Obsession with Digital-to-Analogue (DAC) converters?

A friend recently asked why do I prefer using DAC(s), to using a dedicated player as I seem to have gained a few el-cheapo DVD players as transport? My friend still uses a vintage Marantz CD-72.

The summarised the PRO and CON(s) after a long discussion are:-

PRO

- Using a DAC, your favourite sonic signature will be preserved

- Not necessary to use a expensive and/or hard to repair player to act as transport

- Unlikely to break down often as a DAC does not have many physical moving parts

- Can replace the transport with a decent DVD player that's pretty affordable nowadays since DVD players are no longer the flagship players

- Can be part of a AV setup as long as your Audio-Video equipment has a SPF/DIF output eg android box, streamer etc

- Much improved audio presentation as a DAC hifi component has been optimised for the sole purpose of production of audio only eg best example is the Marantz CD-94 being enhanced with CDA-94

CON

- When your favourite CD/DVD/transport dies, the cost for repair and/or replacement will be expensive

-  May not be able to rescue the player due to way most companies operate today eg stock min parts

-  Need to evaluate many players before you can find a satisfactory audio quality compromise (if not repairable)

I look at it is a way to "future proofing" my setup and preserving the preferred audio signature.

Another low cost DIY tube buffer kit (***Update#2***)

Bought a different version of the low cost DIY tube buffer kit to try.

The new toy uses two  Chinese 6J3 tubes, with option of US made 5654W(s). My initial purchase was with the default Chinese made 6J3.

The main PRO for this 2nd DIY set is more space around the capacitors in the audio critical path eg the yellow poly(s), permitting a much larger variety of potential substitution choices.

Initial kit purchased

Similar layout to the previous kit but with more space for swapping the critical capacitors

Uses non-mainstream EC capacitors on the PCB

The default 6J3 purchased with the kit

Assembled kit in-action 

This new kit has the same power requirements and input-output layout(s). However, the output volume for the new kit is much lower than the previous. The potentiometer output is even at low volumes and cames with a volume knob which also functions as a power-on/off switch. To enable more space on roughly the same footprint, the new kit uses SMD resistors which were pre-soldered onto the PCB.

How does it sound?

Best way to describe is as if someone enabled a "tonal normaliser" on the output😬.

When I contacted the seller, they assured using the US made 5654W would make a "night & day" difference. Many online reviews does mention the US made 5654W(s) are worth the upgrade. Thus I placed an order for a pair since these did not cost an arm or leg!

Will update next month once I received the 5654W(s) and give them a spin.

1Nov2019

6J3 (LHS) vs 5654W (RHS)

Been using the buffer kit with the newly installed 5654W(s) for past few days and can confirm they do produce a remarkable improvement over the 6J3(s). Received the 5654W(s) quite a bit later than usual and suspect that is due to the decrease in the number of shipments from PRC with the on-going trade-war between the two big economies. 

Thus did not have the opportunity to run-in the 5654W(s) properly before this update. At the moment I can safely say that the "tonal normalisation" has been removed. The DIY kit is beginning to sound like a proper tube component.

Will allow the 5654W(s) to settle in before deciding if to start substituting the capacitors in the critical path.

Late September 2022

Pix after "upgrade"

Was considering changing the default yellow 1uF as the sonic reproduction was pretty good but could be better.

Hence did not wish to waste proper quality capacitors for a "Proof-Of-Concept" evaluation.

Found a few of the 2.2uF poly(s) which was removed from other units, since it has long leads, was suitable as a candidate#1.

Will leave it for the moment for further listening, and, swap out with others for further evaluation.

To be update iagain n the future.

Low cost DIY tube pre-amp / buffer kit

While trawling the PRC eBay, I came across a low cost DIY tube pre-amp kit which was advertised as a possible tube buffer as well. Definitely easier and cheaper than try to procure a X10-D from the used market, as those goes quite quickly once listed.

The completed DIY unit mounted using magnetic feets on top of a cheap DVD player

Received the DIY kit with all parts as per advertised which does not include the 12VAC 0.8-1A power adapter, potentiometer knob, mounting feet nor the plastic casing.

The good news is the PCB is well adorned with marking of component position and values. And the potentiometer has a built-in ON/OFF switch.

Bad news is the PCB is extremely compact, with most of the critical components located very close to the others. Would help if you used a soldering iron with a fine or small tip.

Close-up of the DIY kit; 2 of the audio path critcal capacitor on top with the other 2 on the bottom side of the PCB (not visible)

One minor minus point is that the potentiometer does not came with a knob and volume at the lowest setting was not balanced. Hence once switch on, you need to turn the volume up slowly until you could hear a balance volume on both LHS & RHS speakers.

Another minor minus point is that there were no labelling for the INPUT and OUTPUT terminals on the PCB or the optional casing. It's only stated on the instruction sheet (provided in Chinese), with schematic of the PCB. The design uses the X10-D methodology for doubling the input voltage but implemented for a lower cost 7-pin valve instead.

The major minus point is the location and available space for the 4 critical capacitors on the audio path - 2 for input and 2 for output. Due to the severe space restrictions, your choice of capacitors are severely limited by physical size, lead length and available values (if you wish to keep everything on the PCB). In addition, the compact PCB makes swapping capacitors a "pain in the neck".

How does the default kit sound when used as a tube buffer?

Reproduction is surprisingly clear with good details BUT with a heavy HF bias. The default Chinese 6J1 provided seem to be adequate for the moment.

Am still performing substitutions and listening to the new components (once they have settled) on the audio critical paths. Once done, will then decide if the supplied Chinese 6J1 x 2 should be swap out.

Post to be updated at a later date.

DIY - possible simple solution for deteriorating sound from the channel of a Leak integrated amp

Recently I had an inclination to go listen to my Leak Stereo 30Plus setup in the spare room.

When I switch the unit on, the LHS works fine. The RHS channel let out a few muffled grumbling sounds before turning silent. Repeating the procedure produced the same results. I then tried various settings on the balance control as well as turning the volume up and down. There were extremely low squeaks from the RHS output.

Thus I suspect the issue was similar to that of my Quad 33 (post in the past) - due to oxidation of the contact points on one of the boards of the Leak. The internal setup of the integrated Leaks (Stereo series and Delta series) are all similar.

Please power off the unit and disconnect the power before proceeding any further.

General layout of the integrated Leak amplifiers, with the L&R boards on the LHS of the unit

Since my unit had issues with only the RHS channel, I concentrated on the two boards with "R" on the top of the grey plastic bar. To access the boards, you need to gently lift the plastic bar (which is held down by a gentle spring).

I pulled only the "R" boards from the motherboard and sprayed a little contact cleaner into the board cradle of the motherboard. Then returned the boards to their cradle and return the grey plastic strip onto it's grooves - the way I found them.

Left the unit alone for about 30min or so before restoring all the connections ... all's well again!😄

So before you head out to visit the repair shop for a similar issue, give the above a go 1st.😉

Revisiting Marantz CDA-94 - Transformer failed (again)

A couple of months ago, I was enjoying the pleasant results from the CDA-94 when the front display suddenly went dark and there was no longer any music from the hifi set.

I powered off the unit, disconnected the power line (VERY IMPORTANT) and checked the unit's main fuse with a multimeter eg F001 - it was fine. Was puzzled. Hence I reconnected everything and tried to use the DAC again. Still "dead in the water", I repeated the previous check and discovered F001 blew this time. F001 is supposed to be 250V 200mA but had been previously replaced with a 250V 500mA since the 200mA fuses are pretty hard to came by (where I am).

Next I proceeded to check all the fuses on the various PCB(s) with the multimeter; all the existing fuses were fine. Hence suspect a shorted transformer, most probably L001 again since it had been replaced long ago and another visitor on my previous post informing of the same issue. Since I had some spare 500mA fuses handy, I could replace F001 but this time, remove the power to L001 before performing the power-on test. Bingo! The unit could be power-up without L001.

First a recap. When L001 was replaced years ago I did not have access to the Marantz CDA-94 service manual (courtesy of HiFiEngine) and thus did not know how to proceed as there was no information on L001 as there were no markings on the bloody thing!! A retired repair techie from DIYAUDIO advised to use a lower spec transformer instead. Hence I purchased a 12V 133mA toroid with dual secondary(s) from Element14. In those days there were not many choices and you had to pay thru your nose for the part (since they charged for courier delivery if you did not meet the minimum purchase sum). Since the replacement transformer had dual secondary(s), the kind DIYAUDIO techie provided guidance on how to connect the new dual secondary transformer (the original transformer had 3-cables, the replacement came with 4-cables). I have since learnt that the replacement transformer with dual secondary(s) was connected using the center tap technique. 

Fast forward to the present - was checking the internet for replacement recently ... boy has times changed! You would be overwhelmed by the available choices and surprised by how much prices has lowered!!!

Previously would have loved to install a Talema 7XXXX-series replacement but the cost was prohibitive then since the local agent had minimum purchase requirement(s) etc etc while eBay shipping from overseas was quite expensive. Nowadays it's possible to procure the OEM equivalent for a pretty decent price. 

While trawling the net for information, came across a translated site informing all the transformers used in the CDA-94 were with 1A output. 

Hence settled on the 15W version with 15Vx2 secondary(s) and 500mA output per secondary and the matching mounting PCB - see pix(s) below and additional information on the respective caption(s).

L001 replaced with the blue OEM transformer

Replacement transformer on mounting PCB attached to chassis bracket using plastic screw with additional washer between PCB and the chassis mounting bracket

Close-up of the replacement transformer and cabling

"Center tap" technique hookup at terminator end; fuses after the termination point upgraded from 500mA to 750mA

Please note the cabling used for the replacement transformer were salvaged from it's dead Noratel predecessor.

The CDA-94 back in business again ... now considering procurement of  some heatsinks for the opamps, TDA1541A and the SAA7220 chips.

Add-on heatsinks for Audiolab 8000A

I usually rotate the amp in-use (in the hall) every once in a while. Currently it's the last series of UK made Audiolab 8000A with 'F' in the serial number.

The external casing of the 8000A was running quite warm in the local tropical weather. Hence I search for suitably large piece of heatsink to assist with heat dissipation - inspired by the design of the casing on my long ago Musical Fidelity X1A.

After checking a number of websites, I had to give up my initial idea of acquiring a single largish  heatsink. Discovered that could became a rather costly exercise, with possibly pricey postage too!

About a week later, I came across a PRC website which had some attractive looking heatsinks on offer but these were smaller than what I had in-mind. Then the idea hit me - I could arrange several of these smaller heatsink(s) in such a manner that they could assist with heat dissipation from the critical areas of the 8000A, as if a single large piece of heatsink was deployed.

Each heatsink is anodized aluminium and measuring 150mm x 70mm x 11mm. Used 6 of these heatsinks and arranged them (as per pix) with a spacing of 1-3mm between them. As most of the heat on the external casing were from the LHS of the 8000A, I arranged the heatsinks on the LHS closer to it's neighbour vs those on the RHS.

8000A with several add-on heatsinks

Aesthetically pleasing too, no complaints from the boss ... yet😁

Minor maintenance of a Quad 33 (on behalf)

Was assisting a friends' friend with minor maintenance on his Quad 33.

Sounds ok initially after power-up but takes about 25-35min before sounding right.

Hence only replaced the two main EC on the PSU and a few of the older poly(s) on the DISC board (see pix below). Used an older generation of poly(s) for the DISC board, to maintain the sonic charm as much as possible.

Sound surprising decent with clearity once more.

They don't make them like they used to these days - not put together with "love and tender loving care" these days, just mass production for the sake of profits.

Initial testing after minor maintainence

New EC caps on the PSU

"Newer" poly(s) on the DISC board

Alternate analogue FM reception for the living room (***Update#2a***)

First a background of the change in the existing setup.

In Singapore, most of the population (>90%) live in a Housing Development Board (HDB) flat aka government flat. Traditionally there would be standard antenna access points for FM and TV in every unit which are clearly marked in the living room. These antenna access point were supposed to be connected to the antenna at the top of every HDB building.

Traditional FM & TV antenna connector in HDB flats

On the Sunday morning of 6Jan2019, all I was able to hear was static from the FM radio via the access point marked FM in the living room.

When I contacted the authorities the next working day, I was informed the reported service disruption in my apartment was due to the withdrawal of all cable services by the telco Starhub. Only catch was I did not subscribing to any services from Starhub at the present time.

Hence when I visited several electronics DIY shops in the Sim Lim Tower and Sim Lim Square area, the shops informed many experience the same issue as myself. Thus indoor FM antennas and boosters😵 were flying off the shelves!

Prices were better online and I ordered a set. While awaiting the delivery, I had to use a DIY FM antenna - basically just hookup a 3m cable to the antenna socket of my Kenwood KT-5020. It's doing a decent job for the station I wanted to listen to but did not fare well for distant stations.

The order is scheduled to be delivered tonight. Will update once I have time to setup the item(s). For non-Asian visitors, this is a very busy period in the Far East as it's Chinese New Year week eg our version of Christmas😄!

Apologies for the delay for this month's post😞


Update (11Feb2019)

I purchased the following package online which includes a signal amplifier and a "multi-purpose antenna" (according to the seller's website). The signal amplifier provides 20dB boost and is powered using a typical USB phone charger - great for making reception possible in "poor areas".

Signal amplifier and "multi-purpose" antenna purchased online

Assembly of the components is "easy as 1--2-3" and all that was required was a USB charger.

Unfortunately the new components did not deliver a complete solution. Signal strength on the tuner is full but no stereo light on the tuner.

Hence I bought the indoor antenna originally recommended by a number of stores, the Daiyo EU-1703.




I then proceeded to test various combinations to determine which would provide the best reception - DIY antenna (with/out signal booster), digital antenna  (with/out signal booster), and Daiyo antenna  (with/out signal booster).

Best combination seem to be pairing the signal booster with the Daiyo antenna. Not the perfect solution as was able to receive most of the available stations with high signal strength, and,  about 90%+ in stereo.

Luckily my favourite stations were not among the low number of casualties😀


Update#2 (23Mar2019)


This diagram explains why I can no longer use the traditional designated FM and TV ports in my apartment. Starhub was using them (aka SCV port in the pix) as their "new transfer facility". Don't the residents get any say about this?

JVC XL-MV33 (Part-2)

Continuation from JVC XL-MV33


My skeptical friend finally decided to get his toes wet with minor recapping on the MV33 to improve reproduction.

Upon reviewing the PCB with the output RCA connectors ... I found some typical Japanese poly capacitors encase in a yellow plastic casing. These type of poly capacitors were common in Japanese brand products from the 1980-1990's (see my past article on them) and are most likely the culprits of the audio reproduction barrier - not all need to be swap out unless they are in the audio pathways.

Original output PCB

Part of output schematic for MV33 audio reproduction

The MV33 schematic from HifiEngine confirms only the ELNA EC (47uF 50V) and the yellow encased poly (1500pF) are on the audio pathway between the JRC OPAMP and the RCA outputs. The 220pF capacitors on the schematics were not present on the PCB - replaced by resistors.

As my skeptical friend was unconvinced of how much improvement can be obtained, I proposed initially changing only the two poly capacitors on the audio pathway (1500pF) - should be quite a revelation for him. Used a pair of BC (aka Philips) 1500pF poly for the swap-out. 

ELNA EC and the Japanese poly swapped out

For the first 30mins after the swap, voices were high pitched with the rest of the material sounding a little off-pitch. Thereafter the reproduction was much improved with the HF(s) sounding more natural and precise.

Even so, the overall presentation seem incomplete ... as if there was still some fog in the area. Next the ELNA EC(s) were replaced with audiophile grade Nichicon MUSE and a bypass ... the presentation improved quite a lot - reproduction was now much cleaner and begin to sound more like a decent CD player.

PCB after capacitor swap-outs

As my friend was not adventurous, we did not proceed any further. He wanted to enjoy the new improvements for the time being.