Yamaha A-1 using ‘pre-out.’

[Hifibythekg]

Hi, helpful fellow AKers have pointed out that the signal from the pre-out on the well-regarded ‘Yamaha a-1 integrated amp’ (note, not the DSP-A1) has to navigate the power section before arriving at the RCA sockets. This routing suggests that the pre-out’s signal quality will be comprised.
Question:
Has anyone actually experienced using the A-1 as a preamp, and if so what are or were your impressions?

 

[Hifibythekg]

Here’s some photos of the a-1 that I’ve been offered.
It’s been in storage for years and obviously needs cleaning but does anything seem majorly amiss on first sight?
Apparently the relay cuts it out when volume is turned up more than 30%..

 

[Asmodeus2112]

I'm a novice, but if no one else chimes in I would recommend a light compressed air or vacuum for initial clean, close inspection, then using a DBT on first power on. If no shorts then get the service manual and set idling current and DC offset etc. I have a soft spot for A-1's and own two. I cannot comment on using it only as a pre. Interesting comment about the signal going through power supply. Audio Science Review tested an A-1 and it did have a bit of power supply noise. This could be related to the unit under test's age and condition though.

 

[Hifibythekg]

Cheers Asmodeus. Helpful advice.
Glad you like your a-1's, so I presume that you've been able to enjoy/maintain them fairly trouble free?
Also notice the C-4 and M4 combo in your equipment list. I hear that there's little to distinguish between this and an a-1 except maybe for speaker control in the bass? Fair comment, or would you add anything?
I really wish that the 'pure' signal from the pre-amp section could be routed out directly, but one AK'er mentioned high transients on start up..
I have a self restored Yamaha P2200 which I really want to keep as my the power component in my set up but it's increasingly difficult to get an affordable Yamaha preamp (C4, C2a, CA1020 etc.) in the UK.

 

[Asmodeus2112]

At the moment both of my A-1's are original. I have only cleaned and adjusted one, the other just arrived and I have not touched it yet. It's possible that they may not be at their full potential. The C-4 has more features than the A-1. 3 TTs, turnover frequency adjustment etc. And the M-4 has more power. Yes, they are from the same era, so are very similar designs and parts. I don't have the equipment to measure "high transients at startup" or what ever noise the power supply section may add to the proximity of the pre out. My mid-fi ears think they both sound great. I listen to the C-4/M-4 a lot, but do not have much time listening to the A-1's. As time allows I will try connecting the A-1 as a pre amp to one of my M-4s and see if I can perceive a difference. Both of my M-4s have been recapped and sound identical to my ears, so that could be an interesting comparison. Sorry I can't help you more with your questions, I spend more time at my bench working on them than in the listening room...

Edit: I spend more time at the bench because I like projects and have too many of them. Not because the components are troublesome. After cleaning recapping my C-4 and M-4s have been very reliable.

 

[Hifibythekg]

Thanks Asmodeus, all good to hear.
Yes, would be interesting to see how the pre out of the A-1 performs, but only when it suits, you’ve probably got the C4-M4 set up working just fine as it is.

 

[avionic]

This routing suggests that the pre-out’s signal quality will be comprised.

Explain...Convince me..