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Post subject: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 4:07 am
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Hi all. I ve had to change my plan to invest in a head a cab after a change in finances.
So I ve decided to lightly mod my BDRI. I like the amp generally but would like to tame the flabby bottom end and maybe just tame the sometimes brittle highs. I got the amp 2nd hand and its stock. Looking to replace the speaker and change tubes. I don't need more headroom, and im not attempting to turn the amp into something it's not. Just want the bottom end tighter and not as boomy, and the highs a touch smoother.
Speaker wise I ve sort of narrowed it down to
Weber 12f150
Weber Blue dog
Eminence Texas heat
Eminence Cannabis Rex.

Tube wise
V1,2 and 3. Tungsol re issue 12AX7 s
V4 and 5. JJ 6L6GCs or Svetlana winged C 6L6s.

I'm new to the modding bit, so am I in the right ball park with any of the above in all you experience fellow forumites. Or and further suggestions.
I know this has been asked many times before. But as I've said, I'm not trying to totally alter the sound of the amp, just tweak. Want to keep the mods to just speaker and tubes. If I can't achieve want I'm after with that, there's no point polishing a turd so to speak.
Just some more info for you to go on. Play mainly blues. Guitar is a 62 hot rod strat.

Thanks all in advance for you valuable input.


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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 9:40 am
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I like Bluesier tone of the 12A125 or -150 Weber Vintage in these RI Fender amps. Light or no doping. I put a 12A125A (30 watt) into a DRRI. That single change transformed the amp from just loud, to a much wider range of tone, volume, and sweet harmonics. Better controlled by guitarist input.

You can run Sylvania 5751 or some good GE 12AY7 (6072) in the input stage (V1). This will tame the "in-your-face" tone had lower volumes. Give you later onset of OD. Now, Raytheon 5751 or RCA 12AY7/6072 might be primo, but they are just too $$ these days. You can get some pretty good used, well-testing, & QUIET older tubes. For a good price. Tone of these high testing older tube is usually better than new production. And they last pretty long time.

http://www.ebay.com/itm/2-General-Elect ... 256d6fbc03

http://www.ebay.com/itm/A-Pair-of-Short ... 5648ce2109


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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 10:33 am
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Not sure about alnico tbh, always sounded a tad harsh to me. But will look into it.
The Jensen P12n was suggested to me by a highly respected tube/speaker outlet here in the UK. Listened to loads of clip and I thought is was awful. Way brittle and spikey.


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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 11:07 am
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I have the Cannibis Rex in my BDRI along with a NOS JAN GE 12AY7 in V1 and JJ tubes in the other positions. Proper biasing is a must for good sound out of this amp as the factory bias is way too cold.

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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 11:29 am
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How do you find the Cannibis Rex. Does the 12AY7 give a lower gain/more headroom etc. Only ask because i dont use a crlstal clean sound. Even my clean sound i like with a touch of gtir on single string notes and a slight fraction of break up when a chord is played. So more clean headroom is not something im after. And just to add. My driven sound is courtesy a fulltone fulldrive into the clean channel.


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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 12:21 pm
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BMW2002Ti wrote:
I like Bluesier tone of the 12A125 or -150 Weber Vintage in these RI Fender amps. Light or no doping. I put a 12A125A (30 watt) into a DRRI. That single change transformed the amp from just loud, to a much wider range of tone, volume, and sweet harmonics. Better controlled by guitarist input.

You can run Sylvania 5751 or some good GE 12AY7 (6072) in the input stage (V1). This will tame the "in-your-face" tone had lower volumes. Give you later onset of OD. Now, Raytheon 5751 or RCA 12AY7/6072 might be primo, but they are just too $$ these days. You can get some pretty good used, well-testing, & QUIET older tubes. For a good price. Tone of these high testing older tube is usually better than new production. And they last pretty long time.

http://www.ebay.com/itm/2-General-Elect ... 256d6fbc03

http://www.ebay.com/itm/A-Pair-of-Short ... 5648ce2109


That Weber 12A150 does sound pretty good. No where near as bright and ice pickey as the eqivallent Jensen clips ive heard.
Would you say the Alnico has a smoother tone to the 12F150?


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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 2:07 pm
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dc01 wrote:
How do you find the Cannibis Rex. Does the 12AY7 give a lower gain/more headroom etc. Only ask because i dont use a crlstal clean sound. Even my clean sound i like with a touch of gtir on single string notes and a slight fraction of break up when a chord is played. So more clean headroom is not something im after. And just to add. My driven sound is courtesy a fulltone fulldrive into the clean channel.


The CR is a warm speaker with solid lows and smooth highs.

12AY7 is lower gain than a 12AX7 or 5751 but gives a nice bluesy tone. Also helps to tame the overactive volume control by allowing you to turn the volume up into a smoother range of its sweep. I also use a Fulltone FD-2M into the clean channel. Great combination with that speaker and tube. And let me repeat, the BDRI needs to be biased hotter than stock for best tone.

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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 2:26 pm
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What would you recommend as a bias reading at the test point. I was going to start a 70mv, which i believe is the top end of the recommened voltage.

Any recommendations for a good 12AY7 that readily available in the UK.
i ve seen these,
http://www.karltone.co.uk/electro-harmo ... -100-p.asp

or these

http://www.hotroxuk.com/jan-12ay7-6072a.html


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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 2:59 pm
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Location: Natural Bridge, Virginia
dc01 wrote:
What would you recommend as a bias reading at the test point. I was going to start a 70mv, which i believe is the top end of the recommened voltage.

Any recommendations for a good 12AY7 that readily available in the UK.
i ve seen these,
http://www.karltone.co.uk/electro-harmo ... -100-p.asp

or these

http://www.hotroxuk.com/jan-12ay7-6072a.html


Easy question first: Go with a JAN NOS GE or Phillips 12AY7. I tried a E-H 12AY7 in my BDRI and there was no comparison.

As far as bias setting, keep in mind that to bias properly you have to measure both cathode current and plate voltage. You can measure both with just a DVM at the Fender test points. However, I and others prefer to use a bias probe that in conjunction with a DVM will measure both cathode current and plate voltage more accurately and more importantly, safely. The probe I use is this one:

http://www.amp-head.com/product_info.ph ... ucts_id=70

With both the Fender test point and a good bias probe, you are measureing voltage across a one ohm resistor so that 1 mV = 1 mA. The big difference is that the Fender resistor has a 5% tolerance and a good bias probe one ohm resistor has a 1% tolerance. Makes a difference. Using JJ 6L6GCs in my BDRI, my current bias setting is 40 mA cathode current (approximately 38 mA plate current) at 410 VDC plate voltage. This gives about 53% max plate dissipation. Measure using the Fender test point gives 88 mV which works out to be 44 mA cathode current per tube.

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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 3:16 pm
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Cheers bluesky. Great info.
My first time setting/biasing an amp up so any info like that handy.

Just got to make my mind up on a speaker now. :D


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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 4:05 pm
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dc01 wrote:
Cheers bluesky. Great info.
My first time setting/biasing an amp up so any info like that handy.

Just got to make my mind up on a speaker now. :D


Do as search on me in this forum. I have posted a lot about the BDRI.

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Post subject: Re: Light mod work to my BDRI.
Posted: Sat Mar 03, 2012 7:25 pm
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I had used 5751 in v1 & JJ's for power and the Cannabis Rex was the speaker I had swapped it too.
It was a good combination, back when I had the amp.
Big difference from the original stock speaker & tubes.

Yes warming up the bias from factory settings did make a big difference.

I had also tried the Swamp Thang, that is also a nice clean speaker with a heavy bottom end.
Also tried a v30, nice speaker but did not like it in the bdri cabinet.

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Post subject: Re: Light mod work to my BDRI.
Posted: Sun Mar 04, 2012 12:35 am
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Im not a fan of the V30 tbh. When i was looking at heads and cabs not long ago i thought it was way to go, but the more i tried a range of cabs with them the more i disliked it. Way to harsh and brittle upper mids for me.

From the demos i ve heard the Texas Heat sounds similar to the Swamp Thang, but possibley to heavy in the bottom end.

How does the Weber 12F150,12A150 and C Rex compare in real world in your opinions. On so much you tube can give you. I know its very subjective, but any input is appreciated.

And also, any preferences for tubes in V2 and V3. Or shall i just stick with the Tungsols or JJs previously recommened to me?


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Post subject: Re: Light mod work to my BDRI.
Posted: Thu Mar 22, 2012 8:44 am
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My mods have been done and all I can say is that it sounds fantastic. The change has blown me away. Still got the Fender sound but Fender with bollocks. The amp has really come to life. I ended up doing the following.
Speaker swap for a Weber 12F150
V1 Phillips 5751
V2 Tungsol RI 12AX7
V3 Tungsol RI 12AX7 balanced
V4+V5 JJ 6L6GCs with the bias at 88mv at test point.

I can take or leave the drive channel as its still a tad feeble. But the clean channel us something else!
Big thanks to those who had any input on this thread.
Just one last thing.
The bias pot seemed to have very little resistance when turned. Am a bit concerned that any amp vibration could cause it to move. Is this normal? If so, any suggestions for something to hold it in place. As in something similar to the original blob of red paint.
Cheers all.


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Post subject: Re: Light mod work to my BDRI.
Posted: Thu Mar 22, 2012 10:18 am
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I wouldn't worry about the bias pot moving, it won't. The stuff used by the factory isn't to hold the pot in place, it is typically used to indicate if the pot was adjusted by someone after it was set at the factory, a kind of factory seal. If you feel the need to "hold it in place", use a very small dab of fingernail polish on the lower edge of the pot, lightly connecting the blue part to the base, similar to the factory stuff. Use the lower edge of the pot, so the polish doesn't run down into the pot. If you use too much, it can be very difficult to turn the pot later, and could even ruin the pot. I always kept a bottle of red fingernail polish in my toolbox when I did service, very useful to know if a customer made his own adjustments on the machinery after I left, and then wanted a warranty call at 2 AM. :wink:

For some reason, red seemed to work better than other colors. :? :lol:

Oh, recheck your bias after playing for awhile, some drift may occur and you might need to readjust. The drift is normal for most new tubes, and is not from the bias pot moving, just components/tubes "settling".

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