dreamie

The OPA637 is now in the phono. Seems to be a balance of the OPA2134 and AD8620, albeit with more bass. The "clipping" sound disappeared when the AD8620 is removed.

Perhaps my supplies are approaching its limits. (+- 12V supplies from a SMPS, so voltage should be closer to +-13V, the limits of AD8620, since the SMPS is not really loaded)

bpripadi, my findings have been quite consistent with yours. I would like something which is slightly brighter... and it seems to be the AD8066 from your thread.

Anyone got spare AD8066s? Willing to exchange for opamps? hehehe... Still got some AD797 and AD8610/20s with me.

Just swapped the AD8620 into the phono stage. It seems to be clipping now and then, at least that's what I think clipping sounds like.

dreamie, I am no expert but capacitors take time to burn it. That has been my experience so far and the symptom of the caps not working full capacity has been weak bass. Give it some time and see.

The components in the current power supply are recycled from the previous powersupply.. and with the previous power supply, i didnt let it burn in either and that bass stuck there!

One strange thing is happening right now! I have switched off power to the preamp and sound is still coming out, albeit at a lower level. Maybe the signal's now passing through the feedback resistor.

Hi all,

Rebuilt the powersupply of the AD8610 preamp few hours ago and I realised that there is a slight deviation in sound. Before I rebuilt the powersupply, there is a deep bass (seems to be nearing the lower limits of my hearing) audible, but after I changed the power supply, that deep bass has disappeared.

There was a change though. The previous power supply has 2 rectifier bridges. After which, each rail is filtered by 2 1800uF panasonic FC. (Total 4 1800uF FC on the power board). The current power supply is single rectifier bridge, has a virtual ground splitter and is filtered by only 1 1800uF panasonic FC per fail. (total 2 1800uF FC on the power board) The virtual ground is made by TLE2426 followed by BUF634. No resistors were used on the power board.

Resistors used are Holco 0.1% throughout. Capacitors are Panasonic FCs, with a 1uF stacked film capacitor across the +ve and -ve supply per channel (on signal board). 220uF panasonic FCs are present on the +ve and -ve rail of the signal board. There's no capacitors in the signal path.

Could the 1800uF missing from each rail be responsible for this deviation?

Thanks for reading, and Cheers!

All Op-Amps mentioned in my review are Jfet input.

Ahh.. I'll try them. Have all the OPAs there with me right now.

Thanks!

OPA2228/7

OPA637/627

OPA2107

 

AD8066/65

 

Check:

http://www.sgheadphones.net/index.php?showtopic=2628

Thanks for the recommendation.

Seems like only the AD8066 is a FET input opamp?

Cheers!

Some comments after the OPA2604 have burnt in further.

Sibilance problem set in soon after a few days of rolling to this op-amp. Initially I thought it was the problem of the LP i recently acquired, but after changing back to the OPA2134, the sibilance problem disappeared instantly!

Any other FET input op-amps to recommend?

Dreamie, will the same layout work with MC cartridge? Thanks.

This was designed for MM pickup, but RJM have another project, "VSPS ultra" which is for MC pickup.

This is based on the "VSPS" design by RJM.

dreamie, are you using moving coil or magnet pickup?

Thanks.

I'm using a MM cartridge.

Thank you digi01.

Have yet to try the 4556. Do not have much info on this IC too.. hehe... I chose OPA2604 to replace the original OPA2134 due to its FET input.

Currently using a SMPS computer powersupply, +12V and -12V. There's a powersupply in one of my project boxes which uses 2 shielded transformers, schottkey rectifiers and Matsush*ta 7812 and 7912 as regulator, but have yet to use it due to space constrains. (This amp's hidden between the turntable which is rested on a power amp and a TV. The SMPS is hidden behind the power amp.)

One interesting point though, even with absolutely NO shielding, there is very low noise, and I bet if there's any noise, it is from my tube preamp.

Cute phono amps !

 

Ever tried to roll the op-amp? Or still using the OPA2134?

Changed it to OPA2604. Still letting it burn in...

hi guys,

it's been a long time since i posted something. how's everyone?

this is a simple phono stage i made some time ago for the turntable.

this is the front view of the phono amp.

you can see the connectors here. 4 RCAs with a ground binding posts.

Power supply is outboard.

More info can be found here:

http://www.anzwers.org/free/wooters/projects/vspsphono.htm

enjoy spinning

(Jamiroquai - synkronized)

cheers!

CMF Dreamie???

wa.. breaky got CD deck...

Set it on fire?! =p .... haix... still need time to let it burn... no faster way

let your ipod play some fine music at low level volumes while u r asleep? hehe.. definitely will speed up the burn-in time...

let it burnnn

Wow! How much did it cost you? Is there only US plugs?

Thanks! CHeers!

My bro just passed me a Fisherman's Friends tin can, with chinese characters all over it. It is rather 'short'... about the height of a 9V battery lying down...

Have no idea how to fit the switches and 3.5mms into the tin can with the lid on...

i got phillips MKP for sale if you want some. very raved over cap by the taiwanese...

How much are they?

BTW, just rebuilt my CMOY. It's working now, but the volume is extremely low...

Using OPA627 directly soldered onto the board...

Hi guys!

Tried the above stated methods and the problem still persisted.

Have bypassed the capacitor and used a 0.1uF capacitor but this time it seems to only be worse. I hear a loud humming sound... there used to be music in the past.

Have decided to scrap the whole thing and rebuild another one. Any recommendations on cheap capacitors? Thanks in advance!

317 和 337.

Forgot to switch language mode after flaming at sgchinese?

Just read the article. (http://tangentsoft.net/audio/input-cap.html)

it seems to only talk about the use of the input cap. . It did mention about the corner freq. to be below 20Hz... I did a calculation...

1/(1*(pi)*(100000*(2*(6.8*10^-8))) = 23.40513869Hz

Could this be the problem?

I guess I will scrap the PIO caps for other applications. (A NON-portable preamp perhaps)

hmm... could you take a photo of board and post a copy of the version of the schematics you followed..?

I have no access to a digicam atm... sorry!

I followed the exact same schematic on Chu Moy's Portable Headphone Amplifier article posted on Headwize, only modification will be the absence of the switch (at the input) and changing the input cap value to 2*0.068uF.

I'm having problems closing the tin can. My PSU board wont fit.

It sounds like a MALFUNCTIONING RADIO WITH EXTREMELY BAD RECEPTION!!! Lots of static like sound...

............

Could it be because of the PIO? Old caps sound like old radio... 

More like a wrong connection (or lack of) or solder bridge somewhere.

Checked my connections and they are fine... Both channels have the same problem... and they are also wired the exact same way. (wired 1 channel at a time, not 1 component at a time)

haha.. gain problems i guess...

 

don`t dunk the PIOs... they are good caps...

I followed Cmoy's schematic exactly, except for the input cap.