[mcgsxr]

Hello, I have just placed my JR order for a pair of these TEAC digital amps, in order to play around with my system some.  Border fees should prove a little nasty but these still retail for $480 each in Canada...

I feel strangely guilty playing with amps, since my 10 year old Sugden has done nothing wrong... , but I cannot resist checking this out - if I find the pair of amps unsatisfactory, I can build out a 6 channel HT from my recent Dell.

So, I have two 3 channel amps coming, and I intend to do some passive bi-amping, BUT I have no preamp as yet.

Questions.

1.  To burn in the digital amps, could I attach them to the Tape Outs of the Sugden (with a splitter to hit 2 channels of each amp) and deliver signal to them that way - my question is, do they have to have a load attached to their speaker outs, in order to burn in?

2.  Preamp suggestions on the cheap - I am looking at around US$200 max (cause I don't want to sell my Sugden yet) for this, what are my options?  Would a passive do (Luminous on the 'Gon)?  Would an older PS Audio passive do?  Are there cheap tube preamps in this price range?  Other thoughts?

3.  On the passive preamp front, does anyone have the specs for impedence etc for these tripaths?

Thanks for any direction that you can lend,

Mark

[MikeCTM2]

hi mark     yeah, i think you need to have speakers hooked up.  the amps gotta feel the load, work the speakers, to break-in.     for $200, i have an adcom gfp-565 pre-amp.  it was my first pre.  then i got the dodd audio entry-level tube pre for $450.   if you consider the dodd, you also have to consider good NOS tubes.  that can be $100-200.

[ABEX]

sive Preamp out of Ratshack parts for $15. If you want the info leave me a msg..

I have the parts,bbut have not put it together yet!

[JLM]

For $200, it's gonna be hard to find quality.

The Decware ZSP-1 is a "plate" tube pre-amp kit for $250, but the plate and a cabinet are extra.  

Do you need a pre-amp?  Do you have multiple sources?  Could just a volume control work for you?

[mcgsxr]

Thanks for the replies so far, I appreciate the help.

I really only have 1 source, but sometimes like to watch movies through the system too - about 2 times per month, so the cable swapping for that would be fine.

A volume control would be fine - do you mean building one?  If so, are there sites dedicated to such adventures?

I know that for US$200 I am barrel scraping, but that is where I have to start!

PM me with details about the Ratshack pre please.

I might soon be in possession of a passive PS Audio piece from the 80's, it has 4 inputs, and two sets of outputs so that would SEEM to work well.  My main problem is that I do not have any information about the impedence of the TEAC inputs, so I am not sure if it will overload the PS pre to have 2 amps running off of it.

How would I tell - would there be a rolling off of the highs?

Mark

[JLM]

Volume controls, look here:  http://tweakaudio.com/

[Passive Chappy]

See if you can find a used Creek OBH12 passive preamp.  Sounds great and should suit your needs well.

[TheChairGuy]

Well Mark, if you're reeeeally barrel-scraping for sound, don't reeeally need to cable swap much and willing to listen relatively fixed listening levels.....than inline RCA attentuators may do for you.

Price is right, $9.00 a stereo pair from Parts Express.  1,3, and 6 db cut.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=266-232

Or, Parts Express (and others) sell the Harrison brand (makers of FMods, RCA line crossovers)for $25.90 a pair.  3,6 and 12db cuts available.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=266-242

You eliminate a lot of IC and preamp 'gunk' in the way from your CDP to amp in using these.

They are helpful in evaluating any pre you buy in the future...you can tell, pretty quickly, how much 'sound' any pre adds to the system.  Simpler is often better, but a bit painful on the ergonomic end of things.

Good luck, there is a world of choices out there....even at $200.

[mcgsxr]

A good suggestion ChairGuy, but with a 7 month old daughter, the listening levels tend to vary, depending on her relative proximity and consciousness!

I have received some information about building a passive pre from Rat Shack parts, that will be plan B.  I am still hopeful that an 80's PS Audio passive will be mine, and with that I can play around with cable length etc.

If this really strikes me as a wonderful sounding combo (passive pre plus tripath amplification) I can build out a DACT passive that will match the sensitivity of the TEACs perfectly, once I sell my integrated.

Thanks for the ideas,

Mark in Canada

[JoshK]

What kind of input connectors does this amp have?  3 RCA inputs?  If so, I can think of some nice fun projects for a pair of these!

[MaxCast]

Bottlehead Foreplay.  Tubed, plenty of gain, kit form  = $160.

[nhtran]

Which Teac amp uses a Tripath output stage?

[Occam]

1. To burn in the digital amps, could I attach them to the Tape Outs of the Sugden (with a splitter to hit 2 channels of each amp) and deliver signal to them that way - my question is, do they have to have a load attached to their speaker outs, in order to burn in?

2. Preamp suggestions on the cheap - I am looking at around US$200 max (cause I don't want to sell my Sugden yet) for this, what are my options? Would a passive do (Luminous on the 'Gon)? Would an older PS Audio passive do? Are there cheap tube preamps in this price range? Other thoughts?

3. On the passive preamp front, does anyone have the specs for impedence etc for these tripaths?

1. If you believe is such things as 'break-in' (I do), you need to run some current for  a period of time though the ouput stage(s). You need to put some noise or music through a load, speaker(s) or properly rated resistors. Ohms law is immutable. If speaker, and you want to minimize the neighbor annoyance, reverse the leads of on one of your speakers, and play a mono signal though stereo speakers placed face to face. Much of the sound will be cancelled (180degrees out of phase).

2. Mike's offer of a Adcom GFP-565 seems like an excellent choice.  A very good pre, and even better as the tripath 2050 chipset defines itself as having blocking cap in its inputs, so you could run the GFP in 'LAB' mode, sans its own output caps. I believe it can also be switched to a 'passive' configuration. If that switch provides a buffered passive, so much the better; see below. Dunno the Adcom's Bluebook value, but if you view this as an interim solution, ease of resale should be important, where the Adcom would have a large advantage over kits, BottleHead, AKSA, etc....

3. Whatever the Teac's input impedance, 2 equal input impedances in parralell are seen by the source as 1/2 the impedance. Parralell 3 inputs and it will be 1/3rd the impedance. Assuming the impedance is between 15 and 50kohms, at the lower end, 2 or 3 inputs in parralell might present substantial 'drive' problems for a passive pre. (there is a review of the Teac in the current? 'Audio Ideas Guide', which I've no access to in Brooklyn, but it might provide the input impedance).
A passive(unbuffered) pre might be problematic for driving parralelled inputs,[as well as a non cathode follower tube pre] and long capacitive interconnects from the passive to the amp are a no-no. After you've sussed out  the input impedances, you might give the folks Boulder a call to see what sort of load their LT136X? output opamp on your modded D/IO can drive.

'Be careful out there!'' Hill Street Blues

[mcgsxr]

The TEAC in question is the 3 channel A-L700P.  It is a tripath amp, driving 30x3 at 6 ohms.  US$99 each at JR's.  It is compatible with 4-8 ohm loads, according to my research.

Occam - Thanks for the info about break in, and guidance around pre amp suggestions.  I just won a PS Audio IV Passive pre on eBay (CAN be used active, but does not include the power supply), so I will explore this first.

I do think that the Adcom is a decent deal, and for resale, it would be a great way to go.

I have emailed TEAC to ask them about the input impedance, and should go buy that Audio Ideas Guide issue, so I can read about Andrew Marshall's experience with one of these amps.

The PS Audio Pre has 2 sets of RCA outputs - do you still perceive that this will 1/2 the input impedance of the TEAC, or since it has 2 sets of outputs, is it designed to drive 2 amps?

Lastly, let's suppose that it is NOT designed to drive 2 amps, and the TEAC is 1/2 the input impedance - WHAT will happen?  Will I experience rolled off highs?  Reduced dynamics?  Thoughts?

I will use sets of 0.5 meter IC, likely Bolder M-80 (Hey Wayne... ) when I can afford them, and find that this combination works.

I will check with Wayne about the smART op amp part of your post.

Thanks to all who have offered advice, and those who will choose to do so, I will report back on how this comes together, once I have had all the shipped goodies arrive.

Mark, now anxious in Canada!

[mcgsxr]

Well, the TEAC amps will arrive on Monday, but I am unlikely to receive my pre amp for 2-3 weeks, so there will be some delay in getting my opinion on the sound of these back to those interested.

I spoke with a service rep at Teac today, and was told that the input sensitivity of the amps is 1v@47K ohms.  So, with two in parallel that should have me around the 23500 ohm point.

Wayne at Bolder (always supportive) mentioned that the opamp in the smART runs an output impedance of 221 ohms, and delivers around 2.3 volts.

The PS Audio preamp specs are as follows:

Model: PS IV Serial Number: 1351 IV
THD I/M at 1 v rms: 0.01% or below 20/20 Khz
Signal to Noise Ratio (mm reference to 10mv): 88dB
Signal to Noise Ratio (mm reference to 1mv): 80dB
RIAA Curve Accuracy: 0.1 dB 2hz/20Khz
Input Capacitance: 50 pf
Input Impedance: variable Phono Input Overload (mm): 160mv rms Phono Input Overload (mc): 10mv rms
Max. Level Before Clip: 16v rms
Output Drive Capability: 600 ohms or higher

I intend to use 0.5 meter cables (likely Canare or Belden to get started, then Wayne will no doubt convince me I NEED to hear a new creation...) so cable capacitance should be limited.

I have received PMs from several (thanks to all) helping me understand that I am likely to hear rolled off highs, and reduced dynamics, IF I overload the outputs of the preamp.

Do those that can interpret those stats together have a thought on how this will all work?

I know that I WILL find out, once it is all assembled, but if there is something glaring that I can avoid or prepare for, it would be fantastic if you could take the time and help me learn about this.

Mark

[Occam]

Mark,

Unfortuneately, the specs, save for the last 2 about the PS pre, refer to the phonograph inputs and capabilities [by reputation, the PS preamps have fine mm/mc capabilities]. But as you evidently don't have the power supply for the pre, you're presently constrained to using it as a passive pre, and cannot take advantage of the phono capabilites, nor its nominal stated output capabilites, those last 2 specs, output drive voltage and load.
Regardless, the intrinsic passive attenuator in the pre, assuming some nominal impedance betwwn 10 and 50k, should not be problem, betwixt and between your Boulder smART and the 23.5k load presented by 2 paralelled inputs of the Teac. That is, assuming those .5meter interconnects are not 24 twisted pairs of cat5...

If you ultimately wish to try your pre in active mode, either for phono use, or those stated drive capabilities, you might try to contact either Paul McGowan at the reincarnated PS Audio, or Stan Warren whos ph# is floating about somewheres on the board, to get the powersupply requirements. As these are long out of production, either might be willing to send you the schematic. (Paul & Stan, get it...?)

[cjr888]

Well, the TEAC amps will arrive on Monday, but I am unlikely to receive my pre amp for 2-3 weeks, so there will be some delay in getting my opinion on the sound of these back to those interested.

FYI - there is variable control of each channel on the back of the Teac that you could use as volume control for the time being...  Little, little knobs, but...  I have a unit that's been sitting around here since my initial post regarding the Teac.

[mcgsxr]

Thanks Occam - I did speak briefly with Paul, and he mentioned that he thinks there is a 10k Noble pot in that pre, it has been a while!  I am reassured from several angles that this configuration works at least on paper - the listening will come in time, and that rules the decision in the end.

GREAT call on the small volume controls on the back, I have been reading a pdf of the owners manual, and looking right at those, not even thinking that they are the natural way to control volume during the break in phase with those amps, and a wonderful way to at least get a "fresh out of the box" impression on their sound.

Have you decided not to use your TEAC cjr888?

Mark

[cjr888]

Livingroom was being renovated for much longer than it was supposed to.  In that period of time, I continued to acquire gear....too much gear.  Some is being parted with without listening to whatsoever, per my better half, and some I haven't had any time to really give a chance.  Currently enthralled by the ugliest amplifier I have ever owned -- a custom 6sn7/300b with vintage transformers form a local builder w/Tungsol roundplates and Sophia/TJ meshplates so haven't had a chance to listen to the Teac outside of a couple quick times, and everyone knows what they sound like out of the box..

Nice looking little units though, and plenty of room to mod them if needed.

[geofstro]

Hi,

Just joined these forums. I've been reading a lot about Tripath based amps and other digital amps here.

I have a Powerwave and it's sounds surprisingly good considering the cranky speaker breakout connector. I was put onto it by Ed Schilling from the Horn Shoppe. I have a pair of his horns and he kindly agreed to send me a PW with them.

Now I have one Teac amp on order, since it looks like a promising amp.

I was just wondering if anyone has tried using two of these as mono-blocks.

Seems like an intruiging possibility to me. Although, admittedly the power would be limited in comparison to using two of them in bi-amped mode, if you have speakers that are sensitive enough in your room that 30wpc would be adequate then it might be worth a try.

Afterall, only a limited number of stereo amps are configruable for mono operation; but this amp, having a center channel, would allow each of two amps to be used as a mono amp, using the center channel of each amp only and leaving the L & R channels disconnected. This would have the benefit of separate amps, seperate PSU's, etc.

The only disadvantages is that you would still be limited to 30 watts for each channel.

If anyone has tried this, please let me know. If it worked out well, I may order a second amp.

Thanks


geoff