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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 9th July 2019, 05:48 PM   #411
itsikhefez is offline itsikhefez  United States
diyAudio Member
Join Date: Aug 2015
After a 14 year run, the TSE must DIE!
The mocked up TSE-II is playing pretty sweet music through my HD650.

There are a few open issues I will be exploring, sharing here in case this information is useful:

1) There is some small amount of hum when no music is playing.
Initially, I measured around 8mV AC on the OPT.
As an experiment, I changed the PS to CLCRC, using the 60uF motor RUN as the second cap, and adding a 300R resistor.
Simulation showed this should bring ripple down, and indeed I was measuring 1mV AC after that. This reduced the hum but it was still audible. (I tried this with shorted inputs to eliminate any pot/input related issues)
I think this is due to the headphone application- 5K:32 OPT's and sensitive high impedance cans. I highly suspect that this would silent with speakers and 5K:8 OPT's.
Next, I will experiment with either CLCLC (as randytsuch tried) or a HV B+ regulator.

2) Loading resistors. Without any resistors, there is plenty of volume on the 300ohm HD650 with pot midway. Although, this puts a reflected load of 46K on the 45's.. Based on previous discussions, there was not a clear answer on whether this is a problem or not. The experiment shows the power is sufficient.. but does this cause frequency roll-off or distortion? I cannot know without proper testing tools.
Anyhow, I experimented with a 100R resistor in parallel. Volume range is about the same (hard to tell in mockup), but I _think_ the sound was improved.. better clarity overall. I'll have to continue experimenting in my real setup with a proper source.

3) Power transformer buzz. I'm using the Hammond 370EX. People mentioned they did not get buzz from the 300 series. The buzz I hear is audible only when putting the ear very close, less than half a foot.
Is this expected, or are the Edcor / Custom PT completely silent ?
The 370EX has 144mA, maybe it is over-utilized ? I read somewhere that you want only about 70% of the PT loaded to avoid noise.
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Last edited by itsikhefez; 9th July 2019 at 05:52 PM.
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Old 14th July 2019, 06:55 AM   #412
itsikhefez is offline itsikhefez  United States
diyAudio Member
Join Date: Aug 2015
After a 14 year run, the TSE must DIE!
On Tubelab website it is mentioned:
> The 45 should be biased in the 25 to 30 mA range. I use 28 to 30 mA on 280 volts, and 26 or 27mA if operated at 320 volts.

Based on the RCA data sheet, at 275V it should be 36mA (or am I understanding this wrong?)

If this is the case, any reason to prefer 30mA over 36mA in 275-280V range?
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Old Yesterday, 07:12 PM   #413
diecast is offline diecast  United Kingdom
diyAudio Member
Join Date: Jul 2009
Default Surplus Parts for TSE - including original version specific

I have parts accumulated for the original TSE that I will never complete now. I gathered most of them years ago so there a number of now obsolete parts that came from reputable sources when they still carried them. Would anyone be interested in:
  • 16 x 2SK2700 (yes, lots!)
  • 23 x NDF02N60ZH (even more...)
  • 2 x PQ5EV5
  • 3 x the double heatsinks (=one set)
  • Snap in 450v caps - 100uF, 150uF, 220uF and 470uF
  • A bunch of different values for R14/R25
These are all new / unused. I also have a few bonus used bits and bobs. So - does anyone out there have an original TSE board they want to complete? Or one they want to fix? I am located in the UK.

Last edited by diecast; Yesterday at 07:41 PM.
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