New A12 Mod | SkunkieDesigns

Last week I took possession of a brand new Reisong A12 with the express goal of performing Skunkie's mods on it. I have never owned a Tube amplifier in my life and my primary amps for the longest time have been different pioneer amps from the 70s 80s and 90s and I haven't done any tinkering like this since Jr. High where I took a class where we had to solder (that was 30 something years ago!)

My initial impression of the A12 out the box was that of impressed. Given Skunkie's initial impression on her video series I did not expect much at all but what I did hear was everything I thought I was supposed to hear from Tubes and more. I think having come from solid state the sound of any distortion coming from a tube amp is something akin to romantic, and since this amp spec'd a lot of distortion I was actually impressed by that sound, maybe?

Anyway, I completed the mods 2 days ago and put in a Sovtek rectifier tube. Yesterday I installed the Gold Lion's (regular) and burned in matched JJ EL34s. Doing the mods with Skunkie's videos was a lot more straight ahead of a task than I anticipated. It now sounds spectacular! Now I will say that much of the distortion I was hearing is gone brining this closer sounding to solid state and it sounds, well how to I explain, less romantic. LOL. However, now the bass is a lot tighter and it presents the music much more accurately than it did without the mods. I'm supper impressed by the mids and the highs. The details I hear in drums is spectacular to my ears and the harmonics are dazzling without being obtrusive. Attack and decay are much more pronounced. I think what was happening pre mod is a lot of the tubbiness was obtrusive and it got in the way of the music. Pre mod, there was a lot of "wow I've never heard this like this before!" and now it's more like, "wow this sound's amazing, this is the way this music is supposed to sound." I feel like I'm a lot closer to the music now. I think a lot of the positive reviews out the box are from people like me who don't know what a good tube amp actually sounds like.

Another initial impression I had post mod is that there is virtually no noise floor on the amp. When I plugged everything in and turned it on I thought for sure that I messed it up because even with the volume up more than halfway I heard nothing from the speakers. As a matter of fact as I write this, sitting 3 feet away from the speakers, ready to rock, everything on, it's dead silent. I'm not running any expensive cables or anything fancy but I do use a Mid Atlantic Products power supply with EMF filtering.

I'm running a pair of EPI 100s on these. Sensitivity ratings for this speaker have never been published but general consensus seems to be that they are around 86 db. I had no problem driving them before or after the mods and they sound better than they've ever performed before. Simply put, tubes are doing things with these speakers that I never knew they could do, especially when it comes to imaging and depth. I have some sensitive Sony SSCS5 speakers here that I will try soon but I'm in no hurry.

Thank you Skunkie designs for your videos! You've brought me a lot of joy and this is anther success story and testament to your fine work and contribution to the community.

5 Comments

Junkman George

Mar 26

If you are looking for a more tube sound play with the value of the feedback resistor.

I'm currently running a 550k resistor in there instead of the 820k one.

Some here claim the sweet spot to be around 625k, I had an old 470k and a 75k left over after my build, hooked them in series, and there I was.

I understand the minimum to be around 350k.

Pre-mod, the tubbiness came from the over exciting the 2nd grid in the EL34 tube through the centre tap on the output transformer (this is where you removed a 100 ohm resistor and replaced it with a 2k ohm one).

Mar 28

Replying to

To further elaborate. The 550k resistance is a bit "boomy" for some types of music, so maybe you are better off with the 625k in there, to each his/her own.

Mar 30

And something is to be gained by playing with output tube types.

EL34, 6CA7, KT77, they all interchange, and all sound a bit different.

Again, this is a personal preference choice, I prefer the sound of the 6CA7.

Skunkie

Mar 31

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And that value can be played with. Many of those types of amps I use a 1.2K on the UL connection, just shoot for a screen voltage always at least a couple of volts under the plate has been my experience.

mddawson

Apr 27, 2023

I know what you mean when you say the modified sound is "less romantic". I recently got a pair of NOS AWA 6NS7 tubes to replace some NOS Sovtek tubes in my R8. The top end has so much more detail now and sounds more like a solid state amp and "less romantic" than it use to.