I started my Maruo last night, great layout and the labeled parts are a bonus.
For volume control I bought a 10K ladder attenuator from DIYFidelity in Auz. which is a great deal for the quality but a lot of work.
Bought a 400VA 24V dual sec. toroid from Plitron and I'll build the enclosure out of 8mm aluminum and a piece of crotch chestnut my brother gave me.
This is a great project and I'm using it to show my friend Nguyen
(Me Kong) the joys of DIY.
Tony D.
For volume control I bought a 10K ladder attenuator from DIYFidelity in Auz. which is a great deal for the quality but a lot of work.
Bought a 400VA 24V dual sec. toroid from Plitron and I'll build the enclosure out of 8mm aluminum and a piece of crotch chestnut my brother gave me.
This is a great project and I'm using it to show my friend Nguyen
(Me Kong) the joys of DIY.
Tony D.
Attachments
billabong said:
Hi Audie,
I always get my toroids from Harbuch http://ourworld.compuserve.com/homepages/harbuch/harbuch.htm. They have a great selection.
They are usually cheaper than the normal suspects, but postage to Mt Isa may be a show stopper.
Regards
Hi Russ,
Both the R-11 I received measure out as 1.4 ohm instead of the 1R listed and I am wondering if this is a change in the spec.?
I have lots of 1R resistors laying around so no problem, just curious if this is change?
T.D.
Both the R-11 I received measure out as 1.4 ohm instead of the 1R listed and I am wondering if this is a change in the spec.?
I have lots of 1R resistors laying around so no problem, just curious if this is change?
T.D.
In that spot it will not matter, though it seems a little odd.
That part is definately a 1R 1% resistor so I would see if that measurement is within your DMMs margine of error. Many DMMs do not measure low ohm values very accurately.
That part is definately a 1R 1% resistor so I would see if that measurement is within your DMMs margine of error. Many DMMs do not measure low ohm values very accurately.
Tony D. said:
Put your DMM on the lowest ohm scale (usually 200R) and shunt both probes.
How much does it display?
0.4? 😀
Thanks Greg,
Great link. Choice of two 400VA toroidal T/Fs. Will phone my order in tomorrow for the smaller one, which is the same size as the 300VA, with only a 1% regulation penalty.
Audie.
Great link. Choice of two 400VA toroidal T/Fs. Will phone my order in tomorrow for the smaller one, which is the same size as the 300VA, with only a 1% regulation penalty.
Audie.
gain..?
Hi fellas
Is it possible to raise the gain (change R4 from 1k to ~680R). There doesn't appear to be any errors in component placement and the amp works great. Sadly using a 20k stepped attenuator doesn't give quite enough output. No headroom.
Compared to what it's (My_Ref) replacing (3886 gc) it gets loud but only moderately so, and that's all the way up! I can add a pre with gain later but would prefer to listen using a passive to decide which I prefer first.
To put it in some perspective, when the GC volume pot was at approx 1 - 2 o'clock the Mauro is at Max :/
Is there a potential problem in raising the gain by changing R4?
Thanks for reading 😀
Cheers 🙂
Hi fellas
Is it possible to raise the gain (change R4 from 1k to ~680R). There doesn't appear to be any errors in component placement and the amp works great. Sadly using a 20k stepped attenuator doesn't give quite enough output. No headroom.
Compared to what it's (My_Ref) replacing (3886 gc) it gets loud but only moderately so, and that's all the way up! I can add a pre with gain later but would prefer to listen using a passive to decide which I prefer first.
To put it in some perspective, when the GC volume pot was at approx 1 - 2 o'clock the Mauro is at Max :/
Is there a potential problem in raising the gain by changing R4?
Thanks for reading 😀
Cheers 🙂
In a Italian forum Mauro stated that this amp needs a low impedance at its input - a active pre or a max 10k pot.
Hope it helps
Andrea
Hope it helps
Andrea
Thanks Andrea & Brian.
Very conveniently I have one of those alpha A10k pots laying around so I'll give it a whirl 😀
I'm curious if the amount of spl's being put out is 'about right' or if I should be more closely scrutinizing the boards to see if I have actually made an error with component placement.
So essentially another question would be, has anyone else gone from a basic GC setup using a passive pre to Mauro's design and wondered where the volume went? And to be clear, I do realise this amp is no longer a clone, it's just that they're the only reference I have to go by 😉
Cheers
Kendal
Very conveniently I have one of those alpha A10k pots laying around so I'll give it a whirl 😀
I'm curious if the amount of spl's being put out is 'about right' or if I should be more closely scrutinizing the boards to see if I have actually made an error with component placement.
So essentially another question would be, has anyone else gone from a basic GC setup using a passive pre to Mauro's design and wondered where the volume went? And to be clear, I do realise this amp is no longer a clone, it's just that they're the only reference I have to go by 😉
Cheers
Kendal
I had no problem with a 50K Alpha Pot in front of the amp. Now am burning in the Kookabura Beta in the same place.
One of my several hook-up mistakes was reversing the input leads. That caused me a similar problem to what you describe.
new amp born
It's playing Roy Orbison right now. The offset is 2.4 mv on one channel and higher on the other. How can offset be adjusted?
The sound is very detailed and the low bass is very good. Also, have 2 ceramic caps left over-c10-100pf. dc volts at the ps caps. is 32-34 volts . Seems a little bright at times but needs burn-in.
cheers
doggy😎 🙂
It's playing Roy Orbison right now. The offset is 2.4 mv on one channel and higher on the other. How can offset be adjusted?
The sound is very detailed and the low bass is very good. Also, have 2 ceramic caps left over-c10-100pf. dc volts at the ps caps. is 32-34 volts . Seems a little bright at times but needs burn-in.
cheers
doggy😎 🙂
Attachments
Re: new amp born
Excellent! Very good news. Enjoy it.
As for the offset as long as it is below 20mv or so I would not worry at all. In fact many chipamps run with 3-4 times that.
Offeset is sometimes a function of parts matching, sometimes a function of parts deviation of the LM3886 itself. The LM3386 has a certain amount of DC offset no matter what, and it generally changes with temperature.
Cheers!
Russ
doggy said:
Excellent! Very good news. Enjoy it.
As for the offset as long as it is below 20mv or so I would not worry at all. In fact many chipamps run with 3-4 times that.
Offeset is sometimes a function of parts matching, sometimes a function of parts deviation of the LM3886 itself. The LM3386 has a certain amount of DC offset no matter what, and it generally changes with temperature.
Cheers!
Russ
I might be sailing close to the wind here..
I'm using a 230V trans with 25v secondaries, but the mains here is (just measured) 245 volts. This gives 38volt rails. Is this dangerously high?
I think the3886 is rated to 42v rails, but most comment I've seen recommend 30-32v rails. Do the chips take out the speakers when they pop?
Also, any idea of sound changes with different rail voltages?
I'm using a 230V trans with 25v secondaries, but the mains here is (just measured) 245 volts. This gives 38volt rails. Is this dangerously high?
I think the3886 is rated to 42v rails, but most comment I've seen recommend 30-32v rails. Do the chips take out the speakers when they pop?
Also, any idea of sound changes with different rail voltages?
float said:I might be sailing close to the wind here..
I'm using a 230V trans with 25v secondaries, but the mains here is (just measured) 245 volts. This gives 38volt rails. Is this dangerously high?
Also, any idea of sound changes with different rail voltages?
It is high, but it should work fine. If you have access to a Variac it would be good to check it out by ramping it up slowly.
With 8ohm speakers you will have a bit more headroom, with 4 ohm or less you risk overdriving, but you are not too wildly over the line.
float
My secondaries measured 25.4 v,a.c. in to the boards but at the p.s caps turned out to be 32-34vdc. when the amp was running.
cheers
doggy🙂
My secondaries measured 25.4 v,a.c. in to the boards but at the p.s caps turned out to be 32-34vdc. when the amp was running.
cheers
doggy🙂
Bloody site just burped and ate my post!
I'm checking it out by playing lots of music 😀
Daytime mains may be lower voltage, and with a bit of sag at high volumes hopefully all will be well. I'll keep an eye on chip temps during a LOUD session.
I'll say now that technically this amp is a little gem. No switch -on or -off thumps, very low dc offset and dead quiet. Thats more than a lot of commercial amps can claim. Great job! 😎
Russ White said:
I'm checking it out by playing lots of music 😀
Daytime mains may be lower voltage, and with a bit of sag at high volumes hopefully all will be well. I'll keep an eye on chip temps during a LOUD session.
I'll say now that technically this amp is a little gem. No switch -on or -off thumps, very low dc offset and dead quiet. Thats more than a lot of commercial amps can claim. Great job! 😎