Need Help to Understand Issue with Volume Control

I'm having an issue with the volume when I use my Classe CAP 101 integrated with a newly-purchased Sony HAP S1.  I hope someone can help me understand what is going on.  The Classe has 5 sets of RCA inputs (and one unbalanced set).  It's volume control has a range of 0-50 in half-steps.

I have a Sony CA70ES cd player that I have used for years with the Classe, connecting its Line Out to the Classe's Reg1 input with a pair of "upmarket" Radio Shack interconnects.  For as long as I have used it, my typical volume range is 16-22, depending on time of day, music, my mood, etc.  At my listening position, which is 7-8 feet from the speakers (Harbeth Monitor 30s), a sound meter app on my iPad reads roughly in the 50-62 db or so for that volume range.  According to Sony, the output voltage for the CA 70ES is 2 volts.

I connected of Line Out of my new Sony HAP S1 to the Classe Req2 input using a spare pair of very basic RCA interconnects.  (To be clear, I'm not using the Sony's internal amplifier, and its volume is set at "Min" or zero.)  To my surprise, the "usable" volume range for the HAP S1 reads on the Classe from 4.0 to 6.5, and most often at the lower end.  Lower than 4.0, and it's too soft; higher than 6.5, and it's way too loud.  According to Sony, the output voltage for the HAP S1 is 2.2 volts.

I think I lose a lot of flexibility in setting the volume when I use the HAP S1.  I've tried everything I can think of to try to figure this out. I scoured the internet without success.  I asked my dealer, but he had no clue.  I contacted Sony Support, which tried to duplicate the issue but could not, and therefore told me that the problem was not in the HAP S1.  I tried connecting the cd player to the Classe's Req2 and the HAP S1 to the amp's Req1, and I tried connecting the two sources to all the different inputs on the Classe, but I got the same results.  And, I tried switching the interconnects, using the basic RCA with the CA70ES and the "upmarket" interconnect with the HAP S1, but again the same results.

Can anyone provide some insight as to what is going on and what, if anything, I can do about it?  Thanks for reading and for your response.

The root cause of the problem is that the preamp section of the CAP-101 has an **extremely** high gain of 31.5 db. Meaning that it provides 31.5 db of gain when its volume control is set to max, which is how preamp gains are defined. It also has a slightly higher than average gain of 29 db in its power amplifier section. Also, the large change in volume you described that occurs between settings of less than 4 and more than 6.5 may reflect the fact that many preamp volume controls are intentionally designed to provide volume steps at very low settings that are much coarser than the step sizes that are provided over the rest of their range. Finally, the 2.2 volt figure for the maximum output voltage of the HAP-S1 may not be accurate; this document shows a 2.2K output impedance, but does not provide a spec for output voltage.

One thing that might be worth trying is connecting the HAP-S1 to the tape input of the CAP-101. It is conceivable that the CAP-101 **might** provide less gain from its tape input than from its other line-level inputs, although relevant specs from which that could be determined don’t seem to be available.

Aside from that possibility, as Yogiboy suggested you’ll have to insert an attenuator of some sort between the two components. In addition to the one he suggested, you might consider a Rothwell attenuator. Among the three attenuation values that are offered, my instinct in this case would be to go with the 15 db value.

On the other hand, though, the use of a passive preamp or passive attenuator between the HAP-S1 and the CAP-101 raises some concern about impedance compatibility, given especially the rather high 2.2K output impedance of the HAP-S1 and the very low 10K input impedance of the Schiit. I have measured the unspecified input impedance of the 10 db version of the Rothwell attenuator as being in the vicinity of 30K, and I would expect the input impedance of the 15 db version to be even higher. So my guess is that the Rothwell would be a better choice for this application than the Schiit.

Good luck. Regards,
-- Al

You have to measure the output voltage to make sure the unit is to spec. If it's a lot higher than 2.2 volts then that is most likely the problem.
Yogiboy, thanks for directing me to that product.  Can you tell me whether, if I buy and use it, whether I then use it's volume control or that of the Classe?

Almarg, I've been reading your posts for years, and I am really grateful you took the time for such a long, thoughtful response.  Because I'm functionally illiterate about electronics, I mistook the output impedance for the output voltage.  I'll consider whether to try the Schiit or the Rothwell.  If you saw my question to Yogiboy, just above, I can see from the Rothwell that I'd continue to use the volume control of the Classe.  And I will try your suggestion for the tape input.

gs5556, that's a sound suggestion (no pun intended).  As Almarg pointed out, the spec for output voltage may not be 2.2 (that might have been my misunderstanding).




If you determine that you need to stick some method of lowering the output into the line out of your Sony, I have a pair of the Rothwell attenuators that I could sell. Not trying to poach your thread, but the Rothwells are a bit expensive when you have to order them for the UK (which I did). I'm not currently using them. They were purchased to help equalize the output of a CD player and a phone stage that had a large difference. They work as advertised. I believe mine are the -10 db version, but I could double check if you are interested.
All great suggestions but just out of curiosity why try to essentially hookup two integrated amplifiers together. A stand alone music server would have been a better option. You are basically adding components in the audio path that can be avoided altogether.