Hi,
I am going to finish an I/V dac stage made of an expensive ECC88.
I was said it is not realy need for an IHT tube that have less 300 V PS and the filament is solid enough whatever the low impedance at switch on and the inrush due to the use of SS rectification.
I wonder if the use of the cool design from Mark Johnson could do the trick for a better life span of such expensive tube or not ? And allow me to have an only start button in spite of one for the heater and one after for the B+. Or we do not care, i.e. not a 300B, look elswhere ? I understand than cathode will not suffer with IHT with rapid start, I just talking about better lifespan maybe.
Here isnthe board description https://www.diyaudio.com/community/...ncludes-soft-start-h9kpxg.354971/post-6216476
I asked Mark Johnson who send me there to ask to tubes guys... Any inputs appreciated 🙂
I am going to finish an I/V dac stage made of an expensive ECC88.
I was said it is not realy need for an IHT tube that have less 300 V PS and the filament is solid enough whatever the low impedance at switch on and the inrush due to the use of SS rectification.
I wonder if the use of the cool design from Mark Johnson could do the trick for a better life span of such expensive tube or not ? And allow me to have an only start button in spite of one for the heater and one after for the B+. Or we do not care, i.e. not a 300B, look elswhere ? I understand than cathode will not suffer with IHT with rapid start, I just talking about better lifespan maybe.
Here isnthe board description https://www.diyaudio.com/community/...ncludes-soft-start-h9kpxg.354971/post-6216476
I asked Mark Johnson who send me there to ask to tubes guys... Any inputs appreciated 🙂
We only normally use a soft start on a power amplifier. It is of no consequence for a valve pre amp and will not improve the life of the valve.
Ensure the heaters are 6.3volts AC, DC needs less for obvious reasons.
I wonder why people are trying to use a valve designed for VHF in an Audio Frequency pre amp ... beats me unless they are cheap.
I would use a 7025 or 12AX7WA/ECC83. At least they are designed for the job and nice and quiet.
Ensure the heaters are 6.3volts AC, DC needs less for obvious reasons.
I wonder why people are trying to use a valve designed for VHF in an Audio Frequency pre amp ... beats me unless they are cheap.
I would use a 7025 or 12AX7WA/ECC83. At least they are designed for the job and nice and quiet.
I am a complete noob with tubes.
My basic understanding is :
E88CC which is USA 6922 is an industrial tube that is not so good for audio and if used becomes rapidly microphonic with a not so good treble but for ones liking brigth...as always maybe some exceptions.
EC88 is another story and even if less long life than the previous, generations of tubes enthusiast selected the best ones which sounded better.
Mine is a special iteration long life, low noise 7803.
For the use I will need with a dac chip having its digital silence at - 2mA and a ptop output at 0 to - 4 mA it is one of the good choice. The ECC83 is note in this particular conf.
My basic understanding is :
E88CC which is USA 6922 is an industrial tube that is not so good for audio and if used becomes rapidly microphonic with a not so good treble but for ones liking brigth...as always maybe some exceptions.
EC88 is another story and even if less long life than the previous, generations of tubes enthusiast selected the best ones which sounded better.
Mine is a special iteration long life, low noise 7803.
For the use I will need with a dac chip having its digital silence at - 2mA and a ptop output at 0 to - 4 mA it is one of the good choice. The ECC83 is note in this particular conf.
Nothing precludes a VHF tube being used for audio if the specs are good. You must have really gotten upset with all those HAM radio people using sweep tubes for RF amplifiers and not driving a CRT.
That said I've seen way more tubes with weak emissions than I ever have with burned out heaters. Inrush really isn't a problem.
I would like to follow up on the OP’s original question, if that is permitted. If not I swill start a new thread. Would Mark Johnson’s soft start be useful on an EL84 Baby Huey? In addition the soft start, I like the idea of having a low volt on/off switch.
Here is the link to Mark’s low voltage switch/soft start thread. https://www.diyaudio.com/community/...ains-relay-includes-soft-start-h9kpxg.354971/
Thanks
Thanks
I use one of Mark's soft start boards with my tube amp. With a SS rectifier I was getting a voltage spike at turn on of slightly over 500V until the driver tubes started conducting. This was concerning since the caps I have are 500V rated and I was worried about their longevity being slightly over voltage spec at each startup. With a change in resistor value I get about a 15sec delay before the soft start circuit is bypassed and now I never see over 460V on startup. So for me it was not about tube longevity but more the capacitors. The low voltage switch option is a nice bonus.
You can have your V-12 Lamborghini sports car modified to have a removable Hand-Crank.
Protect it by using the following procedure:
Turn the Hand-Crank 50 Revolutions, Slowly (Check with your Doctor first before you Crank).
Remove the Hand-Crank.
Be sure to check that the Oil-Pump is getting the Oil up and over the top to all the moving and rotating parts.
If the oil is not distributed everywhere, re-install the Hand-Crank and turn it another 50 Revolutions, Slowly.
Check that the Oil is everywhere.
Remove the Hand-Crank.
Now, you can start the engine without any fear of Start-Up-Wear on the parts.
I do not have a Lamborghini, but I do have lots of vacuum tube amplifiers that have run for 1,000s and 1,000s of hours, without any problem.
Just my opinions.
Protect it by using the following procedure:
Turn the Hand-Crank 50 Revolutions, Slowly (Check with your Doctor first before you Crank).
Remove the Hand-Crank.
Be sure to check that the Oil-Pump is getting the Oil up and over the top to all the moving and rotating parts.
If the oil is not distributed everywhere, re-install the Hand-Crank and turn it another 50 Revolutions, Slowly.
Check that the Oil is everywhere.
Remove the Hand-Crank.
Now, you can start the engine without any fear of Start-Up-Wear on the parts.
I do not have a Lamborghini, but I do have lots of vacuum tube amplifiers that have run for 1,000s and 1,000s of hours, without any problem.
Just my opinions.
lol. I guess my question was a little vague. I wasn’t thinking of tube life so much as trying to find out if there would be any problem using the low voltage on/off switch with soft start board on a tube power amp. I gather that it would be fine; although, your analogy implies that there might be some degradation in function (if not in sound quality). I definitely would like to have the low voltage switch; the soft start I could bypass if it would pose a problem. Spiggs seems to use it without problem. I am thinking it may be marginally helpful, in which case I will probably use it.
There is several advantages with the suggested solution.
There is a reliable low voltage switch , no more arced power switched
There is a possibility to concentrate all mains voltages far away from signal carrying components
Safety might be enhances as there is no mains cabling across the amp
reliability increases with switching mains with a SSR relay
There will be possibly a way to remote control power up/down from your control amp.
The start current limiting is a bonus and won't affect the amps function as it is bypassed within a few seconds.
Go for it !