Hovland caps VS Auricaps

I have linestage preamp base on 3 tubes 12AU7, and I already upgrade the output coupling capacitors with auricaps 2.2 uf/400 volt with great result i.e. the base was tight and nice treble.
I got another Line stage preamp (same type) with
1. Output coupling capacitor with hovland caps 2uf/400 volt
2. Replace all the resistors ½ Watt regular resistors with 1 Watt PRP resistor
3. Replace stock diode with fast recovery diode on power supply
4. Bypass on power supply with 1 uf/400
The result was more realistic on midrange & treble but I lost the base compare the preamp with Auricaps.
How to get more on base?
Do I have to put hovland caps 4uf/400 or increase the value of by-pass capacitors?
Is there any capacitor that will increase the low freq with nice real midrange and treble?
I need advice or any body with experience on this matter.

Best regards,
Allow those Hovland caps 140 hours or so of break-in. The bass will flesh out much more after then. You'll hear gradual improvements after 50 hours. The Hovlands seem to take longer to break in than the Auricaps. Personally I prefer the Hovlands in my preamp. Increasing the capacitance will lower the bass roll-off but it might not necessarily improve the bass quality. It also depends on the impedance of your amp inputs. Anyway, I'd be interested in your impressions after the Hovlands have burned in a while.

My amp is VTL MB125 with Input Sensitivity / Impedance
0.75 V / 145KW.
What happen if I put another 0.68 uf/400 or 1 uf/400 hovland caps in parallel?
I think I have wait until 150 hours to get fully broken.
Thanks Sherod , I will let you know.

My amp is VTL MB125 with Input Sensitivity / Impedance
0.75 V / 145Kohm.
VTL TT-25 with Input Sensitivity / Impedance
1.16V / 120Kohm.

There is a formula for determining what roll-off point you want for your bass. I'll try to do a search later to give it to you. Besides the input impedance of your amp, which in your case is high at 145K ohms, you'll also need the output impedance of your preamp to insert into the formula. As to bypassing or paralleling your preamp output caps, I wouldn't recommend it. I have several reasons for this opinion. I would firstly give your current 2.2uf Hovland caps ample time to break in to get the full measure of their sound. If you feel that after determining the bass roll-off point that you want a lower cut-off point, (assuming you like the overall sound of the Hovland), replace the 2.2uf value with a higher value single unit( not bypassed)Also, very important, you need to make sure that the voltage of the capacitor is equal or higher than the value supplied by the manufacturer. There is a wealth of information regarding DIY stuff on various forums in Audio Asylum. Doing a search there will give you many hours of reading and learning. Perhaps others more technically knowledgeable on electronics can make some suggestions for you. I am more an audiophile than a technician. My DIY is very amateurish and limited to some basic soldering in of caps and wire harnesses. Be careful but have fun. If by chance, after listening to your system once the Hovland caps are fully broken in and you still don't like their overall sound, you can always put back in the Auricaps and they also will improve with some burn-in time. I have found that most of the top polypro-type caps need at least 100 hours to fully form in your circuit to sound their best. Good caps are like new cables. They need time to break in. Patience is a virtue here.
Thanks for your information and I am still learning about system synergy and make the sound close to realistic.
I like Hovlands much better on the midrange and treble over Auricaps, but let see what is happen after fully broken.