Runaway volume on tube preamp

[muypogi]

Just bought a really nice tube preamp from a fellow forum member. Was listening to it at slightly past the 12 o clock position and somehow the volume suddenly went up on both speakers. I shut it down and nothing smelled burnt, except for the smell of hot tubes. I turned it on again and everything seemed fine, though I did it at a lower volume level.

The preamp is an Audible Illusions Modulus 2A. It's a pretty old preamp, but when I listened to it, it greatly improved my system. I'd like to ask fellow tube guys if this is just a case of me pushing an old preamp too hard, dapat dahan dahan muna? Just bought a new set of tubes, 4 matched 6922s.

ANy ideas? Should I bring it in for a checkup?

No intention of selling it though. I heard what it can do and its a keeper.

[arnoldc]

Could be the wiper of the potentiometer is damaged. Alpe blue is less than 1k lang.

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[muypogi]

Could be the wiper of the potentiometer is damaged. Alpe blue is less than 1k lang.

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Pwedeng contact cleaner muna?

[muypogi]

Could be the wiper of the potentiometer is damaged. Alpe blue is less than 1k lang.

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Pwedeng contact cleaner muna?

Actually, the volume increased without me touching anything. So, it may not be the potentiometer. . . Somthing else?

[zetroce]

Moi, i believe those are new tubes. Give it time to fully bloom. Maybe your experience was because of the tubes just starting to heat up that's why it appears like volume was pumping up by itself. I don't think it's a potentiometer issue as well 'coz that's mono-mono. Did you experience that with the old tubes? If not, then you can focus on the new tubes 'coz that was the only new thing introduced in your pre-amp system.

[muypogi]

Moi, i believe those are new tubes. Give it time to fully bloom. Maybe your experience was because of the tubes just starting to heat up that's why it appears like volume was pumping up by itself. I don't think it's a potentiometer issue as well 'coz that's mono-mono. Did you experience that with the old tubes? If not, then you can focus on the new tubes 'coz that was the only new thing introduced in your pre-amp system.

Got that. Lrt me try again tonight. . .

[Mamimili]

AA preamps have a reputation for eating tubes.
I have had similar experiences with "more expensive" tubes but with cheap Sovteks everything stays "normal".

Do you have the AA manual? If so stay with the tubes they say are proven, i translate that to long lasting!

[arnoldc]

Tubes don't increase volume on their own

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[highlander]

Moi, i believe those are new tubes. Give it time to fully bloom. Maybe your experience was because of the tubes just starting to heat up that's why it appears like volume was pumping up by itself. I don't think it's a potentiometer issue as well 'coz that's mono-mono. Did you experience that with the old tubes? If not, then you can focus on the new tubes 'coz that was the only new thing introduced in your pre-amp system.

Agree with Dong.....listening past 12 o'clock probably too loud if all is ok inside the preamp....(I also own an AI...listening at
9 o'clock meron mc phono nakakabit)
suspect a not so good contact in some of the tube pins?...heat improved contact thus the increased volume?
suggest plug-unplug the tubes...(from a not so technical guy )

hope this helps.....

[muypogi]

Thanks for the replies guys. Listened last night but made sure the tubes were warmed up for 45 mins or so. Tubes seem to be fine, except for tube 2 from the left having a slightly less radiant burn, but otherwise all of them seemed ok. All 4 tubes ba drive the preamp, or do tubes 3&4 drive the preamp section, withe rest driving the phonostage?

Sorry ha. Many questions. Wala pa yung manual and deadma yung audible illusions website.

[highlander]

Thanks for the replies guys. Listened last night but made sure the tubes were warmed up for 45 mins or so. Tubes seem to be fine, except for tube 2 from the left having a slightly less radiant burn, but otherwise all of them seemed ok. All 4 tubes ba drive the preamp, or do tubes 3&4 drive the preamp section, withe rest driving the phonostage?

Sorry ha. Many questions. Wala pa yung manual and deadma yung audible illusions website.

Yes, 2 tubes for the preamp (line stage) and 2 tubes for the phono...

[zetroce]

Thanks for the replies guys. Listened last night but made sure the tubes were warmed up for 45 mins or so. Tubes seem to be fine, except for tube 2 from the left having a slightly less radiant burn, but otherwise all of them seemed ok. All 4 tubes ba drive the preamp, or do tubes 3&4 drive the preamp section, withe rest driving the phonostage?

Sorry ha. Many questions. Wala pa yung manual and deadma yung audible illusions website.

Good to hear that Moi. Now you just sit down and enjoy the music.

[muypogi]

Thanks for the replies guys. Listened last night but made sure the tubes were warmed up for 45 mins or so. Tubes seem to be fine, except for tube 2 from the left having a slightly less radiant burn, but otherwise all of them seemed ok. All 4 tubes ba drive the preamp, or do tubes 3&4 drive the preamp section, withe rest driving the phonostage?

Sorry ha. Many questions. Wala pa yung manual and deadma yung audible illusions website.

Good to hear that Moi. Now you just sit down and enjoy the music.

Just to update, the amp's left channel's become "scratchy" and fades in and out. I don't think it was the tubes that caused the sudden rise in volume in the left channel, as I swapped them and the problem in the left channel persisted. Bad/worn out cap/resistor/volume pot perhaps? Will have it checked this week.

Not blaming the seller though, as I believe the amp was fully functional when I bought it. Maganda talaga tumunog, just as advertised. Malas na lang talaga since it is a 25 year old amp anyway. . . something had to give. On the bright side, maybe updating /changing the worn out parts will be a blessing in disguise. . . That means more years of listening pleasure with it. Stay tuned. . .

[hypertriode]

Moi, feel free to drop by at the shop anytime (+639277053960). Thanks!

[alexg]

Sounds like wiper of the potentiometer.

If so, ask Rene to replace with stepped attenuator or a TVC...