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I am new to the world of tubes and recently heard an Atma-Sphere S30, and was captivated by it! I am currently using a tube integrated, but would like to experiment with an OTL amp. My question is, could you run an analog volume control CDP (audio aero prime / opus 21)direct into an OTL amp like the S30, or would this be problematic? I would like avoid a preamp for both reasons of cost (money spent elsewhere) and system simplicity. I know virtually nothing about OTL design and was wondering if this was possible? It seems that there are no OTL integrated's on the market? I look forward to your responses.
Follow Ups:
I use a Wadia and run it directly to M60's with a 1.5m balanced interconnect. While I would not suggest that there is no room for improvement, I auditioned a couple of pre-amps in my system including Atma-Sphere's MP-3. Each time I've found the pre-amp subtracts low level detail.As always, there are variables. While some discount a digital volume control, my Wadia is designed to run this way. Other players may not be maximized if run directly. I suggest that you try it.
For what it is worth, I found that Purist cables are magical with Atma-Sphere products.
Ok, I've really mangled this thread.. Don't know what I was thinking but when I saw 'CDP', I thought Passive Volume control. (Yes, I am the brain specialist!)Essentially, I gave the correct answers, to the wrong question.
If you have a CDP (CD Player, doh) that does volume control in the digital domain, or does it in the analog domain *before* a line-amp output, there should be no real problems with running a nominal length of interconnect (2-3 meters) direct into one of our amps.
If the CDPs output is balanced, find out (from the manufacturer) if it is designed to drive 600ohms. If so, terminate the input of the amp at 600ohms and see how you like it.
Standard method is to simply add a 600ohm device across pins 2 & 3 of the XLR input. You can also try using two 300ohm resistors, one each on pin 2 & pin 3, tied to ground on the other end. Depending on how your XLR cable is constructed (use of shield / drain wires etc) one setup may work better for you than the other.
Sorry for the blinding confusion on my end,
I run my Granite variable tube output 657 straight in to my M60 monoblocks. Sounds waaaaaaayyyyyyyyyyy better than any preamp I have tried in there (Blue Circle, Joule, CJ) - more open, extended, clear, immediate, and with a serious amount more slam.As we're in the same audio group and are not that far away, you might want to stop over for a listen some day...
It is not a matter whether the CDP can drive an OTL or not. It is a matter of the CDP can drive the input stage of the OTL or not. As Legendre said, the S30 has input impedance of 600Ohm which is too low for passive. However, we are in the process of developing our own OTL that has very high input impedance and gain can easily be driven by our own passive. It our case, after our audition, we actually favour single ended input stage instead of balance.
Hi Paul,I apologize if my last post may have caused some confusion about Atma-Sphere amplifiers, and the S-30 in particular.
The standard input impedance of all Atma-Sphere amplifiers is 100Kohm single-ended, or 200Kohm balanced. The exception to this is the MA-2/MA-3 which can be switched between 100/200K and 600ohms.
If a customer is using one of our preamps (MP-1, MP-3) with one of our power amps, we suggest that they have us terminate the input of the amp (or the male end of the XLR cable) with a 600ohm resistor. This is to their advantage.
Keep in mind that most of the 'classic' recordings sought by audiophiles were made in an era when fancy hot-shot cables simply did not exist. Yet, as we tweak, upgrade and audition our systems, we continue to extract worlds of detail from these fine yet relatively simple recordings. How can it be that the recordists of yore were able to create such stunning results that it takes the best of our modern systems to reproduce them faithfully? I won't credit it entirely to low-impedance balanced lines (Ampex, Neumann and their ilk get plenty of credit), but this said - these recordings never would have been possible without the technology. It just works..
My main point is that balanced lines are good, but you are not taking full advantage of a balanced line when running it at high impedances. To this end, Atma-Sphere preamps are quite capable of driving a 600ohm load with full bandwidth. Speaking of bandwidth, this post is using more than its share at this point ;-)
Bill
This sounds new to me:"If a customer is using one of our preamps (MP-1, MP-3) with one of our power amps, we suggest that they have us terminate the input of the amp (or the male end of the XLR cable) with a 600ohm resistor. This is to their advantage."
I have a a MP-3 / M-60 combo connected with 1 mt. XLR cables. I always thought this was the ideal connection between the two units.
Would you pelase explain why it is advisable to add a 600ohm resistor? What would be the sonic benefits?
Thanks for your help.
Paul, would you mind emailing me a little more information on this new OTL design you are working on? Thanks!
OTL circuitry basically is pretty simple. It is the implementation, fine tuning and speaker protection that separate.
There is nothing inherently different about an Atma-Sphere OTL amp, or any OTL for that matter, which would preclude using a simple passive control.This said, you're never going to get that passive to properly control the interconnect cable. If the cable is *very* short (a foot or two) this isn't terrible, but start adding length and the lack of control quickly becomes an issue. Using a balanced passive control is a better idea, but ends up being the proverbial 'whistle on a plow' when you realize that it's still quite incapable of driving a low-impedance line - and it's at low impedances (600ohm) that balanced systems really shine.
In an era of hot (line-level) signal sources from CD players, tuners, etc most components don't actually *need* much (if any) preamplification to drive a given amp to full output. What a correctly designed line preamp really gives you is the ability to properly control real-world lengths of interconnect.
Glad you are enjoying the S-30; we enjoyed making it! ;-)
Bill, thanks for your response. I am new to tubes/OTL's, so let me just be sure that I am still on the same page, even though this sounds like more of an interconnect concern, but the issues you raise are still new to me. If I ran a 3'-4' single ended RCA out from the Audio Aero to the S-30, this wouldn't be an 'ideal' situation? Could you please give a recommendation on what you would see as the ideal progression of cables/components comprising these two components. Please feel free to add a preamp (any recommendations?) if necessary. How much (sonically) would I be losing without being able to properly control the interconnect cable? I look forward to your response!
I agree with Bryan's posts, but in addition I would add that it is best to take advantage of the balanced inputs on any Atma-sphere amplifier. Although the S30s will sound great when driven via the single-ended (RCA) inputs, there is a certain something that is gained by driving them via the balanced (XLR) inputs, using a truly balanced-output source, not a device that adds parts at its output to derive a balanced output from a single-ended one. In the latter case, one is probably better off using the single-ended outputs of the cdp to drive the single-ended inputs on the S30, etc. If your unit has balanced outputs, consult your owner's manual to determine whether the output stage is truly balanced or not. You will also get a little more gain via true balanced connections.
Thought I should mention one other thing. If you are new to OTLs, you might not know about the importance of speaker impedence. This might even be more important since you won't have extra gain from an active linestage. And if your speakers have low sensitivity (especially with the S30). With OTLs, speakers should be a minimum 8 ohm impedence, and the flatter the curve the better. So you might want to also consider some ZERO autoformers from Paul Speltz, which can boost the speaker impedence up to the optimal 16 ohms. Even if your speakers are 8 ohms, ZEROs make a big difference. If your speakers are 4 ohms, ZEROs are a must.
Yes, you can do it. You should be able to do it with any amp, and amp topology (OTL, PP, SET) should not make a difference as far as I know. I had a Resolution Audio CD50 that was used direct to a pair of M60s and the result was good. I have also run a phonostage direct to my M60s. I have always found sources direct to amps sounds very transparent but in my experiences it lacks the dynamics of using an active line stage. I think I would also say that digital direct to amps is almost too much. You can almost hear the bits.
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