On my ARC LS26 I changed OEM tubes for BAT Supertube DR and increased bass and also brought midrange into the light more. I would expect you can get the same results with the right tube.
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I agree with Cyclonicman that deep bass is not mainly provided by tubes, though they can be considered a tweak. As such, I think he would obviously agree that because some tubes supply more warmth and fullness, one might perceive or experience more of an apparent enhancement in mid and certainly upper bass/lower midrange performance. I have certainly found this to be true using Mullard 12au7s and Brimar 12ax7s simultaneously in my Air Tight ATM-3 monoblock amps. Of course, utilizing such a combination as this may, for some ears, also manifest an unacceptable degree of masked detail from the midrange on down. As always it comes down to a matter of personal taste and satisfaction.
Bob, got the Peach II's specs from enjoythemusic.com
Type: Vacuum tube stereo preamplifier
Gain: 16.7dB in Hi Mode; 16dB in Lo Mode; 0 dB in HT BYPASS
Frequency Response: 5Hz - 90kHz
Hum and Noise: -85dB
THD:0. 15% 20Hz - 20kHz ref. 2V out
Input impedance: 47k ohms
Output impedance: SuperLoZ Mode: 90 ohms; HiZ Mode: 3.5k ohms
Max Output: 30Vrms 47k ohms load
AUX Inputs (high level):4 relay switched
Tape Loop: 1 in, 1 out with monitor switch
Main Output: 1 RCA
The Mode Switch on the front panel has 3 positions:
LO: This is the SuperLoZ Mode with an output impedance of 90 ohms. In this mode the 6H30 gain stage is connected to a compound 6922 buffer stage to create the very low impedance output needed by some Solid State power amplifiers. In this mode the Peach will easily drive a 5k ohms load, or an extra long cable run.
HI: This is the HiZ Mode with an output impedance of 3.5k ohms. This is the shortest, most elegant signal path using only the 6H30 Class A gain stage and one capacitor to the output of the preamp. This mode is intended to be used with amplifiers that have an input impedance > 100k ohms, such as typical tubed amplifiers. We often refer to this as "BlueBerry Mode" as this is the same line out as the BlueBerry Xtreme.
HT: This is the HT bypass mode, or Unity Gain mode. In this mode the HT INPUT is switched directly to the output jacks as a "straight wire" bypassing all internal Peach circuitry including the volume controls. If you connect the FRONT outputs of your HT pre/pro to these inputs, you can put the Peach in HT BYPASS and control your front amplifiers from the HT Pre/Pro, making it very easy to use a premium amplifier for the front channels of your HT system as well as your music system. NOTE: The Peach must be ON to use the HT mode.
Outputs: Stereo via RCA plus
Tube Compliment: one 12X4, two JAN Philips ECG 6922 and, one 6H30
Dimensions: 19 x 6 x 12 (WxHxD in inches)
Weight: 18 lbs.
Obviously, I should have also noted, perhaps more importantly, that one may or may not like the sound "coloration" per se provided by the Mullard/Brimar combo. I place quotes around the word coloration because some consider it a departure from the reality of so-called unamplified music. In most instances I would reject such a claim, since widely varying colorations are found from concert halls to open air venues(with effects produced by wind, humidity and air temperature)as well as being associated with equipment that involves the recording and reproduction of sound in the studio, audio salon and home. Further, this may raise questions regarding the validity and/or meaning of the word neutrality.
To answer your question, tube rolling can affect bass to a minor degree. FME, bass is mostly affected by the room and speaker location. Smaller bass adjustments can be had by equipment, amps, preamps etc. Smaller yet bass adjustments can be had by cables and power cords. Tube rolling comes in next, and probably last for bass adjustments. You can find some tubes that may have some minor affect on bass. In my tube rolling experiences, I've noticed most differences in tubes lie in the midrange, high's, soundstaging, and aspects like that. Bass to a much lesser degree.
I might add that a change in speaker cable can assist in adding incremental bass as well. As mentioned earlier I noticed an increase in bass. Let me add that the bass was tighter and somewhat deeper. It was NOT and increase that
created a totally new sound it just enhanced. I may have mislead some by a less descript measure of improvement.
My answer was directed at your question and the simplest answer is, yes. The amount and degree will depned on your total system and in some cases the answer could be NO.
FME, it helped.
I am using low z have not tried the hi z. I thought it was for tube amps. The builder of these speakers suggested putting more poly inside the speakers for more bass response, anybody tried this? also the speakers are 3 way speakers but are on the large monitor size being 23.5 tall and 9.5 wide and 11 deep. I only have them about 9in off ground at this time on some inexpensive stands, but plan on getting better stands and raising them 24in off ground. I don't think the speaker have but about 80 hrs on them and recommended breakin is 100. So we will see, they are sounding better all the time though. thank you gentlemen for all your info. Scott