Tube Pre-amp in Front of Integrated Amplifier

DavidS · « **on:** 20 Oct 2015, 03:51 pm »

In the past year I have downgraded my system (from big tube monoblocks and separate preamp) to running a small solid state integrated amp - actually it's my second time on the dance floor with an Audiozone Amp-1. The sound with my Merlin TSM's is fabulous, a nice match.

But there is always a but. The amp only allows for a single source at a time and most of the time my turntable and tuner sit on the side line while I play cd's through an Audio Note transport and Lampizator dac.

So I have been thinking about ditching the little amp for the second time in 10 years or maybe just maybe adding a small tube preamp between sources and amp. I don't read a lot about people adding preamps in front of integrated amps (why would you mostly) but wondering if anyone has experience, or thoughts about what I should think about or expect if I go down this path. May have to try and borrow something but thinking Decware or Eastern Electric or something along these lines that I can't demo.

RDavidson · « **Reply #1 on:** 20 Oct 2015, 04:36 pm »

Just get a high quality switch box. This way you're not messing with the sound you currently enjoy. Any preamp will do more (add more variables) to the signal than just a simple switch box would.

Looks like Decware has a nice one and you just choose the options you want:
http://www.decware.com/newsite/ZSB.html

parbaked · « **Reply #2 on:** 20 Oct 2015, 05:09 pm »

That Amp-1 is nice looking. I have a Shigaraki in the living room and i love it.

A switch box is a good idea, and the Decware model a good choice.

If you already have a pre-amp, and it has a Tape Output, you can use it as a passive switch box and you don't even have to turn it on.
I use the Tape Output an old VTL pre-amp as a line selector and phono pre-amp to feed a single input integrated tube amp.
The Tape Outputs provide a line level signal even when the pre-amp is off.
I only turn the pre-amp on when I want to listen to the turntable.
Cheers!

Early B. · « **Reply #3 on:** 20 Oct 2015, 05:17 pm »

Is it possible to get your amp modded to allow for a second set of inputs?

DavidS · « **Reply #4 on:** 20 Oct 2015, 05:55 pm »

all these years later Audiozone does seem to make custom 2 and 3 input versions but would mean a new amp I think. I could ask about modding my amp.

Will also look at the switchbox idea - the one I had in the way back past seemed to degrade the sound quite a bit.

The preamp angle - so is the sound going to be degraded or just different and maybe like different something I like (such as the combination of amp and preamp that is better together).

RDavidson · « **Reply #5 on:** 20 Oct 2015, 06:43 pm »

Quote from: DavidS on 20 Oct 2015, 05:55 pm

all these years later Audiozone does seem to make custom 2 and 3 input versions but would mean a new amp I think. I could ask about modding my amp.

Will also look at the switchbox idea - the one I had in the way back past seemed to degrade the sound quite a bit.

The preamp angle - so is the sound going to be degraded or just different and maybe like different something I like (such as the combination of amp and preamp that is better together).

Early B's suggestion is the best.

Something along the lines of the Decware is probably 2nd best.

Adding a preamp, it's truly impossible to say whether this will be a combination you will like. The other options introduce the least variables. You said you like how your system sounds now, so why go a route that could mess it up?

Maybe a decent alternative would be a tube buffer with input selection, if such a thing exists. Your amp doesn't need to be fed a signal higher than 2V. Active preamps typically output much higher voltages and have a lot of "extra" circuitry you really don't need. With a buffer, you'd still use your integrated's volume control vs adding a 2nd one in the mix, add some tube flavor, and perhaps even provide a more ideal signal (voltage and impedance) to the amp than your components provide.

parbaked · « **Reply #6 on:** 20 Oct 2015, 07:01 pm »

Quote from: DavidS on 20 Oct 2015, 05:55 pm

The preamp angle - so is the sound going to be degraded or just different and maybe like different something I like (such as the combination of amp and preamp that is better together).

If you already have a preamp that has a 'tape output', you can use it as a switch box with no sonic degradation.
The tape loop is designed to record to tape exactly what is at the source with no sonic signature from the preamp.
As such the tape output bypasses all the preamp functions and any sonic impact. Volume, balance or tone controls don't work.
It functions the same as a passive switch box.
It's just another option if you already have a preamp with tape out...cheers!

DavidS · « **Reply #7 on:** 20 Oct 2015, 07:49 pm »

I don't have a preamp to try - sold my separates to go with this minimalist integrated amp that I thought I could live with just rotating interconnects. Can't - its a pain in the ass - so result is other sources sit unused. Will look more closely at the decware switch box, thinking Mapletree Audio up here in Canada makes one of those as well. Thanks for the feedback and suggestions.

sfox7076 · « **Reply #8 on:** 20 Oct 2015, 09:25 pm »

Add a volume control with preamp to the Lampi.

elmalloc · « **Reply #9 on:** 20 Oct 2015, 10:46 pm »

Audiogon has a Decware ZSB switchbox for sale (used). I'm considering getting it for my setup, if you or someone else doesn't.

Quiet Earth · « **Reply #10 on:** 20 Oct 2015, 10:55 pm »

I think I would get a tube preamp.

One reason is that a tube preamp offers a lot better control with more meat on the bones than a switch-box. Well, it can offer more control - I don't know what your budget is.

Another reason is that it can be an opportunity to upgrade your phono stage. But I don't know what your phono stage is so maybe not.

And the best reason I think is,,, do you really have an integrated amp or do you have a power amplifier with a volume control between the input Jack and the first gain stage. I think you have an amp with a volume control in front, not that there is anything wrong with that. That certainly offers you more value for your dollar.

I have heard very good results putting an active pre in front of this type of "integrated" amp before. Just turn the amp volume controls all the way up or use them as trim pots and pretend that it's a regular stereo amplifier. Which it is, really.

Anyway, food for thought. I would try a good tube preamp, especially since your speakers are only 87dB efficient. You should not have too much gain. Just more control, better bass, and a feeling of more power. A lot more than you will get by adding a switch box. (Which is a good idea too, just kind of boring.)

JakeJ · « **Reply #11 on:** 21 Oct 2015, 03:50 am »

Does the Amp-1 have pre out/main in connectors? If not then you would be have a pre-amp feeding a pre-amp. Not good, impedance mismatch, distorted sound. If the Amp-1 just has a volume control (passive front-end) then it might work if the impedance isn't too out of whack. You will have to fine tune a bit between the two volume controls (the tube pre-amp would be the controller and you should find a spot on the Amp-1's volume that sounds good and allows you full use of the tube pre-amp's volume range, likely near full open).

If the Amp-1 does have pre out/main ins then you just need to match the tube pre-amp's output impedance to the Amp-1's power amp input impedance. You might actually improve the SQ.

From Wiki: "General rule of thumb is for the load (amp) input impedance to be at least 10 times higher than the source (preamp) output impedance."

DavidS · « **Reply #12 on:** 21 Oct 2015, 05:32 am »

no preamp out on the amp-1 - this is a very minimalist design with only one set of rca's in and dual mono setup for volume control and speaker cable out. I think closely based on the Shigaraki as parbaked notes above. Yes I am concerned about impedance mismatch with a tube preamp although as noted by Quiet Earth there are potential benefits.

parbaked · « **Reply #13 on:** 21 Oct 2015, 02:41 pm »

I have tube amps with a volume control but they are not integrated amps in that there is no additional pre-amp gain stage.
They just added a volume attenuator to the circuit for balance trimming or to optimize the volume settings on one's pre-amp.
Most of these you turn up the volume control to full to bypass the attenuator and revert to a power amp.
Shindo and Air Tight, for example, have such an attenuator on their power amps.

I believe my Shigaraki (and the Amp-1) are true integrated amps and I would not use them with a pre-amp - unless using the tape output which bypasses the pre-amp circuit and allows it to act as a line level switch box (and phono pre-amp if desired/required).

Quiet Earth · « **Reply #14 on:** 21 Oct 2015, 04:15 pm »

In the old days, "integrated amplifier" meant that you have a selector switch, a phono stage, and a discrete line stage preamp all inside of the amplifier package. Sometimes the phono stage would be left out, but there was always a selector switch and active line stage. That's what I usually think of when I see the word integrated.

Today, "integrated" means that you put a volume control in front of an amplifier. Times change. Gear changes too.

I thought the Amp One was based on the chip amp concept. I was thinking in terms of RCA input connector -->10k attenuator --> chip amp module --> speaker binding post. That's basically an amplifier with a attenuator in front of it. Is there a discrete line stage before the chip? I suppose you could say that the "preamp" is built into the chip. Fair enough. (I will admit that I don't own this amp so please jump in and correct me on how it is laid out.)

Still, the only way to know if you can improve the Amp One with a tube preamp would be to try it for yourself. That's really the only way to know. You will need a preamp that is comfortable driving a 10k load. Of course, right now your source needs to be comfortable driving that 10k load since it is going directly into the Amp One. But it seems like you are not having any problem in that regard so maybe a passive switch is all you need. It will take a very nice preamp to beat a passive switch in terms of clarity, transparency, etc.

But like you said in your original post, there is always that "but."... You never know until you try.

Quiet Earth · « **Reply #15 on:** 21 Oct 2015, 04:25 pm »

Check this out : http://www.wrightaudio.us/PCC.htm

I have had my eye on this for a while. It seems like a really neat way to add more inputs and outputs to an existing set up, regardless of whether you have an active or passive set up. You can use the included volume control or you could bypass it and use it as a selector switch. You could add tape out, or send the signal to different amps. Very clever idea! Looks well made too.

RDavidson · « **Reply #16 on:** 21 Oct 2015, 04:37 pm »

Why add another possibly signal degrading passive volume pot in the mix, when all he really needs is a switch box?

Not trying to sound antagonistic. I just don't understand the point. I know you have a lot of experience with these types of things QE.

Quiet Earth · « **Reply #17 on:** 21 Oct 2015, 04:43 pm »

Look at the back of it. You can connect the amplifier to the volume controlled output, or you can connect it to one of 3 pairs of fixed outputs. This would be the same as using the tape out of an old preamp, or having a selctor switch without a volume control.

RDavidson · « **Reply #18 on:** 21 Oct 2015, 04:47 pm »

Oh OK. You're just suggesting it as possibly a more versatile route than just a switch box.....then again, we know passive volume controls can bring a slew of possible issues too. It's definitely a neat device, though the volume pot is a YMVV addition.

Quiet Earth · « **Reply #19 on:** 21 Oct 2015, 04:57 pm »

Yeah. Just a suggestion for a very versatile passive control center. You could do a lot with that one. (I like that the switches are dual mono too.)