[StevieDvd]

Situation
 
Having recently decided to have a play with a cheapish tube amp and try a little tube rolling I bought a Bravo amp from Ebay. Now rather than spending a small fortune replacing components and trying out numerous tubes on this I decided to get a better budget tube amp as a base, the Little Dot MK III leapt to mind. Looking out for used ones in the for sale sections of a few forums and searching Ebay/Internet provided no contenders and I assumed it was an out of production model, at least by Little Dot. However there were some Hlly Mk III amps going cheap so I submitted an offer and had it accepted, the amp is now delivered and it works OK.
 
It now seems that it may be possible to get a Little Dot (MK III or VI) but I've got this Hlly one now so I'll play with that for a bit. If I can work out how to open the amp I may take some shots of the pcb & components if only to see which LD version it is closest to.
 
If all bodes well the rnext amp will not be a clonel!!!

Which tubes?
 
Power - 6N11, 6DJ8, 6922, E88CC, 7308 & apparently 6H30 will work
Driver - EF95, 5654, 6AK5, CV4010 & M8100 will work
The amp came fitted with Chinese 6N11 Power tubes and 5654 driver tubes. So I'm intended in try a few UK or Russian tubes to get a feel for the changes tube rolling can have.
Not knowing any UK shops or online stores I'm falling back on Ebay as a source (and checking the 'For sale' section here as well).

Is it better to go for matched pairs or just risk new or nos tubes?

How about these?
 
Driver Tubes
 
 
Mullard tubes from Taiwan
http://cgi.ebay.co.uk/2x-NOS-MULLARD-CV4010-VALVE-EF95-M8100-6AK5-5654-Tubes-/300432428611?cmd=ViewItem&pt=Vintage_Electronics_R2&hash=item45f32b0e43

Power Tubes
 
ZAERIX
http://cgi.ebay.co.uk/ECC88-6DJ8-ZAERIX-USSR-NEW-TUBE-VALVE-1-PC-/390186460467?cmd=ViewItem&pt=UK_Consumer_VintageAudio_RL&hash=item5ad8ece533
 
Russian  6N23P-EV
http://cgi.ebay.co.uk/Matched-pair-6N23P-EV-E88CC-6DJ8-Audiophile-tubes-NOS-/130392624788?cmd=ViewItem&pt=Vintage_Electronics_R2&hash=item1e5c018e94

 

[wwmhf]

I recently had a lot of fun in tweaking this amp.
 
Tube rolling helps a little. I found NOS GE FAA 5654W and Russian  6N23P (no EV) works well. The original driver tubes came with the amp were very bad, but the original power tubes 6N11 are OK, but not as clean as the Russian  6N23P I am using now.
 
After some tube rollings, it sounded a little better, but it was still very harsh. Then I opened the amp and found that the circuit of this amp is very close to Little Dot IV, but not exactly. However, I found that the parts used in this amp were really very bad. All the capacitors except for the electrolytic capacitors (which were some Rubycoms) at the output stage and power supply were total unacceptable! The volume pot was also a faked Alps. Most of the wires were generic ones. Resistors were also substandard. I did the following to upgrade the parts:
 
1. Replaced all the electrolytic capacitors except for those at the power supply. Most of the electrolytic capacitors were generic, it even did not use the same kind electrolytic capacitors at symmetrical locations.
2. Replaced all other capacitors. The amp used some film capacitors for input coupling, which was OK, but I replaced them some better polypropylene film capacitors. Most of the non-electrolytic capacitors in the amp were polyester type known for producing bad sound. Especially the amp used some polyester capacitors at the output stage which were the main course for the harsh sound. I replaced them all by polypropylene film capacitors. 
3. Replaced the faked Alps pot. In fact, I had to replace it because it failed while I was doing the modding. I never had any pot failed before, this was the fist one.
4. Replace some critical wires.
 
Now, the amp sounds very smooth and tubby. I can listen to it for hours and hours. It drives Senneheiser HD 650 and my little Koss 75 well, but of course it sounds better with HD 650.
 
I really went too far in this post, but I just would like to share my observation that tube rolling will impact less than modding for this amp.

 

[tamu]

Hey try watfordvalves. never got anything from them but they seem to have a good stock of different tubes
also try langrex on ebay. they have a very nice siemens e88cc. Nice tight bass and very warm highs. Im listening to my bijou with the siemens tubes and I love it

 

[StevieDvd]

 
Quote:

I recently had a lot of fun in tweaking this amp.
 
Tube rolling helps a little. I found NOS GE FAA 5654W and Russian  6N23P (no EV) works well. The original driver tubes came with the amp were very bad, but the original power tubes 6N11 are OK, but not as clean as the Russian  6N23P I am using now.
 
After some tube rollings, it sounded a little better, but it was still very harsh. Then I opened the amp and found that the circuit of this amp is very close to Little Dot IV, but not exactly. However, I found that the parts used in this amp were really very bad. All the capacitors except for the electrolytic capacitors (which were some Rubycoms) at the output stage and power supply were total unacceptable! The volume pot was also a faked Alps. Most of the wires were generic ones. Resistors were also substandard. I did the following to upgrade the parts:
 
1. Replaced all the electrolytic capacitors except for those at the power supply. Most of the electrolytic capacitors were generic, it even did not use the same kind electrolytic capacitors at symmetrical locations.
2. Replaced all other capacitors. The amp used some film capacitors for input coupling, which was OK, but I replaced them some better polypropylene film capacitors. Most of the non-electrolytic capacitors in the amp were polyester type known for producing bad sound. Especially the amp used some polyester capacitors at the output stage which were the main course for the harsh sound. I replaced them all by polypropylene film capacitors. 
3. Replaced the faked Alps pot. In fact, I had to replace it because it failed while I was doing the modding. I never had any pot failed before, this was the fist one.
4. Replace some critical wires.
 
Now, the amp sounds very smooth and tubby. I can listen to it for hours and hours. It drives Senneheiser HD 650 and my little Koss 75 well, but of course it sounds better with HD 650.
 

 
I'd gathered it was not quite the MkIII, based on the resistors around the gain switches (a lot like the MK IV) - have not figured out how to open the case yet, being a little wary of breaking/dislodging something in the process. I'll try rolling a few tubes at first and may consider replacing components if I stick with the amp, I damaged a finger in an accident so not very dextrous at present. Will balance the cost & effort of changing parts over buying a legit LD or other branded name later. It's only a secondary rig so it won't be a big budget affair.  At least it was cheap.

 
 




 
Quote:

Hey try watfordvalves. never got anything from them but they seem to have a good stock of different tubes
also try langrex on ebay. they have a very nice siemens e88cc. Nice tight bass and very warm highs. Im listening to my bijou with the siemens tubes and I love it

Thanks for that will check out Langrex further the Siemens and a set of matched Mullards for drivers they are doing should be a good start point. Watford look a bit pricey considering the amp the tubes are destined for. I've ordered a pair of Mullard cv4010 from Taiwan as they were cheap - but will they be real Mullards, will have to see how they sound.

 
 

 

 

[technocrat]

I would love to see pics of the internals modified. Im sure im not the only one

 

[reiserFS]

Now that is certainly interesting, I second some pictures of the internals if you manage to get the case open.

 

[wwmhf]

I will get some picture uploaded later.

 

[wwmhf]

The amp after mods:
 

 

[wwmhf]

The tubes I am using now:
 

 
The old and new wire connected to the headphone jack:
 


 
Some bypass caps added and new input and output wires:
 

 

[wwmhf]

Most of the caps were replaced by better ones, the pot was also replaced by a real Alps. The original pot was zapped during the modding.
 

 
Some of the original caps in the signal pass, and I threw away all the original small electrolytic caps:
 

 
The headphone jack was replaced by a better one. The original one went bad and actually damaged the headphone plug!
 

 

[wwmhf]

Looking for better cap configurations:
 

 

[wwmhf]

Now you have some pictures! Have fun with this amp. But be careful due to the high voltage!
 

 

[tamu]

wow. thats alot of caps!
 
why dont you post it in the "post your modding" thread in diy forums?

 

[wwmhf]

"why dont you post it in the "post your modding" thread in diy forums?"
 
I am sorry if I have sidetracked this thread. 

 

[technocrat]

Wow thanks for all the pics. You really seem to know your way around an amp. I really appreciate the effort you took to post these.