"Color" Tube Pre-amp for Solid State Amps: Design Tweaks

This video describes how to tailor this design for your specific system, and explains how and why this Pre-amp differs from some other tube pre-amps out there.
I think this design really hits the mark on what most folks are looking for from a vacuum tube pre-amplifier!
This series is about building a tube pre-amplifier for use with any "overly sterile" sounding solid state amplifier. This device introduces the warmth and second order harmonics people associate with tube gear, in a controllable and consistent manner. The builder can add multiple sources and other options, we are building a basic version to showcase what it can do. At the end of the series we will be doing a complete technical and subjective test of the unit.
Here is Matt's website explaining the design of this amp:
www.cascadetub...
Here he explains the placement of the volume control:
www.cascadetub...
Here is my Patreon, as well as the donation page at my site, if you feel so inclined to help fund some of the future projects for the channel!
www.patreon.co...
www.skunkiedes...

[@LeeBergerMediaProd]

I'm a professional audio tech and your input vs output gain explanation makes perfect sense to me. If you overdrive the input stage of any preamplifier (be it this preamp or let's say a microphone/line level preamp in a mixer) your output will be distorted no matter where you set the output gain. On the gear I use, I have the benefit of either input metering or a peak LED. By the way, I'm learning so much about tube amplification and tube circuits from your videos. Thanks so much!

[@zoroluva]

I swear this phone is watching what I do... I almost pulled the trigger on a Aiyima tube preamp board... Then KZbin started suggesting this channel...lol Thank you for this series!

[@NosEL34]

I've been very interested in this preamp series. I have a streamer only set up I've been putting together that is extremely transparent and I need some tubes injected into the mix. This Color pre would fit perfectly with what I have already.

[@mfr58]

Looking forward to hearing your experiences with how it sounds....

[@therideneverends1697]

Excellent video! I appreciate the succinct explanation of the technical aspects and visual examples. Definitely has given me some ideas

[@pilage98]

Excellent video. Thanks Skunkie Designs!

[@themeeksproject9785]

love this and the love that followers do it helped a lot to those aspiring to build thanks for the effort.

[@bob_mosavo]

Thanks 😁 I'm looking forward to what the tests show 👍

[@SkunkieDesignsElectronics]

A short listening test, I like what I hear but I need to test it on a SS amp.

[@RaviNewfarm]

Cool ideas for a preamp this. I especially liked the idea of volume control both on the input and the output, although a pot degrades the sound a tiny bit, so having two is not optimal in that sense. But would be fun to experiment with for sure. I have coming up both an firstwatt F5 and F4 and this style of pre would be perfect for playing with those. With 21 db of gain it should just be able to drive the F4 which is a power amp with no gain, so needs > 20 db gain from the pre, i.e all voltage gain must come from the pre.

[@NickP333]

Awesome! Very cool that you brought up and showed part of the schematic from the Mapletree Audio’s preamp. Did you already know about it before I sent you that info on your site? It looks like a really interesting way of building a preamp. I’m very curious as to how that’d sound too. A lot of different possible variations on a theme here. I’ve got a fully refurbished beautiful old Hitachi HA-610 SS integrated amp. I put a tube buffer I built using 6922’s in between the pre and amp to add a bit of tube sound. Thanks for another great vid. 🔊😊🎶

[@SkunkieDesignsElectronics]

I knew about placing the volume control between the stages, but thanks for sending me those links! Like I said, for DIY folks wanting to tinker around, lots you can do here!

[@NickP333]

@@SkunkieDesignsElectronics Yeah, I figured you knew about putting the volume in the middle, but just curious as to if you knew of Mapletree Audio? They’re pretty new to me, but I found it exciting when I saw they had schematics for all their products. Yeah, no doubt this preamp has a lot of options of how to build it. This is something I can see myself building to use with a SS amp. I think I’m gonna be building one of Nelson Pass’ First Watt solid state amp designs, and with this pre in front…? That gives me more of a reason to build them. Seems like a good combo. 🤷‍♂️😊🎶🔊👍 Thanks again, Stephe!

[@josephcorreia3116]

Great video! I have a FX audio tube - 01 preamp buffer that you are about to review. If I increase the signal from my dac to this preamp, will I get more tube distortion?

[@SkunkieDesignsElectronics]

Yes. Try driving the pre-amp tube with a hotter signal (or increasing the volume knob on it, the volume is on the input of this pre) and then attenuating it on the volume control on the amp (Which would be the same as doing this on the output of the pre) and vice versa.

[@josephcorreia3116]

I tried what you mentioned Stephe. Sounds different for sure. I increase the signal strength to the FX audio tube - 01 with Russian tubes by using the volume control on my DAC. Bass drums sound less defined but, fuller. For some music like rock, it sounds a little to distorted. Just have to turn down the volume signal from the DAC. With easy listening, and Sinatra sounds good. Noticed larger deeper soundstage.

[@jameskaihatu6209]

Thanks! I have a solid state amp I would like to make less sterile sounding. This is perfect.

[@BobCvideos]

Can’t wait to see testing results. The explanation on where to put pot vs impedance was awesome. I wonder, does a tube pre amp stage provide the same level of “color”?

[@SkunkieDesignsElectronics]

It depends on the amp but yeah, many do.

[@danbuffington75]

6:05 Could I do something like that to use a SET as a preamp, but still use it as a SET when I want to?

[@SkunkieDesignsElectronics]

I don't understand what you are saying.

[@GavinHodgson]

Great series of videos

[@pastamatt]

With these input gain adjusters, do you think they could be turned up enough to allow this preamp to take a phono input from my record player as well? I just ordered the transformers and a few other parts so I can build this thing... primarily to go between a Raspberry Pi with DAC HAT and my integrated SS amplifier... but it would be nice to be able to use it for vinyl too...

[@SkunkieDesignsElectronics]

A turntable needs a RIAA preamp / "phono stage" to de-encode the vinyl. Even if this has enough gain, it won't sound right.

[@pastamatt]

@@SkunkieDesignsElectronics OK, thanks! Good to know!

[@kestutisrimkevicius8891]

Has anyone compared this one to CJ PV12? Wonder if will be any difference in sound. Thinking about building this one ("Color") for myself.

[@MiniCNCLamphun]

Excellent video. 🙏Thanks 🙏

[@IgorPetruk1989]

Hi, thank you for your video. I am getting ready to build a 4S preamp. My Hammond transformer comes with a lot of unnecessary wires for other input voltages, etc. Do you have any tips on how to deal with them? Or maybe some of your older videos cover it?

[@SkunkieDesignsElectronics]

What I have been doing lately is: Take off the end bells, trim down the unused wires, seal the ends with heat shrink tubing, tape them together and tuck them neatly up against the core and reinstall the end bells. Then only the wires I need come inside the amp. That or you could seal them off inside the amp if you don't feel comfortable doing what I just described, that's what I've done in the past.

[@IgorPetruk1989]

@@SkunkieDesignsElectronics thank you, I will try that. Shrink tubing sounds like a good idea. I saw this on your videos that there is no trace of extra wires. I was assuming they are inside of the bells somehow, but I didn't know how because wire nuts are too big to fit

[@mattheweurich2842]

Loving your videos! I'm looking at doing this amp with a 6GU7 tube since I have a few of them laying around. It looks like the specs are close enough other than the obvious 12 to 6 v heater change. Any thoughts???

[@SkunkieDesignsElectronics]

Right, they should be very close to the same. Go for it!

[@brianwills5707]

The issue I've always had with tube pre-amps (Foreplay, Grounded Grid, and Akido) and solid state amps is that the amp's gain tends to be too high and I hear a lot more hiss than I'd like.

[@danbuffington75]

6:03 What is the value of the "fixed" resistor? I don't understand what you mean by fixed, because you also say to not use a low value, but let the amp dictate the value. I'm not clear.

[@danbuffington75]

You said 1 meg. Did I understand that right?

[@SkunkieDesignsElectronics]

If you are building an amp for this to drive, the grid leak resistor on the input tube sets the impedance, just don't use something lower that 250K unless you have no choice.

[@thuanle-lo5bi]

👌👌👌 Pure video, No Ads #PureTuber

[@el_arte]

A DAC with a volume knob acts as a preamp of sorts. So, this video acknowledges that feeding a 2V RCA signal to this preamp would inject a lot of distortion the potentiometer on the output could not take back. Which is what your diyAudio friends were saying.

[@SkunkieDesignsElectronics]

You are missing the point... We (at least some of us) want SOME of this distortion, that is the WHOLE point that some people just don't seem to understand. But also we don't want a lot or too much, which is why you don't want to just blast a full signal into this device. And I never said the pot on the output would "take it back", it actually preserves it. If you want zero distortion, this is not a device you would ever want to use. I would say at least 80% of those DIYaudio "friends" can't comprehend this, it seems simple to me.

[@el_arte]

@@SkunkieDesignsElectronics I am not missing the point. There is “some” and there is “5 to 10%”. Feed it the standard RCA 2V input signal and use the Audio Analyzer Suite to find out if it’s “some” or more than “some”. I like distortion too, particularly even harmonics distortion, but past 3-4%, it’s no longer a benefit to my ears.

[@SkunkieDesignsElectronics]

Until I measure it, all those DIYaudio guys are just guessing at % distortion. I've listened to it briefly and there is no way even with a 2RMS input is there anything close to those extreme amounts of distortion present. Did you read Matt's page? "As can be seen in the table, the preamp adds about 1% second harmonic color to the signal." www.cascadetubes.com/the-12au7-cathode-follower-color-preamp/

[@kubockferre5532]

hi you forgot another scenario if you have a cd player with a fixed output and you drive a transistor power amp with no volume control , you put a volume control input or output of the preamp!

[@SkunkieDesignsElectronics]

kzbin.info/www/bejne/qWOUZax7hJhgl7s

[@frankgeeraerts6243]

...................Putting back some flesh on the digital /solid state musical bones................ You could organise a loterie for the preamp.............and make someone a happy winner ....

[@SkunkieDesignsElectronics]

Unfortunately in the US a "contest giveaway" involves all sorts of legal silliness. :(

[@frankgeeraerts6243]

@@SkunkieDesignsElectronics OWWW , didn't know ! Have a nice day