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Post subject: Re: 1966 DeLuxe Reverb
Posted: Sun Apr 13, 2014 3:33 pm
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cedarblues wrote:
Nikola Tesla wrote:
Each to their own, bit I prefer more ballsy sounding JJ6V6 to TAD 6V6 :lol:


My experience was the exact opposite... The JJs were very clean and had no character, the TADs were the closest to the RCAs. Which TAD 6V6 did you try?



Very interesting, although I have the original RCA's and will test them as well (if they re still good).

Herewith the two side by side

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Post subject: Re: 1966 DeLuxe Reverb
Posted: Sun Apr 13, 2014 6:24 pm
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cedarblues wrote:
How would you compare the GTY to the RCA 6V6GTA? I'm always interested in trying new tubes, so I'll be keeping an eye on some Raytheons...


If both GTY and GTA are strong testing... the GTY has better bass-to-midrange than the usual GTA. BTW... the best GTA IMHO, is the black plate made in USA Tungsol. Very potent tube. Clean highs, but not the warm, nice midrange of a good Raytheon 6V6GTY.


http://i.ebayimg.com/00/s/MTAwMFg3NTA=/ ... y/$_57.JPG


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Wed Apr 16, 2014 4:38 pm
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BMW2002Ti wrote:
Nikola Tesla wrote:
.


The experiment with the new tubes on the horizon too .. :mrgreen:

BTW, do I bias these as a 12W tubes .... .. .or higher?!? :?: :?:


I do this trick with JJ's output tubes. Start at low idle dissipation (like 8 watts per tube). Check to see if the tubes are gassy or have contaminates. The bottle will have a lazy blue-purple glow. Sometimes, this glow will flicker. Let the amp idle for 30 minutes to 1 hour, if you see this. Check to see if the purple glow has gone done. Or decreased a bit.

Now, rebias the amp to around 10 watts per tube. Sound ok? No red plating? You can go to 11-12 watts per tube. Recheck the bias after first use. Then, again, after a few sessions. Should stabilize by one or two readjustments.


BMW2002Ti,

As for biasing ... 70% dissipation at 12W is 18.4mA.

My tech says he would bias at 25-30mA. :twisted:

I have tried 27mA at 455VDC, no red-plating, nice sound.

I'm bit confused now?? :?: :?:


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Thu Apr 17, 2014 1:43 am
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Nikola Tesla wrote:

BMW2002Ti,

As for biasing ... 70% dissipation at 12W is 18.4mA.

My tech says he would bias at 25-30mA. :twisted:

I have tried 27mA at 455VDC, no red-plating, nice sound.

I'm bit confused now?? :?: :?:


There is NO ONE rule to bias , most of the time 70% for AB Class amps work fine , nice tone good tube life . But it is a average for ALL amp .

It is also a matter of taste too AND the tube brand .

My experience show me most of Fender amps did not sound better at more than 50% average.

27 ma at 455 volts is 12.285 watts ,( 100% ) no reason for red plating .

Vox AC30 amp's tubes work best at more than 125% if not at 150% and no red plating.

You probably need more than 200 % to red plate tube, I don't not make serious test to check.
This make me laugh when I read on many forums , people saying they bias their amp with their ears and no red plating meaning bias must be right. :lol:


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Fri Apr 18, 2014 12:32 am
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stratele52 wrote:
Nikola Tesla wrote:

BMW2002Ti,

As for biasing ... 70% dissipation at 12W is 18.4mA.

My tech says he would bias at 25-30mA. :twisted:

I have tried 27mA at 455VDC, no red-plating, nice sound.

I'm bit confused now?? :?: :?:


There is NO ONE rule to bias , most of the time 70% for AB Class amps work fine , nice tone good tube life . But it is a average for ALL amp .

It is also a matter of taste too AND the tube brand .

My experience show me most of Fender amps did not sound better at more than 50% average.

27 ma at 455 volts is 12.285 watts ,( 100% ) no reason for red plating .

Vox AC30 amp's tubes work best at more than 125% if not at 150% and no red plating.

You probably need more than 200 % to red plate tube, I don't not make serious test to check.
This make me laugh when I read on many forums , people saying they bias their amp with their ears and no red plating meaning bias must be right. :lol:



stratele52,

27mA at 455 is 105%.

I didn't know its safe to bias that high .. or is it really safe?!

:?:


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Fri Apr 18, 2014 2:21 am
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Nikola Tesla wrote:

stratele52,

27mA at 455 is 105%. 100% is Just a short cut :lol:

I didn't know its safe to bias that high .. or is it really safe?!
Not safe for Class AB amp like Fender DR , but for Class A amp like Vox you need very very hot bias to have the good Vox tone, 150 % or close. Yes tube's life is not long as on Fender .
Class AB did not work like Class A .That is why bias are not the same and must not me same too


:?:


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Tue Apr 22, 2014 7:54 pm
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Just re-biased the amp with the set of fresh JJ 6V6S's.

The bias value drifted today compared to yesterday. :roll: :!:

Yesterday reading:
V7 - 17.9mA/463VDC
V8 - 19.9mA/463VDC

Today reading:
V7 - 19.1mA/460VDC
V8 - 19.5mA/460VDC

The most confusing part is the difference in 2mA between V7 & V8 (yesterday) and only .4mA today.

Why is the value drifting?

Any idea please :?:


Last edited by Nikola Tesla on Tue Apr 22, 2014 8:16 pm, edited 1 time in total.

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Post subject: Re: 1966 DeLuxe Reverb
Posted: Tue Apr 22, 2014 8:08 pm
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Maybe two problems. 1.) The tubes are still burning-in. The bias may settle to a fix point after a few more hours of use. 2.) Your house voltage is fluctuating.

Try warming the amp up, for a good 30 minutes. Then, read the bias. If the numbers are still moving around, turn the amp off. Pull the phase inverter. Now try reading the bias. If it is now rock steady, you may have some random noise coming through the gain stages or a tad of instability in those stages.

Nothing to really worry about, as long as the output tubes don't wander more than 3-4mA per tube, while amp is at idle. No input, zero volume, speakers connected.


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Sat Apr 26, 2014 6:49 pm
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BMW2002Ti wrote:
Maybe two problems. 1.) The tubes are still burning-in. The bias may settle to a fix point after a few more hours of use. 2.) Your house voltage is fluctuating.

Try warming the amp up, for a good 30 minutes. Then, read the bias. If the numbers are still moving around, turn the amp off. Pull the phase inverter. Now try reading the bias. If it is now rock steady, you may have some random noise coming through the gain stages or a tad of instability in those stages.

Nothing to really worry about, as long as the output tubes don't wander more than 3-4mA per tube, while amp is at idle. No input, zero volume, speakers connected.



Looks like JJ 6V6S's (or maybe other brands as well) need some time to burn-in. After some 20 hours of playing both tubes displayed a very close reading: V7-19.5mA and V8-19.1mA (at 460VDC).
Will keep an eye on the bias value ... hopefully the drifting is over :lol:


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Sat May 24, 2014 4:03 pm
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cedarblues wrote:
Nikola Tesla wrote:
Each to their own, bit I prefer more ballsy sounding JJ6V6 to TAD 6V6 :lol:


My experience was the exact opposite... The JJs were very clean and had no character, the TADs were the closest to the RCAs. Which TAD 6V6 did you try?



I went with TAD 6V6 - STR .. these sounded a bit anemic to me, the JJ's are something different. :mrgreen:


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Sat May 24, 2014 4:10 pm
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There are a few ink stamps; even on the cabinet

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.. and on the chassis

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Post subject: Re: 1966 DeLuxe Reverb
Posted: Sat May 24, 2014 9:54 pm
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My experience show me most of Fender amps did not sound better at more than 50% average.

I agree. When I go over 56% idle with JJ's, my volume and tone go southward. Perfect for me is around 53% idle.


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Sun May 25, 2014 5:03 pm
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yomammaaho wrote:
My experience show me most of Fender amps did not sound better at more than 50% average.

I agree. When I go over 56% idle with JJ's, my volume and tone go southward. Perfect for me is around 53% idle.


Are you referring to a Black Face DeLuxe Amp?

56% at 460VDC is 14.6mA

53% at 460VDC is 13.8mA

I find that variation in bias from 50-70% makes little difference in the overall performance of the amp .. but that's maybe only me. :D

With JJ's I have settled at 19.2mA & 19.5mA.

It is also interesting (mentioned previously in this tread) how burning in tubes made them closer in mA value ... and nearly perfectly matched. :wink:


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Tue May 27, 2014 1:52 pm
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It's with a drri with a plate voltage of about 415 vdc.
Maybe its the lower plate voltage, but when I get anywhere near 60% idle on my JJ's, my sound gets too brown.
53% is perfect offering good clarity AND break up at higher volumes.


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Post subject: Re: 1966 DeLuxe Reverb
Posted: Thu Jun 05, 2014 3:31 am
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:shock:

The old Oxford is probably a bit tired by now, although it was re-coned at some stage.

A bit of a speaker shopping to do now .. :mrgreen:

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