[geetarman49]

we have considered otc vs otl & with a few exceptions, our sonic preferences are almost always otl + ocl (output capacitor less), but ocl almost invariably costs considerably more.
with this particular amp, trying to convert it to otc would hardly be worthwhile, imo.  this is not to say that we don't like otc amps; on the contrary, my buddies have quite a few vintage macs, pilots & citations.  it's all horses for courses ... or something like that ... lol.
 
the 6as7g is the 'perfect' tube for spanning low-z to hi-z phones for this amp.  it is also amongst the cheapest of the good output tubes available today (if you choose NOS rca 6as7g, which is very good).
 
here's what atma-sphere has to say wrt this tube:   http://www.atma-sphere.com/Resources/The_6AS7G.php
 
I have a couple of 6080w & 5998ts ---- I would still go with rca 6as7g, but i prefer my gec round-base 6as7g ... note that I don't recommend this unless you want to get real serious about tubes.
 
hth,

 

[kramer5150]

Cool thanks...
Curious, could you run a pair of these amps in a dual mono configuration... like how the 337 is essentially a pair of 336 amps in one chassis.  In the 337 each 6as7 dual triode outputs a parallel signal to each of its R / L headphone channels.
 
On the P8 it would be Like this:
>One amp for right signal and one amp for left signal.
>On each amp bridge the RCA inputs with either a "Y splitter" adapter, or hard wire the two channels on the board.
>On each amp bridge the output into one channel near the 1/4 TRS jack.
 
So each amp board is running a "mono" channel.
 
Take each mono amps output ground, and common ground them into a single 1/4 TRS jack.
Take each mono amps output positive, and connect it to the positive terminals on the 1/4 TRS jack.
 
Separate dedicated power supplies and volume pots for each channel.
 
Could that work?

 

[bala]

  if you are considering this unit w/o mods, then I would encourage you to consider the hybrid units offered by garage1217.com instead.
& if you are willing to mod, then I don't recommend the cased unit since it will obviously hinder the modding exercise.
 
stock, the unit is smooth throughout the midrange but with some lower end roll-off and some very mild upper mid to high grit.
a friend has devised a range of mods to eliminate all the issues that concern me, but I cannot post w/o his permission.
with these mods, I cannot think of a better all-tube amp for under $400 usd.
 
 

 
Thanks, though I would love to try the mods - time is an issue for me currently so I better give the 1217 amps a look.

 

[geetarman49]

if you do decide to pick up one of garage1217's amps, you might as well grab a few nos tubes as well from him - his prices are very fair.
if you intend to use the amp for both your iems and full-size hps, then check to see if the amp has a gain switch; this could be very useful.

 

[docentore]

What values should be used for bybassig output caps and replacing the red Wima's?


Received mine couple of days ago, I was waiting on tubes until yesterday and today when I was putting everything together it showed up that the transformer is broken. Can't imagine sending transformer to ebay seller in Honk Kong for RMA, postage cost will kill me.

 

[headtube]

Hi
 
I have the Little Bear P8 too. First I changed the Tubes: 2x NOS 6N3P-DR (90s?) and 1x 6H13C Wing-C 1975 NOS OTK.
Great open up and tight bass. Tried late 80s green GE Jan 6080. Not so impressive.
 
@ geetarman49  Your tuning looks very promising. Do you removed any parts from the board or just add these blue bypass caps? (Which type?) How is the improvement? What are these "4 big black lytics" your friend used?
 
Could you, or somebody else please provide some more detailed tuning pictures?
 
I ordered a second board too for try and error.

 

[meccup]

 
for $140 delivered this (little bear p8) is a bargain.  but you are right, there is a potential for some issues.
 
1. this ships as a flat-pack so the final assembly rests with you.  & depending upon whether you choose top-side component or bottom-side component pcb, power routing will change. hence, this explains why there is a male/female socket between the ac main housing (iec) & the xfmr.  i.e. end-user will not be required to do soldering.
 
2. the iec assembly IS fused.
 
3. the xfmr assembly bolts to the acrylic (clear or red).  if you accidentally overtighten (like I did) you will crack the acrylic .... in which case you reach for the bondic or superglue.
 
4. there are 4 output caps, all 'lytics --- at the least, these should be bypassed.
 
5. the 4 red wimas are indeed 0.1uf/630v coupling caps --- these too, should be bypassed, if not outright replaced.
 
6. amongst my friends & I, (with at least 4 pcbs) we have not experienced any egregious channel matching issues ---> you do need closely section-matched tubes, though.
 
7. to my knowledge current pcbs do not use those gold-colored metal power resistors --- instead, they are green-colored carbon resistors of considerable size.
 
8. I have used mine for up to 8hr continuously while running burn-in tests w/o issue.
 
9. the stock tubes, esp the driver tubes should be replaced --- i'm using ge jan 5670w.  for output, i suggest rca 6as7g for those on budget, otherwise gec 6as7g.
 
10. I agree ... emi/rfi may be an issue ... but I haven't experienced it ... ymmv.
 
11. the open chassis is both boon & curse:  boon for those into modding & curse, because the 'chassis' is rather flimsy.
 
12. I experienced two issues with my 'kit', both of which were rectified by the seller.  the acrylic panel around the iec mousing was cracked and some of the standoffs were not threaded sufficiently deep to accept the interfacing standoff.  if you're into modding, you will need longer standoffs in order to accommodate large caps - these are readily available on the 'bay.
 
hth,
 


even w/o modding i would be hard-pressed to find an alternative otl valve amp for less that sounds as good.

 

4. there are 4 output caps, all 'lytics --- at the least, these should be bypassed.
 
5. the 4 red wimas are indeed 0.1uf/630v coupling caps --- these too, should be bypassed, if not outright replaced.

 
As far as I can see, two of those red WIMAs are connected in parallel with those 4 output lytics caps... Which means that those output lytics are already bypassed (correct me if I'm wrong). 
 
My unit came to me with gold resistors (with a heat sync) attached to the alu box through thermo-conducting glue, from my point of view its a good design (although I'm not an expert). 

I also had an issue with channels balance, I felt that some of frequencies (a range) are tend to be more on left side rather than in the center. The cause of this was in one of the WIMA's caps, I noticed that one of them was damaged, so I replaced all WIMA's with auricaps. It looks like the problem has been fixed now.
 
And of course I have replaced terrible Chi-fi valves, sound drastically has improved. RCA tubes make the difference.
 
Anyway, I'm happy with this amp, it's sitting on my desk in the office helping me to do my duties  

 

[geetarman49]

this is a very old thread & i have not been getting any head-fi feedback with respect to 'new' replies -- consequently i did not respond in a timely manner ... my apologies.
 
of course, you are right ... replacing all wimas with better caps is a good idea.  the gold power resistor with built-in heatsink should be replaced --- my unit with green resistor is a later generation ... there are lots of alternative pwr resistors to choose from ... just ensure that the pwr ratings are either identical or higher.
 
i don't really have any more to add on this because i have since jumped into the deep end  (grace m920 + stax + stax + stax + stax) ..
 
cheers,

 

[geetarman49]

i am adding more pix for the benefit of those modding this unit ...
 

 

 

 

 

 

 

 

 
standoffs, along with the thumbscrews, used in the upper fotos are 20mm & 40mm -- readily available from chinese/hong kong sellers on the 'bay.
note the gap in the 5th pic - which occurs when you employ longer standoffs --- this creates a somewhat less than stable platform when plugging in the iec power cord.  you'll have to hold this to avoid breaking it when plugging in your power cord.   if i were to continue modding this, i would get a block of acrylic & 'slot it' to fit between the back 'panel' and the upper 'plate' -- then secure it with screws to the top plate.  this would prevent the pwr inlet from flexing and provide added strength to the entire structure.
 
you can also see evidence of cracking on the bottom plate where the mounting screw attaches the transformer -- note the addition of large washer, after the fact.
i added clear rubber/plastic stick-on feet from home depot.
 
WARNING --- do NOT perform the additional cathode resistor mod shown in the 2nd to last pic --- under certain conditions this puts the bear at its limits and increases distortion, iirc.

 

[ihavet0es]

I know this is an old thread but for my first post I want to thank you all especially kramer5150 and geetarman49 for providing a lot of valuable information on the P8. It's helped me mod my Little Bear P7 switching mode version of the p8 ($80!!!!). So far I've changed the 4 coupling caps to Audyn pure coppers (can't describe it just sounds a lot better), added bypass caps to the electrolytics (echoes are more echoey), increased capacitance of the filtering stage from 4x82uF caps to 4x220uF (more bass), and just this morning bypassed the filtering caps (bass less boomy but still powerful). I've done all the mods progressively and WOW what a positive difference! For future mods I have an Alps pot on order and plan to increase the capacitance of the output stage, then finally change out the stock tubes. I know I've spent more money on my mods than I have on the amp but I care more about the learning and sonic changes with each modification. As I don't know anything about electronics and audio equipment, I'm hoping i can get feedback regarding what I've done especially regarding the filtering as I don't know how it impacts the switching PSUs. So far my headphones and amp haven't melted but I'm sure I've made a mistake somewhere and could use any help/suggestions I can get. My DAC is a Topping D30 with a shunted Burson v6 classic and my headphones AKG K712 Pro. I listen to a mix of crappily converted mp3s, FLAC and (LOL) 1 128dsd file Barber's Adagio for Strings all through foobar w/asio, streamed content, and CDs from an old HK FL8550. Thanks everyone I wish I could share my excitement with you all!

 

[CADCAM]

I know this is an old thread but for my first post I want to thank you all especially kramer5150 and geetarman49 for providing a lot of valuable information on the P8. It's helped me mod my Little Bear P7 switching mode version of the p8 ($80!!!!). So far I've changed the 4 coupling caps to Audyn pure coppers (can't describe it just sounds a lot better), added bypass caps to the electrolytics (echoes are more echoey), increased capacitance of the filtering stage from 4x82uF caps to 4x220uF (more bass), and just this morning bypassed the filtering caps (bass less boomy but still powerful). I've done all the mods progressively and WOW what a positive difference! For future mods I have an Alps pot on order and plan to increase the capacitance of the output stage, then finally change out the stock tubes. I know I've spent more money on my mods than I have on the amp but I care more about the learning and sonic changes with each modification. As I don't know anything about electronics and audio equipment, I'm hoping i can get feedback regarding what I've done especially regarding the filtering as I don't know how it impacts the switching PSUs. So far my headphones and amp haven't melted but I'm sure I've made a mistake somewhere and could use any help/suggestions I can get. My DAC is a Topping D30 with a shunted Burson v6 classic and my headphones AKG K712 Pro. I listen to a mix of crappily converted mp3s, FLAC and (LOL) 1 128dsd file Barber's Adagio for Strings all through foobar w/asio, streamed content, and CDs from an old HK FL8550. Thanks everyone I wish I could share my excitement with you all!

Hope you see this...
I ordered the Little Bear P7 and was loving it for about a month then it died!
Do you still have yours? If so I have mine at a friends and he has the abilty to repair it but I'd love to hear what you did and the results to sound.

 

[intoitreviews]

For a popular tube amp, the DarkVoice 336 is still one of my favorites under 1K. I've thought about upgrading to the 339, but honestly I don't have the space on my desk for it.

 

[Musiciseverything]

Hello hello! An old old thread I know, but I recently bought a p8, second hand, the one with the case, and doing the obligatory change of tubes to merely some GEjan, I’m really liking the sound already. It really is a lot of valve preamp for the money, especially at second hand prices.

I’m keen to unleash some more potential by upgrading a few parts, so I’m wondering if any of you who have enjoyed modding this thing, could share with me your experiences. I’ve read bits and peace’s on here, but I’m unsure which are really worth it. I might add that I’m autistic so I suppose I’m just looking for someone to give me a really clear idea of where to prioritise. What I should start with, and which yield the best results etc? Which specific brand of part did you use etc?

I’m okay with a solder iron, and as a musician, I hardly have a heavy touring itinerary at the moment! So plenty of time on my hands for this.


Thanks in advance, Dave