Seriously considering tube preamp…opinions?

Tube virgin, here. I am building a system and I'm trying to contain the preamp/amp cost to $3k or so. (I could go up a little.) 

I'm inclined not to dive into tubes all the way through, but get a solid state on the output end. (Open to suggestions; inclined toward PS Audio, Parasound.) I'm reading around about tube preamps and have talked with my local dealer, who sells Black Ice/Jolida and Prima Luna (PL). He used to carry Rogue but said they kept coming back for repairs. That's why he carries PL.

I'm asking these questions after having established (via reviews, comments) that Schiit gear is quite the value. Lately, I've been reading about Decware and other small tube makers. I'm very curious about buying direct, if possible, and a company that stands behind their products is crucial.

So, your opinions about tube integrated or *especially* tube preamps —

1. Who do you like? Consider I want to do pre/amp for a total of $3k if possible.

2. Do you think PL is worth all that money just for a preamp? I get the feeling they're high quality but a bit over-hyped. (No disrespect to the highly passionate Kevin Deal, but he's all over my search results.) And what would you think about $2k/$1k preamp-to-amp spending ratio?

3. Any sense of what happened to Jolida since the name change to "Black Ice"? I see there's a sordid story there but did the re-branding clear up the mess? Any experiences with the Black Ice company?

4. I know there are many Schiit fans out there; so my question would be -- did anyone consider Schiit for tube preamp and go another way? Or move beyond Schiit for any particular reason? It's hard not to just capitulate and do a Freya+ or Saga+ but why wouldn't one just go with Schiit?

8700e65e 845e 4b1b 91cc df27687f9454hilde45

Showing 45 responses by tvad

By chance have you tried any of the latest version new production input tubes such as Sophia Blue, or PSVANE MKII, Shuguang Black Treasures, or former TJ Full Music, JJ gold pin Frame Grid tubes - in any of your preamps or for amp input tubes?

Sourcing good tubes is definitely a consideration. They’re not as easy to find as they were just five years ago, and the adventurous pleasure of tube rolling can be an expensive crap shoot.

Frankly, it’s a good argument in favor of Pass Labs and First Watt Class A solid state.
Even if the newer parts were better? Just because it goes outside the original design?

Parts different from the original *can* alter the sonic characteristics of the original design. Sometimes different parts are installed purposely to change (or improve) the sonics of a component. This is often what is done by modification specialists, like Modwright, with excellent results. However, the improvement does somewhat alter the sound of the original component.

In the case of amplifiers or preamplifiers, unless I was purposely looking to change or improve the sound of the component through a modification (versus a repair), I wouldn’t want to alter the characteristics of the original design, and neither would many future buyers.
I love having a triode/ultralinear switch. Two of my previous amps had one: VAC Phi 110 and Manley Snapper.
Triode operation offers a magical holographic image and wonderful midrange at the expense of power output and bass control, while ultralinear boosts the power output and offers excellent bass control while flattening the three dimensional image somewhat as compared to triode. 
Overall, I prefer triode operation, but when “Enter Sandman” is playing it cries out for ultralinear.
If I had to chose one or the other in a tube amplifier, then I’d choose triode.
Pass Labs Class A amplifiers sound so close to ultralinear tube amps that I’d buy a Pass Labs Class A solid state amp before I’d buy a tube amp that operated purely in ultralinear/pentode.
Tube amps that offer both are nice to have in a system.
Factory, or factory authorized service is preferable to independent non-authorized service, but sometimes there are geographically closer repair technicians who have stellar reputations among owners of certain brands. I wouldn’t hesitate to have equipment repaired by technicians like that, although I would want any parts used to match those originally installed.
I’ll never forget the first time I swapped out my beloved 200wpc mosfet solid state amp (in disrepair) for a custom hand made 17-watt loaner tube amp - trying it on my speakers at home. Woah...

It’s strange how that works. I remember having the same reaction after I swapped in a KT88 triode/pentode tube amp that replaced a 300wpc solid state amplifier. 
Then, I remember having a similar epiphany when I replaced the KT88 tube amp with a hybrid Moscode solid state amp. 
Then another epiphany when I replaced the Moscode with a 30wpc Class A solid state amp.

        This journey can be crazy!
One of the benefits of tube amplification is the differences in sound possibilities.

For example, triode operation (like the VAC Renaissance 30/30) offers magical midrange and an almost holographic image. The downside is a tad less bass control

On the other hand is the EAR Yoshino 534 with Push-Pull Tetrode operation which produces better bass control with a little less holographic image.

Some amps offer both triode and push-pull ultralinear modes so the owner can choose. This is a great option to have on a tube power amp, IMO. The Manley Stingray II integrated amplifier offers this, as do some VAC amplifiers. I owned a VAC Phi 110 that offered triode and ultralinear modes.
There is an EAR-Yoshino 868L listed on Audiogon right now, under $3k.

Excellent suggestion @bdp24. 
A really good 30wpc tube amp or really good 25wpc solid state Pass Labs will trounce many others with the same power output.

Exactly right!

Here's an example of a 30 watt tube amp that will trounce most other 30 watt tube amps:

@hilde45, if your reason to demo the more expensive (and shall we agree better) Salk loudspeaker was to pay for less required watts (and therefore a lower cost amplifier), then I think you’re approaching this the wrong way, but I understand the budgetary reasoning.

You’ve undoubtedly heard the cliche "it’s not the quantity of watts, it’s the quality of watts".

Match loudspeaker quality with amplification quality. You will be happier with your system in the long run.

I tool a closer look at the Backert Labs Rhumba 1.3 preamp, and it looks intriguing.

With a 75 ohm output impedance, it would match well with both tube and solid state amplification. Also, balanced inputs and outputs offer some flexibility down the road.
I’m likely going to change my order (I’m going to think about it a bit) to the Salk SS 6M speakers.

That seems like a good change well worth the increased cost.

FWIW...I notice Reno HiFi has two month old used Pass Labs INT-25 (the integrated version of the XA-25 amplifier @almarg uses) with three year transferable warranty for $5495 (retail $7250).
Based on the first of Ralph’s posts dated 2-26-2020 in this thread, though, it sounds like the Salk WOW1 (and other Salk speakers), like the Daedalus speakers I use, tend to be more versatile with respect to the choice of solid state vs. tubes than many others

@almarg, along these lines, I’d be curious to know your thoughts about the Zu Audio Omen loudspeakers. They have been reviewed using both tube and Pass Labs solid state amplification.

I have heard Zu Audio demo'd with both tube and solid state (including switch mode amplification). They sounded very good regardless of amplification topology.

Tubes add serious harmonics to terrible recordings to make them sound better. They also add harmonics to good recordings to make them sound worse.

While a bit of an exaggeration, this is true, although tube amplification often sounds better at clipping output level (as @atmasphere has explained).

It’s a primary reason I have suggested Pass Labs Class A solid state amplification (and gently joined by @almarg). 
@hilde45, thank you for the book link. I will check it out.

I often think I got into the wrong hobby...requiring patience for an impatient person. It likely explains why my home looked like a stereo emporium for a period of five years, and why I knew the UPS and Fedex delivery guys on a first name basis.

I suppose it could have been worse. I could have taken up building ships in bottles. 
I joined an audio club this morning and visits to folks houses in Colorado will be possible now.

That's a great step and will open doors to discovery and insight.

I'm realizing that this process may take a while. That's cool. I find it interesting.

The funny (and insidious) thing about the process is that it always takes longer than we think it will take. Enjoying the journey is as important as the destination. 

But you probably mean "home trials, shipping, travel to audition, buying, reselling" and more.

I do mean home trials of specific brands and models, and the pairings suggested. Home auditions of new equipment is a no-brainer. It puts the gear in your room. Your environment. You will incur shipping and return shipping costs if you home-audition. It’s part of the process.

Sometimes traveling is the best way to hear a wide variety of audio equipment ...particularly speakers, and you are fortunate to have RMAF in Denver if you can be patient.

I definitely do not mean buying and reselling, unless you’re buying top shelf used equipment that can be easily re-sold...but I have a feeling that’s not the best path for you.

Hard to do in-home trials of lots of stuff. pretty soon, it’s gonna be a year and a lot of shipping.
The hard truth is that building a high end audio system is hard. Very hard. It takes hours of auditioning...either in one’s home, or at dealers, or at audio shows. It takes research. It takes some book learning. It takes some luck. It costs money...not only for the equipment, but for shipping, and return shipping, and sometimes for travel.

Putting together a great sounding mid fi system with components from Best Buy is easy...and there’s nothing wrong with mid fi! Our modest home theater makes me very happy, and I spent zero hours auditioning home theater gear.

Folks contributing here have spent years learning and assembling systems. The good news for you is that the results of hard work, experimentation and learning are being shared here on your behalf. If you choose to follow the advice, you can (probably) bypass significant time and expense, but it does require some trust on your part.

You have been led to water. The question is if you will drink?
@hilde45, I recall listening to Omega loudspeakers around the same time I listened to Zu Audio. I much preferred Zu Audio...they better handled music I enjoy...but what I concentrated on were the large Zu Definition and Druid loudspeakers. I recall Zu Audio’s "bookshelf" speakers sounding quite good. I believe they were the Tone model; now replaced by the Omen.

A bit dated, but still:
You’ll note the reviewer spent most of his review time driving the Zu Audio Omen loudspeakers with a First Watt J2 amplifier. Having demo’d a J2, I imagine the pairing was excellent...dynamic, sweet (dare I say "tubelike"), and QUIET. Shhh...

I don’t have any thoughts about Ascend or Fritz.
It has been a decade since I listened to Zu Audio loudspeakers, but they are known for their high efficiency designs. 

Something like the $2,250 Omen MK II floor standers or $1,899 Omen bookshelf speakers might be worth investigating. The bookshelf speakers would require a subwoofer. 97 db efficiency. The floor standers while extending to 35 Hz could also benefit by a sub if you like room shaking bass.

Zu Audio loudspeakers come with a 60 day guarantee. You buy them. Have them delivered, and live with them for two months. 

As an alternative, they are in Ogden, Utah. You could fly there for a day and have a listen.
@djones51 wrote:
 ...concentrate on the speakers first and foremost...
That's excellent advice. 
@hilde45, 90db is certainly better than 84db and will open up your amplification possibilities.
Why are you only considering bookshelf speakers? Limited space?
At what *starting* level of db sensitivity does the choice of quality all-tube amplification open up? 88db? 92 db? more? (I suppose I’m not thinking of the tiny-watt tube systems, but things that are up to 35-40 wpc)
I would suggest 90db and above. Daedalus Audio and Silverline Audio (which utilize Dynaudio drivers) are two great loudspeaker companies making high efficiency speakers.

You will recall @almarg mentioning owning Daedalus speakers driven with a Pass Labs amplifier.

I once owned a tremendous system comprised of Silverline Audio speakers, a Pass Labs XA-30.5 amplifier and a Lamm LL2 Deluxe (and later a Lamm L2 Reference) tube preamp. I purchased all of my components either used or as demo units. 
VTL IT-85 Integrated Amplifier 60wpc  New $5250.00
It’d be crime to buy that instead of the used Pass Labs INT-60 for the same price. You’d have to turn in your audiophile card. 
By chance do you know, Is it all 100% point-to-point wiring or any circuit boards under the cover of the VAC amps?
I don’t. 
Aim high.
Buy separates.
Buy USA if possible. Easier servicing. More personal relationship. Supporting local businesses.
Nope on the new list additions. 
From your list I would eliminate everything under 60wpc. With 84db speakers, you’re just going to be better off with more power than less to provide more headroom. 

My first choice would be the used VAC Standard preamp + VAC 100/100 amplifier for $4100. There is simply nothing on the list that compares for quality. VAC electronics last forever and are virtually worry free. It’d be like shopping for an excellent new Honda Accord, and coming across a super clean, well maintained and affordable used Porsche 911 on the lot (except the Porsche would require maintenance and the VAC stuff won’t).

Next would be one of the Quicksilver combos. Separates offer more flexibility down the upgrade the preamp or amp.

I wouldn’t consider any of the others, but that’s me.
hilde45 OP186 posts02-25-2020 5:06pmOk, Tvad. I’ll think about those!
At the moment, I thought I might be able to do (at the least) something from Quicksilver, e.g. $1295 QS Line stage preamp + $2995 60 QS Watt Mono (60 watts) = $4290
Go for it!!! 

Particularly if they come with a 30 day money back home trial period.
@hilde45, I do believe it’s going to be difficult to find a tube amp+tube preamp or tube integrated amp that meets your criteria of a well-known, and easy to re-sell brand for under $6k that mates well with the 84db speakers and drives them to listening levels most would find acceptable. Particularly if they’re new and not from a boutique manufacturer (some excellent gear comes from boutique manufacturers, by the way).

However, only you know how loudly you listen, how large the space is you want to fill, and what you find pleasing.

I hope I’m wrong.

There is a used VAC Phi 200 amplifier available now for $4k. Mated with a $2k preamp...would get you there. Also available is a VAC Standard Preamp + VAC PA 100/100 amplifier for $4100 that would also likely do the trick. VAC has a long history of high quality, heirloom worthy equipment...and exceptional customer support.

If you find a tube amplifier that makes you happy with those speakers, please share the make and model.

Good luck, and have fun!
Here’s where I am, budget wise — I have shifted above my initial budget above $3k because of:

(a) desire for tubes, possibly all the way
(b) desire not to be buying again in 5 years
(c) desire for headroom
(d) desire for quality
As has been discussed several times by several contributors in this thread, it will be quite difficult to find tube amplification that will properly drive the 84db/8 ohm loudspeakers you are leaning toward purchasing. A $6k budget makes this even more challenging.

If you want all-tube amplification, then you would be wise to investigate higher efficiency loudspeakers...above 90db for sure.

Otherwise, used Pass Labs is your answer (or perhaps Clayton Audio...but harder to find and more difficult to re-sell).

As a past owner of Pass Labs and VAC amplification, and as a present owner of high efficiency loudspeakers, I concur 100% with @almarg.
Well said. 

@hilde45, my answer to your question is:

1) You need not pay $9000 for a INT-60. Reno HiFi has a used INT-60 listed for $5295 with one year factory warranty remaining.

2) IMO, I would not recommend any of the other solid state brands in your list as equal alternatives to Pass Labs except perhaps First Watt.
First Watt is a Nelson Pass designed amplifier. The Pass Labs INT-25 is closely related in design to First Watt, which is why I suggested it as an alternative to the INT-60. The design of First Watt anps is different than Pass Labs, though. They require more careful matching to loudspeakers than do Pass Labs...but First Watt sound exceptional. Please discuss with Mark at Reno HiFi.

3) I generally agree with @mesch’s excellent comments that follow mine. I recommended Pass Labs as a unique situation considering the speakers you already have on order. Again, I emphasize, that a Pass Labs amplifier can be demo’ed in your home with your proposed new loudspeakers for only the cost of shipping and a 5% re-stocking fee: a small price to pay for the opportunity to hear the combination in your home.
The passage below is from the Sterophile Pass Labs INT-60 review. The reviewer is listening to KEF LS50 loudspeakers that have efficiency and impedance specs of 85db/8 ohms...close to the 84db/8 ohm specs of the Salk WOW1.

Listening with the KEF LS50s
The best thing about the Compact Disc has always been the lovingly remastered sets and series of historical, esoteric, and regional music. London Is the Place for Me: Trinidadian Calypso in London, 1950–1956(CD, Honest Jon’s Records HJR CD2) is a modest but well-chosen compilation that includes high-quality images of each song’s original record label. Young Tiger, The Lion, The Mighty Terror, and others are included. It’s a CD to be treasured, and I’ve played it countless times, sometimes for days on end. The music just keeps getting better. However, through most of my systems it sounds as if it’s coming out of a table radio. Not with the Pass Labs INT-60 and the KEF LS50s. Finally, this music sounded as free, richly toned, and swinging as I’ve always wished for. Every song grabbed me, and made me smile and wonder what life was like for Caribbean immigrants in a London still recovering from WWII.
@hilde45, with due respect to Jim Salk, his answer is a bit protective as he avoiding the appearance of favoring a manufacturer whose amplification he may prefer to the exclusion of others.

Certainly, he uses certain amplifiers to vote his speakers, yes? And, he uses certain gear at audio shows to demonstrate his speakers at their best, yes? If he is unwilling to share that information with you, then that’s his prerogative. Your next option is to check Salk user forums/threads.

84db speakers require 32 watts to play at 99db. Do you listen at 99db peaks? Also, the Pass Labs Int-60 runs Class A up to 30 watts...or about 99db. Class A solid state watts are exceptionally sweet sounding.

Per a Stereophile measurements test, the Int-60 clips into an 8 ohm load at 79 watts. 79 watts would be a peak around 103db. Do you ever listen this loudly?

Bottom line, the Pass Labs Int-60 would drive the Salk very well, IMO.

However, I suggest once again that you call and speak with Mark at Reno Hifi and tell him the speakers you intend to use and the specifications. Let Mark help you. If things time out correctly, it’s possible you could have the Pass Labs integrated in your home at the same time as the Salk speakers. He may tell you that the smaller, less expensive, Pass Labs Int-25 may be all you need.

BTW...those Salk WOW1 mini monitors at 84db efficiency will cause you to spend more money on higher wattage amplifier than you have to spend if you were to purchase more efficient loudspeakers. There's no right or wrong answer, but it's a reality. That Pass Int-60 clipping into a 8 ohm load at 79 watts would get you to around 108db on 89db efficient speakers (as opposed to 103db the 84db WOW1).
@hilde45, have you asked Jim Salk what specific brand/model of amplification he recommends...or what specific amplification his customers use with his speakers?

Seems to me that’s a question that should be at the top of your list.

When you receive the Salk speakers, you are going to be driving them with your present amplification, which may or may not be ideal. I’m at a loss to understand how you are going to give the Salk speakers a fair and proper audition without ideal amplification?
INITIAL COST vs. Amortized cost over a long term:
If you buy the right preamp and amplifier (right from the get-go) - (tube or ss), amortize that initial cost over 10-20 years vs. a five year purchase buying a lesser amp you’ll upgrade again in 5 years anyhow. Return on investment also has to do with longevity too, avoiding upgradeitis later. It’s not just about the initial purchase price.
+1 @dcooney. Well said.

@hilde45, if you are seriously considering replacing your present speakers, then you’re wasting time listening to amplification driving speakers you’re not going to own.

Auditioning amplification prior to settling on speakers is an audio merry-go-round you would be wise to avoid.
My thinking against such a high dollar purchase was that I need to live with solid state or tubes or hybrid for a while before knowing what I really want. Paying $6k or whatever, now, much now makes the experiment feel riskier than paying $3k. I guess it all gets re-sold at some point, though, so best not to dwell on the purchase price.
@hilde45, I have mentioned several times that the Pass Labs is available to audition in your home through Reno HiFi (via a purchase and return). There is a small 5% re-stocking fee, which is the price for the opportunity to live with the amplifier in your home for two weeks.

Mark strives to get you the proper amplification for your system and speakers, so it's important to have a good conversation with him about your system and your goals.

To suggest that you’re only option is to risk buying, and re-selling is simply not true.
@tvad After finding myself really psyched about the tube experience, I’m now concerned that you are outlining a real, forced dilemma: give up the speakers or give up the tubes. Or at least give up all-tubes. Some tubes is still possible, if the match is right. Pass labs is beyond my price range and it almost seems silly to outmatch the speakers by so much, no?
The Pass Labs integrated amplifier may be beyond your budget (or it may not...). You have undoubtedly heard the cliche, "Buy cheap, buy again."

It’s true. It’s why it’s a cliche.

A Pass Labs integrated amplifier would/could be a long term purchase. It could be all you ever need. So, you have to ask yourself if you want to stretch your budget and buy now for the long term, or do you want to buy within your price range and risk the urge to "upgrade" and end up spending more than you would have if you had purchased the Pass Labs in the first place.

This advice applies to whatever amplification you eventually purchase. Buy something that is going to carry you through the next speaker purchase. It will ultimately save you money.

Also...the Pass Labs is not out-matching the speakers. It’s matching the speakers, and it’s an amplifier that can match with future, larger, more expensive speakers if you choose to upgrade.

Mark at Reno HiFi may have a used/demo unit that will save you money.

Why not call him and see if a home audition or purchase with return is possible?

What do you have to lose?

Blue Circle was another excellent solid state alternative. The amps sounded very "tube-like" without being bloated. Blue Circle is out of business, but the owner of Blue Circle, Gilbert Yeung, is designing amplifiers for Bob Neill’s Amherst Audio. The 022i-GY is an integrated amplifier to consider... (but admittedly a small circle of potential future perhaps tough to re-sell...unlike Pass Labs). If you go to RMAF in October, I recommend spending some time in the Amherst Audio room.

@hilde45, it seems to me you received rather poor service. If it was me, I would not return to that store.

The QS integrated amplifier (20 wpc) should be able to produce 96db with 16 watts into the 84db Dynaudio loudspeakers, so it’s not underpowered, but the impedance match might not be ideal depending on the impedance curve of the 6 ohm Dynaudio loudspeakers, although the QS integrated amp specs state output of 20 watts into any load 2-8 ohms. However we don’t know how the power output changes along a uneven impedance curve. What you would hear is an unbalanced sound...weak bass, or missing midrange, or shrill highs, etc.

I’m not familiar with Atoll, and I cannot find any specs for the integrated amplifier.

If you are seriously considering tube amplification, I suggest looking at more efficient loudspeakers with at least 8db efficiency and with as flat an impedance curve as possible. Also, look at tube amps with choice of output taps: 4 ohms, 6 ohms and 8 ohms (or some combination of those).

If you prefer the sound of the Dynaudio loudspeakers, then I suggest solid state amplification, and I again refer you to Pass Labs.

 I've come across running very low efficiency speakers (low as 82db @1w/1m) with high impedance 8-16ohms (not 4 ohms), and yet those speakers can still work fairly well with with low power tube amps. Or, as long as the related 8ohm and 16ohm speaker taps are available on the amp.
That's interesting. I would think a low power tube amp would not drive 82db speakers to decibel levels approaching a live performance, but perhaps to levels sufficient for some listeners.

Of course, the actual wattage of that low power amp means everything. One person's low power may be another person's muscle bound beast. LOL.
@tvad  I got the Harley book yesterday, and already created a "cheat sheet" to take with me during my auditioning today, along with a range of music. Amp power, character, difference to look for between tubes/solid state … I'm ready!

I found the chapter(s) about calculating decibel watts for a given speaker efficiency (well explained by @Almarg in this thread), and also the importance of impedance matching preamp to amplifier very helpful. It definitely led to positive results in my system.

Good luck in your audition.
If I could have another session which had the virtues of tubes (a variety of virtues, I’m not trying to oversimplify) but which contained a bit more of the crisp, tight, control of solid state, I’d probably be ready to go all tube right now.
What you describe is precisely what Pass Labs solid state amplifiers deliver. You might look into a Pass Labs XA-30.8 (or earlier XA-30.5). They’re magic. Truly.

Reno HiFi offers very generous home auditions.

Yes, the price point is a little more than you were considering...but an XA-30.8 can be found for around $4200 from a dealer (or less from a private party).

Pass Labs also makes an excellent integrated amp, the INT-60, for around $5200 used/demo (but IMO, the XA-30.8 is where it's at).

Something to consider...
@hilde45, fifteen years ago I was on the same journey as you’re now on. I was interested in adding tubes to my audio system, and began with a tube preamp. It was nearly impossible to audition components, so I purchased used and re-sold. Over and over again.

The reason I’m writing this is post is to share what I learned after many tube preamps rotated through my system...

What I learned, according to my ears and others’ who have gone through the same process, is that the magic of tubes in an audio system lies with tube amps. Not with tube preamps (although a tube preamp can be a wonderful addition).

Tube amplification is where the magic lies.

Once I discovered a perfect marriage of tube amplification and loudspeakers, then the rest fell into place. After owning nearly 12 tube preamps, I ended up with hybrid passive preamp. That system has remained unchanged for almost 10 years.

Sorry to somewhat sidebar your focused quest for a tube preamp, but I thought my journey was pertinent, and offers a potentially valuable lesson.

PS - While it is 8 months away, you have a tremendous listening resource in the Rocky Mountain International Audio Fest - October 2-4, 2020
Tube equipment can sound very close to solid state, or it can sound soft and bloomy, or anything in between. Your experience today barely scratched the surface, so don't judge all-tube amplification based on what you heard today.

With your solid state amplifier, a low output impedance preamplifier will match best...resulting in better bass control.

The aforementioned Modwright gear approaches a solid state sound. It matches well with solid state gear. I know from experience Lamm Industries preamps also match well with solid state. A used Lamm LL2 Deluxe would be in your price range.
Impedance matching is critical for optimal sound when pairing a tube preamp with a solid state amplifier. 

I strongly encourage you to read the applicable chapters in "The Complete Guide to High-End Audio" by Robert Harley.

Do some homework, then you'll have a better foundation for a tube preamp decision.