What 300b's are you running?

[debk]

What 300b tubes are you running in your BeePre?

I have tried both the Gold Lion  and the Psvane 300b-t.  I like the Psvane better.  Sounds  a little more detailed than the gold lion tube.

Anyone have any other suggestions to try?  All the EML 300b seem to have a higher than standard filament current.

Deb

 

[johnsonad]

EML will not work in the amp.

I'm using EH 300B gold grids. They are the only tube I have.....  This is an expensive preamp to roll tubes in.

It would be nice to find someone in SoCal with a stash of different 300B's that would be willing to spend some time with the BeePre at my place.

 

[ditdah]

I thought the EML 300b's would work fine...but the EML 300b-mesh was not recommended.  Can you confirm the EML 300b's won't work?  I could have sworn that I was told the EML 300b's would be just fine for both the Paramounts and the BeePre.

 

[debk]

The regular EML 300b has a filament current of 1.3A, slightly higher than the 1.25A most 300b are.  Don't know if the 1.3A is just 1.25A rounded up or the tube does draw slightly higher filament current than the standard 300b tubes.

I don't know how close the specs are for the filament power supply in the BeePre are, will the extra 50mA make a difference?

Debra

 

[ditdah]

Admittedly...I guess I'm talking more Paramount than BeePre...  but I'm hoping the EML 300b's are fine for either.  As for the 50mA question...I'm going to have to defer to someone more knowledgeable.

 

[johnsonad]

There is a thread on it already. Unless you want to put your beePre in a fridge to keep it cool, EML tubes will not work in the BeePre (they work fine in the Paramount). They all draw too much current and with the highly regulated filament supply you will starve the tubes. You could adjust the regulator which PJ says is possible (and the transformer has the reserve) but at the cost of more heat. I asked Jac and he of course said he will not warrenty the tubes if they are not run to proper current.

We should focus on the tubes we can use safely in the BeePre and keep on Bottlehead to add this adjustablility to version 1.1. Or if someone wants to adjust their regulators and spend a good amount of change to try it, please post your results and temp readings of the BeePre. I really want to use EML myself, don't get me wrong but I also want the tubes and the preamp to have a long and happy life.

 

[debk]

The other thread is mainly about the EML mesh plate 300b which has a filament current of 1.5A.  That we know will not work
Is there enough reserve for the 1.3A draw of the solid plate EML 300b in an unmodified BeePre?

Deb

 

[Frihed89]

Has anyone tried the Shuguang 300BC solid graphite plates?  I have a pair in an Audio Note Meishu integrated, replacements for some low mileage WE 300Bs I'm saving for a rainy day.  The Shuguans aren't WEs, but they are better all around then the EH's that came with the amp when I bought it used.

 

[Doc B]

Not sure how many folks will want to cough up nearly as much for tubes as they pay for our kit. I'm thinking that the best approach might be to offer a separate mod kit that allows changing the circuit to work with the EMLs - which would necessarily make it incompatible with 300Bs.

Perhaps Jac could be persuaded to loan us a pair of tubes to develop the necessary mods with.

 

[ditdah]

hmm...well...  I bought 3 pair of EML 300b's.  pfft.

ok...I'm sure it was mentioned previously, but to avoid any further ordering mistakes, exactly which tube should I get for the BeePre?  The Psvane 300b-TII's?

 

[johnsonad]

Not sure how many folks will want to cough up nearly as much for tubes as they pay for our kit. I'm thinking that the best approach might be to offer a separate mod kit that allows changing the circuit to work with the EMLs - which would necessarily make it incompatible with 300Bs.

Perhaps Jac could be persuaded to loan us a pair of tubes to develop the necessary mods with.

maybe so! Would you guys be willing to send the email to Jac? 

If such a kit was to be produced, it would be nice if it could have the resistors and specs to change the regulators along the full range of current draw, from stock 1.2 A to 1.5 A.

I would buy the kit in a heart beat and I bet most current BeePre owners would too. EML tubes are hard to beat if you are willing to pay for them.

 

[johnsonad]

The other thread is mainly about the EML mesh plate 300b which has a filament current of 1.5A.  That we know will not work
Is there enough reserve for the 1.3A draw of the solid plate EML 300b in an unmodified BeePre?

Deb

Deb the way I understand it the current is regulated to 1.2 amps, not 1.25 amps. Hopefully PJ will weigh in on the 1.3 amp load.

 

[Doc B]

A 300B preamp is not a trivial pursuit as can be guessed by the number of them on the market. It turned out to require some pretty unique design elements to work to the sonic standard we require. It's quite a bit different than the traditional 300B amp with AC filaments that most 300Bs are made to work with.We supply the kit with EH 300Bs. We have not tried all of the boutique tubes, so I am hesistant to make any recommendation about other tubes unless they meet the standard WE spec for 300B filament voltage and current. The nature of our regulation scheme is such that it has to be modified for any tubes that don't run at the filament spec of the tube the preamp is designed for - a spec 300B. There is also the potential issue of how microphonic a given tube design might be. Again I can't comment on what I haven't heard. If boutique tube manufacturers would like the opportunity to have us recommend their product and they are willing to send us a pair of tubes to work with we can determine if adjustments to the regulator are necessary and if the level of microphony is acceptable for the application.

As regards EMLs, I will let PJ weigh in on that. He has had some discussion with Jac about the requirements of the EML tubes and I'm not sure if they are compatible with the regulation method we use to get the S/N ratio as good as it is.

 

[debk]

Anyone have any experience with the KR audio 300b?

Deb

 

[johnsonad]

Anyone have any experience with the KR audio 300b?

Deb

Please buy a pair and give us a comparison to your PSvane tubes. I've been on the fence with both pair..

I'm actually really happy with the EH gold grids. Mind you, I have nothing to compare them to......

 

[ditdah]

Anyone have any experience with the KR audio 300b?

Deb

Please buy a pair and give us a comparison to your PSvane tubes. I've been on the fence with both pair..

I'm actually really happy with the EH gold grids. Mind you, I have nothing to compare them to......

The KR tube spec for the 300b WE clones are as follows:

Maximum Plate Voltage   550 V 
Maximum Plate Current   120 mA 
Plate Dissipation   50 Watts 
Va   450 V 
Ia   100 mA 
Vg   -90 V 
Transconductance   6.2 mA/V 
Amplification Factor   3.9 
Filament Voltage   5 V (DC/AC) 
Filament Current   1.2 A 

Should I expect these to be acceptable for the BeePre based on the spec?

for comparison...here's the EML 300b specs:

300B Filament Ratings
Filament Voltage 5 Volt (AC or DC)
Tolerance on filament voltage 4%
Filament Current 1.3 Ampere

300B Maximum Conditions  Not possible as operating point
Plate Voltage 450Volt
Plate Current 100mA
Power Output in Class A 17.8 Watt
Plate Dissipation 40Watt (note5)
Grid resistor with Auto Bias 250k Ohm (note4)
Grid resistor with Fixed Bias 50k Ohm (note4)

300B Factory Test conditions
Plate Voltage 300V
Plate Dissipation 17Watt
Plate Current 56mA
Grid Voltage -58Volt
Plate Impedance 700 Ohm
Amplification Factor 3,9
Transconductance 5.6 mA/V

 

[Paul Joppa]

...
As regards EMLs, I will let PJ weigh in on that. He has had some discussion with Jac about the requirements of the EML tubes and I'm not sure if they are compatible with the regulation method we use to get the S/N ratio as good as it is.

Jac is naturally disappointed that the design is not at present flexible enough to accommodate his tubes - well, so am I! The mesh especially has such a great reputation that I would totally love to hear it.

As I have told Jac, I will continue to pursue a design revision - as Doc B said, we have had to do quite a bit of research and have wound up with a more complex and less flexible circuit than we would prefer. Jac has a lot of analysis, good ideas, and good advice for designers on his web site, as well.

I do have a research plan for this issue. It will have payoffs (hopefully) for several upcoming products, including the BeePre. I won't promise a payoff any faster than the DAC project, now 2 years and counting, though. If you can predict or schedule the outcome, then it isn't research!

Meanwhile, yes the regulator has enough current headroom for 1.3 amps. I've done some calculations that suggest a certain amount of flexibility, but I'm not ready to specify anything except the stock tube until I have an adequate body of actual measurements - there are too many variables that seem small but may or may not add up.

For those who have good meters (1% accuracy or better), you might measure the voltage at the filament pins (1 and 4) of the 300Bs and report them. I'll accumulate the body of data, which will help me validate my analysis and also assess parts and build variability.

 

[johnsonad]

Thanks Paul! I'll get you a measurement tomorrow. If 1.3 Amps turns out to be an option I will take EML solid plates over anything else based on only my great experience with his other tubes. 

 

[corndog71]

I would be curious to hear someone's impression of Valve Art 300Bs in the BeePre.  I've enjoyed their EL34 and EL84 tubes in my dynaco amps. 

 

[johnsonad]

For those who have good meters (1% accuracy or better), you might measure the voltage at the filament pins (1 and 4) of the 300Bs and report them. I'll accumulate the body of data, which will help me validate my analysis and also assess parts and build variability.

Here are mine:
EH Gold Grid tubes
Line: 120.2
B4: 9.88
B1: 5.04
A4: 9.82
A1: 4.99

edited for poor typing....