Trying different tubes in MV-52

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sailpoint
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Trying different tubes in MV-52

Post by sailpoint » Mon Feb 08, 2016 11:58 am

Hi guys,

I am brand new to this forum. I recently purchased a MV-52 in excellent condition that is using electro harmonix el34 tubes. I understand why people love tubes. Listening to this amp I am astounded how beautiful vocals and midrange instruments sound with it :) But I do have one wish though in that the bass performance is definitely rolled off with this amp. I had read on other boards that the CJ amp's sound can change dramatically with different tubes. I've read that 6550 tubes offer better bass performance and I wanted to try them out. Because I'm brand new to tubes I'm reading up on this now and wanted to ask if it is okay to use 6550 tubes in my MV-52? Also is it worthwhile to replace the other tubes in the amp as well from a sonic perspective? I listen to mostly rock and jazz and though I love the warm midrange, I do miss my bass and am looking for a better balance in the sound.

Thanks!

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Joe Appierto
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Re: Trying different tubes in MV-52

Post by Joe Appierto » Mon Feb 08, 2016 10:22 pm

The MV-52 was designed to use EL-34 tubes and you shouldn't use 6550 in their place. The electrical characteristics of the two are totally different. The 5751 and 6CG7/6FQ7 small signal tubes will affect the amp's sound depending on what you place in those positions. What brands are in there now? Hopefully someone knowledgeable about this amp will chime in. I've owned the Premier 11A and 140 models but not yours.

Another thought. This amp is about 35 years old and its capacitors most likely have a useful life of 20 years, maximum. Do you know if any work has been done to replace any of its internal parts? If not, this might be where you want to start.
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Re: Trying different tubes in MV-52

Post by sailpoint » Tue Feb 09, 2016 12:42 pm

The Small tubes look to be GE though the image of them is not clear. I did not realize CJ offered a capacitor upgrade. I'll go check this out too. Thanks!

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Re: Trying different tubes in MV-52

Post by Joe Appierto » Tue Feb 09, 2016 6:07 pm

The C1 Capacitor Upgrade made an improvement IMO to my Premier 140. Depending on the model it can be an expensive option. Depending, you may wish to have c-j just replace the original caps with the same or like type of capacitors.

GE was what they typically used in their models at that time. Normally JAN (Joint Army Navy) tubes. Still wish that someone familiar with your amplifier would express his opinion. With the Premier 11A I owned that used GE JAN 5751 and 6FQ7, I found just about any other type (including GE non-JAN tubes) of NOS (New Old Stock) small signal tubes were more to my liking.
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Re: Trying different tubes in MV-52

Post by Big Dog RJ » Wed Feb 10, 2016 3:23 am

Hey sailpoint,
Nice to know that you have a mv52, a real cj classic I may add or at least one of their classic designs. The main rule of thumb, if an amp is designed around a particular type of tube- do not change! Changing then in anyway can cause harm to the circuit and the amp overall.

Having said that, cj along with a few others do allow for tube replacements. For example the majority of KT series tubes can be interchanged, from kt88, kt90, kt120 or even the 6550 and its various iterations. These tubes are referred to as power linear pentodes and have very similar topologies with marginal variances in plate current and heat dissipation. Voltages across are relatively the same more or less.

The EL34 is known as a true triode in push-pull configuration, it's current and voltage parameters are very different compared to the pentodes or other power beam tetrodes.

The mv52 along with the majority of the mv series wasn't designed for impressive bass, rather its midrange and smooth highs were its main attributes. The mv series had that very special warmth and golden musical glow of cj amps known back in the hay day. Advancing 20 years on, the mv60se version was able to produce that solid bass and even more refined using the kt120 output tubes. Now cj offers the classic60se which has surpassed the overall performance of the premier11, mv60se, lp66s along with their previous 60-70 w/ch amps.

Having said that, doesn't mean those previous designs were inferior, they were all superb sounding musical instruments in their own right.

You will not be able to get better bass from the mv52, no matter what you change or replace. The EL34's cannot be substituted, but you can try and get perhaps newer input & driver tubes which will make the amp sound more crisp and perhaps better balanced. Bass will remain pretty much the same.

Over the decades cj went on to design higher quality and now offer sound with more realistic impact overall. But those previous designs were true classics and you just have to love what it can do.
Hope this helps.
Cheers, RJ

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Re: Trying different tubes in MV-52

Post by sailpoint » Wed Feb 10, 2016 10:11 am

Thank you so much for this info. This is my first tube amp so it has been very educational for me. I heard that KT77 tubes are compatible with EL34. Could I get a confirmation on that because I'm curious to see if that might give me an improvement. Also I'm wondering if anyone has upgraded the power supply for this amp and could give me their opinions and guidance on that. I love the midrange but I really do wish to eliminate the 'veil' I am hearing and make the sound crisper and better in the lows and highs.

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Re: Trying different tubes in MV-52

Post by Big Dog RJ » Thu Feb 11, 2016 3:20 am

Hey mate. You're welcome on info.
Re. To kt77 and changes/upgrading the power supply, I would consult cj directly. They may also offer you a different amp altogether and forgo the additional costs in upgrades and whatever else is involved with this product since it will take up Labour hours.
You could check with a few well known tech chaps if they are in or close to your area. I don't know of any personally at your end, only in melbourne.
I've heard good things about Bill Thalman, perhaps one of the forum members could advise on this.

I'm just wondering since this is a vintage model, whether the additional cost in upgrades may actually get you a better amp overall. ..
Let us know how you go. Have a good one,
RJ

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Re: Trying different tubes in MV-52

Post by cooterlee » Sun Jun 04, 2017 9:46 pm

sailpoint wrote:
Wed Feb 10, 2016 10:11 am
I heard that KT77 tubes are compatible with EL34. Could I get a confirmation on that because I'm curious to see if that might give me an improvement.

Several people have told you that the output tubes can't be changed. No matter how many times you ask, there will not be a different answer.

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Re: Trying different tubes in MV-52

Post by hornbeck67 » Thu Nov 23, 2017 11:31 am

CJ is now recommending Mullard re-issue EL34's for the MV 52 per a conversation I had with them on 11/22/2017. The last time I replaced the tubes in my MV 52 (3 yrs. ago) CJ had me purchase Electro Harmonix EL 34's.

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Re: Trying different tubes in MV-52

Post by Big Dog RJ » Thu Nov 23, 2017 11:30 pm

Yes, no doubt the Mullard EL34- superb tube!

These are the tubes CJ uses in their new CAV45 and Classic 120. Excellent depth, tight and fast bass and extraordinary resolution. The bass does not dig deeper then a KT120 or have that comparative midrange slam as a KT120 or KT150, but the midrange magic of depth and resolution is like no other. A very special tube indeed, which makes the CAV45 and Classic 120 an absolute pleasure to listen to. I think the most important factor with this tube is the level of musicality, just beautiful!

On another note, I was also thinking if you want to take your power amp to the next level? if you are able to get hold of a MV60, this would open up a whole new listening experience, and if you want to take that up a notch, try the MV60SE, another superb design in power amplification by CJ.

Cheers and have a good one.
RJ

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