Big Bill
Summertime Rolls.....
They are indeed the 470 ohm resistors that you spec'ed.
Here It Is: The All Singing All Dancing HTMCPS
- Thread starter HypnoToad
- Start date
They are indeed the 470 ohm resistors that you spec'ed.
Just made me wonder why when the design is unchanged and gain is a little lower, why people are suddenly having problems with noise and too much gain.
I was worried that people had put 47 ohm resistors where the 470 ohms should be.
I wonder if the op amps are different now, mine are exactly the same as the new versions and both have the right gain and no noise at all.
Big Bill
Summertime Rolls.....
None at all? At any volume setting?
Big Bill
Summertime Rolls.....
Success!
All right, just got home and plugged her in. The reduction from 86 to 58 Ohms (R2/R10) did the trick! :yes: I now get no higher noise floor from the HTMCPS than I did with my SUT running in to my Hagerman Bugle.
I'll report back with my listening impressions in a little bit.....
All right, just got home and plugged her in. The reduction from 86 to 58 Ohms (R2/R10) did the trick! :yes: I now get no higher noise floor from the HTMCPS than I did with my SUT running in to my Hagerman Bugle.
I'll report back with my listening impressions in a little bit.....
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Only if I put my ear up against the speakers but it's the same amount of noise as if I just have my preamp plugged in and turned all the way up.
I'm glad the lower value resistors did the trick.
The idea of using trimmers will take care of this as you can adjust the gain on the fly.
GreatTone
Super Member
Maybe I should try lower resistor values for R2/10. Right now, I have 300 ohms for a 0.3mV AT-33EV. When I had the 2.5mV SAE 1000e in there (also with 300 ohms) it was dead quiet at full volume. Now there is a modest amount of white noise as I said, but not intrusive. I'm not sure how quiet a LOMC can ultimately be.
Big Bill
Summertime Rolls.....
It's certainly worth a shot.
IMHO The gain should be such that at your regular listening levels the volume control should be at around 12.00 oclock, YMMV.
GreatTone
Super Member
Yeah, right now with the HTMCPS it's a bit higher than that. Normally on other inputs full listening volume (as loud as I like it) is about 12 o'clock. Now it's more like a bit under 1. Not too much difference, but if I lowered the gain by decreasing R2/10, wouldn't I have to turn it up even more?
I'm not unhappy with the noise now -- it's not audible during listening at any volume. It's about like my tube stage was before, only no hum. But when I had the 2.5mV 1000e, the HTMCPS was dead silent even turned all the way up. But maybe I'm expecting too much from a LOMC (this AT33EV is my first).
As long as the noise floor is significantly lower than the background noise of the record that's all you need.
My modded 640P's were very low noise but the HTMCPS is a lot lower than those.
Different carts, op amps, wiring, locations, speakers, ancillary equipment all affect noise.
How loud would the music be in comparison to the noise with the volume control all the way up, very loud I imagine.
My modded 640P's were very low noise but the HTMCPS is a lot lower than those.
Different carts, op amps, wiring, locations, speakers, ancillary equipment all affect noise.
How loud would the music be in comparison to the noise with the volume control all the way up, very loud I imagine.
GreatTone
Super Member
Yes, fortunately I normally listen to my stereo with music playing, and not just with the volume control turned way up and nothing else on. :yes:
I think most folks do.:thmbsp:
It's like the often made statement that when I turn it all the way up and put my ear against the speaker..................
shelly_d
Not An Audiophool
I think most folks do.:thmbsp:
It's like the often made statement that when I turn it all the way up and put my ear against the speaker..................
I go deaf when the kid drops the needle on the tonearm!
Shelly_D
dodog
Addicted Member
What does this phono pre sound like with John Cage's 4′33″ playing?
http://en.wikipedia.org/wiki/4′33″
http://en.wikipedia.org/wiki/4′33″
Obankenobi
Hypnotoaded
OK, I want in. Narrowly avoided destroying my 640P with ham-fisted soldering, the upside is that a guy raised on cassettes and CD's is truly enjoying vinyl for the first time thanks to Hypnotoad's thread on modding the Cambridge Audio phono stage. Only complaint I have is that, even with the 3 dB gain resistor swap, I also get moderate background noise and low output compared to CD's with my Denon DL-103D. Could I get a PM for info on ordering the PC board, and leads on cases others have used for this phono stage?
Qwin
Active Member
Build Update
My components arived from the States quite quickly (Mouser).
The only parts I purchased here in the UK were the Takman metal film resistors and the terminal blocks for cartridge matching resistors.
Took about an hour to solder it all in place, see picture below.
Can't find a case anywhere. (5"wide x 3"high x 11"deep) as per my intended layout on the second picture. Think I will have to make a case. Its a while since I did any sheet metal folding so will take my time.
The 8.2K resistor works great for the 12v LED when put accross my total of 24v. Not so bright as to anoy but easy to see. Thanks HypnoToad :thmbsp:
My components arived from the States quite quickly (Mouser).
The only parts I purchased here in the UK were the Takman metal film resistors and the terminal blocks for cartridge matching resistors.
Took about an hour to solder it all in place, see picture below.
Can't find a case anywhere. (5"wide x 3"high x 11"deep) as per my intended layout on the second picture. Think I will have to make a case. Its a while since I did any sheet metal folding so will take my time.
The 8.2K resistor works great for the 12v LED when put accross my total of 24v. Not so bright as to anoy but easy to see. Thanks HypnoToad :thmbsp:
Attachments
Obankenobi
Hypnotoaded
My bits are starting to arrive, yes! But Mouser says these terminal blocks have been discontinued: 737-EBC-02-E Fixed Terminal Blocks 2P 7mm Pitch 8.3mm HT STRGHT PCB MOUNT.
Can't seem to find a close cousin on Mouser, would this unit from Digikey look like it would work?
http://www.digikey.com/product-detail/en/OSTTE021104/ED2748-ND/2351824
Can't seem to find a close cousin on Mouser, would this unit from Digikey look like it would work?
http://www.digikey.com/product-detail/en/OSTTE021104/ED2748-ND/2351824
If you look on the PCB the part numbers for Digikey are on them:
ED1534-ND for the 2 pin
ED1535-ND for the 3 pin
Hope this helps.
Qwin
Active Member
Obankenobi - If it helps everyone, 7mm is not a standard meteric spacing. the standards are 3.5mm & 5mm. The supplyer has used a 3.5mm three way, taken out the centre contact and then called it a 7mm two way.
This is what I have done, the blue blocks in the picture above (post 276) I made this way. There are lots of supliers of low profile blocks with 3.5mm spacing.
They also do this with 5mm spacing and make up 10's this way.
Hope this helps folks, I was strugling to find 7mm spacing and I live in metric Europe, till I realized what they had done.
Edit - If you want a 7mm three way, buy a 3.5mm five way and take out positions 2 and 4.
This is what I have done, the blue blocks in the picture above (post 276) I made this way. There are lots of supliers of low profile blocks with 3.5mm spacing.
They also do this with 5mm spacing and make up 10's this way.
Hope this helps folks, I was strugling to find 7mm spacing and I live in metric Europe, till I realized what they had done.
Edit - If you want a 7mm three way, buy a 3.5mm five way and take out positions 2 and 4.
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Obankenobi
Hypnotoaded
...and now I see the Digikey part numbers you've provided right at the bottom of the BOM- the part I was disregarding first time 'round (face in palm).