Would increasing the gain in the amp give more weight to the sound? Any negatives?


I have an integrated amp with passive preamp section and I feel that the sound is not full-bodied enough. The separate phono stage has 42db of gain and I use MM cartridge. When I play cassette deck, the sound is just right in this respect.
I talked to the designer, and he said that increasing the gain is theoretically possible, though time consuming.
And if I do want to increase the gain - by how much? The amp is 120 watt/ch/8ohm, speakers are 89db efficient, 8ohm.
inna
In integrated amps with passive preamp section it's common not to have full body sound, but transparent. I heard Creek amps with passive section and described them as Brittish-polite and shy amps. I like'm somewhat rude and brave -- in other words completely opposite.
It's not good idea to increase gain of power amp. In most cases the amp can loose stability and become microphonic, pick up emi and simply self-oscillate and hum. 
So theoretically and most trivial, you probably need active preamp and use your integrated as poweramp only.
The integrated has no either pre out or power in, so I would have to use regular line in input, this will bring compatibilty issues. Besides, I see nothing under $2k-$3k new worthy of my attention, plus $500 used interconnect, at least. Putting active preamp, preferably tube, in between phono and integrated is, of course, the first idea that I had.
All you need to do is to move your volume control all the way up and use one of line inputs of your integrated with preamp of your choice. Otherwise to move the right way you simply need to go to separates from your integrated amp.
I have not tried it myself, but, I know that some people increase the sense of body and weight by inserting a 1:1 "repeating" transformer into the line level signal (e.g., between the phonostage and linestage, between CD player and linestage, or between the linestage and the amplifier.  An example of a really good line level transformer is the old Western Electric 111c and 119c transformer.  This is discussed on some DIY sites, such as this:
Would increasing the gain in the amp give more weight to the sound? Any negatives?
I have an integrated amp with passive preamp section and I feel that the sound is not full-bodied enough. The separate phono stage has 42db of gain and I use MM cartridge. When I play cassette deck, the sound is just right in this respect.
I talked to the designer, and he said that increasing the gain is theoretically possible, though time consuming.
And if I do want to increase the gain - by how much? The amp is 120 watt/ch/8ohm, speakers are 89db efficient, 8ohm.
If it's all loud enough for you to listen to and all output to input impedances are a good match  (>1-10 ratio) Then no, all he would do to get more gain is to reduce the feedback, and this has it's own problems. (eg: distortion, damping factor ect) 

But if your phono stage is tube and maybe high output impedance with capacitor coupling, then this could be the problem, what is your phono stage, make and model? And what is your amp?

Cheers George  

Oops, I did not attach the URL, for some reason insert URL is not working:


http://theartofsound.net/forum/archive/index.php/t-10335.html

Inserting transformer? Interesting idea.
As I wrote in another thread, I currently use tape deck monitor as a kind of active preamp and run phono through the deck. This gives me just the right amount of what I am looking for with a slight loss of resolution. Pretty good but certainly can be improved.
The phono stage is AcousTech and the amp is Redgum RGi120, both SS.
well musical fidelity has inexpensive unity gain buffer device that also inverts the phase. one can be placed between the source and amp, but active preamp will work much more efficient than even mentioned inverting transformer. I struggled when I had Creek 5350 SE integrated amp till I purchased active preamp Classe 30. This preamp turned polite and shy Brittish amp into substantially better version...
Hi inna,
Your Redgum is a very low 10kohm input impedance, which could trouble some sources that have high’ish output impedances (eg >1kohm) this could be your problem if you phono stage is >1kohm.

I can’t find what the output impedance is of your Phono stage is, but I did find out just one of the few AcousTech phono stages, was designed by Ron Sutherland .

I just found this if it's your model.
"AcousTech Electronics PH-1 phono preamplifier "
" Recommended load: 10k ohms or greater"

You are right on the min, with the 10kohm of the Redgum if this is your Phono stage.

Cheers George
George, thank you very much. Yes, this is my phono stage. You see, the sound is not exactly lean, it is just not full enough.
So, I understand that increasing the amp's gain is a questionable idea that may do more harm than good. It's either putting active preamp between phono and Redgum or living with it as it is.
Inna, have you tried the two different cartridge loading options, as I remember back to the Supex SD900 days it preferred 10ohm loading to 100ohms as the 100ohms made it sound a bit too rounded.
You have plenty of output with the PH1 as it can give out 8v!!!, more than enough to clip any power amp, so you definitely don't need more gain with an active preamp.

Quote Stereophile on the PH1:" Input impedance: 100 ohms in parallel with 0.01µF (MC), or 47k ohms in parallel with 200pF (MM).

Cheers George

Gain does not affect body. In fact it can add quite a bit of noise.

What you want to do is increase input impedance.  You can do this with a high quality transformer, but not sure where you'd get one off the shelf.

Best,


Erik
erik_squires804 posts09-22-2016 1:58pmGain does not affect body. 

In reality gain (in pounds :-) directly and surely affects body. To test it, switch to ice cream, apple danish with coca cola few times per day or more and drive-thru adventures via famous American food chains to experiment on body and gain.

Aside from humor, gain is important to reach necessary signal strength. If it's insufficient, than there will be an insufficient body. Gain must be increased either at source or preamp level. Gain of poweramp will affect the output power, but if there's not enough input signal, this gain obviously won't affect body or even if it will it may not be to the benefit of sound quality.
He has up to 8v! available from the Ph-1 phono stage and if it’s a low impedance output (<500ohms), there is no "signal strength" problem.
As most amps only need .5-1v in for full output into clipping, so why add even more gain with additional noise as well??

Cheers George
@czarivey Of course, I'm talking relatively. Unplug the amp and of course body will be affected too.

In my experience however, an impedance mismatch is more likely to cause a weak, or whimpy sound than gain. Your mileage may vary.
I don't think he has an impedance mismatch, as the phono is solid state, unless they did something really stupid to make it high impedance output like some tube ones are.

I think it may be a case of the tonal balance of the cartridge or what the loading by the phono stage is, as he says the cassett deck is fine. 


Cheers George
Yes, recordings made from records sound just fine, no complaints about the cartridge. The AcousTech has only two fixed settings for MM and MC.
So what is this "body" that you guys are talking about? I'm no expert but based on my (limited) experience, this lack of "body" is either because of at least one poor quality component in the sound chain or poor impedance mismatch if the components are all top shelf. Using a tape out and the phone in and the rest of the chain makes it more difficult to pinpoint the weakest link in the chain. All the best.
Being a simpleton I would first experiment by adjusting the VTA of your cartridge (granted that this is doable with your deck/arm).

Too lean a sound would dictate lowering the back/tail of the cartridge.
Being a simpleton I would first experiment by adjusting the VTA of your cartridge (granted that this is doable with your deck/arm).

Too lean a sound would dictate lowering the back/tail of the cartridge.
PS, and sorry for the double post (was distracted).

An easy way of checking this (if your deck uses a platter mat) would be to shim the mat a bit higher.

To start, place a thin LP (like an 70’s/80’s Euro import) under the mat which will effectively lower the tail of the cartridge.

If the sound is more to your liking, but you want more fullness then try a thicker LP/shim.

If positive results are achieved then look into adjusting such properly through arm adjustment.

There could also be cartridge loading problems, but I won’t go into this as I don’t know what gear you are using (plus I probably wouldn’t know enough to give decent adcice anyway-:).
What cartridge are you using? And how long is your phono cable?

The reason I ask is that the relatively high 200 pf input capacitance of your phono stage, in combination with the capacitance of your phono cable (which is proportional to length as well as being dependent on the capacitance per unit length of the particular cable), and the capacitance of the wiring in the turntable, will be too high a total to be optimal with some MM cartridges. In those cases the result would probably be an over-emphasis of parts of the treble region, which could be perceived as an under-emphasis of lower frequencies and consequently as a lack of body.

Also, btw, I’ll mention for possible future reference that the 0.01 uf (10,000 pf) input capacitance of the PH-1 in LOMC mode, which George referred to above and which is confirmed in the PH-1’s manual, frankly speaking strikes me as absurd. While LOMCs are of course less sensitive to load capacitance than MMs, low capacitance is generally preferable with them (see the post by Lyra cartridge designer JCarr dated 8-14-2010 in this thread), and 10,000 pf is **extremely** high. Although presumably the high capacitance was necessitated by some aspect of the design of the phono stage.

Regards,
-- Al

Al, the cartridge is Goldring 1042, and the cable that goes from the cartridge right into the phono input is about 1.5 meters long, The cable from phono to the amp is 1 meter long.
Never tried LOMC with it so can't speak. Why would Sutherland do, as you say, nonsense?
Turntable set-up is doing alright.
The Goldring 1042 has a recommended load capacitance of 150 to 200 pf. Unless you are using a phono cable having particularly low capacitance, I would guess that the 1.5 meter cable probably has a capacitance in the area of 150 or perhaps even 200 pf, which means that together with the 200 pf input capacitance of the phono stage the cartridge is probably seeing close to twice the recommended load capacitance. So that could very possibly be a significant contributor to the problem.  On the other hand, though, I note that you indicated that recordings made from records sound fine.

Regarding the reason for the 10,000 pf input capacitance in LOMC mode, as I said it was presumably necessitated by something about the particular design. To hazard a very speculative guess, perhaps the circuitry is particularly sensitive to radio frequency energy, and perhaps a 10,000 pf capacitor was therefore placed at the input to provide a very heavy load at RF frequencies (the impedance of a capacitor decreases as frequency increases, and hence the loading it presents becomes heavier as frequency increases), that would filter out any such energy that might be generated by the cartridge (LOMCs have bandwidths extending up into the RF region) or that may be picked up from some other source.

Regards,
-- Al

Al, this is interesting. I have no idea of the capacitance of the Nottingham arm's wiring. Assuming that you are right that this does contribute to what I am experiencing, how would you explain the fact that when running the phono thru the deck I don't have such a problem, I only got slight drop in resolution and soundstage. And it's not only the deck, it's also an additional cable, by the way. Cables from both phono and deck are Purist Audio.
The deck maybe 47k and loading the phono stage differently to the 10k of the Redgum.

Cheers George
Interesting too. The deck is Nakamichi 682ZX. How does it load?
Found it. The Nak's input impedance is 50kohm.
This say to me that the PH1 maybe capacitor coupled and could be rolling of the bass into the 10k of the Redgum but not the 50k of the Nakka.
If so this is an easy fix, just make the output coupling cap of the PH1 4 x larger. eg: If 1uf make it 4uf.

Cheers George  
Nak's output voltage/impedance is 1v/2.2kohm. Plays real good.
According to John Atkinson's measurements in Stereophile the PH-1 has an output impedance of "220 ohms at all frequencies."  The review also indicates that the circuit "appears to be based on Burr-Brown OPA2134 op-amp chips."  A quick look at the OPA2134 datasheet indicates that it can drive much lower impedances than 10K, albeit with a slight sacrifice in how much output voltage it can swing.  So the 10K minimum load recommendation appears to be conservative, and the Redgum's 10K input impedance is unlikely to be an issue.
... how would you explain the fact that when running the phono thru the deck I don't have such a problem, I only got slight drop in resolution and soundstage.
It's hard to say, in part because the capacitance of the phono cable is unknown.  And it's quite possible that the excess load capacitance being applied to the cartridge is not a significant contributor to the issue.  On the other hand, though, perhaps the tape deck is a bit rolled off in the treble region, which might compensate for the frequency response peak that the excess capacitance is likely to be causing somewhere in the treble region.

What seems safe to say, though, is that the excess capacitance is causing the cartridge to perform at less than its full potential.  The degree to which that may be true, however, is anyone's guess.

Regards,
-- Al
 
Well, from what I can get there doesn't appear to be any components and cables mismatch, I think it comes down to the fact that passive preamp is no way to go if you want full-bodied sound, and this was confirmed by many here who tried it both ways. Most though not all prefer active preamp.
I don't think I will ask the designer to increase the amp's gain, it may throw the amp off the balance with little or no benefit, it would be a gamble, I guess. The resolution and soundstage decrease when running the phono thru the deck is slight, excellent Purist cables help a lot. I'll just wait till I am ready for a major upgrade.
I think it comes down to the fact that passive preamp is no way to go if you want full-bodied sound,
You countered that argument by your saying the cassette is fine. 
I would also hazard a guess that your PH1 will have a better stronger output stage and with more voltage than the old Naka's got.

Cheers George
I was talking about phono not deck. By the way, I didn't mention it because it doesn't bother me, but my CEC belt drive cd player also sounds better in this respect when routed thru the deck. It seems that the deck doesn't mind passive preamp, though I didn't compare its sound with an active one.
Try reversing the polarity of your speaker cables. You might discover that your system is reversing the polarity, and by flipping the speaker cables, you suddenly hear a richer sound. My system needed it. And, the one before that did too.
Genez has hit on a good point there, but it could be just one channel that's out of phase with the wiring in the cartridge/arm/or even the PH1. Just try reversing the polarity of one channel first. 

Cheers George
The cassette "sounds fine" but isn't the phono input equalized as well?