DIY - Increasing number of inputs on vintage sets

I like using my vintage Quad 33-303 combo but was often frustrated by the need to disconnect-reconnect different sources due to the limited number of inputs on the 33 aka TAPE, DISC1 and DISC2.

Checking the internet, the total cost for proper input expansion boxes would be quite prohibitive since I would require a few such units for my numerous vintage sets.

I have a similar issue with speaker selector boxes .. for another post in the near future.

Then I came across the AV selector below and thought, why not try it?

Top view

View of the output RCA(s) to the amp, pre or processor

View of the possible input RCA(s)

Operation is simplicity itself. Connect the LEFT&RIGHT RCA(s) on the OUTPUT to your PRE or Integrated AMP. Then connect the desired Inputs to INPUT1/2/3 and use the selector accordingly.

An example is the below when deployed on my Quad 33-303 set.

Connecting various inputs to the Quad 33

Noise? Crossover "leakage"? Loud crackle when using the selector?

Been using it for a few weeks now and no sign of any undesirable issues or sounds yet ... you would not even suspect the AV selector was in-place unless you peered at the back of the set!

Revisiting the Marantz PM-45

Recently stumbled upon the service manual for the unit. Hence time for a revisit.

In the past I had recapped the unit by only swapping the capacitors with better quality equivalents spares (I had on hand) on the main amplifier board.

After reviewing the schematics, it was quite apparent the key area for improvement was the amplifier board - rest of the circuitry adhered to the K.I.S.S philosophy.

The following pix is for the amplifier section of the Marantz PM-45 from the previous post.

Amplifier section from previous post

There were differences in the amplifier section vs the schematics for my unit??? Maybe late production changes?

Top view after 2nd recap

Close-up of the recap area

Important signal path changes

In the last pix above, the red and yellow outlines indicate changes which are necessary for converting the PM45 into quite a decent unit!!

The yellow outlined items are the new changes introduced after the previous post. The yellow box on the RHS shows that the previous EPCOS replaced with WIMA equivalents. Previously the EPCOS replaced the original green poly(s). These poly caps were not present in the schematics of the service manual.

The yellow box on the LHS required better quality 10uF 50V EC - used Panasonic FC.

The red outlined items on the LHS originally had 470uF 6.3V but were 220uF 6.3V in the service manual. Cause for the extra warm sound. Hence I replaced them so with United Chemicon 220uF 6.3V.

The red outlined items on the RHS were as per previous post (Nichicon 100uF 16V). I added 153J poly bypass to them, to permit HF to pass thru.

The results were startling with the above changes.

Note: Other EC caps on the amplifier board need not be audiophile caps - any decent quality EC will do as they are not in the signal path.

DIY TDA1541A DAC with USB interface (***Update#3***)

Bought the following DIY TDA1541A DAC for a test drive as always been curious of the reproduction quality from such products.

DIY chasis with everything inside

Size comparison against a CD 

Rear view

Initial impressions of the purchase? 

The unit was sent via a double-box cocoon. Superb built quality with a solid feel.

Layout within chasis

Works fine once the necessary connectors were in-place. Source was the el-cheapo Samsung DVD ($39.90 from a local supermarket chain) via SP/DIF. Initially connected to my Accuphase and later to the Audiolab 8000A to see if there were any difference in the quality of reproduction with different amps in play (no difference). Meridian A500 speakers were deployed. 

Close-up of the stars

The DIY runs a little warm as the chasis is an enclosed box. Only the red LED is in-used eg indicate power availability, although another two LED(s) were available on the faceplate. Looking about the motherboard, many Chinese brand EC(s) were deployed. Very few EC(s) were ELNA Stargate and Panasonic FC.

Initial impressions from the DAC (straight out of box) reproduction was an off-pitch with a bias towards the HF. After a couple of days, the DAC began to sound right. A week later, I can't help but to BE IMPRESSED!!! 

Reproduction was good enough to give my Marantz CDA94 a run for the $$$. Of course the CDA94 wins  hands down since it has dedicated power supplies, dedicated clocking board, etc. But for the total cost ... you can't help but to be most impressed by the reproduction capability of the DIY! 

1JAN2015

Finally managed to obtained the Philips version of the opamp(s) to replace the TI 5534.

WHAT A DIFFERENCE!!! Vocals are now beautifully reproduced with realistic depth and detail!! 

8MAR2015

I added a Wima 0.022uF bypass to each of the output capacitors which are located just before the output RCA jacks. 

This was done to lift the super thin veil from the DIY TDA1541 reproduction. The effect of the bypass can be heard after about 30min of usage, resulting in a bigger HF headroom.  

Next change would be to replace the Chinese made caps with my preferred ...


27Mar2015

Finally replaced the Chinese made 2x330uF 16V at the output stage and the 10uF 50V from the input with Panasonic FC equivalents. Must say the Panasonic FC replacement(s) made quite an impression as the Chinese made caps tend to be produce flabby bass.

Chinese-made caps replaced

Philips BC 0.027uF bypass on the Panasonic FC 330uF 25V output caps

Panasonic FC caps added to the final output stage (next to RCA)

I used long leads on the bypass(s) as the board is mounted on shorter screws towards the back where the RCA(s) are. Otherwise would not be able to place the board onto the chassis.

Refurbishing a Quad 303 on behalf

Recently an acquintance requested for assistance to refurbish his 303.

Externally it was in near mint condition.

These are the pictures of it internals.

View of the components on the top of the chasis

PSU board

Original RCA transistors

Condition of the large caps - one leaked with another two on the way (orange dots forming)

Original condition of the internals below the chasis

Close-up of the driver board with EC spillage

After recap and upgrading

The PSU board was functioning properly despite the damp looking surface. No humming from the transformer or any additional spillover near the PSU board. The PSU board output voltage was a bit higher than expected ... maybe cause of the large caps leakage after many years? After rebiasing the output voltage was stable over the period the unit was with me.

Only cleanup was necessary on the driver board with the spillage as the components seem to be within specifications - surprisingly!!!

The original 2x2000uF caps for power were replaced by a single 10000uF 100V United Chemicon - more than adequate for the purpose (proposed by another European electronics company). The 2x2000uF 100V caps for supplying power for audio purposes were replaced by 2x10000uF 63V Rubycon with a bypass (on each) for bass extension.

The carbon resistor on each of the driver boards were replaced with a metal film. A ceramic cap was replaced with an equivalent value silver mica. The EC on the 303 boards was recapped as per my other 303 except the EC utilised in the this case, were ELNA Stargates. 

Sounds great after the aging components has been given a new lease of life - clarity with detail across the board. Bass reproduction is now tighter and sounds more realistic.

Do note the internal cabling tend to be brittle. Hence please handle them with care

Leak Stereo 30+ (Unit#1 - with speaker output modified)

Like Harold Leak's other transistor amp's, the Stereo 30+ was made to sound like a valve unit.

Front view

Only the speaker connectors were modified by the previous owner. Paint work on the unit gives away it's age. Neither effect the quality of reproduction in any manner or form.

Rear - modified speaker connectors

One PRO is the unit was optimised for PHONO as there are Gain selectors etc on the back of the unit. CON(s)? The RCA connectors on the back are quite close together.

Rated at 15W RMS per channel, it is quite grunty and was able to drive the Mission 753 properly via the QED Silver Anniversary speaker cables. Sounded dull using my usual copper cables. To the fans of the 753, it is well known to be quite a power hungry unit which requires a high current amp to obtain the best from it.

This little gem was made to high standards as the quality of the components are superb - still the original parts!!! Upon a glance, the internals look pretty alike that of the Delta 30. Inspecting the circuit diagram on the internet shows very minor differences.

The Stereo 30+ does shine when connected to easier to drive speakers eg the Meridian A500's. So much so a visitor who came to buy my Musical Fidelity X10D was mesmerised by it's quality of reproduction - he thought it was a tube amp. Quite a complement coming from a tube amp owner. Speaks volumes of the Stereo 30+!!

When doing a brief search on the internet, notice many of the Leak Stereo-series are popular in Europe for driving the high-end dual-concentric Tannoy's.

Mythos Audio Vaccum Tube Monoblok

A friend's friend bought this unit over for review.

Little or non-existant information was available on the internet. At the bottom of the monoblok, it is written German ...

The owner advises it was 15W RMS per channel, with output for 4/8ohms. Valves utilised are EL90 and what look like China tube version(s).

Power was provided from the external PSU unit to each of the monoblocks. 

Power on/off was silent - no thums.

The PSU was about 5kg and each monoblock about 3.5kg. 

PSU unit

When input is received, you see the green bars on one of the valves on the monoblocks - the bar appears from top and bottom at the same instance even-though volume was zero. This shows input was present.

Monobloks with volume control

PSU internals

Monoblok internal

The MKP(s) in the monoblock are a China made brand, Chi Da. And these monoblocks run HOT!

How do they sound?

Overall a pretty nice sounding unit. The HF was natural and fluid. Mid was very natural and well defined. Bass could be better but lack authority. 

Beautiful set for vocals.

And grunty enough to drive my DIY LS 3/5A with the DIY AB1 connected in-series, without braking a sweat!!!

Sansui AU-101

Just remember I used to own this little Junior many years ago.

Didn't take pix(s) of my gear then, so please refer to the following pix from the internet for reference. My unit was as clean as this pix from the internet. I remember the wooden sides looked very nice on the amp but was not solid wood (upon closer inspection).

Pix from internet

15W RMS per channel and a lightweight at about 6kg if you compare to the other Sansui's of the era.

Sold it as it didn't have the infamous Sansui grunt and had to regularly turn the volume to 11-1 o'clock before the volume was normal (compared to other amps) on my SL6S. Yes understand the SL6S was not a easy to drive bookshelve!

Reproduction was transparent and full of detail. Bass was not plentiful and had to leave the BASS knob at about 2 o'clock.

Con was the limited number of possible inputs.

The buyer used it as a bedroom set and advised the phono stage was superb - he used a Lenco L75 for source.

Mission 751

The following is a internet pix of the Mission 751. Sold mine many years ago and did not have any pix of it.

Pix from internet

Bought the 751 as could not resist the good deal for it. I remember the 751 was lighter than my main speakers at that time, the Celestion SL6S. The 751 was also slightly shorter than my SL6S, with the SL6S being just a tad wider. However the 751 was much deeper physically than the SL6S. Cabinet construction was solid.

I remembered my initial impressions of the 751's reproduction - initially sounded neither here nor there. After a few days, the 751 started to sound right. A couple of weeks later, the 751 reproduction was actually quite  decent. Only issue I had was the clarity of HF  - details were not forth coming as the SL6S ... probably due to the plastic dome protector on the tweeter as per the Mission 753.

Since I had the SL6S, I decided to let my go of my surplus and sold the 751 with the Pioneer A400, Pioneer F-225 and the Rotel RCD-965BX as a package to a friend.

JVC A-X2

Another of the integrated amps from my past.

Unfortunately no pix(s) of my A-X2... yes been quite a while since I had it. Hence please refer to the following links located via Googling for pix(s).

Front likeness
Specifications via Service Manual

The A-X2 has their Super-A circuitry and runs quite warm after 10min.

From memory the unit was quite grunty and was able to drive my SL6S without any issues. Reproduction was decent but with bias towards HF on the reproductions ...  found it to be a bit hard on my ears.

Discovered my unit to be quite sensitive to interconnect and speaker cabling, with a strong preference for the older version of the Monster Interlink-400 and thick copper cables for the speakers eg vintage QED black copper cables.

A common issue for the A-Xn (where n is a single digit numeric) series was the failure of a small capacitor in the power amp section. In my case, it was on the LHS.

Sold the unit a couple months after acquiring it (and repaired) since it was a bit hard on my ears.

DIY - Reinstating original green backlit after lamp replacement on Audiolabs

Been some time since replacing the original backlit lamps on my Audiolab(s). 

Must admit - I really missed the original green glow of backlit(s). Currently the available replacements does not produce the original green glow.

As I had open up the 8000CDM (awaiting replacement tray gear parts), decided to experiment with alternatives - drawing inspirations from my Sansui TU-9900 eg using a coloured filter of sorts. 

I decided to try using coloured drinking straws.

Sections of drinking straws for the experiment

After cutting them to a suitable length (and trimming the larger straw), I inserted the "candidate(s)" into the lamp holder areas to test, a set at a time - as per below.

With coloured straws inserted

Thickness of the thinner straws were simply too much for the lamps. Hence the results made the display hardly legible - must be within a meter???

Results from the larger straw were most pleasing but dimmer than the original. Definite improvement over the ugly yellow-ish alternative.

8000CDM display after adding filters

8000T display after adding filters

Will continue to search for a better alternative in the future ... until then, these will do just fine!

DIY - Tray gear replacement for Audiolab 8000CDM (VAM version)

After many years of service, the tray gear of my Audiolab 8000CDM (VAM version) gave way.

Initially I thought the belt driving the tray loosen after many years of service. Replacing it did not resolve the issue.

You could hear the motor after pressing the EJECT button but the tray does not budge. Upon closer inspection thru the CD tray opening, I could see the issue was caused by the non-rotating gear indicated by the RED arrow as the tray was not moving.

Offending gear without "teeth"

The next challenge was getting to it!!! Documentation on how to .. was not exactly widely available.

After much mucking around and researching numerous other posts, I noticed similarities on the Audiolab since it does use a Philips VAM assembly.

This is the procedure for removing the tray from the assembly - No other removal necessary.

Please remove power cable before beginning

1) Remove the metal cover and gently extended the tray to the maximum

2) Then use a screwdriver or similar tool to press the tab at the opening indicated by the beige arrow

3) Now gently slide the tray out from the assembly - in the direction indicated by the larger green arrow

How to remove tray after normally extended (to maximum)

You will now see a removable cover above the gear, towards the front of the CD tray assembly - gently release the tab and pull up to expose the tray gears. You can now remove the rubber band and the gears - see items below.

1st gear from LHS is the "toothless" one

Leaving the following behind.

Top view

Front view

Where to get a replacement?

Am ordering a full replacement set (2 gear and the rubber band). Will update once I have receive the parts.

Am deploying the Samsung C370 as backup transport until the 8000CDM can be repaired. Must say am surprised by it's performance so far!!!

17Mar2014

Received the 3 replacement parts from an agent in China.

Luckily I ordered additional belts as the item which was packaged with the gears was a little larger!

The good old reliable is back on-duty again