What's More Important? Tube Preamp or Power Amp? Too Many Tubes? w/ Upscale Audio's Kevin Deal
What this covers
Kevin Diehl of Upscale Audio works through a series of practical and technical questions about tube amplification: which component—preamp or power amp—actually delivers the signature warmth and character people seek from tubes, whether tube rectification truly offers sonic advantages, and whether running many tube stages creates problems or merely requires acceptance of the gear's nature. His argument rests on evidence from guitar and bass culture, where serious players have long insisted on tube power amps rather than hybrid solid-state setups, and on technical specifics about rectification noise, output impedance, and circuit topology that contradict certain industry cost-cutting choices and consumer assumptions.
The discussion covers several distinct areas: the deliberate misdirection in some commercial designs (tubes placed in the signal path only to create a visual impression), the economics of tube manufacturing and why major manufacturers favor cheap solid-state rectification despite its inferior noise performance, the difference between all-tube and hybrid preamp designs, and concrete recommendations for phono stages when adding vinyl playback. Diehl also addresses the psychological dimension—whether anxiety about inevitable tube maintenance should discourage listeners from building systems with many tube stages—and touches on the broader business culture of high-end audio, where he sees tension between engineering integrity and cost reduction. The conversation includes specific equipment examples: the Ampeg SVT as proof that tube amps deliver bass, Pathos InPol amplifiers as an example of unconventional tube design, and hybrid preamps like the Audio Research SP-11 as a middle ground. A recurring theme is the importance of asking salespeople whether their recommendations serve the listener's needs or their own profit margins.
Diehl argues that for genuine tube sound a tube power amp is the foundational component (not a tube preamp), that tube rectification is actually quieter and superior despite cost-cutting by big manufacturers, and that 'too many tubes' is a matter of temperament rather than sound quality.
- Guitar and bass amp culture proves real tube tone requires a tube power amp, not a tube preamp paired with solid-state power
- Tube rectification is technically quieter than solid-state but cut by 'bean counters' to save pennies
- Tubes occasionally go noisy, so highly fastidious listeners should limit how many tube stages they run
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Some integrated amplifiers place a tube in the front window purely as a non-functional buffer to make buyers feel they have a tube amp, so upgrading that tube produces no audible difference because it is not doing anything in the signal path.
“that tube is a buffer it is not doing anything... it runs the signal through the tube but it's not doing anything at all”
Tube rectification is technically quieter than solid-state rectification but is more expensive to implement (a 5AR4 tube costs a manufacturer ~$25 versus ~10 cents for a diode), and big companies cut it to save pennies, contradicting the common belief that solid-state is quieter.
“tube rectification technically is quieter than solid state rectification but it's expensive to implement solid state rectification is a diode right 10 cents... tube rectification to put a 5ar4 tube in there that's going to cost a manufacturer maybe 25 bucks”
When someone answers gear questions for you, you must consider whether they are trying to sell you something; an honest seller gives the true answer rather than the most profitable one (e.g., always recommending a preamp).
“you got to remember when anybody's answering these questions for you you know are they trying to sell it right”
Hybrid preamps that use tubes for voltage gain and FETs to lower output impedance can sound very good, exhibiting some tube flavor combined with a direct sound (examples: Audio Research SP9, SP-11, Sonic Frontiers SFL-1 Signature).
“a hybrid means that you might have a pair of tubes for voltage gain and then you may have some fets or something similar to that to lower the output impedance of the preamp and that's a good way to go”
A tube power amp is more fundamental to achieving tube sound than a tube preamp, evidenced by the fact that serious guitar players insist on tube amps (Vox AC30, Marshall) rather than pairing a tube preamp with a solid-state power amp.
“any really good guitar player is going to talk about a vox you know ac30 or a marshall... they're not going to say no i really want to get the right tone from my guitar so i'm going to use a tube preamp along with a solid state amp it doesn't work that way”
A properly designed tube power amp delivers full bandwidth and excellent bass, contradicting the belief that tube amps lack bass — evidenced by the Ampeg SVT, the most iconic bass guitar amp ever made.
“a tube power amp properly designed should give you full bandwidth and amazing bottom end... what's the best the most iconic bass guitar amp ever ever made... it's the ampeg svt”
Big businesses entering high-end audio reduce costs to pennies and treat it purely as a business, which Diehl views as detrimental ('I hate it when bean counters get involved').
“some companies man they got this stuff boiled down to not the nearest dollar but pennies and that is the unfortunate truth about big business when they get into high-end audio”
An all-tube preamp using tubes for voltage gain, tube followers to lower output impedance, and tube rectification represents the purest, gold-standard tube preamp design.
“that is going to be the purest type of a tube preamp i mean real purity and i would say to you that that's really uh considered to be the gold standard”
Whether you can have 'too many tubes' is a matter of temperament, not sound: anxious, fastidious listeners with many tube stages (preamp, amp, phono) will be bothered when one inevitably goes noisy, so they should limit tube count, whereas it is simply part of the care and feeding of tube gear.
“can you have too many tubes well you can if you are wound too tight... if you've got 12 tubes here and 12 tubes here and six tubes in your funnel stage every once in a while one of them is going to go noisy”
Pathos InPol (inpull) amplifiers are a unique patented Class A design using one or two tubes for voltage gain feeding through large chokes into output devices run past their theoretical limits, producing an effect that 'almost ionizes the air with music.'
“it's a patented design where you have just one tube or actually two tubes giving you voltage gain and then it goes through these big huge chokes and then to these output devices that are running past their theoretical limits”
When adding a tube phono stage, prioritize a quiet unit, especially for very low-output moving coil cartridges (0.25–0.3 mV); good reasonably-priced options include the Manley Steelhead, Manley Chinook SE Mk II, Zesto Andros, and EAT E-Glo Petit.
“i would make sure that you get something that's quiet especially if you're going to get a funnel stage it's going to work with a crazy low output moving coil cartridge”
Modeling guitar amps that use DSP to mimic tube amps are dismissed by hardcore players as gimmicky and not 'real' tube tone.
“the hardcore guys they laugh at it they laugh at it they go oh god you know it's gimmicky it's fun but it ain't real”
Diehl's sales staff are not on commission, which he frames as ensuring honest, needs-based recommendations rather than pressure selling.
“my folks are not on commission i don't want that vibe i want you to have a good time i want them to listen to you and your needs and to be honest”
Video production quality improved because Kevin hired a degreed videographer.
“that's because i hired a true uh degreed videographer and we're making everything higher quality”