Leegazzy - Carvin Amp

[dimirock]

Hi guys! First post here...
My name is Dimi Nalbantov. I'm guitarist from Bulgaria. I was reading the forum and at the end of my building process frustration, decided to post and hopefully to get some help!

I spend the last 10 years working with software, making my albums with amp sims...

Also keep in mind, I have almost zero knowledge in the Electronics mater! Learning every day!

Lately searching the web I've found some websites posting vero-board based schematics of some famous amps.And after a few times I decided to start learning and to build my first DIY pedal.
Of course it was the Legacy Amp by Carvin build for Steve Vai. My teenage years guru...!



In the last 5 days / with the help of my wife/ sorting the parts and even soldering. I've build 4 vero's of this layout. the firs one is still running.

But I cant get them working with my 9v 1700amperage power suply,/ Its capable to power almost 10 boss pedals/ then I had in storage 12v and it produced signal. Succesifuly biased my j201 and 2n5457 at 4.5-5v
But the gain is weak and farting in some points like Fuzz Face pedal.

After that I started to read and found the original schematic of the Legacy amp and what Ive found is that the schematic is 100% copied .... I was like WTF???
The tubes there are runing at 300v around and each stage of tube at 180v....

Reading the commentary below some YouTube videos and the Blog from where Ive got the layout , there were some working projects and some of the guys had the same problem like me....

Then Ive found this web site http://www.runoffgroove.com/fetzervalve.html
But the information for a newbie like me is overwhelming.

Please help me to modify the layout if its needed or maybe I'm going in the wrong direction!

Thank you in advance!
If someone is needing something in return. I have a good background in the recording and playing guitar. I'm always open to help!

Just wanted to build an nice analog emulation/ simulation of one of my all time favorite amps. I'm just tired playing software amp sims!

Dimi

www.nalbanatov.com

[deadastronaut]

hi, and welcome, i'm sure if its on tagboard effects then it has been thoroughly tried and tested...

here is the 9v leegazzy schematic if it helps.

http://gr1ng0.tripod.com/Leegazzy/Calvin_Layupe.jpg

from this thread..'

http://www.diystompboxes.com/smfforum/index.php?topic=21902.msg137554#msg137554

[dimirock]

Thanks!
Yeah, I know about these too. They are 99% identical.
Today tried the schematic with 18v and it sounds more like the real deal.
Still need to realize what is wrong with 9v

[bool]

Well, Dimi from KVR has gone "off plugins".

WRT your issue, it's most probably the so called biasing isn't good for 9V - or IOW, the fets bias more properly when powered with 18V but not under 9V.

If it "sort of works" at 18V there is a chance it will under 9V (or 12V) for that matter, if you adjust the bias "just right".

If the fet's characteristics are too "out of spec" to work with 9V, imho your best bet would be to fine-tune the ones that work with 18V and use it with that voltage.

[ggedamed]

You should build the JFET tester from the Fetzer Valve page to check Vp for your JFETs. Then you could use the calculator at the end of the page to get a ballpark figure for the drain voltage.

Right of the bat, a 4.5V drain voltage seems a bit low. Using the Fetzer Valve page calculator with their 2N5457 example gives a drain voltage of 6.51V.

Also, I think you're using a switched power supply. Just shooting in the dark here, but try inserting a 100 ohm resistor and a big electrolytic capacitor (100-1000uF) before the positive rail.


Side note: your signature link has a typo.

[dimirock]

Thanks guys! Going to build the tester now!
Then I will report back!

[bool]

You know what? I think the best thing to do would be to build an "audio probe" (google).

Then probe each stage (starting with the first one) and adjust the trimmers to the point when it "feels right" - when playing the guitar. With using the probe you in essence bypass the rest of the circuit so you can work on it stage-by-stage.

You'll get the hang of it eventually. There is usually an overlap between the "meter readouts" and adjusting by hand till it "feels right" when playing.

So, fet testers and an audio probe aren't mutually exclusive ...

It can sound good with low-voltage amp-sims when you under and overbias stages in a "staggered" manner ...

[J0K3RX]

Dimi.. Sounds really good man, and your playing is wicked good as always   Are you givin it a bump with a tube screamer or was that just the pedal straight up? JFET preamps sound a lot better @ 18v in my opinion anyway but curious if you got the 9v problem sorted.

**WARNING**
Watching this video may cause involuntary loss of control of bodily functions, feelings of inferiority, inadequacy, shame, impotence and uncontrollable crying! Only watch if you have excepted the probability that no matter how much you may try, you will never sound like this!  
https://www.youtube.com/watch?v=mPOmrRstUdw

You might consider etching it or having it fabbed in a board house.. I know you can etch if you want to, I have seen some of the guitar restorations you have done and etching is sissy kid stuff compared to that!   I built this a couple years ago and I thought it was pretty good, not really what I was looking for but it did sound like the Legacy... You really bring it to life! Perhaps your pickups are hotter than mine were but I thought it was lacking some gain, it wasn't too bad though especially after throwing a tube screamer in front. I tried to get a little more gain by using J201's for all stages except the first stage which I left a 2N5457.. Actually sounded better I thought.

I don't know if you have seen this layout but it's pretty good, same schematic as the vero... You can download the Sprint file also.
http://guitar-gear.ru/forum/topic/2141-carvin-leegazzy/page__p__51223__hl__leegazzy__fromsearch__1#entry51223

Might check this out also, the diode clipping and the tone stack look interesting.... There are a few really good mods for the actual Legacy amp too that might be interesting with this JFET version.
http://www.carvinservice.com/crg/schematics/MTS3200%20REV-E.pdf

Here is all the Carvin stuff if anybody is interested..
http://www.carvinservice.com/crg/schematic_finder.php

Man, I was just thinkin, if you decided to design/sell your own pedals and demo them yourself!  

[dimirock]

Hi guys! Still having problems with the 9v suplly. Sound overdriven and fuzzy.

J0K3RX: This videos is made by someone else, but not me
In fact this was the video that I've got my inspiration....
Even, went ahead and wrote him a few PM's but still no response!

His build is amazing and the tone is spot on!!!

Thanks anyway!
Cheers
Dimi

[dimirock]

Here is a video using my 5th vero build...
https://www.youtube.com/watch?v=RwNNb7tbvqU&feature=youtu.be
Powered with 19v power supply from a laptop.
Having a great problem running it on 9v.
I hope for some guidance and help!!!
Thanks guys!

[J0K3RX]

Hi guys! Still having problems with the 9v suplly. Sound overdriven and fuzzy.

J0K3RX: This videos is made by someone else, but not me
In fact this was the video that I've got my inspiration....
Even, went ahead and wrote him a few PM's but still no response!

Not you? Ha ha... no kiddin, wow! Don't I feel stupid now....   So that is not your post about your wife helping you and even soldering?  


Anyway, about your problem running @ 9v. You may need to use 100k trimmers instead of 50k.. When running at 9v read the voltage right at the drain of each 2n5457. If you don't get the bias voltage low enough/high enough on any single one or more of the stages you will get a gated farty sound. Not only that but the sound you get when running @ 18v or even 24v will not be correct either. It may work and it may sound better than 9v but, it still will not be optimal. If you don't have any 100k trimmers then you can add a resistor between the supply and whichever stages can't be dialed in.


Edit: Another thing with this schematic, the guy who copied it into the JFET emulation did not take into consideration the power filtering... On his schematic the power is coming directly from +9v into each stage... If you look at the actual Legacy schematic you will see the power coming in from (D) right after it comes out of the transformer and goes through some filtering and about 8k of resistance until it gets down to about +385v. You could do the same except don't use 8k but rather try 1k instead.. This should get you in the range you need. If 1k resistor does not do it then try 2k etc.. You could even use a trimmer to dial it in so you don't have to keep swapping resistors.

Legacy 100 tube schematic
http://www.carvinservice.com/crg/schematics/VL100F.pdf

~Jim

[J0K3RX]

Another thing... forget about the 4.5v/5v biasing and try to adjust the trimmers by ear... it will take a little time because each stage will affect the stage after it but you should be able to get to a reasonable point.. another way you can do is set them all for 5v and then go over each one and fine tune / adjust by ear.

[dimirock]

You said: "You could do the same except don't use 8k but rather try 1k instead" On which part of the translated schematic? 


Biased them by ear...the same Fuzz sound on 9v
Something is sucking power btw every jFet. I'm not sure.

I hope, I will learn how to measure every Transistor and calculate the new resistor for each Source leg. Maybe this will help...
And if it will work, hope there will be no frequencies and character change...?

[J0K3RX]

You said: "You could do the same except don't use 8k but rather try 1k instead" On which part of the translated schematic?  

Something is sucking power btw every jFet. I'm not sure.

I hope, I will learn how to measure every Transistor and calculate the new resistor for each Source leg. Maybe this will help...
And if it will work, hope there will be no frequencies and character change...?

What do you mean by "sucking the power"? What is the voltage on the other side of the 100R resistor? I wouldn't start changing the source values... Depending on what you get when you read the voltage on the other side of the 100R you may want to make that a 1k or more..

The plate resistors on the real Legacy tube pre are 220k except for stage 3... like I said I would use 100k trimmers but since you may not have any or you may not want to change them you can drop it slightly at the power to bring your bias pots into better range for adjustment.

Edit: Setting the bias on these is kinda like setting up a floating trem.. You adjust the bias on one fet and it will slightly throw the one before it out and by the time you get to the 4th one you have to go back and re-bias the first one again, then the 2nd etc...

[dimirock]

Thanks for all your help and useful information! Deeply appreciate it! 
Still struggling to learn how to measure the Vp and Idss readings...then I think I will make a progress!

Thanks
Dimi

[J0K3RX]

Dimi, have you heard the CAE 3+SE?  What would you think about a JFET version of the high gain channel?

[dimirock]

Checking it out now. I think it will be a great preamp!

Is it possible to help me with this layout:
I have the readings on my meter, but because of my lack of knowledge and background in the electronics.
I cant figure it out how to convert the readings in Vp and iDss.
It says:
1.Multiply by 10 the reading for Idss in mA/
2. Negate reading tp obtain the actual Vp

Thank you!!!

[bool]

Dimi ... skip this - for now. First, try this:

1. power the circuit with 9V (the problematic voltage)
2. measure the voltage at fets' drains (D's) - a.k.a "on the trimmers"
3. try to set up the trimmers so that it reads circa 6V (two-thirds the supply voltage)
4. if not, record the voltages and post them here so hopefully someone who knows the ins and outs of this exact circuit can help you with a pinpoint-precise advice.

[dimirock]

Thank you!!!  I can get any Drain Voltage from 1 to 8-9... If I set them in 4.5-5v it sounds like a slightly over-driven amp.

I'm geting 9v. on the input leg of the trimmer if I lower the voltage for the Drain.
Here are the readings.
Dimi


________
Q1:Trimmer readings:

Voltage on the trimer: In leg: 8.98 ; Drain leg:6.06

Q1 Fet - 2N5457: Drain: 6.06
                        Source: 0.70
________
Q2:Trimmer readings:

Voltage on the trimer: In leg: 8.96 ; Drain leg:6.00  

Q2 Fet - 2N5457: Drain: 6.00
                       Source 0.83
________
Q3:Trimmer readings:

Voltage on the trimer: In leg: 8.96 ; Drain leg:6.00

Q3 Fet - 2N5457: Drain: 6.00
                        Source: 0.85
________

Q4:Trimmer readings:

Voltage on the trimer: In leg: 8.94 ; Drain leg:6.00

Q4 Fet - 2N5457: Drain: 6.00
                        Source: 1.05

[dimirock]

I can confirm, this layout is not confirmed! And it is misleading!

I'm not trying to be rude or something, but for people like me, making theirs first steps in this mater - electronics, it is really discouraging!
Considering no one from the guys with experience is responding...

Also comparing the "real" schematics from the manufacturer. Those are 99% copied to the vero boards.
Sorry for trying to get some guidance.

I had a big hopes that some of the guys that succeeded to build theirs pedals from the vero layout, and Dimi
from Italy/ right/ with the great video demo will respond.
But, it is obvious this is not for beginners

Everyone in this stage in our society is keeping his secrets and if we learn to share and help, then the Earth will become a better place.

Lastly, I've tested the boards and they sound "great" but from 19v power supply.

If you know how to modify your current batch of jFets corresponding elements in the each stage, then you will get it working as it should.
But, again this is not for beginners!

p.s
This was written after 18 days of reading the forum. And it is not aн act of desperation! Иt is an appeal to the mans who are tired to explain every day the same thing to the smallest ones...

Best Regards,
Dimi