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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old Yesterday, 03:09 PM   #71
colnago55 is offline colnago55  United States
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Hi George,

Here's another suggestion for the revised board.

Would it be possible to change the orientation of the power sockets so that the tube labels will face forward? I believe this would mean that pins two and three are in the rear and pins one and four are in front.

I like the suggestion of adding a center mounting point to add stability to the board.

take care, Jacques
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Old Yesterday, 05:50 PM   #72
rmyauck is offline rmyauck  Canada
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How about the in production ECC99 for driver?

JJ Electronic - ECC99
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Old Yesterday, 06:58 PM   #73
w5jag is offline w5jag  United States
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Mu looks low; I think 5842 is in the low 40's.

Win W5JAG
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Old Yesterday, 09:10 PM   #74
Tubelab_com is offline Tubelab_com  United States
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Quote:
So no viable alternatives to the 5842?
I went through every tube in my collection back when I designed the TSE, and found nothing that works as good as the 5842 or the WE417A.

About this time last year I rigged up a TSE board to test some tubes. I had a bunch of WE471A's that I was selling, and they had to be tested. I used a TSE board without any output tubes to test and match about 15 417A's and 50 some 5842's. Each tube was driven with an audio signal generator to approximately 100 volts P-P output, adjusted for minimum distortion, and the DC, gain and distortion readings recorded.

As expected the WE tubes had lower gain (their Mu is 44) compared to the Raytheon 5842's (Mu = 50). The WE's were more consistent in the DC voltage readings and produced the lowest distortion. How many tubes can make 100 volts P-P at less than 1/2 percent THD? Most of the WE 417's did.

The Raytheon 5842's were less consistent in DC bias which is why there is an adjustment pot in the cathode circuit. All but a couple of these tubes were below 1% THD at 100 volts P-P. ALL tubes were used pulls from old military and telephone company spare equipment.

I have recently gone through several more possible choices for driver tubes, but nothing I have tested is consistently this good. The 5842 was fairly common and about $5 each when I designed the TSE. Any new choice that isn't current production must be available in fairly large quantities, and that is another design criteria that must be considered. Will there be a TSE-III if and when I find one? I don't know, but I do know that the TSE will be long forgotten if I hold up the TSE-II until I find it. For now the 5842 must remain.

Quote:
How about 6C45pi?
I don't have any 6C45's, and I would need several to find out if they were suitable. It seems that it's one of those love it, or hate it kind of things from it's reputation. At this stage of the game I'm hesitant to mess with a successful design until I have the time and funds to do some extensive testing.

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E180F is also suggested.....How about the in production ECC99
The ECC99 does fall short in gain. Even the WE417A is marginal if driven from a low output source.

Like it or not, the TSE has garnered an "audiophile" type reputation in stark contrast to its early days when many people cried foul because of the silicon in the signal path. More than once it was suggested that I change my company name to Transistorlab.

There are still plenty of people who refuse to try it, but that is now the minority. There would likely be resistance to using a triode wired pentode as the driver even though there ARE some that work quite well. Consistency is still an issue. Another possible choice for a driver is the venerable 12AX7. SOME of them can produce astoundingly low distortion numbers, but some really suck. How does an end user without test equipment know which is which? .....these possibilities will be explored in depth in the modular "building block" versions of the TSE and other designs.

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change the orientation of the power sockets so that the tube labels will face forward?
Every tube is different. You can see the labels on the front of my 2A3's in the board the way it is now. It would take a complete redesign of the board to move those two FAT traces capable of carrying 2.5 amps. That's not possible now that I have a working board that just needs minor tweaks.

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I like the suggestion of adding a center mounting point
That one was on my list as the SSE already has 5 holes, and I missed it. I am in the process of fitting it in now, which will mean one or two more test board spins before sending the board out.

Quote:
label the parts on both sides of the board to facilitate dual side assembly?
That is possible. I need to see If my board house will do it, and how much it will add to the price.
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Old Today, 02:37 AM   #75
tubestyle is offline tubestyle  Canada
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Would a company like JJ accept the challenge of making a new tube with similar specs? Other manufacturers?
Just curious what triggers a new model for these companies... Can we convince them there is a market for them?
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Old Today, 03:52 AM   #76
Captn Dave is offline Captn Dave  United States
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Originally Posted by tubestyle View Post
Would a company like JJ accept the challenge of making a new tube with similar specs? Other manufacturers?
Just curious what triggers a new model for these companies... Can we convince them there is a market for them?
Let’s say JJ or Electro-Harmonix we’re to do a 417A reissue, the central question would be whether they have the ability to repeatably achieve the low distortion figures of the originals.

Those originals were made by Western Electric to service their own needs. Namely a low distortion tube that would allow amplification of a multiplexed signal with many hundreds of calls without creating crosstalk. It was a demanding application and poor performance was obvious. If you’re old enough, you will have experienced long distance calls with someone else joining your conversation.

While I’m thankful that these companies are in business and generally satisfied with their products , I’m a bit sceptical that they could produce an equivalent 417A and make a profit doing so.
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