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swapping preamp tubes for less gain

 
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Lumpy Waters
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Joined: 12 Oct 2013
Posts: 14
Location: California

PostPosted: Thu Nov 14, 2013 2:05 am    Post subject: swapping preamp tubes for less gain Reply with quote

I've been looking at the Randall RD1C, 1 watt tube combo amp with an effects loop and speaker emulated line output. I need a low power bedroom/recording amp. I don't need or want built in modelling effects gee-gaws, programming, USB etc, I've got a pedal board that can do all the effects I need and a Steinberg computer USB audio interface and ART tube preamp setup for recording to my computer. I like this Randall amp for the F/X loop, low watts, and the XLR speaker emulated output- those are just what I need and not so common all together in one amp- but this amp is way gainy with almost no clean headroom, and I need more clean. The only review on youtube (for the head) has it starting to breakup with the volume at 4. So I'm thinking maybe I could swap out the 12AX7 preamp tubes for 12AT7 or 12AU7 tubes and hopefully get a little more headroom out of the preamp. Anyone that has done this on other amps, does the idea sound reasonable or is it hopeless since this particular amp is obviously voiced for primarily distortion?




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Gabriel
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Joined: 11 Apr 2010
Posts: 3148
Location: NYC

PostPosted: Thu Nov 14, 2013 2:10 am    Post subject: Reply with quote

Maybe look at an amp voiced for what you're wanting to play. I've been down this road trying different preamp tubes to get an amp to sound vaguely how I wanted but in the end just sold the amp and bought something more suited to what I was originally searching for.
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johnnyseven
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Joined: 03 Jun 2007
Posts: 3996
Location: London, England

PostPosted: Thu Nov 14, 2013 12:11 pm    Post subject: Reply with quote

Isn't the idea behind getting a 1 watt tube amp so that you can have lovely tube break up sounds at low volumes? I would go with Gabriel's suggestion and start looking for another amp if you want a louder clean sound.
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dub
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Joined: 20 Aug 2008
Posts: 1485
Location: WGTN, Aotearoa

PostPosted: Thu Nov 14, 2013 12:13 pm    Post subject: Reply with quote

You could plug straight into the loop, bypass the preamp. You'd need something to bring up the signal possibly, a boost, although at one watt, you might still drive the poweramp into breakup?
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George
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Joined: 03 Jul 2009
Posts: 20477
Location: UK

PostPosted: Thu Nov 14, 2013 12:41 pm    Post subject: Reply with quote

i thought changing preamp tube types just made it quieter because they have a lower overall gain? i don't personally know because i've never experimented.

maybe a more efficient speaker may help with headroom? 1W tube at full bore is still very loud for a bedroom
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GreenKnee
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Joined: 29 Oct 2009
Posts: 573
Location: Sheffield, England

PostPosted: Thu Nov 14, 2013 6:44 pm    Post subject: Reply with quote

I changed the preamp tubes in my 212 DeVille to 12AT7s as I'd heard it gave more clean headroom. I read it on here http://www.justinholton.com/hotrod/ but that link's died now, sadly. It basically says that doing this does what you're looking for. Results will vary with different amps I imagine, but I managed to get quite a bit more volume without breakup than with the 12AX7s.

I also biased my amp a little cooler, which means the power tubes aren't working quite as hard. I imagine this has greater effects than changing the preamp tubes, so if possible try that.
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Josh
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Joined: 17 Nov 2008
Posts: 4641
Location: George

PostPosted: Thu Nov 14, 2013 10:51 pm    Post subject: Reply with quote

aww. that's sad. I was on that site just recently actually. really helpful site too.
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