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Post subject: DRRI Tube Options
Posted: Sun Jun 07, 2015 1:45 pm
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I've had my DRRI for 3 months now and am loving' the tones available. But in true GAS fashion I am still seeking variation in tone. I am currently wondering if I can make it break up a little earlier.

I have read that a 12AX7 in the PI position will do that but does it also increase the amount of breakup? One option I am considering is to try a 12AX7 in V6 and to counteract any overall increase in gain this might produce put a 5751 in V2. I cannot really wind the amp up at home to test it before taking it out so would be interested to know what I might expect from this tube combination from anyone that may have tried it.


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Post subject: Re: DRRI Tube Options
Posted: Sun Jun 07, 2015 2:13 pm
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You can easily try this by swapping V1 and V6, then playing through the VIBRATO channel. Be aware that most Fenders that use 12AT7 in the PI section, run a higher idle bias --- than those amps using a 12AX7. The 12AX7 may become noisy sooner.

Tell us what you think of the swap.


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Post subject: Re: DRRI Tube Options
Posted: Mon Jun 08, 2015 1:35 am
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Best is to use speaker attenuator . Tubes replacement won't do what you want .


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Post subject: Re: DRRI Tube Options
Posted: Mon Jun 08, 2015 12:57 pm
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I did a little experimenting today. My normal pre-amp tubes are TAD 7025WA in V1 and V2, JAN Philips 12AT7WC in V3, TAD ECC83WA in V4, Groove Tubes GT-12AX7-R in V5 and Mullard CV4024 12AT7 in V6.

In V2 I put a JAN Philips 5751 and in V6 a Sovtek 12AX7LPS. I did not try the volume higher than 5 and to my ears there was no noticeable change in tone or breakup nor was there an increase in noise. I then put the Mullard CV4024 back in V6 leaving the 5751 in V2 and there was still no audible change in tone or breakup. Finally, I put the Sovtek 12AX7LPS back in V6 and put a Tung-Sol 12AX7 Reissue in V2 and still nothing changed significantly.

I have a Radial Twin City ABY switch and was able to quickly A/B between the Normal and Vibrato channels and for both the Sovtek and Mullard tubes in V6 I was able to adjust tone and volumes controls so that the I could get the various tubes in V2 to sound the same as the TAD in V1.

It may be that at higher volumes the differences would be more noticeable but after this little experiment I have left the Mullard CV4024 in V6 and the Tung-Sol 12AX7 Reissue in V2.


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Post subject: Re: DRRI Tube Options
Posted: Tue Jun 09, 2015 5:33 am
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stratele52 wrote:
Best is to use speaker attenuator . Tubes replacement won't do what you want .


Better than tubes or attenuator is a good overdrive effect . :wink:


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Post subject: Re: DRRI Tube Options
Posted: Tue Jun 09, 2015 6:07 am
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I have some excellent overdrive pedals including a Wampler Euphoria, Free The Tone MS-SOV, Fulltone Fulldrive 2 Mosfet, Maxon OD-9, Maxon OD808 and a Fredric Effects Golden Eagle (Klon clone). They all sound great but I always prefer to use them with an amp that is on the verge of breakup.


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Post subject: Re: DRRI Tube Options
Posted: Tue Jun 09, 2015 6:55 am
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fifty4, here's something to think about. A guy I know wanted his PR to OD early (in output stage) --- similar to volume you hear OD in a Champ.

He tried 6K6GTs. Good NOS are relatively cheap. Bias them to around 5-6 watts per tube. If your DR puts around 450VDC onto the anode plates, then shoot for 12-14 mA per tube. He like them.


Just a thought. :mrgreen:


http://www.ebay.com/sch/i.html?_odkw=6K ... T&_sacat=0


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Post subject: Re: DRRI Tube Options
Posted: Tue Jun 09, 2015 2:18 pm
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Thanks for the suggestion which I will keep in mind but that sort of technical adjustment it is beyond my capabilities so I would need some expert help.


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Post subject: Re: DRRI Tube Options
Posted: Tue Jun 09, 2015 3:54 pm
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BMW2002Ti wrote:
If your DR puts around 450VDC onto the anode plates...


I would regard such a measurement as highly unusual and start searching for the reason. The original design and all subsequent revisions are spec'd for 410 VDC.

Arjay

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Post subject: Re: DRRI Tube Options
Posted: Tue Jun 09, 2015 5:11 pm
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Another option you could consider is a less efficient speaker such as the Jensen MOD 12-50. Now I'm not saying it's a good speaker nor am I saying it's a bad speaker, I'm just saying it's a very inefficient speaker at 94.6dB/1W/1m. If your current speaker is say 99dB (you'll have to check specs) then you will have to turn up the amp's volume knob significantly to obtain the same perceived volume that you are used to playing at (for example, the 99dB speaker will seem like the amp was about twice as loud and then some), thus making the amp work harder and that might be enough to get you into some nice tube breakup where you say you want to be. It's not an expensive speaker so it's an experiment that won't leave you massively out of pocket and if it works to get you into the breakup zone of the tubes then it'll just come down to if you like the tones from the speaker.

Snowy


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Post subject: Re: DRRI Tube Options
Posted: Tue Jun 09, 2015 9:44 pm
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Retroverbial wrote:
I would regard such a measurement as highly unusual and start searching for the reason. The original design and all subsequent revisions are spec'd for 410 VDC.

Arjay



IME, DR and DRRI with strong GZ34s test closer to 450VDC, than 410VDC. One good reason to use tough 6V6GTs.


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Post subject: Re: DRRI Tube Options
Posted: Wed Jun 10, 2015 7:05 am
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You can simply remove one preamp tube which will increase the voltage to the remaining preamp tubes, giving you a bit more grit (earlier breakup). If using the "Vibrato" channel, remove V1 and this will give you a bit earlier breakup, albeit from the preamp. Likewise, when using the "Normal" channel, remove V2 for similar results. :idea:

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Post subject: Re: DRRI Tube Options
Posted: Wed Jun 10, 2015 4:17 pm
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Cmatmods Signa drive always does it for me and hardly any unwanted noise or color
Three clipping styles to suit your taste and built to last for ever !
Did I mention Quiet ?

Add some comp from my route 66 and ya got touch sensitive breakup that sounds SWEET !

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Post subject: Re: DRRI Tube Options
Posted: Thu Jun 11, 2015 2:16 am
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Thanks for all the suggestions. In regards to the speaker, I should perhaps have mentioned that my DRRI is a limited edition "Fudge Brownie" and it does not have the usual 100w rated Jensen Ceramic C-12K speaker. It has a Jensen Alnico P-12Q rated at 40w so it probably breaks up earlier than the regular DRRI. I don't know how it rates in terms of efficiency though.

I had heard about removing a pre-amp tube to boost the other channel but I regularly use both. I run inputs to both the Normal and the Vibrato channels via a Radial Twin City ABY switch. This has a setting to put the outputs 180 degrees out of phase and when selecting both gives a whole lot more tonal options including a significant volume boost.

Again, thanks for all the suggestions but I think for the time being I will leave it as it is because it really is a great amp.


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Post subject: Re: DRRI Tube Options
Posted: Thu Jun 11, 2015 2:29 am
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No probs, I looked up your current speaker and it appears to be quite inefficient already (95dB), so that rules out my suggestion.

http://www.jensentone.com/vintage_alnico/p12q

The standard C12K is quite more efficient at 99dB and would sound much louder.

http://www.jensentone.com/vintage_ceramic/c12k


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