Review: Tube Audio Design TAD-1000 Tube amp

Category: Amplifiers

The amps under review here, the TAD-1000’s are built in China and are hand finished in the USA by one Paul Grzybek, an audio good guy if ever there was one, of BizzyBee Audio in Chicago. Weighing in at a substantial 43lbs each, the amps are nicely finished with a thick black anodized face plate and a lovely brushed stainless steel chassis. The transformers are carefully finished with stainless steel covers. The indicator lights are located front and center and are bright blue, really bright blue! The amps come well packed in solid Styrofoam containers that even FedEx can’t damage. Your amps will arrive in one piece.

The tube complement consist of an EH 12AX7 input tube feeding a pair of EH 6V6GT’s. The output is handled by a matched quad of new Tung-Sol 6550’s for 100 watts per amp. Each amp has an input level control on the back panel, a variable feedback control, set at about 50%, and a triode/UL switch. The amp is 60 watts in triode mode. All listening was done in UL mode which sounds better to these ears. For this review all tubes were stock except for the input tubes which I replaced with a NOS pair of RCA “Cleartop” 12AU7’s, which I find more harmonically rich and detailed than the stock EH 12AX7’s.

Setup and biasing are easy. Each tube is individually biased (to 650mv for 6550 or KT-88 and 350mv for EL-34’s) with top mounted access points and bias adjustments using the supplied multimeter. The entire process took about 90 minutes from start to finish.

Once setup, the amps were run-in for 50 hrs before any serious listening. The majority of this time was filled with home theater uses, which provided the majority of the break-in listening.

As is my usual practice, vinyl represented the source material for this review. The material used for this review includes:

Holst: “The Planets” Mehta LAPO Decca SXL6529
Schubert: “Symphony # 5” Sound 80 DD
Copland: “Appalachian Spring” Reference RR-22
“Cantate Domino” Proprius 7762 White Jacket
Ravel: “Alborado Del Gracioso: Classic Records test pressing 45rpm LSC2222 45
Stan Getz/Joao Gilberto: “Getz/Gilberto” Verve810 048-1
Vince Guaraldi: “Jazz Impressions of Black Orpheus” Fantasy 3337
Harry James: “The King James Version” Sheffield Lab-3
Rickie Lee Jones: “Rickie Lee Jones” Warner BSK 3296
Bob Marley and the Wailers: “Survival” Island LPS 9542
David Bowie: “Changes Bowie” Ryko Analogue RALP-0171-2
Suzanne Vega: “Suzanne Vega” A&M SP6-5072

My initial impression of the 1000’s is one of great harmonic accuracy. On the Holst disc, the string tone is gorgeously reproduced, while the richness of the choir is exemplary. The same can be said for the other classical discs. All were reproduced with a sense of tonal accuracy and harmonic realism that I failed to get from my PS Audio 100C.
If you’re familiar with “Cantate Domino” on Proprius than you know that it recreates the ambience of the church with unusual precision. The TAD’s reproduce this ambience with great specificity, one can hear the stone walls of the church; the effect is eerie and moving. All of this is accomplished without blurring or muddying the vocal or instrumental lines on this outstanding album. Generally I can state that these amps have a very nice way with the harmonic structure of orchestral instruments, reproducing the wood, rosin, brass and drums with natural and believable felicity.

Dynamics seem limited only by the speakers and the room. The amps go on and on dynamically. These amps are exceptionally good at going from ppp to fff quickly and decisively. Ravel’s “Alborado” on Classic Records 45rpm single-sided pressing is awesomely dynamic, a new reference IMO. Compared to the PS Audio, the TAD’s reproduce the dynamic shadings and movement in a more natural manner, without moving the stage either forward or back. The music gets louder without a marked change in positioning, a rare occurrence on LP’s and an effect that doesn’t happen to live instruments.

Imaging is another strong suit of the amps, as one might expect from monos. The Getz/Gilberto disc was exemplary in this regard with the placement of Getz’s sax and Astrud Gilberto’s voice each occupying their own specific space. That space is maintained at different volume levels and dynamic shadings, very nice indeed. The Harry James is big band at its best. Well recorded and quietly pressed, rare for Sheffield’s IMO, this album maintains the sound of a big band with suitably biting brass, reedy, sax sounds and richly harmonic reproduction of the entire band. The drum solo on track 3 “Cherokee” is as well sized as any that I have heard, it is reproduced quite convincingly.

“He who feels it, knows it” so sang Bob Marley’s widow Rita. On Bob’s album “Survival” one feels and hears the emotional content and message on such songs as “Zimbabwe”, “Africa Unite”, “One Drop” and “Ride Natty, Ride” in a way that allows the listener to “know” Bob feels it in a way, though hard to describe, that is more personal than before, more immediate and heartfelt through these amps.

The mystique of tubes remains despite the “antiquated” technology. Big, heavy and hot, tube amps enjoy a place in the High-End for one reason; they arguably reproduce the sound of music more realistically than transistors do. The TAD-1000’s represent an amazing combination of value and sonics that one will, IMO, be hard pressed to find anywhere else. These are not the best amps on the planet but they are damned good. Any flaws represent flaws of omission. The top might be a little softer than real, the stage a little forward, and I do mean a little forward. These are things I can easily live with given the otherwise insanely good qualities of the amps.

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Click to view my Virtual System

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Equipment like this gives the "little guy" a taste of what the "big boys" experience with their mega-buck gear.

I enjoyed reading your review.
I looked at these amps, but I have to admit that the biasing instructions scared me quite a bit. They were prefaced by the following statement:

"Very important:

Tube bias must be set immediately when tubes are installed. Excessively high tube bias will burn output tubes in a matter of minutes. Output tube glass gets very hot and will burn your skin – the adjustment procedure below is only performed starting with a cold amplifier. Note: The amplifiers are mirror copies of each other – one amp has adjustments that turn left to raise the bias, the other amp turns right. Read instructions below."

--maybe it's just me, but I think that turning the pots in a different direction on each amp to raise the bias is confusing. Hopefully one can correct any mistake before the tubes burn out. I see that you had no problem biasing the amps, but I have to wonder if you just got lucky.
I followed the directions precisely. In fact, when I set up the amps I had the bias control set at the top of its range and I watched the meter. When it went too high I turned the control to the opposite stop and the bias was set very low. At that point I continued with the set-up, as per instructions, and had no problem at all.
How efficient are you ML Speakers? What kind of load do they present to the amp? Did you play with the variable negative feedback settings?

The ML are 89dB/meter efficiency with an average load of 4 ohms with a dip to 1.2 ohms at 20kHz. Not a problem as there is hardly any musical energy up there to worry about.
Four transformers in a mono amp? Why is that?
Eldartford, I asked Paul the same question. The 2 black "transformers" are just covers for the power supply caps.
For those of you who have yet to try this....
I received Paul's Iron Lung Jellyfish power cords yesterday (where in hell did that name come from? Talk about a non-sequitor. Iron Lung because they produce more air? Or because the astonishing improvement sucks the air right out of you? Perhaps the Jellyfish should have been "Jelly roll," because they produce a sweeter middle. I could go on, but you get the idea).

The new cords look unremarkable,very much like any ordinary 14 guage gray power cords, with the exception of the clear, colored plug and socket. They look nothing at all like the exotic and expensive pwer cord offerings from the high-end.

I use a Vans Ever "Unlimiter" as my power conditioner, and after a brief reference listen, replaced the stock chords with the new ones, expecting nothing.

At first listen, that is what I thought I got.

However, I have learned to listen to tweak components over an extended range of recordings before assessing them. Something that does not jump out immediately during a quick A/B can still reveal itself. Such was the indeed the case, and a bit more listening revealed what I'd missed in the quick A/B.

Here is what I heard with the new chords (some of these effects were significant, others minor):
Noticeable improvement at the loud end of the dynamic range (e.g. more Blat in the horns), slightly improved clarity (I was able to reduce the feedback one click...very weird); but the best effect was improved center fill, resulting in a much more coherent and solid orchestral presentation. Overall, a significantly more complete and satisfying musical event. Not bad for 50 bucks.

Interestingly, when I flipped the amps back to triode mode, I liked that mode less than I had previously. I'm not sure why that is, but I suspect that because of its superior dynamics, the UL mode is just superior overall, and that, perhaps, additional break-in of my KT77s has occurred. While the triode mode still does its thing very well (relaxed, open and seemingly "natural" sound), it lacks the punch of the real thing. With the tube complement I am now using, UL mode gives 80-85% of the openness of triode, but delivers a much more realistic dynamic presentation. On good jazz recordings, instruments can be holographic.

So, why does a freakin power chord change anything? It really drives me crazy (for me a very short trip).
Do I really want to go and spend hundreds of dollars on fancy power chords? (Er, no, I do not).

However, I believe Paul G. says that the power supply is the "engine" and the tubes are just the "wheels," so getting change by tweaking the power supply makes sense.

That said, I would be very interested in hearing anyone's experiences with different output tube types and brands. I have read good things about the Tungsol 6550s and the EH KT88s. I am looking for a tube that will tighten the bottom up a bit, without sacrificing the mids and top of the KT77s. Also, what is the correct bias setting for the Class A mode for 6550 and/or KT88 tubes (The normal bias recommendation for those tubes is 65 mils, is it not?)
I'm using the TS 6550's and I find them to be very dynamic with a very good top end. The mids, if not as good as the rest of the frequency range is still pretty damened good. Run in the tride mode the 6550 is dynamic enough, especially through the bottom end to have realistic jump factor with symphonic music. I am considering the KT-77 as outputs myself. Have you tried the big bottle EL-34's in the driver stage? I hear they add a seriously "tubey" component to the sound.
Risabet, I use the KT-77s as a driver as well as output, but have heard a bit of buzz about the large bottle EL34s. However, I am concerned about your "tubey" description. The JJ KT77s were a very significant improvement from the the stock Svetlanas. In the TADs, they are as dead neutral as any tube I have ever heard, and provided additional dynamic capacity and clarity over the stock tubes. One other benefit is the ability to use UL mode. With the Svets, triode seemed significantly better, but the JJ KT77s in UL provide about 80-85% of that triode sonic glow, but add more realistic punch. With good recordings, instruments and vocalists can be holographic and very, very live sounding. I don't know if this effect will be the same with other tubes, like your TS 6550s, since even the two EL34 types were different (I did not like the Svets in UL nearly as well).

Another very significant improvement was wrought by finding the right 12AX7. We (my tube supplier and I) went thru every top rated AX7 that is around, including some old favorites of mine, like the GE 5 Star 5751s, and the Telefunkens. Even tried a few top rated 12AU7s. The one that rose above the others was the Ei Gold Pin 12AX7. We both agreed that the sound of these Eis was significantly more relaxed and natural. If you can find them, they are worth a try.

I really want to find some good Ei KT90s. They have a bad rep right now, due to poor QA in manufacture. I have access to the TS 6550, so may try those, based on your rec. Some say the 6550s to have are the NOS GEs. I have heard the EH KT88 tubes recently, (they were terrific) but in the context of a system very different than mine, so I am not sure how they would sound in the TAD-1000s with my speakers.

I really don't know why I am generating all this angst about tubes. The KT77s sound fabulous, particularly so since I implemented Paul G's Class A-A/B bias setting recommendations. My speakers are full range and all I am trying to do is get just a wee bit more control over the lowest octave (a la solid state). Not that the bass is bad. It is very good (see below). I am also afraid that I will be giving up the great neutrality, and lord knows what else in my search for that last bit of low-end control.

I took the amps over to a friend's house so both of us could hear how they work with a very different speaker system. He uses classic Altec drivers, including large 15 cell horns that go down to 500 cycles, and ultraphile "Symphony Master" Japanese cabinets housing the Altec bass driver. He also has some very good powered subwoofers, that he uses or not, depending on his often changing configuration. We have heard his system countless times, using mostly classic amplification, sometimes bi-amped, sometimes with single monoblocks and stock crossovers. Without speaking for him, I think it fair to say that we were both astonished by the sound of the TAD-1000s in his system, particularly the previously slightly reticent low bass. No need for sub-woofers. In his fairly large room, the sound was amazing, the speakers earning their name.

Although I don't want to sound like an advertisement, that they work very well with his Altec based speakers, your MLs and my VRs, three very different types of loads, speaks loudly for what a great product the TAD-1000s are.

My Von Scheikert speakers are comprised of two boxes per side. They were very recently upgraded at the factory. Before buying the TAD-1000s I had been bi-amping the VRs with some modded classic tube amps. When I discussed amplification with them, the folks at Von Schweikert were fantastic, suggesting that using a solid state amp for the bass, with tubes for mid and top, could be best way to squeeze maximum performance out of them. However, I prefer using tubes. While the bass is not always as tight, it is more "organic" and natural sounding to me.

Since I have two boxes a side to drive, Paul also suggested a means to set up my bi-wire that may optimize performance. I am still astonished by the change that was wrought by changing the bi-wiring set up. It is as big a change to the sound as almost anything I can remember, so much so that I am still trying to get my head around it. Paul is amazing. If you bi-wire you must try it.

BTW, in the photo of your amps, I think I see tube dampers on your input tubes in the photo of your system. If you haven't already done so, you should try dampers on your output tubes, as well. Use the High Temp dampers, at least two per tube.

So, do you use the class A-A/B bias setting for the 6550s? If so, what are the correct bias settings for that mode?

Hello, does anyone have a schematic for the TAD 1000 amplifiers? It would be nice to get a copy, please.
Regards, Robert