albatros_1994

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Hi guys, new project here, my dream-amp.
Let's say i have the schematics and i'm using a Crate BV120-H as a base "corpse" (Cabinet, tubes and transformers), the rest is all new and "handmade".
I mean, not much to say about the amp, it's an almost 1:1 copy of the original Fortin/Randall Satan. The preamp and poweramp use the same resistors and caps.
The transformers are different, clearly. I'm not using a choke but it's not mandatory, i have extra HT+ caps to compensate.
The clean channel is all-tube on mine. The original uses 2 FET transistors
The entire project costed me probably around 700 Euros (200 for the Crate, around 500 for the rest)

Some specs:
5x Sovtek 12AX7
4x Sovtek 5881WXT
Crate BV120-H Transformers
F&T 500v HT caps
Low-Noise resistors
DC Heater for the first stage

I have some photos of the work in progress here:


At the moment i just have the OD channel working, all is there but i still have to wire the footswitch and the fxloop, i also need to tweak the voltage going to the stages, poweramp bias and remove some static noise.
I'll work on it a bit more in the next days, i still have a lot to tune, but the sound is 100% there.

Short video of the first test
 

lewis

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Hnnnnnngggg this thing sounds absolutely godtier!
The balls and upper clank appeal to me
 

albatros_1994

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I must admit that this amp is well designed and voiced, very difficult to make it sound bad.I love how the presence is implemented. The "Kill" switch is also very nice if more gain is needed.
Maybe a bit less saturated and gainy than what i usually go for in my amps, but it may just need some finetuning. The low end is amazing, the "grain/clipping" of the distorsion is absolutely perfect.
The video is very raw, just turned on the amp, biased and recorded. I really want to work on it more as soon as i can

BTW, i have 2x Modded Crate BV120-H on my Youtube Channel that sound very similar
 
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technomancer

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Sounds great, been meaning to do this for a while but other projects always come up.

Worth nothing the 100w has the all tube clean channel, the SS setup was something they did on the 50w to lower tube count / costs.
 

albatros_1994

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So... i worked on the amp for a while and tweaked the preamp voltages (i'm at around 345V on the first stage), removed a bypass cap on the phase-inverter to get a more natural/flat voicing, reduced the "Kill" switch gain to make it more usable and less fuzzy (2.7K resistor instead of 1K) and maxed the V2A stage gain by using a 470K plate resistor instead of 100K. It now sounds a bit more like the videos on youtube. Enough gain to chug without boost or "Kill" enabled. Very sharp attack and mids. I've put a "High-Gain Selected" Tung-Sol in V1 and a Sovtek 12AX7 LPS at the phase-inverter.

I didn't like the original grounding i did, just a messy (and noisy) job. So i decided to read some stuff about the subject and re-do the entire thing right, making it a solid core ground bus that runs along the entire amp

This amp is weird, a bit difficult to get it sound right as it's very sensible to EQ changes, the Presence pot has the opposite effect compared to a normal amp, it removes high-end at the phase-inverter ("Snubber Cap"), it's also important to set the Girth+Bass+Depth just right to fill the low-end and get a good kick, the Sweep pot helps a lot to tame the low-mids (it's a variable slope resistor in the tone stack).

i'll fiddle with the OD channel a bit more to see if i can find something else to tweak but it seems fine now compared to "stock". I'll deal with the clean channel after that is done




Sorry for the low quality video/audio. I record with just a phone, but the room sound is pretty realistic i must say.
 
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albatros_1994

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Boys...All done, cabinet, footswitch, clean channel and FX-Loop.
I went crazy for a week trying to understand why the gain was so low(i needed to max it out all the time). Well well it was just a resistor messing with the signal level between V3 and V4, i went from a 150K resistor to a 250K, god-tier gain levels now. I almost never need to push it over 6 or 7 😁

As usual, a video, the phone is really compressing the audio when there is a lot of low-end but wel well, you get how it sounds.
 

albatros_1994

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That sounds great. I'm always in admiration with the work I'm unable to do myself.
Thanks, I really don't know if what i'm doing is "hard", it's NOT rocket science for sure, it's mostly tubes, resistors and caps connected in such a way that they amplify and filter the signal, multiple times, not tecnically difficult, you just need to know how to set it up right to get a nice sound out of it. What i find difficult is to build with quality, clean and in order. I'm getting better but i'm surely not great at it
 

LedAstray

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Sounds nice even with phone recording, myself I have a gas for Fortin Meshuggah.
But tell me - 700 euros could get you a decent branded amp, was it worth it to spend it on DIY?
 

albatros_1994

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Sounds nice even with phone recording, myself I have a gas for Fortin Meshuggah.
But tell me - 700 euros could get you a decent branded amp, was it worth it to spend it on DIY?
well, i'm not sure you can buy an amp that sounds this good for 700 euros, at the end of the day i love and enjoy the process, i like learning more about amps and tubes, i like that i can repair and replace all the parts myself if something goes wrong and can modify and add/remove functions i need or don't need. I can build my own stuff, just because i like it. It's cool to just let someone use it knowing every single detail and part, why is it behaving in a certain way. They hear noise, i see the parts working together. I'm 100% sure you are gonna get something better if you buy it, but i see those 700euros in this case, as an investment on myself.

One thing i wanna do in the future is hoarding cheap amps and modify/rebuild them. Stuff like Bugeras 6262 or 333XL, Crate BV120-H are amazing, i have 4 of those in total now. I'm talking about all-tube 120w amps that you can get for 200-250 euros. A joke. And i can get a Mesa Boogie or an ENGL or a Fortin out of those. :) Best hobby ever
 
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