Good day L & G,
I was looking for suitable candidate for my bench amp and I found schematic of Roland Jazz Chorus JC-20 from this japanese website :

Looks like this is the one and only JC-20 schematic on the interweb. Anyway, from his article, I got impression that the guy who trace it are surprised that this kind of circuit are released into final products, so probably there's something weird into this circuit.

I did my research based on several another article & gutshot pictures of the...

All this would never have happened if Lee Anderton would have kept his face off the telly... He's born rich, so he's always been out for fame. But this does leave the company very vulnerable.

If you put the title of this thread together with the title of below video you know what's going on: Anderton is (co-)owner of Victory amps and consistently tried to hide it, while they didn't hide launching a number of other brands (they own Burns now btw). Meanwhile, on their youtube channel, to go...

Hello,
i am looking for the schematics for troubleshoot.

Hello everyone, everything good? Does anyone have a PDF of the original Marshalll 1959 SLP PCB with values ​​and board design?
measurements too
I'm finishing drawing and I would like to have this PCB. grateful

ps: I will post here update.

Hi, i have this headphone amp for a while and it was working fine until i plugged jfet boost into it. From that time it distorts signal in very bad way when i have bass on max, when i turn down volume it gets better but it lacks volume for headphones, i tried to change batteries but it didnt help. Any schematic or idea what could cause that problem?

Hello people.

I am trying to fix a Fender practice am with a loud hum noise.
the amp works but it has a hum noise (50hz) loud even when the guitar is unplugged.

- Volume, Contour, Reverb doesn't affect the noise.

I had attached the schematic for the amp Fender R.A.D. that is the same without the reverb circuit.

I tried to connect the preamp output to another amp and the noise still there. My first thought the issue is in the power supply I changed all the electrolytic capacitors in the...

Hallo everyone,
I started my amp builder career with ROG Ruby, then Noisy Cricket, then Tube Cricket, then I moved to higher voltage amp IC: TDA 20x0.

I've built a bridge dual supply TDA2050 AMP. Until I supplied with 36V and voltage divider (low current, ±18V) it worked as expected and louder.

tda2030-bridge-amplifier.jpg

Then I moved to transformer ±18V and 6 elna 10mF filter caps and... probably I cooked my ICs.

20230206_171832.jpg

A bit disappointed, I bought 2 modules from...

Just got these from an eBay auction the other day, thought it was pretty funny. They're definitely Russian 6p6s tubes. Would've been a cool light show if I put them in my bass amp and biased like a 6l6gc. The one on the right is the same thing, but labeled realistic brand 6v6.

The schematic for the other bass preamp by Alembic, the F2b, can be found quite easily on the net, but I hadn't earlier seen the schematic for the F1x.
The product blurb mentioned something that to me pointed to integrated filter IC's like the UAF42 (although that is reported to sound not great ), but apparently not :)

Alembic F1x schematic.png

I am trying to convert a Europe-spec 90's Fender Sidekick 15 reverb amp (sorry, not a tube amp) to run on North American power. Looking at the power section of the schematic (see attached), it seems to me that all I need is a new power transformer capable of delivering 21V center tap like this one . Does that sound right?
If that helps, the part list for the sidekick series list the following part numbers, which I was not able to decrypt: Transformer, Power, F2158UC, F-168UC, F-1008UC, SK-25,...

Hello

This is a nice and rare rack mount tube preamp from the early 90's from Jackson. I have traced the power supply and created a schematic. Its just a simple linear supply.
I was thinking about reverse engineering the whole thing. Leave a comment if you want me to trace the entire thing. If I get enough interest Ill do it.

I posted a YouTube video about it on my channel:

JacksonJX3_PowerSupply.jpg

Peace out.
Pete

I'm feeling reassured that the Ammo Can load wasn't responsible for my amp blowing a tube. I stuck another set in there (EL34s this time), rebiased, checked all voltages, etc... Biased at 70% dissipation, I ran a sine wave directly into the phase inverter and got a very nice clean symmetrical since output without any obvious distortions. When pushed up to clipping, it would show a wave typical of the PI clipping out, so I will say on the bench running a clean sine thru the amp is no issue.

I...

So I picked up 7 of these on the Bay for a great price thinking they would be good in tube amp projects. I measured all the resistances for them (see below image) and I'm pretty confident I know what wires are the primary and what are the secondary. The primary is a little strange and worries me because you would think the resistances would be the same on both halves which they aren't. Is there a conventional color coding scheme with the wires? I know black & white for the primary is Line &...

Blue stripe peavey bandit 112...it's a weird amp with weird controls for sure but the issue is on the clean channel, using the left most pot as volume,it can't be turned up last 1. Doing so increased the volume to 1million percent. Insanely loud and unusable. After cleaning all pots and jacks with contact spray, the problem persists and is now present on the distortion channel. Prior to cleaning the post gain on the distortion channel could be turned all the way up and not be super loud now...

Speaker Line Out Isolation Transformer question:

Does anybody know what Type/Spec ‘Isolation Transformer’ Suhr or Bradshaw uses for their Speaker Line Out Boxes? Correct resistances?

Want to attempt to make one.

I see these resistance specs options but don’t know what is needed:
— 600:600
— 10k:10k
— 10k:600 ?

— Xicon, Jenson, Edcor ?

Anybody have any ideas or knowledge on this?

Thanks for any help

Hi guys.

I am a fan of Blackster FLY3.

It is a 3W amp but its too loud for the apartment I live in.

Specifically, I can only turn the volume knob turn to about 1. Its hard to adjust and its stressful for me :(

If I could turn down the max volume I could turn the volume knob as freely as I do when playing in the studio.

What modifications should I make?

In case you are wondering, I have enough skills to DIY pedals. If its not too hard to mod it, I will do it right away.

Please give me...

I'm trying to build a practice amp using an 8 Ohm speaker and a TDA 2822 IC that will run on 9v pedal power.

For a first attempt, I built the bridged example from the datasheet, shown here:

tda2822-bridged.png

It works, and it's a bit more volume than the usual LM386 amps I've built (ruby, noisy cricket, etc), but zooks its dirty. Like fuzz dirty. If I crank WAY back on the input volume it cleans up OK, but I'm just wondering if I can do anything to make that sample circuit play nicer...

Hello everyone!
Your requests have been heard! I've added three brand new PCBs to my products list 🙂

SLO-style PCB (400mm x 78mm)
Princeton Reverb PCB (322mm x 63.5mm)
Dumblelator PCB (240mm x 35.5mm)

All boards come with full documentation: layout, schematic, BOM! If you want to check out the documentation without any purchase, I've made it available for FREE on my website for anyone to download (just login and you can view/download everything):
If you have any question, please let me...

I want to build or purchase an affordable EL34 power amp, either 2x rack unit or small head format. Absolute maximum 50W, ideal 10-20W, as it is just for playing and eventually recording at home. Only power amp & phase inverter, no preamp, as i have a gazillion preamps either made or in the making for it, and a valve head already.

Any recommendations on DIY kits or ready-made products that have a good quality-price ratio?

Thanks in advance!