Cambridge Audio A1 - which audible sonic difference between all Versions ??

[tiefbassuebertr]

I have heard, that there are at least three different versions - the last both with chip amp (monolithic IC's); MK-II with TDA1514/TDA1514A and mk3 with LM3875.
The MK-I version is a so called "original version" according several posts, developed from Michael Creek (or X-PRO, the same developer from it's successor, the A3i - I don't know exactly).

This version (with optional SRPP phono RIAA head amp modul) I know as a very fine sounded integrated amp despite sluggish/slow fuse in serial to the speaker connectors (instead DC protection relay contacts).

The schematic from this version I have and the topology is very close to those from douglas self blameless amp - only douglas self's buffer stage between the LTP and VAS stage isn't present here.

I've personally never heard the two later versions, but other user's tell me,
that they were disappointed about the sonic quality - compared to the first and discretely version from the A1 (BTW - in Germany the model name for the first version was "ATAC 3"/"ATAC3").

After check the images from the inside stuff (see attachments) the reason therefore is for me clear: Extremly cheap and bad capacitors for the power supply at both new versions of A1. Consequence is, that one hear mainly not the different amp topologies but the different quality standarts of the caps.

Now the question:
Who has heard all this versions by a compared listening test with high quality caps in the power supply?

Concerning this models there are follow threads here on diyaudio:
http://www.diyaudio.com/forums/solid-state/137234-cambridge-audio-a1-schematic.html
http://www.diyaudio.com/forums/chip-amps/39193-cambridge-audio-a1-v2-amp-problem.html
http://www.diyaudio.com/forums/chip-amps/174022-cambridge-audio-a1-mk3-upgrade-mods.html
http://www.diyaudio.com/forums/chip-amps/103006-cambridge-audio-a1-gainclone-conversion.html
http://www.diyaudio.com/forums/solid-state/71825-broken-cambridge-audio-a1-mk3.html
http://www.diyaudio.com/forums/solid-state/165757-cambridge-a1-mk2-line-amp-stage-power-suppy.html
http://www.diyaudio.com/forums/soli...dge-audio-a1-power-amp-section-schematic.html

 

[bitsandbobs]

I just wondered if anyone knew of the difference between the 3 versions? It's looking very much like the original version is the one to look out for!

Would that be true?

 

[a91gti]

I'd just like to figure out for sure which I have.

 

[a91gti]

...and a look at the back panel (lol) reveals it to be a v2.

 

[bitsandbobs]

Then it's possible the V2 is inferior to the V1 - who knows. Interesting that you own a Sony CDP-791, did you know that's also known as a Sony CDP-111ES? Is it a good sounding CD Player because there's one nearby in the charity shop which I have largely ignored.

 

[AndrewT]

which pic shows V2?

I can see a A1 mk3 SE V3 and an A1.

 

[Mortymore]

which pic shows V2?

I can see a A1 mk3 SE V3 and an A1.

This are from a V2 (with the dual TDA configuration)

What I realized so far is it seems one can usually tell from the front and the top case cut what is the power amp. technology fitted inside.

Version one has the volume at the right side of the case, were versions 2 and 3 have it at the centre.

v1 (volume at the right)

other versions (volume at the centre)

About the top cuts, with one like in the next pic, running from front to rear, it can be a 1st, 2nd or MK3 version

1st has transistors in the audio power section, the 2nd have the TDAs (TDA1514 I think)

A rectangular area nearer the front, as the next picture shows, means that a single LM4766 is fitted inside, and it is version v3

PS: MK3 can have, as far as know, versions 2 and 3. Just look at the top of the case to know if it has TDAs/LM3875 or a single LM4766

 

[borderline13]

Hi all, would anyone happen to have the schematic for a Cambridge Audio A1 Mk1 please?

Have just bought one of these and need to adjust the bias but have no idea where to measure it.

Thanks

 

[AndrewT]

Are you sure you need to measure and/or adjust the output bias?

 

[borderline13]

Hi Andrew,

Thanks for responding

The left channel heatsink is remaining cold whilst the right is warm to the touch. I've used the schematic for the A3i to judge where to measure bias current and the right channel reading is 10mV whilst the left is 0.5mV.

I've noticed the left channel output transistors have been replaced at some point so assumed someone has forgotten to adjust the bias accordingly.

Really could do with the service manual to check for correct readings.

 

[jaycee]

The last version with the LM4766 is also available with a toroid instead of the woefully undersized EI transformer.

My guess is they switched to the undersized EI because the original 120VA toroid, backed by 10,000uF per rail, can make the chip explode with the volume turned up. This is what I found in the version of the A1mk3 SE 3.0 I got from Freegle, damaged.

The TDA1514 was not a bad amplifier but it suffers from cheap parts in the Cambridge. Replacing the electrolytics with decent parts really helps.

The Cambridge Topaz AM1 is the same circuit as the last revision of the A1, just optimised to remove the tape loop, phono input, and get the whole thing on one board. Very poor, IMO.