tubelab simple se: increasing the drive

[pforeman]

When I have the simple se hooked up to a tube preamp it is giving full output with the volume control at about the 12:00 position.
When I have (the other) simple se hooked up that has its own volume control driven by a cd player the volume control is all the way up, and possibly not quite as full volume as when driven by the preamp. Even less loud when drivin by a mp3 player.
Also, not sure but the power transformer is warmer (still not "hot").
My questions are:
Does the amp (power and output transformers) work harder to make music of a certain loudness when not using a pre amp ( or using a unity gain preamp)?

Is it possible to switch the 12AT7 tube for a slightly higher gain tube (12 AX7 or 5751) for higher gain if not using a pre amp?
Thanks,
Paul

[Cassiel]

To the first question: LOL
To the second: yes, if cd output not enough to get max watts a switch to 12ax7 would help.

[Cassiel]

On a second thought I think something is wrong somewhere. If I'm not mistaken the amp's sensivity is pretty good, almost the full mu of the driver tube (CSS). What's your output tube ?

[rknize]

I am scratching my head here, but I think you are comparing apples to oranges. The SSE has a lot of gain...plenty to drive to output stage well into clipping using "line level" inputs. What size pot are you using the SSE #2? I suspect that either it is not hooked-up right (wiper should be on the amp side) or the portable player doesn't have enough drive to get past the lowered input impedance from volume control.

Are you asking why the two SSEs seem to have different gain or why the CD player can't drive the amp? What happens if you connect the CD player to the amp with no volume control?

[pforeman]

The simple se I made with a volume control is for my brother. He plays his music pretty loud. So I am using KT88's and 6550's. I'm using a JJ (Tesla) 12at7.
Pretty sure it's wired correctly. It is a 50 Kohm pot.
It plays quite loud. I can easily hit 105 dB peaks on Open Baffle (audio nirvana) with MJK's H frame 18" woofer
( with B&K plate amplifier below 160 Hz).
It's just that with the vol pot all the way up, it's possibly not quite as loud, as with a pre amp ( with vol control half way up-- any higher and distortion is quite apparent).
Not a big deal, as it does sound great, and does play quite loud. I don't usually listen to music that loud, but my brother does. If so, is he completely out of headroom, where as if using a preamp, or different input tube, would the headroom (when playing loud!!) be better?
Thanks,
Paul

[pforeman]

cd player doesn't have a vol control, so I can't connect it to the amp that doesn't have a vol control
Thanks,
Paul

[rknize]

It sounds to me like your portable CD player does not have enough drive and/or enough gain, but you could confirm this by hooking the 2nd amp up to your preamp. If it works fine, then you know. What sort of CD player is this? Like a Discman or something?

I've been running my SSE directly off of my SqueezeBox for several months now while I renovate my basement. About 80% volume puts the amp into the onset of clipping. At 90% the clipping is noticeable.

Are you running the output stage in triode or UL? With or without CFB? If you run UL with no CFB, you will end up with more overall gain.

[DougL]

Originally Posted by pforeman

Not a big deal, as it does sound great, and does play quite loud. I don't usually listen to music that loud, but my brother does. If so, is he completely out of headroom, where as if using a preamp, or different input tube, would the headroom (when playing loud!!) be better?
Thanks,
Paul

If your brother wants more voltage gain for his system, it is better to add a (tube) preamp. I would look at CCDA from John Broskie's Guide to Tube Circuit Analysis & Design.

Changing the input tube on a Simple SE will probably have major sonic impact.
Off the top of my head, here are some of the challenges.
A 12AX7 can only have a couple of mA of current. This is probably not enough to drive a 6550 miller capacitance, thus rolling off the high frequencies to one extent or another. Adding a source follower to compensate is possible, but may require an extra power supply.

Point is, this is more than a tube swap. its a partial redesign. George could tell you more, but that's my best guess.

HTH

Doug

[tomchr]

Are you sure the preamp has unity gain with the volume control past 12 o'clock?

If the max gain of the preamp is indeed unity gain, it sounds like the volume pot of the SimpleSE either isn't wired correctly or is loading the source too hard. The resistance of the volume pot should be on the order of 22~100 kOhm.

~Tom