[Daniel Pumphrey]

Now that the smoke is beginning to clear over in DIY about the final unveiling on the RA-1 circuit board several thoughts come to mind immediately.
In DIY we all had a laugh about the cheap components used in this amp. Now the next step is a clear and simple way to improve the performance of this amp if you already own one.
Obviously you can't remove the circuit board easily, so a possible opamp change can't readily be made. My original criticism of this amp was the loud pop on power-up and down. Now we see why. The two 9V batteries split in the middle without a resistive divider and the .1 capacitor used for the supply is unbelievably low. This is the cause of the pop. Not only a pop but serious problems can occur if one battery has less output or current. No two batteries stay the same very long.
There are several cures for this power supply. Since we can get at the batteries and their wiring, we can change things here for the better.
This amp could be improved by adding a Burr Brown Buf 634 to create a virtural ground, another possible change would be to use a TLE 2426 by Texas Instruments to do the same. I prefer the Buf 634 because it has the best current capacity. This will be wired as the Data Sheet states. The batteries are wired in series into this device. Following the Buf 634 we could use a couple Electrolytic capacitors of the proper rating.
This mod will remove the loud pop and supply a very stable virtual ground supply which will improve the performance of this amp. Total cost about 10.00 at the most.
I don't know exactly how much room exists inside this amp, but it should be enough to allow this mod. I will check with my brother and have him measure the available space inside.
The best aspect of a modification like this is the fact that nothing is altered which can't be easily returned to stock, with absolutely no damage to the amp electrically or cosmetically.
Dan

 

[ILoveGrado]

Very interesting Dan. Please do keep us updated.

 

[rickcr42]

Why would you want to ?
It seems that anyone purchasing this amp would be using Grado cans,and the amp is "voiced" to bring out the best in said cans.
The op-amp used by grado puts out 70ma which is VERY respectable.The cap used appears to be a solen fast cap,also a good grado match,maybe a pot upgrade to a Black Beauty but again-anyone purchasing the amp would probably have grados and if they were into DIY would probably just do a "scratch" amp with parts they prefer.
Why tear up a perfectly good amp ?
The fact that the cicuit board is potted means you have a definate possibility of destroying the wood block cabinet.As far as using an artificial ground driving device,why not go right to using a BUF634 ? This would provide more current.
Turn on clicks ? All my amps do this,sometimes the cure is worse than the disease so I live with it.
Do I own this amp ? no.
Have I heard this amp ? No.
Would I purchase this amp ? Again no.But only because I prefer to build my own.But if I did not then the answer would be probably yes.Not everyone into headphones and amps is also into DIY.
Nothing personal but i know you do not like the RA-1,you have said it, so why not just let it go ?

 

[Rubin]

Hey dan

I'm sure that your suggestion is well intended, but please don't advise people to open their RA-1! I practically destroyed mine tryng to get it open. Plus there is definitely no room to add ANYTHING in there, it is so cramped inside. It would be much better to try this when building an amp from scratch. It is far to dangerous, not to mention pointless, to upgrade the RA-1.

 

[Daniel Pumphrey]

Ok guys, If you read what I said you would notice that the recommended mod would be done where the two batteries are located and is very simple to do without access to the board and would take up as little as 1/4"x3/4" total or as much space as one buf 634 TO-220 vertical.
Rick, If you had the Grado amp you would know just how loud this power-up spike is. It is 5 to 10 times as loud as any Diy amp I have built, and is enough to damage some sensitive phones, plus start the good old grado Grattle. This is caused by the .1 uf cap on the supply and is very loud. This small mod will certainly improve things without harming anything, plus it can easily be returned to stock as my thread states!
Just adding the buf 634 would absolutely improve the amp without a doubt even if the extra caps are left off.
Dan


D

 

[thomas]

In my experience, the larger the powersuply bypasses, the louder the turn-on thump, all things being equal.

Using larger caps in itself will not solve the turn-on thump problem.

What probably caused your problem is excessively mismatched batteries, causing a large DC-ofset at the output. Adding a simple resistor divider is the solution to this problem. Or you could just replace both batteries at the same time.

Anyone who knows enough to construct a virtual ground driver out of a BUF634 could contruct a basic cmoy/RA-1 from scratch. This would be a MUCH smarter idea than trying to cram a few more parts into the wooden case.

The point is, anyone that could do these mods wouldn't purchase the amp in the first place. People buy the RA-1 because they want a finished product, instead of spending the time + money on DIY.

 

[Beagle]

Quote:

In DIY we all had a laugh about the cheap components used in this amp

Maybe you did. I had a bigger laugh watching how you waste time that could be used to listen to music. Music, remember that?

Quote:

My original criticism of this amp was the loud pop on power-up and down

Is that what you do, put on a pair of phones and keep switching the unit on and off so you can bitch about the pop? You keep bringing up that pop. Here's a solution. Turn the unit on THEN put your phones on. Works for me. Then I enjoy the great sound of the music I listen to. I don't get anal about what makes it sound good, I'm just happy that it does.

Sorry if I come across as a bit nasty but you just beg for it, like a pie in the face.

 

[Daniel Pumphrey]

I was simply trying to help the few who paid so much for something that needs serious help.
More capacitance than what causes more pop? .1uf!This amp has no electrolytics at all (what-so-ever). Adding even 25uf will help smooth out the pop which is actually a spike, and spread it out over time a little. .1uf is not even considered power supply bypass except at the very end going right to the chips. I have Never seen another device, even the very cheapest which has No Electrolytic Caps in the power supply.
No I don't sit and turn amps on and off, just the suggestion shows where you are or have been, or who your audio friends are.
Good sound! If this is good sound, then why bother with a Headphone amp in the first place.
I know many who like to modify gear like this, especially if it is this easy.
I like to leave my headphones plugged in to the amp and would not trust my precious ER4 drivers to this loud spike or any other good phone for that matter. Simply turning the amp on without the Headphones on is a stupid cure. The Headphones still get the brunt of the spike, you just don't hear it. Sort of like the Taliban putting their heads in a hole to escape the bombs with the faith that they are protecting themselves.
Those who constantly copy and paste others posts out of context to make a point must not be able to remember what was said in the first place.
The bottom line is there are some pissed off people who paid a lot for an amp and now want to take it out on anyone criticizing that very amp, even when that criticism is leading to a positive attempt to fix the problems the manufacturer refuses to.
Some people just can't be helped, they just bite the hand that feeds them.
Who would want to build an inferior amp when there are superior projects available which are just as easy to build. In fact my own amp boards use dual opamps and I could easily just change the opamp to a .25 cent part if I wanted the so called "REFERENCE SOUND"!
Now to wait for the copy and paste artists to rip this post up also. None of this is helping anyone who might actually want good audio even if they must modify an existing device to get it.
I really did think Headfi was a place where these things were discussed with the goal of getting to the truth about certain products and even attempting to improve the state of Headphone Audio. My posts are focused on the subject at hand and even offer ways to improve gear found to be inadequate or wanting. If my posts help one out there then putting up with the flak from dissenters is certainly worth it.
If I convince one to build their own superior amp instead of wasting a Lot of money on an inferior one, then I welcome the flak from the few who seem to have their feelings hurt in some way and want to make me look bad in any way they can.
What does a "Pie in the face" have to do with audio? The pie in the face actually occurred when the offended writer opened his wallet to buy the amp in question.
"Pie in the Face", Stupid Pet Trick #462 from our resident audio K-9 "Beagle" aka ????? I think I'll do some research about the ankle biting tendencies of internet posters who hide behind silly names and we certainly have out share of them here.

Dan

 

[Neruda]

tell 'em, dan!

 

[skippy]

a $5 buffer used to create a virtual ground for a circuit that has a 30 cent opamp? i'd rather use the buffer for the signal.

 

[Beagle]

Daniel, I am just tired of the repetitive holier-than-thou nature of your posts ragging on the RA-1, it's getting old. You don't like it, fine, move on. But please stop trying to insult the intelligence and tastes of the people who own it and like it.

 

[Daniel Pumphrey]

You're right about that Skippy. But as far as I can tell it is the only way to improve on this circuit. The opamps aside, improvement to the power supply can really help, especially as the two 9V batteries will drain at unequal rates. This is discussed at Headwise and two batteries with the ground in the middle is not a good way to do things. Adding a resistive divider would be cheaper but the 6.00 or so part is the best alternative and adds such a little cost to the amp. A cheaper part would work too with less current capability, even using half the opamp used in this amp would supply a 70ma virtural ground capability but would also take up more space than the 634 TO-220 if used with a small board.
Dan

 

[kwkarth]

Dan,
I just wanted to express my appreciation at your offerings here regarding improvements to the RA-1. People who own the RA-1 should appreciate the opportunity for improvement.

I like my OBH-11SE a lot and think it's a great amp and a great value, etc, etc. but if you were to offer some well thought out improvement suggestions for it, I would be first in line to take you up on them.

Hey folks, are any of the products we use "perfect?" Are *any* of them beyond any improvement? If anyone here here has hit the pinnacle, let me know. In some other thread, I recall someone offering to turn in their "audiophile" card. Well, let me tell ya, this is a really fun hobby for me and the day I get to the point that there are no more improvements that can be made, is the day the hobby is over and I can turn in my audiophile card.

Thanks again Dan!!

 

[rickcr42]

Well if for some reason I ever aquire the RA-1 the only improvement I would consider would be to build a killer dedicated power supply.Battery operation is fine for portability and due to the lack of AC line hum and noise the capacitance requirements are low (negating the need to increase the caps) so fiddling with artificial ground circuits would be of no benefit to me.
Instead I would do a version of the Jung super regulator and match the battery clip to a matching connector.That would mean ZERO changes to the actual amp.
But again,if i were not into DIY I could think of FAR worse amps for the money than the stock factory unit.

 

[livingplasma]

Almost anything you buy can be improved because the manufacturer is most likely not going to use what you think are the best parts/configuration etc. I'm sure Grado Labs designed the RA-1 to sound as good as can for its intended purpose, but there was probably a price constraint on what parts could be used or added to improve it further (remember, they have to make a lot of these so ordering the slighlty more expensive parts or increasing the number of parts needed can increase their spending beyond what they can afford). The DIY'er has it easy because they can afford to use their choice of parts to maximize performance at any cost, Grado Labs would have to aim for what they consider an acceptable performance to cost of manufacturing ratio for the price they're asking to make a profit.