Have your say & ask the experts

I've decided to take the plunge and have a go at modifying (modding) my Beresford DAC. There's a few threads out there that cover this......but I hope to produce a blow by blow guide for the electronics amateur (such as myself).

---

Inside the box


Beresford TC-7510 DAC Internals

This next bit is my interpretation of the internals and could be cobblers, so take it with a pinch of salt.

The board at the back is the DAC itself. On the very left are a couple of big capacitors which form part of the DC power input stage. Then there is the signal output stage which amplifies the analogue signal for the variable and fixed outputs. To the right of signal output stage are the actual DAC components.

The board at the front contains the bulk of the DC power input stage components (left), power switch, input selection, headphone amplifier and volume pot for controlling the headphone amp volume and the variable signal output.


Beresford TC-7510 DAC Output Stage



Beresford TC-7510 DAC Output Stage - closer

In the middle of the signal output stage you can see the surface mounted opamp (JRC4558) surrounded by surfaced mounted resistors and capacitors, radial electrolytic capacitors and, what look to me to be, a couple of ceramic capacitors (CC1 & CC2).

---

The Modifications

The first modifications (mods) I'm going to perform have the support of the designer. Stanley has produced a couple of .pdf files to document these mods and has discussed them on another forum. These mods are called Mod 21 and Mod 21 Pt 2. These mods focus on changes to the signal output stage.

However, if I do any other tweaks to the DAC, I'll use this thread to document them. Clearly, I'd be interested to read about the mods other people have performed and would encourage them to use this thread as well to keep them all in the same place.

---

Mod 21


Mod 21

Refering to the photo above, this mod removes the resistors at R11 and R14 and replaces them with a solder bridge and replaces the four identified electrolytic capacitors with 47uF / 16V rated versions.

The solder bridge is effectively free. I have ordered the four capacitors from Audio Upgrades and have gone for these.


4 x Rubycon ZA 16V 47uF. Cost = £7.60.

On the face of it this mod should be fairly easy to do and doesn't really give me any cause for concern.

The pdf by Stanley is available here.

---

Mod 21 Pt 2


Mod 21 Pt 2

Refering to the photo above, this mod replaces the JRC4558 opamp with a National Semiconductors LM4562MA opamp and replaces the decoupling capacitors at C5 and C6 with a couple of WIMA 220pF/100v polypropolene capacitors.

I have ordered the replacement opamp from Audio Upgrades which can be found here. I'll get the WIMA caps from Maplins which can be found here.


1 x LM4562MA Opamp. Cost = £5.49


2 x WIMA 220pF/100v. Cost = £0.30p

This mod is a different league to the first with the potential to brick the DAC. Removing the old opamp will be difficult enough. Soldering the new one in will be just as hard...maybe more so. I'm a bit worried about this one. Still, nothing ventured....

The pdf by Stanley is available here.

---

I'll update the thread as and when the components arrive and the work progresses. Now, where was I with that headphone amp thread....?

PJPro:

I've decided to take the plunge and have a go at modifying (modding) my Beresford DAC. There's a few threads out there that cover this......but I hope to produce a blow by blow guide for the electronics amateur (such as myself).

I'll update the thread as and when the components arrive and the work progresses. Now, where was I with that headphone amp thread....?

Cool...will be keeping my on this thread and awaiting your impression's on the mod's!Keep up the good work

This is so far over my head it is stratospheric, but again, great photos and very interesting.

Nice to see you getting the soldering iron out, think you will be pleased with the improvements.

However I would have gone for the Elna Silmic II (RFS Series) Electrolytic Capacitors instead of the Rubycon ZA's @£1.53 + vat each.
Here's a link
www.hificollective.co.uk/components/elna_capacitors.html

trevor79:

Nice to see you getting the soldering iron out, think you will be pleased with the improvements.

Trevor, have you done these mods already? If so, how did it go? Was it difficult?

trevor79:

However I would have gone for the Elna Silmic II (RFS Series) Electrolytic Capacitors instead of the Rubycon ZA's @£1.53 + vat each.
Here's a link
www.hificollective.co.uk/components/elna_capacitors.html

Hhhmm. Perhaps I should have posted my intentions before buying the caps and requested advice on which to get. Oh well, I've ordered them now.

Hi there

 Just wondering what improvements these mods will make.  Obviously for the better but do you have any idea how it will effect the sound?  I should have paid more attention to my lecturer in college!   

PJPro:

trevor79:

Nice to see you getting the soldering iron out, think you will be pleased with the improvements.

Trevor, have you done these mods already? If so, how did it go? Was it difficult?

trevor79:

However I would have gone for the Elna Silmic II (RFS Series) Electrolytic Capacitors instead of the Rubycon ZA's @£1.53 + vat each.
Here's a link
www.hificollective.co.uk/components/elna_capacitors.html

Hhhmm. Perhaps I should have posted my intentions before buying the caps and requested advice on which to get. Oh well, I've ordered them now.

No I haven't modded one, but I do know my components. The mods are straight forward enough, a steady hand, cup of tea and a digestive!

My stuff is a little higher up the food chain so use more expensive components, ie Oscons for decoupling caps.

The components have landed.

TitusG:

Just wondering what improvements these mods will make.  Obviously for the better but do you have any idea how it will effect the sound?  

Take a look at this article by Tangent.

TitusG:

I should have paid more attention to my lecturer in college!   

I don't profess to have any great knowledge of electronics. I'm half competent at soldering and can follow instructions. However, I am learning....

Thought I'd take a look at the replacement opamp.


LM4562MA

Errrr. It's a lot smaller than I was expecting. A lot, lot smaller! Doesn't bode well for the upgrade. My soldering iron tip will cover two legs at once!

Hmmmmmm. Maybe it just looks smaller off the board?

Good luck PJ.

Boy, am I glad I got the TC-7520 with it's 2 handy DIP-8 sockets!

All I had to do was make sure the LM4562NA's were the right way round before I pushed them in. (And they are bigger than your SOIC versions.)

 

 

 

I did a bit of preparation for these mods today by having another look at a couple of tutorials by Tangent. These were "Surface Mount Soldering Techniques" and "How to Desolder Electronic Parts". There are actually 15 tutorials in total from Tangent available here. All take the form of videos.

I also went out and bought a soldering iron from Maplins with a much finer tip. I got this one.....only to find out later from another of Tangent's tutorials that it might be a little under powered. Damn! Oh, well. I'll see how it goes.


12W Miniature Soldering Iron

I do intend to complete the mods.......just been a little busy lately. Hopefully, I get round to it next weekend.

Watch this space!

I've completed Mod 21 parts 1 and 2. I'll do the write up later this week. Sneak preview? Sweet!