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Post subject: Fender Hot Rod Deluxe III and 12AT7 tubes in V1
Posted: Wed Aug 26, 2015 9:39 am
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Joined: Sun May 22, 2011 5:06 am
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Greetings,

I really like my HRDIII with stock 12AX7 preamp tubes, but out of curiosity I wanted to try putting a 12AT7 in V1 to see how it effects the amp (since I mostly play at low or medium volume in my band).

I ended up trying two separate GT12AT7 in V1 and both of them seemed to be (what I guess is) 'microphonic.' They both produced odd 'ringing' overtones, and would make them even when I knocked on the top of the amp cabinet.

My question is: Does this amp (specifically the one that I own) just not like 12AT7, or should I try another tube?

No big deal either way, the 12AX7s are fine. This is just a curiosity thing.

Thanks.


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Post subject: Re: Fender Hot Rod Deluxe III and 12AT7 tubes in V1
Posted: Wed Aug 26, 2015 9:51 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
Try another tubes or brand


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Post subject: Re: Fender Hot Rod Deluxe III and 12AT7 tubes in V1
Posted: Wed Aug 26, 2015 3:02 pm
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Joined: Tue Jun 29, 2010 1:20 pm
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Location: Indiana
IMO, the 12AT7 is better suited to the V3 position (PI). Try a 5751 (or even a 12AY7) in V1, a 12AX7 or 5751 in V2, and a 12AT7 in V3. :idea:

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Fender Hot Rod Deluxe III and 12AT7 tubes in V1
Posted: Sat Aug 29, 2015 2:04 am
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Joined: Sun Jan 30, 2011 2:35 pm
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I have a Blues Deluxe Reissue.
After a lot of research on preamp tubes, I use the following combination.

(V1)-5751 -- (V2)-5751 -- (V3)-12AX7

I'm sure that this combinations would work well in a Hot Rod Deluxe.
Check out the following article:
http://www.recycledsound.net/14_Phase_Inverter.pdf
V3 is your "Phase Inverter".

In V1, going from a 12AX7 to a 5751, reduces front end gain (from 100 to 60-70), and provides more clean headroom.
I advise not going down to a 12AY7 (gain of 40). in V1, as gain is reduced way too far.
If you consider going from a 12AX7 to a 12AT7 in the Phase Inverter (V3), I recommend the following combination:

(V1)-5751 -- (V2)-12AX7 -- (V3)-12AT7

As the linked article notes, a 5751 and 12AX7 are much more closely related than the 5751 and 12AT7.
A 12AT7 is not recommended in a first gain stage (V1) for sound reasons (as you experienced).
If you want to drop front end gain use a 5751.

There is also no need to pay tube suppliers to "match" preamp tubes.
Only power tubes need to be "matched".

I also recommend 6L6WGB "matched" Power Tubes biased at 65 to 70 at the bias contact point on the Hotrod chassis.
These tubes provide a warmer sound with earlier break-up, and are safe to use as a 6L6GC replacement.
The lower bias for the 6L6WGB Power Tubes will provide increased tube life and provide a nice warm sound that I like a lot better than 6L6GC Power Tubes.


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Post subject: Re: Fender Hot Rod Deluxe III and 12AT7 tubes in V1
Posted: Sat Aug 29, 2015 6:28 pm
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Joined: Tue Jun 29, 2010 1:20 pm
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MickJagger wrote:
...(V1)-5751 -- (V2)-12AX7 -- (V3)-12AT7...


This is what I use in my HRDlx I. 8)

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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