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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Wed Dec 24, 2014 11:52 pm
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shimmilou wrote:
Great description t-luxe.

The JJ made GTs in my DRRI made it sound like a HRDlx, without the low end and volume of the HRDlx. Since I already have a HRDlx, I wanted the more traditional sound of 6V6, so went with the EH GTs. I am sure that the Tung Sol will also sound more like traditional 6V6.

I can understand maybe wanting the clean sound of the JJ, but the killer harmonics, chimey high-end and articulate touch sensitivity of the EH or Tung Sol is pretty sweet!


Great.
Sounds like I will like the Tungs.
The bias probe should be here soon and I can try them out.

I also have a couple of NOS Jan Phillips Sylvania 5751s coming.
Also looking for some NOS 12ax7's.
I'd really like to try an Ei 12ax7, Yugoslavian made. But from what I read getting a good one is hit and miss.
When you get a good one they are said to be fantastic, but you pays your money and you takes your chances with Ei it seems.


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Thu Dec 25, 2014 11:39 pm
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Just a little warning. I've had thermal runaway issues with the TSRI 6V6GT ( Russian). Bias them to 8-9 watts per tube. Not over 20 watts, if possible.

There are a lot of good NOS or near NOS good US made 6V6GT, -GTA, and -GTY available. FWIW...

http://www.ebay.com/sch/i.html?_from=R4 ... A&_sacat=0


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Fri Dec 26, 2014 3:12 pm
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BMW2002Tii wrote:
Just a little warning. I've had thermal runaway issues with the TSRI 6V6GT ( Russian). Bias them to 8-9 watts per tube. Not over 20 watts, if possible.

There are a lot of good NOS or near NOS good US made 6V6GT, -GTA, and -GTY available. FWIW...

http://www.ebay.com/sch/i.html?_from=R4 ... A&_sacat=0


Thanks for the heads up.

Man there are so many varying experiences with same amps and tubes. Some post how great the Tung 6V6's are and others have issues.
The only way to know for any particular amp is to simply try it while keeping in mind what others have experienced.

I was going to do the simple bias route, meaning, use the listed basic average plate voltage and adjust bias according to the recommended settings without actually measuring the real plate voltage.
I know this sacrilege for those of you who do it the correct and proper way but I didn't get a probe that lets me easily check plate voltage.

I'll have to relook at how to check the voltage the manual way.
Suggestions on that are greatly appreciated. :)


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Fri Dec 26, 2014 3:47 pm
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Probably the best/safest way to check the Plate voltage without having it built in to your bias probe, is to attach the negative meter lead to the chassis, and then using only one hand (keep the other hand behind you or in your pocket), touch the positive meter lead to the connection point where the brown or blue wires from the OT primary connect near the output tubes, being careful not to touch the meter lead to anything but the one connection. Note that the blue wire is for one output tube Plate, and the brown wire is for the other. They will be about the same voltage. The OT primary has three wires, blue, brown and red, and the red wire connects to the B+.

Otherwise, it's not entirely out of the question to simply use the voltage listed on the schematic. Unless something is wrong with your amp, the schematic listed voltage is typically close to actuality.

Using safety glasses is such a habit for me that I forget to mention them. Use them! :idea:

Oh, and be prepared, you might hear a pop when connecting the meter, that's normal.

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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Fri Dec 26, 2014 4:42 pm
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Rverb wrote:
BMW2002Tii wrote:
Just a little warning. I've had thermal runaway issues with the TSRI 6V6GT ( Russian). Bias them to 8-9 watts per tube. Not over 20 watts, if possible.

There are a lot of good NOS or near NOS good US made 6V6GT, -GTA, and -GTY available. FWIW...

http://www.ebay.com/sch/i.html?_from=R4 ... A&_sacat=0


Thanks for the heads up.

Man there are so many varying experiences with same amps and tubes. Some post how great the Tung 6V6's are and others have issues.
The only way to know for any particular amp is to simply try it while keeping in mind what others have experienced.

I was going to do the simple bias route, meaning, use the listed basic average plate voltage and adjust bias according to the recommended settings without actually measuring the real plate voltage.
I know this sacrilege for those of you who do it the correct and proper way but I didn't get a probe that lets me easily check plate voltage.

I'll have to relook at how to check the voltage the manual way.
Suggestions on that are greatly appreciated. :)


The CDR schem. shows 407Vdc at the plates. If you're going to use that figure, (and assuming a 6V6 to be a 14 watt tube), then 10 watts/tube would be about the recommended maximum of 70% dissipation(10w / 14w =.714), which would work out to 24.5mA/tube(10w / 407v=.0245 amps).
9 watts/tube would equal 22mA, or about 65% dissipation; and 8 watts/tube would be 19.5mA and 57% dissipation.

So you see you have quite a range to play with.
Listen and set it where you like it somewhere between 50%-70%.-doesn't have to be right at 70% or some other figure recommended on the inter-webs.
I've got my '75 SFDR set at 10watts, but my CDR set at just over 9 watts because that's where they sound best to me.


In practice, my actual pV with the stock GT/JJs was 405v, and 395v with a set of Tung Sols. This will vary somewhat by tube(and also by bias setting) so is not to be taken as Gospel. It's usually best to measure your actual plate voltage and figure out your settings from there; though I suppose you won't be too far off by using the schematic values...just don't push the upper limits of the range and be sure to check for red-plating.


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Sun Dec 28, 2014 6:02 pm
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Got the Eurotubes bias probe along with an extra set of JJ's 6V6's a pair of JJ's 5751, and a pair of Tung Sol 6V6's.

I decided to first check the OEM bias with the OEM JJ's tubes.
Couldn't get a bias reading using DCV. Meter would display "OL" and beep.
Double checked the bias probes instructions and found that Eurotubes does not use the resistor type of probe allowing one to use DCV to read as milliamps.

My Radio Shack meter is an auto-ranging digital meter but it wouldn't read milliamps.
Got my analog meter out, set it to 250mA range.
Check the reading and the needle swings quickly to the right past the end of the scale.
This meter has 2 ranges and non of them worked, the needle would fly to the right off the scale.

I tried the proble on the other tube and other socket, same results.
I then tried the new JJ's tubes, same result.
Then I tried the new Tung Sol tubes, same result.
Yes, I also tried adjusting the bias trim pot to make sure bias wasn't way out of range, it wasn't.
Making sure to not red plate the tubes I did try extreme clockwise and counterclockwise to see if the reading changed, it didn't.

I think there is something odd or wrong with this probe.
I use both of my meters to test and adjust bias on other amps.
Just used my digital meter to adjust my Egnater amp as I put the stock tubes back in.
The Egnater has external test points and you use DCV to get the reading.
Eurotubes for whatever reason decided not to make their probe with the resistor in place so that one could use the simple DCV meter setting to read bias.

So I don't exactly where Fender set the original bias at this point.
I decided to install the Tung Sol 6V6's and adjusted bias by ear.
At around the same bias point as the OEM JJ's tubes glow looked ok, not hot red or hot orange.
But, there was a bit more hum and hiss than the OEM tubes.
That's one thing my 68 CDR does have and that's a bit of hum and hiss even with no guitar plugged in, though it's not extreme and doesn't bother me at all when actually playing even at low volume.

With new Tung tubes I set the bias to where the hum and hiss was a lot less and then played again.
VERY nice. The tone is still warm yet it's now cleaner, and the harmonic quality has increased.
I like the Tungs tone.
Once I get the bias probe issue sorted I'll do some more testing and swapping to get a better comparison between the JJ's and Tung Sol tubes.
So far setting bias by ear the Tungs win. :)


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Sun Dec 28, 2014 7:17 pm
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Rverb wrote:
Got the Eurotubes bias probe along with an extra set of JJ's 6V6's a pair of JJ's 5751, and a pair of Tung Sol 6V6's.

I decided to first check the OEM bias with the OEM JJ's tubes.
Couldn't get a bias reading using DCV. Meter would display "OL" and beep.
Double checked the bias probes instructions and found that Eurotubes does not use the resistor type of probe allowing one to use DCV to read as milliamps.

My Radio Shack meter is an auto-ranging digital meter but it wouldn't read milliamps.
Got my analog meter out, set it to 250mA range.
Check the reading and the needle swings quickly to the right past the end of the scale.
This meter has 2 ranges and non of them worked, the needle would fly to the right off the scale.

I tried the proble on the other tube and other socket, same results.
I then tried the new JJ's tubes, same result.
Then I tried the new Tung Sol tubes, same result.
Yes, I also tried adjusting the bias trim pot to make sure bias wasn't way out of range, it wasn't.
Making sure to not red plate the tubes I did try extreme clockwise and counterclockwise to see if the reading changed, it didn't.

I think there is something odd or wrong with this probe.
I use both of my meters to test and adjust bias on other amps.
Just used my digital meter to adjust my Egnater amp as I put the stock tubes back in.
The Egnater has external test points and you use DCV to get the reading.
Eurotubes for whatever reason decided not to make their probe with the resistor in place so that one could use the simple DCV meter setting to read bias.

So I don't exactly where Fender set the original bias at this point.
I decided to install the Tung Sol 6V6's and adjusted bias by ear.
At around the same bias point as the OEM JJ's tubes glow looked ok, not hot red or hot orange.
But, there was a bit more hum and hiss than the OEM tubes.
That's one thing my 68 CDR does have and that's a bit of hum and hiss even with no guitar plugged in, though it's not extreme and doesn't bother me at all when actually playing even at low volume.

With new Tung tubes I set the bias to where the hum and hiss was a lot less and then played again.
VERY nice. The tone is still warm yet it's now cleaner, and the harmonic quality has increased.
I like the Tungs tone.
Once I get the bias probe issue sorted I'll do some more testing and swapping to get a better comparison between the JJ's and Tung Sol tubes.
So far setting bias by ear the Tungs win. :)


Head down to Harbor Freight and pick up a cheap DMM that will read mAs.

Or, try this probe:
https://www.tubedepot.com/products/tubedepot-bias-scout-kit

Works great for cheap and will also read plate voltage. Your present DMM will work. Downside-you have to put it together.....


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Sun Dec 28, 2014 8:22 pm
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No offense, but it sounds like operator error. :o

It's mA, not mV.

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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Mon Dec 29, 2014 2:33 pm
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Posts: 303
shimmilou wrote:
No offense, but it sounds like operator error. :o

It's mA, not mV.


Non taken. mA is what I was working with and what I set my meter to.


Last edited by Rverb on Mon Dec 29, 2014 2:50 pm, edited 2 times in total.

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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Mon Dec 29, 2014 2:39 pm
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Joined: Fri Jun 20, 2014 2:07 pm
Posts: 303
t-luxe wrote:
Rverb wrote:
Got the Eurotubes bias probe along with an extra set of JJ's 6V6's a pair of JJ's 5751, and a pair of Tung Sol 6V6's.

I decided to first check the OEM bias with the OEM JJ's tubes.
Couldn't get a bias reading using DCV. Meter would display "OL" and beep.
Double checked the bias probes instructions and found that Eurotubes does not use the resistor type of probe allowing one to use DCV to read as milliamps.

My Radio Shack meter is an auto-ranging digital meter but it wouldn't read milliamps.
Got my analog meter out, set it to 250mA range.
Check the reading and the needle swings quickly to the right past the end of the scale.
This meter has 2 ranges and non of them worked, the needle would fly to the right off the scale.

I tried the proble on the other tube and other socket, same results.
I then tried the new JJ's tubes, same result.
Then I tried the new Tung Sol tubes, same result.
Yes, I also tried adjusting the bias trim pot to make sure bias wasn't way out of range, it wasn't.
Making sure to not red plate the tubes I did try extreme clockwise and counterclockwise to see if the reading changed, it didn't.

I think there is something odd or wrong with this probe.
I use both of my meters to test and adjust bias on other amps.
Just used my digital meter to adjust my Egnater amp as I put the stock tubes back in.
The Egnater has external test points and you use DCV to get the reading.
Eurotubes for whatever reason decided not to make their probe with the resistor in place so that one could use the simple DCV meter setting to read bias.

So I don't exactly where Fender set the original bias at this point.
I decided to install the Tung Sol 6V6's and adjusted bias by ear.
At around the same bias point as the OEM JJ's tubes glow looked ok, not hot red or hot orange.
But, there was a bit more hum and hiss than the OEM tubes.
That's one thing my 68 CDR does have and that's a bit of hum and hiss even with no guitar plugged in, though it's not extreme and doesn't bother me at all when actually playing even at low volume.

With new Tung tubes I set the bias to where the hum and hiss was a lot less and then played again.
VERY nice. The tone is still warm yet it's now cleaner, and the harmonic quality has increased.
I like the Tungs tone.
Once I get the bias probe issue sorted I'll do some more testing and swapping to get a better comparison between the JJ's and Tung Sol tubes.
So far setting bias by ear the Tungs win. :)


Head down to Harbor Freight and pick up a cheap DMM that will read mAs.

Or, try this probe:
https://www.tubedepot.com/products/tubedepot-bias-scout-kit

Works great for cheap and will also read plate voltage. Your present DMM will work. Downside-you have to put it together.....


The analog meter I have reads mA, which is what this probe is intended to read.
I saw that probe from Tubedepot. I decided to go with the quick route and get the one from eurotubes.

I have 2 meters. One is digital auto ranging but doesn't read mA. The other meter is an analog meter that does read mA, which is what the current probe is designed for.
I'll keep at it.


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Mon Dec 29, 2014 5:11 pm
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Rverb wrote:
t-luxe wrote:
Rverb wrote:
Got the Eurotubes bias probe along with an extra set of JJ's 6V6's a pair of JJ's 5751, and a pair of Tung Sol 6V6's.

I decided to first check the OEM bias with the OEM JJ's tubes.
Couldn't get a bias reading using DCV. Meter would display "OL" and beep.
Double checked the bias probes instructions and found that Eurotubes does not use the resistor type of probe allowing one to use DCV to read as milliamps.

My Radio Shack meter is an auto-ranging digital meter but it wouldn't read milliamps.
Got my analog meter out, set it to 250mA range.
Check the reading and the needle swings quickly to the right past the end of the scale.
This meter has 2 ranges and non of them worked, the needle would fly to the right off the scale.

I tried the proble on the other tube and other socket, same results.
I then tried the new JJ's tubes, same result.
Then I tried the new Tung Sol tubes, same result.
Yes, I also tried adjusting the bias trim pot to make sure bias wasn't way out of range, it wasn't.
Making sure to not red plate the tubes I did try extreme clockwise and counterclockwise to see if the reading changed, it didn't.

I think there is something odd or wrong with this probe.
I use both of my meters to test and adjust bias on other amps.
Just used my digital meter to adjust my Egnater amp as I put the stock tubes back in.
The Egnater has external test points and you use DCV to get the reading.
Eurotubes for whatever reason decided not to make their probe with the resistor in place so that one could use the simple DCV meter setting to read bias.

So I don't exactly where Fender set the original bias at this point.
I decided to install the Tung Sol 6V6's and adjusted bias by ear.
At around the same bias point as the OEM JJ's tubes glow looked ok, not hot red or hot orange.
But, there was a bit more hum and hiss than the OEM tubes.
That's one thing my 68 CDR does have and that's a bit of hum and hiss even with no guitar plugged in, though it's not extreme and doesn't bother me at all when actually playing even at low volume.

With new Tung tubes I set the bias to where the hum and hiss was a lot less and then played again.
VERY nice. The tone is still warm yet it's now cleaner, and the harmonic quality has increased.
I like the Tungs tone.
Once I get the bias probe issue sorted I'll do some more testing and swapping to get a better comparison between the JJ's and Tung Sol tubes.
So far setting bias by ear the Tungs win. :)


Head down to Harbor Freight and pick up a cheap DMM that will read mAs.

Or, try this probe:
https://www.tubedepot.com/products/tubedepot-bias-scout-kit

Works great for cheap and will also read plate voltage. Your present DMM will work. Downside-you have to put it together.....


The analog meter I have reads mA, which is what this probe is intended to read.
I saw that probe from Tubedepot. I decided to go with the quick route and get the one from eurotubes.

I have 2 meters. One is digital auto ranging but doesn't read mA. The other meter is an analog meter that does read mA, which is what the current probe is designed for.
I'll keep at it.

Hmm...Do you have your red test lead plugged into the meter's red "mA" hole and the black lead into common? What's the lowest scale for mA's on the meter?


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Mon Dec 29, 2014 11:20 pm
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That is what I meant, separate input for current. :?:

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Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Tue Dec 30, 2014 9:20 pm
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The JJ 6V6 is a cross between a 6L6 and a 6V6. It's not really a 6V6 at all. I like the EH 6V6's. You can sometimes find Philips USA 6V6GT's, which were the Kmart of American tubes in my opinion, but still better than anything made today. The military needed some tubes in the 1980's and contracted Philips ECG to make some, so you can still find them. They are more expensive than they once were, because supplies are dwindling.

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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Tue Dec 30, 2014 11:04 pm
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Yeah, if you look at the guts of the JJ --- it looks more like a 5881/6L6WGB anode plate assembly. In a taller bottle than the standard 6V6GT.

Image

Image

Image


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Post subject: Re: 6V6 tubes & 68 CDR
Posted: Sun Jan 11, 2015 12:20 pm
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t-luxe wrote:
Rverb wrote:
[

The analog meter I have reads mA, which is what this probe is intended to read.
I saw that probe from Tubedepot. I decided to go with the quick route and get the one from eurotubes.

I have 2 meters. One is digital auto ranging but doesn't read mA. The other meter is an analog meter that does read mA, which is what the current probe is designed for.
I'll keep at it.

Hmm...Do you have your red test lead plugged into the meter's red "mA" hole and the black lead into common? What's the lowest scale for mA's on the meter?


No problem with identifying and using the correct leads on my end. :)
But thanks for checking cause sometimes the simplest things end up being the problem.
In this case unfortunately it wasn't that simple.

The analog meter has adequate scale for testing power tubes, that wasn't the problem.
Also it only has 2 probes, and there is no separate lead input for mA.
I had thought that the fuse was blown on my old meter, and it was.
But after replacing it it still didn't work.
The problem is simply that that meter, for whatever reason, wasn't able to read the current.

Finally had time to get a new meter after the holidays.
Got a cheapy cen-tech from harbor for $6 and it works.
Well, for $6 it works.
The new cheapy meter does just fine.

Now back to the amps.
Both amps, CDR and CVR, were biased cold at factory. The CVR really really cold, around 17mA.
I put in a new matched pair of SED Winged C 6L6's into the CVR and set bias to around 42mA.
Oh my!
I liked the tones from the CVR before but felt it could use some warming up.
With the hotter and more correct bias the tone has really warmed up and quite nicely too.
Plus I am a big fan of Winged C 6L6's and they are truly not disappointing me here in this application.
The tone and harmonic quality are fantastic.
These tubes didn't sound so great in the HRdlx 3 I had, but a completely different story in the 68 CVR.

On the CDR I swapped in the new Tung Sol 6V6's and set bias to about 20-21mA.
Yet another "wow" moment.
Originally I had set the Tungs by ear mainly reducing idle hiss and hum, but on the meter bias was around 7-8mA, very cold. Surprising that it sounded good.
But I decided to ignore the light hiss and hum and go for a hotter bias and it has paid off very very nicely.
Super rich and harmonic tone.
I played for an hour straight plugging straight into both amps no effects, no pedals just my Strat straight in and the tones were beautiful, fantastic, harmonic, and rich.
This is why I switched to Fender amps, THE TONE!

On a different note.
A super nice ebay seller sent me 9 NOS pre amp tubes for FREE! I was interested in buying a couple of NOS Jan 5751's that got sold before he got back to me so he sent me the tubes for free just to try them out.
Now how cool is that in this day and age?!
Now these aren't brand new unused tubes, but still a wonderful gesture.
He tells me that all but 1 tests very good, but he said to try the one that tests poorly as it may sound good or have a unique tone.
The tubes are a mix of 5751's and 12ax7's.
These are all old tubes, Wurlitzer, Siemans, unknown USA stamped, GE, and a couple I can't read.

I also purchased a couple of new JJ's 5751's and a NOS Jan 5751 so I've got a lot of pre tubes to test out.

Thanks to everyone who offered helpful advice.
It's play'in time!


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