"Knock-off" Mesa boogie dual rectifier pcb worth it... ...or not?

[Thecomedian]

not to be repetitive, but the first amps were designed by scientists who worked with EE and stuff for a living, so it's definitely going to be a real "job" to put something complicated together and have it work properly.

[defaced]

Maybe they want to cull out the folks who jump in with the sort of rubbish you see from some first posts around here.

"I have X question because I fancy myself as capable of doing Y... so can someone step me through Y from start to end, its ok I've done Z before and it EVENTUALLY worked out".

There are lots of communities that don't have quite that level of gate for a learning person, I know - I lurk them.

Correct.  And to keep spammers out (which has worked, thankfully).

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For your reference.  The schematic linked here looks complete, but I can't verify its correctness: http://schematic.danrudin.com/index.php?dir=Mesa_Boogie/
Yes, you will have to do your own layout, which is not trivial but can/has been done, but from this it is possible to build the whole or just part of the amp.  Personally, I'd take a SLO or Avenger layout and change the values to match that of the Recto.  The Recto is more/less a modded SLO (and the Avenger is just the OD channel of the SLO). 

[mistahead]

I'm full of sedatives (thank you Dr.) so I could be off and talking complete shit here...

Basically in all the Mesa setups I've seen in use they basically only every get used "balls out metal aye", with some exceptions of applications with could probably be done better and cheaper, despite being bloody versatile bits of kit.

So really - what is/are the qualities that make the Recto so appealing? It is not beyond reasonable to build a stripped down amp that does "Just that thing" or to take a much simpler amp starting point and frankenstein in a bit of Recto flavour.

Mind you I don't build amps over 2W yet so salt is available in grains for this thought, but the premise in strong enough in general engineering terms.

[madstayen]

i dont want to build one as of yet. but it would be good to start reading about it, and slocones is app. the best site do get the knowledge you need and start building small amps and work your way up the ladder....er, something like that.

[defaced]

Never been a fan of the start with a "small amp" advice.  My first amp project was a 100w power amp prototype.  My second was a prototype build of a VHT Deliverance where I had to make my own layout because only schematics were available.  That layout took me probably a month to do because I had to learn about layouts (and I still took me a long time to fully understand a few things about them).  A better recommendation would be to build what you want but take the time to understand it fully and build it correctly.  Most of the new/hard/dangerous stuff about amp building applies just as much at 2w as it does at 200w. 

The SLO Clone forum is a terrible place to learn the basics because it's assumed you know them when you start trying to build those sorts of amps.  It's alot like a hot rod club for cars.  If you want to know about bore, stroke, compression, turbo boost, ets, you go to the hot rod forum.  If you want to learn how to do a tune up, oil change, tire rotation, you go to a forum that's geared toward beginners because the hot rod guys are going to either ignore you, or really confuse you because they're going to be talking to you in a language you don't understand yet.   Same basic analogy applies to amps.

If you want to learn about tube amps, this sticky I have on another forum would be beneficial:  http://www.byocelectronics.com/board/viewtopic.php?f=49&t=34216
The ampbooks.com site has a whole write up on the SLO.  Really worth reading as it applies directly to the Recto.  

[mistahead]

I build small amps  as the parts are in my box and I'm too skint to buy new tubes for my Laney (well I assume the tubes have crapped themselves, intermittent "gating" to silence, getting worse with time and time running).

I would really like to cut my teeth on a single channel high gain that pulls in the filthy low end of the laney some (squares it up a bit maybe) but more or less carries the a similar idea to the wall... but that's a bigger job than buying matched tubes and swapping them into my amp (oh and replacing that @#$%ing volume knob with the deadzone around 4-5).

[defaced]

What Laney amp? I want to pull the schematic. Once you get new tubes and fix that pot, it might make a good mod platform.

[mistahead]

Laney GC-30 (older one) combo with the 10".

I've got the schem at home - it looks simple enough to step through so I have hope.

[defaced]

Hmmm, three preamp tubes. Not a perfect setup to turn into a recto, but with two MOSFETs in the phase inverter position, you'd be good.    Since the PI is a functional stage in most applications of this am (as opposed to a tonal stage), putting a MOSFET here shouldn't have an adverse effect on the sound of the amp. Can you source the LND150 or ZVN0545 in your country?

[mistahead]

Wow... I am saving these notes for when I can start approaching this... it wasn't me originally after a Recto but from what you've said pushing my blues/rock amp itself (rather than the boxes before it) into that range is definately interesting.

I don't consider sourcing parts "locally" a requirement - in this day in age if it is on Earth you can pay to have it in your hand if you want it enough!   

[bancika]

Hmmm, three preamp tubes. Not a perfect setup to turn into a recto, but with two MOSFETs in the phase inverter position, you'd be good.    Since the PI is a functional stage in most applications of this am (as opposed to a tonal stage), putting a MOSFET here shouldn't have an adverse effect on the sound of the amp. Can you source the LND150 or ZVN0545 in your country?

I'd be careful about replacing later stages with FETs. Some say that PI and output stage do get overdriven even with these hi-gain amps that make most of the distortion in the preamp. You can take precaution and lower the signal hitting the PI to reduce risk of overdriving, but you may loose some of the flavor added by PI overdrive.

I know it's not the same, but I tried to do similar thing with mosfet source follower. Sounded horrible I would use LND150 stage as the very first gain stage because it won't be overdriven, and you can pull even more clean gain than with triode. Also, you can safely use it as gain recovery stage after the FX loop.

Cheers

[defaced]

That's a doable approach too. The problem will be getting the same gain from the stage. The LND150 is much better at its job than a tube and needs to be cooled a bit to achieve similar voltage gain.

Every amp when turned up enough will distort the PI. The question is does it happen in the application and does it sound bad. Since I know in my applications I'm much lower than needed to distort the PI, I would go that route. Details count, bit luckily parts are cheep and experimentation is easy.

I've also done later stage MOSFET substitution and not found it to sound bad. Its not identical to a tube, a bit more sharper/higher order harmonics, but not bad, but again it depends on the application of the amp. I wouldn't be making the same suggestion for a plexi for example.

What MOSFET did you use as a follower substitute?  Most of my work has been with the LND150.

[bancika]

It was long ago, LND150 wasn't popular back then. I think I used IRF820
I wanted to do hot-rodded marshall type of preamp with two tubes and replaced the cathode follower. It's different than PI because it will get heavily ovedriven. Sounded harsh and cold.