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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Jul 18, 2015 11:33 am
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When I bought my DRRI earlier this year I had no intention of replacing any of the tubes but unfortunately some of the factory fitted Groove Tubes were noisy and/or microphonic so I set about replacing them.

I have previously gone on record as saying that modern tubes are basically all the same and the difference is nothing that cannot be fixed by adjusting the EQ. I am now happy to admit that I was wrong. I still think that replacing just one tube in an amp has only minor impact on tone but I feel strongly that different tubes work better or worse with certain other tubes.

By way of example, when I put a Tung-Sol in V2 and kept the factory tubes in all other positions I could not hear any difference. But if I also replaced V6 with a Mullard CV4024 the change was more noticeable. If I kept the Mullard in the PI but put the Groove Tube back in V2 then the tone was more or less back to where it was. Putting the TAD in V4 was the final change that perfected the pre-amp tone for my taste. Having done that, the icing on the cake was the Tung-Sols in the power section!


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Wed Aug 12, 2015 12:13 am
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shimmilou wrote:
Sounds like a great lineup of tubes. Tung Sol are among my favorites too, and come from the same factory as EH. 8)


I have the Tungs in my 68 CDR and I like them more than the OEM GT's.

I'm thinking of putting in an SS rectifier in my CDR.
Have you played a DRRI or CDR with an SS rectifier?


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Wed Aug 12, 2015 1:44 am
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I've been so pleased with the tone of my DRRI that I emailed the techie that biased my power tubes and asked what he set them to. Largely based on what I had read about tube bias I was expecting him to reply with a number in the low 20s but this is what he said

"I normally set the bias to give 60% of maximum valve power dissipation for any particular valve type (ie mid range 50% to 70%) for Class AB amps. Obviously absolute bias voltage and bias current changes from amp to amp depending on individual transformer voltages. Hence the need to measure everything as its adjusted."

I'm so glad I didn't try to do it myself with a bias probe and multimeter.


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Aug 15, 2015 2:18 am
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Rverb wrote:
shimmilou wrote:
Sounds like a great lineup of tubes. Tung Sol are among my favorites too, and come from the same factory as EH. 8)


I have the Tungs in my 68 CDR and I like them more than the OEM GT's.

I'm thinking of putting in an SS rectifier in my CDR.
Have you played a DRRI or CDR with an SS rectifier?


Changing from tube to SS rectification will alter the dynamics of the amp, loosing the "sag" of the tube rectifier, which will give you a tighter sound, losing some of the touch sensitivity and bloom. Personally, I would not change an amp from tube to SS rectification unless I really didn't like the sound, which has never been the case for me with any DR or DRRI. :wink:

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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Dec 19, 2015 7:12 am
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Thought I'd give an update on the tubes in my DRRI.

When I was testing various tubes I was unable to get any reissue Mullards as they are not generally available in the UK. However, recently I was able to purchase a new Mullard ECC83/12AX7. I really like the Tung-Sols in V1 and V2 so thought I'd try the Mullard in V4 in place of the TAD 7025 WA (RT080). I love it!

It seems fatter, warmer and more drive than the TAD but the amp has lost none of it's sparkle. So my current tube line-up is:

V1 & V2 - Tung-Sol 12AX7
V3 - NOS JAN Philips 12AT7WC
V4 - Mullard ECC83/12AX7
V5 - JJ ECC83S
V6 - NOS Mullard ECC81/CV4024
V7 - JJ GZ34
V8 & V9 - Tung-Sol 6V6GT

When I bought the amp I had difficulty in finding an overdrive I liked with the stock tubes but with the current tubes I can get beautiful extra dirt with stacked Free The Tone MS-SOV and Okko Diablo Gain+. The SOV is first in the signal chain and the Okko next. The tone is still primarily coming from the amp but the overdrives give it extra grunt!


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Post subject: Re: Help! What is that noise in my DRRI?
Posted: Sat Dec 19, 2015 9:29 am
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shimmilou wrote:
Changing from tube to SS rectification will alter the dynamics of the amp, loosing the "sag" of the tube rectifier, which will give you a tighter sound, losing some of the touch sensitivity and bloom. Personally, I would not change an amp from tube to SS rectification unless I really didn't like the sound, which has never been the case for me with any DR or DRRI.


+1

If a "cleaner" sound is desired, look to the Twin Reverb.

Arjay

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