Yamaha A-1 amp conundrum ...
- Thread starter reneborg
- Start date
dspear99ca
Super Member
I am just curious why you would recommend that the OP purchase an M-4, granted a fine amplifier, when he's got a perfectly functioning amp section of his A-1... and the load on it is miniscule... the TC-50's roll off at 85Hz, really you could drive them with a 40wpc amp very very well. It would be simple as far as no chop-job required on the A-1, but then the A-1 amp section just sits there doing nothing... and the cost to modify is maybe $25 worth of parts (includes shipping) vs. several times that at least for the M-4.
Maybe there's something I'm missing, it's certainly happened before...
Dave
I haven't actually heard these particular Spicas, but have heard wonderful things about them. I switch out equipment almost daily, so I'm probably coming at this from a different place.
Even if you go the route of buying another amp to use with the Spicas using the A-1 as a preamp, I would suggest keeping the A-1 even if you eventually go with a stand-alone preamp. It's really a great piece of equipment. To my ears it sounds much much better than some of the more talked about vintage gear I've had. It just gets a lot of things right, and the preamp in it has a way of just, well, getting out of the way. It's very clear without sounding sterile or lifeless.
I agree, the A-1 sounds really nice with my Spicas. In fact, they sound like new speakers.
With the A-1, the Spicas sound more lively and they have a lot more detail in the mid-bass range; I also like the highs better than with my previous amp, but the difference is not as great. There is a much greater dynamic range with the A-1 than with the similarly powered Nak RE-2 it replaced. That's why I'd really like to get something that works with my Spicas and sounds like the A-1 -- especially its phono section! The A-1's tremendous build quality is awesome too.
Oh, . . . about switching gear around ... I guess I'm very monogamous when it comes to speakers. I've switched around a bit of electronics (but certainly not daily!), but my speakers, TT and cartridge have been the same for a number of years now. I've connected a few other speakers for a week or two, but nothing other than the Spicas has lived with me for quite some time.
dspear99ca
Super Member
One last thought... I mentioned you could just let the Spica's roll off naturally i.e. sans crossover. I do this with my Super Zeroes and really, I'm happier with the sound than with using the Velodyne crossover in my sub. You could try the pre-out to the Passive box, using the low-out to the sub amp, and just connect the TC-50's to the A-1's speaker terminals. So you're feeding them low frequencies they can't reproduce... maybe not 100% ideal but I think you might like what you hear.
I've tested my in-room response with an SPL meter and it's pretty flat.
Just my 2 cents.
Dave
I've tested my in-room response with an SPL meter and it's pretty flat.
Just my 2 cents.
Dave
Dave .... Great minds think alike
I already tried this and YES, the A-1 and the Spicas and sub sound much nicer powered by the A-1 than they do with 2 other amps I'm listening to. But, because of the Spica's design, it's just like you say, not ideal. With the extra low-frequency information going to the TC-50s, they sound somewhat constrained ... I don't know if that's the best word, but you can tell the speakers are 'limited' at the low frequencies. They don't sound so constrained when those lower frequencies are filtered out.
That's why I started to seek other possible solutions ... I REALLY like the A-1 sounds very 'musical' to me ... whatever that means :scratch2:
If it's the added dynamics you like, getting into the separate pre/power amp game might be your thing. If you think using the A-1 as just a pre is a waste...I'm using a Sansui 9090db as just a tuner! And it's a fantastic tuner at that.
I love integrated amps, but only run them in my bedroom system. Once I went to separates, and heard how much better I liked the sound, I don't know that I can go back. It's not as cut and dry, though, as an integrated. Some amps I've tried sound great with some preamps, some don't. But the A-1/M4 combo should be great. I like the sound of the A-1 preamp section better than my dedicated C-80 preamp. The C-80 seems flat/2 dimensional in comparison. It's not bad by any means, but the A-1 is very direct and simple. Hence...the direct switch.
I love integrated amps, but only run them in my bedroom system. Once I went to separates, and heard how much better I liked the sound, I don't know that I can go back. It's not as cut and dry, though, as an integrated. Some amps I've tried sound great with some preamps, some don't. But the A-1/M4 combo should be great. I like the sound of the A-1 preamp section better than my dedicated C-80 preamp. The C-80 seems flat/2 dimensional in comparison. It's not bad by any means, but the A-1 is very direct and simple. Hence...the direct switch.
Wow ... so you think your A-1's preamp section sounds nicer than the C-80 ... who would have thought!?
and I do appreciate the added dynamics. the attack of the notes is better. I think I hear more of a difference between the A-1 and the other amps with records as a source than when CDs are the source, but I'm not 100% sure that's my final answer.
and I do appreciate the added dynamics. the attack of the notes is better. I think I hear more of a difference between the A-1 and the other amps with records as a source than when CDs are the source, but I'm not 100% sure that's my final answer.
My taste in preamps has been going towards less is more, and the C-80 seems to have a lot going on, even when the tone-defeat is on. It's dead quiet but something just seems kind of off about it. I never end up listening to music very long when it's in my rig, which is the best test I have for how well something is working. Everything sounds good if you just listen to the sound, but music seems to get lost in it somewhere. If you want options and tone controls and a pretty effective loudness contour, the C-80 has all of that and it all works very well. I get lost in the music with the A-1, though. I never ran the C-80 and A-1 as pre in the same system, though, so the comparison might not be fair. The C-80 was with a powerful amp and big power hungry speakers, the A-1 with a little 80wpc Heybrook amp and smaller, efficient speakers.
Should have posted this pic sooner!
Despite my lack of clarity in my first post in this thread, I hope that by now all of you folks understand how the passive interface works with the pre-amp out and power-in jacks and the Spica satellites and servo subwoofer. What I should have done from the get go is post a pic of it, eh?
Here ya go:
Passive Interface for the TC-50s and Servo Subwoofer: the PRE-AMP output goes to LR IN jack, and the satellite output from the Passive Int. goes to the POWER-IN or amplifer input for amplification. The Servo out goes to the powered subwoofer.
The interior is simple, you can see it here:
http://www.audiokarma.org/forums/album.php?albumid=484
Thanks again everyone!
Despite my lack of clarity in my first post in this thread, I hope that by now all of you folks understand how the passive interface works with the pre-amp out and power-in jacks and the Spica satellites and servo subwoofer. What I should have done from the get go is post a pic of it, eh?
Here ya go:
Passive Interface for the TC-50s and Servo Subwoofer: the PRE-AMP output goes to LR IN jack, and the satellite output from the Passive Int. goes to the POWER-IN or amplifer input for amplification. The Servo out goes to the powered subwoofer.
The interior is simple, you can see it here:
http://www.audiokarma.org/forums/album.php?albumid=484
Thanks again everyone!
merrylander
AK Member
Just to clarify something, the A-1's pre-out is derived from a sort of voltage divider network immediately before the output transistors, I would not recommend mucking about in there.
dspear99ca
Super Member
So it's not a pre-out, it's just called that. Really it's an attenuated take-off from the signal path within the main amp circuitry. Any idea what the benefit of this approach is? I've never seen anything like it.
Still not having seen a schematic, isn't there a point where the tone amp or volume control is coupled to the input differential pair that could be broken?
Just a guess here... but could this weird circuitry be due to the A-1's "DISC" mode? There's a block diagram that gives the general sense of what they are doing ....
Also there's a page here showing the schematics of the area I THINK may be what Merrylander speaks of ... This link, however, gives you a larger sized file
Also there's a page here showing the schematics of the area I THINK may be what Merrylander speaks of ... This link, however, gives you a larger sized file
Attachments
Last edited:
I got your PM reneborg, and I do not recommend doing anything to the A-1.
I'd run the pre-out to the filter box, and run the output to the sub. The main L&R speakers get powered from the A-1, but it would be easy to rig up a 1st or 2nd order filter for these main L&R speakers to keep a bit of the bass out of them.
That is by far the easiest solution, and prevents modding a rather nice integrated amp.
It is a little odd that an integrated of this caliber does not provide full pre-out/main-in functionality, but a simple passive filter to the main speakers will put ya back in business.
I'd run the pre-out to the filter box, and run the output to the sub. The main L&R speakers get powered from the A-1, but it would be easy to rig up a 1st or 2nd order filter for these main L&R speakers to keep a bit of the bass out of them.
That is by far the easiest solution, and prevents modding a rather nice integrated amp.
It is a little odd that an integrated of this caliber does not provide full pre-out/main-in functionality, but a simple passive filter to the main speakers will put ya back in business.
dspear99ca
Super Member
Yes. RC high-pass filter. Easy, cheap and simple. Do you have the specs on the Spica crossover box, i.e. corner frequency and slope?
It looks like the pre-out is AFTER the output transformers, it's exactly like another headphone jack.
I don't see a downside, other than the fact that you're bastardizing (in a good way) the A-1 circuitry, to adding real pre-out (you could even use the existing "pre-out" jacks) and main-in, splitting just upstream of the input FET IC (IC701 & IC702 on the power amp board). I can't read the component values on the schematic scan, there may be some issues with cable capacitance for longer interconnects.
Well, I was thinking CL filter. But he gets the idea.
The scat is too difficult to read to make any real suggestions about modifying the amp, but I stick by my recommendation that it's a bad idea and that there are better solutions.
dspear99ca
Super Member
And i will defer to your more extensive experience... I have a vague recollection of having had this discussion before, in particular about the necessity of adding high-value resistors to ground on whatever side of the pre/main split doesn't have them...
Was it not you who put up some photos awhile back of unity-gain op-amp buffers on the pre-outs of a Kenwood receiver you had split to give it bullet-proof output impedance?
Well, I just spoke on the phone with the person who knows a lot more about Spicas than I do ... he's the person behind the spica enthusiasts web site.
Here's a link to the Servo Sub-woofer's manual, which has the info needed for building the high-pass filter as kindly suggested (see pages 4-5). Now, you folks will know and understand more about why this is, but John, the gentleman of the spica website, pointed out that the benefit of having the filter before the amplification stage is that impedence is more constant than what is presented to the speakers after amplification (?? Did I get that right, guys?? :scratch2: )
So, he thought that the finished product would sound ok, but the phase coherency of the Spicas would be lost. Something to do with the actual values of capacitors vs. EFR or ESL? In essence, the filters would work differently before amplification than they would after ... does this make sense at all ???
Here's a link to the Servo Sub-woofer's manual, which has the info needed for building the high-pass filter as kindly suggested (see pages 4-5). Now, you folks will know and understand more about why this is, but John, the gentleman of the spica website, pointed out that the benefit of having the filter before the amplification stage is that impedence is more constant than what is presented to the speakers after amplification (?? Did I get that right, guys?? :scratch2: )
So, he thought that the finished product would sound ok, but the phase coherency of the Spicas would be lost. Something to do with the actual values of capacitors vs. EFR or ESL? In essence, the filters would work differently before amplification than they would after ... does this make sense at all ???
We're talking about filtering the amplifier output to the L&R channels...like a crossover with no cross. A cap in series with the '+' terminal, and an inductor in parallel (for a 12db/octave rolloff), to mute some of the bass that the subwoofer is already handling.
No one suggested that this is the ideal solution for your speakers. Your choice of integrated amplifier has already rendered that option unavailable. But using high-quality film caps and inductors in the C-L filters for the L & R channels should give you results that are more than adequate. It certainly isn't the end of the world. All we're doing is rolling off the bass. No biggie.
If you want to use the speakers as they were apparently intended to be used (which seems to be an intentional PITA [sorry John Bau, but what the hell? :scratch2:]), then you need a separate preamp and amp, or a receiver or integrated with true pre-out/main-in jacks. If you want to use them with your current setup, see my previous post on the subject.
Edit: I took a look at the manual you linked to. It looks like the 'box' is a passive line-level filter to the main L&R channels. IMHO, this is a questionable approach, as amplifier input impedence specs are often not much more than educated guess (at least with BJT transistor inputs). Using this type of filter is not very accurate, to be kind. If you have a reasonable handle on the impedence of the L&R satellite speakers, you can probably do a better job (frequency-wise) with a high-level filter such as I previously suggested.
There are advantages to filtering at a line-level and feeding the filtered signal to the amp, but many of these advantages are lost by attempting to do it with passive devices at such low signal levels and varying amplifier parameters.
Last edited:
