Tube gear for sale

fredv

Both are singing; however, not quite done..
The left channel of the pre pops once for awhile. Maybe a bad tube, will need to investigate. One of the output tube of the amp wouldn't bias without an input connected. It would jump from 0.65V to over 2.3V, don't have a clue what might cause it.
The amp is working fine overall, but it has a hum and a buzz that can be heard from 3 feet away especially at this hour. Considering my speakers are only 87dB efficient, this can be quite annoying to more efficient speakers. This amp is definitely not considered as quiet.
Based on the last 45 mins of evaluation, I can say:
1. The ML-20 seemed to roll off the high a touch too soon. The Transcendent Sound Grounded Grid preamp has better imaging and sound more lively.
2. The PP-150 sounds quite clean, and as other ex/current McAlister owners said, the bass is very tight and deep. It is deeper than the TAD-60 but on par with the TAD-1000 with 6550.
3. ... ah, too tired, maybe later :-)

madmax

Cool, I'm glad to see you getting this monster up and running!
madmax

fredv

I have it hooked up a pair of Dahlquist DQ-10's which don't go that low, around 40-ish range. The DQ-10 is also very power hungry but 8 ohm. The comparison to the TAD's were not A/B, all based on memory. I might have use the wrong word to say the bass was deeper as almost any amp can go to it's range. It is more like the presence of the bass at the 40-ish range is more vivid. This PP-150 actually uses 6LB6 output tubes, not the EL509 or 40KG6. This is a slightly lower output tube than the EL509, but I don't think it is that much of a difference. What kind of preamp do you use? I wonder there is any possibility of impedance mismatch.

fredv

I have a Lite Audio DAC (the case looks very much like your pre!!), they are quite decent. In fact, this DAC is the source hooked up to the McAlister preamp. This is a tube pre. The impedance match shouldn't be an issue at all. If my measurement is correct, the PP-150's input impedance is 100K which will work fine most of the preamps. I fixed the ML-20 pre, and while I got the chance to crank up the volume a little bit, I did a back to back comparison of the grounded grid and ML. The GG didn't sound like having more mid-low to low than the TAD-60, and the high was a little bright. When I paired the GG and the TAD-60, it wasn't this bright. Putting back the ML pre, the kind of bass presence was back, and the mid to mid high was very sweet especially vocal. I didn't have the chance to try the ML and the TAD-60 combo, but from what I heard, the ML is a better companion to the PP-150. I will try out the GG/TAD and ML/TAD combo tomorrow.

Just curious, did you try to use the Lite Audio pre/PP-150 with a different pair of speakers? I wonder the "mismatch" is pre and amps OR amps and speakers.

fredv

Hi Anonymouse,

I have been fiddling with the amps. I played 3 different tube preamps (Grounded Grid, FVP5a clone, and ML-20) and 2 pairs of speakers (DQ-10 and Carver AL-III) with the PP-150 and TAD-1000. Yes, I fixed the ML-20 intermittent pops and the buzz of the PP-150. The PP-150 sounded the best with ML-20, both speakers. The TAD-1000 sounded the best with FVP5a, GG and ML-20 is a matter of taste. Even with the ML-20, the PP-150 didn't sound right, a little too much at mid-high to high. It was simply bright with the other 2 preamps, regardless to which pair of speakers. Not only that, the 2 channels were not balance, the ML-20 has balance control which helped. Another reason why it was preferable to the others. When I played the GG with the PP-150, I got the feeling of somewhat sloppy bass. If I focused on the low end spectrum, I could heard the bass was there, but overall, the excessive mid to high was so distractive that I could say the bass was mushy or weak. From what I experienced, I suspect your preamp may not be the best match to the PP-150.

This kind of bothered me. I trusted Victor, Rich, and Norm ears. Something wasn't quite right. Remember Peter said that tube rolling would not affect the sound of this amp. I remembered, so I didn't pay a lot attention to the tubes. When all other simple things are rule out, I turned my attention to the input tubes (the front outmost tubes). They were 2 very different tubes, one 6EM7 "thick base" and one 6EA7 "coin base". While they were equivalent, they could sound different at this sensitive position. So, I dashed out to look up my tube collection and found 2 GE 6EA7/6EM7 tubes, both had coin base, look like this . I then replaced both input tubes and powered up the PP-150 again. Oh my, all my complaint were gone. The 2 channels are balanced, and the excessive brightness disappeared. Granted, the PP-150 does have more mid-high presence than the TAD, but it is not considered as bright. At this point, the bass is very apparent and tight. Even with the 86dB 4 ohm Carver, the bass was well controlled. So, one quick experiment is to rearrange the 6EA7's and the 6EM7's; for example, exchange the driver and the input tubes. To me, changed out the input tubes did the magic to me. I hope this will work for you as well. If you don't mind to spend a few more bucks, you can buy a couple new ones from thetubecenter. When you buy, make sure you include a notes to Jack to pick the same brand for you.