A tale of two CJs and a Beard

[ronenash]

I am lucky to have three great tube power amps on my hands right now. Two from Conrad Johnson (LP125m SE and LP70s) and my trusted Bread P100 vintage tube amp. This past weekend I had some time and decided to do an extensive comparison between the three and see where each one shines.
But first for some details on the amps as they all use different output tubes and the Beard also uses a different design. The LP125mSE uses four KT120 per channel and is rated between 125 and 140w per channel. The LP70s uses the winged C 6550C output tubes and is rated at 70w per channel. The circuit design of the two CJs is very similar both using high quality Teflon caps as coupling and power supply bypass capacitors in addition to a significant dose of Vishay resistors.
The Beard is an amp I have in my possession for almost 20 years now. I have upgraded this amp myself several times and recently replaced all tube sockets to high quality ones, replaced all resistors in the signal path to Shinkoh resistors and replaced the coupling capacitors with paper in oil types and installed polyprop power supply capacitors. The Beard uses a balanced design to drive the output stage (much like the LP140) and is a dual mono design with two power supply transformers in addition to the two output transformers. It generates a healthy 100w from two KT88 (Gold Lion) tubes per channel. It’s a substantial amp weighing over 85 pounds (this is as much as the two CJ mono blocks put together). The Beard also uses some of the largest output transformers I have seen which enable it to output 100w @ 20hz. That's some serious bass output for a tube amp.
All amps were powered and warmed up driven in turn by the CJ ET3 preamp driving the Sonus Faber Amati's. I have used material from Jazz to Classical to some Rock as well.

My reference in this test was the LP125mSE which has been my main amp and reference for the past 6 month. The LP125mSE to me does everything right. It's very detailed but not in an offensive way. It throws a huge soundstage with every instrument and musician placed accurately within that stage, its extended at the frequency extremes and above all transfers music in an emotional way like nothing else I have heard before. The LP125mSE with good recordings and the right music can literally bring me to tears. To me this amp seems like it has no limits. See my previous short review of the LP125mSE in this forum.

The LP70s shows the same general signature of the LP125 with very detailed sound extended to the frequency extremes. The soundstage is smaller and less holographic than with the LP125 and the emotional factor although still there is less convincing than with the LP125. The back of the stage also is slightly less illuminated. It still has the signature modern CJ sound. Everything is there but in smaller doses. Note that some of these differences can be the result of the difference in output tubes. I did not take the KT120 from the LP125 to use in the LP70 because I wanted all amps to be powered up at the same time for assist in quick switching between them and I did not have an extra set of KT120s. Judging by memory (I have used the 6550C in the LP125 until it was fully broken in) the output tubes make a difference but a relatively small one.

The Beard was a big surprise in this review. I did not expect such performance from a 20 year old design. The first thing you notice with the Beard is that this is one powerful amplifier. It gives the impression that it is more powerful than the LP125, this mind you with only 2 KT88 per channel. The other thing you notice is that it goes deeper in the bass than the two CJ's. This must be the result of these two huge output transformers. The bass from the Beard is tight, accurate and extended. It's almost solid state sounding in this regard. This is one serious power house which explains the weight of this amp. One other price you pay for driving the pair of KT88 to their upper limit is tube life. The Beard will go through a set of output tubes faster than the CJ amps, probably 2-3 years per set when used as a main amp. Other notable attributes of the Beard compared to the CJ amps is the warmer tone, I assume this is the result of those PIO caps, and the change in sound stage perspective. The Beard bring the soundstage forward by a few meters. In width and depth its very similar to the LP70 but whereas with the LP70 the soundstage start at the pain of the speakers and extends back, with the Beard it starts 1-2 meters in front of the speakers and extends back from there. On some intimate vocal recording this effect works out really well and puts you right there near the vocalist. Ella Fitzgerald's Intimate Ella sound magnificent with the Beard. In this recording Ella sings very close to the microphone and the Beard highlights this fact. The detail retrieval of the Beard is very close to the CJ amps but not quite there. Noise levels are very low again not quite at the level of the CJ which have a better and more complex power supply circuit but the level of improvement here with the parts upgrade has been phenomenal.

I initially got the LP70 as a possible replacement for the Beard which I have had for a long time. After this weekend review I am keeping the Beard and returning the LP70 not because the Beard is a better amp because is not. The LP70 still has the edge and if I had to have only one amplifier to choose from between the LP70 and Beard the LP70 would definitely be my choice. The Beard stay because it give a different perspective and sound signature which I like very much. The LP70 is a scaled down version of my LP125 and as such does not really bring me anything new.
Second conclusion of this review is that the LP125mSE will continue to be my reference amplifier for the foreseeable time. It's such a great design that for me really does everything right.
Third and last conclusion from this review is that if you like DIY electronic work and care to learn how tube amps are designed and how they operate you can find great bargains out there of vintage tube amplifiers and restore them. The Beard was last manufactured in the early 80's and I have had it since the mid 90's. It was my first tube amplifier which has been my main amplifier for over 15 years, used with the CJ PV10 BTW. Restoring it has been fun and also very rewarding in the sound I get from it today. It's one serious piece of machinery and cannot be matched in its power and bass delivery. Now if I can only find another one to restore and use them as mono blocks. Imagine 200w from a pair of these…

I will be posting some pictures of the test setup this weekend.

[Joe Appierto]

What an excellent review/comparison! I'm looking forward to the pictures.

Thanks!

[ronenash]

Now for the pics...