All now placed in 'My List' Digikey. Cheers.
What is the purpose of those HER108 diodes?
The diodes protect the rectifier tube. According to George, modern GZ34s can't take the punishment that the old Mullards and Amperexes could. He did say that the diodes weren't really necessary for the SPP. An old Dynaco ST70 would be a different matter.
S.
S.
As George mentioned, if C101 is actually needed, then to have a range from say 270pF to 800pF.
I would imagine something like these would be fine, voltage rated 100V - 300V?
https://www.digikey.es/en/products/...Uofgb1fvIg5nF1mB2BABMuDeiINk45q3YAT1YWufqUM6A
To determine the optimum value of C101, using 'Silver Mica' is an expensive affair.
I would start with different MLCCs (C0G/NP0) and then replace the correct value with a 'Silver Mica'.
As already mentioned several times, the amplifier will also work without this capacitor.
Attached is an example of a 1 kHz square wave signal.
In the picture above everything is OK. A missing or incorrect capacitor was used in the bottom one.
I would start with different MLCCs (C0G/NP0) and then replace the correct value with a 'Silver Mica'.
As already mentioned several times, the amplifier will also work without this capacitor.
Attached is an example of a 1 kHz square wave signal.
In the picture above everything is OK. A missing or incorrect capacitor was used in the bottom one.
Cheers for that, though i dont have an audio generator, so it'll be ears tuned and go from there. George from Tubelabs said it might not even be needed.
As you say, Silver Mica's aren't cheap...
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I'd recommend getting a relatively cheap USB sound card + REW (free) software, results in an excellent audio generator and low voltage oscilloscope that you can use to tune your amplifier.
Thanks. I'll be asking for a favour by the looks of it from an 'audio' guy i know.
I'm sure there'll be something on YouTube
Can someone enlighten me about using a Vol. control at the inputs?
I assume it should be Linear.
I know that Stephe https://www.youtube.com/c/SkunkieDesignsElectronics mentioned in post #39 that she would be using a 100K pot.
Saying that for R100 she would use a 1M 1W metal film and R101 a 1K 1W metal film, that the "higher power resistors sound - slightly- better/less noisy".
Any recommendations for the type of Vol. Pot to use?
I assume it should be Linear.
I know that Stephe https://www.youtube.com/c/SkunkieDesignsElectronics mentioned in post #39 that she would be using a 100K pot.
Saying that for R100 she would use a 1M 1W metal film and R101 a 1K 1W metal film, that the "higher power resistors sound - slightly- better/less noisy".
Any recommendations for the type of Vol. Pot to use?
Just my opinion Calpe.
You can't build your amp optimally on the first try.
buy yourself a selection of cheap components but in several values and do some tests.
Instead of taking only 1 silver mica of say 330pF, you take a range of 100pF to 1uF ceramic (or other) to do your tests and when you have determined the right value, you buy the right mica.
ditto for your potentiometer, take a range of 20K 50k 100k 250k 500k and 1M as standard and try it, it will always serve you for something else.
You can't build your amp optimally on the first try.
buy yourself a selection of cheap components but in several values and do some tests.
Instead of taking only 1 silver mica of say 330pF, you take a range of 100pF to 1uF ceramic (or other) to do your tests and when you have determined the right value, you buy the right mica.
ditto for your potentiometer, take a range of 20K 50k 100k 250k 500k and 1M as standard and try it, it will always serve you for something else.
Volume control pots are usually logarithmic, matching human ear's response. Alps pots are decent, and not too pricey.
I must admit and its probably obvious by now that i am not a DIY person.
When i spot something of interest i have a few thoughts and if the urge gets to me, i'm up on my feet.
Yes, i take time in ordering parts as i want to avoid numerous postage costs and when of course import duty too.
So it boils down to try and get my parts list order as accurate as possible, so i really do not want to be left with items i'll never use, but thanks.
I look at George's Tubelab's SPP write up (although hacked and some text appears to be doubled up and not correct), read it to see if he suggests any changes etc.
The same for Stephe's Skunkie Design Electronics, she is so natural and hands on lady, and certainly knows her electronics, puts me to shame.
Not forgetting the very useful write up here https://wallofsound.ca/misc/diy/diy-el84-amp-project-part-2-circuit-board-and-chassis-preparation/
However, there is light at the end of the tunnel, spares part list is now 95% ready, just need to sort out my nothing special case.
The Transformers and Choke should arrive within a couple of days
Valves (tubes) and valve sockets have arrived, need to collect from Post Office on Monday,
@calpe,
I’m sure you will do well with the Tubelabs SPP and will have reason to be proud of your build once it is up and running. You may not have DIY experience, but you seem to be intelligent, careful and deliberate in your approach I believe you will be successful and well pleased.
I am currently building an amp to explore using Russian 6P15P power tubes (in stead of the EL84s) in the Tubeslabs SPP PCB. I plan to install
”posts” (just a short solid copper wire sticking straight up with a hook at the top) in place of the feedback capacitor, so that I can try different caps easily. I am eyeing one of these for an attenuator:
https://www.ebay.com/itm/2748637127...Sa8BgLrRxy&var=&widget_ver=artemis&media=COPY
I’m sure you will do well with the Tubelabs SPP and will have reason to be proud of your build once it is up and running. You may not have DIY experience, but you seem to be intelligent, careful and deliberate in your approach I believe you will be successful and well pleased.
I am currently building an amp to explore using Russian 6P15P power tubes (in stead of the EL84s) in the Tubeslabs SPP PCB. I plan to install
”posts” (just a short solid copper wire sticking straight up with a hook at the top) in place of the feedback capacitor, so that I can try different caps easily. I am eyeing one of these for an attenuator:
https://www.ebay.com/itm/2748637127...Sa8BgLrRxy&var=&widget_ver=artemis&media=COPY
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Calpe,
I've used the remote volume much like these before and they worked OK, The only problem is finding 9 to 12 volts in a SPP build. The filaments are only 6 volts. Unless you are really set on remote, just get a 50K or 100K Alps Blue Velvet pot (same as in the picture in your link but no motor, board or any of the other bits) https://www.ebay.com/itm/272249742734?hash=item3f6359658e:g:vXMAAOSwU1FXP-Fb.
I've used the remote volume much like these before and they worked OK, The only problem is finding 9 to 12 volts in a SPP build. The filaments are only 6 volts. Unless you are really set on remote, just get a 50K or 100K Alps Blue Velvet pot (same as in the picture in your link but no motor, board or any of the other bits) https://www.ebay.com/itm/272249742734?hash=item3f6359658e:g:vXMAAOSwU1FXP-Fb.
I needed 5VDC for the Khozmo attenuators w/remote and used a small SIMPS tucked into a corner of the preamp chassis. Works well but takes up a little space.
Thank you for the interest shown and your words, but i will not be using Motor Potentiometer Remote Control Volume in this build.