r/tubeamps

Hi everyone!
I wanted to share my latest flagship project: Euphony, designed and hand-built under my brand Vitro Cantus.
As a process engineer and lifelong tube audio enthusiast, my vision for Euphony was to combine rigorous circuit topology with modern ergonomics—without compromising signal purity or build quality.
🛠️ Key Highlights & Technical Architecture
Power & Signal Tubes: Features a matched quad of Psvane KT88 power tubes paired with high-grade driver/preamp tubes for dynamic headroom, low distortion, and effortless drive.
Remote-Controlled Ergonomics: Full remote functionality controlling the iconic ALPS RK27 motorized potentiometer for smooth volume tracking, input switching via relays, Mute, Standby, and Main Power ON/OFF.
Relay Input Switching & Short Signal Paths: Audio inputs (PrePhono, CD, Aux, Tape, Radio) are switched via local high-grade relays right at the rear panel to keep signal paths ultra-short and eliminate crosstalk.
Integrated Bias Control: Features front-panel Bias selection with a top-mounted analog meter for quick, precise calibration without needing an external multimeter.
Modular Internal Layout: Engineered with separate PCB modules for power supply, control/relays, and audio circuits—optimizing grounding, thermal dissipation, and eliminating noise.
Custom Acoustic Shielding & Aesthetics: A distinct multi-layered, laser-cut acrylic top frame designed to protect the tubes while creating a unique illumination effect alongside the backlit control knobs.
🎵 The Philosophy
With Vitro Cantus, I treat every project as a bridge between pure audio engineering and functional art. Euphony was built to offer absolute clarity, rich micro-dynamics, and a dead-silent background noise floor, combined with the convenience of full modern control.
I'd love to hear your thoughts, answer any questions about the internal design or component choices, and connect with fellow DIYers and audiophiles!

i didn’t get a crazy good deal or anything, but holy shit these XXXs are slept-on. i bought it off of a friend who was selling off some of his old backline gear and i’m not at all disappointed. i wasn’t sure it was for me at first when i tried it through my V30 cab with the damping on the tight setting— it was a little quacky, but i put it in the mid position and there i think it’ll likely stay. been mainly living on the “Crunch” channel, if you can really even call it that. not sure what preamp tubes are loaded in it, but it has a quad of Mesa 6L6GCs in the power section and it roars, plugged straight in! sounds especially ballsy through my 412MS with Sheffield 1290s.

It has a preamp, power amp, and reverb. The two 35w stereo channels can be rerouted to 70w mono. It's around 30 years old.

Hello everyone!

I’m having issues with my Ampeg V4 (VT-22), so I'm hoping to get some insight from people with more expertise. I’ve done everything I can think of and exhausted every resource I could find to identify the issue to no avail. I have a limited understanding, so I haven’t been able to narrow things down in a reliable way with troubleshooting.

When I turn the amp on and plug my guitar in, I’m getting no signal until the volume is turned up to around 10 o’clock. It’s distorted with limited sustain (it should produce a clean sound), then drops out completely until I strum again. It’s the same for both inputs, and the ext. amp jack on the back. 

The power light is slightly dimmer than the standby light. It was flickering slightly when I initially started working on it, but that has stopped and I’m not sure why. It’s still a bit dim, but solid.

Any advice would be greatly appreciated! Please let me know if any clarification is needed, or if there’s more troubleshooting I can do. I’ve listed everything below. 

Tubes:

• 4 x 7027A
• 12AU7
• 12AX7
• 12DW7
• 6CG7 (Missing)
• 12AX7
• 12AX7
• 6K11

All but the 6CG7 and 6K11 have been replaced with brand new JJ tubes. From what I understand, the amp should be working without the 6CG7 tube (reverb), but I’m not certain of this. 

Troubleshooting (Tubes):

• Swapped all of the pre-amp tubes with other working tubes
• To test the power amp tubes, I removed 1 and 4 position 7027A tubes, matched impedance and tested amp, then did the same for 2 and 3 position 7027A tubes. 
• Fuse has been replaced and I’ve tested multiple (6A/250V)
• I’ve tapped the tubes with a pencil to see if they are microphonic, but none seem to be. I’m not sure how hard I should be tapping them, so I may need to revisit this.

 

Troubleshooting (Other):

• DeoxIT cleaning of input jacks, ext. amp jacks, speaker jacks, fuse cap. Using a patch cable, inserting and removing around 20 times, twisting in between. As well as a q-tip, which came out quite dirty but I still see some oxidization on the jack tip and everything else. I will try using something abrasive if this could solve the problem. 
• I’ve replaced the three prong power cable end, but not the entire cable. It is a bit loose at the base where it connects to the amp, but the power isn’t cutting out, only the guitar signal.
• I ran my guitar through the ext. amp jack with the same result as the front input jacks. Although, I found I could get the same distorted guitar signal at a much lower volume, with the knob around 7 o'clock. 
• Obvious troubleshooting, such as cables and guitars have been tested. I’ve tried a different speaker cabinet as well as a different amp and it worked fine.

 

Thanks again for any advice!

'68 Sunn Secptre after extensive repair. Had for years but too many incompetent guitar store repairmen had been in it. Finally took to a certified, knowledgeable tech and did tube and component replacements. Sounds great through a Jensen C12N and EVM 12L. Happy to resurrect after a long period of being dead.

Hey, I have a problem with my fender custom pro reverb. It started to make this horrible noise when guitar is jacked in. But only if the amp stands flat on the ground. When I turn it like 30-45 the noise stops. Apart form the noise it plays normally. I thought it’s something with the speaker, but I connected different speaker and it was the same or even worse. Any idea what happened?

Is this normal for these amps? This is my first tubeamp and this noise is killing me. I thought faulty preamp tubes caused this noise, because 3 out of 4 were leaking. Then i threw new preamp tubes in and the noise is still present. i have tung-sol 12Ax7 in v1 and rest of them are jj ecc83 tubes. i have nothing in the fx loop and speaker cable is fairly new orange.

Doesnt matter if guitar plug is in or out.

Oh and this is pre infinium if it matters.

ps. English isnt my first language, sorry about that.

Only happens while playing, doesn’t while the amp just idles.

Fender Deluxe Reverb from 1995.

Was thinking probably the tubes but don’t really have any faith in my own troubleshooting. Any help or pointers would mean the world, Cheers!

Hi all,

Looking to build myself another lid for my late-model Ampeg 115 portaflex cab (right now it’s situated with a ‘67 SB-12 that I don’t want to keep removing).

Only issue I’m having is trying to source a catch plate like the one pictured - need 8 of them (4 for each side). Any ideas? This is a relatively new cab, and Ampeg doesn’t appear to sell components like these individually. Thanks in advance!

Hey guys! First post here so I’m sorry if I’m out of format.

Recently, I was rummaging through my gear collection looking for some extra stuff to put up for sale and found that I had a 4-pack of Amplifier Tubes laying around.

I had taken a newly acquired Fender Twin Reverb (1972-1976) in for servicing about 2 years ago (the previous owner had added a wattage modifier switch that caused instability in the circuit, but no issues with the tubes). It took a while to hear back from the amp tech, but he eventually reached out and said he had not only repaired the circuit, but replaced the tubes because he didn’t believe the quad had ever been taken out. He sent them back in a wrapping for me to take a look at.

I believe they are a set of 4 black-plate matched 6L6GC tubes serial numbered 7439. Though, I could be wrong. There’s barely any information online that I understand. There appears to be more writing on the glass of the tubes that has faded from time.

I’m not sure what sort of quality I’ve stumbled across here, but any tips or advice on what I’ve got would be much appreciated. I am NOT looking to sell and this is not a post trying to advertise.