[dkd7]

After a few recommendations and searching, I found a very well kept VTL 2.5 but has the stock tubes. Upon first listening, the liquid, detailed sound of what I've been hearing all the talk of, was quickly apparent.

This will be used in place of a B&K Ref 50 but still feeding the B&K 200.2. The B&K gear sounds great, but this preamp takes it up a notch for sure.

I did notice a louder hiss/gain noise from the speakers, easily heard from 2-3 feet away. I had to get right up on the speaker to hear the B&K but granted that's a solid state pre. The sound from the VTL is very nice, a slight dropout in the midrange and just slightly bright...but the highs are smoother than the Ref 50 so it's not a simple trade off.

I did order some Mullard CV 4024/M8162 for the 12AT7 slots and not sure about the 12AU7 slots...that's where I'm searching.

I did also order some RCA 12AU7 grey or black tops since they were cheaper but other than that, I haven't ordered any more.

Still waiting on the other tubes for now, but any input on what other members have tried with this preamp is greatly appreciated.

Also, is the high gain noise normal? I understand tubes wcan be noisier that SS components but not sure how loud or quiet they tube pre should be.

[SteveFord]

I don't have that preamp but have heard good things about it.
You shouldn't have a whole lot of noise, though.  Sounds like a beat tube or two, you'll see/hear what I mean when you get some good ones in there.

[JakeJ]

I'm with Steve at this point.  Sounds like the tubes it came with are worn out.  You'll know immediately when you change them out for the new ones.

[dkd7]

Ok, I'll reassess it when the tubes arrive. Something I noticed just now when I moved my phono stage over to the side as its sitting above the preamp...was a static hiss sound when I lightly bumped the cover of the preamp. A very light tap will produce that light static sound in the speakers. So I assume that's the guts of the tube producing that.

[dkd7]

Something else I noticed, I was trying different inputs yesterday to see if the noise was the same. I thought I swapped the cables back to the CD position but I left them on TAPE. I turned the volume up with the CD on and it sounded like it was muted....turns out it's bleed through.

Actually it's a little louder than I would think...I didn't think there should be any. But clearly with the selector on a different input, I can clearly make out the music from the CD on other input selections. Granted it's not that loud but with the volume at halfway I can easily make out the song from the other input.

Is this normal or could be a fault of the worn tubes?

[nickd]

"Bleed through" is usually from circuit layout. Parallel wires or circuit board traces, lack of shielding on long low voltage wires etc. The manufacturer usually becomes aware of the issue after units are built and have begun shipping. When they re-design they fix some of the previous errors and omissions. I guess that's why the 7.5 is such a nice unit. Circuit evolution continues along with the consistent price increases. 

Hard to fix if it is from board trace or poor grounding layout. Might be worth checking the input stage for long (unshielded or parallel ) wires. That can be an easy fix if they run across the inside of the unit to the volume pot etc.

I would install a set fresh tubes. Power down your other sources during critical listening and listen through the quietest input (trial & error to find it) for long term satisfaction. 

[Rusty Jefferson]

1st adventure with anything new can be fun and frustrating at the same time.

The noise (hiss) you're hearing may or may not be bad tubes. There are factors including how efficient your speakers are, how much gain your amp has, and how much gain your preamp has. If you've been all solid state amp/preamp you've probably never had these noise issues.

My speakers are about 100db efficient, my amp (ss) has 28db of gain and my preamp (tube) has about 20db of gain. I can hear noise at 2-3 ft with even the quietest tubes.  As long as I  can't hear it from the listening position, I don't worry about it. I don't need a preamp with gain, but I like how it sounds (musically).

At this moment, I wouldn't get too worried about the crosstalk between inputs either.  See how the new/better tubes work out. If you aren't comfortable with the noise level, you likely won't be keeping this preamp.

[ACHiPo]

After a few recommendations and searching, I found a very well kept VTL 2.5 but has the stock tubes. Upon first listening, the liquid, detailed sound of what I've been hearing all the talk of, was quickly apparent.

This will be used in place of a B&K Ref 50 but still feeding the B&K 200.2. The B&K gear sounds great, but this preamp takes it up a notch for sure.

I did notice a louder hiss/gain noise from the speakers, easily heard from 2-3 feet away. I had to get right up on the speaker to hear the B&K but granted that's a solid state pre. The sound from the VTL is very nice, a slight dropout in the midrange and just slightly bright...but the highs are smoother than the Ref 50 so it's not a simple trade off.

I did order some Mullard CV 4024/M8162 for the 12AT7 slots and not sure about the 12AU7 slots...that's where I'm searching.

I did also order some RCA 12AU7 grey or black tops since they were cheaper but other than that, I haven't ordered any more.

Still waiting on the other tubes for now, but any input on what other members have tried with this preamp is greatly appreciated.

Also, is the high gain noise normal? I understand tubes wcan be noisier that SS components but not sure how loud or quiet they tube pre should be.

There will be tube rush (hiss), but what you describe seems higher than you should be getting.  Figure out from the manual, interwebs, or VTL which tube(s) are most important and spend most of your money on it (them).

Where are you from?  If you're in the US I would recommend checking out Andy Vintage Tube Services (best to call as he claims to be a month behind his email):
http://vintagetubeservices.com/
I just ordered my first tubes (12AX7s) from him, but he comes highly recommended and was impressed with his selection, prices, and the brief conversation I had.

I've also had good luck with Brent Jesse:
http://www.audiotubes.com/
Best to communicate with Brent via email, as he's hard to reach by phone.

Good luck and keep us posted.

[glynnw]

Tube rolling is great fun, but sometimes vintage tubes are noisy.  If that remains an issue, try some new JJ or similar and if available select the low noise option.

[DaveC113]

1st adventure with anything new can be fun and frustrating at the same time.

The noise (hiss) you're hearing may or may not be bad tubes. There are factors including how efficient your speakers are, how much gain your amp has, and how much gain your preamp has. If you've been all solid state amp/preamp you've probably never had these noise issues.

My speakers are about 100db efficient, my amp (ss) has 28db of gain and my preamp (tube) has about 20db of gain. I can hear noise at 2-3 ft with even the quietest tubes.  As long as I  can't hear it from the listening position, I don't worry about it. I don't need a preamp with gain, but I like how it sounds (musically).

At this moment, I wouldn't get too worried about the crosstalk between inputs either.  See how the new/better tubes work out. If you aren't comfortable with the noise level, you likely won't be keeping this preamp.

My guess is both the OP and you suffer from too much gain. I'd look into trying a zero-gain preamp and reduce your noise by 20 dB, you should be able to find something that'll float your boat and not have excessive gain...

My speakers are about 105 dB sensitive and with my tube buffer pre (-3.5 dB gain) and tube amp (+30 dB gain) my speakers are extremely quiet, I can't hear noise with my head inside the midrange horn.

[Rusty Jefferson]

My guess is both the OP and you suffer from too much gain. I'd look into trying a zero-gain preamp and reduce your noise by 20 dB, you should be able to find something that'll float your boat and not have excessive gain...

Dave,

Thanks for your critique of the problems with my system.  As I stated in my 1st post:

... I don't need a preamp with gain, but I like how it sounds (musically).....

I've tried passive/zero gain preamps and prefer (to date) my active tube pre. Again, being able to hear hiss from the compression driver at 2-3 ft doesn't bother my listening experience as I sit 6 ft from the speakers.

I realize too much gain could be the OP's problem, that's why I posted. Just to point out to him/her the tubes may not be the issue. For some folks, any noise is objectionable.

If you'd like to send me your preamp to demo, send me a pm. I'd be more than happy to demo it in my system, and have a double blind listening evaluation with members of my local audio club.

[JackD]

Rusty

Don't know if you have tried these or want to but they work very well in the situation you describe.  I have a pair of SE and balanced I keep on hand for use with amps like the Nuprime ST-10 or Job 225 with input sensitivities of .75 volt. 

http://www.rothwellaudioproducts.co.uk/html/attenuators.html

[Double F]

Congratulation on the VTL,  heard good things about them

You may have to roll a few different tubes to reduce the hiss.  They could be worn out.  Could be to much gain. 

Some tube preamps can take just about any tube and not complain, some are very sensitive.

I currently have a DeHavilland Ultraverve 3.  It is very forgiving of the 6SN7s I use with it.
My previous Rogue Metis Magnum was real tough to quiet down.  In fact many of the 6sn7s that were noisy in the Rogue are dead quiet in the DeHavilland.

Go figure.

No matter the noise I don't think I will ever go back to a SS preamp. 

[SteveFord]

It's been a while but I seem to recall shorting plugs taking care of the bleed through from my tuner on one of my preamps.
Maybe this would help?
http://www.takefiveaudio.com/mall/shopcontent.asp?type=RCA_Input_shorting_plugs

[dkd7]

I appreciate all the help and advice.....

The specs on the amp are:

Input sensitivity: 1.4V
Voltage gain 28
Input Impedance: 33.2K ohms


The VTL has 20 db of gain

My speaker sensitivity is 89.7 db.

I like the idea of the in-line attenuator, I wonder how much they may change the sound....could be worth a try.

Hopefully in a day or two I will have some fresh tubes, the JJ tubes in there now are at least 2 years old with unknown hours of use.

[JackD]

dkd7

I have used both the SE and Balanced Rothwell's on multiple amps and preamp combo's and have not heard any change in the sound. My speakers are over 90 db so in addition to the lower noise floor the increased range on the volume control was appreciated. 

[dkd7]

I have the preamp on a different set of speakers now, same type just larger. I changed the JJ tubes in the 12AT7 slots to Mullard CV4024/M8162 and the 12AU7 slots to RCA NOS 12AU7A ( https://www.tubedepot.com/products/12au7a-rca ). This combo reduced the gain noise or hiss a little, it's not really noticeable from the listening position.

Granted I only have about 10 hours on these tubes, I still had the Mullard NOS CV4003/12AU7 tubes on order and they arrived today. I've heard alot about these tubes and wanted to give them a shot so I put them in and I have 8 hours on them now.

I understand tubes need a little time to settle down, but right off the bat I noticed with Mullards in all 4 slots, the female vocals are great, but the piano is muddy. Maybe this is just the tube combo or that they need time to burn in, or both. I don't want to swap the RCA's back in yet as the CV4003's need more time.

Overall so far so good, this preamp really changed the dynamic of the music.

[SteveFord]

Unless it's simply for convenience not too people go back to a SS preamp after they give a tube preamp a shot.