Tube rolling, both fun and rewarding.

[Schu]

I am happy with the sound from this combination

 

MULLARD GZ32 CV593

KT 150's  Tong-Sol

CBS 7318

Tesla 12ax7

 

The Tesla 12AX7 is a awesome sounding tube and the CBS 7318's are worth every bit of the 89.00

 

 

[Rick J B]

I am happy with the sound from this combination

 

MULLARD GZ32 CV593

KT 150's  Tong-Sol

CBS 7318

Tesla 12ax7

 

The Tesla 12AX7 is a awesome sounding tube and the CBS 7318's are worth every bit of the 89.00

 

A1, which iteration or vintage are your Tesla's? 

 

I've read that some of the CBS tubes were awesome, were those produced by Amprex?

[Rick J B]

A1's run down, especially his choice of rectifier, jogged my memory and I remembered I had a used GZ34/5 tube stashed. It was made for EICO by Mullard I'm guessing early to mid 60's?

[Audible Nectar]

A1's run down, especially his choice of rectifier, jogged my memory and I remembered I had a used GZ34/5 tube stashed. It was made for EICO by Mullard I'm guessing early to mid 60's?

 

Sounds about right. Look at the code on the tube - it will read something like "f32 B2C4". Probably around '62-'66.

[Rick J B]

 

A1's run down, especially his choice of rectifier, jogged my memory and I remembered I had a used GZ34/5 tube stashed. It was made for EICO by Mullard I'm guessing early to mid 60's?

 

Sounds about right. Look at the code on the tube - it will read something like "f32 B2C4". Probably around '62-'66.

 

 

Sadly while much of the print on this tube is still in good shape, some of it has rubbed off. The only things that are clear are: GZ34/5 EICO by Mullard. Made in Great Britain. ......212.

[Audible Nectar]

 

 

A1's run down, especially his choice of rectifier, jogged my memory and I remembered I had a used GZ34/5 tube stashed. It was made for EICO by Mullard I'm guessing early to mid 60's?

 

Sounds about right. Look at the code on the tube - it will read something like "f32 B2C4". Probably around '62-'66.

 

 

Sadly while much of the print on this tube is still in good shape, some of it has rubbed off. The only things that are clear are: GZ34/5 EICO by Mullard. Made in Great Britain. ......212.

 

Look more closely where the glass meets the base - there is an acid-etched code on the glass. This doesn't rub off. Would be shocked if it isn't there.

[Rick J B]

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

[Rick J B]

 

 

 

A1's run down, especially his choice of rectifier, jogged my memory and I remembered I had a used GZ34/5 tube stashed. It was made for EICO by Mullard I'm guessing early to mid 60's?

 

Sounds about right. Look at the code on the tube - it will read something like "f32 B2C4". Probably around '62-'66.

 

 

Sadly while much of the print on this tube is still in good shape, some of it has rubbed off. The only things that are clear are: GZ34/5 EICO by Mullard. Made in Great Britain. ......212.

 

Look more closely where the glass meets the base - there is an acid-etched code on the glass. This doesn't rub off. Would be shocked if it isn't there.

 

 

Nah, nothing.

[Audible Nectar]

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

That's a 1983 Mullard made in the Mitchum factory. If it's anything like the CV4004 (12AX7) and CV4003 (12AU7) of the same era it's a nice tube. The CV4004 and 4003s are quite expensive these days - and BTW sound really good in the front end of VRDs.

[Rick J B]

 

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

That's a 1983 Mullard made in the Mitchum factory. If it's anything like the CV4004 (12AX7) and CV4003 (12AU7) of the same era it's a nice tube. The CV4004 and 4003s are quite expensive these days - and BTW sound really good in the front end of VRDs.

 

Thank you, sir.

 

I thought I remembered being told when I picked up the amp it was a NOS tube, but couldn't remember what it was.

[muel]

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

You know that is a 12at7 tube right?  

[Rick J B]

 

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

You know that is a 12at7 tube right?  

 

 

Say what?

 

Steve told me it was a 6922, which is what all the other tubes have been that I've tried in this spot.

 

Or at least the day I picked this amp up in 03 it had the tube in question in it and it also came with the JAN Phillips 6922. He said I could try either to see which I liked best.

 

Is it possible this amp could use both? I mean apparently it is because I've used both in that front end spot for long periods of time.

Edited September 26, 2014 by Rick J B

[Rick J B]

 

 

 

A1's run down, especially his choice of rectifier, jogged my memory and I remembered I had a used GZ34/5 tube stashed. It was made for EICO by Mullard I'm guessing early to mid 60's?

 

Sounds about right. Look at the code on the tube - it will read something like "f32 B2C4". Probably around '62-'66.

 

 

Sadly while much of the print on this tube is still in good shape, some of it has rubbed off. The only things that are clear are: GZ34/5 EICO by Mullard. Made in Great Britain. ......212.

 

Look more closely where the glass meets the base - there is an acid-etched code on the glass. This doesn't rub off. Would be shocked if it isn't there.

 

 

AN, here are some photos of the EICO tube.

 

 

 

 

Thats all the info visible on it I'm afraid.

 

Could it be that since it was produced specifically for EICO they left off the etching?

[Fjd]

 

 

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

You know that is a 12at7 tube right?  

 

 

Say what?

 

Steve told me it was a 6922, which is what all the other tubes have been that I've tried in this spot.

 

Or at least the day I picked this amp up in 03 it had the tube in question in it and it also came with the JAN Phillips 6922. He said I could try either to see which I liked best.

 

Is it possible this amp could use both? I mean apparently it is because I've used both in that front end spot for long periods of time.

 

 

 

There are many tube substitution books online.  However, several are typically needed as most do not cover all tubes.

 

http://frank.pocnet.net/other/Sylvania/SylTubSubstManual1953.pdf

http://www.worldtubecompany.com/mm5/merchant.mvc?Screen=TSL

 

I'm sure some that are more knowledgeable than I will come along and verify, or correct, the following.

 

In most instances the following tubes have similar parameters and it may be possible to substitute in a circuit; 6922, 6DJ8, 7308, ECC88, E88CC, E188CC, CV2492, CV2493, CV4108, CV4110, CV4109.

 

In most instances the following tubes have similar parameters and it may be possible to substitute in a circuit; 12AT7, ECC81, E81CC, ECC801S, 6201, 6060, CV455, CV4024, CV4033, 13D9.

 

From the pin-out diagrams that I’ve included, it looks like the 12AT7 should not necessarily work appropriately in a 6922 circuit without rewiring the socket.   From the diagrams below you will notice that the heater connections for the 12AT7 tube ties pins 4 and 5 together and feed the heater to 4/5 and 9, while the 6922 (6DJ8 below) has its heater connections of 4 and 5 (with pin 9 being a shield between the sections).  

 

 

 

 

 

 

 

 

 

If the circuit is wired for the heater in one tube, I don’t see how the heater would work for the other tube.  Maybe pin 9 is the key, I don't know for sure though.

 

I suppose you could apply the high voltage to the tube plates without the heaters; however, while it would survive for a while, it seems that prolonged use this way would ultimately damage the tube. 

 

While the "12" in the 12AT7 part number is for "12 Volts," one aspect of the 12A*7 series of tubes is that it provides a choice given that they are designed to run either two halves of the heater in parallel at 6.3V and 300mA or as a single 12.6V 150mA heater with a center tap.

Edited September 26, 2014 by Fjd

[Rick J B]

Thanks for the input Fjd.

 

I obviously need to email Steve, I'm confused on this.

[tube fanatic]

 

 

 

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

You know that is a 12at7 tube right?  

 

 

Say what?

 

Steve told me it was a 6922, which is what all the other tubes have been that I've tried in this spot.

 

Or at least the day I picked this amp up in 03 it had the tube in question in it and it also came with the JAN Phillips 6922. He said I could try either to see which I liked best.

 

Is it possible this amp could use both? I mean apparently it is because I've used both in that front end spot for long periods of time.

 

 

I suppose you could apply the high voltage to the tube plates without the heaters; however, while it would survive for a while, it seems that prolonged use this way would ultimately damage the tube. 

 

 

 

There is no concern about applying high voltage to the tubes with no heater voltage.  Why not give Deckert a call and find out what he is using pin 9 for in the amp?

 

Maynard

[Rick J B]

 

 

 

 

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

You know that is a 12at7 tube right?  

 

 

Say what?

 

Steve told me it was a 6922, which is what all the other tubes have been that I've tried in this spot.

 

Or at least the day I picked this amp up in 03 it had the tube in question in it and it also came with the JAN Phillips 6922. He said I could try either to see which I liked best.

 

Is it possible this amp could use both? I mean apparently it is because I've used both in that front end spot for long periods of time.

 

 

I suppose you could apply the high voltage to the tube plates without the heaters; however, while it would survive for a while, it seems that prolonged use this way would ultimately damage the tube. 

 

 

 

There is no concern about applying high voltage to the tubes with no heater voltage.  Why not give Deckert a call and find out what he is using pin 9 for in the amp?

 

Maynard

 

 

Yep, I need to touch base for sure.

 

Tho it must not be an issue because the last 4 tubes I've rolled through that location over the past 3 or so years have been 6922's and its sounded nice, especially with the older tubes.

[Fjd]

 

 

 

 

 

Another tube I have that I wonder about is the 6922 tube that came in my SE84C-S amp.

 

It bears no makers name, but has the following info printed on it:

 

000-4024

CV4024

KQDD/K

83-31

.

654

R3C4

 

Other than having short gray plates and a halo getter, thats all I can tell on it.

 

You know that is a 12at7 tube right?  

 

 

Say what?

 

Steve told me it was a 6922, which is what all the other tubes have been that I've tried in this spot.

 

Or at least the day I picked this amp up in 03 it had the tube in question in it and it also came with the JAN Phillips 6922. He said I could try either to see which I liked best.

 

Is it possible this amp could use both? I mean apparently it is because I've used both in that front end spot for long periods of time.

 

 

I suppose you could apply the high voltage to the tube plates without the heaters; however, while it would survive for a while, it seems that prolonged use this way would ultimately damage the tube. 

 

 

 

There is no concern about applying high voltage to the tubes with no heater voltage.  Why not give Deckert a call and find out what he is using pin 9 for in the amp?

 

Maynard

 

 

Yep, I need to touch base for sure.

 

Tho it must not be an issue because the last 4 tubes I've rolled through that location over the past 3 or so years have been 6922's and its sounded nice, especially with the older tubes.

 

 

@ Maynard, Thanks, I wasn't sure what the impact would be if there was no heater voltage or incorrect heater voltage.

 

@ Rick J B, The correct tube is the 6922.  The manual suggests 6N1P, 6DJ8 or 6922. 

 

What Muel was trying to point out is that the CV4024 is an equivalent to the 12AT7 tube and not an equivalent of the 6922.  I was trying to point out the difference in the pin-out with the heater to further the discussion and hopefully draw out more knowledge (i.e. Maynard).

 

I did find this copy of the ower's manual for the SE84C-S amp and in looking at the last page, it appears that pin 9 may not be used. 

 

http://www.decware.com/zsowner.pdf

 

 

 

 

Edited September 26, 2014 by Fjd

[Rick J B]

Very cool, thanks Fjd. 6922 or equivalent it is.   

[beeker]

I have to include in a tube rolling thread to keep an eye on bias.

 

If new tubes have the same number and burn in easily then biasing should not be much of an issue. But with a switch even with automatic biasing it is smart to keep an eye on bias to keep the amp safe. ]

 

I have 2 friends that help me keep an eye on the bias on older tube gear as well as new tube gear I have or have had.

 

When switching actual label numbers on a tube re biasing is usually a must. Even if new tubes burn in or the tube swap goes well.