Tape in + tape monitor = passive preamp?

I took a look at the schematic for your B60R integrated amplifier.

First, along the lines of Newbee's comment, there is an active amplifier stage between the tape input and the input to the power amplifier section (or, correspondingly, between the tape input jacks and the preamp output jacks). So it cannot be considered to be a passive preamp, and more generally I don't know that it would be particularly meaningful to speak of the preamp section of an integrated amp as being passive even if that amplifier stage were not present.

The reason you are losing bass is that the input impedance at the tape inputs is very low, and your source component probably has an output impedance which rises at low frequencies (presumably due to the presence of a coupling capacitor at its output).

The input impedance of the regular line-level inputs appears to be close to 50K (50,000 ohms). The input impedance of the tape inputs will vary between 5K and 10K depending on the setting of the balance control. With the balance control set at mid-point, it will be 8.33K, according to my calculations. That is a very low value, which can only be driven properly by a source component having either very low output impedance, or an output impedance that varies very little with frequency (which most components are unlikely to have).

Unless detailed information is available on the output impedance of the source component, including its variations with frequency, and unless that information indicates a low output impedance at all frequencies (which your sonic observations suggest will not be the case), my recommendation would be to go back to the regular line-level inputs.

Regards,
-- Al

One further thought: I would speculate that the reason you are sensing increased detail using the tape inputs may simply be that the attenuation of the low end is leading you listen at a higher volume level in that configuration.

Regards,
-- Al

In the last sentence of my previous post, that should obviously be "leading you to listen at a higher volume level," not "leading you listen ..."

-- Al

I too use a BCD-1 as my cdp. Great minds think alike!

I use it's balanced outputs into the balanced inputs of a Classe CP-60 preamp, and I've been very pleased with it, listening mainly to classical music.

But I'm surprised to hear that is what you are using, because I don't think that the low frequency rise in output impedance from 74 to 106.5 ohms would be audibly significant, even into a 5K input impedance, which appears to be the worst case possibility for your B60R's tape inputs. So I'm not sure how to explain the bass loss, unless the output circuit of the BCD-1 is just uncomfortable in some way driving that low an impedance.

Re the comparisons being level matched, it's hard to tell from the schematic what the gain of the input buffer stage is, but it seems conceivable to me that it could be a bit less than 1 (resulting in a slightly lower volume at the same settings than from the tape input).

I don't think that the B60R has balanced inputs, so you can't use the BCD-1's balanced outputs without an adapter, which is not a good idea to do generally on outputs (most adapters short the inverted signal on pin 3 to ground). And it wouldn't help anyway because the adapter would simply route the non-inverted output to the amp's unbalanced input, the non-inverted output presumably having essentially the same voltage and impedance characteristics as the single-ended output.

Regards,
-- Al