"Color" Tube Pre-amp for Solid State Amps: Power Supply #2

[@johnkohlhauff9061]

Love your videos. I especially appreciate the way you explain why and how come you are doing things a certain way. Your videos aren't hard to follow. Thank you for making videos people can understand!!

[@cobar5342]

Great video Stephe. I could watch you work all day

[@zefrog7482]

Your channel has gotten me wanting to build all of this stuff, would never have thought a few weeks ago I'd even consider DIY, but you explain it all and demonstrate it so well its a job to have a reason not to.🙂

[@richardr3178]

I gotta get to building this little dude!

[@SkunkieDesignsElectronics]

Do it! Enough people have built this and like it, I consider this a proven design.

[@johnjackson7162]

Great construction tips. Thanks a lot.

[@thuanle-lo5bi]

good

[@robertdiffin9136]

Looking forward to trying this unit with my Crown ice power amp that sounded way too sterile with my Magnapan 1.7s.

[@WayneKnight_Rider]

technically, combining the resistances does change the smoothing characteristics of the filters. The LC filter is going to provide -34 dB ripple attenuation regardless of the Rd position. There is approximately a 5 dB difference in ripple attenuation in the RC filter when combining Rd with the RC filter. Not a big deal in this circuit. I believe Matt is placing Rd in the circuit to allow the builder to tweak the final B+ voltage. If the B+ is too high, swap in a higher Rd and vice versa. Also, the placement or arrangement of individual resistances following rectification will not affect current.

[@bob_mosavo]

Thanks 😁

[@tebbi67]

Now i must see how it ends with the preamp........i prefer the old discrete mosfet amps for the chain....because the amplification of the mosfets have also a listening character, The overall amplification is added as well as the sound character.....thx for the vid.

[@SkunkieDesignsElectronics]

I've been thinking about playing with those in the future.

[@bob_mosavo]

Bob Cordell says that MOSFETs are his favorite for audio amplifiers.

[@1mctous]

2nd-order harmonic distortion done dirt cheap, especially compared to an SE power amp!

[@SkunkieDesignsElectronics]

Bingo!

[@gee3883]

Hi Stephe. You mention at the end that this is suited to cheaper solid state amps. If you have time can you please tell me if this is suitable to hook up to an ice power ICEpower 1200AS2 specs > Output Power per channel 1 % THD+N, 20 Hz - 20 kHz 1200 W (4 Ω) 600 W (8 Ω) Output Power per channel 10 % THD+N, 20 Hz - 20 kHz 1400 W (4 Ω) Minimum load impedance 2.7 Ω Maximum amplifier efficiency - Maximum total amp+psu efficiency 80 % Supply voltage input 85-264 VAC Peak output current 38 A Dynamic range 129 dB Amplifier maximum output peak voltage per channel 100 V Output referenced idle noise (A-weighted) 25 µV THD+N 1W/1kHz 0.005 % Sorry if this is a dumb question, best wishes from sunny London.

[@SkunkieDesignsElectronics]

You didn't specify the input impedance, which is the main one that would matter.

[@asx1248]

I’ve really enjoyed this series, watched the videos a few times and subscribed. Can you explain please why the star ground goes to the transformer centre taps rather than the point where the ground/earth of the incoming mains power is attached? Since both these are connected via the chassis why are they these two ground points not directly linked? Thanks, Alex

[@SkunkieDesignsElectronics]

1st is for safety, I always want to ensure the safety ground has a solid connection. 2nd is for some reason, I have had less problems with hum when they aren't tied to the same point on the chassis. *shrugs*

[@asx1248]

@@SkunkieDesignsElectronics Thank you for the reply. That’s very interesting because electrically they are still connected via the chassis. I’ve always been tempted to make a valve amplifier but considered the task a step too far for a beginner but this series of videos has really given me the confidence to try. No timescales on when, but I think it will definitely be my first project. Thanks again for sharing your knowledge with others.

[@SkunkieDesignsElectronics]

Grounding stuff in tube amps can be pretty weird :)

[@ericlane5949]

The Hostiles would probably be AOK with the design if it had been called a ‘tube buffer preamp.’

[@bob_mosavo]

A buffer is not supposed to alter a signal, right?

[@SkunkieDesignsElectronics]

Why do they think it's called a "Color" pre-amp lol

[@bob_mosavo]

@@SkunkieDesignsElectronics Yup! I was trying to get Eric Lane to realize that this is not a buffer 😉

[@johnstuchlik5828]

Haven't seen the schematic, I wonder if putting the 2k of drop resistor between rect tube and 1st cap and some between 1st and 2nd improves the voltage regulation on transients.i realize this supply is class a preamp has small change in current.what value is the 1stcap? you've got me curious to experiment.have seen where drop resistor to reduce b+ was suggested to put between rect. And 1st cap on small set power amp.your video s have benefit me on how to do the circuit grounding . bridge gap between schematic and actual lay out and construction.some small tube rect can't take much than 10mfd. On 1stcap without considering surge charge current .I damaged a 6x4 that way.

[@SkunkieDesignsElectronics]

But he placed the resistor in between the first cap and the choke... That's not the same as between the rect and the first cap. And you are right, a 6X4 can only handle 10uf (and are know to be very weak anyway...), this tube is rated at 50uf. It's a much stouter tube and as you said with class A, there is almost zero change in current to consider. Also moving the resistance inline with the choke to where I did seems to make that RC stage of filtering more efficient as it sims lower ripple. The schematic is at the web link.

[@johnstuchlik5828]

​@@SkunkieDesignsElectronics thanks for the clarification.i looked at the schematic and I think I understand why he did what he did.i also now understand why you made the change.2k feeding that cap for preamp seems ok and you may gain some ripple reduction.6ca4 should last a long time in this circuit.

[@pavelpavlov954]

By the way since it doesn't have big consumption, do you think his power supply will be able to feed four pairs of "color" preamp in one box or it will be too much?Thanks.

[@SkunkieDesignsElectronics]

I would have to do th3e math on that one, but possibly. I have learned leaning hard on a transformer/power supply can end up creating noise. It's important on a higher gain pre-amp to have the power supply somewhat "coasting".

[@jonzeuthen-tv2wn]

Just a newbie question from me, is the 2k resistor a 1 or 2 watts? 😊

[@SkunkieDesignsElectronics]

If it's the one in the power supply, 2W for sure. I just realized I never uploaded all this info to the web site!