Upgrades to Graham Slee "The Bridge"

[freddypipsqueek]

A few months ago I picked up a new Cyrus amp and a Graham Slee Gram Amp (The Bridge) phono preamp. My Cyrus 1 was on the way out but after a bit of TLC (new sockets, alps blue velvet and replacement of the input selector) I got it working again. I forgot about the Gramamp until last night when I dug it out and read the following review.

www.tnt-audio.com/ampli/gram-preamps_e.html

The review seems to suggest that changing the capacitor for Polypropylene ones is the main difference between the Gramamp 1 & 2.

Below are some photos of the inside.






I have identified the following,

The voltage regulator is an 7818CT.
The light blue capacitor near the regulator is marked 220u-M 35v.
The large blue capacitor in the centre is marked 470uF 16v.
The smaller blue capacitors are marked 47uF 16v.

Assuming I will pick the bits up from HiFi collective (http://www.hificollective.co.uk/) I would really appreciate some upgrade hints particularly on replacing the capacitors. I am getting quite comfortable replacing bits but really would appreciate some ideas.

I have also bought the following (an OPA627 dual on an adaptor).
www.ebay.co.uk/itm/250920737187?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I understand that I could use this to replace the NE5532AN opamp. Does this sound like a good idea ?.

[PinkFloyd]

The voltage regulator is an 7818CT.The light blue capacitor near the regulator is marked 220u-M 35v.The large blue capacitor in the centre is marked 470uF 16v.The smaller blue capacitors are marked 47uF 1

The blue caps are Panasonic general purpose types. The light one is BC components.... not bad caps. The OPA627 on Brown dog will be a good drop in replacement for the NE5532, the OPA2134 is also pretty good. The max voltage of both 627 and 2134 is +/- 18V so you may want to change the regulator to a 7815 (the 24V Slee PSU will be perfect with the 7815).... Frans may have more info on this.

[freddypipsqueek]

Mike.

Thanks.

I have the wallwart 24v supply.

Is this worth a Pinkie ?.

[Deleted]

Seems like a pretty dated design to me.
I feel sure that Frans could do a helluva lot better than that very basic design.
Alex

[PinkFloyd]

Is this worth a Pinkie?

I don't really know anything about them Freddy, I sold my turntable when CD came out back in the 80's. Try swapping the opamp and see how it sounds... what are you trying to achieve? ie: where do you find it lacking?

[freddypipsqueek]

Not an easy question to answer !!.

I have a lot of old LP's. say 400 or so. When we moved I put them all in a few boxes and moved onto CD's and (boring because I was into computers when it was nerdy) computer audio etc.

In the last year or so I've started to play them and I don't want to give this up when I change the amp.

Where is it lacking. There is no doubt it lacks the soundstage and resolution of CD and I suppose I'm trying to improve these aspects. What my turntable does though is "get up and go". I have alot of Mozart on vinyl and its great to listen to whilst I'm working; it has energy off an LP which I don't get off CD.

Also, you guys are very clever. This phono amp is something I think I can just about get my head around and improve. Its a bit of a starting block for me. If I can change some of the capacitors and the opamps and PSU and get a feeling what going on then its a good learning curve. I need that. Does that make sense ??

[freddypipsqueek]

Sorry if this sounds like a basic question but if I put in one of these (15v) with the OPA627 would that be worthwhile with the standard wallwart ?

www.paulhynesdesign.com/page6.html

[freddypipsqueek]

Ended up getting an “ebay” regulator to drop the voltage to 18.5v DC and then a Paul Hynes 15v regulator. Dropped the OPA627 in and its working fine.



Any other ideas gratefully received.

[leo]

I'd just try the reg upgrade to start with and see what it sounds like using the stock op-amp. I'd then try removing the lytic cap which was on the output of the stock regulator (one on the third pin), I think the PH series reg has an output cap already onboard, keep the local ceramic decoupling cap for the phono stage op-amp.

BTW if the PH series reg allows it with an onboard trimmer I'd adjust it from 15v to 18v and up the main PSU so to keep the voltages the phono circuit was designed for.

[freddypipsqueek]

Thanks Leo. the PH does have an onboard trimmer. PH recommended the 15v unit to go with the OPA. I'll have a play over the holiday. Thanks again and have a good Christmas.

[leo]

No probs, Just remember its a single rail on that circuit rather than +/-v so you get just the 15v rather than 30v from +/-15v