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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 372

post #5566 of 7003
Quote:
Originally Posted by hypnos1 View Post
 

 

Ah so - some while back when I put out feelers for possible use of 6AS7s and 6080s as powers I assumed there were other factors going against their use in our LDs...eg. plate dissipation 13W (6080). Was I worrying unduly, and do we just need to provide an external heater supply of 2x 2.5A (6080) to be safe? If so , these 6080s sure do look interesting...

 

 

 

Now this is another real problem to use 6AS7's as powertube with LD. With 150ohm cathode resistors 6AS7 could hog 4-5 times the current what 6N6P uses! I think LD does not have enough anode current. And LD resistors can't stand the heat. Cathode resistors should be 10W.

 

Quote:
Originally Posted by mordy View Post
 

Hi Artsi and Gibosi,

 

A 6BX7 tube is on the way which uses a 1.5A heater - should not be a problem for my 5A voltage regulator and power supply.

 

Re the 6AS7, 6080 and similar tubes with a low amp factor of 2, what would be the result using such a tube as a driver in the LD MKIII together with my 110W ss Sony amp driving speakers?

 

As it is now, the LD volume control is always set at near clipping (around 3o'clock), and the Sony volume is on low. (As a comparison, when using headphones I cannot use a higher setting on the LD than 9 o'clock without risking my hearing.)  The Sony amp has a LED bar graph that indicates less than 1-2W (!) to get more than adequate listening levels. If I play really loud and go higher than say 30W on this meter I experience audible hum (that may be masked by the music).

 

Using the 6AS7 etc tubes, would I need to increase the volume level substantially? The tube I am using now, the 8FQ7, has an amplification factor of 20.

 

.

When coming to gain 6BX7 and 6AS7, 6BX7 should work ok and 6AS7 could be 5x quieter. 5998 is better option with amp factor of 5.5. :D 


Edited by Artsi - 3/23/14 at 8:37pm
post #5567 of 7003

With my hybrid LD, rolling power tubes is not even an option, and so recently, I have been trying to figure out what amp I should buy next. Given my considerable investment in 6SN7 and ECC40 tubes, both in time and in dollars, I would prefer to be able to use them in my next amp. Moreover, I would also like to be able to roll 6AS7-type power tubes. At this time, the Bottlehead Crack looks very attractive to me. It is quite affordable and, further, it is directed to the DIY crowd. I have heard reports that 6SN7s are quite noisy in the Crack, but similar to the LD, it appears to be possible to use an external DC power supply.

 

Having just purchased new headphones, I won't be purchasing another amp anytime soon, but thought I would throw this out to see what others think.

 

Cheers

post #5568 of 7003

Friendly words of advise if your considering getting new gear :                                                                                                                                                                                                                                                                                                                                                                                                                                                 

post #5569 of 7003

I an octal 6N7 tube compatible with the LD MKIII? This tube is all metal - any info about the sonic characteristics?

post #5570 of 7003
Quote:
Originally Posted by mordy View Post
 

I an octal 6N7 tube compatible with the LD MKIII? This tube is all metal - any info about the sonic characteristics?

 

This double triode has a common cathode. That is, two anodes, two grids and only one cathode. And so the 6N7 is not pin compatible with a 6SN7, and thus is not a good candidate for tube rolling in our LDs 

post #5571 of 7003

Thanks - you saved me from a wrong purchase

post #5572 of 7003
Quote:
Originally Posted by Artsi View Post
 

 

Now this is another real problem to use 6AS7's as powertube with LD. With 150ohm cathode resistors 6AS7 could hog 4-5 times the current what 6N6P uses! I think LD does not have enough anode current. And LD resistors can't stand the heat. Cathode resistors should be 10W.

 

 

 

Many thanks Artsi...your greater knowledge has reinforced my gut feeling that all may not be well moving in this direction. And reinforced my belief that my current combo of C3GS and Psvane (on MKIV SE) has reached a level that would be very hard indeed to surpass. I am one REALLY happy LD owner, and do not even feel the need to move to another camp (or spend a vast amount of money on new headphones)...I have so many people to thank for this fascinating, rewarding and enjoyable journey...

 

Cheers everyone...

post #5573 of 7003

Re: Mordy's recent question about inexpensive headphones

 

I have never heart these, but this might be a good deal:

 

Sennheiser 558's for 50% off -  $89.97 + free shipping

 

http://slickdeals.net/f/6808062-sennheiser-hd-558-headphones-50-off-89-97-plus-free-shipping

post #5574 of 7003

Hi Gibosi,

 

Thanks for the suggestion. As a rule, I always go to Amazon.com to check prices and customer reviews. IMHO you can really on them if there are many customer reviews. In this case there are almost 240 reviews, the overwhelming majority very positive.

 

As part of my research I always start reading the negative reviews. In this case they are almost nil which is a very good sign. There seems to be a long term quality issue with the plastic headband cracking after time, but it may have been fixed - there is a two year warranty.

 

Some reviewers describe the sound as dark. Personally, I prefer an open, airy and lively sound. Don't know how much an improvement these would be over my Audio Technica ATH AD700 ($65 B stock) headphones. Saw a pair of HD700 used going for  $544....

 

http://www.amazon.com/Sennheiser-504631-HD-558-Headphones/product-reviews/B004FEEY9A/ref=sr_1_1_cm_cr_acr_txt?ie=UTF8&showViewpoints=1

post #5575 of 7003
Quote:
Originally Posted by mordy View Post
 

Hi Gibosi,

 

Thanks for the suggestion. As a rule, I always go to Amazon.com to check prices and customer reviews. IMHO you can really on them if there are many customer reviews. In this case there are almost 240 reviews, the overwhelming majority very positive.

 

As part of my research I always start reading the negative reviews. In this case they are almost nil which is a very good sign. There seems to be a long term quality issue with the plastic headband cracking after time, but it may have been fixed - there is a two year warranty.

 

Some reviewers describe the sound as dark. Personally, I prefer an open, airy and lively sound. Don't know how much an improvement these would be over my Audio Technica ATH AD700 ($65 B stock) headphones. Saw a pair of HD700 used going for  $544....

 

http://www.amazon.com/Sennheiser-504631-HD-558-Headphones/product-reviews/B004FEEY9A/ref=sr_1_1_cm_cr_acr_txt?ie=UTF8&showViewpoints=1

                                                                                                   

post #5576 of 7003

Hi,

 

Today I received the little 9 pin socket savers to be used as socket extenders. They came with a speedboat from China - only 9 days (I'm glad that I took my own advice and did not order from Hong Kong which took 30 days. The US Post Office has a small packet deal with China where the vendor in China can use a tracking number that can be tracked through USPS.)

 

These socket savers fit inside the decorative rings around the sockets on my LD MKIII, enabling me to use 6SN7 tubes as power tubes with an octal to 6CG7 adapter (thanks mab1376). I picked a pair of 60's RCA 6SN7 tubes that are among my best driver tubes, now to be used as power tubes.

 

By coincidence, the GE 6BX7GT tube arrived today as well. This tube draws 1.5A, but I upgraded my voltage regulator to a 5A model, so this should not be a problem (the old one was rated for 2-3A).

 


I am pleased to report that this tube has no problem with volume, although the amplification factor is 10 and half of what I was using. Maybe I have to turn up my ss amp one notch, but no problem at all.

 

Before I used the the BX tube I had used a 6SN7 tube as driver. The voltage regulator has an easy way to calibrate it to make the LED readout correspond to the measurements of a multimeter. I had it set to 6.3V at the tube pins.

 

 

On the bottom of the regulator on each side of the red LED display are two little push buttons. You push in the right button and hold it for two seconds and let go. The display flashes, and you can increase or decrease the readout numbers by pushing the right or left button.

 

A curiosity: The voltage at the BX tube pins dropped half a volt when I inserted the BX tube. In order to get it up to 6.3V I had to adjust the regulator to 6.77V (It shows 6.7V).

 

Thanks Nic Rhodes for your comments on the 6BL7 and 6BX7 tubes. First impression is that this really is a cracking tube! In American English we would say awesome!

 

I think we'll call it a cracking tube to keep it a secret so I can buy great sounding octals for less than $4...LOL

 

Anyhow, the clarity, soundstage and sweet midrange are astounding. The bass is very powerful. There is a little brightness in the presentation, but I don't know if the tube is new or if I have to pair it with different power tubes. Toe tapping index is 5+

 

The BX runs hot, too hot to touch, the power tubes are moderately hot, but the amp itself is cool as a cucumber.

 

The sound is mesmerizing....

 

Anyhow, this is a first impression, so tentative...

 

Happy tube rolling!


Edited by mordy - 3/24/14 at 9:14pm
post #5577 of 7003
Quote:
Originally Posted by mordy View Post
 

Hi,

 

Today I received the little 9 pin socket savers to be used as socket extenders. They came with a speedboat from China - only 9 days (I'm glad that I took my own advice and did not order from Hong Kong which took 30 days. The US Post Office has a small packet deal with China where the vendor in China can use a tracking number that can be tracked through USPS.)

 

These socket savers fit inside the decorative rings around the sockets on my LD MKIII, enabling me to use 6SN7 tubes as power tubes with an octal to 6CG7 adapter (thanks mab1376). I picked a pair of 60's RCA 6SN7 tubes that are among my best driver tubes, now to be used as power tubes.

 

By coincidence, the GE 6BX7GT tube arrived today as well. This tube draws 1.5A, but I upgraded my voltage regulator to a 5A model, so this should not be a problem (the old one was rated for 2-3A).

 


I am pleased to report that this tube has no problem with volume, although the amplification factor is 10 and half of what I was using. Maybe I have to turn up my ss amp one notch, but no problem at all.

 

Before I used the the BX tube I had used a 6SN7 tube as driver. The voltage regulator has an easy way to calibrate it to make the LED readout correspond to the measurements of a multimeter. I had it set to 6.3V at the tube pins.

 

 

On the bottom of the regulator on each side of the red LED display are two little push buttons. You push in the right button and hold it for two seconds and let go. The display flashes, and you can increase or decrease the readout numbers by pushing the right or left button.

 

A curiosity: The voltage at the BX tube pins dropped half a volt when I inserted the BX tube. In order to get it up to 6.3V I had to adjust the regulator to 6.77V (It shows 6.7V).

 

Thanks Nic Rhodes for your comments on the 6BL7 and 6BX7 tubes. First impression is that this really is a cracking tube! In American English we would say awesome!

 

I think we'll call it a cracking tube to keep it a secret so I can buy great sounding octals for less than $4...LOL

 

Anyhow, the clarity, soundstage and sweet midrange are astounding. The bass is very powerful. There is a little brightness in the presentation, but I don't know if the tube is new or if I have to pair it with different power tubes. Toe tapping index is 5+

 

The BX runs hot, too hot to touch, the power tubes are moderately hot, but the amp itself is cool as a cucumber.

 

The sound is mesmerizing....

 

Anyhow, this is a first impression, so tentative...

 

Happy tube rolling!

 

 

Glad you're up and running! I'm waiting on a pair of c3gs and some adapters I commissioned from an ebay member who makes custom adapters.

 

Hopefully my 6SN7GTB synergizes as well as Hypnos1's cv181-z with the c3gs'.

post #5578 of 7003

Mordy;

your rig there is very fascinating.

please excuse that I don't know exactly what all you have hooked up there, or that I may have missed the place you identified what all you have wired into what...

 

any chance you could post up a simple diagramme, or maybe just re-post the pic with some labels superimposed?

 

I'm big on tube rolling adventures but I don't know the nitty-gritty electronics side of it as much as I'd like.

What you are doing is very interesting.

 

 

So...I know I am asking a much repeated question; can one run a 6CY7 in a LD 1?

 

thanks so much!

:smile:

post #5579 of 7003

Hi DogMeat,

 

Basically I have a breadboard with a 9 pin socket with two 7 pin Vector adapters connected that allows me to use 12AX7 or 6DJ7 tube families (with different wiring) or octal tubes with an adapter in my LD MKIII. For tubes used as drivers that draw more than 0.5A an external power supply and voltage regulator is required.

 

The latest post shows how you can use 6SN7 tubes as power tubes with the appropriate adapters.

 

The 6CY7 tube draws 0.75A which means that you need an external power supply if it is used a driver. For the suitability for the LD MkI which I do not have experience with, I refer you to Gibosi who has been extremely helpful with all these types of questions.

 

Once it has been determined which tube family the pinout of this tube corresponds to, and if it is suitable, you can build an adapter. There are many posts on this thread with wiring diagrams and how to instructions.

 

Good luck!

post #5580 of 7003

:cool:

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