Tub pre amp/solid state amps

[vinny]

I was told tube pre amps work well with solid state amps. Is this true ? I'm about to try a marantz 7c with dual omkyo m504's. Any suggestions ?

[pivot]

Tube preamps were often designed to work into the higher impedance of tube amp input stages.

What is the input impedance of the Onkyo power amps?

Too low an impedance could cause a roll off in the bass.

[duficity]

tube preamps are often used with SS amps to get a warmer, more liquid sound, especially in the mid/hi range. But the bass is better controlled with a SS amp

[Coffee Phil]

I would guess that a Marantz 7 would be a joy with nearly any good amp however there is an issue with tube preamps of that vintage. In its day it was expected to be paired with a tube amp. The warm up time of the power amp would be comparable with that of the preamp. A solid state amp will be ready to go well before the preamp is warm. Since the designers of the vintage preamps did not have to be concerned with the power amp amplifing the turn on and warm up transients of the preamp they may not have worried much about keeping them under control. Unless you provide for a "head start" for the preamp to warm up and stabilize before turning on the PA you may have a bit of excitement watching your speaker cones during turn on.

Phil

I was told tube pre amps work well with solid state amps. Is this true ? I'm about to try a marantz 7c with dual omkyo m504's. Any suggestions ?

[aardvarkash10]

aieee aieee...

The Marantz uses a cathode follower output stage. While not extraordinary in its output Z by todays standards, it will be ok feeding into any competently spec'ed modern SS amp.

Of course, if your amp has an input Z in the low 1,000s of ohms, there may be an issue...

[watercourse]

I've had my tube pre (with a switchable 90 or 3.5K ohm output Z) paired with 3 SS amps (Class D and AB), as well as tube amps. Having such a low output Z on hand really makes it easy to match with a wide variety of amps.
Interestingly, my last class D amp and a current tube amp have input Z of 10K ohms. This is somewhat low, and may not match well with a lot of tube pres with higher output Z than what I have. They did not match with my pre at the 3.5K ohm output Z setting without losing some low frequency response; very audible in fact. I believe that the rule of thumb is 10:1 input Z/output Z.
My current Pass amp has an input Z of 30K. It takes about a half hour to warm up, just like my pre.
But the bottom line is: Yes, tube pres with SS amps work just great, it's all about synergy. I like all tube, but agree that the bass quality of SS amps are better in general. Go for it!

[vinny]

Hey guys !, this thing is awesome ! just looking for some advice. first day it was everything and more, 2nd time listening it lacked midrange and specialy lows. it was very crackly, thought it was the records till i put a brand new one in that i knew sounded good. sounded like it was scratched to hell between songs. sounds very thin. do i change the tubes ?

[jake]

What about the reverse situation, SS pre and TUBE amp? Which would be preferable, in general, or does the balancing out prevail either way?
My tube pre recently failed (Dyna PAS3), and I threw in a backup NAD 1240to manage my Marantz 8b. The detail seems to have improved, but the highs are harsh.
Would the ideal sound be the Pas-3 tubes pre and a SS amp?

[watercourse]

Hey guys !, this thing is awesome ! just looking for some advice. first day it was everything and more, 2nd time listening it lacked midrange and specialy lows. it was very crackly, thought it was the records till i put a brand new one in that i knew sounded good. sounded like it was scratched to hell between songs. sounds very thin. do i change the tubes ?

I would check the tubes. When was the last time you used it? Might need a going over just to be safe.

@ jake - I wouldn't generalize that one pairing is better than another per se. That's why I have a tubed pre but SS and tube amps. It's all about synergy. And the tubes you're using impact the sound quite a bit as well. I've tried also tried a passive pre with SS and tube amps, and found performance differences too, in particular loss of drive/energy, but might mainly be based on input Z yet again.

[pivot]

My tube pre recently failed (Dyna PAS3)...

What failed in the PAS? Any mods/updates? In my experiance the usual point of failure in a PAS is the selenium rectifier in the heater supply. Unfortunately in the stock PAS, which has no power fuse, the failed heater supply usually burns out the power transformer. Minimum mod for a PAS is a pair of modern diodes to replace the selenium rectifier and a 1 amp regular blow fuse in the power line. "Been there, done that have the tee shirt" as the saying goes.

There a number of web sites out there with PAS updates and mods. Even replacment transformers, if you need one, are not that expensive.

By the by the, ST-70 has a selenium rectifier in the bias supply. REALY reccomend changing that out and there are a number of parts kits out there for that. Think about one of the kits to replace the PS quad cap at the same time too.

[pivot]

Hey guys !, this thing is awesome ! just looking for some advice. first day it was everything and more, 2nd time listening it lacked midrange and specialy lows. it was very crackly, thought it was the records till i put a brand new one in that i knew sounded good. sounded like it was scratched to hell between songs. sounds very thin. do i change the tubes ?

The 7C is a veteran piece for sure. First thing I would do is pull the tubes and clean pins and sockets. Caig Pro Gold GX5 is made especally for high temp tube circuits.

Once cleaned and back together CAREFULLY measure voltages at the circuit test points. Keep in mind tube gear runs at high voltages that can be dangerous TAKE THIS SERIOUSLY.

There might be a solder connection that has gone intermitant with age OR there could be a PS cap that has aged out. Checking voltage should find these failures. My bet is a cleaning will do it.

If the crackles are both channels this points to a power supply issue. The small signal tubes in a vintage preamp are run fairly conservatively and are usually withn specs for decades of use.

[jake]

Thanks Pivot, my PAS3 is heavily modified, so now I'm guessing you're right about its repair being a diode burnout. It sort of popped when I accidently turned it on and off real quick twice. Usually I need a new fuse in that situation, but the PAS3 has no fuse.
I like the NAD 1240 preamp detail and manners and also the adjustable load, but I am missing a lot of headroom and soundstage I had with the Dyna, must get it back.

[Larry I]

As a rough rule, tube preamps are far more unpredictable when it comes to matching with any particular amp--tube or solid state. One cannot easily characterize the sound of the preamp and expect that character to follow with a different amp. Most solid state preamps can be roughly characterized after hearing them in two different systems.

That said, a mix of the two CAN be very good sounding. It is just that I would caution against expectations that either the tube preamp or the solid state amp can compensate for the characteristic of the other to get the best of both worlds (it is more likely one would get the worst of both worlds). The particular prospective matching must be tried out.

There is one practical issue that should also be considered. I find that most solid state amps take quite a while to warm up to sound their best (much longer than it takes tubes to warm up), but, given the lower current draw at idle, one can justify leaving the solid state amp on all the time. Given the limited life of tubes, I would never leave a preamp or linestage on all the time. In a hybrid system one would that would mean having to turn the preamp on and off while not turning the solid state amp off first. There are some tube preamps that put out some pretty loud and nasty sounds when being turned off and/or on. If the linestage is prone to making that kind of noise, one would need to have an effective muting mechanism if one plans to only turn on/off the preamp.

[duficity]

I just bought a Musical Fidelity M3 Nuvista integrated amp that uses nuvista tubes in the preamp and ss in the amp side. very nice open, slightly warm through the midrange, clean but not bright and very strong, clean dynamic bass. I would say the tube/ss match works very well.