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Author Topic: Does preamp size affect output level?  (Read 2043 times)

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assquatch20

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I've got a little Blackstar HT5 and I was running the fx send through a stereo tremolo into the rack unit. I've never had a dedicated power amp, let alone a stereo one, so I don't know if this is typical. The volume never overpowered the 5W. It may just be because they're not that far apart in max volume realistically but I feel like there's more to it. I need to experiment with a bigger amp and see if it ramps up a bit more to match. Pretty much I'm wondering if this is normal or if I have a poorly functioning power amp.
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rnolan

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Re: Does preamp size affect output level?
« Reply #1 on: Time Format »

Hey assquatch20, I'm not quite sure what you mean or quite how you've got this set up. (I've got a little Blackstar HT5 and I was running the fx send through a stereo tremolo into the rack unit), what rack unit ? are you returning into the HT5 to use it's 5w power amp  (and speaker if it's the combo) ?Your HT5 has 2 tubes, one is the preamp tube, the other is its poweramp tube (so you do have a dedicated power amp albeit only 5w.( Does preamp size affect output level?) not sure what you mean here, output level is a combination of things but mostly affected by the power amp (in your case 5w) and speaker(s) efficiency.  A preamp with more tubes can produce more gain and 'potentially' drive the poweramp harder, depending on the circuit.The HT5 is a nice unit but not very loud, good for bedroom style or possibly studio use (but then you'd probably use its cab sim outs direct into the desk.
I don't think you have a poorly functioning power amp, it's just not a very loud amp, 5w is not allot of power.
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Live Rig: MP2/MB1 > Alesis Quadverb > Alesis Midiverb 4 > Yamaha AM802 > B200s/Carvin TS100/DCM200L > ADA Split Stacks/Mesa P112s

Kim

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Re: Does preamp size affect output level?
« Reply #2 on: Time Format »

I assume   "rack unit"  =   ADA T100s ?   

I agree that it seems something isn't quite right.  The T100s should be very apparent that it is capable of being louder than the HT 5.
What speakers are you using?  I wonder if perhaps the Input signal to the poweramp is just not as high as it should be?   
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RIG OF FIRE:  ADA MP-2, Rocktron Xpression, Peavey Classic 60/60, Gator pedalboard, Rolls MidiBuddy, Dunlop 95Q wah, D'Addario Pedal Tuner. 4x12 cab w/Celestion Vintage 30s.
Mellotron/organ section:  EHX Mel9, EHX C9, Saturnworks A/B switch, Vox V860 volume, Crate Powerblock. 4x12 cab with Crate/Celestion speakers.
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HOME/STUDIO/COMBOS/STUFF:  Peavey JSX halfstack, Crate G60XL, Saturnworks Saturn Fuzz,  EHX Soul Food, ProCo Rat, Ibanez Smashbox, Saturnworks buffered splitter, Morley Tremonti wah, Peavey PV6, Korg DTR-1000, ADA MPC, Mr Black Bloodmoon.
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assquatch20

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Re: Does preamp size affect output level?
« Reply #3 on: Time Format »

I assume   "rack unit"  =   ADA T100s ?   

I agree that it seems something isn't quite right.  The T100s should be very apparent that it is capable of being louder than the HT 5.
What speakers are you using?  I wonder if perhaps the Input signal to the poweramp is just not as high as it should be?   

This is correct. I have a -10/+4dB on the fx loop that I have at +4. The pots on the stereo amp are very scratchy so they may be to blame. In certain positions it seems like it's not getting through. The Blackstar has nothing in the fx return, its power amp is keeping up with the ADA power amp somehow. As I increase the volume on the B* the ADA volume seems to rise as well. I need to test with a larger amp with fx loop and/or maybe a dB meter to be sure I'm not fooling myself with wattage:volume not being linear and such.

The speakers I'm using are a 1960A in the center off the B* and the ADA stereo power amp is feeding two split stacks. The B* has a stereo DI (stereo reverb) but I'd need a shielded stereo splitter cable of some sort to test it. The issue is it comes with cab emulation you can't turn off, but I do believe the dB switch affects the DI as well. It would be nice if the FX send had the reverb, especially if it were stereo, but maybe I'll get a cable and the cab emulation through DI would be tolerable. More likely I'm going to buy stereo effects.
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Kim

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Re: Does preamp size affect output level?
« Reply #4 on: Time Format »

The pots on the stereo amp are very scratchy so they may be to blame. In certain positions it seems like it's not getting through.

I'd start right there before anything else.  I've had numerous instances concerning volume levels that were not behaving properly and were simply just dirty and scratchy pots causing all the problems.    :thumb-up: 
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RIG OF FIRE:  ADA MP-2, Rocktron Xpression, Peavey Classic 60/60, Gator pedalboard, Rolls MidiBuddy, Dunlop 95Q wah, D'Addario Pedal Tuner. 4x12 cab w/Celestion Vintage 30s.
Mellotron/organ section:  EHX Mel9, EHX C9, Saturnworks A/B switch, Vox V860 volume, Crate Powerblock. 4x12 cab with Crate/Celestion speakers.
UPDATED DIAGRAMS
HOME/STUDIO/COMBOS/STUFF:  Peavey JSX halfstack, Crate G60XL, Saturnworks Saturn Fuzz,  EHX Soul Food, ProCo Rat, Ibanez Smashbox, Saturnworks buffered splitter, Morley Tremonti wah, Peavey PV6, Korg DTR-1000, ADA MPC, Mr Black Bloodmoon.
GUITARS:  Jackson KE3-DiMarzio Breed/PAF Pro, Jackson KE3-DiMarzio Breed/PAF Pro/nickel covers, Silvertone P-bass, '70s Gretsch Dorado acoustic.
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rnolan

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Re: Does preamp size affect output level?
« Reply #5 on: Time Format »

The T100S should be very loud and blow the B* speaker away.  Sounds like there are issues with the pots and probably the jacks.  Give them all a good clean and also the jacks on the split stacks, they can gum up if not used for a while.  You need an insert lead (stereo jack to 2 x mono) then you can test using the DI outs.  As they are for headphone/cab sim they will lack top end so you'll have to turn the treble up a bit to compensate.  If you buy a stereo Fx you should be able to use the Fx send into one channel but both outputs should work to plug into the T100S.
« Last Edit: Time Format by rnolan »
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assquatch20

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Re: Does preamp size affect output level?
« Reply #6 on: Time Format »

The T100S should be very loud and blow the B* speaker away.  Sounds like there are issues with the pots and probably the jacks.  Give them all a good clean and also the jacks on the split stacks, they can gum up if not used for a while.  You need an insert lead (stereo jack to 2 x mono) then you can test using the DI outs.  As they are for headphone/cab sim they will lack top end so you'll have to turn the treble up a bit to compensate.  If you buy a stereo Fx you should be able to use the Fx send into one channel but both outputs should work to plug into the T100S.

To be fair, the 5w amp is going through a 4x12 so they have equal surface area at least. I'll give it a cleaning and test tubes and such though. I think, according to Blackstar, I need a balanced cable for the DI. The speaker emulation is a bummer, but the stereo reverb might sound nice. Regarding the loop and stereo fx, that's what I'm currently doing. The only effect I have for now is a stereo tremolo but it is pretty fun. And to be fair it sounds great, it's like the power is scaled to match the preamp it's feeding from somehow. I wish someone that had one of these and a small amp could verify whether or not this is normal.
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rnolan

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Re: Does preamp size affect output level?
« Reply #7 on: Time Format »

The T100S output:85w per ch -> 4 ohm50w per ch -> 8 ohm (which I assume the split stacks are)25w per ch -> 16 ohmThey have 3 tubes per chan, 1 12AX7 driver (phase splitter) and 2 6CA7 (=EL34) power tubes
This should much louder than the 5w blackstar (double the volume takes 10 x the power ie 50w vs 5w). In your case you have 2 x 50w so add 3db to twice as loud. However, as the T100S input is just one 12AX7 phase splitter you need to drive it pretty hard as there is no additional gain at its input.
The lead you need for the cab sim/phones output is a standard stereo to double mono shielded lead (there's a wiring diagram in the B* manual showing the stereo end).  They are more commonly known as insert leads as that is what you use in the insert jacks on mixer channels.
I used a HT5 once for a soft rehearsal, nice amp, the reverb is very good BTW but the amp is not very loud and cant compete with drums.  I have a Carvin TS100 which is a modern equivalent of the T100S.  It competes with drums no problem and then some  >:D .  The speaker emulation is fine if you want to record or go into a desk live.  This is basically what the HT5 is designed for.

Recently we started to use my split stacks that had been sitting for a few years and the jacks were dirty and causing issues.
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assquatch20

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Re: Does preamp size affect output level?
« Reply #8 on: Time Format »

Here's the top of the power supply board:


And here's the underside:


Seems like the seller was less than forthright. Haven't checked the caps yet but there seems to be continuity from what's been checked so far at least. At this point I feel it is unlikely that the pots of two different channels are equally diminished. Rather I feel this is likely where the issue is, upstream.

You can see where parts have been jumped already. The black stuff came right off with a little pot cleaner but the traces have bubbled up in places. There's also some other added wiring, I think for the fan. I'm starting to wonder if I could recreate this board old school and make it fit. Hopefully won't have to though.
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