BeePre Input Transformer and Other Questions

[KandB]

Hello all I am a newbie to this gear; this forum sounds like a great resource; before I go any further let me wish you all well in 2015

1. The valve gear (BP and monoblocs) that I purchased last month was purchased and assembled in early 2014.

2. Is this a modification that is needed to upgrade the BP or is it from a specific condition/symptom of the preamp.

3. I have now listened to my 300B s for 30 hours plus the 10 hours of use before my purchase. I have a crackle out of the BP on one side only, I swapped the interconnect at the monobloc and the sound moved to the other speaker so I assumed the BP was the source. I have removed all but my oppo as an input with no change. tube issue?transformer issue? build issue?

My setup currently is the BP , monoblocs, oppo 83( allows me a subwoofer feed), technics 1500( tweeked inhouse) with a Seduction tape amp( low output signal), and a Sony playstation/Thorens 166 mkll depending on what I will listen to . I have a pair of Klipschorn corner speakers for sound delivery.

I did have to add an isolation transformer for the BP because of an original hum, that eliminated the initial hum problem

Any help on the crackling or the value of modification of the input transformer would be appreciated.

I am not a builder/assembler but do appreciate the sound, thanks in advance



[ modified by fullheadofnothing to split out from an unrelated topic, and correct PB to BP ]

[fullheadofnothing]

The only reason to do the Input Transformer mod is if you have a balanced source (i.e. it has XLR jacks) you want to use. The Oppo, Seduction, and Playstation are all single-ended. You don't specify a phono stage that you use with your turntable, but most are single-ended.

Your crackling issue could be tube related. Have you changed tubes from side-to-side? It also could be a soldering issue, but the tube check is an easy first step.

[Doc B.]

It sounds like you need to talk to whoever you bought the amp from, and see if they had a similar experience.

[KandB]

Thanks for your timely replies, as time allows I will swap the tubes on the PB from side to side and see what happens. I already have the XLR balanced sockets in place. The original builder had no hum issues at all.

The Thorens is a MC cartridge so I do need an amp, as a sidebar I tried the seduction amp with the turntable and got a reasonable sound I suspect not optimal but ok. That addition will be at a low priority on my list. I am working on getting the gear and the setup right before any more gear purchases.

The reason I went with the Klipschorns and the tube gear was an epiphany of sorts, I had a SS amp and speakers ( Threshold 400 rebuilt by Ken Ealey and a set of Paradigm studio 20 speakers) and listened to a set of horn speakers/valve gear and was amazed at the difference and was sold on the idea. Retirement was in site so a decision was made and here I am.

Thanks again for your reply I will do the troubleshooting and get back on the result.

Are there different tubes/manufacturers that give a different sound output or are most of the PB tubes equal sound wise? - I do know that the pricing does vary - does the sound do the same?

[Paul Birkeland]

I already have the XLR balanced sockets in place. The original builder had no hum issues at all.

The XLR sockets on the stock BeePre are for balanced output, and do not require a transformer.  As mentioned above, they are not related to the crackling sound you're experiencing.

The Thorens is a MC cartridge so I do need an amp, as a sidebar I tried the seduction amp with the turntable and got a reasonable sound I suspect not optimal but ok.

The Seduction works well with moving magnet cartridges with an output level around 5mV.  Most moving coil cartridges are below 1mV, and would require a step-up transformer ahead of the Seduction for proper loading and signal level.

Are there different tubes/manufacturers that give a different sound output or are most of the PB tubes equal sound wise? - I do know that the pricing does vary - does the sound do the same?

They will all indeed sound a bit different, but I believe nearly all of the currently available 300B tubes have happy owners.

-PB

[KandB]

Thanks to all again I did swap the tubes on my BP as suggested and that solved the crackle issue.

I have an isolation transformer for the PB plus I used the monoblocs pots( apparently not correct)and reduced/eliminated the original problem - a hum.

If I used the adj of the isolation transformer and have a range of voltages is there value in having the PB operate under or over the 120V, tube life etc.

A further question on the Monoblocs - I have voltage adj pots  on the monoblocs, are they to adj for hum or to set the tube voltage or both. I was told by the builder that they are to adj the voltage for the tubes to the lowest possible voltage. They did help with reducing the hum before I talked with the builder. Is it improtant to adj the tube voltage? Would that then be a regular ongoing check and adj weekly or monthly

Thanks in advance

[fullheadofnothing]

You have not said what the amplifiers are, only that they are monoblocs. It seems that they are Paramounts from context. If they are not, then please specify and I will clarify.

Paramounts have hum balance pots on the top of the chassis. These are there to minimize the hum from the filaments of the output tube. For best results, let the amplifier warm up for a half hour or so before adjusting. Ideally, the input should be shorted for this adjustment. You can adjust by ear, but for best results, put a volt meter set to read AC mV on the output. The center of the pot will be where it works best, work it one way until you hear/see hum, then back the other way until you hit hum, and so forth until the hum is minimized. You may need to touch up this adjustment as your tubes age, and definitely if you change tubes.

Paramounts also have a potentiometer on the driver board,  which sets the plate voltage of the driver tube. I do not believe this is what you are referring to. This would need to be adjusted if you change driver tubes. Consult the manual for more information.

Is your isolation transformer a variac...? What is your incoming AC that requires reducing voltage? The power transformers are designed for 120V and the circuits are tolerant of some variation.

[KandB]

Hello thanks for your reply. I have the Paramount monoblocs. The pots are on the surface plate of the Paramounts and from your post I understand that they are hum adjustments(?) which maybe done by listening or for an optimum setting a ACm V check is the best method to check the the tube status.

I have an isolation transformer not a variac. I am able to select a scale from 110V to 130V(outputs) from a 120V source( in my case it is 116V source). The question is when I  adj the voltage to the BP through my Isolation Transformer(IT) is there a benefit to be above or below 120V. The selector on the IT is at best a plus or minus 3V range on 120V so I can set 123 or 117.

Thanks in advance

[Paul Birkeland]

123V will be a better place to be.

-PB

[KandB]

Thank you for that, I will sit back and enjoy the music

[Grainger49]

Most of us in the states have greater than 120V out of the wall.  The extra few volts are not going to break down the transformer insulation, it is insulated very far above that.  It does put out a few more volts out the high voltage winding of the transformer and an additional fraction from the heater winding.  But that is all inconsequential. 

I've got almost a constant 124V AC out of my outlets.  I use a PS Audio P300, very old, regenerator and run the system on 120V.  Before the Eros I ran it at 117V as that is what the Foreplay 2 was specified at.  When I got the Eros I bumped it a whopping (joke) 3V so that the voltage regulators and constant current sources had no chance to be starved of the energy they need to operate properly.

That last sentence is the crux of the matter.  Don't starve the active circuits.

[KandB]

Caucasian Blackplate: responded about my attempt to use the seduction tape preamp on my MC turntable - the suggestion was that I would have to add a stepup transformer to increase the feed from the  1mV to 5mV to be able to get a full listening field(my words).

Is that what I would neeed in the daisy chain for my turntable  - turntable, stepup transformer,  seduction then PB and then the P monos?

I do appreciate having access to this the site, thanks again

[fullheadofnothing]

Whether or not you need a stepup depends on the cartridge. Either way you would need a phono preamp, not tape.

[Paul Birkeland]

Caucasian Blackplate: responded about my attempt to use the seduction tape preamp on my MC turntable - the suggestion was that I would have to add a stepup transformer to increase the feed from the  1mV to 5mV to be able to get a full listening field(my words).

Yes, 1mV isn't enough signal for the Seduction to work properly.  The Seduction Tape Preamp is also not a suitable choice for RIAA playback.

Is that what I would neeed in the daisy chain for my turntable  - turntable, stepup transformer,  seduction then PB and then the P monos?

Yes, that is what the signal chain would end up looking like.

[KandB]

To all who responded thanks again.