It is currently Mon Mar 16, 2020 4:51 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 32 posts ]  Go to page 1, 2, 3  Next
Go to page 1, 2, 3  Next
Author Message
Post subject: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 7:02 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Remember when you change rectifiers, you change not only the B+ to the output tubes --- but, also the anode voltages to the gain, EFX, and PI stages. And this change in signal tube voltages can cause more tonal changes, than the output tubes.

Just in case, you were wondering why 5AR4/GZ34 sound so much different than 5U4GB in certain amps. Or a high testing new rectifier can cause such a global change.


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 9:15 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
BMW2002Ti wrote:
Remember when you change rectifiers, you change not only the B+ to the output tubes --- but, also the anode voltages to the gain, EFX, and PI stages. And this change in signal tube voltages can cause more tonal changes, than the output tubes.

Just in case, you were wondering why 5AR4/GZ34 sound so much different than 5U4GB in certain amps. Or a high testing new rectifier can cause such a global change.


+1

And higher anode voltages generally equate to a cleaner tone. Which is one reason why FMI switched from the tried-and-true GZ34 to the higher-voltage 5U4GB in the larger tube-rectified models.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 12:15 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Sat May 22, 2010 10:53 pm
Posts: 1467
Location: deep down in Florida...
My BF amps have 5AR4 rectifiers while my SF amps have 5U4GB. I have a spare Mullard 5AR4 I'd like to try in either the Super Reverb or Deluxe Reverb, both SF. Recommended? Do I just need to check and adjust the bias after swapping tubes?


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 12:23 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
The bias should be checked after swapping rectifiers and -- if necessary -- adjusted to whatever specs you're comfortable with.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 1:14 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Sat May 22, 2010 10:53 pm
Posts: 1467
Location: deep down in Florida...
So no issues running a 5AR4 rectifier in an amp designed for 5U4GB? How would it affect the tone?


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 1:19 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
Theoretically it would deliver more PS sag, and sooner, which are vital components to compression and enhanced harmonics under overdriven conditions. However, amps designed for the 5U4GB are delivering some 30% more heater current to the rectifier -- this might shorten a 5AR4's service life.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 1:27 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Sat May 22, 2010 10:53 pm
Posts: 1467
Location: deep down in Florida...
So not really recommended? I'll give it a try this weekend and see if it's worth it...


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Fri Jun 06, 2014 1:45 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Retroverbial wrote:
...However, amps designed for the 5U4GB are delivering some 30% more heater current to the rectifier -- this might shorten a 5AR4's service life.

Arjay


No worries. The 5AR4 will only draw its rated heater current, and no more. While the circuit designed for the 5U4GB heater can deliver enough current for the 5U4GB (about 3 amps), it will only deliver what is drawn by the rectifier tube, and in the case of the 5AR4, the circuit will only draw about 1.9 amps. The maximum capability of any electrical circuit is different than what it actually delivers, as the delivered current is determined by the load on the circuit, not its capability.

I hope that I explained that clearly. :?:

I should add that trying the inverse is when you should worry. Do not put a 5U4GB in a circuit designed for a 5AR4. The 5U4GB will pull 3 amps of heater current, and could overload a circuit designed for 1.9 amps of current (5AR4).

_________________
---> "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.


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Sun Jun 08, 2014 8:55 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Sat May 22, 2010 10:53 pm
Posts: 1467
Location: deep down in Florida...
So I decided to try a 5AR4 in my '75 Deluxe Reverb. I use a Bias Rite to measure the bias and plate voltage.

The amp has a pair of RCA 6V6GTA and a GE 5U4GB rectifier. Plate voltage was at 442 on the Bias Rite. I dropped the bias from around 21 to maybe 16, I then installed a Mullard 5AR4 and now the plate voltage is at 465. Isn't that kinda high for a SFDR???


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Sun Jun 08, 2014 9:24 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
No, it just means that you have a healthy PT and PSU caps. Mullard GZ34 are noted for strong B+'s.


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Sun Jun 08, 2014 9:34 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Sat May 22, 2010 10:53 pm
Posts: 1467
Location: deep down in Florida...
Thanks Bimmer, that's good to know :)

I had the filter caps replaced when I bought the amp 2-3 years ago... so no issues playing the amp with the plate voltage being that high? I tested the amp for a few mins just to see what it sounds like, I'm not sure if it's just my imagination but it sounds like the amp got a little brighter, something I want to accomplish in this amp.


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Sun Jun 08, 2014 9:50 am
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Fri Aug 21, 2009 1:45 pm
Posts: 852
Location: SoCal323
cedarblues wrote:
Thanks Bimmer, that's good to know :)

I had the filter caps replaced when I bought the amp 2-3 years ago... so no issues playing the amp with the plate voltage being that high? I tested the amp for a few mins just to see what it sounds like, I'm not sure if it's just my imagination but it sounds like the amp got a little brighter, something I want to accomplish in this amp.



Good info, please keep us updated on its longevity. I tried two different types of 5ar4's on my bandmaster reverb, one a JJ and the second a Sovtek. The JJ lasted less than a two weeks while the Sovtek faired a bit longer, about a month. Don't know if it was just bad tubes or if my BMR just doesn't take kindly to 5AR4's. Either way, I reinstalled the original 5U4GB which is of vintage variety and here I am a year and a half later it's still kicking. Maybe they just don't make those kinds of tubes like they used to anymore. :wink:

_________________
Its a lifestyle.....

Image


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Sun Jun 08, 2014 9:56 am
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
cedarblues wrote:
Thanks Bimmer, that's good to know :)

I had the filter caps replaced when I bought the amp 2-3 years ago... so no issues playing the amp with the plate voltage being that high? I tested the amp for a few mins just to see what it sounds like, I'm not sure if it's just my imagination but it sounds like the amp got a little brighter, something I want to accomplish in this amp.


No problem, as long as the idle bias current is readjusted for the higher plate voltages. When it comes to 5Y3GT, 5AR4/GZ34, & 5U4GB rectifiers, hard to beat US or British made ones. BTW... the finest GZ34 I ever used was a Dutch made, metal based one. Late 1950's manufacturing dates. These Dutch tubes often ran 15-20VDC above strong testing Blackburn, UK ones.


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Sun Jun 08, 2014 10:24 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Sat May 22, 2010 10:53 pm
Posts: 1467
Location: deep down in Florida...
Great! I didn't want to risk damaging that Mullard tube...

I dropped the bias before swapping tubes, the 5AR4 brought it back up to around 21, so it's a safe number.


Top
Profile
Post subject: Re: Rolling tube rectifiers
Posted: Sun Jun 08, 2014 10:26 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Sat May 22, 2010 10:53 pm
Posts: 1467
Location: deep down in Florida...
socal323 wrote:
Good info, please keep us updated on its longevity. I tried two different types of 5ar4's on my bandmaster reverb, one a JJ and the second a Sovtek. The JJ lasted less than a two weeks while the Sovtek faired a bit longer, about a month. Don't know if it was just bad tubes or if my BMR just doesn't take kindly to 5AR4's. Either way, I reinstalled the original 5U4GB which is of vintage variety and here I am a year and a half later it's still kicking. Maybe they just don't make those kinds of tubes like they used to anymore. :wink:


That was my concern, those Mullard rectifiers ain't cheap! But if Bimmer said it's fine then I'll give it a try :D


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 32 posts ]  Go to page 1, 2, 3  Next
Go to page 1, 2, 3  Next

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: