2. amps-preamps
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Need suggestion on VTL TL-5.5 tubes

I've been using TL-5.5 preamp and I like it a lot. Recently I'm trying a different amp, which has much higher gain than the current amp, and noticed I'm hearing a lot of background noise now. The source of the background noise turned out to be my preamp. With preamp off, or out of the chain, there is no noise. My speakers are 93dB efficient, and the new amp has about 25dB of gain. The background noise is loud enough it's heard/felt at the listening seat at 8 ft away. It's clearly heard about 1 ft away from the speakers.

I really like my preamp and I'd like to keep it if possible, but I must eliminate the noise. I'm not sure if the noise is due to aging tube or other part of the component, or simply noisier nature of tube gear. My questions are:

Are there other TL-5.5 users with sensitive speakers that can comment on how much noise they are hearing? It's also dependent on the gain of the amp, as with my previous amp with 15dB of gain I don't hear ANY noise even when ear pressed against the tweeter, maybe except for slight hint of hiss.

Should I try new set of tubes? If so, any recommendation on 12AX7 and 12AT7 with very low noise floor?

Third question, somewhat tangential to the issue is the need to reduce overall gain. The useful range of volume knob is now from 0 to 10 o'clock. It needs fine adjustment by hand and it's not feasible to use remote control any more. Is it possible to reduce the gain on the preamp with a different set of tubes?
jylee
cheesehead
16 posts
 
I just received my 5.5 back from VTL with the V3 upgrade, and with it was a new set of o.e.m. tubes (jj tesla).
I let her burn for about 100 hours and then pulled the tubes, put in a nos set of RCA gray plates, which I prefer sonically, but was suprised to hear how much quieter they are. The back ground was nice and black with either set, but the RCA's can't be heard @ 1 foot away through my signature 185 mono's and 102db speaks.
jylee OP
306 posts
 
Cheesehead, did you replace the tubes with the same types, or have you tried different type of tubes in 5.5? I've ordered a pair of NOS JAN Philips 5751 and two pairs of EH 17AY7 hoping to reduce the gain on the preamp. If that works out well I'll try higher quality tubes.
cheesehead
16 posts
 
Yes,
except the 12AX7A's are now suffixed with AW. Wasn't concerned enough to see what the extra charecter meant.

The 12AT7's are just that.

I have had good luck @ audiotubes.com.

Brent Jesse has been very trustworthy to deal with. My local dealer gets run of the mill tubes but really doesn't deal with some of the older stuff.

I had tried the mullards, other clich'e makes, and a few garden varieties before settling in on the RCA's.

Being so subjective to begin with, and every other system charecteristic affecting the way they sound, it's best to do what you ar doing and sample till your hearts content.

Godd luck, and enjoy it, its a gem.
ha_ha_he_man's avatar
ha_ha_he_man
5 posts
 
Cheesehead,

What is the V3 upgrade? I have an earlier version 5.5 (has the 12ax7/12at7 and the pot's on the preamp PCB) and was wondering what the difference in sonics is. How much was it and how long did it take?

Regards
Alx
jylee OP
306 posts
 
I've spent last couple of months tube rolling. I just replaced the 12AX7 input tubes and left 12AT7 alone. I tried the following.

JAN 5751
Telefunken 12AX7 ribbed plates
RCA 12AX7 Wurlitzer branded
Philips Miniwatt 12AX7

RCA tubes are remarkable. It's must more quieter than any of the tubes I've tried. The tonal balance is more on the neutral side. It's not as tubey or mellow as others, but crispier and cleaner. There is still plenty of midrange bloom, and the tubed sound is unmistakable. Very happy with the result, especially the lowered noise floor.
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