post some pictures of the prototype in here eventually and the production units as they come along. I’m on the very tail end of the design process so I expect it to go into production this fall. There could be two models, I haven't decided yet. Pricing is still up in the air, but it would be competative.

The  (C) 2025 name DynaGrid comes from Dynamic Grid Controlled Rectification. As far as I can tell, nothing like it exists in the world making it a world's first!

-Steve

Very interesting.

Sounds so interesting Steve. Other than price, my other question is will the wait time for this device be less than four years once ordered.

Fascinating Steve! I'd much rather consider this than the STR. (Though I am still not sure that I am wanting this sort of device, nor that I will be able to afford it).  Will be so interesting to see the final model(s) and pricing.

Very cool! This brings up a question:

CA, with monoblocs, how would this be connected? Would you need one for each channel? How is the STR setup with dual amps?

MM wrote on 06/28/25 at 15:05:38:


It's just a (hopeful) guess. . . but this may be on the accelerated list rather than the amplifier list. Time will tell.

Lon says;
"It's just a (hopeful) guess. . . but this may be on the accelerated list rather than the amplifier list. Time will tell."
     

Or place order now for anything and then switch to DynaGrid when time appropriate ??

I knew it! Deposit down and back on the list!

Mental Notes:

1) Given the popularity of the STR, I was wondering when Steve would offer something similar? I would much rather get something from an outfit that is well oiled and established, from an engineer that I know and respect, and a customer service situation that doesn’t involve being dependent on the whims of one individual. Not meant to be disrespectful of Al and what he has achieved — you know what I mean.
2) Missing/Craving a new development thread!
3) Amused that the two biggest STR holdouts just perked up!

How Steve kept quiet for six months is beyond me! Looking forward to more updates!

Kamran said, "How Steve kept quiet for six months is beyond me!”

So, note to self (and all of us) - don’t play poker with Steve.

Randy

This is very interesting for sure. Hopefully not a 3 year wait but it surely don't look like a black box!
What happen to the ZCA Steve?

I would want to know what you are hearing when used with amp x. I am interested in use with SE84UFO25 and Torii Jr V2. Hopefully, you will share more over time.

Do you limit development in short term to single rectifier products for ease of manufacture and product launch? It seems to me that you would benefit in the short term to limit the product initially to Decware products. You obviously know the safe operating window of your products.

Your comment about a 300mA meter in the production model. Will this fit the operating range of your amps/preamps? Do premium meters matter? Power supply design considerations? If I am running a preamp and amp, where would I get the most benefit from a DynaGrid?

I only see one knob. What does it adjust? Are amplifier current and B+ voltage related as you adjust? You made comments (as an example) of running a Sarah at 380 volts instead of 405 volts? Based on your comments of wall voltage dropping reading to 370 volts. I think wall power stabilization could be an issue. How should owners tackle this issue? It seems like something more than a ZLC is needed. What are your thoughts?

Can you tell us more about the power in your listening room? Do you run dedicated circuits? Use ZLC?

Monitoring is a benefit, but how does one take action based on what one is seeing from a amplifier current or B+ voltage perspective?

Is the cord to the rectifier port detachable? Do different cables even make a difference?

I do not understand a lot of technical speak about how some 'things' work. But there is no doubt in my nowadays 'dented' mind, that when Steve has his mind set on something, it's obviously going to be a winner. So fn talented. I will try not to get too personal on the internet, but I got in on Decware when the Zen UFO2.1 amp I ordered (my pretty wife made me get it! She saw me reading about them several times) wound up being a wait time of 2 years. I had already been through 2 very serious, more recent hospital stays, 3 years apart and a total of 3 'episodes' in my life, so because of this, I was paranoid about ordering. I was SO blessed to even ~BE~ at all and no one understands how I am still here. Especially me.   Other than my family and friends, this wait on this amplifier was so exciting to me. There are some things I can no longer do, but listening to good music.... always so important to people like us too. Our little Zen amp IS the best electronic music purchase in my lifetime. For those of you that are financially able and healthy etc, order what you want here. The wait is sometimes the pits, but weirdly exciting too at the same time. How do you explain this? I am currently getting ready to fire up the music in here for a bit. This happens a LOT. All the very best to Steve and ALL staff over there. As well as this forum that has such wonderful and helpful people too. It's not about me, it's about YOU folks waiting to order, like I did....if you can swing it~ think a bit more about it and just do it. I told my way better half to be glad I was once as sharp as a rocket scientist...pretty sure she never bought it though...  Always~  Mike

Mike, Hock--I'm with you both. Music is what keeps me going, looking forward, get through the morass of insanity in the world. And Decware components have been with me for nearly 30 years now, they've gone through the changes in life and fortune that I have and I have reached a plateau of beautiful sonic playback that sustains me and calms me. I owe a lot to the Decware family and to this community of forumites.

Are we going to be able to listen to this at this years Decfest?
Bob

The unit is designed very specifically for the 845 tube ONLY.  If you want to roll tubes, there are probably 50 or more different brands ranging from $50 to $1900.

I am doing all of the testing with $100 Linlai 845 tubes, which is what it will ship with.

Steve