If you're getting sufficient level now, I don't see any benefit to adding a SUT. If anything, the added gain may result in distortion.
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You don't say why you are thinking about adding a SUT to this system. That would help. Also, as a rule you don't match a SUT to the TT. The TT doesn't give a hoot what SUT you choose to use, and vice-versa, but I understand in this case that the Bob's Devices SUT can sub for the VPI cable junction box. (Couldn't any SUT do that?) Anyway, your Cadenza Black makes 0.3mV (at 1kHz at standard velocity) and your Fosgate is said to provide 60db of MC phono gain. That's a 1000X increase in voltage gain. So that means the Fosgate feeds 0.3V to the Unison Research amplifier. Most integrated amplifiers do not provide much if anything in the way of linestage gain, so I guess the total signal voltage to drive the amplfier section is 0.3V. I cannot find the input sensitivity of the UR amplifier section, but 0.3V is in general a bit low to drive a typical amplifier to full output. So, can it be that your sound is a bit lean? Is that why you are thinking about a SUT? In any case, if the sound is a bit lean and you are turning up the volume control to achieve anything near satisfying levels, then yes, you might be better off with a SUT driving the MM stage of the Fos.
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Your Fosgate has 60db of gain. Enough for most of the popular MC carts.
Former owner of one for 12 years- great phonostage. Get a different cart for a different "sound" Also a longtime VPI Classic user
If you're seeking dramatic improvement dump the VPI/Fosgate and open the wallet wider.
You will hear less tube rush at high volume with SUT-MM setting if you're the type that listens for it.
Needless expense, IMO.
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lewm: Your math is off! The Fosgate mc stage amplifies the signal about 10X. So .3 mv becomes 3 mv. That is enough for a typical phono stage. You didn't figure in the gain of the Fosgate preamp's line stage. Most line stages can output several volts. Plenty to drive power amps, which typically need 2 volts for full output.
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Jason, I don’t know where to begin. But 60db of gain provided by the MC stage in the Fosgate equates to a 1000X voltage gain, and a 10X gain that you claim would be insufficient for any phono stage ever. 0.3mV multiplied by 1000 = 0.3V
Also, I didn’t figure in the gain from the linestage because I cannot find any information on that and because most integrated amplifiers don’t add linestage gain. So I’m guessing the linestage (which is probably just a volume control ahead of the amplifier input stage) adds no gain. To support that assumption I found that the UR has only one tube that drives its mosfet output stage. That leaves no gain device available for any sort of linestage gain.
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No need to spend $1750 on a Bob's SUT! I have five SUT's. My Bellari is a favorite! Only $350! It sounds excellent with my Denon 103R!
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The typical mc stage magnifies a mc cartridge voltage by a factor of 10. So .3 mv becomes 3 mv. Adequate for the typical phono stage, which I assume the Fosgate has. I am sure the Fosgate line stage can output several volts. So plenty of volts to drive a power amp.
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Most mc stages amplify a mc cartridge's voltage TEN times for use with a typical phono stage! So .3 mv becomes 3 mv (.3 x 10 = 3).
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Most integrated amps have an active line stage which adds gain. At least the older ones do! I guess the single tube driver for the output stage of the Fosgate adds gain. Otherwise it wouldn't have enough voltage to drive a typical power amp.
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".3 x 1000 = 300!"
Not when you're talking millivolts.
"0.3mV multiplied by 1000 = 0.3V"
@lewm is correct.
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Luckily I enjoy my vinyl system as is...but I appreciate any ’tweaks’ / upgrades that work. Thank you for our group conversation / education on maybe adding a SUT.
FYI My Unison Research ’"Unico" integrated amp is the first version sold, with 2 tubes and a wireless remote. Volume Level 4 out of 10 is enough for me. I upgraded the tubes to Mazda’s PLUS had two levels of modifications done - they clearly improved the overall quality, detail and soundstage of the audio to me: https://6moons.com/audioreviews/unison2/unico.html.
Unico Mods:
- Three sheets of SoundCoat chassis damping material to the inner chassis
- 2 premium mil-spec, ultra low noise/microphony Mullard CV4003/12AU7 designed for 10,000-hour operation
- Two Multicap PPFXS polypropylene film and tin foil inter-stage coupling capacitors
- Two 1uf Auricap metallized polypropylene preamp input coupling capacitors
- Twenty Japanese Riken 0.5- and 1-watt signal path carbon resistors with gold-plated leads
- Two feet of DH Labs Revelation Series pure 99.999% silver solid-core input signal wire with Teflon tape-wrap dielectric
- One pair of premium Vampire direct gold-over-copper-plated RCA female jacks
- Four WBT 0763 single output binding posts
- TRT WonderSolder used throughout
- 8 Vishay-Telefunken SF4007 ultra-fast soft recovery diodes to rebuild two existing bridge rectifiers
- 6 Black Gate electrolytic capacitors to the power supply
- Two custom-made Burr-Brown OPA-627 opamp-based PCBs to dramatically upgrade the amp driver stage
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Jason, do you really believe this?: "Most mc stages amplify a mc cartridge’s voltage TEN times for use with a typical phono stage!" Because most MC gain stages supply at least 60db of gain to the signal, and frequently much more than that, which counts for a lot because "db" is a logarithmic quantity. For example, 66db is equal to twice the gain seen with 60db or ~2000X increase in signal voltage. So the baseline 60db (which is what the Fosgate happens to supply) is equal to a 1000X gain in voltage. There are numerous on-line calculators you can consult, if you insist upon your particular belief system. It’s OK to be in error, but once the facts are given you, accept them. And as far as your pointing out that 0.3 X 1000 = 300, that is correct, but you left out the units: 0.3mV X 1000 = 300mV = 0.3V
Furthermore, like I said above, if MC gain stages could supply only a 10X increase in cartridge gain, the analog signal chain would not work; "3mV" that you propose to be the result of multiplying the cartridge output times 10 would not even drive an active linestage, let alone any amplifier. And I gave you the reasons why I think the Unison has only a volume control for a linestage ahead of the amplifier section.
Vinylfun, The version of the Unison Unico that I looked up (in the context of a Stereophile review) has only one tube, a 12AX7, instead of two 12AU7s. In either case, the tube input stage drives a MOSFET output stage, so far as I can tell. In your amplifier, one of the two 12AU7s may be used as a cathode follower, which adds no gain. In the review, there was no mention of an op amp. I imagine it is used for phono, if the Unico has the optional phono section, but I certainly could be wrong.
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Vinylfun-As lewm has pointed out, based on specs-60db/.3mv into your integrated may be on the low side for maximum performance.
The lowest I have used with the Foz was .4mv-into an integrated(no additional gain)just how much dynamic performance lost is not known since I have no reference
vinylfun states being currently satisfied but, obviously curious.
For the price of a decent SUT/IC's, a nice .5mv cart can be had for less along with less hardware clutter and additional "stuff" in the signal path.
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For only 60db gain, I'd want a cartridge with a bit more than 0.5mV output. And tablejockey, I am sure that was a typo but my point is that 60db gain from an 0.3mV source gives 300mV or 0.3V.
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Lewm, SUT's typically amplify the sub-millivolt output of a LOMC cartridge by 10 times. So my Denon 103R's .3 millivolt becomes 3 millivolts from the secondary of the Bellari SUT. Enough to use with most phono stages. My math is correct! I bought my first SUT in 1978 - a Mitchell Cotter P Type.
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Tablejockey: I don't know of any LOMC cartridges that output .5 mv. Anyway, that is still too low to use with a typical phono stage which needs a minimum of 2 mv and a maximum of 5 mv. Maybe you are thinking of a high-output moving coil cartridge like my Dynavector 20A which has 3 mv output so it doesn't need an SUT.
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Lewm, The typical phono stage adds an additional 40db to the SUT's 32db gain. So plenty of voltage to drive a line stage.
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Getting back to the topic at hand...
OP, please don't take offense, but IMHO your VPI will sound better with better full-range 100% passive speakers.
For reference, I've owned BP2000's and Mythos ST-L's.
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o@vinylfun By adding a SUT there is also the addition of a Richness of Tonality.
Bob's Devices use Tranx that I believe will be ones that produce the lower on the scale Richness of Tone, as I use similar Cinemag Tranx' myself I can offer this as a a assessment of the end sound.
If the risks associated with adding Richness of Tone are wanted to be avoided, the use of a Head Amp, the ones I have experienced in comparisons, will create a End Sound that in comparison to a SUT, does not create a detectable Richness to the Tonality.
I have one Phonostage I prefer the Head Amp in place of the Built In MC Input and a SUT as the Option.
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Pindac: In addition to my SUT's I have a Marcof PPA-1 head amp for use with LOMC cartridges. It is battery-powered and has a wider bandwidth than any transformer.
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Jason, you might review your own early posts here. You consistently stated that an MC phono stage adds 10X gain. Now I see that you meant to say that a SUT typically adds 10 X gain. If so, ok.
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